IGC 13 82

IGCIGCIndustrialGasesCommittee

IGC 13/82The Transportation and Distribution of Oxygen by Pipeline

Part 1 : Introduction and General

1982 Reproduced in IMSS with permission Page 1 of 39

The Transportation and Distribution of Oxygen by PipelinePart 1 : Introduction and General

IGC 13/82/E

Recommendations for the Design, Construction, Operation and Maintenance

32, Bd de la Chapelle

75880 PARIS CEDEX 18

The information furnished by the Association was gathered with the greatest care, and the knowledgeavailable on the date of issue. It does not include any warranties of the Association, whoseresponsibility does not substitute the responsibility of the user.

Prepared by Working Group WG "C"

L. Bothoel A.L.W. Busch LindeA. de Lorenzo A.L.K.R. Mathison AGAG.W. Randle BOCD.H. Rowe A.P.E. Wolfe LindeH. Zcepuck M.G.M. Jamault TS-IGC





INTRODUCTION....................................................................................................................................................................5

SECTION 1: GENERAL.......................................................................................................................................................6

1.1 DEFINITIONS..........................................................................................................................................................61.1.1 General..................................................................................................................................................................61.1.2 Scope......................................................................................................................................................................61.1.3 Pressure.................................................................................................................................................................6

1.1.3.1 Pressure range ................................................................................................................................................61.1.3.2 Nominal pressure ...........................................................................................................................................91.1.3.3 Design pressure ..............................................................................................................................................91.1.3.4 Strength test pressure .....................................................................................................................................91.1.3.5 Leak test pressure...........................................................................................................................................91.1.3.6 Maximum allowable operating pressure ........................................................................................................91.1.3.7 Working pressure ...........................................................................................................................................91.1.3.8 Delivery pressure ...........................................................................................................................................91.1.3.9 Design pressure - customer’s network...........................................................................................................91.1.3.10 Set or lifting pressure - safety valves .............................................................................................................91.1.3.11 Relieving pressure - safety valves ..................................................................................................................91.1.3.12 Bursting pressure ............................................................................................................................................9

1.1.4 Temperature....................................................................................................................................................... 101.1.4.1 Design temperature ......................................................................................................................................101.1.4.2 Working temperature ...................................................................................................................................101.1.4.3 Process temperature .....................................................................................................................................101.1.4.4 Ambient temperature ....................................................................................................................................10

1.1.5 Corrosion........................................................................................................................................................... 101.2 OXYGEN CHARACTERISTICS..................................................................................................................................10

1.2.1 Physical Data.................................................................................................................................................... 101.2.1.1 Physical characteristics ................................................................................................................................101.2.1.2 Oxygen content in the atmosphere...............................................................................................................11

1.2.2 Properties........................................................................................................................................................... 111.2.2.1 Combustion ..................................................................................................................................................111.2.2.2 Biological effect ...........................................................................................................................................111.2.2.3 Density in relation to air...............................................................................................................................111.2.2.4 Miscellaneous properties .............................................................................................................................111.2.2.5 Properties of liquid oxygen ..........................................................................................................................11

1.2.3 Industrial Oxygen............................................................................................................................................. 111.3 FLAMMABILITY - CONDITIONS..............................................................................................................................11

1.3.1 Flammability of Materials and Products in Oxygen .................................................................................. 121.3.1.1 General.........................................................................................................................................................121.3.1.2 Compatibility tests .......................................................................................................................................121.3.1.3 Ignition temperature .....................................................................................................................................121.3.1.4 Cleanliness ...................................................................................................................................................131.3.1.5 Velocity ........................................................................................................................................................131.3.1.6 Influencing factors .......................................................................................................................................13

1.3.1.6.1 Pressure..................................................................................................................................................131.3.1.6.2 Temperature...........................................................................................................................................141.3.1.6.3 Simultaneous effect: velocity, pressure, temperature.....................................................................141.3.1.6.4 Humidity................................................................................................................................................151.3.1.6.5 Concentration........................................................................................................................................151.3.1.6.6 Surface to volume ratio of materials .................................................................................................151.3.1.6.7 Other parameters ..................................................................................................................................16

1.3.1.7 General Combustion Process .......................................................................................................................161.3.2 Ignition in an Oxygen-Enriched Atmosphere .............................................................................................. 19

1.3.2.1 General.........................................................................................................................................................191.3.2.2 Influencing Factors ......................................................................................................................................19

1.3.2.2.1 Oxygen concentration .........................................................................................................................191.3.2.2.2 Pressure..................................................................................................................................................191.3.2.2.3 Fabrics - materials and treatment.......................................................................................................191.3.2.2.4 Cleanliness ............................................................................................................................................20

1.3.2.3 Safety limits of oxygen concentrations........................................................................................................20





1.3.3 Combustion and Explosion of Gases and Vapours..................................................................................... 201.3.3.1 General.........................................................................................................................................................201.3.3.2 Conditions for Ignition.................................................................................................................................211.3.3.3 Definitions and Characteristics ....................................................................................................................21

1.3.3.3.1 Limit of flammability ..........................................................................................................................211.3.3.3.2 Minimum ignition energy...................................................................................................................221.3.3.3.3 Ignition temperature.............................................................................................................................221.3.3.3.4 Combustion rate ...................................................................................................................................221.3.3.3.5 Pressure developed ..............................................................................................................................23

1.3.3.4 Influencing Factors ......................................................................................................................................231.3.3.4.1 Effects of pressure ...............................................................................................................................231.3.3.4.2 Effect of temperature ...........................................................................................................................241.3.3.4.3 Effect of an inert gas............................................................................................................................241.3.3.4.4 Other effects..........................................................................................................................................25

1.3.3.5 Self-Ignition .................................................................................................................................................251.3.4 Physiological Risks .......................................................................................................................................... 26

1.3.4.1 Nature of risks ..............................................................................................................................................261.3.4.2 Effect of oxygen enrichment........................................................................................................................261.3.4.3 Physiological effects of oxygen deficiency .................................................................................................261.3.4.4 Thresholds....................................................................................................................................................27

1.4 CAUSES OF ACCIDENTS..........................................................................................................................................281.4.0 General............................................................................................................................................................... 281.4.1 Internal Spontaneous Ignition........................................................................................................................ 281.4.2 Causes of Internal Ignition ............................................................................................................................. 28

1.4.2.1 Physical/mechanical phenomena .................................................................................................................281.4.2.1.1 Friction of particles or foreign bodies ..............................................................................................281.4.2.1.2 Impact and incrustation of particles ..................................................................................................291.4.2.1.3 Abnormal or accidental friction within components .....................................................................291.4.2.1.4 Vibration................................................................................................................................................291.4.2.1.5 Fractures ................................................................................................................................................291.4.2.1.6 Adiabatic compression........................................................................................................................291.4.2.1.7 Thermodynamic phenomena ..............................................................................................................29

1.4.2.2 Chemical Phenomena...................................................................................................................................301.4.2.2.1 Exothermic phenomena.......................................................................................................................30

1.4.2.3 Electrical Phenomena...................................................................................................................................301.4.2.3.1 Heating due to electric currents .........................................................................................................301.4.2.3.2 Electrostatic charges............................................................................................................................301.4.2.3.3 Dust concentration...............................................................................................................................301.4.2.3.4 Electrolytic phenomena.......................................................................................................................30

1.4.3 Factors Influencing Ignition........................................................................................................................... 301.4.3.1 Lack of cleanliness.......................................................................................................................................301.4.3.2 Abnormally high velocity ............................................................................................................................301.4.3.3 Incompatible or unsuitable materials ...........................................................................................................301.4.3.4 Temporary connections to other networks ...................................................................................................311.4.3.5 Mechanical accidents on installations..........................................................................................................311.4.3.6 Poor workmanship & maintenance ..............................................................................................................311.4.3.7 Unauthorised action .....................................................................................................................................31

1.4.4 External Causes of Accidents ......................................................................................................................... 311.4.4.1 Mechanical damage......................................................................................................................................311.4.4.2 Thermal Effects ............................................................................................................................................321.4.4.3 Corrosion......................................................................................................................................................321.4.4.4 Proximity of high tension electric cables .....................................................................................................321.4.4.5 Natural Causes .............................................................................................................................................33

1.4.5 Internal Explosions in Pipelines .................................................................................................................... 331.4.6 Oxygen - Enriched Atmosphere...................................................................................................................... 331.4.7 Explosive Atmospheres.................................................................................................................................... 341.4.8 Oxygen Deficient Atmosphere ........................................................................................................................ 341.4.9 Normal Electrical Dangers............................................................................................................................. 341.4.10 Points Where Accidents May Occur........................................................................................................... 341.4.11 Circumstances of Accidents......................................................................................................................... 341.4.12 Synoptic Table................................................................................................................................................ 35





1.5 REGULATIONS.....................................................................................................................................................361.5.1 Official Regulations and Recommendations................................................................................................ 361.5.2 Scope of Official Regulations......................................................................................................................... 361.5.3 Environmental Problems................................................................................................................................. 371.5.4 Dominance of Local Law................................................................................................................................. 37

1.6 GUIDANCE FOR THE PREVENTION OF, PROTECTION AGAINST , AND MEANS OF COMBATING ACCIDENTS371.6.0 General............................................................................................................................................................... 371.6.1 Prevention.......................................................................................................................................................... 37

1.6.1.1 For the whole ...............................................................................................................................................371.6.1.2 For the equipment ........................................................................................................................................371.6.1.3 For materials ................................................................................................................................................371.6.1.4 For the installations......................................................................................................................................371.6.1.5 For work on the installations........................................................................................................................381.6.1.6 Protection gainst third parties ......................................................................................................................38

1.6.2 Protection of Persons....................................................................................................................................... 381.6.3 Combating Accidents ....................................................................................................................................... 38

1.7 INSPECTION OF EQUIPMENT AND INSTALLATIONS.............................................................................................391.7.1 The Need for Inspection................................................................................................................................... 391.7.2 Inspection........................................................................................................................................................... 39

1.7.2.1 Scope ............................................................................................................................................................391.7.2.2 Application...................................................................................................................................................39

1.7.3 Training of Personnel ...................................................................................................................................... 39





INTRODUCTIONFor several years, transport and distribution of products by pipeline have developed world-wide,mainly for gaseous fuels and petroleum products. Now this system of distributions is used extensivelyfor oxygen, especially in areas where industry is heavily concentrated. From production centres,oxygen is piped to steel mills, chemical and petrochemical plant as well as to other industrialfacilities.

Oxygen is not a fuel but a supporter of combustion. In oxygen or even in air which is only slightlyoxygen enriched, fuels ignite more easily and burn more readily.

The Companies who belong to the Industrial Gas Committee have prepared this document with a viewto preventing incidents during operation of oxygen piping systems caused in particular by thephenomena known as ‘self-ignition’ and to limit the impact of possible consequences.

The recommendations formulated in this document are the result of many years experience in thedesign, installation and operation of oxygen pipelines. Application of these recommendations willensure a high level of safety.

The recommendations apply to normal operating conditions and would have to be adapted or modifiedif conditions deviate from normal.

The document is not a manual for pipeline designers nor will it relieve manufacturers from the need toexercise sound engineering judgement in selecting materials or making decisions.

The document should not be considered as an account of research work or as scientific report.Explanatory notes and comments which usually accompany the latter will only be found in thisdocument to a limited extent.

The recommendations reflect what is currently considered as the state of the art of gas pipeline design,construction and operation and the document is only a reminder of the essential aspects.

The recommendations are only to be used as a compliment to National rules and regulations whichremain predominant.

Design may be improved with technological advances. The Industrial Gas Committee feel that it hasa duty to publish such developments and will be quite prepared to examine and consider relevantremarks or suggestions which may be submitted.

TERMS OF REFERENCE

The recommendation of the Code concerns the design, construction, operation andmaintenance of oxygen transportation and distribution pipeline installations,excluding production plant pipework and consumer points of use.

Scope

Pressure 0 to 70 bar gauge

Temperature -30°C to +80°C

Purity Higher than 90% oxygen





SECTION 1: GENERAL

1.1 DEFINITIONS1.1.1 General

In diagrams Figure 1 and Figure 2 are shown the parts which make up a pipeline network and theirprincipal definitions.

The document deals with distribution networks from the supply stations of oxygen plants to thedistribution stations at customers’ works. (Points ‘A’ to ‘B’, Fig. I).

It does not deal with the other parts of a complete network.

• oxygen plants

• distribution piping in the workshops

• points of use

1.1.2 ScopeThis documents deals with the distribution of oxygen with purity in excess of 90%, at a pressurehigher than 1 bar and having a dew point lower than -30°C at the maximum operating pressure attemperatures between -30°C and +80°C.

1.1.3 Pressure

1.1.3.1 Pressure rangeGaseous oxygen is transported under pressure. The pressure provides the energy for transportation.In the case of oxygen pipelines 3 pressure ranges may be distinguished (pressure unit: bar gauge):

• 0-25 bar : generally used for distribution in workshops. (see I.C.C. Code)

• 1-70 bar : DELIVERY NETWORKS(Tolerance +10%) the subject of the present document.

• above 70 bar : special constructions outside traditional standards, not covered by this code.













1.1.3.2 Nominal pressureThe nominal pressure defines the maximum allowable pressure for a given basic temperature: atwhich a fitting or system may be operated according to a given code.

1.1.3.3 Design pressureThe design pressure is the maximum pressure for which the fitting or system has been calculated. Forcalculations additional parameters such as temperature, corrosion, cycling pressures, etc., shall takeninto account as well as the maximum stresses permitted both at operational level and for testing.

1.1.3.4 Strength test pressureThe strength test pressure is the pressure to which the fittings or systems are subjected at the time ofmanufacture or before going into service. The test is generally of a statutory nature and the testpressure is defined on the basis of the design pressure increased in a defined manner by the code orofficial regulation applied.

1.1.3.5 Leak test pressureThe leak test pressure is the pressure to which a fitting or system is subjected when a leak test is madeseparately from the strength test. The value for it is defined by the constructor’s own rules or by thecode or regulation applied.

1.1.3.6 Maximum allowable operating pressureThe maximum allowable operating pressure is the maximum pressure that a fitting or system is able tosustain at a given temperature in order to meet the requirements of a given code.

It shall not exceed the design pressure.

This pressure and the test reference should be written on components after testing and checking withcalculation notes.

1.1.3.7 Working pressureThe working pressure is the pressure under which the installations function.

1.1.3.8 Delivery pressureThe delivery pressure is the pressure at which the product is delivered to the customer.

1.1.3.9 Design pressure - customer’s networkThe pressure used for the design of the distribution network in customer's works

1.1.3.10 Set or lifting pressure - safety valvesThe set pressure of a valve is the pressure at which the valve begins to open, this pressure shall not begreater than the design pressure of the installation.

1.1.3.11 Relieving pressure - safety valvesThe relieving pressure of a valve is the pressure at which the valve passes its rated flow. Normallythis will be within 10% of set or lifting pressure.

1.1.3.12 Bursting pressureThe bursting pressure of a safety bursting disc is defined as function of the design pressure of theinstallation. See 4.2.5.4.2.

Certain codes and regulations accept destructive testing of a component as an alternative to a designcalculation. The working pressure will then be the bursting pressure multiplied by a safety factor asdefined by the code or regulation. This method may be used for mass produced components.





1.1.4 Temperature

1.1.4.1 Design temperatureThe design temperature is the temperature used in the selection of the materials and the dimensioningof the installation components considered in accordance with the code applied.

In the installations concerned two design temperatures may be distinguished.

• The highest design temperature. This is taken into account in determining the thickness of theelement considered.

• The lowest design temperature which determines the selection of the materials used.

The unit is the degree CELSIUS.

1.1.4.2 Working temperatureThe working temperature is the temperature taken into consideration in the specification of astandardised element (see 1.1.3.2.).

1.1.4.3 Process temperatureThe process temperature is the design temperature for the normal operation of the installation.

With regard to transportation networks, in practice the temperature remains within limits which haveno effect on the dimensional specification of the components. When necessary a distinction is madebetween:

• normal operating temperature

• minimum operating temperature

• maximum operating temperature

• minimum allowable temperature

• maximum allowable temperature

1.1.4.4 Ambient temperatureThe ambient temperature is the outside temperature, variable at a given point as a function of theprevailing climatic conditions, the reason, the time of day or night.

It may occur at two extremes:

• Low temperature: specification of materials as a function of brittleness:

• High temperature: the effect of a rise in temperature on the pressure of a gas in an enclosed space.

1.1.5 CorrosionDry oxygen with Characteristics defined in 1.1.2 is not corrosive.

The protection of the pipeline from external corrosive agents shall be ensured.

1.2 Oxygen Characteristics1.2.1 Physical Data

1.2.1.1 Physical characteristicsChemical formula O2

Molecular weight 32

Specific mass of the gas at 0°C and 1.013 bar 1.4290 kg/m3

Boiling point at 1.013 bar -183°C

Specific mass of the liquid at 1.013 bar and -183°C 1.141 kg/1





1.2.1.2 Oxygen content in the atmosphereOxygen is the second component by quantity in the air of the atmosphere:

Oxygen 21% by volume in the air

Nitrogen 78% by volume in the air

Argon 0.9% by volume in the air

1.2.2 Properties

1.2.2.1 CombustionOxygen is an oxidising gas which under certain conditions combines with almost all the elementsgiving rise to a brisk exothermic reaction.

Compared with air, pure oxygen or oxygen enriched air favours and activates combustion, especiallythat of organic materials. This phenomenon is aggravated by the effects due to the pressure of the gas(higher partial pressure) or due to higher velocity (blowing effect).

1.2.2.2 Biological effectOxygen is necessary for life.

Air which is deficient in oxygen causes physiological difficulties and even asphyxia.

1.2.2.3 Density in relation to airBeing slightly heavier than air (density 1.05) oxygen has a tendency, especially when cold, toaccumulate at low points.

1.2.2.4 Miscellaneous propertiesGaseous oxygen is odourless, colourless and tasteless. It is not toxic.

In the absence of moisture it is not corrosive.

1.2.2.5 Properties of liquid oxygenBy reason of its temperature liquid oxygen can make certain materials brittle. It can cause seriousburns on contact with the skin.

1.2.3 Industrial OxygenIndustrial oxygen is mainly produced from the air, from which it is extracted by distillation at lowtemperature (see also 1.1.2).

IMPORTANT NOTE

Nitrogen is also an odourless, colourless, tasteless gas. The detection of anyanomoly by the senses is therefore inoperative, whether it is a matter of pure

oxygen, enriched air, air deficient in oxygen, or pure nitrogen.

1.3 Flammability - ConditionsIn this section the characteristics of the flammability of materials or products in oxygen or oxygen-enriched atmospheres are examined. Also the physiological aspects of atmospheres enriched ordeficient in oxygen.

Distinction is made between :

• the flammability of materials or products in oxygen leading to spontaneous ignition (1.3.1)

• flammability in oxygen-enriched atmospheres (1.3.2)

• the flammability and explosivity of gas or vapour in an atmosphere of oxygen, of air, or ofoxygen-enriched air (1.3.3)

• the physiological consequences of an atmosphere enriched or deficient in oxygen (1.3.4)





1.3.1 Flammability of Materials and Products in Oxygen

1.3.1.1 GeneralCombustible materials, and indeed materials reputed to be non-combustible in air, may ignite morereadily in oxygen.

Compared with air, other considerations shall be taken into account:

• Ignition temperature is lower

• Energy required for ignition is much lower

• Combustion temperature is higher

• Combustion rate is greater

This combination of properties makes ignition easier to initiate and develop.

Combustion generally progresses in the direction of the gas flow.

1.3.1.2 Compatibility testsThere are a large number of tests which make it possible to select materials for use in oxygen.

It is very difficult to reproduce tests which simulate the many parameters involved at the same time,and is practically impossible to reproduce actual accident conditions met with during operations.

Of the tests that are best known, mention is made of the following:

• Determination of ignition temperature

• Adiabatic compression tests

• Determination of the oxygen index (concentration of oxygen required to maintain combustion ofa material)

• Determination of the combustion rate

• Determination of acceptable velocities (ignition by friction and percussion of particles)

• Simulation tests

The results of these tests make it possible to classify materials within the framework of the testconditions.

These results shall therefore be the subject of interpretation by specialists in order to determine theirapplication.

The ignition temperature is not the only factor to be taken into consideration. Certain other factors arecapable of influencing the effect of the Ignition Temperature and are capable of accelerating orretarding ignition, especially those which have the effect of increasing or decreasing the heat inputnecessary to reach the ignition temperature.

These various factors and parameters will now be analysed.

1.3.1.3 Ignition temperatureThe ignition temperature is most commonly determined by a specimen test of product whosetemperature gradually rises in an enclosure under constant oxygen pressure until ignition occurs. Thisis known as the bomb test.

In Chapter 2.0 will be found ignition temperature figures for various materials and products.

The sample figures below emphasise the drop in ignition temperature in oxygen as compared with air,at atmospheric pressure.

In oxygen

°C

In air

°C

Mild steel 1097 to 1250 1227 to 1277

Perspex 430 595

Cotton 360 465

Wool 500 > 600





1.3.1.4 CleanlinessAs repeated numerous times, the cleanliness of the gas pipeline is an important safety factor.

The gas is manufactured clean, however dust may be carried from the installations. The causes ofaccidents are dealt with in 1.4 and the problems of cleanliness are dealt with in 2.3.

1.3.1.5 VelocityThe velocity of the gas acts as the motive element for particles, which may in certain cases as a resultof friction and percussion attain temperatures of a kind to initiate ignition.

The velocity in certain countries has for many years been limited to 8 m/s, whatever the conditions ofuse.

In the meantime tests and operational results have shown that this arbitrarily chosen velocity has beensafely exceeded.

Tests have shown that in steel pipelines the friction of particles in the networks cannot cause ignitionunless the oxygen attains a velocity in excess of 60 m/s, and then only after or during changes indirection of flow.

It will therefore be possible in most cases to allow velocities higher than 8 m/s in correctly constructedsteel pipelines. The same applies to installations maintained in a clean condition.

It should however be emphasised particularly for long lengths of pipeline, that the level of pressuredrop to be complied with generally has the effect of limiting the velocity to a safe value.Recommended maximum velocities are indicated in 4.1.2.

1.3.1.6 Influencing factors

1.3.1.6.1 PressureAn increase in pressure results in :

• lowering of the ignition temperature

• increasing the combustion rate

Within the limits set for this Code, however, any increase of pressure beyond 30 bar has little effecton the ignition temperature and combustion rate.

The curves in Figure 3 show the temperature at which ignition takes place and of the combustion rateas a function of pressure.





Figure 3 : Ignition temperatures and combustion rates as a function of pressure

Increase in pressure also has the effect of increasing the dynamic pressure and the density andtherefore the capacity for entraining particles, for same gas velocity.

The effect of a rupture may increase with an increase in pressure and pipe diameter.

1.3.1.6.2 TemperatureHigh temperature of the oxygen, and at the same time that of the pipelines and components favoursignition.

The main factors that favour ignition following an increase in temperature are:

• The energy required to reach the ignition point is less

• The combustion rate is higher

• Less heat removed by the gas flow

• Particles subjected to friction reach their ignition point more easily

Similarly in the case of adiabatic compression the compression ratio necessary in order to obtain agiven temperature will be less as the initial temperature is higher. Starting from 1 bar(a) thecompression ratio required in order to pass from 15 to 400°C is 20, but is only 7 in order to pass from130 to 400°C.

1.3.1.6.3 Simultaneous effect: velocity, pressure, temperatureThe tendency towards ignition by entrained particles increases with :

• increase in oxygen velocity

• increase in oxygen pressure

• rise in oxygen temperature

The graph fig.4 shows qualitivly through the results of a test the interrelationship of pressure andtemp. on the velocity to cause ignition.





Figure 4 : Ignition as a function of velocity, pressure and temperature

1.3.1.6.4 HumidityIt is probable that ignition is favoured in the presence of dry gas, although this is difficult to assess.

On the other hand humidity may cause corrosion with the disadvantage of component damage,entrained particles etc.

It is possible that in certain cases humidity may influence the accumulation of electrostatic charges.

Phenomena in this field is still insufficiently known and generally speaking we have only hypotheseswhich have not been investigated.

Industrial oxygen is today a dry product and therefore we need not under normal conditions ofworking fear any effects due to the humidity content.

1.3.1.6.5 ConcentrationThis Code deals with the distribution of oxygen on a concentration equal to or greater than 90%.

The effect of oxygen enrichment is dealt with in 1.3.2.

1.3.1.6.6 Surface to volume ratio of materialsEase of ignition of a material depends upon the area in contact with oxygen. For example a cube of1 cm in size presents an area of 6 cm2, while the same cube divided into cubes of 0.1 cm has a surfacearea of 600 cm2.

It may be said that the more finely divided a material is, or the more it lacks compactness :

• the smaller the beat addition necessary to initiate combustion because of the smaller heatabsorbtion and lower dispersion ability.

• the faster will be the reaction combustion rate, because of the greater surface area of attack for agiven mass. This is emphasised by the curves in Figure 3, the rate being higher for the 1 mmdiameter wire than for the 2 mm.

These considerations will require limitations in the use of liquids, pastes, powders, fabric and materialof small mass.





1.3.1.6.7 Other parametersMany other parameters also enter into consideration in defining the liability to ignite.

(a) Physical and Chemical characteristics of the material

• Metal hardness, impact behaviour, ability to produce sparks.

• Thermal conductivityGood conductivity favours the dispersion of heat while poor conductivity favours theconcentration and rise of temperature.

• Specific heatHigh specific heat retards the rise of temperature

• Heat of combustion or of reactionA high value increases the amount of heat available

• Presence of a film of oxide.

Oxides retard ignition. This may be the case for metals either in the solid or liquid state to thepoint of preventing the propagation of ignition in a stable environment.

Transformation by ageingCertain materials such as polyurethane burn much more easily after ageing.

Retarding or accelerating effect of materials.

(b) Design of parts

• ConfigurationSharp edges favour initiation of ignition

• Mass or thickness of partsCapacity for absorbing heat

(c) Loose Parts

A loose part is more liable to store heat, especially if it is small and a poor conductor, hencethe necessity for plastic parts to be in intimate contact with the metallic materials.

1.3.1.7 General Combustion ProcessSpontaneous ignition is generally speaking a phenomenon. The development of which is not alwayseasy to explain.

Ignition generally begins in materials which ignite easily. These may be materials forming part ofcomponents, or deposits of foreign matters.

There may also be a latent source of ignition in a very low flow of oxygen or in stationary oxygen,this may develop suddenly when significant flow is established. Ignition is propagated from materialto material according to the characteristics of the system.

On the other hand as combustion depends on heating and maintaining the components at the reactiontemperature, a very large flow of oxygen at high velocity may disperse the combustion products andcool the reaction zone sufficiently to stop combustion.

One thing is certain : When combustion spreads externally everything then happens very quickly andmay result in damage.

According to circumstances the effects upon the component which initiated ignition may :

(a) be limited to internal combustion without perforation. In this case damage is slight and limitedto the component concerned without consequence for the environment.

(b) cause perforation of small dimensions with a jet of oxygen and of an incandescent material. Inthis case, too, the damage is generally small and limited in the path of any projections.





(c) cause extensive combustion of the installation or the component (generally downstream),causing :

• large scale projections of :

• incandescent or molten particles

• incandescent large pieces

• large pieces of broken metal

• oxygen enrichment of the area

(d) resultant bursting caused by deterioration of the mechanical properties due to reduction ofthickness, or heating, when the enclosing walls can no longer resist the pressure of the gas.

Bursting may be caused by :

(a) Reduction of wall thickness :

• metal partly burnt away

• erosion

(b) Heating :

• by internal combustion of elements

• by combustion of the metal itself

• by the flow of molten oxides and metal along the bottom of a pipe.

In cases (c) & (d) and sometimes case (b) the consequences may be aggravated by the effect of the jetaction of the escaping gas. This may lead to the violet displacement of pipes which may causedamage to the surroundings.

In conclusion we may recall that in order for igntion to develop into an accident there shall be 4conditions.

• the presence of oxygen

• the source of ignition

• a material which is combustible under the effect of the ignition source

• conditions favourable for the development of combustion

Ignition and combustion conditions are shown in Table I. This table also applies for 1.3.2 and 1.3.3.





Table 1 : Oxygen Installations – conditions for ignition and its effects





1.3.2 Ignition in an Oxygen-Enriched Atmosphere

1.3.2.1 GeneralThe behaviour of materials flammable in air containing 21% oxygen changes as soon as theproportion of oxygen exceeds this concentration. Any excess of oxygen in the air has a considerableeffect on combustion.

The curves in Figure 5 illustrate the effects of enrichment on materials currently used in themanufacture of clothing.

Figure 5 : Ignition temperatures and combustion rates as a function of oxygen concentration

It is possible to classify materials according to an oxygen index, which is the percentage oxygenbelow which combustion cannot be maintained under clearly defined test conditions.

The enrichment of air with oxygen makes combustion more likely, brighter, hotter and more rapid.

We shall briefly analyse the effect of the various parameters, relative to the protection of persons.

1.3.2.2 Influencing Factors

1.3.2.2.1 Oxygen concentrationFabrics which on receiving a certain amount of ignition energy (a spark) do not ignite in air mayignite very rapidly when the oxygen concentration is increased.

The increase in oxygen concentration accelerates combustion (see Figure 5) for the following reason :

• Energy required for ignition is much lower

• increase in the temperature of combustion

• rapid increase of the combustion rate

See 1.3.2.3 for safety limits.

1.3.2.2.2 PressureAccidents that occur in the atmosphere as a result of enrichment are not affected by pressure.However, the danger increases rapidly with pressure.

1.3.2.2.3 Fabrics - materials and treatmentSome fabrics are more flammable than others. Wool has a greater resistance to fire than cotton orlinen.

Closely woven fabrics are generally more resistant to fire.

Some synthetic materials offer a certain resistance to fire but may cause serious burns by melting andclinging to the skin, therefore are not recommended.

Fabrics impregnated with fire-resistant products reputed to be difficult to burn in air burn more readilyin higher oxygen concentrations. It should also be noted that washing reduces the efficiency ofimpregnation.





1.3.2.2.4 CleanlinessA garment stained or impregnated with oil, grease or hydrocarbons ignites more easily and burnsmore rapidly.

1.3.2.3 Safety limits of oxygen concentrationsIt is difficult to establish a rigid threshold. It may however be considered that the danger is great asfrom 25%.

Various factors may however influence ignition, as we have seen in 1.3.2.2.

In addition, the degree of oxygen enrichment may :

• be variable from one point to another

• increase progressively or suddenly

• vary as a function of gaseous mass displacement

For these reasons, working in an oxygen-enriched atmosphere is prohibited, and warning shall begiven as soon as the oxygen concentration exceeds 22%. (see 6.1.2.1).

The general problem of prevention will be dealt with in 1.6 of the Code which deals with work onpipeline networks.

Protection and action to be taken are dealt with in section 7 of the Code.

1.3.3 Combustion and Explosion of Gases and VapoursThis section is concerned with the dangers of explosive mixtures.

The installations covered by this Code are not designed to carry such mixtures normally. Thesemixtures can only be introduced accidentally.

It should be noted that normal pressure release devices are not sufficient to limit the effect ofexplosions.

It nevertheless seems advisable to explain the nature of the dangers to impress upon personnel thenecessity for preventing the formation of such mixtures within systems as well as areas of installationor maintenance work.

1.3.3.1 GeneralFlammable gases are capable of reacting violently with oxygen, whether with oxygen or oxygen-enriched air or air. The oxygen acts as a supporter of combustion. Ignition starts the reaction andcombustion is the development that follows.

The combustible nature of these gases can create dangers of fire or explosion in the event of mixingwith oxygen or air. An explosion may result in considerable damage in the event of bursting of theenclosure in which ignition occurs. Explosion may also occur in the atmosphere.

The existence of a dangerous mixture of combustible gases or vapours is always accidental and mayarise for example :

• from a back flow of gas from a point of use

• from an incorrect connection

• from residues of cleaning products incompletely rinsed out

• release of other gases

• from leaks in hoses or equipment, e.g. welding cutting and heating equipment

Ignition of a combustible mixture may be caused by :

• a brief pin-point source, within the mixture, e.g. electric spark, incandescent particle, impact

• heating through accidental contact with a heat source or element. (Pipe or component wall,internal parts)

• spontaneous ignition as described in 1.3.3.5





1.3.3.2 Conditions for IgnitionThe following are necessary for ignition to take place :

In all cases :

(a) The composition of the mixture shall lie within the lower and upper limits of flammability.

A mixture can ignite and its ignition can be propagated if the mixture contains a sufficientproportion of combustible gas and a sufficient proportion of air/oxygen.

In addition:

(b) In the case of a pin-point source, it is necessary for the energy introduced by the source to beadequate.

(c) In the case of heating by contact or of spontaneous ignition, it is necessary for the ignitiontemperature to be reached in the mixture.

1.3.3.3 Definitions and Characteristics

1.3.3.3.1 Limit of flammabilityThe lower limit of flammability is the lowest concentration of combustible gas at which ignition ispossible.

The upper limit of flammability, is the highest concentration of combustible gas, above which ignitionis not possible because the mixture is too deficient in air or oxygen.

NB A mixture containing a proportion of combustible gas which exceeds the upper limit offlammability in air cannot propagate the flame within itself but it can burn in contact with theoutside air with a diffusion flame.

It is usual to express these limits as percentages by volume of the combustible gas and unlessotherwise stated they refer to standard conditions of temperature and pressure.

The limits are given for some common products in Table II for the two cases of mixture with oxygenand mixture with air.

It should also be noted that most of the vapours emitted by the solvents are heavier than air and thatthere may be at their tendency for concentrations at low points.

Table II:- Limits of flammability at 20°C and 1013 mB

Flammability Limitsin Vol %

in Air In O2

Product Formula SelfIgnitionTemp °C

in Airlower upper lower upper

Acetylene C2 H2 299 2.5 81 2.8 93Butane C4 H10 405 1.9 8.5 1.85 49

Carbon monoxide CO 609 12.5 74 15.5 93.9

Ethylene C2 H4 450 3.1 32 2.9 79Hydrogen H2 585 4 75 4.65 93.9

Methane CH4 537 4.5 15 5.0 60.5

Propane C3 H8 466 2.2 10 2.25 52Trichloroethylene C2 H Cl3 8 12 7.0 64.5

Trichloroethane C2 H3 Cl3Trifluorotrichloroethane C2 F3 Cl3 Non-FlammableTrichlomonofluromethane (Fll) CF Cl3 Non-Flammable

Methyl ether (CH3)2 0 350 3.4 18 3.9 61

Petroleum ether C5 H12 246 1 6.5Light petrol 230 1 6.5

Methyl alcohol C H4 O 464 7.3 36 7 82

Monoethyleneglycol (clycol) C2 H6 O2 412 3.2





1.3.3.3.2 Minimum ignition energyThe minimum ignition energy is the minimum energy required to ignite a mixture. In some cases itmay be very small, of the order of 0.02 millijoule in air for most flammable gases.

It should be also noted that gases or vapours non-flammable in air, can burn with pure oxygen orenriched air but may react with oxygen or oxygen enriched air.

Minimum ignition energy is defined for each gas, as the mixture which is most flammable under thetest conditions.

It may also be given as the minimum electrical current to obtain ignition referred to that for methane.

1.3.3.3.3 Ignition temperatureThe ignition temperature also called the temperature of self-ignition, is the lowest temperature atwhich a mixture may ignite under certain conditions.

The minimum ignition temperature given in Tables is indicated for mixtures at atmospheric pressure.It corresponds to a mixture laying within the limits of flammability. See Table 2.

The ignition temperature rises as the mixture approaches the lower or upper limit (see Figure 8) or ifthe inert gas content increase (Figure 7).

Note: The flash point is the minimum temperature to which a flammable liquid is raised so that thevapour given off ignites in the presence of a flame, spark, etc.

1.3.3.3.4 Combustion rateDeflagration - Explosion - Detonation

The progress of combustion and the destructive effect of flammable mixtures may vary widely:

Deflagration and explosion :

The term explosion is sometimes given a general connotation which covers both deflagrations anddetonations.

The propagation of the combustion of a deflagration or explosion is effected mainly by the thermalconductivity and to a lesser extent by the effects of diffusion.

In a deflagration the combustion rate, particularly in the vicinity of the lower and upper limits offlammability, is of the order of a few dm/s (Approx 1 m/s). In an explosion combustion rates ofseveral m/s (usually less than 100 m/s) are producted.

Propagation velocity varies considerably as a function of the dimensions of the enclosure.

Detonation:

In detonation the flame propagation is supersonic. When an explosive mixture is ignited, theexplosions may be converted into detonations, the reaction then being brought about by the shockwave.

Detonations are also distinguished by the fact that the speed of combustion is comparatively constant.e.g. the limits of flammability of hydrogen in air.

in practice, however, detonation is uncertain.

EXAMPLE

Figure 6 is a diagram showing the distribution of the zones for the air hydrogen mixture.

The limits of flammability of hydrogen in air vary from 4 to 75% by volume. Laboratory testsconducted with pipes of less than 50 mm diameter and under certain conditions have, however, shownthat detonations can only be produced with hydrogen-air mixtures between the limits from 18 to59 vol %.





1.3.3.3.5 Pressure developedExplosive ignition generally develops a high pressure in a closed system which varies with the volumeand shape of the system owing to the cooling effect of the walls.

The figures given in the tables unless otherwise stated indicate starting from atmospheric pressure themixture which gives the highest pressure under the test conditions.

Up to 10 bar initial pressure the multiplying factor of the initial pressure remains approximatelyconstant; above 10 bar it increases.

When in a stabilised environment, there is deflagration after detonation, the pressure may reach :

• 7 times the initial pressure with air

• 12 times the initial pressure with oxygen

When there is detonation the pressure attained is multiplied by 2 in the stock wave and by 5 in thereflected wave.

In all cases the pressures developed are much higher than the design pressure of the installations.

1.3.3.4 Influencing Factors

1.3.3.4.1 Effects of pressureSmall variations in atmospheric pressure have only a negligible effect on the flammability limits.

On the other hand when the pressure rises there may be appreciable variations in flammability limitsas shown by the figures below for methane.

PERCENT BY VOLUME

Methane Pressure Lower Limit Upper Limit

1013 mb 4.5 15in air

100 bar 3.7 56

1013 mb 5 58in oxygen

100 bar 5 90

The pressure sometimes has the effect of lowering the ignition temperature, even to a considerableextent. This effect is added to the previous one, the two together acting towards the aggravation ofdanger.

It should also be noted that with increase of pressure the results are aggravated. When the initialpressure is high the developed pressure reached is much greater and the explosive effect increases.

The effect of pressure on the ignition temperature is illustrated in Figure 7.





Figure 7 : Self-ignition temperature as a function of pressure in pure oxygen (stoichiometric mixture)

1.3.3.4.2 Effect of temperatureAt atmospheric pressure or at a given pressure, if the temperature of a mixture rises, the lower limit islowered slightly and the upper limit is raised.

As long as 200°C is not exceeded, the variation remains comparatively small, as shown by theexamples below.

PERCENT BY VOLUME

Temp °C Lower Limit Upper Limit

20 5 15Methane in air 100 4.7 15.7

25 6.6

100 5.5 57Trichloroethane inoxygen

200 4.1 60

It may also be said that a high temperature facilitates ignition by reducing the amount of energyneeded.

1.3.3.4.3 Effect of an inert gasIn air deficient of oxygen and above a certain total concentration of nitrogen there is no possibility ofignition, whatever the ratio of fuel to oxygen.

The progressive narrowing of the limits of flammability leading to complete impossibility for ignitionare shown graphically in Figure 8.





Figure 8 : Flammability diagram

1.3.3.4.4 Other effectsThe two limits of flammability are not absolutely specific, they depend on test conditions since theirvalues vary slightly with other factors, such as :

• the shape of systems

• the volume of systems

• the intensity of the source of heat

The dimensions, especially length-to-width-ratio, are important for the development of detonations.Long pipes are unfavourable in that respect.

Humidity of the gas may also play a part but its influence is negligible.

We may also mention the effect of the composition of the mixture on the ignition temperatureaccording to whether a mixture is near to the lower or the upper limit and according to whether it is amixture with air, with oxygen, or with air that is deficient or enriched. However, these variousmixture possibilities have little effect upon the ignition temperature.

Other parameters, more directly connected with the characteristics of the products, may clarify thedevelopment of an accident. They shall be taken into consideration either in explaining an accident orin order to specify the choice of products.

Characteristics for cleaning products such as the following may be involved :

• difficulty of removal

• ease of evaporation (evaporation rate)

• heat of evaporation

The concentration of a mixture may also determine other characteristics which may modify dangersbetween one concentration and another or one product and another.

• the mixture which develops the highest pressure on explosion

• the mixture which requires the lowest temperature for spontaneous ignition

• the mixture which is most incendiary, i.e. the most able to transmit ignition when started

• the mixture which is most inflammable, i.e. the one that requires the smallest ignition energy

1.3.3.5 Self-IgnitionA mixture of flammable gas and air or oxygen which is heated may reach a temperature at which itbecomes the seat of a chemical oxidation reaction. This reaction is slow at first but may grow rapidlyand finally suddenly initiate ignition in the mass when the temperature of self ignition or ignition isreached.

A high initial temperature favours the development of the reaction.

This phenomenon is called self ignition (spontaneous ignition).

It assumes an explosive nature when the temperature of ignition is reached.





The minimum ignition temperature depends upon the pressure and conditions (thickness, materials,shape and state of surface) and of the various reaction characteristics.

Figure 9 shows diagrammatically for a given pressure the limits of flammability as a function of thetemperature, the zone of slow reaction and the ignition temperature

Figure 9 : Self-ignition: zone of slow reaction

1. Poor mixture which does notpropagate the flame

2. Mixture which propagates the flame

3. Rich mixture which does notpropagate the flame

4. Zone of slow reaction

Li Lower limit of flammability

Ls Upper limit of flammability

1.3.4 Physiological Risks

1.3.4.1 Nature of risksThe main risk for personnel is that of changes in the composition of the breathing air.

Oxygen is essential to maintain life and it is vital to ensure that it is present in sufficient quantities inthe air breathed.

Normal air contains 21% oxygen and if there is any deviation from this concentration, especially if theoxygen concentration is lowered, there may be danger.

In the case of installation or maintenance of a system this danger is essentially connected with the useof nitrogen during the operation of blowing, inerting or testing.

1.3.4.2 Effect of oxygen enrichmentBreathing pure oxygen is not dangerous except in the event of prolonged exposure at highconcentration or under pressure.

1.3.4.3 Physiological effects of oxygen deficiencyThe figures given in Figure 10 are rather conservative.

The values indicated are those allowed for Zones located at sea level (1013 mb). When at an altitude,these values shall be increased proportionately to the reduction of barometric pressure in order tomaintain the same level of partial pressure for the oxygen.

The value of 17% shall be raised from 0.20% to 0.27% per 100 metres. When increasing from 0 to2000 metres in altitude acclimatisation allows adaptation varying according to the individual andreduction of the altitude is proportional to the decrease of partial pressure.





Figure 10 : Thresholds of Physiological Dangers

The above figures result from commonly adopted values admitted in the specialist literature.

Apart from the dangers connected with the solubility of nitrogen in the blood during respiration underpressure, the danger is that of reducing the oxygen concentration and causing asphyxia.

Asphyxia may develop suddenly or slowly and insidiously.

In the sudden process the victim falls unconscious. A few seconds to a few minutes from entering thedangerous atmosphere suffice, according to the degree of oxygen deficiency or according to theindividual.

Generally, oxygen deficiency leads to a lowering of vigilance, distortion of judgement and even asensation of well-being.

As nitrogen is odourless, the danger is not readily detected.

This subsequent loss of consciousness renders the victim incapable of self rescue.

Exposure to pure nitrogen quickly results in death or more or less serious after-effects throughirreversible damage of the cells of the brain.

1.3.4.4 ThresholdsIn practice it is advisable to adopt 17% as the minimum concentration of oxygen, below which it willbe considered that there is danger.

With regard to oxygen-enriched atmospheres there are few physiological dangers. On the other hand,as we have seen in 1.3.2, dangers of ignition increase rapidly when the normal concentration in the airis exceeded.

NB For additional information refer to ICC document 876E entitled ‘Prevention of Accidentsarising from enrichment or deficiency of oxygen in the atmosphere’.





1.4 Causes of AccidentsIn this section we list the various kinds of accident and their possible causes.

1.4.0 GeneralThe reader is reminded that Combustion requires the presence of three factors.

• Oxygen

• Combustible Material

• Means of Ignition

See Table I, 1.3.1.7.

The list that follows although comparatively long does not claim to be absolutely complete.

1.4.1 Internal Spontaneous IgnitionAccidents due to internal ignition are the most typical kind of accident and its various aspects andcauses are generally covered by the term “spontaneous ignition”.

Spontaneous ignition may occur in an installation in service, at rest or being worked on (stopping,putting into service, handling, inspection, survey, maintenance, modification).

Self-ignition may have serious consequences, its unexpectedness surprising and its effects sometimesviolent.

The ignition process is described in 1.3.1.7.

The venting of large quantities of oxygen may produce an enrichment which may be the source of anew ignition in the area affected.

When perforation or bursting occur in the ground or next to a building the accident may also provokeejection of sand, earth, stones or other materials.

In oxygen systems spontaneous internal ignition without external energy supply is the most typicalaccident.

External causes can also be the origin of a spontaneous ignition of the circuit. The cause of ignitionmay then be the energy developed by a shock or a rupture, or the effects of velocity of the gas beingvented.

1.4.2 Causes of Internal IgnitionInternal ignition is caused by any phenomenon able to impart to an element a calorific energysufficient to provoke ignition, without addition of outside energy.

The use of materials of too low ignition temperature or the presence of extraneous elements that areeasily combustible may cause ignition.

Various phenomena are liable to bring materials to an ignition temperature. For instance :

• Physical/Mechanical phenomena

• Chemical phenomena

• Electrical phenomena

1.4.2.1 Physical/mechanical phenomena

1.4.2.1.1 Friction of particles or foreign bodiesCaught by the flow of gas the particles become heated by friction when in contact with the walls.This possible source of heating necessitates the limitation of gas velocities. (See 4.1)

However, it should be noted that the temperature of particles carried in the gas stream is very quicklylowered to that of the ambient gas.





1.4.2.1.2 Impact and incrustation of particlesSimilarly, when carried by the flow of gas, particles become heated on encountering an obstacle. Thismay have a cumulative effect. If the heated particles have become encrusted on an organic material oflow thermal conductivity, a localised rise in temperature can occur. If the particles are themselvescombustible, the risk is greater.

Another source of heating which is an aggravating factor is the focalisation of particles which mayoccur at a bend.

1.4.2.1.3 Abnormal or accidental friction within componentsFor example :

Abnormal friction on opening a valve. Friction within volumetric meters having moving parts.

1.4.2.1.4 VibrationAn organic element subjected to a high rate of vibration rises in temperature. There can becombustion only if the ignition temperature is reached before the element loses its consistency underthe effect of the temperature and thus stop vibrating.

1.4.2.1.5 FracturesIn the case of a rapid fracture the temperature of the material rises in the fracture zone. The roughnessof the surface of the fracture may also favour ignition by the high surface/mass ratio. In addition tofractures a noticeable temperature rise may occur with deformation due to :

• Elongation

• Flexing

• Shearing

1.4.2.1.6 Adiabatic compressionThe adiabatic compression of oxygen may involve local rises of temperature sufficient to causeignition. This can occur when there is rapid pressurisation of an oxygen system.

Tl and Pl being the absolute initial temperature and pressure, the temperature T2 in correlation withthe final pressure P2 is determined by the following formula :

28.01

12

112

12

≈

=

−

PP

TPP

TTγ

γ

CPγ = CV=

Ratio of specific heats at constant pressure andconstant volume.

The curve Fig. 11 shows the riseof temperature obtained byadiabatic compression starting at15°C between 0 and 100 bars.The curve shows that this rise canbe considerable, but in actualpractise it is balanced by theunavoidable losses of heat.

1.4.2.1.7 Thermodynamic phenomenaThe flow of gases, in bodies having sectional changes and complex profiles, may form eddys.Similarly, in cul-de-sacs, metallic particles may be subjected to vibration or resonance.

These may cause heating.





1.4.2.2 Chemical Phenomena

1.4.2.2.1 Exothermic phenomenaThis phenomenon concerns easily oxidisable products whose exothermic reaction may produce a riseof temperature sufficient to initiate ignition. Ignition will be avoided by the strict selection ofmaterials and effective cleaning.

This phenomena can only occur when foreign matter in the system reacts with oxygen.

1.4.2.3 Electrical Phenomena

1.4.2.3.1 Heating due to electric currentsFor various reasons pipes or components can be subjected to the passage of an electric current. Partsor components can be insulated from the rest of the installation. Conductive particles are able tobridge over the insulated parts, the current passes through these particles and become heated by theJoule Effect until the point of ignition.

Electric arcing can also occur.

1.4.2.3.2 Electrostatic chargesPhenomena relating to static electricity are little known in relation to oxygen systems, howeverelectrostatic discharges cannot be excluded as a cause of ignition. in particular charges whichaccumulate on parts that are electrically insulated.

1.4.2.3.3 Dust concentrationDust concentrations may be produced bv electrostatic phenomena, residual magnetism at the free endof the pipeline, for example at an insulating Joint.

1.4.2.3.4 Electrolytic phenomenaThis may occur with moist oxygen in the presence of metals or alloy of a different nature. Oxygenbeing maintained at low moisture content, these phenomena are not to be feared any more, they weremainly a cause of corrosion.

1.4.3 Factors Influencing Ignition

1.4.3.1 Lack of cleanlinessForeign bodies may cause ignition by :

• Friction or Impact

• Accumulation of static electricity and discharge

• Joule Effect by accumulation of dust deposits.

They may also transmit ignition because of their lower ignition temperature.

1.4.3.2 Abnormally high velocityThe origin of an abnormal high velocity may be :

• Uncontrolled flow

• Venting too rapidly

• Fracture of a component or of the pipeline

• Too rapid pressurisation (this last case may also be accompanied by the effects of adiabaticcompression)

• Leakage

These may displace foreign bodies and cause other phenomena such as thermodynamic heating,vibrations etc.

1.4.3.3 Incompatible or unsuitable materialsThe presence of these materials may be due to incorrect choice of materials that do not conform tospecifications.





1.4.3.4 Temporary connections to other networksAccidents have occurred by inadvertently connecting oxygen pipelines to other gas lines.

A more frequent occurrence is making temporary connections to other networks, for exampleconnection to a nitrogen or air line for purging or pressurisation which can lead to the introduction offoreign matter in the oxygen line.

1.4.3.5 Mechanical accidents on installationsSuch accidents may be due to :

• Bursting under gas pressure

• Fracture under mechanical stress

• Failure of equipment

• Blockage

• Over speeding of rotary meters

• Inadequate supporting of venting and main equipment

• Thermal stresses (Expansion/Contraction)

• Ground Stresses

• Various defects or bad workmanship

• Hydrostatic stresses (water table)

1.4.3.6 Poor workmanship & maintenanceBad assembly (internal assembly of a component or assembly of the whole) may be a source oftension, stress, vibration causing heating, dangerous deformation and even rupture.

An undesirable object (a loose nut, washer, various elements) may originate from an element locatedupstream, which is badly designed or fitted.

A leak at a joint may be the origin of an ignition or it can be a contributory or aggravating factor,.

1.4.3.7 Unauthorised actionThis includes non-observance of general- and safety rules such as

• Operating instructions

• Prohibition of drilling, welding etc of a pipeline

• Prohibition of smoking

(See section 6 for details)

1.4.4 External Causes of Accidents

1.4.4.1 Mechanical damageMechanical damage to the installations may be due to:

• The movement of vehicles or machines

• The movement of abnormal size transport and loads

• The blows of tools during digging operations

• The placing of sheet Diles or piles

• Loads upon the ground

• Explosives, shock wave

• The movement or anchoring of ships

They may cause : impact, penetration, tearing, crushing, wear.





1.4.4.2 Thermal EffectsThermal effects through heating or cooling may originate from :

• A hot spot (torch arc, etc)

• Hot products (metal, scale etc)

• Low temperatures (cold due to expansion of the gas)

• Very low temperatures (liquid oxygen, liquid nitrogen etc)

Thermal shocks may cause ignition by introducing energy from outside, or they may cause dangerouschange to the mechanical characteristics of the metal.

1.4.4.3 CorrosionExternal corrosion due to failure of the protective coating may cause deterioration of the pipes to thepoint where penetration or bursting may occur.

In the ground corrosion may be slow or rapid according to the corrosivity of the soil, and by thepresence of stray currents.

Corrosion by contact with other elements of different potential may result in penetration of the pipe.This may occur in the ground and above ground by contact with other elements.

In the case of above-ground structures corrosion by atmospheric pollution should also be taken intoconsideration.

1.4.4.4 Proximity of high tension electric cablesThe accidents caused by the proximity of high tension electric cables can be classed in threecategories, according to the nature of the electrical phenomenon.

(a) Direct Contact

This is an accidental contact or a discharge by short circuit to the earth in the case of default.The energy involved by this type of incident can result in penetration of the tube.

(b) Capacitive Connection

This is the capacitive influence on insulated section or pipe during positioning work so that itis recommended these sections are connected to earth before assembly.

(c) Inductive Connection

This is the influence of magnetic fields due to alternating current on electric cables runningparallel to the pipeline.

In all the above cases the pipeline may carry the electric current.

The following practices shall be prohibited due to the accidents they may involve.

• Connection of pipeline to other installations

• Conductive connection between pylon and pipeline

• Pipeline used as an earth

• Pipeline or installation in service used as an earth terminal during welding operations

(see Figure 52, Tables 13 & 14 and paras. 4.3.5.22 & 4.3.5.24)





1.4.4.5 Natural CausesMovements of the earth :

• ground slip

• subsidence

• erosion

• earthquake

• change in water table

and the elements :

• wind

• rain

• variations of temperature

• lightning

These causes may bring about deformation and even rupture, lightning may also cause fusion of metalor the passage of dangerous currents.

1.4.5 Internal Explosions in PipelinesThe presence of gas or flammable vapour in the oxygen may be due to the following reasons :

• Installation inadequately rinsed after cleaning with products which are flammable in oxygen.

• Feed-back of a combustible gas or product into the oxygen pipeline from a utilisation point.

• Incorrect connection.

These mixture may produce explosions.

An energy source is necessary to ignite the mixture, one of the energy sources mentioned in 1.4.2.

• An external source of heating

• Self ignition

• Ignition at a usage point resulting in flashback to the pipeline

As shown in 2.2.2.6 certain solvents in the presence of certain metals can produce explosive mixturesby chemical reaction.

1.4.6 Oxygen - Enriched AtmosphereAny enrichment of the air with oxygen will increase the risk of ignition especially of the clothing ofpersonnel. This risk is critical in trenches or enclosed spaces where repairs or modifications arecarried out. oxygen enrichment prohibits welding opertions.

Causes of oxygen enrichment may be :

• Leakage due to faulty equipment

• Perforation

• Porous metal

• Weld leakage

• Leakage at flanges and seals

• Valves leaking into work area

• Leakage from vent pipework

• Venting

• Purging

• Feed-back of oxygen due to incomplete purging before work or isolation

• Wrong usage or badly adjusted equipment

• Forbidden usage (Air refreshment, Ventilation, Pheumatic tools etc)

If there is leakage the oxygen concentration increases, this concentration in an area can also betransferred to any area from the point of leakage.





Apart from the cigarette we list other causes of ignition :

• Cutting and welding tools

• Electric welding processes

• Metal and scale projections from operations of either cutting or welding

• Sparks from electrical equipment or over-heating

• Sparks from grinding

• Sparks produced by impact

• Oxidation of paint during drying

1.4.7 Explosive AtmospheresAn atmosphere may become explosive if fuel gases are present, whether air or oxygen enriched air isinvolved.

Combustible gas or vapours may originate from :

• Vapour from products being stored or used e.g. degreasing agents

• Cases used with oxygen (Feed-back, Leakage)

• Equipment used (Cutting and Welding torches)

Ignition factors are the same as those mentioned in 1.4.6.

Special attention shall be paid to this danger when work is being carried out in a trench. (Note : Fuelgases are usually heavier than air).

1.4.8 Oxygen Deficient AtmosphereNitrogen is frequently used for cleaning, blowing, purging, leak-tightness and pressure testing.

Because of the physiological dangers of an atmosphere deficient in oxygen, precautions shall be takento ensure that such a condition does not exist due to the use of nitrogen.

Special attention shall be paid to this danger when work is being carried out in a trench. The dangerincreases when using cold nitrogen vaporised from liquid.

Cold gases are heavier than air and tend to concentrate at low level and are difficult to dissipate(Note : Nitrogen is normally lighter than air, but at 0°C is heavier than air at 15°C).

1.4.9 Normal Electrical DangersOxygen installations shall be protected against electrical dangers of the traditional type. Standardpractices or regulations shall be observed.

1.4.10 Points Where Accidents May OccurA pipeline for which these recommendations for construction and cleanliness have been observedcannot normally be the origin of an accident.

on the other hand the fitted components constitute the weak points of installation where ignitiongenerally originates. Because of this, components shall be restricted to the minimum necessary. Thepoints where there are components shall be points where generally speaking protection shall beassured (see 4.2).

1.4.11 Circumstances of AccidentsExperience has shown that a large proportion of accidents occur after modification maintenance,putting into service or return to service after a short time.

Generally, there is at the time of an accident, a high gas velocity, but not always, some accidents haveoccurred in installations under pressure but at rest.





1.4.12 Synoptic TableTable III summaries the causes and effects of accidents in oxygen distribution networks





1.5 REGULATIONS1.5.1 Official Regulations and Recommendations

As a general rule the regulations, whether national or local, refer to various gaseous products underpressure. A distinction is generally made between various gases under pressure, combustible, toxic,corrosive, combustive, etc.

Few countries have regulations which take into account all characteristics of gaseous oxygen.

West Germany has official regulations, according to which materials are tested for their suitability,supplemented by authorisation for the use of non-metallic materials with oxygen.

On the European level there are also the recommendations of the European Economic Communities(EEC). These recommendations concern oxygen installations for iron and steelmaking. They weredrafted by the ‘General Commission on Safety and Hygiene in the Iron and Steel Industry’.

Professional organisations have in most countries issued recommendations for the use of members,namely :

• The committee of oxygen producers:

• The IGC in Europe (Industrial Cases Committee)

• The CCA in U.S.A. (Compressed Gases Association)

• The technical association of the iron and steel industry

• The chemical industries group

A number of companies have their own rules for design, installation and operation :

• Companies producing and distributing oxygen

• Iron and steel producing companies

• Chemical companies

• Petrochemical companies

1.5.2 Scope of Official RegulationsUsually the relevant regulations originate directly from those for pressure vessels or refer to them.

Essentially problems of mechanical strength are dealt with and the regulations, therefore, concern :

• The characteristics of materials

• The allowable stress of materials

• The methods of testing or of approval

• The methods of calculation

• The pressure safety devices

• Inspections and repeat tests

A distinction may be made between factory pipelines and transportation pipelines.

Pipelines for the transportation of gases under pressure may also be subject to :

• Safety regulations related to pipeline route (extra thickness standards for burying and spacing ofpipes)

• Legal regulations concerning the land, which define the conditions of granting a right of way bythird parties for the laying, operation or maintenance of the pipes

• Commercial regulations associated with the license to operate relating to the pipeline

Valve stations or distribution stations may be subject to regulations with regard to construction.These regulations may affect the method of construction or lay down certain requirements concerninglocation, aesthetics or protection.





1.5.3 Environmental ProblemsIn addition to regulations concerning construction there are two other factors that may affect theenvironment, namely noise and cold due to expansion in the vicinity of distribution stations.

Specific regulations concerning noise show an increasing tendency in most countries.

1.5.4 Dominance of Local LawAll official, compulsory or public order regulations will prevail in the country or zone of application.

The legal provisions shall always remain preponderant over the provisions of this code.

1.6 Guidance for the Prevention of, Protection Against, and Means ofCombating Accidents

1.6.0 GeneralIn earlier sections we have observed the characterisics of risks associated with oxygen distributioninstallations. In this connection we have already defined a number of preventive parameters withregard to concentration and velocity.

In the sections that follow we shall develop the rules it is appropriate to observe in order to design,construct and operate the installations with a minimum of risk. These measures relating to theprevention of, protection against, and the means of combating accidents will be dealt with from thevarious points of view enumerated below :

1.6.1 PreventionPrevention concerns the measures which should be taken in connection with installations and actionswith a view to eliminating the causes of accidents.

1.6.1.1 For the whole• Competent personnel forewarned of the problems

• Limitation of the gas velocity

• Cleanliness of installations and installed equipment

• Electrical continuity of installations and equipment (see 4.2.5.14)

• Knowledge of the environment

• Control and supervision of work

1.6.1.2 For the equipment• Selection of materials

• General Design

• Design of equipment

• Method construction and control

1.6.1.3 For materials

• Selection of products

• Procedures for use

1.6.1.4 For the installations• Design of installations

• Selection of operating procedures

• Automatic controls

• Control and detection instruments

• Safety equipment

• Assembly procedures





1.6.1.5 For work on the installations• Programme of inspection and maintenance

• working procedures

• detection of oxygen content

• ventilation

• training of personnel

1.6.1.6 Protection gainst third parties• pipeline identification

• keeping documents up to date

• supervision of installations

1.6.2 Protection of PersonsMeasures to be taken to minimise the consequences of an accident.

• Design

• Electrical protection

• Protective screens and enclosures

• Access and escape

• Escape facilities

1.6.3 Combating AccidentsThe actions taken in order to arrest or limit the extent of an accident or its consequences.

• Emergency planning

• Emergency action

• Safety training

• Remote operations

• Means

• Extinguisher

• Sprinkler

• Pipeline purging and venting

• Emergency Notices

• Plans of action

• Persons who act

• Training of action teams





1.7 Inspection of Equipment and Installations1.7.1 The Need for Inspection

In order to avoid accidents, oxygen distribution installations shall be correctly constructed and complywith normal technical rules and the recommendations of this code.

Inspection is required to ensure that the rules are observed.

1.7.2 Inspection

1.7.2.1 ScopeInspection shall be applied to

• cleanliness required

• materials

• design of the pipeline and installation

• construction (manufacture, welding, laying, etc)

• testing

• operation and maintenance

1.7.2.2 ApplicationInspection is carried out

• during design

• on the components or elements manufactured at the suppliers works

• on components supplied from stockists

• at the work site

• before putting into service

• at the time of putting into service

• during operation

• during maintenance

1.7.3 Training of PersonnelAt a large work site it is necessary to introduce specialist personnel to ensure control.

In many cases, inspection will be carried out by construction personnel or by operating personnel.

Personnel shall have been made aware of the dangers inherent in oxygen. They will have receivedadequate training.

Personnel installing, operating or maintaining the pipelines shall also be informed and trained withregard to possible electrical influences and to the rules to be observed.

For large pipeline networks, service teams trained with maintenance or operational personnel capableof being mobilised in case of emergency shall be made available



Part 2 : Materials and Products - Cleaning


The Transportation and Distribution of Oxygen by PipelinePart 2 : Materials and Products - Cleaning

IGC 13/82/E











SECTION 2: MATERIALS AND PRODUCTS - CLEANING...................................................................................4

2.1 MATERIALS AND PRODUCTS...................................................................................................................................42.1.0 General..................................................................................................................................................................4

2.1.0.1 Material selection ............................................................................................................................................ 42.1.0.1 Recommended materials................................................................................................................................... 4

2.1.1 Metals ....................................................................................................................................................................42.1.1.1 Behaviour in oxygen........................................................................................................................................ 42.1.1.2 The metals in general use.................................................................................................................................. 42.1.1.3 Cast iron .......................................................................................................................................................... 52.1.1.4 Aluminium and its alloys.................................................................................................................................. 52.1.1.5 Metal deposits.................................................................................................................................................. 5

2.1.2 Plastic or Organic Materials.............................................................................................................................82.1.2.1 Behaviour in oxygen........................................................................................................................................ 82.1.2.2 Permissible uses ............................................................................................................................................... 82.1.2.3 Mass limitations............................................................................................................................................... 82.1.2.4 Material selection ............................................................................................................................................ 82.1.2.5 Identification ................................................................................................................................................... 82.1.2.6 Reinforcements and additives ........................................................................................................................... 82.1.2.7 Material characteristics..................................................................................................................................... 82.1.2.8 Recommended resins and elastomers................................................................................................................ 9

2.1.3 Other Materials....................................................................................................................................................92.1.3.1 Examples ......................................................................................................................................................... 92.1.3.2 Proof of compatibility ...................................................................................................................................... 92.1.3.3 Ceramics........................................................................................................................................................ 10

2.1.4 Gaskets, Seals, Packings, Sealing Compounds........................................................................................... 102.1.4.1 Material selection .......................................................................................................................................... 102.1.4.2 Seals for Flanges and Component Elements.................................................................................................... 102.1.4.3 Valve seat inserts ........................................................................................................................................... 102.1.4.4 Gland seals..................................................................................................................................................... 112.1.4.5 Thread seals ................................................................................................................................................... 112.1.4.6 Sealing compounds......................................................................................................................................... 11

2.2 MISCELLANEOUS PRODUCTS.................................................................................................................................112.2.1 Lubricants .......................................................................................................................................................... 11

2.2.1.1 Limitations of use........................................................................................................................................... 112.2.1.2 Classification ................................................................................................................................................. 112.2.1.3 Lubrication products ...................................................................................................................................... 112.2.1.4 Recommended lubricants................................................................................................................................ 11

2.2.2 Degreasing Agents and Solvents.................................................................................................................... 132.2.2.1 General .......................................................................................................................................................... 132.2.2.2 Halogenated solvents ..................................................................................................................................... 132.2.2.3 Solvent Characteristics ................................................................................................................................... 132.2.2.4 Formation of explosive mixtures..................................................................................................................... 152.2.2.5 Temperature and ultra violet effects on solvents.............................................................................................. 152.2.2.6 Reaction with Metals...................................................................................................................................... 152.2.2.7 Other cleaning agents..................................................................................................................................... 152.2.2.8 Prohibited degreasing agents .......................................................................................................................... 15

2.2.3 Cleaning Agents and Protective Products.................................................................................................... 162.2.3.1 General .......................................................................................................................................................... 162.2.3.2 Chemical cleaning and descaling agents.......................................................................................................... 162.2.3.3 Chemical protective agents............................................................................................................................. 162.2.3.4 Other products ............................................................................................................................................... 16

2.2.4 Mechanical Cleaning Products and Equipment.......................................................................................... 162.2.4.1 Abrasives ....................................................................................................................................................... 162.2.4.2 Propellant gas................................................................................................................................................. 172.2.4.3 Brushes.......................................................................................................................................................... 172.2.4.4 Cleaning pigs ................................................................................................................................................. 172.2.4.5 Cleaning cloths .............................................................................................................................................. 17

2.2.5 Purging and Testing Gases............................................................................................................................. 172.2.5.1 Nitrogen ........................................................................................................................................................ 172.2.5.2 Air ................................................................................................................................................................. 17

2.2.6 Dessicating Products ....................................................................................................................................... 172.2.6.1 Products......................................................................................................................................................... 172.2.6.2 Application.................................................................................................................................................... 172.2.6.3 Quantities ...................................................................................................................................................... 17





2.2.7 Leak Detectors .................................................................................................................................................. 182.2.7.1 Products for external use ................................................................................................................................ 182.2.7.2 Products for internal use ................................................................................................................................. 18

2.2.8 Other Products.................................................................................................................................................. 182.2.8.1 Water ............................................................................................................................................................ 182.2.8.2 Anti-freeze..................................................................................................................................................... 182.2.8.3 Paints............................................................................................................................................................. 182.2.8.4 Products for temporary sealing ....................................................................................................................... 182.2.8.5 Sound insulation products............................................................................................................................... 182.2.8.6 Other Products ............................................................................................................................................... 18

2.3 CLEANING ................................................................................................................................................................192.3.0 General Considerations................................................................................................................................... 19

2.3.0.1 Cleanliness..................................................................................................................................................... 192.3.0.2 Contaminants................................................................................................................................................. 192.3.0.3 Object and nature of cleaning......................................................................................................................... 20

2.3.1 Preliminary Cleaning ...................................................................................................................................... 202.3.2 Degreasing With Solvents ............................................................................................................................... 20

2.3.2.1 Products......................................................................................................................................................... 202.3.2.2 Degreasing by immersion............................................................................................................................... 202.3.2.3 Degreasing by circulation............................................................................................................................... 222.3.2.4 Degreasing by vaporisation ............................................................................................................................ 222.3.2.5 Cleanliness of solvents................................................................................................................................... 222.3.2.6 Elimination of solvent residues ....................................................................................................................... 22

2.3.3 Degreasing with Water Solutions or Steam................................................................................................. 232.3.3.1 Methods......................................................................................................................................................... 232.3.3.2 Applications .................................................................................................................................................. 23

2.3.4 Treatment with Acid Products........................................................................................................................ 232.3.4.1 Aims and effects of this treatment .................................................................................................................. 232.3.4.2 Products......................................................................................................................................................... 232.3.4.3 Methods......................................................................................................................................................... 232.3.4.4 Chemical pickling .......................................................................................................................................... 232.3.4.5 Phosphating and passivation........................................................................................................................... 232.3.4.6 Duration of treatments.................................................................................................................................... 25

2.3.5 Mechanical Cleaning ....................................................................................................................................... 252.3.5.1 Processes and applications ............................................................................................................................. 252.3.5.2 Products and equipment ................................................................................................................................. 252.3.5.3 Manual methods............................................................................................................................................. 252.3.5.4 Sand and shot-blasting.................................................................................................................................... 252.3.5.5 Passage of cleaning pigs ................................................................................................................................. 252.3.5.6 Blowing out the pipelines ............................................................................................................................... 262.3.5.7 Vacuum cleaning............................................................................................................................................ 26

2.3.6 Cleaning of Components and Equipment..................................................................................................... 262.3.6.1 Cleaning of components................................................................................................................................. 262.3.6.2 Cleaning prefabricated pipework .................................................................................................................... 272.3.6.3 Cleaning the pipes.......................................................................................................................................... 27

2.3.7 Cleaning the Pipelines..................................................................................................................................... 272.3.7.1 Methods......................................................................................................................................................... 272.3.7.2 Pipelines constructed with unclean pipes ........................................................................................................ 282.3.7.3 Pipelines constructed-with clean pipes............................................................................................................ 28

2.3.8 Level of Cleanliness and Control................................................................................................................... 282.3.8.1 General .......................................................................................................................................................... 282.3.8.2 Control of cleanliness..................................................................................................................................... 282.3.8.3 Direct control of degreasing............................................................................................................................ 292.3.8.4 Indirect control of degreasing.......................................................................................................................... 292.3.8.5 Methods of inspection .................................................................................................................................... 29

2.3.9 Preservation of the Cleanliness Obtained.................................................................................................... 292.3.9.1 General .......................................................................................................................................................... 292.3.9.2 Packaging of small items................................................................................................................................ 292.3.9.3 Sealing of components and sections of pipework ............................................................................................ 302.3.9.4 Sealing pipes.................................................................................................................................................. 302.3.9.5 Drying agents................................................................................................................................................. 302.3.9.6 Inerting.......................................................................................................................................................... 302.3.9.7 Labelling........................................................................................................................................................ 30





SECTION 2: MATERIALS AND PRODUCTS - CLEANING

2.1 Materials and Products

2.1.0 General

2.1.0.1 Material selectionIn this part we consider the choice of materials. Metals are generally speaking materials of welldefined composition, worked at high temperature.

This is often not the case with numerous other materials such as plastics, lubricants and various otherproducts. This is because of the difference in procedure for manufacture, in the use of fillers and inthe multitude of products manufactured each for a very specific industrial need.

It is necessary to state that the materials indicated below are in many cases a guide which will assist inmaking a choice but that it is necessary to make sure that chemical and physical qualities aremaintained.

A single commercial name may designate a whole family of Products which are not necessarily allusable with oxygen. It is, therefore, necessary to specify the quality and type corresponding to thecomposition and manufacture which have been judged to be valid for the specific use to which theproduct is to be put.

2.1.0.1 Recommended materialsMetals are recommended for the construction of components and pipelines.Non-metallic materials may be used only for the applications indicated in 2.1.2 and subject to carefulselection.

2.1.1 Metals

2.1.1.1 Behaviour in oxygenMetallic materials generally have a high ignition temperature in oxygen (see Table iv).• Copper and its alloys, nickel and its alloys (monel, inconel) ignite only with difficulty.• Carbon steel and stainless steel enable combustion to continue very easily by reason of the heat

released provided that the supply of oxygen remains sufficient to support the combustion.• The thermal conductivity of stainless steel is less that that of carbon steel.• The ignition temperature of stainless steel is higher than that of carbon steel but it burns more

rapidly and with greater intensity than the latter.• Aluminium and its alloys burn in the gas phase after melting and evaporation of the metal.

2.1.1.2 The metals in general useThe metals in general use for the construction of components and elements of pipelines are:• nickel and its alloys (monel, inconel... )• copper and its alloys (bronzes, brasses... )• unalloyed or low alloy steels and cast steels• stainless steels.In the case of certain components, part or all of the constituent metals is the subject ofrecommendations or restrictions stated in 3.6 in conjunction with the following considerations:• design of the installation• conditions of operation (velocity, pressure, temperature)• function of the component• design of the component• presence of plastic or organic materials• safety devices





2.1.1.3 Cast ironLamellar or spheroidal graphite cast irons whether alloyed or not may be used for the fabrication ofcomponents on condition that these components do not have to withstand forces due to gas pressure.

For making pressurised enclosures certain cast irons may be employed under certain conditions fixedby the legislation in force in the country.

2.1.1.4 Aluminium and its alloysFor pipelines covered by this code the use of aluminium and its alloys should be avoided as far aspossible unless experience and testing has demonstrated its safe use.

2.1.1.5 Metal depositsMetal deposits made electrolytically or by welding or brazing are permitted on condition that:• the application processes do not introduce other elements incompatible with oxygen.• the materials (both base and deposit) are chosen as a function of their respective characteristics so

as to ensure perfect adhesion of one to the other.Typical uses:• preventing corrosion• reducing friction -• increasing locally surface hardness• improvement of heat dispersion













2.1.2 Plastic or Organic Materials

2.1.2.1 Behaviour in oxygenPlastic or organic materials have a distinctly lower ignition temperature than metallic materials (seeTable v).

If ignited they may eventually heat particles and adjacent metal components to the point of ignition. Itis, therefore, good practice to use such materials in the smallest possible quantities and only inintimate contact with metallic parts of greater mass and good conductivity to dissipate the heat.Copper and most of its alloys possess this quality.

For a given ignition temperature, plastic and organic materials with less heat of combustion and alower combustion rate, are preferred to reduce the possibility of transitting heat to the metal.

2.1.2.2 Permissible usesThe use of plastic or organic materials in direct contact with oxygen shall be limited to the following:(See 3.6)

• seals and packings in components and assemblies• deformable elements (diaphragms) in servomotors and regulating devices.• antifriction elements (pedestal and thrust bearings)• antifriction coatings• electrical insulation for cathodic protection• hoses

2.1.2.3 Mass limitationsIn every case their mass shall be as small as possible and they shall be employed only when a metallicelement is unsuitable.

2.1.2.4 Material selectionIn countries where official regulations exist specifying the materials that may be used with oxygenand qualify their use (pressure, temperature functions), it is possible to choose among the productsrecommended, while nevertheless giving preference to fluorinated or chlorofluorinated resins andelastomers.

2.1.2.5 IdentificationIt is recommended that fluorinated elastomers (diaphragms, O-ring seals, etc) have a distinctive markto prevent any confusion with the elastomers.

2.1.2.6 Reinforcements and additivesFluorinated and chlorofluorinated resins can be reinforced with oxides, asbestos, glass ceramic, metalsand alloys in order to improve some of their mechanical properties. Such reinforcement shall notaffect resistance to ignition.

Similarly, certain methods of manufacture which involve the use of additives such as the binders shallnot lower ignition temperature below that of the base product.

It is therefore necessary to check for each batch that the products have the same ignition temperatureas the base product.

2.1.2.7 Material characteristicsIn the choice of plastic or organic material, selection according to the property of resistance to ignitionis of paramount importance. These materials shall, however, comply with other properties connectedwith their use:• friction properties• mechanical strength• resistance to wear• flexibility• sealing properties• insulation propertiesCertain characteristics may render plastic or organic materials unsuitable for a particular use, such as atendency to flow.





The PTFE’s (eg Teflon) while possessing excellent antifriction properties are products which floweasily.

By contrast the PTFCE’s (eg Voltalef, Kel-F) have slightly less antifriction properties but much betterresistance to flow. The fluorinated resins (PTFE) and the chlorofluorinated resins (PTFCE) also havea tendency to ‘sublimiate’ under certain conditions of pressure and teMDerature.

The various characteristics of these products can be modified or improved by means of fillersincorporated in the course of their manufacture (see 2.1.2.6).

Table VI summaries a number of initial recommendations for selection which will be elaborated in thesections that deal with the design of components.

TABLE VIPRODUCT PROPERTIES USES

PTFE and FEP Good antifriction

Tendency to flow

Tendency to sublimiate (Canbe reinforced to improvestrength)

Valve seats

Antifriction bearings

Antifriction coatings

Thrust washers

Thread seals

Gland Packings

PTFCE Harder than PTFE

Greater mechanical strengththan PTFE and FEP

Valve seats

Bearings

Insulating seals

Gland packings

Fluorinated chlorofluorinatedelastomers (Viton)

Flexibility

Elasticity

O-rings seals

Diaphragms

2.1.2.8 Recommended resins and elastomersAmong the fluorinated and chlorofluorinated resins and elastomers those listed below are acceptable:

Fluorinated resins• Polytetrafluorethylene (P.T.F.E) Teflon, Hostaflon, Soreflon, Fluon, Algoflou)*• Polyfluorethylene propylene (F.E.P) (Teflon FEP)*• Polyfluoride of vinylidene (P.V.F.2) (Kynar)*

Chlorofluorinated resins• Polymonochlorotrifluoroethylene (P.T.F.C.E) (Kel-F 300, Voltalef 300)*• Monochlorotrifluoroethylene-Fluorovinylidene copolymer (P.T.F.C.E) (Kel-F 500, Voltalef 500,

Diaflon)*Fluorinated elastomer• Flurovinylidene-hexafluoropropylene copolymer (Viton, Fluorel, Refset)*Chlorofluorinated elastomer• Fluorovinylidene-monochlorotrifluoroethylene copolymer (Kel-F 5 500)** Trade names of products in use at the time of publication.

2.1.3 Other Materials

2.1.3.1 ExamplesFilter elements can be made from sintered bronze, bronze alloy mesh, glass fibre or ceramic subject tothe recommendations of section 3.6.5.

2.1.3.2 Proof of compatibilityThe ignition temperature in oxygen of some of these materials, especially of asbestos compounds,varies with the method of manufacture and any additives (fillers or binders) used. They shall only beused if previous tests have proved their safe use.





2.1.3.3 CeramicsCeramics offer excellent resistance to ignition but their low mechanical strength generally limits theiruse.

2.1.4 Gaskets, Seals, Packings, Sealing Compounds

2.1.4.1 Material selectionThe materials that may be used for the manufacture of gaskets, seals and packings in flangeconnections, plugging devices, stuffing boxes, screw couplings, etc., shall be selected from amongthose mentioned in previous sections.• the metallic materials in 2.1.1.2• the resins and elastomers in 2.1.2.8• the miscellaneous materials in 2.1.3The choice will depend upon the form and use of the product.

2.1.4.2 Seals for Flanges and Component ElementsVarious types of seals which may be used are shown in 3.4

Types of seals and materials of construction are show in Table VII.

TABLE VII

TYPE OF SEAL SEAL MATERIAL

Flat seals Annealed red copper

Aluminium

Silver-gold

O-ring seals

(blind or hollow)

Silver copper

Stainless steel

Nickel, Monel, Iconel

Metallic

Seals of special shape and S seals Nickel, Monel, Iconel

Stainless steel

Carbon steel

Copper

Spiral wound gaskets

(Flat seals)

Spiral part: Stainless steel

Nickel, Monel

Iconel

Composite

Interpolation: Graphite,Ceramic PTFE,asbestos

Formed seals Fluorinated resins

Chlorofluorinated resins

O-ring seals Fluorinated elastomers

Chlorofluorinated elastomers

Moulded seals on a metallicsupport

Fluorinated elastomers

Chlorofluorinated elastomers

Non-metallic

(Flat seals in sheet form) Asbestos fibres with various binders

NOTE:For non-metallic materials, refer to 2.1.2 and 2.1.3 for precautions to be taken.

2.1.4.3 Valve seat insertsThe seals for valve seat inserts shall be made with Fluorinated and chlorofluorinated resins andelastomers. (See 2.1.2.8)





2.1.4.4 Gland sealsGland seals may be made by using fluorinated and chlorofluorinated resins and elastomers. They mayalso be made up of asbestos braid impregnated with PTFE. Certain type of graphite based seals maybe used.

Gland seals of uncompacted PTFE fibre or of PTFE powder are not recommended.

2.1.4.5 Thread sealsOnly PTFE tape may be used. The tape shall not protrude into the gas stream.

Vegetable fibres such as hemp, etc., are prohibited for use with oxygen.

2.1.4.6 Sealing compoundsAll products such as dressings, glues, sealing pastes, whether liquid or powder or paste, intented to -ensure leak-tightness or adhesion between elements shall not be used unless tests have proven them tobe safe with oxygen.

2.2 Miscellaneous Products

2.2.1 Lubricants

2.2.1.1 Limitations of useGenerally, the use of lubricants should be avoided, preference being given to devices that operatewithout lubrication,, The use of lubricant shall be strictly reduced to the minimum. It shouldpreferably be incorporated for life when the component is assembled and not be visible externally.

2.2.1.2 ClassificationThe lubricants for use with oxygen may be classified into two categories:a) Lubricants in direct contact with oxygen under pressure.

Certain national regulations specify for each product a maximum pressure and temperature.

b) Lubricants applied to components designed for use with oxygen but not in direct contact withthe gas, e.g. on gear boxes or other devices for the operation of valves. Steps shall be taken toavoid oxygen pressure build up in the enclosures containing these lubricants.

2.2.1.3 Lubrication productsAt present five basic products may be used for lubrication in the presence of gaseous oxygen:• graphite• molybdenum disulphide• fluorinated or non-fluorinated silicones• polymers of monochlorotrifluoroethylene• perfluorinated polyethersa) Graphite and molybdenum disulphide are generally supplied in the form of very fine dry

powders or packed in aerosols.

b) Silicones, polymers of monochlorotrifluoroethylene and perfluorinated polyethers are offeredin liquid form (oil) or in the form of pastes (greases).

c) The greases differ from the oils in that they contain a jelling product. This product shall benon-combustible (e.g. Silica gel).

2.2.1.4 Recommended lubricantsTable VIII divides the lubricants into those that may be used with oxygen under pressure and thosethat may only be used in contact with oxygen at low pressure subject to national regulations.









2.2.2 Degreasing Agents and Solvents

2.2.2.1 GeneralOils and greases are dangerous products in the presence of oxygen and their elimination shall,therefore, be correctly ensured before any equipment is put into service.

This section deals with degreasing products, most of which in the presence of air or oxygen are capbleof igniting or of creating explosive atmospheres.

Every degreasing operation shall be followed by the removal of the residual solvents. Nationalregulations shall be followed concerning the use of these products which are generally toxic,inflammable, whose vapours are heavier than air (protective clothing, ventilation, etc). Methods ofdegreasing and control are described in chapter 2.3.

2.2.2.2 Halogenated solventsHalogenated solvents such as the following solvents are suitable for use as degreasing agents.• Trichloroethylene• Dichloroethylene• Perchloroethylene• Trichloroethane• Pentachloroethane• Carbon tetrachloride• Methylene chloride• Monofluorotrichloroemthane• Difluorotetrachloroethane• Trifluorotrichloroethane, etc

2.2.2.3 Solvent CharacteristicsTable IX indicates the main characteristics of the most commonly used solvents.Table IX also shows the classification of solvents as a function of their toxicity, solvent power andflammability in oxygen.

Solvents are generally toxic and may act on the human body through inhalation, penetration of theskin and ingestion.

Dichloroethylene, Pentechloroethane, Carbon tetrachloride, Trichloroethylene,Difluorotetrachloroethane are not recommended due to their high toxicity, unless special precautionsare taken.









(1) The KAURI-BUTANOL index of a solvent corresponds to the volume of solvent which whenadded to a solution of kauri gum in butanol causes commencement of cloudiness in thesolution. The better the product is as a solvent, the higher the value of this figure.

(2) TLV. The TLV value (threshold limit value) is the maximum concentration of a substance inthe form of gas, vapour or body in suspension in the air at the place of work which accordingto present knowledge generally does not injure the health of an employee or disagreeablyinconvenience even after repeated or continuous exposure as a general rule for 8 hours a day or45 a week.

The figures shown are those published by the Ministry of labour and Social Affairs of the GermanFederal Republic.

(3) The evaporation rate is the ratio between the evaporation time of the liquid concerned and thatfor diethyleter at a temperature of 20 + 2’C and a relative humidity of 65% + 5%.

(4) The minimum ignition temperature is the minimum temperature of ignition of the mostflammable mixture with air or oxygen.

(5) The pressure developed in a closed vessel by the most explosive mixture ignited at 1013 mb.

SOLVENTS ARE USUALLY SUPPLIED IN UNSTABLISHED FORM

NOTE:The values given in this table are extracted from specialised publications.The choice of solvent for a given application shall be the best compromise basedon the variousproperties listed in the table IX and the following paragraphs.

2.2.2.4 Formation of explosive mixturesMost chlorinated solvents are capable, at moderate temperatures, of forming vapours which, undercertain concentrations with air or oxygen produce mixtures that are readily explosive. In addition,some mixtures of these chlorinated solvents with oxygen under pressure may ignite if theirtemperature exceeds 200’C.

In addition to avoiding localised heat concentrations.

It is recommended NOT to:• use heated chlorinated solvents• blow with hot air in order to dry elements degreased by means of a chlorinated solvent.• use chlorinated solvents for cleaning closed tanks or other elements where it is not possible to

ensure total removal of the solvent.

2.2.2.5 Temperature and ultra violet effects on solventsChlorinated or fluorinated solvents may decompose in the presence of sources of heat ( > 200°C) ultraviolet rays and of atmospheric humidity to form very toxic gases, e.g. phosgene.

Smoking and the performance of any operations involving the use of flame arcing or other source ofheat greater than 200ºC shall, therefore, be prohibited on premises where vapour of halogenatedsolvents are present.

2.2.2.6 Reaction with MetalsSome chlorinated or fluorinated solvents are capable of forming explosive products with alkali metalor alkaline earth metals, especially if the latter are in a finely divided state (chips, filings, etc).

Chlorinated solvents other than perchloroetylene for degreasing light alloys shall be stablised andproven suitable for the purposes.

2.2.2.7 Other cleaning agentsIt is also possible to use certain detergents or chemicals dissolved in hot or cold water provided thatthe compatibility of any residues with oxygen has been examined previously.

The degreasing power of these products is lower than that of halogenated solvents.

Their use also requires precautions detailed in 2.3 in particular the need for careful drying of the parts.

2.2.2.8 Prohibited degreasing agentsDerivatives of petroleum products (petrol, kerosine, acetone, etc) aliphatic and aromatic solvents,other than those listed in 2.2.2.2 and their derivatives like alcohols, esters and ketones which are soldunder different names shall not be used because they are highly flammable and also may have lowthreshold limit values (TLV).





2.2.3 Cleaning Agents and Protective ProductsThis section deals with descaling and chemically protective products. Products designed formechanical cleaning are dealt with in 2.2.4.

Methods of operation and control are dealt with in 2.3.it is compulsory to observe national regulations concerning the use and handling of these productswhich are generally toxic and corrosive.

2.2.3.1 GeneralScale, bituminous internal costings and certain varnishes generally cannot be removed from internalsurfaces by means of the solvents indicated in 2.2.2 but require other chemical or mechanicalcleaning.

Descaling lays the metal bare and thus renders it vulnerable to attack by corrosion. It is, generally,followed by the application of protective products that inhibit corrosion.

2.2.3.2 Chemical cleaning and descaling agentsAqueous solutions of acids such as :• sulphuric aicd, H2SO4

• hydrochloric acid, HCl• Nitric acid, HNO3

• Phosphoric acid H3PO4

may be used as chemical descaling agents.

The degrees of concentration and the temperatures for using these solutions are indicated in 2.3• Products with a hydrochloric acid base shall only be used for carbon and low alloy steels.• Products with a nitric acid base are intended only for non-ferrous metals such as aluminium,

copper and their alloys; they mainly serve to deoxidise and polish the metal.• Acid solutions which attack the base metal require the addition of inhibitors. For example nitric

acid and hydrochloric acid.

2.2.3.3 Chemical protective agentsAqueous solutions of :• phosphoric acid, H3PO4

• chromium, copper or manganese• salts soda, etcmay be used as protective agents.

2.2.3.4 Other productsThese are ready prepared products and solutions on the market designed either for descaling or foranticorrosive protection, or to fulfil both these functions simultaneously.

Manufacturers generally do not give the exact composition of their products.They may, therefore, not be used unless previous tests have proven safety of the products or their dryresidues for oxygen installations.

2.2.4 Mechanical Cleaning Products and EquipmentMechanical cleaning includes operations such as• sand blasting• brushing, grinding• scraping (‘pigging’), etcMethods of application and control are dealt with in 2.3.

2.2.4.1 AbrasivesAbrasives used for sandblasting operations should be inert in oxygen (free from oil or grease).Metallic shot (powders or grains of cast iron, iron, steel, etc) are capable of burning and initiatingignition. They shall, therefore be prohibited unless satisfactory removal can be assured.

Preferably use will be made of silica sands (if national regulations permit) or other products which arenot combustible in oxygen such as carburundum.





2.2.4.2 Propellant gasThe propellant gas for sanding and shot blasting operations shall be clean dry oil free air or nitrogen.Propellant shall be considered oil free if its content of oil and grease is less than 0.005 g/Nm3. It shallbe considered dry if its relative humidity is less than 30% at working pressure.

2.2.4.3 BrushesBrushes used for cleaning shall be of metal, with steel or bronze bristles. They shall be in goodconditions and perfectly degreased before use. Handles of small hand brushes may be of wood.

2.2.4.4 Cleaning pigsScrapers for pipelines (‘pigs’) shall be of metal. If they comprise brushes these shall comply with2.2.4.3. If they comp 1rise non-metallic sealing (cups) rubbing against the walls of the pipes, thesecups shall be made of fluorinated or chlorofluorinated resins or elastomers as indicated in 2.1.2.

2.2.4.5 Cleaning clothsCloths used for wiping components or small elements of pipelines shall be clean, free from traces ofoil or grease and lint free.

2.2.5 Purging and Testing Gases

2.2.5.1 NitrogenThe purging or testing gas will preferably be dry oil free nitrogen, taken:• from mobile transportation gas containers (cylinders, bundles, etc).• from direct evaporation of liquid nitrogen• from a nitrogen pipeline whose cleanliness has been verified

2.2.5.2 AirClean dry compressed air free from oil and grease may be used for purging or testing.Air shall be considered oil free if its content of oil and grease is less than 0.005 g/Nm3 and shall beconsidered dry if its relative humidity is less than 30% at working pressure.

NB: Oxygen shall not be used for cleaning of installations under any circumstances.

2.2.6 Dessicating ProductsOnce cleaned, the components or elements of a pipeline may be provided with dessicating agents so asto prevent, during the period of storage, any corrosion or other deterioration due to the humidity of theair enclosed at the time of plugging or packing.

2.2.6.1 ProductsThe following may be used as dessicating agents:• silica gels• regenerated clays• crystalline silico-aluminates of sodium• and calciumCertain colour additives may be included in the products to give an indication of the moisture content

2.2.6.2 ApplicationThese products shall be packed in fabric or plastic sachets which shall be firmly fixed to the sealingplugs or plates of the component or element of the pipeline. In this way the possibility of them beingforgotten and left inside the installations will be prevented.

Small, loose capsules which may be left inside the component when it is fitted to the installation shallnot be used.

2.2.6.3 QuantitiesIn order to be effective, the amount of dessicating agent shall be determined bearing in mind:• the permeability and surface area of its packaging• the storage time• the volume of air enclosed• the maximum percentage relative humidity permitted





2.2.7 Leak Detectors

2.2.7.1 Products for external useThe detection of possible leaks from a component or coupling device may be effected with the aid of a2% aqueous solution of Teepol.

Some ‘leak detector’ products packed in aerosols and used in the gas industry may also be used ifprevious tests have demonstrated their safe use with oxygen under their actual conditions of use.

In most cases the dry residues of these products are flammable.The introduction of any combustible leak detector products into the interior of a component or circuitshall be avoided.

The circuit shall be under pressure before application of the product. After testing, all traces of theproduct shall be removed with a clean, dry, lint-free cloth or by rinsing with potable water.

If the search for leaks is effected by filling the circuit with clean, dry air or nitrogen the same productsshall be used as for oxygen.

The use of a flame or burning object to detect a leak is prohibited.

2.2.7.2 Products for internal useLeaks may be traced by the injection of Halogen or other products (Helium, N2O) into the test gas andthe use of suitable detectors.

The use of odourising products is not recommended. Products currently on the market are toxic andflammable. Special precautions shall be taken according to the properties of the products injected.

2.2.8 Other Products

2.2.8.1 WaterIn the case of hydraulic testing of the pipeline potable water only shall be used providing this test ismade after cleaning and degreasing operations.

Pure water (potable or distilled) may be used as a hydraulic medium for control systems.

2.2.8.2 Anti-freezeMonoethylene glycol may be used as an anti-freeze addition in water. However, its content shall notexceed 20% by volume.

Care shall be taken to ensure that water does not evaporate and leave residues of monoethylene glycolwhich is combustible in oxygen.

If the system includes filtration, care shall be taken that filter elements have a sufficient permeabilityto prevent separation of the anti-freeze additives.

For example, solution of water glycol may be separated by sieves of a permeability of 20 microns.

2.2.8.3 PaintsAll paints and varnishes are prohibited inside components or pipeline elements subject to an oxygenatmosphere.

2.2.8.4 Products for temporary sealingSpheres or inflatable cylinders used as temporary sealing plugs should preferably be of fluorinated orchlorofluorinated elastomer but may also be of polyurethane or copolymer of isobutylene andisoprene.

2.2.8.5 Sound insulation productsMineral wool (glass wool or rock wool) may be used for insulation in the manufacture of silencers forvents, or for the manufacture of sound insulation casings on component parts or on piping.

The product shall be of low oil content. Residual oil shall not exceed 0.2% by weight and shall beevenly distributed.

2.2.8.6 Other ProductsNo products other than those recommended in 2.2 may be used with oxygen unless prior tests haveproved their safe use.





2.3 Cleaning

2.3.0 General Considerations

2.3.0.1 CleanlinessCleanliness is a fundamental safety requisite for oxygen installations.It is not sufficient for the cleanliness to be effective at a given time : it is necessary to verifycleanliness up to the time of putting into service.

It is not possible to guarantee that installations will be absolutely free from defects and 100% clean. Itis, however, possible by observing the provisions of this code to construct safe installations.However, whatever the level of such selection of components and methods of construction, if theinstallation is not kept clean during operation and maintenance, its reliability will be poor.

In order to achieve acceptable cleanliness it is necessary to define :• contaminate• levels of cleanliness• methods of cl’eaning• methods of protection• procedures for construction• methods of inspection• supervision for the prevention of contamination.Standards with regard to the level of cleanliness and the method of inspection are generally difficult toapply.

It is easy to set theoretical levels which cannot be measured or achieved in practice, however, thiscode gives a basis for guidance. See 2.3.8.

Methods of cleaning are numerous. The purpose of this section is to list the methods that may becontemplated and provide guidance in order to make the best selections.

2.3.0.2 ContaminantsIt is possible to distinguish:• dust, fibres and particles• hydrocarbons and organic residues• water and element of the soil• unusual objectsDuring construction and maintenance, fine dust, particles and fibres can be deposited on componentparts.

Clean, pickled pipes will tend to corrode until they have been assembled resulting in the formation ofa layer of oxide dust. Most of this dust will be removed in the final cleaning. However, there willalways be a tendency for the remaining dust to be released during operation of the installation.

During welding, particles such as residues from grinding, welding slag and grains of weld metal canbe introduced into the pipes.

Hydrocarbons and other organic residues may result from:• oils used during manufacture of the pipes• protective oils and greases• machining oils• lack of precautions and supervision• various deposits during cleaning operations• contamination of oil and grease spillage from plant and machineryWater and elements from the soil (earth, stones, etc) may be introduced into the pipelines duringconstruction if the precautions are not observed. The consequences of water contamination may bethe formation of thick layers of oxides.





In addition to the soil elements mentioned above, unusual objects are occasionally met with, such as :• elements of components (parts, bolts, washers, seals)• welding electrodes• sealing plugs or sachets of dehydrating products• hand tools• oily or dry rags• various site elements or objects• clothing and footwear• miscellaneous objects (cigarettes, etc)

2.3.0.3 Object and nature of cleaningThe presence of impurities such as oil or grease, filings or chips, slag, weld spatter, textile debris,loose residue from pigs, sand and other foreign bodies of all kinds in a system containing oxygen maybe the cause of ignition, explosion or poor mechanical operation. All such foreign bodies shall,therefore, be carefully eliminated.

Cleaning implies the removal of contaminants and residues of cleaning products.

Cleaning procedures generally comprise the following successive phases :• preliminary cleaning• degreasing• cleaning• rinsing• neutralising• drying (where required)• blowing• inspection and control• arrangements for preservationThe choice of cleaning products and procedures, and the choice of repetition of the various operationswill be determined by the nature, amount and location of the impurities and according to thecomponents or installations and their materials of construction. The choice of possible solutions isillustrated in Table X. The main methods are degreasing and cleaning with:

• liquid or vapour solvents• hot water or steam with detergents• acids or aqueous solutions of acids• mechanical devices

2.3.1 Preliminary CleaningBefore proceeding to the cleaning operations proper it is advisable to effect preliminary cleaning inorder to remove the greater part of foreign bodies.

This preliminary cleaning can be effected by tilting blowing, vacuum cleaning, brushing, sweeping,wiping etc.

2.3.2 Degreasing With Solvents

2.3.2.1 ProductsOnly the solvents recommended in 2.2.2 may be used and preference will be given to those listed in2.2.2.3.

The advice given in 2.2.2.1 and 2.2.2.4 to 2.2.2.6 shall also be observed.

2.3.2.2 Degreasing by immersionDegreasing can be effected by immersing and agitating the elementsin a tank containing the solvent.

Agitation of the parts may be effected by an ultra-sonic generator.

Degreasing by immersion is applied essentially to separate parts and components of an assembly.After verification of the cleanliness and dryness the parts shall be carefully packed or pluggedaccording to 2.3.9.





TABLE XTYPICAL PROCEDURES FOR THE CLEANING OF PIPES /

INSTALLATIONS FOR OXYGEN DISTRIBUTION





2.3.2.3 Degreasing by circulationDegreasing can be achieved by forced circulation of a flow of liquid solvent through the componentsor installation. When using this method, care shall be taken to ensure that all the parts to be degreasedare properly reached by the flow of solvent in circulation.

Care shall also be taken to ensure that the equipment used does not comprise any hoses or fittingsmade of rubber, neoprene, polyvinyl chloride or other organic elements that may be dissolved andentrained by the solvent used.

The duration of degreasing by circulation shall be continued until the solvent emerges as clean as thenew solvent put in.

This method is applied mainly to assemblies that cannot be dismantled, to large size elements ofpipelines, to prefabricated circuits and pipework, to sections of pipeline, etc.

After verification of the cleanliness and removal of the cleaning products, all orifices of thecomponents or of the installation must be sealed in accordance with 2.3.9.

2.3.2.4 Degreasing by vaporisationThis method consists of the removal of soluble organic materials from the surfaces of equipment bythe cleaning action of continual condensation of solvent vapours.

This method is applied mainly to the degreasing of large quantities of parts and detached componentsof an assembly or to equipment already assembled where internal geometry allows the easy flow ofcondensate.

Degreasing may be considered complete when the returning condensate is as clean as the new solvent.After verification of the cleanliness dryness, all orifices of the components shall be sealed inaccordance with 2.3.9.

2.3.2.5 Cleanliness of solventsDuring the course of the degreasing processes described in 2.3.2.2 to 2.3.2.4 it is necessary to checkthe cleanliness of the solvent used. For this purpose a sample of fresh solvent shall be kept formaking comparisons

A good reference point may be the discoloration of the solvent compared with fresh solvent.The solvent shall be discarded or regenerated when the degreasing operation no longer results inacceptable surfaces.

2.3.2.6 Elimination of solvent residue sAfter degreasing by solvents in accordance with the processes described in 2.3.2.2 to 2.3.2.4,particular care shall be taken to remove all residual traces of the solvent.

Parts of simple shape and with all their surfaces accessible may be wiped with a clean, dry, lint freecloth or by blowing with dry, oil-free nitrogen or air.

Parts that cannot be reached with a cloth (blind or small diameter holes, screw threads, grooves,corners, etc) shall be cleaned by blowing with dry, oil-free nitrogen or air.

In the case of equipment or installations where the interior is not accessible, solvent residues shall bedrained off through every available opening (tilting the equipment, opening purging orifices, drainholes, etc) and the whole shall be cleaned by blowing with dry, oil-free nitrogen or air until all tracesof solvent residue have been removed.

Solvents containing organic products or grease shall be moved by the vaporisation method.Cleaning may be considered complete when it is no longer possible to detect solvent in the blowinggas at the exit from the equipment or installation.

There are in existence halogen leakage detectors which make it possible to determine whether allsolvent residues have been eliminated.





2.3.3 Degreasing with Water Solutions or Steam

2.3.3.1 MethodsWater or steam is given solvent properties by the addition of detergents or alkaline products such ascarbonate of soda (Na2CO3).

Hot water is preferred to cold water for application of the solution.• by spraying the solution or steam at pressure against the surfaces to be degreased.• by high speed circulation of solution inside the installations to be degreased.• by immersion and agitation in the solution of the elements to be degreased.

2.3.3.2 ApplicationsThe degreasing methods using water solutions or steam may be used in certain cases as preliminarydegreasing, e.g. before pickling operations (see 2.3.4).

These methods are not recommended for the final degreasing of pipelines for the following reasons:• good degreasing is often difficult to obtain• the drying operations are very long and rarely efficient in the case of pipelines.

2.3.4 Treatment with Acid Products

2.3.4.1 Aims and effects of this treatmentAccording to the products used, cleaning with acid is used in the following applications:• Chemical pickling• Temporary anti-corrosion protection for certain materials such as carbon steels.

2.3.4.2 ProductsThe products used depend upon the nature of the metal to be cleaned.

They shall be selected and used in accordance with the recommendations in 2.2.3.

2.3.4.3 MethodsWhen required, this treatment will be preceded by degreasing according to the recommendations in2.3.2 or 2.3.3.

According to the shape and size of the parts or elements to be treated, one of the following methodsmay be employed:• immersion in a tank containing the product• Complete filling of the element with the product. This may be applied to pipeline elements or

large vessels.• Forced circulation of the products inside the elements. This method is applied to tubular

components treated in series or to sections of pipeline. Care shall be taken to ensure that theproduct wets all the inside surfaces to be treated.

2.3.4.4 Chemical picklingChemical pickling by means of aqueous solutions of acids such as sulphuric or hydrochloric acid isapplied to vessels, pipes, or prefabricated elements made of carbon or low alloy steel.

It removes rust, scale and certain protective coatings.

This pickling may be effected by one of the methods indicated in 2.3.4.3.The operation shall be completed by rinsing with a neutralising product or with running water untilthe pH value of the rinsing water at the outlet approaches that of the rinsing water at the inlet.

Pickling bares the metal of the surfaces treated and thus favours its corrosion by contact withmoisture. This operation shall therefore, be followed by an anticorrosion protection treatment inaccordance with 2.3.4.5.

2.3.4.5 Phosphating and passivationThese are treatments to retard the corrosion of surfaces that have been pickled and are applied tocomponents, pipes, vessels etc., of carbon or low alloy steel.

The operations of phosphating and passivation can be done in accordance with one of the methodsindicated in 2.3.4.3.





After passivation the elements shall be drained and dried either by wiping with a clean, lint free clothor by blowing with dry, oil-free nitrogen or air.

TABI.E XI

TYPICAL EXAMPLE OF DECREASING AND CLEANING TREATMENTSOPERATION PRODUCT TEMPERATURE

OF PRODUCTin °C

DURATION OFOPERATION inminutes

PROCEDURE

LIQUID

Chlorinated

solvent (1)

according to

2.2

ambient 10 to 15

Deg

reas

ing

by Alkali

bath

15% aqueous

solution of

Na2CO2 Plus

0.5% detergent

70° to 80° 30 to 40

Immersion

or

circulation

Rinsing running water ambient until initial

pH is reached

circulation

Chemical pickling 10% aqueoussolution ofsulphuric acid

60° to 70° 60 to 90 Immersion orcirculation

Rinsing Running water Ambient Until initialpH is reached

Circulation

Phosphating Aqueoussolution ofphosphoric acid(concentrationacc. Tomanufacturer’sinstruction)

70° to 80° 20

Passivation Aqueoussolution ofcopper,chromiumsodium etc salts(concentrationacc. Tomanufacturer’sinstructions) M

ay a

lso

be d

one

wit

h a

com

posi

te p

rodu

ct

70°

Dur

atio

n ac

c. T

o te

mpe

ratu

re o

f pro

duct

(see

man

ufac

ture

r’s

inst

ruct

ions

)

15

Immersion orcirculation

Drying Dry, oilfree

nitrogen or air

ambient Until

completely dry

blowing

(1) To be followed by drying operation (not rinsing) before continuing with next operation.

Surfaces treated in this way have a uniform greyish colour, occasionally with some reddish-brownlights due to deposits of salts of the passivation products. Any blackish deposit forming extrathickness and slightly sticky to touch, shows that draining after phosphating and passivation has beenincomplete.

Whitish surfaces with a tendency to be floury indicate incomplete drying.If elements treated in this manner are not used immediately, they shall be sealed or packed accordingto the recommendations in 2.3.9.





2.3.4.6 Duration of treatmentsThe duration of treatments of pickling, phosphating, etc., varies according to the state of the surfacesto be treated, the temperature, concentration and nature of the products used.

It is advisable to follow the instructions supplied by the manufacturers of the products.

Table XI gives an example of the application of these treatments

2.3.5 Mechanical Cleaning

2.3.5.1 Processes and applicationsMechanical cleaning is generally used as a means of preliminary cleaning but some processes such assandblasting can be used as a complete cleaning process.

Cleaning can be carried out by blasting (sanding, shot-blasting) by metallic brushing and scraping, bygrinding, etc. This cleaning may be done manually or with the aid of more sophisticated equipment,according to the shape, number and size of the components to be cleaned.

2.3.5.2 Products and equipmentThe products and equipment to be used are those recommended in 2.2.4.

2.3.5.3 Manual methodsThe accessible surfaces of parts and components of small size can be brushed to remove solidcontaminants, dust, etc. Accessible welds can be ground and brushed to remove slag or excess weldmetal etc.

2.3.5.4 Sand and shot-blastingSand and shot-blasting are used to remove scale, rust, varnishes, paints, manufacturing lubricants andother foreign bodies.

These operations may be applied to pipes, prefabricated pipework, components and vessels.Cleaning by sandblasting is effective for the removal of certain bituminous varbishes deposited on theinside of elements of pipelines such as commercial bends, caps or tees. Chemical agents may beincapable of dissolving these bituminous varnishes.

For the internal sandblasting of pipes or vessels it is recommended that a quality equivalent to thescale N9, rugotest No.3. of 1.S.O. 2632 be achieved.

The abrasives and propellant gases used for this work shall be those recommended in 2.2.4.1 and2.2.4.2.

Sand or shot~blasting may be followed by anticorrosion protection according to 2.3.4.5.

2.3.5.5 Passage of cleaning pigsPreliminary cleaning of a pipeline or section of pipeline may be effected by means of cleaning pigs inaccordance with the recommendations of 2.2.4.4. The propellant gas shall be clean, dry, oil-freenitrogen or air.

The flow should be regulated so as to obtain a steady advance rate of the pig in the order of 2 to 3 m/s.Several successive passages of the pig shall be effected until it is found by visual observation that itno longer brings out solid bodies, particles and excessive dust at its point of exit.

Only one pig at a time shall be introduced into the pipeline





2.3.5.6 Blowing out the pipelinesBlowing out of the pipelines shall be done with clean, dry, oil-free nitrogen or air in accordance withthe recommendations of 2.2.5.

The pressure of the blowing gas may be low (close to atmospheric pressure) but its velocity shall behigh. In order to be effective, i.e. to remove most of the residual dust and particles, the blowing gasshall have a minimum velocity of the order of 25 to 30 m/s. To obtain these velocities in all parts ofthe pipeline to be cleaned, several methods may be used:

a) A turbocompressor delivery directly into the pipeline for cleaning at a pressure of several bar.b) Filling a previously cleaned section of pipeline of approximately the same length as the section

to be cleaned with the gas. The pressure of this gas shall be high enough to give the velocitiesrequired when it is discharged into the section to be cleaned.

This method requires previous strength testing of the pipeline serving as storage vessel.c) In the case of small auxiliary pipelines of small diameter it is possible to use nitrogen supplied

direct from mobile gas containers such as cylinders, bundles, etc.

The duration of blowing depends upon the length of pipeline to be cleaned, the velocity of the gas, theamount of dust present, etc. Blowing should continue until the outgoing gas is free from particles andexcessive dust at its point of exit.

Temporary equipment and connections used for blowing shall be previously cleaned and degreased inthe same way as equipment intended for use with oxygen.

2.3.5.7 Vacuum cleaningVacuum cleaning can also be used either alone or in conjunction with other mechanical cleaningprocesses.

2.3.6 Cleaning of Components and Equipment

2.3.6.1 Cleaning of componentsParts and components made of carbon or low alloy steel shall be subjected to the following treatmentsand in the order listed:

a) Any necessary prescribed strength tests

b) Degreasing according to the recommendations of 2.3.2 or 2.3.3.c) If necessary, chemical pickling according to 2.3.4.4 or mechanical cleaning according to

2.3.5.4.

d) If necessary, anticorrosion protection treatment according to 2.3.4.5.The nonferrous parts of components or items of equipment shall also be degreased in accordance withthe recommendations of 2.3.2.

In the case of non-metallic parts care shall be taken to select a solvent that does not attack the objectto be cleaned.

Assembly of the components shall then be effected in a clean environment by personnel dulyinformed of the cleanliness demanded.

Care shall be taken not to introduce any foreign body or impurity into the component duringassembly.

If the component is lubricated it shall be effected in the course of assembly and shall comply with therecommendations of 2.2.1 and 3.6.0.

Certain design of components require degreasing of the complete assembly in accordance with 2.3.2.After assembly, equipment or components shall be sealed or packed in accordance with therecommendations of 2.3.9.





2.3.6.2 Cleaning prefabricated pipeworkCarbon steel pipework designed to connect the various parts of an installation, prefabricated in thefactory or fabricated on site, shall be subjected to the following treatment and in the order listed:

a) Any necessary prescribed strength tests.

b) Degreasing according to the recommendations of 2.3.2 or 2.3.3.c) If necessary, chemical pickling according to 2.3.4.4 or mechanical cleaning according to

2.3.5.4.

d) If necessary, anticorrosion protection treatment according to 2.3.4.5.If these elements are not fitted immediately they shall be sealed according to the recommendations of2.3.9.

2.3.6.3 Cleaning the pipesCarbon steel pipes intended for the construction of pipelines may, after the prescribed strength tests,be treated at the factory by one of the following methods:

a) Mechanical cleaning (sandblasting) according to 2.3.5.4 followed by blowing with clean, dry,oil-free nitrogen or air.

b) Mechanical cleaning (sandblasting) according to 2.3.5.4 followed after b lowing byanticorrosion protection treatment according to 2.3.4.5.

c) Degreasing according to section 2.3.2 or 2.3.3 followed by chemical pickling and anticorrosionprotection treatment according to 2.3.4.

In every case, the pipes shall, after inspection and verification of their cleanliness according to 2.3.8,be carefully sealed according to the recommendations of 2.3.9.

If the pipes afterwards undergo an external coating operation care shall be taken to ensure that thesealing of the pipe cannot possibly be perforated or removed in the course of this work.

Stainless steel and copper alloy pipes shall be decreased according to the recommendations of 2.3.2and, after inspection and verification according to 2.3.8, they shall be carefully sealed according to2.3.9.

2.3.7 Cleaning the Pipelines

2.3.7.1 MethodsThe method of cleaning a pipeline depends essentially upon the method of construction. From thepoint of view of cleaning there are two main methods of constructing a pipeline to be considered :

a) Construction of the pipeline using unclean pipes. Laying shall then be followed by extensivecleaning see 2.3.7.2.

b) Construction of the pipeline using clean pipes treated according to 2.3.6.3, care being taken toavoid introduction into the pipeline during laying of any foreign bodies or impurities. See2.3.7.3.

The first method makes installation easier but final cleaning will be onerous and its efficiency difficultto control.

The second method, which is preferable, requires more carefully controlled laying but final cleaning iseasier.

The pipeline shall be cleaned before components and equipment are fitted. In the event of pre-assembly of components into the pipeline, they must be removed before the cleaning operations.





2.3.7.2 Pipelines constructed with unclean pipesA pipeline constructed with unclean pipes requires cleaning with very special care and attention.Such operations will be difficult to control since effective inspection is not possible. Cleaning may beeffected, after the passing of a cleaning pig (see 2.3.5.5) in the following ways:

a) By successive filling and circulation, by means of pumps supply and evacuation tanks, usingdegreasing, pickling, rinsing, phosphating and passivating products, see 2.3.4.

b) By circulation of a ‘train’ of the above products, separated from each other by pistons orballoons and propelled by the pressure of clean, dry, oil-free nitrogen or air.

Both methods require subsequent drying “hat is difficult to achieve. This may be successfullyachieved in certain special cases where large quantities of blowing gas are available for drying thepipeline (e.g. availability of a turbocompressor).

c) By sand blasting of the line using clean, dry, oil-free air or nitrogen with sand on the sectionsof 3 to 5 kilometres. This operation shall be followed by vigorous blowing to remove all sandand dust. See 2.3.5.4.

2.3.7.3 Pipelines constructed-with clean pipesIf the pipeline has been constructed:• with pipes cleaned in accordance with 2.3.6.3 delivered sealed on site ;• and if during laying every precaution has been taken according to 4.3.13 to prevent the

introduction of foreign bodies and other impurities into the pipeline ;one of the following methods of final cleaning may be used :a) passage of pigs followed by high velocity blowing out with clean, dry oil-free nitrogen or air.

See 2.3.5.5 and 2.3.5.6.

b) blowing out with clean, dry, oil-free nitrogen or air. See 2.3.5.6.

2.3.8 Level of Cleanliness and Control

2.3.8.1 GeneralContamination by dust, fibres and particles can be evaluated by counting the quantity (mass ornumber) per unit volume for a fluid or per unit area for a system. These particles can then beclassified as a function of their dimensions and of their nature.

Oily or organic deposits are measured in mass of deposit per unit area (mg/m2).Sophisticated methods of control can be applied during trials or tests, e.g. to determine the efficiencyof a cleaning operation.

on the other hand these methods are not practical in the construction workshop or on site; theirefficiency is doubtful. We shall indicate in the following sections some levels of contamination andpractical means of control to be employed.

2.3.8.2 Control of cleanlinessControl of the absence of foreign bodies, particles filings, dust, textile waste, etc., during constructionshall be effected by visual inspection with white light.

Cleanliness shall be considered adequate if no trace of impurities can be detected visually.This method shall be applied to all surfaces accessible to vision, possibly with the help of a set ofmirrors.

Where a completed pipeline cannot be checked visually, cleanliness can be verified by absence ofparticles and dust during blowing operation. See 2.3.5.6.





2.3.8.3 Direct control of degreasingVisual inspection according to 2.3.8.2 is not adequate for verification of the absence of residues of oilor grease.

One or both of the direct methods below may be used:-a) Wipe test, lightly rubbing highly porous paper (e.g. cleansing paper) over the surface to be

controlled. No permanent stain resulting from the presence of oil or grease on the surface shallshow on this paper.

b) Inspection of the surfaces to be controlled by ultra-violet lamp producing radiation of awavelength between 2500 and 4000Å. No fluorescence betraying the presence of oil or greaseor textile fibres is acceptable.

NB: We draw the reader’s attention to the fact that some oils and greases are not fluorescent underultra-violet light.

2.3.8.4 Indirect control of degreasingIn certain cases it will be possible to use indirect methods such as ‘solvent extraction’. This methodconsists in rinsing the inside of the cleaned equipment with a clean solvent and evaporating arepresentative sample of the solvent used, then comparing the residues thus obtained with thoseobtained from the same quantity of clean solvent. “The difference in weight between these tworesidues and the amount of solvent used to make it possible to calculate the quantity of impuritiesextracted per square metre of surface cleaned.”

In current technical literature figures of permissible hydrocarbons uniformally distributed varybetween 50 to 1000 mg/m2 depending upon the type of hydrocarbons.

This control by solvent extraction is restricted by the difficulty in the solvent reaching and dissolvingthe impurities present.

This method is only valid for defining the effectiveness of a cleaning process. It is not generallypractical for the systematic control of cleanliness in a manufacturing workshop or on a work site.

2.3.8.5 Methods of inspectionThe criteria for cleanliness and control shall be specified between the manufacturer and buyer.The buyer shall from the start and periodically afterwards visit the premises of the manufacturer andverify the methods of control and achievement of cleanliness specified.

The manufacturer shall make a record indicating for each item of equipment:• its designation and serial number• the processes used for,cleaning and inspection• the dates and results of inspection

2.3.9 Preservation of the Cleanliness Obtained

2.3.9.1 GeneralAfter cleaning and inspection, the elements or components shall be protected from any contaminationor deterioration during the time of storage and transport until they are fitted or put into service in theinstallations. Protection shall be assured against exposure to adverse weather and moisture.

Packaging and sealing used for this purpose shall :• be strong, clean and free from oil or grease• be dust tight and waterproof

2.3.9.2 Packaging of small itemsSmall items of equipment and spare parts shall be packed in sealed plastic bags. If these small itemscomprise orifices, these should first be sealed by means of metal, plastic or rubber plugs.

Sealing with adhesive tape shall be avoided.

Packing under vacuum is permitted.





2.3.9.3 Sealing of components and sections of pipeworkThe opening of components and prefabricated pipework shall be sealed by means of blind flanges,metal, plastic or plywood covers

Small orifices shall be sealed by means of metal, plastic or rubber plugs.

2.3.9.4 Sealing pipesThe pipes or sections of pipework without flanges, cleaned in accordance with 2.3.6.3 shall be sealedby means of plastic plugs or caps.

These may :• have a conical part fitted by insertion (plug)• have an external collar securely held (Cap)• have force fit outer and inner lips, clamped and held by strong adhesive tape (see fig.12). For

typical example.

2.3.9.5 Drying agentsIn order to adsorb moisture inside the packed or sealed items of equipment or components, dryingagents should be used in accordance with the recommendations of 2.2.6.

2.3.9.6 InertingEquipment and components of large internal volume may be protected from internal corrosion bybeing inerted with a nitrogen atmosphere.

2.3.9.7 LabellingParts and packages shall carry inscriptions such as: -• CLEANED FOR OXYGEN SERVICE• OXYGEN - NO OIL OR GREASE• DO NOT OPEN BEFORE TAKING INTO SERVICE• INERTED WITH NITROGEN



Part 3 : Equipment


The Transportation and Distribution of Oxygen by PipelinePart 3 : Equipment

IGC 13/82/E









Part 3 : Equipment


SECTION 3 : EQUIPMENT.................................................................................................................................................6

3.1 GENERAL ....................................................................................................................................................................63.1.1 Specifications.......................................................................................................................................................63.1.2 Invitations to Tender and Purchase Orders....................................................................................................63.1.3 Manufacture .........................................................................................................................................................63.1.4 Inspection and Acceptance ................................................................................................................................6

3.2 PIPES............................................................................................................................................................................73.2.0 General Considerations......................................................................................................................................7

3.2.0.1 Choice of materials ........................................................................................................................................73.2.0.2 Use of carbon steel pipes ...............................................................................................................................73.2.0.3 Use of copper or copper alloy pipes ..............................................................................................................73.2.0.4 Use of stainless steel pipes .............................................................................................................................73.2.0.5 Thickness of pipes ..........................................................................................................................................7

3.2.1 Carbon and Low Alloy Steel Pipes...................................................................................................................73.2.1.1 General provisions .........................................................................................................................................73.2.1.2 Method of Manufacture .................................................................................................................................73.2.1.3 Appearance and dimensions ..........................................................................................................................83.2.1.4 Pipe ends ........................................................................................................................................................83.2.1.5 Inspection of materials and pipes ...................................................................................................................83.2.1.6 Pressure test at the manufacturers ..................................................................................................................83.2.1.7 Internal treatment and sealing ........................................................................................................................83.2.1.8 External coating and wrapping ......................................................................................................................83.2.1.9 Markings ........................................................................................................................................................83.2.1.10 Handling.........................................................................................................................................................9

3.2.2 Copper Pipes........................................................................................................................................................93.2.2.1 General provisions .........................................................................................................................................93.2.2.2 Manufacture ...................................................................................................................................................93.2.2.3 Appearance and dimensions ..........................................................................................................................93.2.2.4 Pipe ends ........................................................................................................................................................93.2.2.5 Inspection of pipes .........................................................................................................................................93.2.2.6 Pressure test at the manufacturers ..................................................................................................................93.2.2.7 Internal treatment and sealing ........................................................................................................................9

3.2.3 Copper Alloy Pipes..............................................................................................................................................93.2.4 Stainless Steel Pipes............................................................................................................................................9

3.2.4.1 General provisions .........................................................................................................................................93.2.4.2 Methods of manufacture ..............................................................................................................................103.2.4.3 Appearance and dimensions ........................................................................................................................103.2.4.4 Pipe ends ......................................................................................................................................................103.2.4.5 Inspection of materials and pipes .................................................................................................................103.2.4.6 Pressure test at the Manufacturers ...............................................................................................................103.2.4.7 Internal treatment and sealing ......................................................................................................................103.2.4.8 Markings ......................................................................................................................................................103.2.4.9 Handling.......................................................................................................................................................11

3.3 STANDARD PIPE FITTINGS......................................................................................................................................113.3.0 General Considerations................................................................................................................................... 11

3.3.0.1 Definitions....................................................................................................................................................113.3.0.2 Materials .......................................................................................................................................................113.3.0.3 Thickness .....................................................................................................................................................113.3. 0.4 Ends..............................................................................................................................................................113.3.0.5 Appearance and dimensions ........................................................................................................................113.3.0.6 Tests .............................................................................................................................................................113.3.0.7 Internal treatment.........................................................................................................................................113.3.0.8 Inspection .....................................................................................................................................................113.3.0.9 Markings ......................................................................................................................................................11

3.3.1 Bends................................................................................................................................................................... 123.3.1.0 General.........................................................................................................................................................12

3.3.2 Reducers............................................................................................................................................................. 123.3.3 Pipe Caps or Dished Ends.............................................................................................................................. 123.3.4 Tees and Other Branches ................................................................................................................................ 12

3.3.4.0 General.........................................................................................................................................................123.3.4.1 Forged tees ...................................................................................................................................................12



Part 3 : Equipment


3.3.4.2 Reinforced branches .....................................................................................................................................133.3.4.3 Fabricated Tees ............................................................................................................................................13

3.4 ASSEMBLY COMPONENTS......................................................................................................................................133.4.0 General Considerations................................................................................................................................... 13

3.4.0.1 Definitions....................................................................................................................................................133.4.0.2 Gaskets and jointing materials .....................................................................................................................133.4.0.3 Leak-tightness ..............................................................................................................................................133.4.0.4 Mechanical strength .....................................................................................................................................133.4.0.5 Cleanliness ...................................................................................................................................................13

3.4.1 Flanges............................................................................................................................................................... 133.4.1.0 General.........................................................................................................................................................133.4.1.1 Standarisation...............................................................................................................................................133.4.1.2 Flange selection............................................................................................................................................143.4.1.3 Materials for weldneck flanges ....................................................................................................................143.4.1.4 Materials for other types of flanges .............................................................................................................143.4.1.5 Conditions of use .........................................................................................................................................143.4.1.6 Flange faces .................................................................................................................................................143.4.1.7 Inspection .....................................................................................................................................................143.4.1.8 Nuts and bolts ..............................................................................................................................................143.4.1.9 Bonding ........................................................................................................................................................14

3.4.2 Couplings........................................................................................................................................................... 153.4.2.0 General.........................................................................................................................................................153.4.2.1 Materials .......................................................................................................................................................153.4.2.2 Leak-tightness of screw threads...................................................................................................................153.4.2.3 Leak-tightness of couplings .........................................................................................................................153.4.2.4 Couplings with conical or spherical contact surface....................................................................................153.4.2.5 Flared tube couplings ...................................................................................................................................163.4.2.6 Olive couplings ............................................................................................................................................163.4.2.7 Flat seal or O-ring seal couplings ................................................................................................................163.4.2.8 Connection of couplings to pipework..........................................................................................................16

3.5 MISCELLANEOUS ACCESSORIES............................................................................................................................163.5.1 Flexible Pipes.................................................................................................................................................... 16

3.5.1.0 General.........................................................................................................................................................163.5.1.1 Possible uses ................................................................................................................................................163.5.1.2 Materials .......................................................................................................................................................173.5.1.3 Inspection and testing...................................................................................................................................17

3.5.2 Expansion Elements ......................................................................................................................................... 173.5.2.0 General.........................................................................................................................................................173.5.2.1 Use of expansion elements ...........................................................................................................................173.5.2.2 Expansion Loops..........................................................................................................................................173.5.2.3 Expansion Bellows .......................................................................................................................................18

3.5.3 Elements to Reduce Noise............................................................................................................................... 183.5.3.1 Silencers .......................................................................................................................................................183.5.3.2 Sound insulation coverings ..........................................................................................................................18

3.5.4 Other Accessories ............................................................................................................................................. 183.6 COMPONENTS..........................................................................................................................................................18

3.6.0 General Criteria for the Design and Construction of Components......................................................... 183.6.0.1 Compliance of components with this code ..................................................................................................183.6.0.2 Choice of safety factors ...............................................................................................................................183.6.0.3 Recommended materials ..............................................................................................................................193.6.0.4 Non-metallic materials .................................................................................................................................193.6.0.5 Metallic parts facing the gas flow................................................................................................................193.6.0.6 Components subjected to a differential pressure .........................................................................................193.6.0.7 Electrical potential - conductor....................................................................................................................193.6.0.8 Electrical devices .........................................................................................................................................193.6.0.9 Hydrostatic testing .......................................................................................................................................193.6.0.10 Internal surface treatment.............................................................................................................................193.6.0.11 Internal Cleanliness......................................................................................................................................193.6.0.12 Degreasing ...................................................................................................................................................193.6.0.13 Lubrication ...................................................................................................................................................193.6.0.14 Connections..................................................................................................................................................203.6.0.15 Sealing and packing .....................................................................................................................................20

3.6.1 Stop Valves......................................................................................................................................................... 203.6.1.1 Compliance of components with this code ..................................................................................................20



Part 3 : Equipment


3.6.1.2 Use of valve .................................................................................................................................................203.6.1.3 Internal profiles ............................................................................................................................................203.6.1.4 Leak tightness ..............................................................................................................................................203.6.1.5 Non-metallic sealing ....................................................................................................................................203.6.1.6 Equalising valves .........................................................................................................................................203.6.1.7 Quarter turn valves .......................................................................................................................................203.6.1.8 Manual operation .........................................................................................................................................203.6.1.9 Lubrication of manual operating devices .....................................................................................................213.6.1.10 Position indicator.........................................................................................................................................213.6.1.11 Operation of manual valves .........................................................................................................................213.6.1.12 Servomotors .................................................................................................................................................213.6.1.13 Oxygen operated servomotors .....................................................................................................................213.6.1.14 Nitrogen or air operated servomotors ..........................................................................................................213.6.1.15 Electrically operated servomotors ................................................................................................................213.6.1.16 Hydraulically operated servomotors ............................................................................................................213.6.1.17 Emergency control .......................................................................................................................................213.6.1.18 Fail safe device.............................................................................................................................................223.6.1.19 Small manually operated valves ..................................................................................................................223.6.1.20 Small pneumatically operated valves ...........................................................................................................223.6.1.21 Electrically operated valves .........................................................................................................................223.6.1.22 Manual throttling valve ................................................................................................................................22

3.6.2 Automatic Control Valves ............................................................................................................................... 223.6.2.1 Definition .....................................................................................................................................................223.6.2.2 Compliance with this code ...........................................................................................................................233.6.2.3 Type of valve ...............................................................................................................................................233.6.2.4 Materials of construction .............................................................................................................................233.6.2.5 Non leaktight valve installation ...................................................................................................................233.6.2.6 Standby manual operation............................................................................................................................233.6.2.7 Fail safe device.............................................................................................................................................23

3.6.3 Non-Return Valves ........................................................................................................................................... 233.6.3.1 Definition .....................................................................................................................................................233.6.3.2 Compliance with this code ...........................................................................................................................233.6.3.3 Type of valves ..............................................................................................................................................233.6.3.4 Leak-tightness ..............................................................................................................................................233.6.3.5 Locking device .............................................................................................................................................233.6.3.6 Small non-return valves ...............................................................................................................................24

3.6.4 Pressure Reducing Valves............................................................................................................................... 243.6.4.1 Definition .....................................................................................................................................................243.6.4.2 Compliance with this code ...........................................................................................................................243.6.4.3 Loading gas ..................................................................................................................................................243.6.4.4 Fail safe device.............................................................................................................................................243.6.4.5 Balanced valves ...........................................................................................................................................243.6.4.6 Leak tightness ..............................................................................................................................................243.6.4.7 Safety shut-off..............................................................................................................................................24

3.6.5 Filters.................................................................................................................................................................. 243.6.5.1 Function .......................................................................................................................................................243.6.5.2 Recommended materials ..............................................................................................................................253.6.5.3 Filter elements made from non-metallic materials ......................................................................................253.6.5.4 Filtration threshold .......................................................................................................................................253.6.5.5 Strength of filter elements ............................................................................................................................253.6.5.6 Instrumentation filters ..................................................................................................................................25

3.6.6 Flowmeters and Meters ................................................................................................................................... 253.6.6.1 Function .......................................................................................................................................................253.6.6.2 Main types ....................................................................................................................................................253.6.6.3 Selection.......................................................................................................................................................263.6.6.4 Volume correcting devices ..........................................................................................................................263.6.6.5 Compliance with this code ...........................................................................................................................263.6.6.6 Lubrication ...................................................................................................................................................263.6.6.7 Bellows type.................................................................................................................................................263.6.6.8 Remote indication ........................................................................................................................................263.6.6.9 Auxiliaries ....................................................................................................................................................263.6.6.10 Overspeed protection ...................................................................................................................................26

3.6.7 Safety Valves - Bursting Discs........................................................................................................................ 273.6.7.1 Function .......................................................................................................................................................273.6.7.2 Compliance with this code ...........................................................................................................................27



Part 3 : Equipment


3.6.7.3 Operating mode............................................................................................................................................273.6.7.4 Lifting pressure ............................................................................................................................................273.6.7.5 Bursting pressure ..........................................................................................................................................273.6.7.6 Multiple safety devices ................................................................................................................................273.6.7.7 Duplication of safety devices .......................................................................................................................273.6.7.8 Misadjustment ..............................................................................................................................................273.6.7.9 Safety valve materials ..................................................................................................................................273.6.7.10 Disc material ................................................................................................................................................273.6.7.11 Leak tightness of safety valves ....................................................................................................................273.6.7.12 Pilot devices .................................................................................................................................................273.6.7.13 Vent pipes ....................................................................................................................................................273.6.7.14 Periodic inspection .......................................................................................................................................273.6.7.15 Periodic replacement of disc........................................................................................................................273.6.7.16 Small safety valves ......................................................................................................................................28

3.6.8 Insulating Joints................................................................................................................................................ 283.6.8.1 Definition .....................................................................................................................................................283.6.8.2 Function .......................................................................................................................................................283.6.8.3 Ignition risks ................................................................................................................................................283.6.8.4 Compliance with this code ...........................................................................................................................283.6.8.5 Material in contact with oxygen...................................................................................................................283.6.8.6 Material not in contact with oxygen ............................................................................................................283.6.8.7 Insulating capability .....................................................................................................................................283.6.8.8 Design and installation.................................................................................................................................28

3.6.9 Other Components............................................................................................................................................ 293.6.9.1 General criteria.............................................................................................................................................293.6.9.2 Flow limiters ................................................................................................................................................293.6.9.3 Pressure sensors and indicators ....................................................................................................................293.6.9.4 Pneumatic control device .............................................................................................................................293.6.9.5 Temperature sensors and indicators .............................................................................................................293.6.9.6 Miscellaneous items of equipment...............................................................................................................30



Part 3 : Equipment


SECTION 3 : EQUIPMENT

3.1 GeneralThis section deals with recommendations concerning the design and manufacture of items ofequipment and components for oxygen systems.

The recommendations represent minimum requirements for the safety of oxygen systems and areintended for guidance in the preparation of fully detailed specifications by users.

3.1.1 SpecificationsIt is desirable for users to draw up specifications for their invitations to tender and for purchasing.The form of these document shall be related to their purpose.

The documents may include requirements such as:• additional specifications• the type of manufacture• quality• cleaning procedures• dimensions and tolerances• inspection• etc

3.1.2 Invitations to Tender and Purchase OrdersWhenever an invitation to tender is issued or an order given for equipment destined for use withoxygen, it shall specify that the equipment is intended for use with oxygen, indicating the conditionsof use, (e.g. pressure, temperature, etc) and the requirements for cleanliness and degreasing.

A certificate of conformity may be required of the supplier. The wording of this certificate shall bedrafted at the time of ordering.

3.1.3 ManufactureThe manufacture of items of equipment and components shall comply with the recommendations ofthis Code and relevant Standards, and users specifications.

The final assembly of components, sub-assemblies or unit parts, previously degreased and cleaned inaccordance with the recommendations of 2.3.2 or 2.3.3 shall be carried out in a clean place speciallyprovided for the purpose, by personnel duly instructed concerning the cleanliness demanded inaccordance with 2.3.6 and 2.3.9.

3.1.4 Inspection and AcceptanceIn spite of the recommendations and specifications made, items of equipment or components intendedfor use with oxygen may not conform completely to the conditions indicated in the order. Deviationssuch as:• the use of non-recommended materials or lubricants• inadequate cleaning• nonobservance of dimension or tolerance errors• various irregularitiesmay occur.

Inspection of equipment before its installation and commissioning is, therefore, mandatory.It is preferable for the user to carry out inspection on the supplier’s premises before the equipment isdespatched.

The equipment shall be plugged or packed according to the recommendations of 2.3.9 and 3.6.0.15before despatch.

Plugs or packaging shall only be removed at the last moment before assembly of the equipment in theinstallation.



Part 3 : Equipment


3.2 Pipes


3.2.0.1 Choice of materialsPipes intended for the construction of pipelines above or below ground shall be made from one of themetals recommended in section 2.1.1.

The metals most frequently used are:• carbon steel• copper and copper alloys• stainless steelPipes of nickel or nickel alloy may be used for special applications.The use of rigid pipes of non-metallic material is forbidden for oxygen. The case of hoses is dealtwith in 3.5.1.

3.2.0.2 Use of carbon steel pipesCarbon steel pipes are generally used for delivery and distribution pipelines above or below ground,and for the construction of pipework fittings. Carbon steel pipe shall not be used for vents and purgesto atmosphere.

3.2.0.3 Use of copper or copper alloy pipesPreference is given to copper and its alloys by reason of their resistance to oxidation and ignition, aswell as of their ease of cleaning.

3.2.0.4 Use of stainless steel pipesStainless steel is characterised by greater mechanical strength than copper but its behaviour in theevent of ignition is less satisfactory (see 2.1.1.1).

Stainless steel pipes may be used for delivery and distribution pipelines both above and below groundand for the construction of the pipework elements of valve or delivery stations and instrument piping.

3.2.0.5 Thickness of pipesThe pipe thickness is determined according to the material, the size of the pipe and the design pressureselected, in accordance with the national standards and regulations in force in the country where thepipes are to be installed (see 4.1.4).

3.2.1 Carbon and Low Alloy Steel Pipes

3.2.1.1 General provisionsCarbon and low alloy steel pipes shall comply with the national standards and regulations in force inthe country for which they are intended and shall conform to the buyer’s specification.

Generally speaking, the regulations, standards and specifications determine the acceptable limit ofconditions and characteristics.

3.2.1.2 Method of ManufacturePipes may be manufactured by different methods :• seamless• welded longitudinally• welded helicoidallySeamless pipes made by hot rolling shall be of one piece and no joining of short pieces of pipe will betolerated. Any repairs by welding is prohibited.

Welded pipes shall be welded without overlap along the line of contact of the edges, which may belinear or helicoidal. The edges to be welded shall be sound, free from scale and rust and dry. Theyshall be correctly formed and aligned, without any offset.

The welding process will be agreed between vendor and user.



Part 3 : Equipment


3.2.1.3 Appearance and dimensionsPipes shall be straight and cylindrical in shape. They shall present a uniform surface. Theirdimensions (diameters and thicknesses), theoretical mass, tolerances, permissible irregularities ordefects of structure and appearance shall comply with the national standards in force.

3.2.1.4 Pipe endsThe ends of pipes shall be trimmed and prepared at right angles to their axis. Edges shall be clean andfree from burrs.

The ends shall be chamfered for butt welding.

No visible lamination will be tolerated.In the case of welded pipes, it may be advisable for the inside pipe welds to be bevel ground at eachend for a distance of at least 50mm before delivery.

3.2.1.5 Inspection of materials and pipesThe inspection of materials and pipes at the factory shall be carried out to ascertain confirmity withthe users code, specification or national regulations.

3.2.1.6 Pressure test at the manufacturersBefore applying any coating or wrapping, all pipes shall be hydraulically pressure tested.The test pressure shall not exceed the maximum pressure compatible with the stresses permitted bythe regulations or standards.

The pressure shall be maintained for at least 15 seconds. No leakage or permanent deformation shalloccur.

Test pressures are defined in 4.1.9.

3.2.1.7 Internal treatment and sealingPipes may undergo cleaning treatment according to 2.3.6.3, and will be sealed in accordance with2.3.9.4 to maintain cleanliness, if dessicants are used they shall comply with 2.2.6.

3.2.1.8 External coating and wrappingExternal coating or wrapping shall be made in accordance with the rules of the art under conditions oftemperature and humidity compatible with the nature of the products.

The coating shall have good adhesion, good uniformity and perfect electrical continuity, which shallbe verified by testing with a detector to a minimum of 10,000 volts.

The coating shall be designed to ensure an insulation value in excess of 10,000Ω/m2, measured on theinstalled pipe.

The ends of pipes shall not be coated for a distance of :• 160 to 200 mm for pipes of 2” and 3” nom dia• 250 to 300 mm for pipes of 4” to 10” nom dia• 300 to 350 mm for pipes above 10” nom dia

3.2.1.9 MarkingsThe accepted pipes shall bear clearly visible markings conforming with the users code andspecification or national regulations.

In the absence of the above, the following marking is recommended at a minimum of 100 mm and amaximum of 140 mm from one end of pipe and in such a way that any coat or wrapping does notcover them.

By permanent marking :• the manufacturer’s mark (identifying the factory of manufacture)• the mark of the cast• the year of manufacture• the identification number of the pipe• the required inspection and test marking



Part 3 : Equipment


By stencilling :Where special pipes are procured whose thickness or grade differs from the standard pipes, these shallhave a clearly visible distinctive marking.

No internal marking shall be permitted.

3.2.1.10 HandlingIn the course of transport and handling, all necessary steps shall be taken to prevent damage to pipesand their protective coatings.

3.2.2 Copper Pipes

3.2.2.1 General provisionsCopper pipe shall comply with the national standards and regulations in force in the country where thepipes are to be used, and shall conform to the buyer’s specification.

3.2.2.2 ManufacturePipes shall be solid drawn deoxidized non-arsenical welding grade copper and may be supplied :• In straight lengths, in one of the following conditions, as drawn, (unsuitable for bending or

expanding unless locally annealed), annealed, quarter hard, half hard or hard.• In coils, annealed

3.2.2.3 Appearance and dimensionsPipes shall be straight and cylindrical in shape, Their dimensions (diameter and thickness), theoreticalmass, tolerances, permissible irregularities or defects of structure and appearance shall comply withthe national standards or regulations.

3.2.2.4 Pipe endsThe ends of pipe shall be trimmed and prepared at right angles to their axis. Edges shall be clean andfree from burrs.

3.2.2.5 Inspection of pipesThe inspection of pipes at the manufacturers shall be carried out by a competent person, to ascertainconformity with the users specifications and national standards or regulations.

3.2.2.6 Pressure test at the manufacturersAll pipes shall be hydraulically pressure tested.The test pressure shall not exceed the maximum pressure compatible with the stresses permitted bythe national standards or regulations.

3.2.2.7 Internal treatment and sealingWhen specified by the user, pipes shall undergo cleaning treatment and be sealed in accordance with2.3.6.3 and 2.3.9.4.

3.2.3 Copper Alloy PipesPiping made of copper alloys (e.g. cupro nickel, tin bronze, aluminium bronze) may be used for theconstruction of pipework elements and pipelines where their mechanical and physical characteristicsallow.

Generally the mechanical and physical characteristics of copper or copper alloys vary according totheir composition and shall be specified by the manufacturer for each material.

The use of brass pipes shall be avoided because of their tendency to crack in certain stress conditions(vibration, etc).

3.2.4 Stainless Steel Pipes

3.2.4.1 General provisionsStainless steel pipes shall comply with the National standards and regulations in force in the countryfor which they are intended and shall conform to the buyer’s specification.

Generally speaking, the regulations, standards and specifications determine the acceptable limitconditions and characteristics.



Part 3 : Equipment


3.2.4.2 Methods of manufactureStainless steel pipes may be:• seamless• welded longitudinally• welded helicoidallySeamless pipes made by hot rolling shall be of one piece and no joining of short pieces of pipe will betolerated. Any repairs by welding is prohibited.

Welded pipes shall be welded without overlap along the line of contact of the edges, which may belinear or helicoidal. The edges to be welded shall be sound, free from scale and dry. They shall notcorrectly formed and aligned, without any offset.

The welding process will be agreed between vendor and user.

3.2.4.3 Appearance and dimensionsPipes shall be straight and cylindrical in shape. They shall present a uniform surface. Theirdimensions (diameters and thickness), theoretical mass, tolerances, permissible irregularities ordefects of structure and appearance shall comply with the national standards in force.

3.2.4.4 Pipe endsThe ends of pipes shall be trimmed and prepared at right angles to their axis. Edges shall be clean andfree from burrs.

The ends shall be chamfered for butt welding.

3.2.4.5 Inspection of materials and pipesThe inspection of materials and pipes at the factory shall be carried out to ascertain conformity withthe users code, specification or national regulations.

3.2.4.6 Pressure test at the ManufacturersAll pipes shall be hydraulically pressure tested before applying any coating or wrapping.The test pressure shall not exceed the maximum pressure compatible with the stresses permitted bythe regulations or standards.

The pressure shall be maintained for at least 15 seconds. No leakage or permanent deformation shalloccur.

Test pressures are defined in 4.1.9.

3.2.4.7 Internal treatment and sealingPipes may undergo cleaning treatment in accordance with 2.3.6.3.

3.2.4.8 MarkingsThe accepted pipes shall bear clearly visible markings on the outside conforming with the users codeand specification or national regulations.

In the absence of the above, the following marking is recommended at a minimum of 100 mm and amaximum of 140 mm from one end of pipe and in such a way that any coat or wrapping does notcover them.

By permanent marking :• the manufacturer’s mark (identifying the factory of manufacture)• the mark of the cast• the year of manufacture• the identification number of the pipe• the required inspection and test marking

By stencilling :Where special pipes are procured whose thickness or grade differs from the standard pipes, these shallhave a clearly visible distinctive marking.

No internal marking shall be permitted.



Part 3 : Equipment


3.2.4.9 HandlingIn the course of transport and handling, all necessary steps shall be taken to prevent damage to pipesand where applicable their protective coatings.

3.3 Standard Pipe Fittings


3.3.0.1 DefinitionsThe name ‘Standard Pipe Fittings’ is given to pipeline elements such as• bends or elbows• reducer cones• tees• caps or dished ends• weldolets etcGenerally these parts are available as standard items.

3.3.0.2 MaterialsIt is generally desirable to use for pipe fittings the same grade of metal as that of the correspondingpipe.

As pipe fittings made of copper alloy are special products, the potential user shall, in collaborationwith the manufacturer, study the characteristics required shaped parts of equipment as a function oftheir intended use.

3.3.0.3 ThicknessThe thickness required for the various parts of these elements shall comply with the standards andregulations in force as a function of the intended conditions of use.

3.3. 0.4 EndsAll ends for welding shall be trimmed and prepared in a plane perpendicular to the axis of the pipe towhich they are to be welded.

Edges shall be clean and free from burrs.

Ends for butt welding shall be bevelled.

3.3.0.5 Appearance and dimensionsDimensions, theoretical mass, tolerances, permissible irregularities or defects of structure andappearance shall comply with the national standards in force.

3.3.0.6 TestsStandard pipe fittings do not generally undergo internal hydraulic testing by the manufacturers.

3.3.0.7 Internal treatmentNo coating, covering or grease shall be tolerated on the internal surfaces of pipe fittings. Pipe fittingsshall undergo cleaning treatment as indicated in 2.3.6.2 and 2.3.6.3.

3.3.0.8 InspectionInspection shall be carried out to ascertain conformity with the users code, specifications or nationalregulations.

3.3.0.9 MarkingsAll markings shall be on the outside of the element.



Part 3 : Equipment


3.3.1 Bends

3.3.1.0 GeneralBends shall comply with the recommendation of 3.3.0 and to the relevant specifications. Bends mayhave different radii according to standards.

These bends are made from seamless pipes.

They may be 45°, 90° or 180°.

These bends are available in various thicknesses.

The thickness shall be selected as a function of the anticipated conditions of use.

The use of long radius types are preferred.

3.3.2 ReducersReducers are defined by their large and small diameters (D and d). For any given large diameter Dthere is a number of reduced diameters d defined by the Standards.

According to standards reducers may be of constant angle or length.

Reducers may be concentric or eccentric.

Reducers shall comply with the recommendations of 3.3.0 and the following :• The thickness shall be selected as a function of the conditions of use.• When eccentric reducers are used in a horizontal position, it shall be ensured that the straight

generating line is at the bottom.

3.3.3 Pipe Caps or Dished EndsDished ends or pipe caps may be :• or large squaring-off radius• elliptical• of the ‘cap’ type for welding on pipesElliptical ends and those with a large squaring-off radius are generally used in the manufacture ofpressure vessels (storage tanks for gases, etc) while the ‘cap’ type of end is used for pipeline elementsor components.

Dished ends shall comply with the recommendations of 3.3.0 and to the relevant specifications.Dished ends may be of various thicknesses. The thickness shall be selected as a function of theconditions of use.

3.3.4 Tees and Other Branches

3.3.4.0 GeneralBranches may be made by means of :• Forged tees• Reinforced branches (weldolets, sweepolets, etc)• Fabricated tees• Welding of two pipes, making a given angle and reinforced, if required, by means of gussets or

plates.It is preferable to use forged tees or reinforced branches of the weldolet, etc., type because theirmechanical strength is generally better than that of branches made by the direct joining of two pipes(angled or right angle tappings).

Tees and branches shall comply with the recommendations of 3.3.0 and the following.

3.3.4.1 Forged teesForged tees may be :• Equal tees, for joining a branch of the same diameter as the pipeline• Reducing tees, for connecting a branch of smaller diameterThe thickness shall be selected as a function of the intended conditions of use.



Part 3 : Equipment


3.3.4.2 Reinforced branchesReinforced branches of the ‘-olets’ family (weldolets, sweepolets, etc) are forged shaped partsspecially designed to effect branching without the need for any supplementary reinforcement.

-Olets (weldolets, sweepolets, etc) shall be selected to suit the conditions of use in accordance withthe manufacturers instructions.

-Olets shall only be used where the branch diameter is smaller than that of the main pipeline,otherwise the cut in the pipeline would be too large causing deformation during welding.

3.3.4.3 Fabricated TeesThe use of fabricated tees (angled or perpendicular) between pipes of equal diameter should beavoided.

Care shall be taken in calculating and making any necessary reinforcement.

3.4 Assembly Components


3.4.0.1 DefinitionsAssembly components are defined as devices which permit connection or disconnection of pipelineelements to each other or to components.

Bolted assemblies are defined as flanges, and screwed assemblies are called couplings.

3.4.0.2 Gaskets and jointing materialsGaskets and jointing materials, if they are necessary, shall be selected from the materialsrecommended in 2.1.4.

3.4.0.3 Leak-tightnessWhatever the type of assembly concerned it shall be leaktight. Any leakage may lead to ignition.

3.4.0.4 Mechanical strengthFlanges and couplings shall be selected as a function of the conditions of use.

3.4.0.5 CleanlinessFlanges and couplings shall be cleaned and degreased.The joint faces of flanges and couplings shall not contain any trace of paint or varnish. If flanges aredelivered with their joint faces protected against corrosion by a coat of varnish, this shall be removedin accordance with 2.3 before the flange is assembled into the installation.

3.4.1 Flanges

3.4.1.0 GeneralFlange assemblies are generally used for 1” diameter (DN 25) pipes and above.

3.4.1.1 StandarisationIn most industrial countries there are standards that define the types of flanges, their dimensions, theircharacteristics and the conditions (pressure and temperature) for their use.

Flanges are defined :• according to their type• i.e. weldneck, slip-on socket screwed and backing• according to their rated pressure (see 1.1.3.2).



Part 3 : Equipment


3.4.1.2 Flange selectionThe flanges preferred for use on oxygen pipelines are weld neck for butt welding.Flanges of non-standard dimensions, (special flanges) may be used for certain components. In thesecases the dimensions of the flanges shall be determined by the designer of the component as afunction of the metal, the type of joint and the conditions of use.

Where screwed flanges are used leak tightness between flange and pipe may be obtained by :• a line of welding or brazing at the back of the flange• by P.T.F.E. tape in accordance with 2.1.5.

3.4.1.3 Materials for weldneck flangesWeldneck flanges shall be of weldable steel.

Flanges of stainless steel or copper alloy may be used.Their dimensions shall be determined as a function of the nature of the metal, the type of joints andthe anticipated conditions of use.

The steel flanges of steel pipeline elements may be connected to the flanges of a stainless steel orcopper alloy component.

3.4.1.4 Materials for other types of flangesMaterials and dimensions are selected as a function of the type of joint and condition of use incompliance with appropriate standards and recommended materials in 2.1.

3.4.1.5 Conditions of useThe conditions of use (pressure and temperature) of flanges are defined by the appropriate standards.

3.4.1.6 Flange facesFlange faces shall be selected as a function of the nature of the gasket used. The flanges may have :• a flat or raised face for use with flat or similar gaskets• single or double recessing for 0 rings or annual gaskets• specially shaped flange bearing surfaces for special metallic gaskets.When using flat seals on flanges without recesses, it is necessary to make sure that the seal does notproject into the interior of the pipe.

3.4.1.7 InspectionThe appearance, dimensions, chemical analysis and mechanical testing of the materials and of theflanges shall comply with the national standards.

3.4.1.8 Nuts and boltsNuts and bolts shall comply with the relevant standards.For special flanges the nuts and bolts shall be specified by the flange designer as a function of theanticipated conditions of use.

3.4.1.9 BondingIf flanges have gaskets which are electrically non-conductive, the two flanges shall be fitted andconnected to each other by a bonding strip (see 4.2.5.14).



Part 3 : Equipment


3.4.2 Couplings

3.4.2.0 GeneralCouplings are used for :• union couplings between pipes• Couplings for connection to components or elements of a pipeline (male or female connections)They may be :• straight• elbow• tee• cross• etc. (see fig.17)

They may be used on auxiliary pipes or piping whose diameter is equal to or less than 40 mm (1.1/2").For pipes of nominal diameter 50 mm (2”) and over it is preferable to use flange assemblies accordingto 3.4.1.

Whatever the type of coupling used it shall be fitted with care and in accordance with the instructionsof the designer. The best of couplings leak if badly fitted and could become a safety risk.

The effort required for tightening is dependent upon the type of coupling used. The various designs ofcoupling are dealt with in 3.4.2.3 to 3.4.2.7.

3.4.2.1 MaterialsThe material for couplings shall be chosen from the materials recommended in 2.1.1.2.Materials liable to produce electro chemical action shall be avoided. Couplings shall, therefore, bemade of a similar material to that of the pipework to which they are fitted.

Since drawn brass is subject to mechanical fracture due to possible flaws or cracking, its use is notrecommended.

Die-stamped or forged brass may be used. Use of cast iron shall be limited due to its low mechanicalcharacteristics.

3.4.2.2 Leak-tightness of screw threadsThe leak-tightness of the threads for coupling connections to a component may be made:• by means of a taper thread• by means of taper thread with PTFE tape according to 2.1.4.5. Fig (8b).• by means of a parallel thread with a flat gasket compressed between coupling and component in

compliance with materials in 2.1.4.2.• by means of tinned threads.

3.4.2.3 Leak-tightness of couplingsCouplings are distinguished according to the methods of sealing:• Couplings with metal-to-metal seal, such as

• a conical or spherical contact surface• flared tube• an olive

• Couplings with a seal packing such as flat gasket or O-ringFor each type of coupling there is a multiplicity of patented models and selection is generallyconditioned by company standards.

For oxygen installations it is preferable to use metal-to-metal seal couplings. Couplings with a non-metallic packing should be reserved for installations requiring frequent dismantling.

3.4.2.4 Couplings with conical or spherical contact surfaceThese are ‘three piece’ couplings whose seal is ensured by contact between two surface lines of theconnection parts. The contours of these surfaces may be :• cone to cone, with different angles• cone to sphere

The contact surfaces shall be perfectly clean and in good condition.



Part 3 : Equipment


3.4.2.5 Flared tube couplingsThis type of coupling is used for relatively thin walled pipes.The seal is obtained by contact of the flare at the end of the pipe with the conical contact surface ofthe nipple.

It is generally necessary to provide a special tool to flare the pipe correctly.

Some types use a sleeve which prevents rotation of the pipe during tightening.

3.4.2.6 Olive couplingsThis type of coupling has a metal ring which effects limited deformation or penetration of the outerwall of the pipe to be connected.

Tightening of the nut effects a seal between the olive and the pipe and between the olive and thenipple of the coupling.

This coupling eliminates threading, welding or flaring of the pipe but requires careful assembly.(Strict observance of assembly instructions provided by the coupling designer).

The mechanical characteristics and dimensions of the parts shall be related to the material anddimensions of the pipe and shall comply with the Manufacturers specification,

Numerous types of coupling are commercially available. They generally differ only in the shape andmanner of sealing effected by the olive.

3.4.2.7 Flat seal or O-ring seal couplingsThe leak-tightness of this type of coupling is obtained by means of either a flat or an O-ring, generallyfitted inside the nipple.

The seal material shall be chosen from the materials recommended in 2.1.4.2.

If the flat seal is of non-metallic material it shall not project into the inside of the pipe.

It is preferable to use couplings with a metal seal.

3.4.2.8 Connection of couplings to pipeworkWith the exception of flared pipe and olive type couplings, for which the pipe is directly held bytightening of the nut, the other couplings require the fitting of an adaptor on the end of the pipe.

The fitting of this adaptor depends upon the pipe material, its diameter and thickness and theconditions of use.

The main methods are :

a) by welding

b) by silver brazing

c) by screw threadingLeak-tightness of the screw thread can be obtained by means of either a welded or brazed silver beador PTFE tape.

3.5 Miscellaneous Accessories

3.5.1 Flexible Pipes

3.5.1.0 GeneralThis section concerns only small diameter (25 mm and below) flexible connections of short lengthwhich are likely to be used in oxygen distribution installations dealt with in this Code.

3.5.1.1 Possible usesThey may be used for connecting instrumentation components to the main pipeline, for instrumentsthat are sensitive to vibration.

Generally speaking, preference will always be given to rigid metal pipelines.Flexible connections should be installed together with a safety device attached to the flexibleconnection to prevent dangerous whipping in case of fracture.



Part 3 : Equipment


3.5.1.2 MaterialsThe inner tube shall be smooth and of either copper alloy or fluorinated or chlorofluorinated resin.Hoses with corrugated inner tubes are not recommended.

The outer sheath shall consist of a single or double metal braid.Additional outer sheaths of chlorinated or nitrated elastomer may be added in order to improveprotection of the hose against outside influences.

End fittings shall be of copper alloy or stainless steel. Drawn or turned brass shall not be allowed forhoses liable to be subjected to vibration.

3.5.1.3 Inspection and testingFlexible pipes shall be clean and degreased (see 2.3.8).They shall have undergone a hydraulic strength test at twice the maximum design pressure and also aleak-tightness test.

The leak-tightness test shall be with nitrogen. With the hose submerged in a tank of water, no bubblesshall appear.

3.5.2 Expansion Elements

3.5.2.0 GeneralAt ambient temperatures the thermal expansion of mild carbon steel is of the order of 0.0117mm perdegree C per metre length.

Under the same conditions, the thermal expansion of copper and stainless steel is 40 to 50% greaterthan that of mild steel.

The free thermal expansion of above-ground pipelines of carbon steel caused by the variations inambient temperature may generally be accommodated by changes of direction of the pipeline,expansion loops or other expansion devices. The configuration of the pipeline may be designed toaccommodate the movement of the pipeline or expansion loops inserted. These solutions arepreferable to the use of expansion bellows.

3.5.2.1 Use of expansion elementsExpansion elements can be used :• To compensate for thermal expansion or contraction.• To prevent excessive stresses due to relative movement between parts of the installation.Where expansion elements are used care shall be taken to ensure that adequate supports, anchors andguides are fitted.

Where expansion bellows are used, manufacturers design and installation instructions shall befollowed.

3.5.2.2 Expansion LoopsExpansion loops may be made in one of the shapes below :

The radius of curvature shall be chosen to facilitate the use of cleaning pigs if required.If the loops are made on site, care shall be taken to ensure that their interior is perfectly clean anddegreased after the bending and fabrication operations.



Part 3 : Equipment


3.5.2.3 Expansion BellowsExpansion bellows are metallic elements which have been preformed, generally made of materialswith a high elastic limit, comprising a certain number of corrugations which allow variations of theirlength (axial movement fig. 14) or lateral movements or a combination of both.

Expansion bellows shall be of entirely metallic construction and made of the metals recommended in2.1.1.

They shall have a smooth inner sleeve to reduce turbulence and dust accumulation. Before assemblyof the sleeve, the inside of the corrugations shall be inspected for cleanliness.

3.5.3 Elements to Reduce Noise

3.5.3.1 Silencers‘Silencers’ are components which make it possible to reduce the noise of a gas flow by using baffleplates to cause expansion of the gas in stages.

Shells and baffles of silencers shall be entirely of metallic construction, made from the metalrecommended in 2.1.1. The assembly should be designed and made to avoid any relative movement ofthe parts.

If silencers make use of sound-absorbing materials, these shall be non-greasy and non-combustible,such as glass fibre or mineral wool (see 2.2.8.5).

Silencers may be used for venting systems.

3.5.3.2 Sound insulation coveringsThe reduction of noise from a pipeline and its components may be achieved by means of an outercovering.

The insulating material shall be non-greasy and non-combustible such as glass fibre or mineral wool.Care shall be taken to prevent any moisture ingress through the insulation to the pipe resulting incorrosion.

3.5.4 Other AccessoriesAny other accessory liable to come into contact with oxygen shall be designed and made in the spiritof the recommendations of this Code, from materials recommended in 2.1 and fitted clean anddegreased in accordance with the recommendations of 2.3.

3.6 Components

3.6.0 General Criteria for the Design and Construction of Components

3.6.0.1 Compliance of components with this codeThe design manufacture and supply of all components described in 3.6.1 to 3.6.9 shall conform withthe general criteria stated in 3.6.0.

3.6.0.2 Choice of safety factorsSafety factors of design used for other non-flammable and non-corrosive gas applications are alsovalid for oxygen components and pipes.

Higher safety factors are recommended for some items of equipment which are particularly sensitiveto external stresses - such as, rotary meters.

Components of a higher rating class or PN, may then be fitted for a given rated operating pressureproviding additional thickness and resistance to deformation which also improves resistance toignition.



Part 3 : Equipment


3.6.0.3 Recommended materialsComponents may be manufactured only from the suitable materials in 2.1.

3.6.0.4 Non-metallic materialsParts made of non-metallic materials (e.g. gaskets, valve seats, etc) shall have the minimum possiblemass. Parts made of non-metallic materials shall be dense, non porous and free from surface or otherdefects. Compacted fibres and powders shall be excluded.

These parts shall be securely enclosed with the minimum of play in solid metallic supports which aregood conductors of heat (e.g. copper alloys).

Parts made of non-metallic materials should preferably not face the gas flow.

3.6.0.5 Metallic parts facing the gas flowMetallic internal parts which may face the gas flow should preferably be of copper base alloys.

3.6.0.6 Components subjected to a differential pressureAny part of a component subjected to a differential pressure shall withstand the maximum valuewhich this pressure could attain (for filters see 3.6.5).

3.6.0.7 Electrical potential - conductorWhen two or more metallic elements are likely to be electrically insulated by non-metallic materials,these components shall be brought to the same electrical potential by efficient and permanentconductors (metal braiding, springs, etc). This paragraph does not apply to insulating joints as definedin 3.6.8. These conductors shall not be detachable from the outside of the valve (or withoutdismantling the valve).

3.6.0.8 Electrical devicesElectrical contacts shall not be located within components pressurised with oxygen unless they arecontained within an enclosure which prevents the entry of oxygen.

3.6.0.9 Hydrostatic testingTo hollow bodies of components subject to pressure shall be subjected to hydrostatic test at themanufacturers works and under his responsibility.

In most countries legal regulations give the test conditions for pressure vessels.

3.6.0.10 Internal surface treatmentThe internal metal walls of components of carbon steel, alloy or low alloy steel, shall be treated toremove scale and rust according to 2.3.6. Furthermore, it is recommended that further oxidation beprevented by metallic coating or by dry phosphating. The recommended descaling products are thosestated in 2.2.3.

3.6.0.11 Internal CleanlinessThe inside of components shall be clean and shall not contain any trace of paint or varnish. All partswhich are likely to come into contact with oxygen shall be kept free from any trace of oil or grease.This degree of cleanliness shall be maintained throughout all transportation, storage and assemblyoperations.

3.6.0.12 DegreasingDegreasing shall be carried out with one of the solvents recommended in 2.2.2 according torecommendations of 2.3.2 or 2.3.3. Only new solvents or those purified by distillation may be used.After degreasing no trace of the solvents or deposits shall remain the component.

3.6.0.13 LubricationAll components should be designed to function without lubrication. However, if a lubricant isnecessary to permit assembly operations or the functioning of a component, it shall be selected fromthe lubricants authorised in 2.2.1 and distributed on the surfaces to be lubricated. Its use shall be keptstrictly to a minimum. The lubricant shall be incorporated for life when the component is assembledand no trace shall be discernible from the outside.

A deviation is permitted in the case of components where experience and comprehensive testing hasdemonstrated the safe use of such components.



Part 3 : Equipment


3.6.0.14 ConnectionsThe components may be provided with flanges (standardised or special) screwed connections orwelding stubs for assembly into the pipelines. Welding stubs shall have the same internal dimensions(within tolerances permitted by relevant codes) as the corresponding pipelines and have compatiblecharacteristics. (see 3.4).

If coupling flanges are used care shall be taken that electrical continuity between the component andthe adjacent pipeline is permanently assured.

3.6.0.15 Sealing and packingComponents shall be supplied by the manufacturer with all orifices tightly plugged and sealed. If theinside contains sachets of a dehydrating product it shall be of a type stated in 2.2.6 and shall be clearlyvisible and integral with the sealing device of the largest orifice. The external face of the flanges shallnot bear any trace of varnish, grease or paint. The exterior of the body of the components may bepainted and shall bear the clearly visible inscription : “OXYGEN and Degreased for Oxygen Service”.Packing shall be designed to protect the components against damage and shock. For preservation ofcleanliness see 2.3.9.

3.6.1 Stop Valves

3.6.1.1 Compliance of components with this codeStop valves may be manually or power operated (see 3.6.1.10 to 3.6.1.18).

Their design shall comply with 3.6.1.0 and the following requirements.

3.6.1.2 Use of valveA stop valve shall not be used for regulating the flow. It shall be fully open or closed. When it isfully open it is highly recommended that the non metallic parts do not face the impact of gaseousflow.

3.6.1.3 Internal profilesThe design of the component should be simple and present the smoothest flow profile possible toreduce turbulence. Diaphragm or spherical plug valves may be of the ‘full flow’ type (without areduction in the cross section of the passageway through the valve) or the ‘reduced flow’ type (in theform of venturi). In the latter case, it shall be ensured in operation that in the reduced cross sectionthe maximum flow velocity of the gas remains in accordance with the regulations of 4.1.2.4. This isalso applicable to stop valves of the piston or butterfly types in which the moving parts often obstructa part of the cross section of the passageway.

3.6.1.4 Leak tightnessAll stop valves shall be designed so as to ensure the maximum leak tightness when in the closedposition.

3.6.1.5 Non-metallic sealingThe ratio of the mass of the non-metallic materials directly affecting the leak tightness of the valve tothe total mass (flanges included) of the valve should be the lowest possible.

3.6.1.6 Equalising valvesThe opening of certain valves may be facilitated by preliminary equalising the pressures acting oneither side of the closure element. The design, construction and operation of the pressure equalisingvalve shall conform with the recommendations of 3.6.0 and 3.6.1.19 to 21.

3.6.1.7 Quarter turn valvesSo-called quarter turn valves’ (rotary plug valves, butterfly valves) with a passageway diameter equalto 50 mm or over shall be provided with a reduction gear and wheel requiring several complete turnsof the operating wheel to completely open the valve.

3.6.1.8 Manual operationManual operation of the valves shall comply with the provisions of 3.6.1.9 to 3.6.1.11.



Part 3 : Equipment


3.6.1.9 Lubrication of manual operating devicesIf the mechanical device transmitting movement from the operating wheel to the moving part of thevalve, (bevel gear, worm gear, reduction gear, etc) requires lubrication, this shall be used in minimumquantity and be one of the products stated in 2.2.1. In this case, the kinetic transmission mechanismshall preferably be enclosed and shall not be subjected to the gas pressure. If there is a possibility ofthe oxygen moving towards the housing containing the lubricated mechanism, this housing shall beprovided with a pressure limiting device.

3.6.1.10 Position indicatorAll manual valves larger than 40 mm shall include a simple device which locally indicates theposition of the closure element.

3.6.1.11 Operation of manual valvesManual valves and actuators shall be designed for easy operation preferably by one person.

3.6.1.12 ServomotorsThe valve may be operated by means of a servomotor which may be one of the following :• pneumatic servomotors using oxygen• pneumatic servomotors using dry oil-free compressed air or nitrogen• electrical servomotors• hydraulic servomotorsWhatever type of servomotor is used the mechanism shall conform with the provisions of 3.6.1.9 and3.6.1.10 relating to manual operation.

Where servomotors are fitted to stop valves in which an equalising valve cannot be included andwhere fast opening of the valve could result in a hazardous condition the servomotor shall be designedto operate the valve slowly on initial opening.

3.6.1.13 Oxygen operated servomotorsIf a pneumatic servomotor uses oxygen as the driving fluid the construction of the moving device (forexample the ram : piston and cylinder assembly, etc) shall conform with the provisions of 3.6.0.

If the driving fluid is oxygen taken from the pipeline network, two possibilities may arise :a) the servomotor is designed to function at the pressure of the pipeline network. It shall

therefore be capable of operating the valve down to the minimum possible operating pressureof the pipeline.

b) the servomotor is designed to function at a constant pressure equal to or less than the minimumpressure of the network. In this case, the servomotor shall be provided with a pressure limitingdevice.

In both cases as indicated it is recommended that a reservoir of driving fluid be provided.

3.6.1.14 Nitrogen or air operated servomotorsIf a pneumatic servomotor uses nitrogen or clean dry oil-free air as the driving fluid, it shall bedesigned in the same way as servomotors using oxygen. However, non-metallic materials for thesealing packings of the ‘motor’ device (ram, piston and cylinder, etc) may be selected from outside ofthose stated in 2.1.2 and 2.1.4 and a label attached to the servomotor indicating “NOT SUITABLEFOR USE WITH OXYGEN”.

3.6.1.15 Electrically operated servomotorsAll electric servomotor parts shall comply with the requirements indicated in 3.6.0.8.

3.6.1.16 Hydraulically operated servomotorsHydraulic servomotors may be used with hydraulic incombustible fluids, providing suitableprecautions are taken to prevent contact with the oxygen.

3.6.1.17 Emergency controlServomotors shall be provided with emergency control, enabling the valve to be closed in the event offailure of the operating power.



Part 3 : Equipment


3.6.1.18 Fail safe deviceAutomatic stop valves shall be provided with a fail safe device which operates in the event of thedriving fluid or electric power being accidentally cut off.

3.6.1.19 Small manually operated valvesA distinction shall be made between two groups of small valves for oxygen :

a) Valves of a diameter 15 m or less normally used for pneumatic instrumentation.

The closure device for these valves should be the ‘metal to metal’ type.b) Valves of a diameter of between 20 and 40 mm inclusive generally used as shut-off, by-pass or

purging valves in small and medium sized installations.

The closure device should be of the ‘metal to metal’ type, however a sealing device ofnon~metallic material recommended in 2.1.2 and 2.1.4 is permitted.

All small manually operated valves should be constructed from copper alloy with the exception oftheir sealing equipment (O-rings, gland packing, etc) which shall be selected from the materialsrecommended in 2.1.2 and 2.1.4.

3.6.1.20 Small pneumatically operated valvesPneumatically operated valves of a diameter of between 15 and 40 mm inclusive * should beconstructed from copper alloys similar to the small manually operated valves as indicated in

Their closure device may include a non-metallic sealing device constructed from a materialrecommended in 2.1.2.

If the pneumatic actuator uses oxygen it shall comply with the provision of 3.6.0 and should be able towithstand the design pressure of the valve.

* For orifices of 15mm or under, electrically operated valves in accordance with 3.6.1.21 may beused.

Pneumatically controlled valves may be used as :

a) Venting valves; in this case the venting pipework should be made of copper or a copper alloy.

b) Automatic by-pass valves on a shut-off or regulating component fitted on a main pipe.

c) a shut-off valve

3.6.1.21 Electrically operated valvesElectrically operated valves, with a diameter of 40 mm or under. Their sealing device may make useof the non-metallic materials recommended in 2.1.2 and 2.1.4.

If these electrically operated valves are provided with a venting orifice, this shall be equipped with acopper pipe to ensure evacuation of the oxygen up to a point where it ceases to be dangerous.

The ‘valve’ part of all electrically operated valves should be copper alloys with the exception of thesealing devices which shall be selected from the materials recommended in 2.1.2 and 2.1.4.

The electrical parts shall comply with 3.6.0.8.Materials other than those stated in 2.1.2 and 2.1.4 may be used to construct the electrical operateddevice.

3.6.1.22 Manual throttling valveThese valves are used for pressuring and venting oxygen pipelines. All parts in contact with the gasshall be of copper alloy, and the closing device preferably free from non-metallic materials.

3.6.2 Automatic Control Valves

3.6.2.1 DefinitionAn automatic control valve is a valve provided with a servomechanism which enables a givenphysical characteristic of a fluid to be regulated (or maintained constant) as required. In the case ofoxygen distribution pipelines this physical characteristic is either the pressure or the rate of flow orboth.

Automatic control valves may also incorporate a “limitation of flow” function which comes intoaction only when the volumetric flow tends to exceed a predetermined maximum limit.



Part 3 : Equipment


3.6.2.2 Compliance with this codeDesign and construction of automatic control valves shall conform to the general criteria of 3.6.0 andthe requirements of 3.6.2.

The Servomotors shall be designed to comply with the provisions of 3.6.1.12 to 3.6.1.16 inclusiveconcerning stop valves.

3.6.2.3 Type of valveAutomatic control valves may be of different types eg :• single or double seated plug• Butterfly• Piston or cageCertain types of valves may also be equipped with a safety shutter which acts as an automatic shut-offelement. This shut-off element shall always be fitted upstream of the valve port.

Valves may include a noise reducing device providing it complies with recommendations of 3.5.3.

3.6.2.4 Materials of constructionThe body of the valve and its internal parts in contact with the gas should preferably be of copper basealloy. The gland packing and joints shall be leaktight and be made with authorised materials indicatedin para 2.1.2 and 2.1.4. The valve stem shall operate without lubrication.

3.6.2.5 Non leaktight valve installationAutomatic control valves which are not leaktight when closed shall comply with the provision of4.2.5.5.

3.6.2.6 Standby manual operationIf an automatic valve is provided with standby manual operation the latter shall meet the requirementsof 3.6.1.8 and 3.6.1.9.

3.6.2.7 Fail safe deviceIt is recommended that servomotors shall be designed so as to cause the valve to close in the case offailure of its operating energy unless special circumstances dictate otherwise.

3.6.3 Non-Return Valves

3.6.3.1 DefinitionA non-return or check valve is a component which prevents reversal of the direction of flow of thefluid.

3.6.3.2 Compliance with this codeThe design and construction of non-return valves shall conform to the general criteria of 3.6.0.

3.6.3.3 Type of valvesNon-return valves may be of different types e.g.:• flap• inclined flap• ball• single or double leaf.

3.6.3.4 Leak-tightnessNon-return valves shall be designed to ensure maximum leak-tightness in the closed position, i.e.when the upstream pressure is lower than the downstream pressure.

3.6.3.5 Locking deviceNon-return valves may be provided with a device for locking their moving parts in the closed position.When steel valves larger than 40 mm dia used operation of this locking device shall be designed andmade in such a manner as to allow its actuation from behind a protective screen.



Part 3 : Equipment


3.6.3.6 Small non-return valvesSmall non-return valves with a diameter of 15mm or under shall be constructed in accordance withsections above. They shall be constructed entirely from copper alloy with the exception of theirsealing devices which may be constructed from a material recommended in 2.1.2 and 2.1.4.

The valves are generally used for instrument systems.

3.6.4 Pressure Reducing Valves

3.6.4.1 DefinitionA pressure reducing valve is a valve which enables the pressure downstream of it to be kept constantwhatever the variation of flow and upstream pressure. Within the flow capacity limits of the valveand provided that the upstream pressure is greater than the downstream pressure.

A pressure reducing valve differs from an automatic control valve in that it regulates the downstreampressure without the need for an auxiliary supply or control. Pressure reducing valves may be eithergas or spring loaded.

3.6.4.2 Compliance with this codeThe design and construction of pressure reducing valves shall be in accordance with the generalcriteria of 3.6.0.

3.6.4.3 Loading gasThe pressure reducing valve loading gas may be oxygen or clean dry oil free air or nitrogen

3.6.4.4 Fail safe deviceAll pressure reducing valves shall be designed in such a way that in case of rupture of its diaphragmor in the absence of the loading gas pressure it will automatically close.

3.6.4.5 Balanced valvesAll pressure reducing valves with an orifice of 15 mm or more in diameter shall be of the “balanced”type so that control of the downstream pressure shall be maintained constant and not affected by theupstream pressure.

3.6.4.6 Leak tightnessThe valve shall be designed to ensure maximum leak tightness in the closed position.

3.6.4.7 Safety shut-offReducing valves may be fitted with a safety device that will act as an automatic shut off. This closingdevice if fitted shall always be upstream of the reducing valve.

3.6.5 Filters

3.6.5.1 FunctionThe function of filters is to arrest at selected points foreign bodies which are unavoidably conveyed bythe gas flow in the oxygen pipelines (in spite of precautions taken). Dust and foreign bodies (whethercombustible or not) may have either escaped initial cleaning or have been subsequently formed orintroduced.

Filtration enables:a) The prevention of erosion or even the deterioration of the moving parts and the seats of stop

and regulation valves, as well as non-return valves.

b) The prevention of wear of the orifice plates or venturis or the jamming (or heating by friction)of the moving parts of volumetric meters.

c) The prevention of the incrustation of particles (whether heated or not) in components offittings made of non-metallic materials.

d) The prevention of dust (whether combustible or not) in suspension in a gaseous mass rapidlyintroduced into an enclosure of small volume from attaining a dangerous temperature(adiabatic compression).

e) The elimination of the causes of spontaneous ignition of pipeline components or elementsresulting either directly or indirectly from a flow of dust (see causes of accidents 1.4).



Part 3 : Equipment


3.6.5.2 Recommended materialsThe filter bodies and elements shall be constructed solely from the materials authorised in 2.1 andconform with the general criteria stated in 3.6.0.

3.6.5.3 Filter elements made from non-metallic materialsIf filter elements are fitted with non-metallic materials such as glass fibre these shall be thoroughlycleaned to remove manufacturing lubricants and assembled using copper wire to avoid accumulationof electrostatic charges.

3.6.5.4 Filtration thresholdThe maximum filtration threshold will depend upon the extent of protection required. If filtration isnecessary, the particle size threshold shall not exceed 200 x 10-3mm (i.e. no particle over 200 micronin size shall be able to pass through the filter elements).

3.6.5.5 Strength of filter elementsThe filter elements should preferably withstand without tearing or being ruptured, a pressuredifferential between the upstream and downstream of their filter surfaces equal to their maximumworking pressure.

Filters shall be provided with pressure differential measuring devices.

The design and construction of filters shall be in accordance with the general criteria of 2.6.0.

3.6.5.6 Instrumentation filtersSmall filters used on oxygen services shall be constructed entirely of copper alloy with the exceptionof the sealing devices which may be selected from the materials recommended in 2.1.2 and 2.1.4. Oiltype filters shall not be used.

The filter elements should preferably withstand without tearing or being ruptured, a pressuredifferential between the upstream and downstream of their filter surfaces equal to the maximumworking pressure.

3.6.6 Flowmeters and Meters

3.6.6.1 FunctionFlowmeters and meters are used to:• measure the flow of gas (flowmeter)• measure the quantity of gas (meter)• or to perform both these functions simultaneously.The measurement can be used for:• counting and verifying the quantities supplied• monitoring a process• ensuring operating safety (limitation of flow)Meters are generally made up of a flowmeter and an integrating system.

3.6.6.2 Main typesIt is possible to distinguish three main types according to the measurement technique.a) Those that measure velocity : pressure differential, (orifice plate, venturi, nozzle, etc) vortex,

impeller meters, etc.

b) Those that measure volume : rotary piston (Roots), bellows, etc.

c) Those that measure mass : ‘hot wire’ meters, certain turbine meters, etc.

The following are also distinguished:a) ‘Static’ meters, i.e. those that have no moving elements (pressure differential:- orifice plate,

venturi, vortex ‘hot wire, meters, etc).

b) ‘Dynamic’ meters, i.e. those having measuring elements in motion (rotary piston, bellows,impeller, turbine, etc., meters).



Part 3 : Equipment


3.6.6.3 SelectionBecause of the features inherent in rotary machines (friction, the need for lubrication, sensitivity toexcessive speeds, etc) preference shall be given to static meters wherever their measuring performanceis able to satisfy users’ requirements.

3.6.6.4 Volume correcting devicesFlowmeters and meters may be provided with mechanical, pneumatic or electronic devices enablingconversion or correction of the gross flow into standard reference units.

Conversions and corrections apply to:• 3 factors : the pressure (P)

the temperature (T)the compressibility coefficient (Z)

• or the specific mass which includes correction/conversion for P.T.Z.

3.6.6.5 Compliance with this codeFlowmeters and their auxiliaries shall be designed and constructed in accordance with the criteria of3.6.0 and the following special provisions.

3.6.6.6 LubricationSome dynamic meters require a reserve of lubricant. This shall be selected from among the productsrecommended in 2.2.1. If the lubricant is visible from outside, there shall be a label in a prominentposition, fixed to the meter, specifying the grade of lubricant authorised. Renewal of the lubricant orthe checking of it shall be by personnel authorised by the user.

3.6.6.7 Bellows typeAs an exception for bellows type meters* with bellows requiring the use of a material notrecommended in 2.1 these may be made up of diaphragms such as leather impregnated with acarbofluorinated oil providing they are compatible with oxygen. (see 2.2.1).

3.6.6.8 Remote indicationIn the case of meters made of steel and having integral flow indicators or totalisers it is recommendedthat they be duplicated at a distance so that they can be read without approaching the meter.

3.6.6.9 AuxiliariesAuxiliary apparatus for measuring temperature, pressure, specific mass, etc., shall comply with theprovisions of 3.6.0 and 3.6.9.

3.6.6.10 Overspeed protectionSome ‘dynamic’ meters such as rotary piston meters are in danger of undergoing excessivedeformation when their maximum permitted flow is exceeded.

The friction caused by contact of the moving parts or entrained foreign particles may cause jamming,fracture and/or ignition.

These meters shall be protected by a flow limiting device.

This may be• either incorporated in the pressure regulating assembly and be controlled by a ‘flow/speed’ signal

given by the meters• or consist of an independent ‘flow limiter’ component controlled by the velocity of the gas stream

(see 3.6.9). Such a flow limiter shall be fitted at a distance of 3 to 5 diameters downstream of themeter and no other component shall be interposed between it and the meter.

* Generally intended for measuring small flows (less than 100m3/h gross).



Part 3 : Equipment


3.6.7 Safety Valves - Bursting Discs

3.6.7.1 FunctionThe purpose of safety valves and bursting discs is to prevent a pipeline or pressure vessel, etc., frombeing subjected to a pressure higher than the maximum acceptable pressure.

3.6.7.2 Compliance with this codeSafety valves and Bursting Discs shall be designed in accordance with the general provisions of 3.6.0and the following special requirements.

3.6.7.3 Operating modeSafety valves and bursting discs shall be actuated directly by the fluid.

3.6.7.4 Lifting pressureA safety valve shall open when the set pressure is reached (see 1.1.3.10) and shall be of adequate sizein conformity with the provisions of 1.1.3.11.

3.6.7.5 Bursting pressureA bursting disc shall burst in accordance with the provisions defined in 1.1.3.12.

3.6.7.6 Multiple safety devicesIf more than one safety device is used, their combined total capacity shall be designed in accordancewith the general provisions of 4.2.5.4 and the following special requirements.

3.6.7.7 Duplication of safety devicesWhen valves or bursting discs are duplicated, isolation devices shall be installed so that the system isalways protected.

3.6.7.8 MisadjustmentSafety components shall be so designed as to prevent any possibility of inadvertent misadjustment.

3.6.7.9 Safety valve materialsWith the exception of the spring, which may be of treated steel, the body and internal elements ofsafety valves should be made of copper alloy.

3.6.7.10 Disc materialBursting discs should be made of nickel. Their outer surface in contact with the atmosphere may becoated with a thin layer of PTFE or FEP in order to prevent deterioration by corrosion.

3.6.7.11 Leak tightness of safety valvesSafety valves shall be designed to ensure maximum leak-tightness in the closed position, preferablyexcluding seats of non-metallic materials,

3.6.7.12 Pilot devicesSafety valves may comprise a pilot device designed to increase the accuracy of their setting. Thisdevice shall not affect any of the provisions listed above and its possible failure shall not prevent thevalve from opening.

3.6.7.13 Vent pipesSafety components shall be provided with a vent pipe that ensures the removal of oxygen to a pointwhere it ceases to be dangerous either to the plant or personnel. This vent pipe should preferably beof copper or copper alloy.

3.6.7.14 Periodic inspectionThe proper functioning of safety valves shall be periodically checked.

3.6.7.15 Periodic replacement of discIt is desirable that bursting discs be replaced by new ones periodically, depending on materials,conditions of use and experience.



Part 3 : Equipment


3.6.7.16 Small safety valvesSmall safety valves with a diameter of 15 mm or under, shall be constructed in accordance withproceeding sections.

They shall be constructed entirely from copper alloy with the exception of their sealing devices whichmay be constructed from a material authorised in 2.1.2 and 2.1.4. These valves are generally used forinstrument systems.

3.6.8 Insulating Joints

3.6.8.1 DefinitionAn insulating joint is essentially made up of two pipe elements separated by a dielectric material.

3.6.8.2 FunctionThe purpose of insulating joints is to provide permanent electrical discontinuity between the parts ofthe installation with cathodic protection and those without it.

3.6.8.3 Ignition risksBecause of this electrical discontinuity insulating joints carry potention danger of spontaneousignition of the insulating material, caused by possible heating due to the joule effect.

If, in the interior of a pipeline a continuous deposit of dust connects the two pipeline elements, and ifthe current intensity is sufficient, the dust may be brought to a temperature capable of initiatingignition of the insulating material.

3.6.8.4 Compliance with this codeInsulating joints shall be designed and made in accordance with the general criteria of para 3.6.0 andthe following special provisions.

An insulating joint should be made in a vertical pipe or inclined at 45° max. from vertical in order toavoid deposits through the effect of gravity.

3.6.8.5 Material in contact with oxygenThe insulating material in contact with oxygen shall combine adequate mechanical with gooddielectric qualities and comply with the provisions of 2.1.2.

3.6.8.6 Material not in contact with oxygenInsulating materials not liable to be in contact with oxygen (insulants for nuts and bolts, externalcoating, etc) may be of materials other than those indicated in 2.1.

3.6.8.7 Insulating capabilityAn insulating joint shall be guaranteed to withstand a potential difference of 11000 volts (50 Hz) at acurrent intensity of less than 10 mA.

3.6.8.8 Design and installationInsulating joints shall be made to reduce the possibility of the formation of a conducting bridge.

For example, in the case of a flange type joint, the insulating part shall not be recessed.



Part 3 : Equipment


3.6.9 Other Components

3.6.9.1 General criteriaAll the components mentioned in this section shall be designed and constructed in accordance with thegeneral criteria of 3.6.0 and the following special provisions.

The small items of equipment in accordance with 3.6.9.2 to 3.6.9.6 should be designed to functionwithout lubrication in accordance with 3.6.0.13. If a lubricant is necessary to permit assemblyoperations or the functioning of the item of equipment, it shall be selected from the lubricantsrecommended in 2.2.1.

Its use shall be kept strictly a minimum: The lubricant should be incorporated for life when thecomponent is assembled and no trace shall be discernible from outside.

3.6.9.2 Flow limitersThe ‘flow limiter’ is a component with a variable passageway under the direct action of the gas flowbut independent of an auxiliary external device.

If the design of the flow limiter makes use of a deformable diaphragm or bellows, these shall be ofmetal construction.

3.6.9.3 Pressure sensors and indicatorsPressure Sensors and indicators (manometers) may be divided into two groups:• those in which the deformation of the sensitive element is measured mechanically (Bourdon tube

or metal capsule)• those in which this deformation is measured electrically (condenser, strain gauge, quartz,

differential transformer).All parts in contact with oxygen should preferably be of copper alloy.

All internal connections between the various components shall be made by brazing or welding.Dial gauges shall be provided at the rear with blow out plugs or bursting discs enabling the oxygen toescape in the event of fracture of the sensing element.

Where there is no partition between the sensing element and the gauge window, safety glass shall befitted.

Sensors and indicators with electrical devices shall be constructed in accordance with 3.6.0.8.If sensors use hydraulic fluid this fluid shall be taken from materials recommended in 2.2.1 and shallnot be in direct contact with oxygen.

All pressure sensors and indicators shall bear the clearly visible inscription ‘OXYGEN’, no oil orgrease.

3.6.9.4 Pneumatic control deviceThe pneumatic control devices can be operated using oxygen providing that materials are compatiblewith oxygen.(see 2.1.1, 2.1.2 and 2.1.4) and that vented gas can be conveyed to a safe place.

3.6.9.5 Temperature sensors and indicatorsWhere temperature measuring devices such as resistance probes, thermocouples or mercury bulbs areused, they should be welded or brazed into the pipeline in a pocket of stainless steel or copper alloy toprevent corrosion.

Sensors with electrical devices shall be constructed in accordance with 3.6.0.8.Temperature indicators which require direct reading at the place of measurement should not be usedwith oxygen.



Part 3 : Equipment


3.6.9.6 Miscellaneous items of equipmentAll miscellaneous items of equipment not stated in 3.6.9 and which may be used with oxygen inregulating and control devices shall be constructed from copper alloy and their non-metalliccomponents constructed solely from the materials recommended in 2.1.2.

They shall also comply with the general provisions of 3.6.0 and the special requirements of 3.6.9.1.In particular, items which include electrical components shall conform to the recommendations in3.6.0.8.

There are no special requirements regarding the selection of supply current and voltage for electricalequipment.



Part 4 : Equipment


The Transportation and Distribution of Oxygen by PipelinePart 4 : Equipment

IGC 13/82/E









Part 4 : Equipment


PART 4 : INSTALLATIONS................................................................................................................................6

4.1 THE DESIGN AND TESTING OF INSTALLATIONS .........................................................................................64.1.1 General ..............................................................................................................................................6

4.1.1.1 Design criteria ..............................................................................................................................................64.1.1.2 Design procedure for the pipeline.................................................................................................................64.1.1.3 Other design criteria .....................................................................................................................................64.1.1.4 Choice of design and test methods ...............................................................................................................64.1.1.5 Effects on the environment...........................................................................................................................64.1.1.6 Physical constants - oxygen..........................................................................................................................6

4.1.2 Velocity ..............................................................................................................................................74.1.2.1 General .........................................................................................................................................................74.1.2.2 Calculation of velocity..................................................................................................................................84.1.2.3 Maximum velocity in pipelines ..................................................................................................................10

4.1.2.3.1 Carbon steel pipelines ......................................................................................................... 104.1.2.3.2 Copper and copper alloy pipelines ...................................................................................... 104.1.2.3.3 Stainless steel pipelines ....................................................................................................... 104.1.2.3.4 Other materials .................................................................................................................... 10

4.1.2.4 Components................................................................................................................................................104.1.2.5 Other factors that limit velocity..................................................................................................................10

4.1.3 Pressure Losses ...............................................................................................................................114.1.4 Mechanical Strength and Wall Thickness of the Pipes ....................................................................12

4.1.4.1 Characteristics of carbon and low alloy steels ............................................................................................124.1.4.2 Calculation formulae ..................................................................................................................................124.1.4.3 Permissible stresses ....................................................................................................................................13

4.1.4.3.1 Steel pipes for transportation pipelines ............................................................................... 134.1.4.3.2 Steel pipes for stations......................................................................................................... 134.1.4.3.3 Copper, copper alloy and stainless steel pipes..................................................................... 13

4.1.4.4 Choice of Pipes...........................................................................................................................................134.1.5 Design of Components.....................................................................................................................134.1.6 Noise ................................................................................................................................................144.1.7 Cold .................................................................................................................................................144.1.8 Design of Installations.....................................................................................................................14

4.1.8.1 General dimensions ....................................................................................................................................144.1.8.2 Design of stations .......................................................................................................................................15

4.1.9 Testing - Method and Test Levels ....................................................................................................154.1.9.1 Choice of method .......................................................................................................................................154.1.9.2 Tests for transportation pipes .....................................................................................................................15

4.1.9.2.1 Specially ordered pipes (according to 4.1.4.3.1) ................................................................. 154.1.9.2.2 Ppipes that are not specially ordered ................................................................................... 15

4.1.9.3 Tests for station pipework ..........................................................................................................................154.1.9.3.1 First possibility overall test at 1.5 times design pressure .................................................... 154.1.9.3.2 Second possibility individual testing of pipes at 1.5 times maximum design pressure ....... 16

4.1.9.4 Prefabricated elements and components.....................................................................................................164.2 DESIGN AND CONSTRUCTION OF STATIONS.............................................................................................16

4.2.1 Location of Stations and Access ......................................................................................................164.2.1.1 Choice of location ......................................................................................................................................164.2.1.2 Access to and exits from stations................................................................................................................164.2.1.3 Roads and general utilities..........................................................................................................................17

4.2.2 Protection by Walls or Screens........................................................................................................174.2.2.1 Stations requiring protection ......................................................................................................................174.2.2.2 Size of stations ...........................................................................................................................................174.2.2.3 Spacing requirements .................................................................................................................................174.2.2.4 Function of protection screens....................................................................................................................174.2.2.5 Arrangement of screens..............................................................................................................................174.2.2.6 Design of screens........................................................................................................................................184.2.2.7 Choice of screens and structural arrangements...........................................................................................21

4.2.3 Buildings for Stations ......................................................................................................................214.2.3.1 Closed buildings .........................................................................................................................................21

4.2.3.1.1 Walls and partitions............................................................................................................. 214.2.3.1.2 Structural materials.............................................................................................................. 21



Part 4 : Equipment


4.2.3.1.3 Roofs of buildings ............................................................................................................... 224.2.3.1.4 Natural ventilation............................................................................................................... 224.2.3.1.5 Forced ventilation................................................................................................................ 224.2.3.1.6 Exits - lighting..................................................................................................................... 224.2.3.1.7 Venting at atmosphere......................................................................................................... 22

4.2.3.2 ‘Outdoor’ construction ...............................................................................................................................224.2.3.2.1 Protection walls ................................................................................................................... 224.2.3.2.2 Roofing................................................................................................................................ 224.2.3.2.3 Shelters ................................................................................................................................ 234.2.3.2.4 Ducts.................................................................................................................................... 23

4.2.4 Stresses due to the Ground and to Temperature Changes...............................................................234.2.4.1 Forces due to the ground ............................................................................................................................234.2.4.2 Forces due to temperature change ..............................................................................................................23

4.2.5 Design Rules for Stations.................................................................................................................234.2.5.1 Valves.........................................................................................................................................................23

4.2.5.1.1 Choice of valve operation.................................................................................................... 234.2.5.1.2 Manual operation................................................................................................................. 234.2.5.1.3 By-pass valves..................................................................................................................... 244.2.5.1.4 Automatic operation by servomotor .................................................................................... 244.2.5.1.5 Small manual or motorised valves....................................................................................... 25

4.2.5.2 Vents and pressure tappings on a pipeline..................................................................................................254.2.5.3 Temperature tappings .................................................................................................................................254.2.5.4 Safety device ..............................................................................................................................................25

4.2.5.4.1 Safety valves ....................................................................................................................... 264.2.5.4.2 Bursting discs ...................................................................................................................... 264.2.5.4.3 General requirements .......................................................................................................... 26

4.2.5.5 Pressure or flow regulating components.....................................................................................................274.2.5.6 Metering components .................................................................................................................................274.2.5.7 Other components.......................................................................................................................................274.2.5.8 Layout of station pipework.........................................................................................................................274.2.5.9 Auxiliary pipework.....................................................................................................................................274.2.5.10 Pipework and cables in ducts ..................................................................................................................274.2.5.11 Wall, partition and screen crossings........................................................................................................274.2.5.12 Electrical and pneumatic instrumentation ...............................................................................................284.2.5.13 Electrical installation ..............................................................................................................................284.2.5.14 Electrical continuity/earthing..................................................................................................................284.2.5.15 Cathodic protection.................................................................................................................................284.2.5.16 Soundproofing ........................................................................................................................................294.2.5.17 Supports and fixings ...............................................................................................................................304.2.5.18 Firebreak sections ...................................................................................................................................30

4.2.6 Prefabricated Pipework...................................................................................................................304.2.6.1 Materials.....................................................................................................................................................304.2.6.2 Design, construction...................................................................................................................................304.2.6.3 Continuity of internal diameters .................................................................................................................314.2.6.4 Headers.......................................................................................................................................................334.2.6.5 Tees and branches ......................................................................................................................................334.2.6.6 Vent, pressure and temperature tappings ....................................................................................................334.2.6.7 Dead ends ...................................................................................................................................................334.2.6.8 Cleaning and cleanliness ............................................................................................................................33

4.2.7 Construction of Stations ..................................................................................................................344.2.7.1 Start of the work .........................................................................................................................................344.2.7.2 Cleanliness during construction..................................................................................................................344.2.7.3 Fitting of pipeline components and elements .............................................................................................344.2.7.4 Welding on site...........................................................................................................................................344.2.7.5 Gaskets, nuts and bolts ...............................................................................................................................344.2.7.6 Auxiliary pipework.....................................................................................................................................344.2.7.7 Painting, cleaning of the premises ..............................................................................................................35

4.2.8 Final Inspection...............................................................................................................................354.2.8.1 General .......................................................................................................................................................354.2.8.2 Verification of conformity..........................................................................................................................354.2.8.3 Verification of cleanliness ..........................................................................................................................354.2.8.4 Verification of leak-tightness .....................................................................................................................354.2.8.5 Verification of operation ............................................................................................................................35



Part 4 : Equipment


4.2.8.6 Protection of the station..............................................................................................................................354.3 DESIGN & CONSTRUCTION OF PIPELINES ................................................................................................36

4.3.0 GENERAL........................................................................................................................................364.3.1 Study of the route.............................................................................................................................364.3.2 Drafting the Plans ...........................................................................................................................364.3.3 Regulations for Conduct of the Work...............................................................................................364.3.4. Supply of Pipes ................................................................................................................................36

4.3.4.1 Steel pipes ..................................................................................................................................................364.3.4.2 Internal treatment .......................................................................................................................................364.3.4.3 Sealing of pipe ends ...................................................................................................................................364.3.4.4 External protection .....................................................................................................................................37

4.3.5 Pipeline Construction ......................................................................................................................374.3.5.1 Staking out, marking and route preparation................................................................................................374.3.5.2 Excavation of the trench.............................................................................................................................374.3.5.3 Handling of the pipes..................................................................................................................................374.3.5.4 Making of bends.........................................................................................................................................374.3.5.5 Tappings and shapes...................................................................................................................................374.3.5.6 Preparation for welding ..............................................................................................................................374.3.5.7 Welds and approvals...................................................................................................................................374.3.5.8 Recording of welds.....................................................................................................................................374.3.5.9 Inspections of welds ...................................................................................................................................384.3.5.10 Junctions .................................................................................................................................................384.3.5.11 Test of welded sections...........................................................................................................................384.3.5.12 Sections waiting to be laid ......................................................................................................................384.3.5.13 On-site coating........................................................................................................................................384.3.5.14 Inspection of the coating.........................................................................................................................394.3.5.15 Laying in the trench ................................................................................................................................394.3.5.16 Backfilling ..............................................................................................................................................394.3.5.17 Warning of underground pipeline ...........................................................................................................394.3.5.18 Underground crossing of roads ...............................................................................................................394.3.5.19 Underground crossing of railroads..........................................................................................................394.3.5.20 Waterway crossings ................................................................................................................................394.3.5.21 Overhead crossings .................................................................................................................................394.3.5.22 Crossing or running alongside underground services..............................................................................394.3.5.23 Crossing drains .......................................................................................................................................404.3.5.24 Proximity of overhead high tension cables .............................................................................................404.3.5.25 Construction in the proximity of high tension cables..............................................................................414.3.5.26 Above-ground sections ...........................................................................................................................42

4.3.6 Pipeline Cleaning ............................................................................................................................424.3.7 Tests .................................................................................................................................................42

4.3.7.1 Strength test................................................................................................................................................424.3.7.2 Leak tightness test ......................................................................................................................................424.3.7.3 Typical test procedures...............................................................................................................................42

4.3.8 Cathodic Protection.........................................................................................................................434.3.9 Restoration of the Terrain ...............................................................................................................434.3.10 Pipeline Identification .....................................................................................................................434.3.11 Pre-Commissioning Tests ................................................................................................................434.3.12 As Built Drawings............................................................................................................................434.3.13 Supervision of the Work Site............................................................................................................43

4.4 SUPPLY STATIONS ...................................................................................................................................614.4.1 General ............................................................................................................................................614.4.2 Function...........................................................................................................................................614.4.3 Construction ....................................................................................................................................614.4.4 Special Considerations ....................................................................................................................61

4.5 VALVE STATIONS....................................................................................................................................614.5.1 General ............................................................................................................................................614.5.2 Function...........................................................................................................................................614.5.3 Construction ....................................................................................................................................614.5.4 Special Considerations ....................................................................................................................62

4.6 DISTRIBUTION STATIONS ........................................................................................................................624.6.1 General ............................................................................................................................................624.6.2 Function...........................................................................................................................................63



Part 4 : Equipment


4.6.3 Construction ....................................................................................................................................634.6.4 Special Considerations ....................................................................................................................634.6.5 Protection of Customers Network....................................................................................................63

4.7 RECOMPRESSION STATIONS ....................................................................................................................634.8 PRESSURE REDUCTION STATIONS ...........................................................................................................634.9 STORAGE VESSELS (BUFFERS) ................................................................................................................64

4.9.1 General ............................................................................................................................................644.9.2 Construction of Buffers....................................................................................................................644.9.3 Design..............................................................................................................................................64

4.9.3.1 Regulations and design...............................................................................................................................644.9.3.2 Design pressure ..........................................................................................................................................644.9.3.3 Piping connections .....................................................................................................................................644.9.3.4 Flange connections .....................................................................................................................................644.9.3.5 Stop valves and vent valves........................................................................................................................644.9.3.6 Safety valves...............................................................................................................................................644.9.3.7 Manholes ....................................................................................................................................................644.9.3.8 Ladders and attachments ............................................................................................................................64

4.9.4 Inspection and Cleaning ..................................................................................................................654.9.4.1 Inspection and tests ....................................................................................................................................654.9.4.2 Cleaning .....................................................................................................................................................654.9.4.3 External finish ............................................................................................................................................65

4.9.5 Installation.......................................................................................................................................654.9.5.1 Foundations and supports ...........................................................................................................................654.9.5.2 Valves and controls ....................................................................................................................................65



Part 4 : Equipment


PART 4 : INSTALLATIONS

4.1 The Design and Testing of Installations

4.1.1 General

4.1.1.1 Design criteriaThe three basic criteria that determine the design of pipes and components are:• Gas velocity for safety reasons• Pressure losses so as to obtain flow conditions compatible with operating requirements.• Mechanical strength (pressure, temperature and stress).Where modifications are made to an existing network, the new conditions of pressure, flowrate andvelocity throughout the system shall he verified.

4.1.1.2 Design procedure for the pipelineFor each section of pipeline, the flow rate and required pressure being known the usual sequence ofcalculations will be as follows:a. Determination of the diameter so as to obtain an acceptable pressure drop.

b. Verification of the velocity and possible adjustment of the diameter so as to observe velocitylimits.

c. Calculation of the minimum wall thickness. (Resistance to pressure).

4.1.1.3 Other design criteriaOther criteria shall also be taken into consideration. These are especially :• Pressure effects due to changes of direction• Static loads of equipment• Forces due to the wind• Stresses due to variations in temperature (expansion, contraction)• Stresses due to the ground conditions• Effects of vibration• Effect on existing supporting structures and installations• Effects of corrosion• Effect of temperature on permissible stress values• Possible legal classification of pipeline location

4.1.1.4 Choice of design and test methodsIn most countries there are regulations, codes and standards for the design for mechanical strength ofinstallations or at least of components.

The indications given here may, however, be used for the calculation of strength and testing incountries that have no specific regulations but they shall not be substituted for those of countries thathave them.

4.1.1.5 Effects on the environmentConsiderations regarding noise and cold shall also be taken into account (See 4.1.6 and 4.1.7).

4.1.1.6 Physical constants - oxygenTable XII gives some values of physical constants for Oxygen necessary for certain calculations.



Part 4 : Equipment


TABLE XIIPhysical constants at 15°C (288K)

Pressuregauge Specific heat

Thermalconductivity

Compressibilityfactor

Dynamicviscosity

bar CP = kJ / kg. °K W / cm °K Z = PV/RT Poisseuille (PI)

0

1

5

10

15

20

30

40

50

60

70

0.9187

0.9200

0.9271

0.9359

0.9451

0.9547

0.9735

0.9932

1.0129

1.0327

1.0539

0.2535x10-3

0.2543

0.2577

0.2630

0.2667

0.2705

0.2790

0.2876

0.2962

0.3049

0.3137

0.9994

0.9985

0.9960

0.9921

0.9885

0.9849

0.9780

0.9714

0.9649

0.9590

0.9537

2.003x10-5

2.005

2.014

2.022

2.032

2.042

2.062

2.074

2.114

2.142

2.172

Mass Specified in Grams per Litre

Temperature 1013mb abs 1 bar abs

0 °C

15°C

1,4290

1,3543

1,403

1,3366

4.1.2 Velocity

4.1.2.1 GeneralVelocity is not dangerous in itself. It becomes a risk factor mainly in the presence of dust and otherforeign bodies which conveyed at high speed, may be raised to a high temperature by friction orimpact.



Part 4 : Equipment


4.1.2.2 Calculation of velocityVelocity means the gas velocity in a given cross section calculated under the conditions of pressureand temperature and flow.

Actual flow rate by volumeV =

Cross sectional area

4Q 106 P0TZV =

PD2 ×3600

×PT0Z0

Q TZV = 1.313 ×

D2 ×P

V velocity of gas in m/s

Q flow in m3/h under reference conditions P0, T0

D ID of pipe in mm

P absolute gas pressure in bar

T gas temperature in K

Z coefficient of compressibility under flow conditions P and T

P0 1.013 bar absolute reference pressure

T0 273.15 K reference temperature

Z0 0.9994 coefficient of compressibility under reference conditions P0,T0

4 106 P01.313 =

π×

3600×

T0Z0

For approximate calculation, neglecting the factors T and Z the formula becomes :

QV = 358 ×

PD2

V = velocity in m/s

Q = flow in M3/h

P = abs pressure in bar

D = diameter

4 106

358 =π

×3600

× 1.013

The diagram (Fig 24) was made with the aid of this last approximate formula. It allows a quickreference and relatively accurate vertification of the velocity in relation to QP and D.



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Part 4 : Equipment


4.1.2.3 Maximum velocity in pipelinesThe following recommended limits for the velocity of flow are based on the test - and operating -results by the oxygen European Manufacturers and Distributors and on the experience of othercompetent authorities and organisations.

These values vary for a given pressure condition and are dependent upon the standard of pipelinecleanliness and assurance that the standard of cleanliness can be maintained under all operatingconditions of the system.

4.1.2.3.1 Carbon steel pipelines

For correctly designed and maintained installations the velocities shown by curve A of the graph ofFig 25 are recommended.

If there is any doubt regarding the cleanliness of the installation or where design and operatingexperience is limited, velocities defined by curve B Fig 25 are recommended.

4.1.2.3.2 Copper and copper alloy pipelines

In pipelines of copper and copper alloy it is not necessary to limit velocities. Where high velocitiesare unavoidable, the use of these materials is preferred.

4.1.2.3.3 Stainless steel pipelines

Stainless steel has the advantage that once cleaned, the internal cleanliness is easily maintained.

Velocities used for stainless steel vary according to developed working practices.

Where these working practices have not been developed, it is recommended that permissiblevelocities shown by Graph ‘A’ Fig 25 be used.

4.1.2.3.4 Other materials

For all other metallic materials, the velocities permitted shall be the same as those allowed for steel.

4.1.2.4 ComponentsFor components of reduced cross section, the smallest cross section shall not be less than 1/3 the crosssection of the pipeline.

In regulator components the possibility of sonic velocities may be accepted.

In every case the components and installations shall comply with the criteria defined in this Code.

4.1.2.5 Other factors that limit velocityThe maximum velocities permitted are rarely used in practice, because other factors intervene to keepthe velocities at relatively low levels.

Two such factors are :• Pressure losses, which increase rapidly with the velocity• Vibrations, which may be prohibitive due to

• the behaviour of components• the excessive noise created



Part 4 : Equipment


Fig. 25 – MAXIMUM FLOW VELOCITIES OF OXYGEN IN CARBON STEEL PIPELINES

For use of this diagram see 4.1.2.2 and 4.1.2.3

A Maximum permissible velocities

B Maximum velocities if doubt exists regarding cleanliness of the installation

4.1.3 Pressure LossesLoss of pressure is a loss of mechanical energy of the fluid due to friction between the fluid and thewalls of the pipeline on the one hand and between the various particles of the fluid on the other. Thislost energy is representative of the energy required for transportation.

A distinction is made between :• Regular pressure losses: those caused by flow through a straight cylindrical pipe of constant cross

section.• Particular pressure losses : those caused by peculiarities of the pipe (sudden changes of cross

section or direct, components inserted in the pipeline, etc).Reference should be made to text books for the evaluation of pressure losses for pipe components.

Some of these formulae are used for the design of slide rules, charts or computer programmes that canbe used for calculating pressure losses. For application of the formulae the main characteristics ofoxygen are given in 4.1.1.6.



Part 4 : Equipment


4.1.4 Mechanical Strength and Wall Thickness of the PipesIn chapter 3.2.1 manufacturing requirements have been defined.

Where regulations and standards are not available for carbon or low alloy steels, the basiccharacteristics are defined in 4.1.4.1 corresponding calculation formulae shown in 4.1.4.2 permissiblestresses in 4.1.4.3 and testing in 4.1.9.

4.1.4.1 Characteristics of carbon and low alloy steelsThe following values are recommended :

Rm max ≤ 580 Nmm2

Re max / Rm max ≤ 0.80

A min ≥ 18%

Rm max x A min ≥ 10.500

KCV ≥ 2.8 daJ/cm2

C + Mn/6 ≤ 0.43 wt%

METAL - shall be homogeness, weldable and killed- shall present good resistance to ageing- shall be suitable for cold bending on site

In the formulae:Rm = U.T.S. Newton/mm2

Re = Yield, Newton/mm2 for 0.2% elongationMax = maximum tolerance - Highest valueMin = minimum tolerance - lowest valueA = Elongation % for length 5.65 x √SKCV = Impact test value daJ/cm2 of Charpy notch specimen at -20°CC + Mn/6 = Weldability coefficientC = Carbon %Mn = Manganese %S = Cross section area of test piece in mm.

The above characteristics concern steels which have a guaranteed UTS of up to 520 Newton/mm2

For higher UTS steel a more detailed study is required to suit existing regulations.

4.1.4.2 Calculation formulaeThe minimum wall thickness can be calculated from the following formulae:

PD 100 + tde =

20fz + 2P×

100 − tewhere:

f = the allowable stress for the pipe material in N/mm2p = the design pressure in barD = the outside diameter in mmtd = the maximum plus tolerance for the diameter in %e = the minimum wall thickness in mmte = the maximum minus tolerance on wall thickness in %z = welding coefficient = 1 for seamless pipe or specially

inspected welded pipeFor a specific pipe transposition of this formulae makes it possible to calculate the pressure and stress.

P (D − Ze) 100 + tdf =

20eZ×

100 − te

20efZ 100 − teP =

D − Ze×

100 + td



Part 4 : Equipment


4.1.4.3 Permissible stressesThe maximum permissible stresses recommended below take the various customary safety factors intoconsideration.

4.1.4.3.1 Steel pipes for transportation pipelines

As a general rule, the pipes used to construct an Oxygen transportation pipeline can be orderedspecially and tested in accordance with 4.1.9.2.1. For these pipes the following stress values arepermitted :

a The maximum stress permitted shall be less than the smallest of the values below• when buried ≤ 0.73 − Re (yield)

≤ 0.55 − Rm (UTS)• when above ground ≤ 0.73 − Re (yield)

≤ 0.44 − Rm (UTS)Re is the conventional limit of elasticity (yield) with a guaranteed minimum of 0.2%

Rm is the guaranteed minimum breaking stress (UTS)

b The maximum works test stress shall be less than or equal to 10/11 of the limit of elasticity.

If the pipes cannot be purchased as a special order to above conditions, they shall comply with4.1.4.3.2.

4.1.4.3.2 Steel pipes for stations

For the station pipes the maximum stress in service shall be less than the lowest of the followingvalues:

f ≤ 0.625 - Re

f ≤ 0.33 - Rm

The maximum stress under test pressure shall not exceed 0.95 Re.

4.1.4.3.3 Copper, copper alloy and stainless steel pipes

The formula in 4.1.4.2 may also be used for these pipes. The stress rates permitted for working ortesting shall be those laid down by the manufacturers or the competent organisations.

4.1.4.4 Choice of PipesIt will generally be an advantage to choose a pipe of standard size and verify that the dimensionssatisfy the results of calculation.

It may also be necessary to take pipe of greater thickness than that calculated to ensure the pipesresistance to crushing or to provide satisfactory conditions for welding.

4.1.5 Design of ComponentsMost countries have their own regulations or codes for the calculation of pressure vessels.

The calculation and tests necessary to establish strength functioning and capacity of components is theresponsibility of the manufacturer based on agreed regulations, codes or standards where applicable.

It does not lie within the scope of this Code to define the conditions for the calculation of pressurevessels or components. In the case of imports it is advisable to check whether the design of thecomponents of the country of origin comply with the requirements of the importing country.

The choice of components shall be made from equipment which complies with the safetyspecifications mentioned in part three of this Code.



Part 4 : Equipment


4.1.6 NoiseNoise caused by the rates of flow and gas expansion in installations is not generally of a sufficientlyhigh level to justify special attenuation measures.

For some installations, however, steps to limit noise may be necessary.

Possible sources of noise are :• the gas flow• expansion of the gas• mechanical vibration• moving partsNoise may be reduced by careful design of pipework and selection of items of equipment.

It is also possible to reduce noise levels by means of insulation of pipework, locating equipment insidebuildings, insulating buildings, etc.

In the course of operations large scale venting of short duration to atmosphere on isolated sites, maybe necessary which exceeds the noise levels usually permitted. It is recommended the immediateneighbourhood and the services concerned (police, fire brigade, municipal authorities, railways, etc)should be advised.

4.1.7 ColdThe expansion of oxygen generates cold. Within the usual range of pressure and temperature there iscooling of the gas of the order of 0.28°C per bar pressure drop for free expansion.The approximate temperature differential is given by the formula:

273∆T = 0.28 (PA-PB)

TA

Where ∆T is the temperature drop K

PA is the pressure before expansion

PB is the pressure after expansion

TA is the absolute temperature of the gas before expansion K

It is thus possible to obtain a temperature lower than 0°C.

As the gas is dry, cooling does not affect the functioning of equipment. External condensation andpossible icing has only a minor effect upon the behaviour and appearance of equipment but underexceptional conditions, freezing may prevent the operation of certain components.

The effect of cold upon the environment is exceptional, however, if the pipework enters the ground onleaving the stations, cooling of the ground may then entail frost damage to roads or the blocking ofneighbouring water pipes by freezing. Precautions should be taken to avoid these consequences.

4.1.8 Design of InstallationsThe main elements of design of installations are the strength of the pipeline and components,verification of velocity and pressure losses. A number of other factors, including stress analysis aredealt with in 4.2 for the installations as whole and 4.3 for the transmission pipeline.Certain aspects of distribution supply and valve stations are dealt with in the following paragraphs.

4.1.8.1 General dimensionsThe choice of components will depend upon flow rate, pressure and pressure drop. The type ofequipment and especially flow meters influence the length and configuration of pipe required.

The diameter of pipework and dimension of components will affect the configuration of theinstallation.



Part 4 : Equipment


4.1.8.2 Design of stationsThe design and construction of the stations shall take into account all civil and mechanicalengineering requirements.

The civil engineering part of the work comprises the foundations, the walls or screens, the supportsand bedding of pipes and components.

The design of screens (when required) is dealt with in 4.2.2.5.

The problems of stresses due to the ground and to variations in the outside temperature are dealt within 4.2.4, see also 4.4 to 4.9.

4.1.9 Testing - Method and Test Levels

4.1.9.1 Choice of methodOxygen is a clean, dry gas and should be supplied with these qualities. Internal pollution of pipelinesalso acts against safety. If it desirable not to contaminate the pipelines by hydraulic testing whichleaves behind moisture and dust consisting of rust. It is therefore advisable to proceed to drying andcleaning after hydraulic testing. These operations are difficult on pipelines of great length. Hydraulictesting should be avoided if possible, following the recommendations of 4.3.7.1

4.1.9.2 Tests for transportation pipes4.1.9.2.1 Specially ordered pipes (according to 4.1.4.3.1)

The following 3 tests are mandatory :

1. Hydraulic strength test at the factory, individually for each pipe at a pressure equal to at least1.21 times the design pressure.

The maximum stress under test shall observe the limit laid down in 4.1.4.3.1.

2. Strength test on the site of the completed system at a pressure equal to at least 1.1 times thedesign pressure.

This test may be pneumatic if the conditions of 4.3.7.1 are observed.

3. Pneumatic leak-tightness_test on the site of the completed system at a pressure at least equal tothe design pressure.

4.1.9.2.2 Ppipes that are not specially ordered

The following 3 tests are mandatory:

1. Individual hydraulic strength test for each pipe at a pressure equal to 1.5 times the designpressure.

The maximum stress under test shall observe the limit laid down in 4.1.4.3.2.

2. Strength test on the site of the completed system at a pressure of at least 1.1 times the designpressure. This test may be pneumatic if the conditions of 4.3.7.1 are observed.

3. Pneumatic leak-tightness test on site at a pressure at least equal to the design pressure.

4.1.9.3 Tests for station pipeworkOne or other of the methods below is current practice in a number of countries.

4.1.9.3.1 First possibility overall test at 1.5 times design pressure

The following 2 tests are necessary:

1. Hydraulic strength test of assemblies or sub-assemblies at a pressure of at least 1.5 times thedesign pressure.

This test is generally preceded by non-destructive testing of the welds by selection(connections of pipes and coupling elements: tees, elbows etc).The maximum stress under test shall observe the limit laid down in 4.1.4.3.2.

2. Pneumatic leak-tightness tests at a pressure at least equal to the design pressure.

NOTE: After testing, the closing welds shall be subjected to 100% to non-destructive testing.



Part 4 : Equipment


4.1.9.3.2 Second possibility individual testing of pipes at 1.5 times maximum design pressure

The following 3 tests are necessary:

1. Hydraulic strength test of the pipes at a pressure of at least 1.5 times the design pressure, oneach pipe individually before it is put into service.

The maximum stress under pressure shall observe the limits laid down in 4.1.4.3.2.

2. Pneumatic strength test of the assembly at a pressure of 1.1 times the design pressure aftercompulsory 100% non-destructive testing of all welded joints.

3. Pneumatic leak-tightness test at a pressure not exceeding the design pressure.

NOTE: After testing, the closing welds shall be subjected to 100% non-destructive testing.

4.1.9.4 Prefabricated elements and componentsThese parts shall be subjected to a hydraulic strength test at 1.5 times the design pressure and possiblyto a leak-tightness test after assembly. The maximum stress under test shall not exceed 0.95 Re.

NOTE 1. The regulations of some countries require the hydraulic strength test to be repeated every10 years. In some cases these regulations allow exemption from this rule for certainelements if the original test pressure is twice the service pressure. Calculation of theelement shall therefore be carried out in such a way that the permissible stresses are notexceeded in the course of testing.

NOTE 2. The regulations of some countries provide for the omission of calculation and testing ofcomponents by substituting destructive tests of sample models.

4.2 Design and Construction of StationsThis section deals basically with provisions for the design and construction of the stations detailed in4.4 to 4.9.

4.2.1 Location of Stations and Access

4.2.1.1 Choice of locationIn order to prevent errors of operation the location of oxygen stations shall. be chosen so as to observea degree of isolation from installations for the distribution of flammable gases, air, water, etc.

The station should be surrounded by a fence.

It is necessary to avoid the immediate proximity of:• tanks or storage receptacles of flammable products• main public roadsIt is necessary to avoid locations where stations could be subject to:• oil dripping from installations situated above them (machinery, handling equipment)• Projected cinders or incandescent bodies• Projected materials of any kind

4.2.1.2 Access to and exits from stationsAccess to the stations and components shall be easy to facilitate quick evacuation of personnel in theevent of an accident.

Door locks shall be of the panic type, easily opened from inside or incapable of being closed whenpersonnel are inside.Exits shall open into free spaces clear of obstacles.

Locations chosen shall also enable necessary handling operations to be carried out under favourableconditions.



Part 4 : Equipment


4.2.1.3 Roads and general utilitiesThe station shall be served by an access road suitable for motor vehicles.

For supply stations of large capacity or distribution stations with a large output, the following shouldbe provided.• A source of electric power for the supply to equipment.• Powerful and robust lighting equipment sufficient to illuminate work area and exits.

Electric cables supplying this equipment shall be adequately protected.• Suitable power socket for maintenance operation.

4.2.2 Protection by Walls or Screens

4.2.2.1 Stations requiring protectionWhere installation of large stations comprising components for which experience or knowledge isinsufficient to guarantee resistance to ignition under all possible conditions of operation, walls orscreens are recommended if adequate spacing cannot be obtained.

4.2.2.2 Size of stationsLarge stations shall be considered as those for which the highest value of the pressure multiplied bythe square of the diameter for any pipe or components in the station exceeds the following limit.

PD2 > 3000

Where P is the gauge pressure in bar, andD is the nom dia in cm.

4.2.2.3 Spacing requirementsIn the case of installations according to 4.2.2.1 protection by walls or screens is necessary if thedistances shown in fig 26 cannot be observed.

4.2.2.4 Function of protection screensThe purpose of screens is to contain the effects of incident and ensure the protection of:• operators• maintenance personnel• the surrounding area• components from each otherScreens and protection walls shall be made such that maintenance personnel and operators can worksafely.

Dividing screens are used mainly in installations comprising parallel systems. They enable work to becarried out on one system while adjacent systems remain in service.

4.2.2.5 Arrangement of screensVarious arrangements may be contemplated, according to the type of station. A number of typicalexamples are represented in fig 27.

The exists shall be located in such a manner to stop flying objects and facilitate exit of the personnel.See fig 28 for typical chicane type exits.

The distance between screens shall be kept to a minimum compatible with the size of equipment,assembly work, operation and maintenance.



Part 4 : Equipment


4.2.2.6 Design of screensScreens shall be vertical and their height shall ensure effective protection, it should generally not beless than 2 metres.

Protection by screen is open to the sky (“outdoor” installation). Reinforced concrete walls constituteefficient screens. The strength of screens of lighter design shall be ensured by means of a supportingframework.

The loads to be taken into account for the calculation of screens are :

a) The conventional• Loads due to wind• The weight of the screen itself• Loads due to supports

b) Accidental Loads

In addition to conventional loads the screen shall be capable of withstanding an exceptionalload defined as follows:• A force uniformly distributed over the entire height of the screen and limited locally to a

width of 3 metres, over the length of the screen.The load per square metre will depend upon the size of the station, it is expressed as follows asa function of category:

Category Size Load

I PD2 8000 120 kgf /m2

ii 3000 PD2 8000 80 kgf /m2



Part 4 : Equipment




Part 4 : Equipment


Fig. 27 – TYPE OF PROTECTION – WALLS OR SCREENS



Part 4 : Equipment


4.2.2.7 Choice of screens and structural arrangementsThe choice will depend upon requirements and upon experience acquired. Screens shall be capable ofwithstanding the loads described in 4.2.2.6 and the materials used shall have good resistance to impactand fire.

There are various possibilities:• Walls of reinforced concrete• Walls of prefabricated blocks• Walls of reinforced concrete panels• Asbestos cement panels• Composite (“sandwich”) panelsAttention is drawn to the need for careful study of anchorages and supporting for resistance to blast.

Steel panels provide good resistance to blast and impact, but on the other hand they burn easily in anoxygen atmosphere.

Composite panels shall comprise combinations of plates or layers of metal and non-combustiblematerials (asbestos, cement, silicate etc).

4.2.3 Buildings for StationsSo-called ‘outdoor’ installations are recommended because they offer a higher degree of safety.Closed premises of small size are more liable to be subject to an oxygen-enriched atmosphere.

4.2.3.1 Closed buildings4.2.3.1.1 Walls and partitions

The walls and partitions of a closed building shall be constructed based on the recommendations of4.2.2. The surrounding walls, not exposed to possible damage, may be constructed of ordinarystructural materials (bricks, prefabricated blocks, etc). The height of buildings shall be sufficient topermit easy manipulation of the pipeline components and elements.

4.2.3.1.2 Structural materials

The buildings shall be constructed entirely of non-flammable materials, including the floor, doors,framework, etc.



Part 4 : Equipment


4.2.3.1.3 Roofs of buildings

Roofs shall be capable of stopping projected incandescent materials (reinforced concrete, metalstructures with sheets of asbestos cement, etc). Where there is forced ventilation the building shall beprovided with blow out flaps so that perforation of the pipeline will not give rise to any dangerousinternal excess pressure.

4.2.3.1.4 Natural ventilation

A free space of at least 0.5 m high shall be arranged over the entire periphery (except the posts)between the walls and the roof for removing smoke and gases and to prevent pressurisation of thebuilding in the event of extensive leakage due to fracture. The open area thus created shall be at least100 times the cross section area of the biggest pipe element in the building.

In order to assist ventilation, whether natural or forced, grilled openings with a total area of(open area / 20) shall be provided at the lowest part of the walls.

4.2.3.1.5 Forced ventilation

If natural ventilation cannot be considered (excessive dustiness of the atmosphere) forced filtered inletventilation shall be provided, and one or more extraction fairs fitted high in the walls to draw the airfrom the building and exhaust it to the outside. The total delivery rate of these ventilators shall besufficient to renew the atmosphere of the building at least 3 to 4 times per hour. It is not necessary forthese ventilators to operate continuously. They may be linked to:• an abnormal increase (greater than 22%) of the oxygen concentration in the building.• the opening of one of the doors to ensure the renewal of the air before entering the premises.

4.2.3.1.6 Exits - lighting

Closed buildings shall have a sufficient number of exits. Their location shall be studied in relation tothe position of the components requiring attention (filters, meters, valves, etc). These exits shall bebrightly lit, even during the day when work is being done, so as to be seen through smoke in the eventof a fire. This lighting shall be switched on automatically when a door is opened and shall only beextinguishable by means of a manual switch inside the building in the immediate vicinity of the exits.

Doors of the building shall be of the emergency exit (‘panic' type) opening outwards simply by beingpushed (see 4.2.1.3).

Electrical equipment for lighting shall be of standard design and comply with recommendations in4.2.5.13.

4.2.3.1.7 Venting at atmosphere

Venting lines for valves, vents, pneumatic instrumentation using oxygen as the driving fluid, etc.,shall lead into a manifold and be vented outside of buildings by means of copper or copper alloypipelines. (See 4.2.5.4.3).

4.2.3.2 ‘Outdoor’ constructionIn 4.2.2 the provision of protection by a wall or screen is recommended for some large installations.

4.2.3.2.1 Protection walls

In order to ensure good rigidly and stability of the structure and to prevent ‘blow out’ of walls in theevent of an incident the following are recommended:• walls integral with the floor and foundation• partitions integral with the floor and foundations acting as supports to the main walls.• linking by means of lintelsIn order to prevent disintegration and projection through walls, the spacing of reinforcements shouldbe limited (25cm may be used as a guide).

4.2.3.2.2 Roofing

In ‘outdoor’ installations, control instruments may require protection against inclement weather.

Where the instrument room forms part of the station structure, the roof shall be made of reinforcedconcrete. (Fig 29)



Part 4 : Equipment


4.2.3.2.3 Shelters

It may be necessary to provide a shelter above certain delicate components to protect them from therain or to facilitate maintenance.

Fragile sheets such as those of fibrocement shall be avoided because of the danger they present in theevent of fragmentation.

Use may be made of flexible light materials or solidly fixed ‘safety’ glass panels.

4.2.3.2.4 Ducts

If ducts are required for instrument lines (pipes and cables), they shall have a slope of at least 1% inorder to permit drainage. They shall be connected to an outfall. Ducts shall be covered by reinforcedconcrete slabs or chequered steel plate

4.2.4 Stresses due to the Ground and to Temperature ChangesEvery line should be the subject of calculation which takes into account expansions and settlementdifferentials. The design shall take account of permissible stressing of components. The use ofexpansion devices should be considered see 3.5.2.

4.2.4.1 Forces due to the groundForces due to ground changes shall be taken into account when designing the station.

These may arise from:• settling of the ground• undermining of the ground• modification of the characteristics of the ground• effect of change of water table.

4.2.4.2 Forces due to temperature changeForces may result from the differential effect of ambient temperature on systems made up of twoparts, one of which is above and the other below ground.

4.2.5 Design Rules for StationsThe number of components should be kept to a minimum compatible with requirements since theymay be the most likely cause of incidents. All components shall comply with Part 3 of this code.Instructions for the installation of components shall be observed (i.e. handling, supporting, directionof flow, etc).

4.2.5.1 Valves4.2.5.1.1 Choice of valve operation

Shut-off valves may be manually or automatically operated according to the design of stations andopertional requirements.

4.2.5.1.2 Manual operation

If a manually operated valve is installed behind a protective screen or wall (see 4.2.2) its operatinghandwheel shall be in front of the wall.

Use may be made of:• an extended operating rod, or• an angled lever device.If a device without an effect angle is used, a stop shall be provided integral with the extension of theoperating rod so that in case of accident the rod or handwheel cannot strike the operator. Fig 29shows some examples of manual operation of a valve.

SAFETY ARRANGEMENTS OF VALVE OPERATING SPINDLES

The object of these arrangements is to prevent the spindle or the handwheel from striking the operatorin the event of explosion or projection.



Part 4 : Equipment


4.2.5.1.3 By-pass valves

It is recommended that stop valves of inside diameter 150mm or more should not be opened until thepressures upstream and downstream have been balanced (see 3.6.1.6). Stop valves may besupplemented by a by-pass valve in accordance with 3.6.1.19.

In horizontal pipelines upstream and downstream connections for the by-pass valves shall be installedabove the horizontal centre line of the pipe. (Fig 30A).

If electrically or pneumatically operated by-pass valves according to 3.6.1.20 are used, the insidediameter should be equal to or less than :• one-fifth the inside diameter D of the main pipeline, if the distance from the stop valve to the next

following shut-off component is equal to or greater than 100 D.• one-tenth of the inside diameter D of the main pipeline in other cases.• On valve stations up to 400mm diameter, the diameter of the by-pass valves should not be greater

than 100mm and should be sized according to volume of the downstream system.In by-pass valves high velocities prevail during balancing of the pressures. Use shall, therefore, bemade only of valves made of copper alloy.

If the main shut-off valve is behind a protective screen, the by-pass valve should also be behind thescreen if its inside diameter is equal to or greater than 15mm. If this valve is manually operated itshall be provided with an extension to allow its handwheel to be in front of the wall or screen.

4.2.5.1.4 Automatic operation by servomotor

It shall not be possible for a shut-off valve equipped with motorised operation to be opened before thepressures upstream and downstream of it have been balanced.

For this purpose, the operating circuit shall be designed so that the by-pass valve opens first. Whenthe pressures upstream and downstream are practically equal (ratio between the two equal to or lessthan 1.1) the main valve may be opened. In the case of a signal to close, the main valve and itsby-pass shall close simultaneously.



Part 4 : Equipment


If a pneumatically operated valve is operated by means of oxygen taken from the network, a reservecapacity of driving fluid shall be provided, separated from the network by non-return valve. Thisreserve capacity shall be sufficient and suited to the system.

If the pilot operation device makes use of electrical energy, it should preferably be designed so thatthe shut-off valve closes if the current is cut off.

4.2.5.1.5 Small manual or motorised valves

If the installation includes protective screens or walls (see 4.2.2) all valves greater than 15mm shall beinstalled behind the screens.

4.2.5.2 Vents and pressure tappings on a pipelineVent valves and pressure tappings shall be installed on the top part of a horizontal pipe (see fig 30).

The vent valve of a filter shall be installed downstream of the filter (on the filtered gas side) accordingto fig 31.

4.2.5.3 Temperature tappingsTemperature tappings shall be effected by means of a ‘pocket’

The pocket shall be of stainless steel or copper alloy. They shall not penetrate to a depth of more than0.5 D into the pipeline (D being the inside diameter of the pipeline).

If the pocket is fitted to a horizontal pipeline it shall be fixed to the top part of the pipe in the sameway as pressure tappings (see 4.2.5.2).

If the pocket is liquid-filled, this shall be non-flammable and shall not freeze at operating temperature(-30 to + 80°C).

The sensitive elements (thermocouples, resistance probes, etc) shall be fitted inside the pockets andnot directly into the gas stream.

4.2.5.4 Safety deviceThe requirement for safety devices such as safety valves or bursting discs in sections liable to exceedthe design pressure is generally prescribed by national regulations.

The design and construction of these safety components shall comply with the recommendations insection 3.6.7.

Safety valves have the advantage of closing when the pressure has fallen to the permitted level.

Bursting discs have the disadvantage of completely venting the parts of the network protected toatmosphere as soon as they burst. Bursting discs shall be used with working pressures sufficientlybelow their calibration pressure so as to avoid premature bursting due to metal fatigue.



Part 4 : Equipment


4.2.5.4.1 Safety valves

Oxygen installations if necessary shall have two or more valves according to the following criteria:

a) one or more main valve(s) capable of venting the entire flow of the pressure reducing valve inthe event of failure, and limiting pressure within defined limits.

No shut off component shall separate the main valve or valves from the line protected exceptas stated in 3.6.7.7.

b) A secondary valve designed to evacuate any possible leak flow from the pressure reducingvalve.

For example the set pressure of the valves may be chosen according to the criteria indicated in thefollowing table.

Set pressure (valve begins to open)Valve If secondary valve

without isolating valveIf secondary valve with

isolating valveSecondary 1P 0.95P

Main 1.03 to 1.05P 1PP may be any value lower than the maximum allowable operating pressure

The secondary valve may be isolated from the pipeline by means of a shut-off valve, to facilitatemaintenance.

Safety valves, whether main or secondary, should be fitted between the downstream side of thepressure reducing valve and the upstream side of the shut~off valve, as shown in fig 32.

4.2.5.4.2 Bursting discs

As an alternative to one or more main safety valves, a bursting disc or discs may be used.

Bursting disc installations should preferably include a secondary relief valve designed to evacuate anypossible leak flow from the pressure reducing valve.

The secondary valve may be isolated from the pipeline by means of a shut-off valve to facilitatemaintenance.

The maximum bursting pressure of the discs see 11.3.12 shall comply with the demands of the systemand shall be defined as follows:• If bursting discs only are fitted their bursting pressure shall be equal to or lower than the

maximum allowable working pressure.• If a secondary valve is fitted which opens at the design pressure the bursting pressure of the main

disc can be defined for 1.1 designed pressure.• No isolating valve shall be fitted between the bursting disc and the line except as defined in

3.6.7.7.

4.2.5.4.3 General requirements

If the station comprises several lines having pressure reduction equipment, safety devices shall befitted behind the protective walls.

Safety devices shall be provided with a vent pipe which ensures the evacuation of oxygen to a pointwhere it does not present a hazard to personnel or the installation.

Because of the high velocities prevailing in vent pipes, these should preferably be made of copper orcopper alloy, they shall be as straight as possible and firmly secured to withstand reaction forces.



Part 4 : Equipment


4.2.5.5 Pressure or flow regulating componentsIf the station is provided with pressure or flow regulating components these shall be fitted downstreamof a filter.

If the pressure regulating component is of a type that is not leaktight in the closed position (e.g.double seated clack valves) it may be preceded by an automatic leaktight shut-off valve operated bythe pressure downstream of the reducing valve.

If the main components are installed behind protective walls or screens, regulation auxiliaries thatnecessitate the approach of an operator shall be installed away from the reducing valve (e.g. in acontrol room).

A flow limiting component may be fitted either upstream or downstream of a meter except in the caseof a volumetric meter with moving parts and if the component is independent of the meter. In thiscase, it shall be fitted downstream of the meter in order to avoid excessive revolutions of the meter.

4.2.5.6 Metering componentsMetering components may be fitted downstream or upstream of flow or pressure components exceptin the case of volumetric meters mentioned in the last paragraph of 4.2.5.5.

Metering components with moving parts shall be preceded by efficient filtration to the metermanufacturers specification.

If the main components are installed behind protective walls or screens, metering auxiliaries thatnecessitate the approach of an operator shall be installed away from the meter or be duplicated so as tomake remote control and readings possible (e.g. in a control room).

4.2.5.7 Other componentsOther components (filters, insulating flanges, etc) which form part of the installation shall follow thebasic recommendations indicated in this section.

4.2.5.8 Layout of station pipeworkThe pipework of a station shall be if possible above ground level, straight, horizontal and changes ofdirection avoided.

If changes of cross section are required, reducers according to section 3.3.2 shall be used. Buriedsections shall not include components or mechanical joints.

4.2.5.9 Auxiliary pipeworkPipes for by-passing shut-off valves, venting pipes and auxiliary pipes for instrumentation shouldpreferably be of copper or copper alloy in accordance with 3.2.0.3 and 3.2.2.

Auxiliary pipes leading to instruments or control equipment should not be laid at ground level. Theyshould be grouped together in ducts or on racks as well as electric cables for instrumentation.

Buried section shall not include components or mechanical joints.

4.2.5.10 Pipework and cables in ductsIt is advisable to avoid the installation of main pipelines in ducts.

It is desirable that pipes and cables do not rest directly on the bottom of the duct but on a raised rack.

Instrument pipes or cables where laid in ducts.

Lines containing oxygen located in ducts shall not include mechanical joints or components.

Pipelines conveying flammable fluids or electric power cables (≤ 380v) shall not be installed in thesame ducts containing oxygen pipelines

4.2.5.11 Wall, partition and screen crossingsHoles or slots in walls or screens for pipework and valve stem extension shall be constructed over-sizeto allow for assembly. After assembly the openings to be finally sealed shall be finished withconcrete, after the pipe has been covered with a strip (rubber, plastic, etc) at least 5mm thick toprovide the necessary flexibility for the pipe.

The passageways for extension stems shall be lined with PVC sheaths before sealing off withconcrete. In some cases, use may be made of sealing plates but concrete is recommended. See Fig33.



Part 4 : Equipment


4.2.5.12 Electrical and pneumatic instrumentationIf instrumentation is grouped together in an enclosed building, the latter must have sufficientventilation to prevent the accumulation of air enriched with oxygen in the event of possible leakagefrom the oxygen instrumentation circuits.

The vents shall comply with 4.2.3.1.7.

The supply voltage for electrical instrumentation should be normally less than 250V-AC or 50V-DC.

Pneumatic instrumentation shall be equipped with an isolating valve according to section 3.6.1.19 topermit maintenance of the apparatus.

4.2.5.13 Electrical installationElectrical installation of a station may be effected with standard equipment provided the equipment isinstalled in an adequately ventilated building. Equipment installed in the open shall be weatherproof.

Explosion-proof equipment, where oxygen may come into contact with electrical parts does notimprove the level of safety.

Electric cables shall be of adequate section for the current carried.

4.2.5.14 Electrical continuity/earthingCare shall be taken to ensure that the whole of the station pipework installation is permanently at thesame electric potential. For this purpose all flange couplings, excluding insulating joints shall beelectrically bonded for example by means of copper braid under heads of bolts of at least 20mmsection. The contact surfaces shall be clean and free from oxidation or paint. See 3.6.0.7.

If the flanges are fitted with electrically conductive gaskets it is unnecessary to bridge them withbraiding. Various earthing arrangements are possible, a typical arrangement is shown in fig 34. If thestation is under cathodic protection see 4.2.5.15.

4.2.5.15 Cathodic protectionTwo cases may arise:

The station is not under cathodic protection:

This is the most frequent case of distribution stations and the installation shall be earthed.

The station is under cathodic protection

This may be the case for valve stations for which the installation shall be insulated electrically fromearth and installations designed accordingly. In particular :• wall penetrations• Instrumentation couplings• supports• valve stem extensionValve stem extension shall have an insulating joint for the protection of operators and this joint shallbe capable of transmitting the operating torque to the componment.



Part 4 : Equipment


4.2.5.16 SoundproofingThe soundproofing of pipework installed in the open air may be effected by means of acousticinsulation covering according to section 3.5.3.2.

Where insulation covers flanged connections, it shall be made removable so that any leakage may bedetected.

If acoustically insulated parts have pressure or temperature tappings, these shall be made in such away that the connections are outside the insulating coating.



Part 4 : Equipment


4.2.5.17 Supports and fixingsHeavy components such as filters, shall be fixed on rigid supports of reinforced concrete or metalstructure solidly anchored to the ground.

Heavy components subject to vibration, such as rotary piston volumetric meters, etc., must be fixed tofootings of reinforced concrete.

Components such as valves, diaphragm flowmeters, flow limiters, etc., may be held by means of fixedor adjustable height supports (see fig 35 for typical example of adjustable support).Where possible, station equipment and supports should be mounted on one common base.

Small installations running along a wall may be fixed to the latter by means of metal angle brackets.

Supports for pipework and components shall be designed to allow acceptable movements only.

4.2.5.18 Firebreak sectionsIn the past, copper pipe or stainless steel sections known as firebreaks were sometimes installed in thehope of limiting the propagation of combustion of a steel pipeline.

Practical experience and research during more than 20 years of operation of oxygen pipelines has nowshown that in the event of ignition, the fire very quickly stops of its own accord, thereby confirmingthe theoretical explanation referred to in 1.3.1. For this reason, firebreaks are not recommended.

4.2.6 Prefabricated Pipework

4.2.6.1 MaterialsPipework connecting the various components of a station shall be made of materials recommended insection 2.1.1 from pipes according to 3.2 and shapes according to 3.3 and 3.4.

Use may be made of pipes and fittings made of carbon steel and assembled by welding. In some caseswhere high velocities may prevail, e.g. valve station by-passes, prefabricated copper or copper alloyelements may be used.

4.2.6.2 Design, constructionPrefabricated pipework shall be designed and constructed in accordance with the standards andregulations in force in the country where they are to be used.

Welds shall comply with the recommendations of 4.3.5.7.



Part 4 : Equipment


4.2.6.3 Continuity of internal diametersCare must be taken to ensure that for any given nominal diameter the pipes, flanges and fittingsmaking up a prefabricated element are of the same schedule i.e. of the same inside diameter (fig 36).

If for any reason it is necessary to use pipes and flanges of different schedules, a chamfer shall bemade on the element of smaller diameter as shown in (fig 36).

Tees reductions and other alterations of section shall avoid protusions or changes of profile. See Fig37 and 3.3.2.



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Part 4 : Equipment


4.2.6.4 HeadersIn the case of installations comprising lines in parallel headers shall preferably be made according tothe diagram in fig 39.

4.2.6.5 Tees and branchesCouplings of two pipe elements by Tee shall comply with the recommendations of section 3.3.4.

4.2.6.6 Vent, pressure and temperature tappingsTappings for vent valves or pressure or temperature gauges welded to prefabricated elements shallcomply with the recommendations of 4.2.5.2 and 4.2.5.3.

4.2.6.7 Dead endsElements comprising dead ends shall be avoided, especially downstream of expansion components fig40.

4.2.6.8 Cleaning and cleanlinessAfter assembly, prefabricated pipeline elements shall be cleaned and treated according to therecommendations of 2.3.6.



Part 4 : Equipment


4.2.7 Construction of Stations

4.2.7.1 Start of the workAssembly of components and pipework should not begin until the main civil engineering work(foundations, walls, paving, etc) is completed.

4.2.7.2 Cleanliness during constructionPersonnel entrusted with the assembly and erection of the installations shall wear reasonably cleanworking clothes that are not stained with oil or grease and keep their hands washed clean of all oil,grease, etc. for tools and handling see 6.1.4.

4.2.7.3 Fitting of pipeline components and elementsProtective plugs or seals of components or pipework shall not be removed until the last momentbefore fitting. Before their assembly, it shall be ensured by visual inspection that they are clean anddo not contain any trace of oil or grease or any foreign body.

Care shall also be taken to remove any dehydration sachets that may be inside components orpipework and to avoid introduction of impurities or foreign bodies into items of equipment duringassembly.

When work stops (at night, for holidays, etc) all openings shall be effectively sealed by plastic caps orother clean, safe and watertight means.

In the event of lengthy interruption of work (more than a week) or at the end of assembly if takinginto service is not immediate, the installation shall be filled with dry oil free nitrogen.

The whole of the pipework and components shall be aligned in relation to the points of reference.

During the assembly and erection of pipework and components care shall be taken to ensure thatflanges are concentric, parallel/perpendicular to the axis of the pipeline. Correction for bad alignmentby excessive tightening of the bolts or by using mechanical means such as levers, winches, clamps,jacks, etc., is not permitted.

When the bolts of a flange joint are loosened, the faces of the two flanges shall remain parallel andconcentric without moving appreciably away from each other.

4.2.7.4 Welding on siteIf welds have to be made on site, the components and pipework shall be carefully cleaned anddegreased if necessary, according to the recommendations of 4.2.6 before they are placed in their finalpositions. (See 2.3.6.2).

4.2.7.5 Gaskets, nuts and boltsGaskets shall be clean and comply with the recommendation of 2.1.4.

Nuts and bolts of flanges shall comply with the recommendations of 3.4.1.8 and be degreased beforeassembly by means of a solvent recommended in 2.2.2.

Excessive tightening of nuts and bolts shall be avoided and the relevant instructions be observed. Inthe absence of specified tightening torques, the rules of the art will be observed as a function of thenature and size of the flanges and bolts, of the working pressure anticipated and of the nature of thegasket. The threaded ends of bolts may be covered by plastic or rubber caps in order to prevent thescrew threads from being coated with paint or from corroding.

4.2.7.6 Auxiliary pipeworkSmall auxiliary pipework made on site shall, before being connected to their respective componentsand instruments, be carefully cleaned and degreased according to the recommendations of 2.3.2, and2.3.2.6.

Couplings shall comply with the recommendations of 3.4.2.

Pipes for venting to atmosphere shall be horizontal and bevelled at 45° to prevent entry of rainwater,etc.



Part 4 : Equipment


4.2.7.7 Painting, cleaning of the premisesWhen the final inspection has been satisfactorily carried out according to the recommendations of4.2.8, the following finishing work shall be undertaken :• if the installation includes protective walls, the openings in them for pipelines and manual valve

extension stems shall be closed in accordance with the recommendations of 4.2.5.11.• any grouting of components or their supports to their respective foundations shall be effected.• carbon steel components and pipework shall be given a protective coating of anticorrosive paint.

Care shall be taken to see that no damage is done to components or pipelines in the course of thiswork.

• care shall be taken to avoid oxygen enrichment while paint is drying.• at the end of the work the station shall be cleaned and any elements not necessary for its

operation, such as wood blocks, tools, rags, papers, pots of paint and solvents, handlingequipment, etc., be removed.

4.2.8 Final Inspection

4.2.8.1 GeneralFinal inspection shall take place after complete assembly of the installation to verify compliance with4.2.7 and testing in accordance with 4.1.9.

4.2.8.2 Verification of conformityThe conformity of the installation with the drawings and specifications shall be verified.

Check that there are no abnormal stresses by removal of bolts from flanged joints, one at a time toverify that the faces of the two flanges remain parallel and concentric, and do not come apart.

4.2.8.3 Verification of cleanlinessThe cleanliness of the installation shall be verified by disconnecting and inspecting selected pipeworkelements and components of the station in accordance with the recommendations of 2.3.8.2 and2.3.8.3. They shall not contain contaminants or foreign bodies as indicated in 2.3.0.2.

If necessary, the disconnected elements shall be cleaned according to the recommendations of 2.3.6.2and verification shall be extended to the remainder of the installation.

4.2.8.4 Verification of leak-tightnessFollowing removal of components and elements for inspecting and their subsequent replacement.

The leak-tightness of the installation shall be verified by means of the materials and methodsrecommended in 2.2.7 using clean dry oil free air or nitrogen at a pressure of 1 to 2 bar. Any leakagedetected shall be marked and repaired when the installation has been depressurised. The operationshall be repeated until leak-tightness is obtained.

After satisfactory results of leak-tightness at 1 to 2 bar, the pressure shall be increased in steps to themaximum working pressure and leak-tightness checks repeated.

4.2.8.5 Verification of operationUsing nitrogen or oil-free air, the setting and operation of automatic elements shall be simulated andverified.

In particular:• the opening and closing of automatically operated valves• the setting and operation of electric, pneumatic and electro-pneumatic regulators and metering

devices.• the operation of safety valves, by increasing the pressure of the test medium up to their set value.• the internal leak-tightness of shut-off valves by depressurising one or other of the pipe sections of

the station.

4.2.8.6 Protection of the stationAfter the inspection and testing of the station, painting and cleaning of the premises shall be effectedaccording to the recommendations of 4.2.7.7.

The station and associated pneumatic circuits shall be filled and maintained under an atmosphere ofnitrogen until they are put into oxygen service.



Part 4 : Equipment


4.3 Design & Construction of Pipelines

4.3.0 GENERALPipelines may be buried or above ground. For medium or long distances, the pipelines will normallybe buried.

The construction of oxygen pipelines shall be effected in accordance with the same general techniquesas those for the laying of pipelines for gases under pressure, with, in addition, a certain number ofprecautions which will be enlarged upon in following paragraphs. These are mainly precautions to betaken in order to ensure the CLEANLINESS REQUIRED FOR OXYGEN INSTALLATIONS. Apartfrom these precautions, the pipelines shall be made in accordance with :• the statutory regulations in force in the country,• national or international standards,• the professional rules concerning proper execution of the work.

4.3.1 Study of the routeStudy of the route of an oxygen pipeline shall take the following into consideration, on both privatelyand publicly owned property:• The geographical situation of the points to be supplied.• The terrain: hills, wooded areas, mining subsidence areas, built-up areas, motorways, railways,

rivers, etc.• The nature of the subsoil: water table, rock, marshland, etc.• The existing installations: pipelines, pylons for high tension electricity lines, etc.• The views of owners (private or authorities) utilising or controlling the land traversed.• The view of owners, users or controllers of buried or above-ground structures crossed by or

running alongside the pipeline.

4.3.2 Drafting the PlansWhen the survey of the route is complete, together with calculations as necessary, the following plansand documents shall be made.• A layout of the pipeline on a map, with marking of roads, railways, rivers, etc.• Survey plans for rural and urban areas or factories to the required scale.

Plans for crossings or longitudinal usage of roads, railways, rivers and canals.Plans and descriptions of special areas such as marshlands, drained areas, undulations and otherobstacles.

• A list of usages of publicly and privately owned territory, indicating the manner of laying andprotection.

4.3.3 Regulations for Conduct of the WorkThe owner of the pipeline to be installed shall ensure that the agreement with the contractor containsreference to the safety, legal and other requirements on both privately and publicly owned propertyassociated with the construction of pipelines.

4.3.4. Supply of Pipes

4.3.4.1 Steel pipesAll pipes shall be hydraulically tested. See 4.1.9, 3.2 and 4.1 deals with the problems of selection,manufacture and calculation of pipes.

4.3.4.2 Internal treatmentThe completed oxygen pipeline shall have been degreased internally and be free from scale and rustand any coating or lining. Internal cleaning of the pipe shall be carried out in accordance with 4.3.6.

4.3.4.3 Sealing of pipe endsWhen the pipes have been cleaned on the manufacturer’s premises they shall at once be sealed at bothends to prevent contamination and corrosion see 2.3.9.4. A check shall be made at the time of deliveryand at the various handling operations to see that the seals are properly in place. When the seals areremoved a check shall be made to ensure that nothing (plugs, dehydrating sachet) is left inside thepipes.



Part 4 : Equipment


4.3.4.4 External protectionThe external protection of the pipes may be carried out either on the manufacturer’s premises or onsite. See 4.3.5.13 or 3.2.1.8.

4.3.5 Pipeline ConstructionThe following operations will be carried out.

4.3.5.1 Staking out, marking and route preparation

4.3.5.2 Excavation of the trenchIt is recommended that the trench be excavated to provide a minimum cover for the pipeline of 0.75 mor to suit local conditions. See Fig 41.

The bottom of the excavation shall be free from all materials which could damage the coating of thepipeline. If necessary, a layer of sand shall be spread over the bottom of the trench.

4.3.5.3 Handling of the pipesWhen handling, care shall be taken to ensure that the external coating of the pipe is not damaged alsothat end seals remain in position.

4.3.5.4 Making of bendsBends shall be formed using a purpose designed machine. Bends having corrugations, sharp changesin wall contour or unacceptable wall thinning shall not he permitted.

If pigs are to be used for pipe cleaning, bends shall be sized to suit.

The bends will be made with pipe of the same quality as those used for construction of the pipeline.

If a method is used which requires filling the pipe with sand, it will be necessary to ensure internalcleanliness of the tube after bending.

If coated pipes are bent care shall be taken not to damage the coating.

When bends are made on longitudinally welded pipes the line of the weld shall be located on theneutral axis of the bend or at 45º to the neutral axis.

4.3.5.5 Tappings and shapesThese shall be made as shown in 3.3 and 4.2.6. In particular, the bottom line of different section shallbe in the same horizontal plane to prevent low points which form dust traps.

4.3.5.6 Preparation for weldingThe end seals shall only be removed from each pipe just prior to positioning of pipe for welding.

It is necessary at this time to check that no foreign body remains inside the pipe.

If use is made of internal clamps these shall not be lubricated, and if they are pneumatic the mediumused shall be dry oil free air or nitrogen.

4.3.5.7 Welds and approvalsAssembly of the pipes shall be effected by welding.

The welding process and the choice of electrodes or filler metal shall be selected to suit the steel of thepipes. The welders shall pass recognised qualification tests.

Welds shall have full penetration but protrusions into the pipe bore shall be strictly limited.

The root run may be by argon arc (T.I.G.) welding. The advantage of this process is that less internalsplattering occurs and a smoother surface behind the welding line is ensured. Where internal cleaningis impracticable the tig process may be recommended. On some sites good results can be difficult toachieve due to adverse weather conditions or site peculiarities.

In the event of the use of welded pipes, the seam welds on adjoining pipes should be offset from eachother by at least 10 cm.

4.3.5.8 Recording of weldsEach weld shall be given a number, this number shall be shown on reference plan of the pipes or on awelding log-book. In these documents, opposite each weld number, shall be shown the name of thewelder or his reference number together with information relative to the assessment of the weld.



Part 4 : Equipment


4.3.5.9 Inspections of weldsIn addition to visual inspection, welds shall be subjected to a non-destructive inspection by X-rays orgamma rays.

The following minimum requirement for non-destructive testing is recommended based on the provenacceptable repeatability of individual welder’s performance.• 100% until 10 consecutive acceptable welds are obtained• 75% until 10 consecutive acceptable welds are obtained• 50% until 10 consecutive acceptable welds are obtained• 30% until 10 consecutive acceptable welds are obtained• One weld chosen at random from each group of 10 welds.In the event of in unacceptable defect in the course of the 75%, 50%, 30%, and 10% inspections, oneweld upstream and one downstream of the defective one shall be inspected. If these inspections detectan unacceptable weld, the strictness of inspection shall revert to 100% before the law of diminuationindicated above is re-applied.

If use is made of an internal inspection device the carriage for the transfer of the device shall not belubricated and if it is pneumatic the medium used shall be dry oil free air or nitrogen.

Closing weld and welds made on pipeline elements underneath high-ways, motorways, railways,rivers or in the vicinity of houses, shall be 100% inspected.

The decisions of the inspection organisation with regard to the acceptance or rejection of a weld shallbe final.

4.3.5.10 JunctionsNo violent thermal or mechanical means for facilitating positioning of elements shall be tolerated,which would introduce stresses to or damage the installation.

Adequate protection shall be provided to prevent ingress of water into the enlarged section of trenchwhere welding is to be carried out.

4.3.5.11 Test of welded sectionsA pneumatic test of the welded sections may be made before the welds are coated, with verification ofthe leak-tightness of the welds with soapy water.

4.3.5.12 Sections waiting to be laidWhen sections have been assembled but not connected:• in a trench or not in a trench• preinstalled sections• road, railway, etc, crossingsthese sections shall be carefully plugged.

Similarly, when work stops, the open ends of the pipeline shall be sealed.

4.3.5.13 On-site coatingIf the pipes have been ordered bare on the outside from the manufacturer, coating will be done on-site.

It may be effected:• by means of glass cloth coated with coal tar• by means of glass cloth coated with petroleum bitumen• by means of glass cloth coated with adequate plastic tapeThe coating shall adhere perfectly to the pipe.

The coating shall be doubled in areas where the corrosive nature of the soil makes this necessary.

It shall also be doubled:• at crossings of cables and pipes• at the base of high tension electricity pylons• on pipe sections in mud• on pipe sections inside metal sheathing• inside concrete channels• at points where the pipe emerges from the ground.The pipeline may be protected by a covering of suitable materials.



Part 4 : Equipment


4.3.5.14 Inspection of the coatingImmediately before laying in the trench, the insulation of the coating shall be verified in dry weatherby the passage of an insulation tester at 10 000V. Any defect shall be marked and repairedimmediately.

4.3.5.15 Laying in the trenchThe bottom of the trench shall be free from all objects or pebbles capable of damaging the coating. Ifnecessary for example in stony ground, the bottom of the trench shall be provided with a layer ofsand.

The pipeline shall then be laid in the trench by using methods and equipment which ensures that thecoating is not damaged.

When ballasting or anchoring the pipeline in areas where movement of soil can take place, everyprecaution shall be taken to ensure that the protective coating is not damaged.

4.3.5.16 BackfillingBackfilling up to a level of 20 cm above the top of the pipeline shall be effected with care, usingselected uncontaminated materials free from any large or sharp objects which could damage theprotective coating.

4.3.5.17 Warning of underground pipelineA warning plastic grid or tape shall be placed above the buried pipeline in the course of backfilling atall points where this is considered to be necessary.

4.3.5.18 Underground crossing of roadsThese crossings may be made by drilling, thrust boring or open trench according to the size of theroad to be crossed and the nature of the sub-soil and the requirements of the appropriate authorities.

Sheaths may be constructed of asbestos cement, concrete or steel. Care shall be taken in the designand construction of the crossing to ensure the effectiveness and reliability of Cathodic Protection ofthe pipeline, also the ability to withstand without deformation the forces due to filling materials andtraffic loads. See drgs 42, 43, 44 and 45 for typical examples.

4.3.5.19 Underground crossing of railroadsThe provisions described in 4.3.5.18 also apply to railroad crossings. These may be modified by therailroad authorities. See fig 46 and 47 for typical examples.

4.3.5.20 Waterway crossingsThese crossings shall be made in accordance with the requirements of the Authorities concerned.

If the waterway is navigable, it is advisable to provide notices indicating the presence of the pipelineand to prohibit anchoring. For typical example of waterway crossing see Fig 48.

4.3.5.21 Overhead crossingsThe crossings referred to in 4.3.5.18 to 20 may also be made by existing or purpose designed bridges.The design and construction of these crossings shall take into account requirements of Authoritiesconcerned and local conditions affecting safety of the pipelines, e.g. minimum clearance height andassociated warning notices.

4.3.5.22 Crossing or running alongside underground servicesThe spacing and nature of construction shall be such that no mutual interference is to be expected,also that cathodic protection installation and the possibility of repair are preserved.

Any agreement shall be obtained from the owners of the installations concerned.

In the absence of rules the distances shown in Table Xlll may be used for typical examples see Figs 49to 53.



Part 4 : Equipment


Table XIII - CLEARANCE FROM UNDERGROUND SERVICES

Distance in metres between outside lines

Type of Works Crossing Running Parallel

Metal pipework for hydrocarbons,gas, water, etc.

0.60 m 0.60 m

Concrete or fibrocement pipework 0.40 0.40 m

Telecommunication lines 0.40 m 0.40 m

Electricy cables 0.50 m 0.50 m

If these distances, cannot beobserved, protection must beprovided by:

split shells of concrete for a lengthof 2m centred on the point ofcrossing and wrapped in weak

concrete.

split shells of concrete or thick,strong slabs of concrete or

fibrocement. Prefabricated ofcast in situ

Earthing Distance in metres between outside of pipeline andearthing point

Low or medium voltage < (15.kv)

High voltage < 110Kv

Lightening protectors

2

5

10

Anode of cathodic protection to be specified

4.3.5.23 Crossing drainsWhen crossing drains or irrigation systems, special care shall be taken to ensure that their efficiency isnot impaired. For typical example see Fig.51.

4.3.5.24 Proximity of overhead high tension cablesOxygen pipelines are generally laid in industrial regions where the density of high tension electricitylines is also considerable.

Contact shall be made with those responsible for the electrical distribution network when a pipeline isbeing planned. The study to be made shall take account of the characteristics of the electricity lineand of the pipeline as well as the resistivity characteristics of the ground.

Subject to the results of the study, the following minimum distances and measurements are given forguidance for lines up to 110 kV without guard line and above 110 kV with guard line in Table XIV.For typical example see fig 52 and 53.



Part 4 : Equipment


TABLE XIV - CLEARANCES FROM HIGH TENSION OVERHEAD CABLES

ITEM Minimum distancebetween pipeline anditems

Minimum distancebetween pipeline andvertical projection orextreme cable

In Metres In Metres

Between Pipeline and :

H T cable running parallel 10

Base of pylon crossing* special case

10(2)

Overhead electric rail pylon – crossing orrunning parallel

2

Earth connectionfrom the end of the connection

3

Between

Accessories such as valves AND H.T.CABLES

Crossing or running parallel 10

Between

Vent Pipes and H.T. Cable

Crossing or running Parallel

Over 110 kV

Under 100 kV

30

10

Other measures-

For a pipeline in course of construction, sections that are ready welded and situated in the immediatevicinity of a high tension cable shall be earthed.

Above-ground parts of a pipeline that are not covered and that are accessible and could be touched forexample from the ground or from a bridge shall be electrically insulated.

Any conductive connection between the pipeline and high tension line pylons is prohibited.

Neutral conductors or protecting conductors of local electric distribution networks shall not beconnected to the pipeline.

4.3.5.25 Construction in the proximity of high tension cablesIn the course of construction of the pipeline contact with a cable represents the greatest danger topersonnel. Contact between site machinery and a high tension cable shall therefore, be avoided.

A minimum distance of 5 m shall be respected and this distance shall take into account swaying ofcable due to the wind.



Part 4 : Equipment


4.3.5.26 Above-ground sectionsIf the pipeline includes above-ground sections, it will be necessary for the layout of the pipework totake account of possible expansion. If the layout is inadequate for the adsorption of expansion andcontraction it will be necessary to provide either expansion bellows similar to those described insection 3.5.2 or loops arranged either horizontally or vertically upwards. (Loops directed downwardspresent a risk of forming receptacles for dust).

If the above-ground section of a pipeline is under Cathodic Protection, it will be necessary to provideelectrical insulation between the pipeline and its supports.

Special consideration shall be given to environmental and other conditions which may exist, such aslighting, wind, heat, corrosive atmospheres, other installations. Dangerous projected bodies etc.

If the pipe is not under Cathodic Protection, it will be necessary to ensure efficient earthing.

To avoid underlying corrosion, the above ground section should not be externally wrapped with amaterial which has a tendency to deteriorate in the atmosphere. If necessary, existing coating shouldbe removed, and the Darts exposed to the air shall be painted.

4.3.6 Pipeline CleaningIt is essential that a pipeline for oxygen service is in a clean condition in accordance with therequirements of 2.3.

Pipe for construction of the pipeline may be:• Descaled, degreased and passivated at the manufacturer’s works• Descaled, degreased and passivated on site just prior to erection• Uncleaned pipes.The methods of cleaning depend upon the condition of the line, and are described in 2.3.7.

4.3.7 Tests

4.3.7.1 Strength testThe pipeline shall undergo a strength test, preferably pneumatic, using dry, oil-free air or nitrogen soas not to contaminate it.

The pressure shall be increased gradually and time allowed for equalisation of pressure.

The dangers inherent in performing a pneumatic test shall be recognised and adequate precautionstaken. Pneumatic testing cannot be permitted unless the pipes have undergone hydraulic testingbefore installation adn the welds inspected in accordance with the provisions of paragraphs 4.3.5.7 to4.3.5.11 inclusive.

The test pressure, duration and procedure is generally specified by the legislation in force in thecountry where the pipeline is laid. Where such legislation does not apply see 4.1.9.

4.3.7.2 Leak tightness testFollowing the strength test a test for leak tightness shall be carried out, the pressure, duration andprocedure for which shall be as specified by the legislation in the country where the pipeline is laid.In the absence of such legislation, the test duration shall be a minimum of 24 hours.

4.3.7.3 Typical test proceduresTypical examples of performing tests are indicated in figure 54. The records of above tests shall bekept and signed by responsible persons.



Part 4 : Equipment


4.3.8 Cathodic ProtectionIn order to ensure preservation of underground oxygen pipelines, they shall be protected by cathodicprotection. In addition to the passive protection provided by the insulating coating applied to theoutside of the pipes it will be necessary to ensure active protection by sacrifical anode or impressedcurrent systems. The planning of this cathodic protection shall be carried out by specialists who willtake into account chemical or electrical influence of the soil, also the possible effects from otherinstallations.

The potential tappings shall be welded onto the pipeline during laying. Typical example shown infigure 55.

The tappings shall be properly insulated electrically from the soil. Electric cables shall be broughttogether beneath a capped opening or in a terminal box.In the case of highway or railway crossings, typical example of installations are indicated in fig 55.

Tappings on an oxygen pipeline in service will not be done by welding but by means of a collar.Typical example is shown on Fig 57.

4.3.9 Restoration of the TerrainBefore commencement of work, a contractual record of the state of the site shall be made.

The land over which the pipeline has been installed shall be reinstated to the satisfaction of thelandowner or Authorities.

4.3.10 Pipeline IdentificationPipeline identification shall be in accordance with 5.1.

4.3.11 Pre-Commissioning TestsThe pipeline shall have been installed, tested and inspected as described in this code and the relevantspecifications. All defects revealed during inspection and testing shall have been rectified beforeputting into service see 6.2.

4.3.12 As Built DrawingsWhen the pipeline installations completed, the drawings shall be brought up to date in accordancewith any modifications that may have occurred during the installation. The information for updatingof drawings shall be collated as the work proceeds.

4.3.13 Supervision of the Work SiteThe supervising personnel shall ensure that the recommendations of this code are followed and inparticular, shall personally verify :• that the pipes are properly furnished with end plugs when they arrive on the site• that there is nothing left inside the pipes when they are placed alongside for welding• that each section of pipe is properly plugged tight every evening and put on blocks so that water

or moisture cannot penetrate to the inside.• that when work is recommenced each morning, nothing has been placed inside the end pipes.• that in the event of water rising in the trench, for instance as a result of heavy rainfall, everything

possible is done to prevent water from getting into the pipes, whether assembled or not.In addition, supervision during the following operations is recommended.• the passage of the holiday detector• the fitting of pipeline ballast• lowering into the trench• passing pipes through sheathing• insulation coating of the potential tappings welded on the pipeline• the first part of the filling of the trench• introducing and removal of the pigs• testing• final purgingFinally, the welding record shall be inspected to see that it is properly made.



Part 4 : Equipment


Fig 41 BURIED PIPELINESTypical Cross Section of Trench



Part 4 : Equipment


Fig 42 BURIED PIPELINES

Typical Road Crossing without Sleeving or Longitudinal

Utilisation of Roadway Laid in Open Trench

The depth of 1 m for covering is a minimum figure. It may be increased in accordance with therequirements of the authorities or organisations responsible for the road way.



Part 4 : Equipment



Typical Road Crossing in Sheath of Concrete Laying

by Boring or in Open Trench



Part 4 : Equipment



Typical Road Crossing in a Metal Sheath Laying

by Boring or in Open Trench



Part 4 : Equipment



Typical Sheaths: End Seals and Centering Clamps

I D of sheet = (OD of pipe + coating) + 10 cm minimum.

Distance between packing pieces according to nom. dia. of pipe.

Distance between end packing pieces and end of sheath: less than 0.50 m.

Packing pieces and end seals shall be of a type approved by the Site Foreman.

If use is made of packing pieces made up of tarred glass wool, they must be 4 - 5 cm thick and consistmainly of fabric (50 turns per pad) and the tar must be coal tar.

Thickness of steel sheath:

This must be not less than:

4.5 mm up to 175 mm nom. dia. Inclusive5 mm from 175 to 225 mm nom. dia. Inclusive6 mm above nom. dia. 225 mm

The pipelaying company shall check the mechanical strength of the sheath during and after laying.



Part 4 : Equipment



Typical Rail Crossing

Laying by Boring or in Open Trench



Part 4 : Equipment


Fig 47 TYPICAL RAIL CROSSING

With Reinforced Concrete Channels

(Coal Tar Ends Seals)



Part 4 : Equipment



Typical Waterway Crossing Laying in Mud

Note: The length of the part covered by ‘bacula’ (laths) may be increased if the bottom of the trenchis stoney



Part 4 : Equipment



Typical Crossing of an Underground Pipeline

Proximity of pipeline

CROSSING ABOVE OR BELOW

MINIMUM SPACING E

Proximity of pipeline

metallic Non-metallic

Crossing 0.60 m 0.40 m

Running parallel 0.60 m 0.40 m

NOTE 1: The warning device may be omitted if the pipelines are in sheaths or protected bysplit concrete shells.

NOTE 2: E may be increased if required by owner of the pipe being crossed.



Part 4 : Equipment



Typical Crossing of an Underground Electric

Power Cable or Telecommunications Cable

CROSSING ABOVE OR BELOW

Proximity of Cable

Crossing 0.40 m 0.50 mMinimumspacing Running parallel 0.40 m 0.50 m

Reinforcement of coating on bothsides of crossing

3 m 5 m

NOTE 1: The warning device may be omitted if the pipeline is in sheath or protected byconcrete split shells.

NOTE 2: E may be increased if required by the owner of the cable being crossed.



Part 4 : Equipment



Typical crossing of a Stoneware Drain



Part 4 : Equipment


Fig 52 INDICATED DISTANCES BETWEEN PIPELINES AND

HIGH TENSION TRANSMISSION CABLES



Part 4 : Equipment



Proximity of an Earth Connection for an

Electrical Installation of less than 110 kV



Part 4 : Equipment


Fig 54 TRANSPORTATION PIPELINES

Typical Sequence of Tests



Part 4 : Equipment



Details of Fittings at Ends of Sheaths



Part 4 : Equipment



Installations and equipment to be provided for crossings

of highways, railways and waterways

CROSSINGS SHEATHING CAPPEDOPENING

VENT &AERATIONPIPE

CABLE &POTENTIALTAPPING

REMARKS

Railways

Reinforcedconcrete ormetal cement –2m each side ofthe outerboundary or13m the nearestrail if the overallwidth is verylarge

2 per crossing atthe boundary oneach side

2 2 potentialtappings, eachcomprising1 cable of16mm2

& 1 cable of35mm2

Railwaysregulations to beapplied

Concrete, rein-forced concrete,asbestos ormetal cementconduit, ending+ 1m beyond theoverall width atboth ends

As required As required As required

HighwaysMetal sheath ifboringdemanded byHighwaysAuthority. Endsat boundary

1 per sheath ofless than 30m

2 per sheath of30m or more

As required 1 up to 30m (1cable of 16mm2)2 over 30m(each with 1cable of 16mm2

and 1 cable35m2)

If a cappedopening is notprovided, theremust beprovided at eachend:

• a sandfunnel

• a marker

WaterwaysCanals

Waterways or canals are usually crossed in the mud or aerially. In the event of boring theyshall be made as in the case of highways with metal sheathing.

NOTE: A potential tapping be provided at least every 2km



Part 4 : Equipment


Fig 57 POTENTIAL TAPPING BY MEANS OF A CLAMP



Part 4 : Equipment


4.4 Supply Stations

4.4.1 GeneralSupply stations are normally situated on the site of production plants and receive oxygen direct fromcompressors or liquid evaporators.

Downstream of the supply station the transportation pipeline begins. See Fig 1.

4.4.2 FunctionThe normal function is to allocate oxygen to one or more pipelines to suit the pressure and flowrequirements. Metering facilities can also be included. See Fig 2.

4.4.3 ConstructionThe choice of materials and equipment and the construction of the installation shall comply with therecommendations of Parts 2 and 3 and in 4.1 and 4.2 supplemented by the following.

Supply stations comprise stop valves and assemblies similar to those of distribution stations. See 4.5and 4.6.Commissioning is dealt with in Section 6.2.

4.4.4 Special ConsiderationsThree points peculiar to supply stations are emphasised:

a) It is recommended to protect the supply station against backflow of gas from the pipeline.

b) Where liquid supplies the pipeline, precautions shall be taken to prevent low temperature gasor liquid damaging the pipeline.

c) The plant may, in certain cases, receive oxygen from the pipeline via the supply station. Thestation shall then be designed accordingly, in particular it will generally be necessary toprovide a filter.

4.5 Valve Stations

4.5.1 GeneralValve stations are normally located:• at branches of the pipeline• at the exit from plants• at recompression points• at buffer stations• to isolate sections of pipelineIn the case of pipelines of great length, it is recommended that a valve station be installed every 30 to35 km.

4.5.2 FunctionThe primary function of a valve station is to isolate one part of the installation from another.

In addition, it may:• facilitate maintenance operations• enable pressurisation or depressurisation of sections of the pipeline.The station may be designed to function in one direction only but very often may be used to effectseparation in both directions.

4.5.3 ConstructionThe choice of materials and equipment and the construction of the installations shall comply with therecommendations of parts 2 and 3 and in 4.1 and 4.2 supplemented by the following.

Assembly and use of the stations shall take into account the characteristics of the valves, such as thedegree of gas-tightness, gas-tightness in one or both directions, opening speed, etc. See Fig 58 fordiagram of typical installation.



Part 4 : Equipment


If the valve station has a by-pass or a vent to atmosphere, the pipeline and components of these partsshall be of copper or copper alloy. For vent valves see 3.6.1.22 and 4.2.5.13.

Cathodic protection is dealt with in 4.2.5.15.

Commissioning is dealt with in section 6.2.

4.5.4 Special Considerations3-valve block and bleed systems are used to safely isolate sections of pipeline where frequent work iscarried out. Fig 58d. The valves may be automated.It is necessary to fit valves which are gas-tight in both directions under all operating conditions.

Valves which require gas pressure to assist in providing positive shut off (e.g. certain types of gatevalve) shall not be used since any leakage through the upstream valve may split between the ventvalve and the downstream valve into the pipeline being protected.

Fig 58 DIAGRAMS OF TYRES OF VALVE STATION

4.6 Distribution Stations

4.6.1 GeneralNormally, the pipeline system delivers to several distribution stations which are located on or nearcustomer’s premises. (See Fig 2).

Distribution stations are an essential part of the pipeline networks, having components in continuousoperation (control valves, meters).



Part 4 : Equipment


4.6.2 FunctionThe normal function of the station is to control flow and pressure of oxygen prior to distribution to thedelivery points and to meter the quantities supplied.

The other functions are generally connected with safety or operational requirements such as:• filtration• flow limitation• protection against over-pressure• venting• emergency shut downThe components and functions vary from case to case and are determined by careful analysis of therequirements of the station.

4.6.3 ConstructionThe choice of materials and equipment and the construction of installations should comply with therecommendations of parts 2 and 3 and in 4.1 and 4.2 supplemented by the following.Commissioning is dealt with in section 6.2.

4.6.4 Special ConsiderationsFor reasons of safety, certain uses of oxygen (e.g. chemical and petrochemical) demand a continuoussupply without interruption. It is possibly necessary in such cases to provide 2 parallel systems withautomatic transfer.

In such cases, security of electric or pneumatic services shall also be ensured.

4.6.5 Protection of Customers NetworkCare shall be taken to ensure that user’s network can accept the increase in pressure due to theoperational characteristics of the distribution station.

4.7 Recompression StationsRecompression stations are used to compensate for loss of pressure in the pipeline or to supply at ahigher pressure than the pipeline.

Such stations normally include:• intake station comprising filtration and regulation of flow and pressure. See 4.6• supply station. See 4.4• general by-passFor the installation of recompression machines, the following documents may be consulted:• For centrifugal compressors.

“Turbo compressors for Oxygen Service” published by the I.C.C.for oxygen turbocompressor safety.

• For reciprocating compressors:“Code of Practice for Reciprocating Oxygen Compressors”published by the Industrial Cases Committee under No 10/81

4.8 Pressure Reduction StationsPressure reduction stations are used for supplying network branches at a pressure which is lower thanthat of the main pipeline.

These stations are similar to distribution stations but are usually without metering.

They shall comply with 4.6.



Part 4 : Equipment


4.9 Storage Vessels (Buffers)

4.9.1 GeneralBuffers may be used:

a) to provide a limited reserve supply, normally via a regulating station. See 4.6.

b) to provide for intermittent use for continuous production (as in the case of oxygen forsteelworks converters). The buffer being connected permanently to the network.

4.9.2 Construction of BuffersThe choice of materials and equipment and the construction of installations shall comply with therecommendations of Parts 2 and 3 and in 4.1 and 4.2 supplemented by the following.Commissioning is dealt with in Section 6.2.

4.9.3 Design

4.9.3.1 Regulations and designBuffers for oxygen storage shall be designed and constructed in accordance with the pressure vesselregulations in force in the country of use.

The choice of materials, the design and the calculations must take into account the cyclic variations ofpressure.

Design shall also take account of additional weight during hydrostatic testing.

4.9.3.2 Design pressureThe design pressure shall be selected as a function of the network design conditions.

(buffers shall be protected by a safety valve).

4.9.3.3 Piping connectionsTo prevent entrainment of dust and impurities, inlet, outlet and vent connections on vessels shall besituated at a height of at least 0.5 diameter of the vessel above the bottom of the vessel.

If inlet, outlet or vent pipes pass through the base, they shall extend inside the vessel to a minimumheight of D/6 (D = inside diameter of the vessel).

The lowest part of the vessel shall include a connection (100 to 200mm dia) designed for easyremoval of any deposits during inspection that may possibly have collected at the bottom of thevessel.

4.9.3.4 Flange connectionsFlanges for pipe connections and manholes etc. shall comply with the appropriate regulations andrecommendations of 3.4.1.

4.9.3.5 Stop valves and vent valvesStop valves and vent valves shall comply with the recommendations in section 3.6.1

4.9.3.6 Safety valvesSafety valves and their installation shall comply with the section 3.6.7 and item 4.2.5.4.

4.9.3.7 ManholesLarge capacity buffers and those that are installed vertically should have two manholes, one at thebottom and one at the top of the vessel, to facilitate inspection and maintenance and in the event ofsuch work they will facilitate ventilation of the interior atmosphere.

4.9.3.8 Ladders and attachmentsLarge vertical vessels may be equipped with outside ladders to give access to manholes and withinside ladders or spurs for inspection and maintenance.

Any internal attachments should be made from solid bar welded to the wall of the vessel to avoidmovement and vibration.

Permanent inside ladders constructed by mechanical assembly are prohibited.



Part 4 : Equipment


4.9.4 Inspection and Cleaning

4.9.4.1 Inspection and testsNational regulations generally require for inspection and material certificate for the Construction ofpressure vessels, as well as for hydraulic tests.

Hydraulic strength tests shall be carried out with potable (drinking) water free from oil or grease.

4.9.4.2 CleaningAfter hydraulic testing and drying with clean oil free dry nitrogen or air, the interior shall be cleanedin accordance with the recommendations of 2.3.5. The cleanliness shall be verified according to therecommendations of 2.3.8.3. Sand blasting is recommended, followed by cleaning in accordance with2.3.5.4.

If necessary, traces of oil or grease shall be removed by the use of a solvent recommended in section2.2.2 and a clean rag according to 2.2.4.5.

After cleaning, the vessel shall be filled with a nitrogen and all connections carefully sealed inaccordance with the recommendations of 2.3.9.

4.9.4.3 External finishPainting of the outside shall not be carried out until all the connections of the vessel have been closed.

4.9.5 Installation

4.9.5.1 Foundations and supportsSupports for buffers may be made of metal frames or reinforced concrete.

They shall be solidly anchored to stablp foundations.

The design of supports and foundations shall be based on-:• The weight of the vessel when filled with water in case of hydraulic testing in situ• Wind loading• The expansion and contraction of horizontal vesselsThe area of contact between the buffer and supports shall be designed to avoid the possibility ofhidden corrosion.

4.9.5.2 Valves and controlsWhere valves and controls are installed in conjunction with oxygen buffers the recommendations of4.2.1 and 4.2.2 should be observed.



Part 5 : Signs and Information


The Transportation and Distribution of Oxygen by PipelinePart 5 : Signs and Information

IGC 13/82/E











SECTION 5 : SIGNS AND INFORMATION .....................................................................................................3

5.1 PIPELINE ROUTE MARKERS.......................................................................................................................35.1.1 Purpose..............................................................................................................................................35.1.2 Marker Posts......................................................................................................................................35.1.3 Markers for Aerial Inspection............................................................................................................35.1.4 Underground Markers .......................................................................................................................35.1.5 Above Ground Markers .....................................................................................................................35.1.6 Pipeline Corridors .............................................................................................................................3

5.2 STATION SIGNS .........................................................................................................................................45.2.1 Purpose..............................................................................................................................................45.2.2 General Sign ......................................................................................................................................45.2.3 Instructions to Operators...................................................................................................................45.2.4 Safety Signs........................................................................................................................................45.2.5 Colour of Sign....................................................................................................................................4

5.3 RECORDS ..................................................................................................................................................45.3.1 Purpose..............................................................................................................................................45.3.2 Agreement Documents .......................................................................................................................45.3.3 Design and Inspection Documents ....................................................................................................55.3.4 Design Drawings “As Built” .............................................................................................................55.3.5 Modifications .....................................................................................................................................55.3.6 Records to Authorities .......................................................................................................................5

5.4 LAND ADMINISTRATION............................................................................................................................55.4.1 Purpose..............................................................................................................................................55.4.2 Action.................................................................................................................................................5

5.5 INFORMATION - INSPECTION - EMERGENCY PLAN ....................................................................................65.5.1 Purpose..............................................................................................................................................65.5.2 Information ........................................................................................................................................65.5.3 Inspection ..........................................................................................................................................6

5.5.3.1 Regular inspection ........................................................................................................................................65.5.3.2 Special information ......................................................................................................................................6

5.5.4 Emergency Plan.................................................................................................................................75.5.4.1 Use of the emergency plan ...........................................................................................................................75.5.4.2 Content .........................................................................................................................................................7





SECTION 5 : SIGNS AND INFORMATION

5.1 Pipeline Route Markers

5.1.1 PurposeWhere pipelines are underground it is necessary to provide markers to identify the route, to facilitateinspection and to warn any others likely to undertake operations in the immediate vicinity.

This marking is important, to prevent damage by civil engineering machinery during diggingoperations.

5.1.2 Marker PostsMarker posts indicate at ground level existence of the installation, and shall be provided at intervals(eg 200 to 500 meters) and along the entire length of the buried pipeline.

Locations• changes of direction• crossings, roadways, railways and waterways.• the point where pipelines or other underground services cross.• special points.Marker plates shall be fixed to the marker posts or other suitable supports and be positioned so thatthey can be easily found.

A typical marker plate is illustrated in fig 59.

This plate indicates:• the name of the owner• oxygen• pipeline diameter and pressure• pipeline distance from the marker• the depth at which the pipeline is buried.Placing of the markers shall be properly carried out so as not to be effected by ground movements.Positions shall be chosen with a view to avoiding damage or destruction of the-markers. They shallnot constitute an obstacle to the use of the land.The position of markers shall be indicated, on the appropriate survey map for the installation.

5.1.3 Markers for Aerial InspectionIn the event of inspection by aerial survey it is advisable to provide along the length of the pipelinemarkers that can be spotted from a height of approximately 200 to 300 meters.

5.1.4 Underground MarkersIn certain areas it is advisable to place a warning grid or tape over the pipeline. (see 4.3.5.17).

In particular areas the grid or tape may be replaced by concrete slabs which in addition to markingprovides protection.

5.1.5 Above Ground MarkersAbove ground section of pipeline shall be clearly identified by suitable markings. See 5.2.5.

5.1.6 Pipeline CorridorsIn some highly industrialised areas pipelines may have to make use of reserved pipeline corridors.

In this case marking shall be suitable for the corridor and it will be necessary to comply with the rulesimposed





5.2 Station Signs

5.2.1 PurposeThe purpose of these signs is to provide:• warning of the type of installation• information concerning safety• instructions to operators

5.2.2 General SignThis sign should indicate:• the name of the owner• the responsible local branch• the telephone number to call• the fluid transported (oxygen)• and identification of station, precise location. The sign may indicate the hospital for emergency

service.This sign shall be placed in a prominent external position.

5.2.3 Instructions to OperatorsA simplified diagram of the station shall be displayed, with a list of manual operations for putting intooperation and shut down, for typical example see fig 60.

The diagram shall be located inside, near the main entrance, or inside the control room in case ofdistribution stations.

5.2.4 Safety SignsSafety signs draw attention to prohibitions and recommendations• Prohibitions• Access• Smoking• Use of naked flames• Use of oil and grease• Recommendations• Protective equipmentFor typical signs see fig 61.

These signs shall be placed in a prominent position at the entrance to the station and if necessary atseveral locations in the case of large stations.

5.2.5 Colour of SignStandard or statutory colours shall be used.

5.3 Records

5.3.1 PurposePipeline installations are recorded on appropriate survey maps, and records shall also indicate whereuse is made of public or private properties and indicate where rules are imposed.

These records shall be readily available for reference.

5.3.2 Agreement DocumentsThese documents are:• way leave agreements for the pipeline and ancillary installations:• permission to instal pipeline.• permission to operate pipeline.The form of the agreements will depend upon the regulations in force.





5.3.3 Design and Inspection DocumentsThe records shall include the documents previously mentioned in the Code, such as:• design calculations• test certificates and inspection reports• material conformity certificates• welder approval certificates• weld test document (X-ray)• pressure test certificates

5.3.4 Design Drawings “As Built”The final design drawings entered in the records shall take into account any modifications made in thecourse of installation. See 4.3.12.

The records shall comprise:• a route map• identification of property owners• ordinance survey maps with reference points, distances, outline diagrams etc• plans of crossings of:

• main highways and motorways• secondary roads• railways, rivers and canals• private roadways

• location of marker posts• location of cathodic protection test points• ground contours• design drawing of special installations with supporting calculations• drawings showing design and location of station including cathodic protection

5.3.5 ModificationsDetails of all modifications and repairs, shall be incorporated into the drawings and records.

5.3.6 Records to AuthoritiesDocuments required shall be forwarded to the authorities as necessary.

5.4 Land Administration

5.4.1 PurposeThe ability to install the pipeline may be subject to numerous land agreements. These agreements arefrequently subject to special clauses and require administrative procedure of a legal nature, thepurpose of which is to safeguard the installation.

5.4.2 ActionThe purpose of initial action is to legalise the agreements.

Later it is mainly a matter of keeping up with modifications of land ownership due to purchases,transfer, regroupings and road or rail projects and other developments.

It is also important to ensure a constant review of all works and developments planned in the vicinityof the installations.

This is necessary to safeguard the interests of the owner of the installation and impose safetyconditions.

This procedure is also connected with the problems of supervision dealt with in 5.5 and with theproblems of maintenance modifications dealt with in 6.4 and 6.5.





5.5 Information - Inspection - Emergency Plan

5.5.1 PurposeTo reduce the number of accidents due to ignorance of the existence of pipeline networks. Byeffective information and inspection. The object of the emergency plan is to define and implementactions following any emergency.

5.5.2 InformationIn the case of large or complex pipeline installations it is useful to prepare a map showing the routeand the names of the areas traversed. Mention may also be made of:• the dangers that may result from damage to an oxygen pipeline by earth - moving equipment.• An instruction to contact pipeline operator where work is to be carried out in close proximity to

the pipeline.• The address and telephone number of the place to contact for information.It is advisable to implement procedures, which ensure that where necessary information is passed toall who may be concerned such as:• Public utilities (fire, gas, electric, water and telephone)• Local authorities concerned• Companies and other land owners traversed• Others (civil engineers, lawyers and surveyors)

5.5.3 InspectionA distinction is made between regular and occasional inspection. Certain technical aspects ofinspection are dealt with more fully in section 6 of the Code.

5.5.3.1 Regular inspectionThe pipeline should be inspected on foot at least once a year.

Other complimentary inspections can be carried out by car, plane or helicopter.

A general inspection of the route should be made every 6 months, and more often in areas subject tofrequent work by others or earth subsidence and anomalies reported.

The inspector shall:• in case of immediate and obvious risk, indicate measures to be taken to avoid an accident.give the contractor the address of the person responsible for the pipeline.• inform his company of any anomalies of work being carried out by others in the vicinity of the

pipeline.The inspector’s report shall include the following information:• any damage to the installations,

• pipelines - leaks, corrosion, physical damage, exposure of buried piping.• accessories, sheathing, inspection covers, cathodic protection, markers.• supports and supporting structures

• earth movements (especially in mining areas) at river banks or mountains.• works in progress along the route adjacent to the pipeline.• changes liable to affect the installations, planting of trees, area development industrial or private.• particular attention shall be given to areas where leaks could enter confined spaces, i.e. sewers,

and caves.Following inspections it may be necessary to update survey maps.

5.5.3.2 Special informationInspection is recommended when works are being carried out in the immediate vicinity of theinstallation where on-site co-operation and guidance are necessary.

It is also advisable to send the contractor recommendations concerning precautions to be observed.This last point is dealt with in 6.1.





5.5.4 Emergency Plan

5.5.4.1 Use of the emergency planAn emergency plan is recommended for large scale or complex systems, it should contain essentialidentification for the network and emergency actions to be taken.

The emergency plan should be at the disposal of the system oxygen plant managers of maintenancemanagers and of other concerned with the operation of the pipelines.

In certain cases this document may also be required by the National Authorities, Local Authorities,police, fire department and safety organisations etc:

5.5.4.2 ContentThe emergency plan shall comprise the following information:• a general description of the system• action to be taken in case of emergency

• persons to contact• action to be initiated.

• the area addresses and telephone numbers of:• Companv plant and personnel responsible• the police• the fire brigade• the hospital authorities• the customers

• description of the system:• a detailed map of the system• details of location and access to stations• a flow diagram of the system• design specification, diameter, pressure etc• flow diagram of the stations

• the means of taking action:• the location of emergency equipment and vehicles• the addresses and telephone numbers of contractors trained in emergency operations• emergency instructions• a reminder of the main safety rules for oxygen oxygen• data sheet

According to circumstances the system may be divided into areas and documented accordingly.

The emergency plan shall be kept up-to-date.



Part 6 : Operations and Maintenance


The Transportation and Distribution of Oxygen by PipelinePart 6 : Operations and Maintenance

IGC 13/82/E











SECTION 6 : OPERATIONS AND MAINTENANCE ......................................................................................3

6.1 GENERAL SAFETY RULES..................................................................................................................36.1.1 Basic Rules ........................................................................................................................................3

6.1.1.1 Operations and maintenance personnel ........................................................................................................36.1.1.2 Operation of stop valves ...............................................................................................................................36.1.1.3 Cutting and welding work ............................................................................................................................46.1.1.4 Rules and recommendations - general and special .......................................................................................4

6.1.2 Protection Against Oxygen Enrichment & Deficiency.......................................................................56.1.2.1 Limit thresholds............................................................................................................................................56.1.2.2 Measurement and control of oxygen concentration......................................................................................56.1.2.3 Isolation of circuits .......................................................................................................................................6

6.1.2.3.1 General rules ......................................................................................................................... 66.1.2.3.2 Practical points to note .......................................................................................................... 6

6.1.2.4 Venting to atmosphere, depressurising, purging...........................................................................................76.1.2.4.1 Venting .................................................................................................................................. 76.1.2.4.2 Depressurising....................................................................................................................... 76.1.2.4.3 Purging .................................................................................................................................. 76.1.2.4.4 Extraction of residual oxygen from pipelines........................................................................ 76.1.2.4.5 Ventilation............................................................................................................................. 7

6.1.2.5 Work inside buildings...................................................................................................................................76.1.2.6 Work within storage vessels .........................................................................................................................76.1.2.7 Work in trenches ..........................................................................................................................................8

6.1.3 Clothing and Cleanliness of the Hands .............................................................................................86.1.3.1 Clothing........................................................................................................................................................8

6.1.4 Tools and Handling ...........................................................................................................................96.1.4.1 Tools.............................................................................................................................................................96.1.4.2 Handling.......................................................................................................................................................9

6.1.5 Preparation for Work ........................................................................................................................96.1.6 Co-ordination of Third Party Work ...................................................................................................9

6.2 COMMISSIONING .....................................................................................................................................106.2.1 Compliance With Recommendations ...............................................................................................106.2.2 Inspection Before Commissioning of Installations ..........................................................................106.2.3 Pressurising .....................................................................................................................................106.2.4 Nitrogen Pockets..............................................................................................................................10

6.3 OPERATION .............................................................................................................................................116.3.1 Compliance with Recommendations................................................................................................116.3.2 Operating, Alarm and Tripping Devices .........................................................................................116.3.3 Filter Cleaning ................................................................................................................................11

6.4 MAINTENANCE AND INSPECTION ............................................................................................................116.4.1 Compliance with Recommendations................................................................................................116.4.2. Pipeline Maintenance ......................................................................................................................126.4.3 Component Maintenance .................................................................................................................126.4.4 Special Inspections ..........................................................................................................................12

6.4.4.1 Severely stressed areas of buried pipelines.................................................................................................126.4.4.2 Effect of an incident ...................................................................................................................................12

6.4.5 Locating a Leak on an Underground System...................................................................................136.4.6 Drying a Pipeline.............................................................................................................................136.4.7 Programme of Preventive Maintenance and Inspections ................................................................13

6.5 MODIFICATIONS ......................................................................................................................................136.6 WITHDRAWAL FROM, OR CHANGE OF, SERVICE .....................................................................................14

6.6.1 Compliance with Recommendations................................................................................................146.6.2 Possible Cases .................................................................................................................................14

6.6.2.1 Taking out of service ..................................................................................................................................146.6.2.2 Removal of pipeline ...................................................................................................................................146.6.2.3 Changing from oxygen to another gas........................................................................................................146.6.2.4 Change to oxygen service from another product ........................................................................................14





SECTION 6 : OPERATIONS AND MAINTENANCEIn the preceding sections the choice of equipment and the design of the installations have beenexamined. Where the precautions to be taken relate to the safe use of the installation with oxygen.

However when the installations are taken into use, dangers do exist and these are dealt with togetherwith precautions necessary for the safe operation and maintenance as well as inspection.

6.1 GENERAL SAFETY RULES

6.1.1 Basic Rules

6.1.1.1 Operations and maintenance personnelIn accordance with 1.7.3, personnel assigned to the operation and maintenance of oxygen installationsshall have received adequate training.

Personnel shall have a good knowledge of the location and design of the installations, and shall begiven operation and safety instructions in writing. Main safety instructions shall be displayed at theplaces of work (see 5.2).

In the event of repair work carried out by outside contractors such personnel shall be supervised toensure that safe operational procedures are observed.

No operation involving risk shall be entrusted to any single person. An assistant acting as observershall in case of accident be able to raise the alarm and give assistance or first aid.

6.1.1.2 Operation of stop valvesWe have seen in 1.3.1.5 that excessive gas velocity and in 1.4.2.1.6 that high adiabatic compressionmay be the cause of heating that may lead to ignition. High values of ∆P are causes of thesephenomena.

Although control valves are designed to operate with high ∆P the same is not true of ordinary stopvalves, which shall not be used as throttle valves.

It is not advisable to open a stop valve in the presence of a high ∆P because of throttling and highvelocity effects. See 4.2.5.1.3.

It is always desirable:• To ensure a slow and controlled increase in pressure.• to operate stop valves with:-

• the pressure equalised on both sides• the gas flow at rest.

∆P = difference in pressure between upstream and downstream of components.

These handling precautions shall be observed mainly when the system is taken into service ormodified.

Modifications of the system are understood to mean:• modifications made to the installations such as the removal, change or addition of equipment.• putting into service any new oxygen supply.• modification to the operating conditions of the pipeline system:

• change inflow pattern, involving increased velocities and the possible displacement of dustand particles.

• alteration of pressure conditions.• change of flow direction.

There are some case





that do not fall within these basic principles. e.g.

a) Operation of stop valves isolating a component

When filters are installed in parallel it is necessary to inspect and clean without stoppingoperations.

The first valve to be closed shall be the one downstream of the filter in use which is in thefiltered part of the gas flow. By contrast when opening, the upstream valve shall be openingfirst.

b) Closure of an emergency valve

Some systems may be equipped with automatic valves that can be closed automatically byremote control in the event of an incident.

Re-opening of these valves, however, shall be carried out locally. Following pressureequalisation. Stop valves that are rarely used shall be operated periodically to test their properfunctioning, e.g. every six months.

6.1.1.3 Cutting and welding workNo cutting or welding work shall be undertaken on pipelines and components containing oxygen.

The only exceptions is the drilling of small holes on depressurised pipelines. This may be carried outby specially trained personnel using special procedures and equipment.

6.1.1.4 Rules and recommendations - general and specialThese are due to the:• specific properties of oxygen• fact that the gas is under pressure• nature of the worka) General Rules

The following are the basic general rules covered by this code:• only trained personnel allowed to operate• observance of safety zones• observance of the rules in safety zones such as:

• no smoking• no naked flames

• requirement for materials and assembly of components• observance at all times of the two fundamental, compulsory requirements:

• NO OIL OR GREASE• SCRUPULOUS CLEANLINESS

• ensure that installations remain clean, that premises are not encumbered with unnecessaryobjects and that exits remain clear.

• report every anomaly• during inspections or work on the installation any anomalies (unusual noise, change in the

appearance of paint, heating, soke) shall be investigated. If there is any doubt concerningits origin, personnel shall leave the area immediately without attemtping to investigatefurther and report to responsible person.





b) Special Rules

Other recommendations:• For night work, provide appropriate lighting in the work area and access.• In stations, the lighting shall be switched on even during work in the daytime, to ensure

adequate lighting in case of incident.• For work at height, adequate safety precautions shall be provided.• When dismantling, avoid the use of penetrating products, or if they do have to be used,

ensure effective cleaning before asseirbly.• The re-tightening of components or couplings in a circuit tinder pressure shall be

forbidden. Circuit shall be depressurised before this work is carried out.• For any work on site and for cutting, grinding and welding operations, provide the

relevant protective equipment.• Under no circumstances shall oxygen installations be used as an earth return during

welding operations.• Open ends of pipelines shall be sealed at all times unless work is in progress.• Temporary pipes or components whose strength is unknown shall not be used.• For supply of blowing or purging gas, use degreased, clean pipelines.• Wlnen acid, caustic materials or solvents are used, provide appropriate protection (face

shield, safety goggles, gloves, boots, aprons) and the necessary ventilation.• Remember that chlorinated solvents can decompose and produce phosgene when heated or

subjected to ultra violet rays, e.g. when welding.• Wherever possible, work requiring contact with the pipelines or their components shall be

avoided during electric storms.• Contact with cathodic protection installations shall be forbidden during electric storms.

6.1.2 Protection Against Oxygen Enrichment & Deficiency

6.1.2.1 Limit thresholdsWe have in 1.3.2 indicated the dangers caused by oxygen-enriched atmospheres (danger of ignition)and in 1.3.4.3 those caused by oxygen-deficient atmospheres (danger of asphyxia).

As a general rule there is no reason for working in areas where the atmosphere is not or cannot be thesame as that usual in air, namely 21% oxygen, any deviation on either side of 21% constitutes ananomaly.

When measuring level of oxygen the accuracy of measuring instruments shall be borne in mind:

The following warning thresholds are recommended:

For oxygen enrichment 22%

For oxygen deficiency 19%

The concentration of oxygen maybe localised, neighbouring areas may be more enriched or moredeficient, a fact which urges care in taking measurements.

Special care shall be taken in the case of work being carried out, inside buildings, in enclosed areasand in holes or trenches. Work in the open air generally presents little danger.

Oxygen at the same temperature as air and nitrogen when its temperature is lower than air is heavierand therefore tends to accumulate at low levels.

6.1.2.2 Measurement and control of oxygen concentrationVariations in the oxygen concentration in the atmosphere, cannot be detected by the senses.

The use of combustion tests is strictly forbidden.

It is necessary in the case of operations requiring control of the atmosphere, to be equipped withinstruments for measuring the concentration. Measurement of the concentration shall be undertakenat one or more points:• In the pipeline upstream of the work position.• In the pipeline downstream of the work position.• In the work area, at carefully selected points.





There are many types of portable instruments on the market, selection shall be made with regard to thefollowing points.• accurate measurement• rapid, response• audible alarm signal may be incorporated• suitable for use on site• robust• suitable for inclement weather• lockable settings• accuracy and response• not affected by temperature• not sensitive to humidity• not sensitive to positionInstruments shall be subjected to regular inspection and calibration.

Care should be taken at altitude to reset analysers to compensate for change in atmospheric pressure.

6.1.2.3 Isolation of circuits6.1.2.3.1 General rules

In 1.4.6 and 1.4.8 the main causes of oxygen enrichment or deficiency are indicated.

No repair work may be carried out on a pipeline or pipeline system unless the work point is reliablyisolated.

In the case of maintenance during operation such as the cleaning of a filter or replacement of acomponent, the closure of leak-tight isolation valves is acceptable. A non-return valve cannot beconsidered as isolation component.

In the case of works involving cutting, shaping or welding, there shall be a positive guarantee ofisolation. One of the following shall be considered.• Complete disconnection and isolation from the system• The fitting of blind flanges• Three valve block and bleed system see 4.5.4.• The closure of a valve and insertion of a sealing balloon with a vent to atmosphere in between, or

other procedures adaptable to the problems of large networks.

6.1.2.3.2 Practical points to note

The removal of a component or of a section of pipe without sealing off the pipeline is generallyinsufficient for the protection of a circuit.

• Existing leaks may enrich the atmosphere in the area concerned.• The gas may also pass from the upstream section to the downstream section if chimney effect

is established in the downstream section.The site layout shall be studied so that preventive action can be taken to avoid oxygen enrichment ordeficiency due to chimney effect or wind.

In the case of a long pipeline of gas rapidly, emptied of gas, and isolated upstream an oxygen flow ispossible after emptying for the following reasons:• Residual gas which has been cooled during the depressurisation warms up and is emitted at the

open end. Heating may be caused by the ground, or by the sun on above-ground sections.• Changes in level may produce a chimney effect.• Variations of atmospheric pressure or density may cause flow to take place.• These three effects may be cumulative.It should also be noted that:• If oxygen is used to operate equipment in the stations these circuits shall be considered as a

possible cause of leakage with enrichment of the atmosphere.• Oxygen may also originate from the improper use of equipment (heating, cutting and welding

torches).





6.1.2.4 Venting to atmosphere, depressurising, purging6.1.2.4.1 Venting

Venting of large quantities of oxygen into the atmosphere shall be carried out under clearly defined,controlled conditions for valves used for venting see 3.6.1.22.

Venting procedures shall ensure that oxygen is removed to a point where it ceases to be dangerous topersonnel or surroundings. Combustion engines and compressors are particularly dangerous in anoxygen-enriched atmosphere.

6.1.2.4.2 Depressurising

Depressurising small volumes of gas shall be carried out by means of suitable components (3.6.1.19 to21). For valve stations see 3.6.1.22 and 4.5.3.

Depressurisation procedures shall be clearly defined.

Depressurisation by the loosening of bolts, on flanges or couplings is forbidden.

6.1.2.4.3 Purging

The purging of a pipeline ensures the removal of oxygen from a system. This purging may be carriedout with dry oil free nitrogen or air.If nitrogen is used for purging care should be taken see 6.1.2.

6.1.2.4.4 Extraction of residual oxygen from pipelines

Consideration may be given to the protection of a working area, by extraction using suction devices inthe pipeline.

This method requires special procedures and equipment and shall therefore be used only by speciallytrained and well-informed personnel.

6.1.2.4.5 Ventilation

Ventilation of an enclosure or trench may be effected by extraction or preferrably by introducing freshair.

6.1.2.5 Work inside buildingsThe dangers of oxygen enrichment or deficiency are greater inside a building than in the open air.

If a big leakage is found inside a building, the following steps shall be taken in the order given:• Evacuate the building• Do not enter• Shut down the installation• Isolate the installation• Depressurise the installation• Ventilate the building• Test the atmosphere before entering the building continue testing during maintenance• Repair the leak

6.1.2.6 Work within storage vesselsIt may be necessary to undertake work inside large vessels such as buffers (see 4.9).

Before work is started the vessel shall be isolated, purged and its atmosphere tested. If necessarycontinuous analysis shall be carried out, and a continuous supply of dry oil free air maintained.





6.1.2.7 Work in trenchesWork at the bottom of an excavation may be necessary on oxygen pipeline systems for repair ormodifications, fig 76.

The excavation is a low point without cross ventilation, and represents a likely place for the formationof a dangerous atmosphere.

In addition, it is a place where use is made of torches, grinders and welding equipment which providesources of ignition.

In any trench where there is the risk of oxygen enrichment or deficiency of the atmosphere, thefollowing precautions shall be taken.• The trench shall be constructed so as to permit the rapid evacuation of personnel by means of:

• sloping sides• metal ladders• continuous analysis of the atmosphere shall be made.

• A person in charge of the work shall be stationed at the edge of the trench. It shall be his duty• to supervise the proper progress of operations• to make any decision in unforeseen circumstances• to ensure correct composition of the atmosphere• to be ready to act with fire fighting equipment. See 7.2 & 7.4.

• If necessary, ventilation shall be provided.

Fig.59 WORKING IN A TRENCH

6.1.3 Clothing and Cleanliness of the Hands

6.1.3.1 ClothingWork clothes, gloves and footware shall be in good condition, free from fluff, clean and withoutgrease stains.

Clothing should be light in colour.

Clothes should be well-fitting but easy to remove. They should not have gaping pockets and trouserlegs should not have turnups. Pockets should preferably have zip fasteners.

Loose material and flowing garments are more easily impregnated with oxygen.

Closely woven cotton and wool are recommended. Leather which has been “fire-proofed” is also agood product (see 1.3.2.).

Certain synthetic fabrics made to be fire resistant may also be used provided tests have demonstratedtheir safe use.

Synthetic materials are generally less flammable but when they are ignited they melt, stick to the skinand may contaminate any wounds.

Synthetic fabrics are therefore not recommended for undergarments.





6.1.4 Tools and Handling

6.1.4.1 ToolsThe tools and accessories used (work benches, supports) shall be in good condition and clean, freefrom oil and grease.

It is not necessary to use anti-sparking tools.

If mechanical tools comprising lubricated elements are used (pulley blocks, portable grinders anddrills, etc), they shall not have any seepage or ejection of oil or grease.

For cleaning cloths see 2.2.4.5.

For blowing gases see 2.2.5.

Regarding the maintenance of components it is recommended that a specific place be reserved in themaintenance workshop for equipment used with oxygen. The bench can then be covered with lightcoloured paper which is periodically changed or when contaminated.

6.1.4.2 HandlingThe handling of components and sections of pipeline shall be carried out with care, making sure thatequipment and especially the faces of flange joints are not damaged. The use of slings isrecommended.

If mechanical handling equipment is necessary, any possible pollution by oil from cables, gears orother sources of oil or grease shall be avoided.

6.1.5 Preparation for WorkPrior to commencement of maintenance or modification work on oxygen pipeline installations,especially long or complex installations, a survey shall be carried out and the method of completingthe work procedures planned, programmed, the equipment required established and safety precautionsto be implemented.• shutdown procedures• work• start-upCare shall be taken to ensure that work by, or affecting others, is co-ordinated.

All personnel concerned with the work should be made familiar with the programme and supervisedto verify that the work is carried out correctly, safely and to the programme.

Any deviation from the planned work shall be properly authorised by the person in charge of thework. On the spot decisions by other individuals should be avoided.Work permits shall be prepared and implemented as necessary.

6.1.6 Co-ordination of Third Party WorkCo-ordination shall be carried out between the owner and third parties who have to execute operationsnear to pipelines or stations of an oxygen system and a work plan agreed.

In 5 we have described the importance of notification of the work and in 5.5.2 the information it isnecessary to provide.

If any work such as digging, pipelaying or construction is to be carried out in the vicinity of thepipeline with the possible need to expose it, a note shall be sent to the third party with a plan of theroute.





This note shall specify:• a description of the oxygen system• the need to accurately locate and identify the route of the pipeline.• a request for the third party to communicate the exact date for the work so that a representative of

the owner may be present to check the pegging out and the work itself.• the precautions and measures to be observed during the work:

• if trial holes are necessary, they shall be made manually.• mechanical digging work shall be supervised and prohibited in the immediate vicinity of the

pipeline.• Necessary precautions to be taken for the passage of heavy machines or equipment over the

pipelines.• the conditions for backfilling and marking• a request for details of the third party work so that record drawings can be updated.

• the distances to be observed from the oxygen pipeline, see 4.3.5. - 22, 23 and 24• the requirements of cathodic protectionThe note should also give a brief indication of the dangers associated with oxygen systems.

It shall specify that the drawing provided is indicative only and that verification may be necessary.Dimensions given may be inaccurate as a result of alterations following road straightening, new roads,demolitions, land boundary changes, the laying of new system, etc. For these reasons preliminaryroute identification is often necessary.

6.2 Commissioning

6.2.1 Compliance With RecommendationsCommissioning operations should be carried out in accordance with the recommendations of 6.1 andthe special recommendations below.

Commissioning instructions provided by suppliers and designers of equipment and installations shallbe observed.

6.2.2 Inspection Before Commissioning of InstallationsBefore any installations: pipelines valve stations, distribution stations, buffers, etc., are commissionedit is essential to ensure that the installation is correctly installed, tested and clean. See 4.2.8.

In the event of uncertainty with regard to cleanliness it will be necessary to effect control bydismantling and inspection. it may then be necessary to proceed to the cleaning or blowing demanded.

The sequence of dismantling and blowing shall ensure that purge gas blown through pipes that havenot been cleaned does not pass through valves and components. In advancing section by section, thevalves and components should be removed and replaced by spools before blowing commences.

6.2.3 PressurisingPressurising of the installation shall be carried out progressively using throttling or by-pass valvesfitted on the installation. If an installation contains several stop valves in series all these valves shallbe opened using one valve only to introduce the oxygen.

If the installation includes an automatic or expansion valve (3.6.2. or 3.6.4) this valve may be used.

6.2.4 Nitrogen PocketsWhen nitrogen has been used, pockets may remain in the pipeline in spite of blowing through.

For this reason medical installations should not be connected to industrial oxygen distributionsystems.





6.3 Operation

6.3.1 Compliance with RecommendationsInstallations shall be operated in accordance with the recommendations of 6.1 and 6.2 and the specialrecommendations below.

Operating instructions provided by suppliers and designers of equipment and installations shall beobserved.

6.3.2 Operating, Alarm and Tripping DevicesIn normal service all the safety devices shall be operational: they shall not be put out of service, orsettings altered. They shall be periodically tested.

When an installation has been shut down by a tripping device it shall not be returned to service untilthe reason for tripping has been determined and any faults corrected.

6.3.3 Filter CleaningThe cleaning of filters demands special care, to prevent dust collected in the filter being returned tothe system.

In order to remain effective, fitlers shall be regularly cleaned.

From the date of entering service, the intervals between successive clearings shall not be longer than:• one week• two weeks, twice• one month• then every two months or as indicated by the differential pressure.The cleaning of filter elements in situ is not recommended. A spare filter element should be fitted andthe element withdrawn cleaned in the workshop and maintained oxygen clean.

Any considerable modification of the operating pattern of the system may be considered as a newcommencement of operation (e.g. large increase in maximum flowrate, reversal of flow direction).

6.4 Maintenance and Inspection

6.4.1 Compliance with RecommendationsMaintenance of the installations shall be in accordance with the recommendations in 6.1 to 6.3 andwith the special recommendations below.

Maintenance instructions provided by suppliers and designers of equipment and installations shall beobserved.

The recommendations in 4.2.7 and 4.2.8 shall also be taken into consideration in connection withmaintenance work.





6.4.2. Pipeline MaintenanceThe pipeline maintenance and inspection work is limited. It may be entrusted to specialisedcontractors.

Typical jobs are as follows:• Recentering the pipe inside sheaths• Renewal of pipeline insulation• Repair of supports and restoration of paintwork on above-ground sections.• Replacement of earth or repair to pipeline made necessary by ground movement.• Repair of damage caused by adjacent works.• Modifications, resulting from area development.• Work on the cathodic protection system:

• Modification or reinforcement of the protection• Repair of insulation• Insertion of new anodes• Provision of additional control points• Repair of faults detected.• Repair of cathodic protection potential taps• Maintenance of support structures at road, rail and water crossings.

• Maintenance of above-ground sections of pipeline.• Repair of damaged marker posts.

6.4.3 Component MaintenanceIn the event of breakdown or malfunctioning of a component it is recommended that repair on site beavoided. It is better to remove the component and replace it with one in good working condition.Reconditioning of the faulty component should be carried out in the workshop.If repairs have to be done on site, the part of the installation concerned shall be depressurised.

Adjustments to components in situ under oxygen pressure should be avoided. It is better to makeadjustments using dry air or nitrogen free from oil or grease.

During work dismantled elements shall be stored in a clean area and covered to prevent contaminationand to protect against the weather.

6.4.4 Special Inspections

6.4.4.1 Severely stressed areas of buried pipelinesIn order to monitor the stress conditions of pipelines, in particular in areas where there are frequentground movements, it may be useful to measure the state of stress of the pipe by means of stressgauges or other suitable means.

The readings should be taken at regular intervals and under different climatic conditions.

If the stresses exceed abnormal thresholds, corrective action shall be taken.

It should, however, be noted that this condition is very rare.

6.4.4.2 Effect of an incidentFollowing an incident, particles (such as soil, cinders etc) may have been entrained or projected intothe interior of the installations, both upstream and downstream. It is, therefore, advisable after anincident to thoroughly inspect the complete installation.





6.4.5 Locating a Leak on an Underground SystemIf it is necessary to locate a leak on an underground system, location of the leak may be a lengthyoperation because there is at present no simple device able to detect easily a slight leakage of oxygenfrom a system.• If sections of the pipeline can be isolated, a pressure drop test may be considered. If there is a

leak it shall be located by sound or by successive examination of pipeline sections.• In certain cases, it is possible to make use of helium or of a gas whose leakage is easily

detectable. In the case of buried pipelines, however, the result of the tests is not clear if theleakage is small. In addition, in the case of oxygen the choice of tracing gas is not withoutrestriction (see 2.2.7)

• The search for a leak by analysis of the oxygen content in the air along the pipeline may not beeffective.

• If the leak is a large one it may be audible or visible during regular inspection of the pipeline.• Finally, before any search for a leak it will be useful to make a general inspection of the whole

route to detect any areas of working or of ground movements. The leak will usually be in theseareas.

6.4.6 Drying a PipelineOn several occasions mention has been made of the need for protecting the pipelines against the entryof water. In 4.1.9.1 also mentioned is the disadvantages of hydraulic testing, which it is advisable toavoid.

It may, however, happen that as a result of an incident during working (such as sudden flooding)water may enter the pipeline. it will then be necessary to clean and dry it.

The recommended procedure is as follows:

a) drive out the water by means of a suitably leaktight pigging device (2.2.4.4.) Several passes areusually necessary.

b) Dry with clean, dry, oil-free air or nitrogen. This operation is a lengthy one. It may bespeeded up by slightly preheating the gas (50°C.)

c) After drying, brushing pigs should be passed (one or two passes) through the pipeline (2.3.5.5).

d) Finish by blowing (2.3.5.6)

Drying by adsorption of the water with chemical products is not recommended.

Vacuum drying may be used.

If there is any doubt about the cleanliness of the pipe it will be necessary to undertake a completecleaning operation according to the procedure specified in 2.3.7.

6.4.7 Programme of Preventive Maintenance and InspectionsA programme of preventive maintenance shall be drafted.

The type of programme will depend upon the installation and its particular characteristics. See 5.5.• equipment to be inspected.• inspection and maintenance tasks• frequency of inspection and maintenance

6.5 ModificationsAll modifications carried out on the system shall comply with the recommendations of 6.1 and 6.2.

Selection of new equipment and the modified installations shall comply with the recommendations ofparts 3, 4 and 5.





6.6 Withdrawal From, or Change of, Service

6.6.1 Compliance with RecommendationsThe withdrawal from or change of service of installations may involve work on them, which shall becarried out in accordance with the recommendations of 6.1 and 6.2 and the special instructions below.

6.6.2 Possible Cases• The taking of an installation out of service with the intention of returning it to service later.• Removal of pipeline• Changing from oxygen to another gas.• Re-use for oxygen of a pipeline previously used for another gas or liquid.

6.6.2.1 Taking out of serviceThe following shall be observed for any part of an installation that is taken out of service:• The installation taken out of service shall be physically separated from the part remaining in

service. Isolation by means of a valve or blind flange is not sufficient. The free end of the pipewithdrawn from service shall be fitted with an end cap.

• After purging, the installation shall be filled with dry, oil-free nitrogen or air, under slight positivepressure.

• During the period when it is out of service the installation shall continue to be inspected (5.5 and6.4). In particular there shall be no relaxation of maintenance of cathodic protection.

• Before returning to service, the installation shall be subject to detailed inspection. (see 6.2).

6.6.2.2 Removal of pipelineBefore removal:• The part retained shall be physically separated from the part to be demolished.• The section to be removed shall be emptied and purged with air or nitrogen.Correct purging of ‘dead end’ sections shall be assured.

6.6.2.3 Changing from oxygen to another gasThe installation shall be properly emptied and purged with air or nitrogen.

The part of the installation to be re-used for another product shall be physically separated from thepart remaining under oxygen.

Isolation by means of a valve or blind flange is not sufficient.

6.6.2.4 Change to oxygen service from another productGreat care shall be taken when re-using a pipeline for service with oxygen.

In order to determine the necessary action, a detailed survey of the installation shall be made.• Collect all relevant documents• Establish the history of the installation• Determine

• general condition of the installation• corrosion and wear• internal condition of the pipe• internal cleanliness of the pipe

• Examine the oxygen compatibility of the installationIn many cases intensive cleaning will be necessary (see 2.3.0.3 and Table X).

Nitrogen pipelines shall also be subjected to the above as it is possible for the nitrogen to have beencompressed at some time by means of lubricated compressors, or with carbon piston rings.

In the majority of cases, the components of the system will have to be replaced, or at the very leastcleaned and adapted for oxygen use.

The re-used part of the installation shall be physically separated from any part remaining. Isolation bymeans of a valve or blind flange is not sufficient.For commissioning see 6.2.



Part 7 : General Protection – Preventive Means


The Transportation and Distribution of Oxygen by PipelinePart 7 : General Protection – Preventive Means

IGC 13/82/E











SECTION 7: GENERAL PROTECTION – PREVENTIVE MEANS..............................................................3

7.1 LIGHTNING AND ELECTRICAL HAZARDS ...................................................................................................37.1.1 Protection Against Electrical Hazards ..............................................................................................37.1.2 Protection Against Lightning.............................................................................................................3

7.2 FIRE HAZARDS ..........................................................................................................................................37.2.1 The Danger of Outbreak of Fire. .......................................................................................................37.2.2 Fire Fighting Equipment ...................................................................................................................3

7.2.2.1 Means of protection incorporated in the installation ....................................................................................37.2.2.2 Fire extinguishers .........................................................................................................................................37.2.2.3 Water showers ..............................................................................................................................................47.2.2.4 Charging water extinguishers and showers...................................................................................................47.2.2.5 Fire hydrants.................................................................................................................................................4

7.2.3 Specific Recommendations ................................................................................................................47.2.4 Initial Action ......................................................................................................................................4

7.3 DANGERS OF OXYGEN ENRICHMENT ON PUBLIC PROPERTY .....................................................................47.4 THE DANGERS OF HYPOXIA ......................................................................................................................5

7.4.1 Breathing Equipment .........................................................................................................................57.4.2 Additional Emergency Equipment .....................................................................................................57.4.3 Specific Recommendations ................................................................................................................57.4.4 Initial Action ......................................................................................................................................57.4.5 First Aid for Hypoxia Victims............................................................................................................5

7.5 CRYOGENIC BURNS...................................................................................................................................67.6 MAINTENANCE - LOCATION AND USE OF EMERGENCY AND FIRE-FIGHTING EQUIPMENT.........................67.7 INCIDENT REPORT .....................................................................................................................................6





SECTION 7: GENERAL PROTECTION – PREVENTIVE MEANS

7.1 Lightning and Electrical Hazards

7.1.1 Protection Against Electrical HazardsElectrical energy may be used on the stations for actuation of control equipment and lightning.

Electrical installations shall comply with regulations regarding construction safety and protection ofthe workers.

See 4.2.5.13 and 4.2.5.14.

7.1.2 Protection Against LightningFor protection against lightning see 4.2.5.13.

An exception may be made for valve stations situated at high altitudes in areas particularly subject tothunderstorms, for which it may, after consultation with experts, be decided to install a lightning-arrester system:

7.2 Fire Hazards

7.2.1 The Danger of Outbreak of Fire.Two specific causes of fire in an oxygen installation are:• The internal ignition of oxygen circuits, described as ‘spontaneous’ (1.3.1.7). Since its rapid

development is practically impossible to stop, it is, therefore, advisable to vacate the areaimmediately. The fire may be confined once approach to take action is possible.

• Fires in an oxygen-enriched atmosphere should be dealt with in a traditional manner in view ofthe fact that the oxygen enrichment that favoured the start of the outbreak may vanish as theoxygen supply becomes exhausted.

7.2.2 Fire Fighting Equipment

7.2.2.1 Means of protection incorporated in the installationSafety devices actuated by lack of pressure and emergency stops strategically placed may be used toshut off the oxygen supply, vent to atmosphere and isolate power supply.

7.2.2.2 Fire extinguishersSelection of fire extinguishing agents depends upon the material to be extinguished and in some casesupon the electrical environment.

Fire-extinguishing agents suitable for an oxygen-enriched atmosphere are: water, powders with asodium, calcium or potassium bicarbonate base, carbon dioxide and certain halogenated hydrocarbonssuch as bromochlordifluoromethane.

Toxic products such as methyl bromide and chlorinated hydrocarbons shall not be used.

For putting out clothing fires water extinguishers shall be used.

Approved powder and CO2 extinguishers are suitable for fighting fires in electrical installations likelyto remain live or in areas where the use of water as a fire-fighting agent is to be avoided.

In the stations extinguishers shall be provided in adequate numbers and placed in carefully chosen,accessible places. In the absence of local regulations the number of portable extinguishers may bespecified as follows:

1 extinguisher for a station floor area of up to 25 m2

2 extinguishers for 25 to 100 m2

3 extinguishers from 100 to 250 m2

4 extinguishers for over 250 m2

The numbers recommended apply to extinguishers of 8 to 10 litres capacity of water or equivalentquantities of fire-extinguishing agents.





During certain operations, in particular during work in trenches where there is a fire risk (see 6.1.2.7)one or two water extinguishers on wheels, with a capacity of the order of 50 litres, shall be providedfor fighting clothing fires.

7.2.2.3 Water showersWhere emergency water showers are used, supply from a permanent source is preferred or if this isnot possible an independent system with a reserve of 150 to 200 litres of water and an adequatenumber of non-clogging spray nozzles. The nozzles shall be efficient and the total meaninstantaneous delivery of water should be in the order of 150 to 200 1/min.

7.2.2.4 Charging water extinguishers and showersWater extinguishers and showers operate by pressurisation with CO2 or Nitrogen.

In the case of mobile extinguishers and safety showers specially designed for accidents to personnel,measures shall be taken to prevent freezing of the water.

7.2.2.5 Fire hydrantsIn the case of large stations, a fire hydrant of the non-freezing type should be provided.

7.2.3 Specific RecommendationsThe following recommendations shall be observed in order to prevent more serious consequences.• It is dangerous to attempt to save a person who has caught fire in an oxygen enriched atmosphere

by entering the area, because the rescuer will very probably also catch fire.• No person who has been exposed to an oxygen-enriched atmosphere shall approach a source of

ignition (cigarette, torch, sparks, etc).• Personnel who have been exposed to an oxygen-enriched atmosphere shall ventilate clothing for

at least 5 minutes, moving arms and legs to disperse the oxygen after loosening clothes.• No attempt shall ever be made to extinguish a fire in an oxygen-enriched atmosphere by stifling it

with the foot. This gesture could spread the fire and transfer it to be person concerned.

7.2.4 Initial ActionIn case of fire, the following actions should be taken. The order will depend upon individualcircumstances.• Evaluate risk involved.• Warn colleagues to leave the hazard area• Operate emergency devices (emergency stop, isolation by valves, switching off current, etc)• Inform the responsible persons and the emergency team where applicable.• If necessary, inform the fire brigade and the police.• Rope off the hazard area• If clothing has caught fire, it is essential to extinguish the fire as quickly as possible - water is the

most effective extinguishing agent.• In the case of injury or burns to persons:

• Immediately call for medical assistance• Strictly observe first aid instructions or those given by medical authorities.

7.3 Dangers of Oxygen Enrichment on Public PropertyTo avoid the danger of fire in an oxygen-enriched atmosphere, leakage of oxygen or flow frompipeline fractures shall be stopped or reduced as quickly as possible. Collaboration with theauthorities concerned shall start immediately.

The following actions shall be taken. The order will depend on individual circumstances.• Leave the hazard area• Operate emergency device (emergency stop, isolation by valves, switching off current, etc).• Warn others and inform responsible persons and the emergency team where applicable.• Inform the police and fire brigade• Rope off the hazard area• Prevent access by traffic into the hazard area (road, rail, rivers, etc).





7.4 The Dangers of HypoxiaThe dangers arising from hypoxia (lack of oxygen) have been dealt with in 1.3.4.

7.4.1 Breathing EquipmentWhen it is doubtful whether there is sufficient oxygen content in the atmosphere, breathing apparatusshall be used.

The use of analytical instruments to monitor the atmosphere is recommended (see 6.1.2.2)

Filter masks are useless in an atmosphere deficient in oxygen.

The recommended types of breathing apparatus are as follows:• the self contained type, using air cylinders may present difficulties in passing through restricted

places.• the fresh air mask, fed by means of a hose of adequate length and diameter. with a source of

compressed air or from an area where the composition of the atmosphere is suitable for breathing.The mask shall have a valve system which prevents the user from breathing the same airindefinitely, which would rapidly cause asphyxia. The proper functioning of the valves shall befrequently checked.

For resuscitation purposes, oxygen apparatus should be provided.

7.4.2 Additional Emergency EquipmentFor work in confined areas or in trenches where there is a danger of oxygen deficiency means shall beprovided to ensure quick and safe evacuation (e.g. safety harnesses with rope ladders, hoists ifrequired).

7.4.3 Specific RecommendationsThe following shall be observed to prevent more serious consequences.• It is very dangerous to attempt to give assistance to a person in an oxygen-deficient environment

without proper breathing apparatus. Without breathing equipment, the rescuer or the rescue teamare in danger of suffering the same fate as the victim.

• The person giving assistance shall wear a harness and be under constant observation by acolleague who is out of the hazard area.

• Where possible resuscitation of the victim should be carried out outside the hazard area.

7.4.4 Initial ActionIn the case of an oxygen-deficient atmosphere, the following action shall be taken. The order willdepend upon individual circumstances:• Recognise the problem• Quickly identify the risks involved (see 7.4.2.)• Organise the necessary evacuation and identify the hazard area• If possible, isolate by means of valves or ventilate• Take all action to avoid development of oxygen deficiency, or adopt the recommendation in

7.4.3.• In the event of injury to persons:

• Inform the responsible persons and the rescue team where applicable• Immediately call for medical assistance• Strictly observe the first aid instructions or those given by medical authorities• If necessary, take action according to 7.4.5.

7.4.5 First Aid for Hypoxia VictimsThe following shall be carried out without delay:• Remove victim from hazard area if possible - see 7.4.3. and keep victim warm.• Administer oxygen if available or apply artifical respiration by one of the usual methods.• Continue treatment until the patient regains consciousness or until a doctor decides to stop• It is imperative to summon a doctor.





7.5 Cryogenic BurnsCryogenic burns may occur if contact is made between skin and liquid nitrogen, oxygen or cold parts,whose temperature is around minus 190ºC.

The treatment for cryogenic burns after return of the skin to normal temperature is the same as fornormal burns.

Safety gloves and glasses shall be worn when dealing with cryogenic liquids.

The injured person shall be placed in the care of a doctor as soon as possible.

7.6 Maintenance - Location and Use of Emergency and Fire-FightingEquipmentFire-fighting and emergency equipment shall be maintained in perfect condition and located and keptin easily accessible positions.

Personnel shall know its location and be trained in its use.

7.7 Incident ReportIn the event of incident, a detailed analysis shall be made.

Analysis of any incidents that occur provide useful information for the prevention of incidents, theselection of components and the solving of installation problems.