Norgren - Guide to Clean Compressed Air

Clean Compressed AirThe Norgren guide to effectiveair preparation

The air leaving acompressor is hot, dirty, wetand generally at a higherpressure than thedownstream equipmentrequires. A typical50 dm3/sec (100 scfm)compressor will push 4 500litres of water and 8 litres ofdegraded compressor oilinto the system in a yearalong with considerableamounts of dirt particles.Before this air can be used itneeds to be treated toremove the contaminants,have its pressure reduced tothe right level, and in manycases have oil added tolubricate downstreamequipment.

Figure 1.Compressed air installation, showing examplesof air preparation applications. See details onpages 4 and 5.

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APPLICATIONS4 ~ 5

REMOVING CONTAMINANTS6 ~ 10

PRESSURE CONTROL11 ~ 13

LUBRICATION 14 ~ 15

PROTECTING SYSTEMS, PERSONNEL AND THE ENVIRONMENT

16 ~ 17

SAFE SYSTEMS18

NORGREN AIR PREPARATION PRODUCT OVERVIEW

19 ~ 21

GLOSSARY22

REFERENCE TABLES23

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Compressed air is oftenwrongly assumed to be acheap or even ‘free’ sourceof power. In fact it can be10 times as expensive aselectricity by the time allgeneration, transmission,treatment and system costsare taken into account.Good air preparation musttherefore consider theenergy consumption of thesystem and air treatmentequipment.

The process of airpreparation has been at thecore of Norgren’s businessfor over 70 years. The aimof this booklet is to offerguidance on the correct,economic and safetreatment of compressed airin industrial applications.Here we can only provide abrief summary of theextensive experienceNorgren has as a worldleader in FRL technology.

For more detailedadvice contact your localNorgren Technical SalesCentre, Tel: 0345 662266.

APPLICATIONS

The following section shows several typicalsystems of a generic type and the equipmentnormally used for the application. Rememberevery system should be treated on its meritsand broken down into several elements toensure optimum installation, running andmaintenance costs are achieved.

The applications below are typicallybranches taken off a large works distributionmains and isolating valves are usually placedin front of all branches to permit isolationfrom the mains to allow for maintenance totake place without recourse to complete plantshut-down.

For expert advice on the rightequipment for your application contact yourlocal Norgren Technical Sales Centre,Tel: 0345 662266.

General Pneumatic Circuits:eg: directional control valves and cylinders, inmulti-valve circuits, machine cleaning, airmotors and high speed tools.

A Micro-Fog lubricator is required forthe several varying flow paths to ensure fulllubrication. (Figure 2)

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Figure 2.

Shut-off valve, filter/reg, Micro-Fog lubricator,soft start/dump, relief valve.

Multiple Simple Applications:eg: OEM machines.

It is often a case that with fairly simplemachines, lubricated air is require for valvingand pneumatic circuitry and oil-free air for airbearings. To keep costs low two separate linesare unnecessary and a typical arrangement fromone air supply only can be arranged as shown.

Other elements such as pressureswitches and check valves may be madeavailable within modular systems. (Figure 3).

Figure 3.

Shut-off valve, filter/regulator, oil removalfilter, porting block, Micro-Fog lubricator.

Critical Pressure Control (Instrumentation):eg: precision regulation, fluidic systems, airgauging, process control.

A typical arrangement is shown, whereoil aerosols which can prevent fast response ofdownstream devices, need to be removed.Dependant upon air quality drying may not berequired. (Figure 7)

Continuous Processes:eg: paper mills, chemical plants.

Another facet of Norgren’s Olympian Plus is theability to make duplex systems. This is invalu-able for systems which cannot be shut-down,such as continuous process plant. Two identicalair sets are joined together and one may beisolated (and serviced) whilst the other set is inoperation. (Figure 9).

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Figure 5.

Shut-off valve, general purpose filter, oilremoval filter, drier, oil removal filter, regulator,relief valve.

Figure 6.

Shut-off valve, filter/reg, Oil-Fog lubricator, soft start/dump valve, relief valve.

Figure 8.

Shut-off valve, filter/reg + direct injectionlubricator.

Figure 7.

Shut-off valve, general purpose filter, oilremoval filter, drier, oil removal filter, precisionregulator.

Figure 9.

Duplex system: shut-off valve, filter/reg,lubricator, porting block, oil removal filter andshut-off valve x 2 with manifold block connectors.

Breathing Air:eg: face masks and hoods, air agitation.

The typical application assumes thatair intakes are of a reasonable quality with noC0 or C02 contamination. It may in someinstances be a consideration to remove watervapour. (Figure 4)

Heavy Duty Lubrication:eg: large slow moving cylinders.

In such applications large amounts oflubricant are required for effective lubrication.Again a soft start/dump valve is shown but isdependent upon the application. (Figure 6).

Direct Injection Lubrication:eg: conveyor chains.

The application does not allow for‘fog’ type lubrication because of thesurrounding environment and absence of alubrication chamber. (Figure 8).

Oil-Free Applications:eg: paint spraying, foodstuffs, film processing,powders.

These applications need to be freefrom any water deposits in the downstreamsystem. For many installations this will requireair drying. The drying medium (for desiccant ordeliquescent dryers) will need protecting fromoil to allow it to work efficiently and thedownstream system will also need protectionfrom accidental migration of the material into it.A typical arrangement would be as figure 5 andin some instances it might be worth consid-ering an oil vapour removal filter too.

Figure 4.

Shut-off valve, general purpose filter, Ultrairefilter, regulator.

REMOVING CONTAMINANTS

The air produced by a compressor is hot, wetand dirty. The first step in good air prepara-tion is to filter out these contaminants. Thissection considers the removal of liquid water,water vapour, solid particles and finally oil.

LIQUID WATER

In compressed air systems water vapourexists as a contaminant originating at thecompressor outlet in vapour form, but as theair cools, it will exist as both liquid andvapour.

The amount of water vapour that canexist in any given volume of compressed airis directly proportional to the air temperatureand inversely proportional to the pressure.

Most liquid water will be presentwhen the temperature is lowest and thepressure is highest and removal at this pointwill achieve the highest efficiency.

In order to achieve this an essentialelement of any system following thecompressor is an efficient after cooler ofsufficient capacity to reduce the temperatureof the outgoing air to within 8°C of thetemperature of the water entering the aftercooler.

The outgoing air should then bepiped to a receiver of adequate capacitylocated in the coolest location available,definitely not within the compressor houseitself. This will permit further cooling of theair to occur and therefore more condensa-tion.

Generally the capacity of the receiveris about 30 times greater than the rated freeair delivery of the compressor when oper-ating in the 7 bar g region, typical of mostindustrial air supplies. See figure 10 for atypical compressor installation.

Further cooling may occur in thedistribution mains themselves. These shouldbe laid out with a pitch in the direction of airflow so that gravity and air flow will carrywater to drain legs located at appropriatesites. Down loops in distribution mainsshould be avoided, if not locate a drain leg atthe down loop. With the exception of drainlegs all air take-off points from the distribu-tion mains should be taken from the top ofthe main to prevent water from entering the

take-off lines. See figure 1 for a typical gooddistribution main arrangement.

As stated earlier most efficient waterremoval will take place at high pressure, soanything which will produce a pressure dropwithin the distribution system should beavoided. This will also be a loss of energy tothe system and increase the the cost ofcompressed air generation. Areas to avoidhere are complex flow paths with unduebends and inadequately sized piping. Seepage 23 Reference Data for friction losses inpipe and for recommended pipe flows.

The action of water removal can beachieved by drip leg drains, automatic drainvalves and as discussed later, filters. Thesedevices should be located in positions whereliquid water is present in amounts largeenough to be removed. (See figure 11).Because of the possibility of cooling occur-ring during the passage of the air throughdistribution mains and branch lines it ispreferable to install smaller individual filtersas near to the actual point of air usage aspossible, rather than rely on one large filteradjacent to the air receiver. A point toremember is that since most water will bepresent at higher pressures, always locatefilters upstream of any pressure reducingvalves.

Filters which have the ability toremove water are designed for efficient waterremoval and low pressure drop in accor-dance with the recommended pipe flows (seepage 23) and Norgren filters will have highefficiencies up to 200% of this recommendedfigure.

WATER VAPOUR

A properly designed air line filter of thecorrect size, in the correct location willeffectively and efficiently remove liquid water,but will not reduce the water vapour contentof the air. Further air cooling may result inmore water condensing out. If completefreedom from water contamination is essen-tial then the water vapour content of the airmust be lowered such that the ‘Dew Point’ ofthe air is lower than any temperature that theair can be exposed to in the system.

Once all liquid water is removedfrom compressed air, then normally the airwill be completely saturated with watervapour. The particular temperature andpressure at which the compressed air existsat that moment is known as the ‘PressureDew Point’.

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Figure 10.TYPICAL COMPRESSOR INSTALLATION

Figure 11.DRIP LEG DRAIN

Dew Points are normally measuredat atmospheric pressure and can be relatedto Pressure Dew Points through appropriatecharts.

In order to remove water vapourfrom a compressed air system Air Dryersmust be employed. The efficiency of thesedevices is much increased by ensuring thatthey are not contaminated by liquid water oroil (or combinations - emulsions) and aresupplied with air at the lowest possibletemperature. So they are additions to thesystem and not alternatives to filters and aftercoolers.There are 3 principle types of Air Dryer;

Refrigerant, Regenerative Adsorbent Desiccantand Deliquescent Absorbent Dryers(The general comparative abilities

and comparative costs are tabled in theReference Data on page 23)

In order to keep the costs of airdrying to a minimum consider thefollowing:-

a) Does the particular process requireair drying or will efficient aftercoolers, receivers and filters suffice?

b) Do not specify extremely low DewPoints if the process does notwarrant them.

c) Limit the volume of air being driedto that actually needed for theparticular process with an adequatemargin for future expansion. Thismay indicate only one area of aprocess plant need employ a dryer.

d) The major requirement for air dryersin general industrial applications iswhere high ambient temperaturesexist.

SOLID PARTICLES

Like water, solid particles exist in anycompressed air system regardless of the typeof compressor. These can arise from fourprinciple sources:-

a) Atmospheric dirt inhaled at thecompressor inlet port.

b) Corrosion products due to the actionof water and weak acids, formed bythe interaction of water and gasessuch as sulphur dioxide inhaled bythe compressor.

c) Carbon products formed by theaction of the heat of compression onthe lubricating oil or the normalwear of the carbon piston rings usedin some types of oil free compres-sors.

d) Particles originating from themechanical fixing of the metal pipework and components into the airdistribution system.The size of dirt particles covers a

very wide range from several hundred tobelow one micron (see figure 12) and thelevel of filtration depends upon the degree ofcleanliness needed for the particular processinvolved. Generally it is inadvisable toprovide finer filtration than is absolutelynecessary because the finer the filtration, thegreater the quantity of dirt trapped by thefilter element and the more rapidly it willbecome blocked.

Particles can be broken broadly intotwo groups, coarse (40 microns and above) orfine. Most normal air line filters will satisfac-torily remove particles down to 40 microns.

Fine filtration in the region 10 –25 µm is normally required for high speedpneumatic tools or process control instru-mentation. Filtration of 10 µm and below isessential for air bearings and miniaturepneumatic motors. Norgren general purposefilters are available with different grades ofelement to offer these various filtration levels.Some applications may need filtration betterthan this and indeed for paint spraying,breathing air and food related applicationsparticle removal below 1 µm is also essen-tial. Standard air line filters cannot be used

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Figure 13. GENERAL PURPOSE FILTER

Figure 12. PARTICLE SIZES

Particle Diameter, Microns0,01 0,1 1,0 10,0 100

Aerosols ll l l l l l l l l l l lSprayTobacco SmokeHuman HairVirusesBacteriaSiltFine SandCarbon BlackCoal DustPollens

and high efficiency filters (oilremoval/coalescing filters) must beemployed. Standard air line filters shouldstill be employed as pre-filters to these highefficiency filters. High efficiency filters willremove these extremely fine particles and ifexposed also to the coarser particles theywill simply clog and become congested withdirt extremely quickly.

All elements will become blocked inuse. The level to which the blocking isacceptable is dependent upon the applicationand the energy consciousness of the plantoperation. Standard filters can be cleanedand reused but in today’s environment withlabour costs high and spare parts inexpen-sive it is normally better to replace elements.This will also ensure minimum pressure dropon reinstallation as cleaning at very best willonly remove 70% of accumulated particles.High efficiency filter elements cannot becleaned and must be replaced before theybecome blocked with dirt.

Under normal usage conditionsgeneral purpose filter elements are usuallychanged before their pressure drop is greaterthan 0,5 bar, or in routine annual mainte-nance. The period can always be adjusted bymonitoring for critical applications using aservice indicator (figure 15).

High efficiency filters should havetheir elements replaced when a pressuredrop of 0,7 bar is achieved. Again a low costservice indicator is often employed. Thisdevice has a scale of two colours, usuallygreen/red. The elements should be changedwhen or before all red is achieved. Electricalservice indicators are also available fromNorgren, to provide remote signalling.Maintenance schedules can be produced toensure this ‘last chance’ situation is notachieved, indeed some applications cannottolerate even this much pressure drop,especially if this is at the generation point ofa large compressed air distribution main asthe cost of extra energy alone would be verylarge.

OIL

The principle source of oil contaminationwithin a compressed air system is from thecompressor. An oil lubricated compressor of50 dm3/s capacity may introduce as much as0,16 litres of oil per week into the system.

Oil is used for lubrication of thecompressor but when it emerges with thecompressed air prior to distribution the oil isnow in a totally unusable state. Having beensubjected to high temperatures during aircompression it becomes oxidized and acidicand can be considered as an aggressivecontaminant rather than a lubricant and somust be removed.

Normal air line filters will removesufficient liquid oil (along with water) toleave the air in a suitable condition to supplymost pneumatic tools and cylinders, butcertain processes demand completely oil-freeair.

One solution is to use oil-freecompressors. These will still produce aircontaminated with dirt and water and it isoften more economical to use lubricatedcompressors in conjunction with aftercoolers and standard air line filters, onlyfitting high efficiency oil removal filters at thepoints in the system which demand oil-freeair. This ensures that the amount of airneeding special treatment is kept to aminimum by allowing a smaller specialisedfilter in the affected area and not a largespecialised filter for the whole plant.

Oil in a compressed air system canexist in three forms, oil/water emulsions,aerosols (small particles suspended in theair) and oil vapours.

Emulsions can be removed bystandard air line filters but the aerosols areour next concern.

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Figure 14.‘PURAIRE’ COALESCING FILTER

Figure 15.FILTER SERVICE INDICATOR

OIL AEROSOLS

These particulate oil droplets exist in theairstream and the most troublesome are inthe size range 0,01 to 1 micron (approx90%), the rest may be slightly larger (seefigure 12 particle size chart).

Most standard air line filters achievewater removal by centrifugal action but dueto their small particle size these aerosols areunaffected and require special coalescingfilters.

In addition to removing the oildroplets these filters will also remove minutewater droplets, but they must be protectedagainst gross dirt or water contamination bymeans of standard air line filters mountedimmediately upstream (figure 16). It isnormally advisable that these filters arecapable of removing particles down to 5microns or less otherwise the coalescingfilter may quickly become choked andblocked with dirt, requiring a filter elementreplacement.

Coalescing filters are normally ratedby the amount of air which they can ‘process’to achieve a given oil removal performance,normally a maximum remaining oil contentin the exit air of 0,01 mg/m3 (or 0,01 ppm).To try to overflow these units will not onlyresult in a greater pressure drop across theunit and therefore extra energy cost but moreimportantly the remaining oil content willincrease. This may be acceptable for someapplications where oil removal down to theorder of 0,5 mg/m3 is quite adequate to givea degree of protection to a system particu-larly prone to gross oil contamination.

Figure 19 shows Norgren coalescingfilters flow capacities to achieve their givenperformance.

OIL VAPOUR

For most processes the removal of oil vapouris unnecessary since unlike water vapour, oilvapour exists only in minute quantities andis not objectionable except in circumstanceswhere its odour is unacceptable eg. in foodprocessing, pharmaceutical and beverageindustries and breathing air applications.

The most common method ofremoval is to pass the air through anadsorbing bed, usually of activated carbon,although other materials can be used.

Such vapour removal filters willnormally reduce the total remaining oilcontent when used in conjunction with a pre-filter (general purpose filter) and a coalescingfilter to 0,003mg/m3.

A common misconception of thesefilters is that they will remove carbonmonoxide or carbon dioxide - they will not.

As with oil removal (coalescing)filters the vapour removal filters should onlybe employed where their function is needed,the maximum flow rating is not exceeded andthey are preceded by a general purpose and acoalescing filter. This will minimise the sizeof the filters required and therefore the costof the installation.

Norgren offers an integratedcoalescing and vapour removal filter in theOlympian Plus range. (See figure 17). Thisincludes a colour change service indicator asstandard.

The location of the compressorintake may also have an effect on the level offiltration required, if for example the intake issituated by a source of hydrocarbon vapoursetc. Clean air intake will reduce the cost ofproducing clean compressed air.

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Figure 16.OIL REMOVAL FILTER WITH GENERALPURPOSE PRE-FILTER

Figure 17.‘ULTRAIRE’ OIL VAPOUR REMOVAL FILTER

FILTER SELECTION

Once all of the contaminants have beenconsidered the degree of cleanliness of airfor each part of an industrial plant or processcan be determined. By only employing thecorrect filters in the right location energy andmaintenance costs can be kept to aminimum. The volume of air involved in eachstage must always be considered as under-sized, inappropriate filters are a prime causeof high energy costs.

A very general guide to the typicallevels of cleanliness required for commonprocesses is given in figure 21. Each appli-cation should however be considered on itsown merits.

Recommendations on air drying areparticularly difficult since this is dependantupon the temperature of the compressed airmain adjacent to the application/machine thelevel of pressure reduction and air flow rate.

For well laid out generation anddistribution systems drying is seldomrequired in countries of typically low tomoderate relative humidities and ambienttemperatures.

When choosing a filter to cleancompressed air ensure:-

● The correct type of filter and elementrating is selected for particleremoval.

● The liquid removal efficiency is highand that re-entrainment is notpossible.

● Ease of maintenance and liquidcondensate collection is possible.

● Easy visibility of condensate and/orelement ensures that function isachieved or shows if maintenance isrequired. This may be a pressure drop device,

liquid level indicator or transparent bowl. In order to aid determining the type

of water and particle removal, figure 20shows ISO 8573 Air Quality Classification.

Figure 18.GENERAL PURPOSE FILTER FLOWS

Pipe Unit Flow (dm3/s)*Size

1/8" F07 15

1/4" F72G 30

1/2" F64G 70

F74G 83

1" F15 175

*Flow at 6,3 bar and 0,5 bar pressure drop.

Figure 19. HIGH EFFICIENCY FILTERFLOWS

Pipe Unit Flow (dm3/s)* OilSize Removal

Class**

1/8" F39 2,8 2

1/4" F72C 4,5 2

3/8" F64C 16 2

F64B 7 1

F74C 16 2

1/2" F64H 28 2

F64L 11 1

F74H 28 2

1" F53 60 2

F52 60 1

1 1/2" F47 85 2

F47 120 3

2" F47 200 2

F47 286 3l l l l

0 10 100 1 000

*Flow with 6,3 bar inlet to achieve ‘class’requirements.**See figure 20.

Figure 21.RECOMMENDED FILTRATION LEVELS.

Application Typical Quality Classes

Oil Dirt

Air agitation 1 3

Air bearings 2 2

Air gauging 2 2

Air motors 4 4

Brick and glass machines 5 4

Cleaning of machine parts 3 4

Construction 4 5

Conveying, granular products 2 4

Conveying, powder products 1 3

Fluidics, power circuits 2 5

Fluidics, sensors 2 3

Foundry machines 4 5

Food and beverages 1 1

Hand operated air tools 5 5

Machine tools 5 4

Mining 5 5

Micro-electronics manufacture 1 1

Packaging and textile machines 5 3

Photographic film processing 1 2

Pneumatic cylinders 3 5

Pneumatic tools 5 4

Pneumatic tools (high speed) 4 3

Process control instruments 2 3

Paint spraying 1 1

Sand Blasting 4 5

Welding macines 5 5

General Workshop air 5 4

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Figure 20.

AIR QUALITY CLASSIFICATIONS ISO 8573Quality Class Dirt Water Pressure Dew-point Oil

Particle Size in Microns °C (ppm vol.) at 7 bar g (including vapour) mg/m3

1 0,1 -70 (0,3) 0,01

2 1 –40 (16) 0,1

3 5 –20 (128) 1

4 15 +3 (940) 5

5 40 +7 (1 240) 25

6 — +10 (1 500) —

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PRESSURE CONTROL

In order to use compressed air most effec-tively and efficiently it is necessary to reducethe pressure to precisely the level requiredfor its application.

All pneumatic equipment has anoptimum operating pressure. Using it at ahigher pressure causes excessive wear, withno significant increase in output, whilstwasting the compressed air itself and thecost expended in generating it. If thecompressed air is stored at this higherpressure and only used at exactly the lowerlevel required for the application the storagevessel or receiver need only be topped upfrom some intermediate figure to the fullcapacity, which is more efficient. In order toachieve this optimum usage the compressorusually operates between two pressurelevels, that is the receiver normally has apressure switch set to give compressor cut-off at the required storage pressure (usuallythe highest achievable for filtration efficiency)and a lower level usually about 10 - 20%lower. This figure can be adjusted for theoptimum when the receiver size, system flowdemand and compressor output rating areconsidered. The outcome of this arrangementis that the compressor is not continuallyrunning, using up excess energy, producingmore heat which produces more water, whichmust be removed (extra cost) to supply asystem requirement at too high a pressurewhich causes excessive wear (extra cost) forno increase in output.

A pressure reducing valve cantherefore generate cost savings greater thanits purchase price in a short time period.Also it is mandatory in such applications asblow guns and cooling nozzles where the useof compressed air at high pressure ispotentially hazardous.

Pressure reducing valves or regula-tors have two principle characteristics whichmust be considered in establishing which toselect, their ability to keep the outlet pressureconstant irrespective of the inlet pressure(called the regulation characteristic) andirrespective of the outlet flow (flow character-istic). Standard designs are manufacturedwhich achieve certain levels of the idealperformance on each characteristic. A simpleapplication with loose demands of the two

principle requirements could employ astandard and therefore low cost reducingvalve. The correct selection and deploymentin the relevant part of the air system willachieve the lowest cost most energy efficientsystem.

The penalty for poor regulationcharacteristics is that the outlet pressure willvary but in the bulk of compressed airapplications, inlet pressures are fairlyconstant so this poses few problems.

The penalty for poor flow character-istics is pressure drop which directly reflectsin energy costs. Every regulator suffers fromsome amount of pressure drop so for goodsystem design this is the more importantproperty to examine.

An important cost saving can beachieved by employing a reducing valve inconjunction with double acting cylinderswhere a reduced pressure can often be usedadvantageously on the non-working returnstroke and cost savings as high as 30% canbe achieved. This can be very important onmulti-cylinder installations.

A point common to all pressureregulators is that in order to work constantlyand repeatability within their design limitsthey will require a supply pressure at least 1bar higher than the required outlet pressure.They will work with a lower differential butperformance can be impaired.

TYPES OF REGULATOR

Although Norgren produces a vast array ofregulators they can be broadly broken into 4types:-

General PurposePilot OperatedPrecisionSpecial PurposeMost general purpose regulators are

of the diaphragm type (figure 22). In generalthese are more sensitive than piston typeregulators which tend to have better flowcapacity for a given size. In the majority ofcompressed air systems response, ratherthan compactness for a given pipe size is themajor requirement, hence diaphragm typeregulators are most common.

Regulators can be relieving or non-relieving. The relieving feature allows for thesystem (outlet) pressure to adjust from ahigher level to a lower one without actuatingdownstream equipment (this is done byhaving a vent hole through the diaphragm toatmosphere). Generally this relief hole is verysmall in relation to the regulator main portsso no more than a bleed flow can beachieved and this should not be considered afull relief or even safety relief device.

Non-relieving versions do not havea connection from the downstream system toatmosphere and so can only be adjustedfrom a higher desired or achieved outletpressure to a lower one by cycling down-stream equipment or using a 3/2 shut-offvalve to expel excess air from the down-stream system.

Figure 22. GENERAL PURPOSE REGULATOR

Pilot operated regulators are thosewhich do not have a direct mechanicalmeans of adjusting the outlet pressure. Thiseliminates leverage problems in achievinghigh (16 bar plus) pressures in large pipesize units. The outlet pressure is controlledby means of an air pressure signal (Figure23) which is normally produced by a preci-sion regulator. This allows for example apilot operated regulator to be remotelysituated in the large distribution mainsnormally in a building’s roof, but be adjustedto give the desired output pressure fromshop floor level. For the majority of pilotoperated applications it is best to take thesystem or outlet pressure reading from thepilot operated (often called a slave or main)regulator itself or the distribution system asthe pilot regulator’s outlet pressure isgenerally not the same.

Pilot operated regulators also givebetter performance by eliminating the controlspring and usually have a large diaphragmarea compared to valve area which alsoimproves the accuracy of pressure control inresponse to small pressure changes.

Another level of control accuracycan be achieved by employing a feedbackpilot regulator. This device senses the outletpressure in the system and a piped connec-tion feeds this signal back to the pilot

regulator which compares it to the desiredoutlet signal and ‘compensates’ by increasingthe outlet pressure if the feedback signal istoo low, or decreases if the signal is toohigh. This type of control is usuallyemployed where a large steady air flow to acontinuous process is required.

Precision regulators (or controllers)are normally used for instrumentationapplications where exact repeatability andfreedom from outlet pressure setting driftover short or long term operation is neces-sary. These regulators normally have a smalloutlet flow range, but exhibit superior flowand regulation characteristics. Their ability toachieve the ideal of these characteristics overflow and pressure ranges is reflected in theirsize and price.

Generally most precision regulatorsemploy a special arrangement to allow aconstant bleed of air to escape to atmos-phere. Although this is a cost to system as awhole, being a loss of air, it is the pricewhich must be paid in order to achieve thevery fast response to the applicationsdemands needed to keep the systempressure as constant as possible. The besttypes of precision regulators also employ anintegral pilot operation, producing effectivelytwo diaphragms and valves, one small andsensitive the other a slave to ensure that the

overall performance meets the requirementsof the particular application.

Another feature of precision regula-tors is their relief capacity and some have theability to relieve up to 80/90% of theirrecommended regulated flow for specialistapplication such as tensioning belts, paperrolling and balancing. (Figure 24).

Special purpose regulators cancover a whole range of specific demandsincluding meeting exact environmentalrequirements with special materials, havinghigh relief flows, plunger operation in placeof handwheels etc. They can be derivatives ofany of the other types of regulators withapplication specific additions.

REGULATOR SELECTION

Ensure the regulator chosen exactly fits theperformance requirements of the application.A regulator which controls the pressure to adistribution main is usually of the generalpurpose type or for large volume/flowapplications pilot operated.

Decide if the performance require-ments need a standard or precision regulator.Then decide if the flow capacity of theregulator is suitable for the pipe size needs(see figure 38) and check with the regulatorsflow characteristics. Figure 25 shows flowratings of Norgren General PurposeRegulators . If there is no variation in theinlet pressure to an application then theregulation characteristic of the regulator isunimportant but the flow characteristic willbe. If the inlet pressure is exposed tovariations then the regulation characteristics

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Figure 24.NORGREN MICRO-TROL PRECISIONREGULATOR

Figure 23.A TYPICAL PILOT OPERATED REGULATOR INSTALLATION.

SUPPLYAIR

SUPPLYAIR

OUTLETAIR

CONVENTIONALPILOTREGULATOR

PILOT OUTPUTLINE

PILOT OPERATEDREGULATOR

of the chosen regulator must also be consid-ered.

A variety of spring ranges are offeredwith most regulators. Ideally the regulatorsshould be operated inside the middle third oftheir range, since at the lower end of theirrange the spring loses some sensitivity andat the higher end may suffer in linearity. Alsolow rate springs can help reduce pressuredroop, so springs can be selected to best fitthe systems requirements.

If a precision regulator is requireddecide on the level of sensitivity, flow andregulation characteristics and if requiredrelief capacity and temperature sensitivity.Select only a regulator suitable for itsapplication. Correct selection could see ageneral purpose regulator with ordinaryperformance characteristics fulfilling whatmay be considered a precision regulatorsfunction without system degradation at alower installed cost and more cost efficiently.

Figure 25.GENERAL PURPOSE REGULATOR FLOWS

Pipe Unit Flow (dm3/s)*Size1/8" R07 6,51/4" R72G 331/2" R64G 120

R74G 1051" R15 180

*Flow with 10 bar inlet, 6,3 bar outlet and 1 barpressure drop.

FILTER/REGULATORS

Filter/regulators both clean the air to theapplication and control the pressure in onecompact unit. For general purpose applica-tions filter/regulators are usually lower costthan two separate units.

Some specialist filter/regulators areavailable for instrument applications with fineparticle removal or even oil removal proper-ties with precision regulator characteristics,as are others with special material compati-bility.

Figure 26.NORGREN FILTER/REGULATOR FLOWCAPABILITIES.

Pipe Unit Flow (dm3/s)*Size1/8" B07 6,21/4" B72G 381/2" B64G 1101/2" B74G 1001" B15 230

*Flow with 10 bar inlet, 6,3 bar outlet and 1 barpressure drop.

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Figure 27.GENERAL PURPOSE FILTER/REGULATOR

Figure 28.ALUMINIUM INSTRUMENTFILTER/REGULATOR

LUBRICATION

The next important step in processingcompressed air is that of introducing into theair a suitable amount of lubricant, usually oilto enable the operating equipment to performto its requirements efficiently without exces-sive resistance or wear. Excessive resistanceto motion will result in extra powerconsumption and excessive wear will resultin shortened equipment life. Both result inextra cost.

There are two basic type of lubri-cator in general use, aerosol and injectionpump.

The most widely used is the aerosol,which was the first type of dependableautomatic air line lubrication device, inventedby Norgren in 1927.

Aerosol lubricators are available intwo main types, Oil-Fog and Micro-Fog. Inan Oil-Fog lubricator the fog producedgenerally has relatively large oil particles andso will only remain airborne for relativelyshort distances. As a general rule of thumbthe maximum distance an Oil-Fog lubricatorshould be placed from the pneumatic devicewhich it is to service is 9 metres. Largeparticles are more strongly affected bygravity and so Oil-Fog lubricators should notbe used in attempting to lubricate a device ata higher level than the lubricator.

The Micro-Fog lubricator uses aspecial fog generator to atomise only afraction of the oil.

Because the airborne fog is nowmade up of only light particles, less thanabout 2 microns in size, gravity does nothave the same effect upon it and so this fogcan travel not only “up-hill” but also for longdistances and through more complex feedlines without wetting out in the pipe. Micro-Fog can also ensure proportionate distribu-tion through multiple lubrication outlets,ideal for multiple valve control circuits.

A comparison of these two types oflubricators can lead to a simple division ofthem as being high delivery (Oil-Fog) or lowdelivery types (Micro-Fog). All of thedroplets of oil shown in the Oil-Fog sightdome will be delivered into the system andfor the Micro-Fog only about 5 to 10% of thedroplets witnessed will be delivered. TheMicro-Fog can therefore be used in applica-

tions where only very small amounts oflubricant are required, possibly over largeareas. By adjustment of the drip rate higheroil delivery can be achieved to match that ofan Oil-Fog lubricator at normal usage rates.

The Micro-Fog principle has madepossible the application of aerosol lubrica-tion to general machine lubrication such asbearings, gears, chains etc.

Both Oil-Fog and Micro-Foglubricators include a non-return valve in thesyphon tube to ensure immediate lubricationas soon as the air is turned on. However forsome rapidly cycling duties or systems withsmall stroke cylinders it is sometimes notpossible to lubricate correctly with conven-tional lubricators. For such applicationssystem modifications such as quick exhaustvalves must be employed or a bi-directionallubricator suitably located can overcomesuch problems.

The second type of lubricator, theinjection oil-pump is a positive displacementdevice. Because of its nature it cannotcontinuously deliver lubricant but hasparticular applications in multi-spindle nutrunners where conventional lubricators willsplit air flows according to passagewaygeometry. The injection pump will deliver thesame amount of lubricant to the applicationpoint every time it is cycled. This type oflubricator is often used on conveyor chainswhere their application will overcomeproblems of incorrectly located or adjustedconventional lubricators.

Several such injectors can bemanifolded together to lubricate at severaldifferent points, but at the same frequency.

Whichever type of lubricator isemployed it is important to remember that alllubricators are total loss systems in that thedispensed lubricant will reach its ‘bearing’surface and be broken down into smallerparticles and ‘lost’ as the system is cycled.

The amount of oil which should bedelivered to a pneumatic system to providesufficient lubrication is difficult to determineas all systems will be different. Pneumaticdevices in a system may require differentamounts of lubricant and so equipmentmanufacturers recommendations shouldalways be followed, where they exist.

For a general guide for mostpneumatic systems an oil output density of

60 mg/m3 is a good basic starting point.From regular inspection and servicing theoptimum setting may be found by increasingor decreasing the amount delivered.

FILLING LUBRICATOR BOWLS

With all lubricators eventually the bowl orreservoir will need filling. Most Oil-Foglubricators have a check valve fitted to allowthem to be refilled whilst in use. Most Micro-Fog lubricators can be fitted with a quick fillnipple and so be topped up with lubricant,supplied at a pressure of approximately 1 barabove that within the bowl.

Remote fill devices also exist whichcan do this automatically. Such devices canbe used to supply several bowls or reservoirsfrom one central position.

Another way to reduce the scheduledtask of refilling lubricators or to ensurecritical operations never ‘run dry’ is toemploy a liquid level switch. Such devicesare normally float operated switches whichcan give an electrical signal on low or highliquid level. Such signals can then be builtinto a control system to fill or stop filling orgive warning alarms.

14

Figure 29.OIL-FOG LUBRICATOR

Although a high level signal may atfirst seem strange remember that overfillingwill not only prevent the lubricator fromperforming its function of producing anair/oil mix of fog, but will distribute bulklubricant into the pneumatic system, floodingit.

LUBRICATOR SELECTION

Determine which parts of the system requirelubrication (some distribution lines will be tooil free areas such as paint spraying orbreathing air applications).

Determine what type of lubrication isrequired for each part of the system. Slowmoving heavy cylinders need high deliveryso chose an Oil-Fog type lubricator. Longruns of pipe in multi-valve circuits require aMicro-Fog (or several Oil-Fog) lubricators tolubricate effectively. High speed tools arebetter served by a Micro-Fog, as are tips ofcutting tools.

All lubricators are a source ofpressure drop and therefore energy loss, soalthough Micro-Fogs may be positionedalmost anywhere in a system select andplace them as conveniently close to the

application as possible. Always selectlubricators and locate them where differentlevels of lubrication are required, neverattempt to fit one lubricator to supply a wholedistribution system as differing parts willthen be over lubricated, whilst others areunder lubricated.

Ensure that only special purposeMicro-Fog lubricators are used for bearinglubrication as other types are not suitable.

Check that the lubricator chosen hassufficient flow capacity without excessivepressure drop for the pipe line size beingused (see figure 37 and individual lubricatorperformance graphs).

Figure 31. LUBRICATOR FLOW RATES

Pipe Unit Flow (dm3/s)*Size1/8" L07 51/4" L72 241/2" L64/L74 721" L15 175

*Flow at 6,3 bar and 0,5 bar pressure drop.

Since lubricators require a minimumpressure drop to operate which is normallyrelated to a flow, ensure that this minimumflow condition is met or there will be no oiloutput. It is important to note that leaks fromcompressed air systems are a source ofenergy loss and also such leaks are effec-tively a constant flow through the system. If alubricator with a very low start point is usedthen even a small leakage, if in excess of thestart point will cause it to drip and supply oilto the system. This is often the cause of oilflooding during periods of shut-down,especially over weekends.

Where continual usage exists selecta lubricator with sufficient reservoir capacity.For units in 1/2" pipe size and above, severalreservoir capacities are usually available.Where this is not possible because of spaceor usage rate utilise remote fill devices orliquid level switches to auxiliary systems.

Where very high flows are encoun-tered use a fixed venturi type lubricator.Unlike standard types this does not automati-cally adjust to give a constant air/oil density,so the flow requirement needs to be essen-tially constant. This type of device will thennot produce excessive pressure drops

associated with high flows and so be moreenergy efficient.

For exceptionally high flow ratessmall amounts of lubricant (especially foranti-freeze usage) can be injected by smalllubricators into large distribution mains of 1to 2" and above, where a full bore lubricatorwould be expensive in both cost andpressure drop.

15

Figure 30.MICRO-FOG LUBRICATOR

PROTECTING SYSTEMS, PERSONNEL AND THE ENVIRONMENT

Safety in the workplace is essential and isemphasised via the Machinery Directive, thePressure Systems legislation and theProvision and Use of Work EquipmentRegulations (PUWER).

The following section can helpmachine designers and others using pneu-matics by illustrating those air line productswhich, when correctly applied, can be usedto ensure safe pneumatic systems.

In it we have cross referencedrelevant documents. Norgren stronglyrecommend that all who are involved withmachine and system design should becomefamiliar with these and other relevant safetydocuments.

OVERPRESSURE PROTECTION

The components in pneumatic systems willoften have a pressure rating lower than thatgenerated at the compressor and pressureregulators are used to reduce this pressure tosafe efficient levels. In the event of a faultthe components can be exposed to excesspressures leading to mis-function or inextremes failure of the pressure containingenvelope.

To protect against this excessiveover pressure situation several solutions canbe employed the most common being a reliefvalve. Selecting a relief valve is not a simpleprocess, and detailed consideration of thesystem or element of the system is required.

In general all pneumatic componentsand equipment will have a Safe WorkingPressure (SWP) and over pressure limit of10%. The designer of the pneumatic systemcan use regulators to run the system atpressures below the SWP and use the 10%safety factor to be the limit of over pressurethat the system can experience with the reliefvalve in operation.

A relief valve is defined as a devicewith its outlet so connected to a pressuresystem to enable the system pressure to beheld at a constant level. This constant levelwould then be at or below the stated SWP +10% over pressure allowance.

Relief valves need to be set to only

operate when the regulated pressure isexceeded and so need to be set higher thanthe regulator. There will be a tolerance onthe relief valve setting and on the regulatorsoutlet setting, depending on its flow andregulation characteristics. A commonproblem is a relief setting too close to thesystem operating pressure. The conse-quence of this is to have the relief valveoperating and venting air during normalsystem operation, which is an expensivewaste of air.

Once the relief valve setting pressureand acceptable level of over pressure arechecked the flow capacity of the relief deviceand that of the system can be considered.The relief device must be able to match orexceed the amount of flow through the part ofthe system being protected without thesystem pressure rising above the acceptableover pressure level.

Several methods can be used toachieve this:-

The relief device has a flow capacityin excess of the compressors free air deliverycapacity - in systems where no receiverexists - i.e. flow out of system is greater thanflow in.

The relief device has a capacity inexcess of the flow through the smallest flowpassageway upstream of the equipmentbeing protected. Tables of orifice flow existto determine the flow at different pressuresthrough differing sizes of orifice. Thesmallest bore is acting as a restriction to theflow into the downstream system and unlessthe upstream pressure can be increased theflow will be choked through this area andtherefore limited. This is important since amains distribution system can be of verylarge volume with pipes of large bore andcompressors of high capacity, but the devicebeing protected could be fed by 1/8" nominalbore tubing. So a small low cost device onlyis required and not one large enough to copewith the full system capacity.

In areas where no such flow restric-tion exists, one should be created in order toreduce the cost of the relief valve to beemployed, ensuring of course that therestriction does not cause excessive pressuredrop in the course of normal operation.

Legislation Reference:BS EN 983 5.1.2

TYPES OF RELIEF VALVES

Several types of relief valves exist to achievedifferent levels of performance with respect tothe flow capacity and over pressure limita-tions. The most common is the ‘pop’ type,followed by the diaphragm type. For betterperformance use pilot operated valves withthe integral pilot operated type being themost compact and cost effective (figure 32).

An “in-line” type of relief device hasrelief port at 90° to the direction of flow andin normal operation flow passes through thebody of the device, without interfering withnormal upstream operation. A common useof this type of device is with machinebuilders, where all the controlequipment/protection devices are in onediscrete position, aiding both installation andscheduled servicing.

The in-line device differs from thepop or diaphragm type of relief valves whichare connected into the system on a tee-piece.Flow through these devices only occurswhen in operation and air vents to atmos-phere.

In both cases the exhaust flow canbe piped away to an area where the noiseand flow will not cause disruption or harm tothe environment or the operators. Exhaustsilencers may be required to reduce noiselevels in high flow exhaust applicationswhere piping away to less sensitive areas isnot possible.

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EXHAUST AIR

Exhaust air needs to be treatedcorrectly to reduce the effects of noise, oilmist and to minimise danger to personnel.

Where a dump valve is employed,large volumes of air can be released at highspeed which will produce high noise levels.Simple silencers made of porous materialsare often able to deal with this. In moredemanding high velocity cycling applicationsa heavy duty silencer may be needed.

Silencers are normally rated for theirnoise reduction and associated backpressure so the choice should be dependentupon the duty required of the device toensure the most cost efficient silencer isutilised.

The next major pollutant is oil. Allpneumatic lubrication systems are total losssystems, the lubricant goes into the system,gets degraded in its function and is carriedalong with impurities and dirt to the atmos-pheric exhaust.

In well maintained and correctlylubricated systems of a general engineeringnature the amount of exhausting oil is verysmall and will disperse without generallyaffecting the working environment adversely.However incorrectly lubricated systems orthose which require high levels of lubricationfor heavy duty applications can expel highlevels of oil into the atmosphere on their

SOFT START/DUMP VALVES

The next form of protection is that associatedwith the moving parts of the system, wherethe parts themselves can need protectionagainst excessive wear due to loading onstart up or there is danger to personnel fromsudden movement of the parts.

Here the use of “soft start” (“slowstart”) valves is desirable. The normaloperation is to allow air to pass to a pneu-matic system or device in a gradual manner,where the rate of pressure build-up can becontrolled by adjustment of the valve. Thevalve design is generally an internal poppetvalve which is spring operated and when thegradual pressure build-up produces a forcein excess of that holding the poppet closed,the poppet moves to the open positionallowing flow to proceed through the normalflow passageways. The level at which thepoppet operates is called the snap point andfor most devices this snap point will be inthe range of 40 to 70% of full line pressure.

Because pressure build up in anysystem is dependant upon the systemvolume it is important to locate these devicesclose to the piece of equipment they are toprotect. Fitting of a larger valve to acomplete distribution system will generallymean the system will take many minutes tofully pressurise.

It is extremely common to couplethe slow start valve with a dump or exhaustfunction valve within one body, for compact-ness.

The function of the ‘dump’ valve is toquickly exhaust the pressure from thedownstream system. The valve can havesolenoid or air pilot operators and often amanual override or emergency dumpfunction.


17

Figure 33. SOFT START/DUMP VALVE

Figure 34.COALESCING SILENCER

Figure 32.INTERNAL PILOT RELIEF VALVE

exhaust cycle. In such instances use of acoalescing exhaust silencer should beconsidered. The action of this device isexactly as those for oil removal filters whichcause the small oil droplets to mergetogether into large droplets which fall into acontainer for removal. (See figure 34.) Inthe course of this process the porousmaterial employed also reduces the noiselevel of the exhaust air.

Since these devices are on theexhaust side of the pneumatic system theyare exposed to sudden shock loading, whichmeans their oil removal capabilities are notas good as those employed in coalescingfilters. A good exhaust coalescing silencerwill however give figures of typically 2 ppmunder average usage conditions.

PROTECTION DEVICESELECTION

(i) Decide which parts of the system cannotwithstand the maximum pressure which canbe developed in the distribution system (orcompressor).

Determine which type of relief valveis required to control this air pressure mosteffectively with consideration of failure flowthrough that part of the system. Considerusing a restrictor (orifice) without producingexcessive pressure losses in the normaloperation of that part of the system.

For very large flows consider a pilotoperated regulator as a dump valve.

For machines consider an in-linedevice to build-up one complete integralmodular preparation assembly for ease ofpiping, location and servicing.

(ii) Decide upon which parts of thesystem can suffer from problems on initialstart up, or resetting where excessive initialspeeds can lead to wear problems or entrap-ment, or where an emergency stop/dumpfunction is required.

Employ one soft start/dump valve foreach section of the system operated in thisway. The larger the system the longer thedump or emergency stop function will take tofully empty the system.

Locate soft start/dump valves in theFRL assembly at the downstream end toprevent high back flows through the lubri-cator.

(iii) Where large volumes of air areto be exhausted consider fitting a silencer ifthe air cannot be piped away to a convenientposition.

Where rapid cycling of exhaust ispresent fit a heavy duty silencer.

Where the exhaust air can be heavilyladen with lubricant, usually from equipmentrequiring high levels of lubrication fit acoalescing exhaust silencer.

OTHER PRODUCTS FOR SAFESYSTEMS

Other air line products that can help createsafe pneumatic systems -

Preset pressure regulators - whereunauthorised adjustment of the set pressurecan be injurious to personnel.

Guidance Document: HS (G) 39Lockable shut-off valves - ensure

that a ‘safe to work’ procedure can beadopted without jeopardy from the unautho-rised re-application of pressure.

Legislation: BS EN 983 5.1.6Guidance Document HS (G) 39Tamper resistant kits - can be fitted

to pressure regulators, filter/regulators, reliefvalves and lubricators to ensure that flow,pressure and other settings are securedagainst unauthorised adjustment.


18


UNRIVALLED PRODUCTRANGE

Norgren, the world leaderin air preparation offers anunrivalled range of productsto enable you to produceclean compressed air anduse it economically andsafely.

Whatever your need fromthe simplest factory installa-tion to a complex medicalapplication, Norgren hasthe right air preparationequipment for you.

19

Figure 36.OLYMPIAN PLUS SYSTEM

Figure 35. EXCELON SYSTEM


These pages show the main product families,together with just a few of the morespecialised standard products. In addition weproduce hundreds of products to customersspecifications, utilising the vast experienceNorgren has accumulated over the past 70years.

All the main ranges include :-General Purpose FiltersHigh Efficiency FiltersVapour Removal FiltersGeneral Purpose RegulatorsFilter/RegulatorsOil-Fog and Micro-Fog LubricatorsSoft Start/Dump ValvesShut-Off ValvesRelief valvesThese are supported by a wide

choice of mounting methods and accessoriesPorting BlocksPressure SwitchesLevel ControlsService IndicatorsManifold Blocks

OLYMPIAN PLUS

Olympian Plus is the new generation FRLsystem, which sets new standards for ease ofuse and flexibility. The unique plug in featureallows quick installation or removal of unitswith a simple quarter turn of the clamp ring.The easily connected yoke systems allowsspeedy assembly of combination units.

Packed with features to make fieldmaintenance easy and convenient OlympianPlus is ideal for industrial installations.Equally the wide range of system accessoriesmean it offers the OEM user a highly flexiblesolution.

Olympian Plus is available in basic1/2 inch , with optional 1/4, 3/8 and 3/4porting.

OLYMPIAN 15 SERIES

The 15 Series is the basic 1" versionof the Olympian system. Available in 3/4through 1 1/2 inch ports it offers a flexiblesolution for larger machines and highvolume industrial use.

EXCELON

Excelon is a completely new air preparationsystem from Norgren. Although direct ported,thanks to a patented Quikclamp connectionsystem, Excelon can be used where bothstand alone units or modular assemblies arerequired.

It offers exceptional performance ina compact well styled unit. It is ideal forOEM’s offering a flexible modular systemwith useful accessories such as pressureswitches and manifold blocks. The quickrelease bayonet bowl, high visibility liquidlevel indicator and easy to operate patentedQuikdrain are just a few of the featuresdesigned with ease of maintenance in mind.

There are two sizes in the Excelonrange.

EXCELON 72 is basic 1/4 (withoptional overporting to 3/8). However thereis nothing basic about its performance,which is actually better than many competi-tors 3/8 products.

EXCELON 74 is a 1/2 inch range(optional 3/8 and 3/4).

20

PORTED UNITS

The ported products have no modularconnection system, and are generally used asstand alone units. They cover a wide range ofbasic port sizes from 1/8" (07 Series)through 2" (18 Series).

07 SERIES

The miniature range offers goodperformance units for smaller flow require-ments. Here regulators are the most commonproduct and in addition to the cataloguedunits Norgren offers a vast array of options.Units are available in a range of bodymaterials, with internal components chosento deliver the specific performance character-istics requested by the customer.

11 SERIES

A basic 3/8" size the 11 Series isalso offered with 1/4" and in some cases1/2" ports. These are well proven reliableunits often used as an alternative to a true1/2" product, where the flow requirementsare not high.

18 SERIES

The 18 Series is a basic 2 inchrange designed for factory air mains or highflow OEM applications such as shot blastingor textile machines.

PRECISION REGULATORS

Norgren has several different precisionregulators, each offering the designer aparticular combination of performancecharacteristics from which to select the bestunit for the application. Many specials areproduced in addition to the cataloguedoptions.

11-818

Compact, high precision regulatorsfor air gauging, laboratory use and precisepilot control.

11 400

For high accuracy pilot control oflarge regulators and relief valves.

R24 MICRO TROL

Exceptionally high flow with excel-lent relief performance.

R38

Instrument regulator produced inaluminium or stainless steel.

R27

High precision regulators featuring awide choice of operators.

SPECIALISED PRODUCTS

STAINLESS STEEL

Norgren produces units which meet NACErequirements for use offshore and in harshprocess environments. The 38 Seriesregulator and filter/regulator are 1/4 NPTunits offering high flow with good precision.The 22 Series filter, regulator and lubricatorare basic 1/2" and for lower flow applicationsthere is the 1/4" 05 Series.

WATER REGULATORS

Regulators with plastic or brassbodies suitable for general or potable waterduty.

RELIEF VALVES

In addition to the relief valves whichare part of the main FRL families Norgrenhas several specialised units including PopType and the air piloted 40AC.

ELECTRONIC REGULATORS

Norgren can offer fully program-mable electronic regulators for use with anystandard industrial PLC. The R26 Pneu-Statelectronic regulator gives stable output overlong periods and is ideal for closed looppressure control in applications such aswelding machines which require manydifferent pressure settings.

21

GLOSSARY

After Cooler:A heat exchanger mounted on acompressor outlet to extract the heatof compression.

Ambient:The conditions, usually temperature,in the vacinity of the equipmentunder normal working conditions.

Back Pressure Regulator:A device connected to a system insuch a way that the system pressureis held effectively constant bycontrol of the outlet flow to atmos-phere.

Check Valve:A device which allows flow in onedirection only.

Coalescing:The action causing small particles tounite to form larger particles.

Deliquescent Dryer:A dryer using material whichabsorbs water vapour to such anextent that the material ultimatelydissolves into the water it absorbs.

Desiccant:An adsorbing material used in somedryers. Many such dryers areregenerative in that they use some oftheir energy to dry the materialmaking it suitable for reuse.

Drip Leg Drain:A device at the bottom of a down legfrom a distribution main or a systemlow spot to remove condensed waterfrom the system. Such devices arenormally fitted with automatic drainvalves.

Dump Valve:A valve which is connected toatmosphere in such a way as torapidly exhaust the system pressure.

Emulsion:A mixture of oil and water.

Failure Flow:The maximum flow through a deviceat a given pressure with the valveopen to maximum extent.

Flow Characteristics:A characteristic of a pressureregulator which shows the variationof outlet pressure with varying outletflow rates at a constant supplypressure.

Free Air:Air flow measure in dm3/s at STP(1 013mbar and 21°C) (ISO R554).All air flows are converted to this tomake system sizing easier.

Initial Droop:The amount of pressure dropincurred by a pressure regulator ingoing from a flow (static) conditionto a small flow (dynamic) condition.

Micro-Fog:A suspension of light oil fractions inair, typically less than 2 µm in sizewhich can travel long distances,through complex passageways.

Micron (micrometre):A measurement of size on millionthof a metre (symbol µm).

Oil-Fog:A suspension of oil fractions in air,heavier and larger than Micro-Fog,suitable for heavy duty lubrication.

Pilot Operated Regulator:A regulator which has its outletpressure controlled by the outletpressure of another (piloting)pressure regulator, and not by anintegral adjustable spring load aswith standard pressure regulators.

Porting Block:A modular device for allowingseveral air take-off from a main airflow control set.

Pressure Drop (Droop):The amount of pressure lossincurred by the flow of air through adevice.

Pressure Reducing Valve/PressureRegulator:A device which is used to lower airpressure in a pneumatic system to adesired working level.

Regulation Characteristic:A characteristic of a pressureregulator which shows the variationof outlet pressure with varying inletpressure at a constant flow rate.

Relative Humidity:The ratio of the actual amount ofwater vapour present in a givenvolume of air, to the amount of watervapour necessary to saturate thesame volume of air at the sametemperature.

Soft Start Valve:A device which on initial pressurisa-tion of a system allows the pressureto build up slowly to a pre-deter-mined intermediate level beforeallowing a step-up to full linepressure to be achieved.

22

REFERENCE TABLES

23

Figure 37.

FRICTION LOSS IN PIPE FITTINGS IN TERMS OF EQUIVALENTMETRES OF STRAIGHT PIPE.

8 mm 10 mm 15 mm 20 mm 25 mm 32 mm 40 mm 50 mm

Tee (straight through) 0,15 0,15 0,21 0,34 0,46 0,55 0,67 0,92

Tee (side outlet) 0,76 0,76 1,01 1,28 1,62 2,14 2,47 3,18

90° elbow 0,43 0,43 0,52 0,64 0,79 1,07 1,25 1,59

45° Elbow 0,15 0,15 0,24 0,30 0,38 0,49 0,58 0,73

Ball valve* 0,01 0,03 0,09 0,12 0,15 0,22 — —

* Self exhausting – full open

Figure 38.

MAXIMUM RECOMMENDED FLOW * THROUGH ISO 65 MEDIUMSERIES STEEL PIPE.

Applied Nominal Standard Pipe Size (Nominal Bore) – mmGauge 6 8 10 15 20 25 32 40 50 65 80Pressure Approximate Pipe Connection – inchbar 1/8 1/4 3/8 1/2 3/4 1 1 1/4 1 1/2 2 2 1/2 3

0,4 0,3 0,6 1,4 2,6 4 7 15 25 45 69 120

1,0 0,5 1,2 2,8 4,9 7 14 28 45 80 130 230

1,6 0,8 1,7 3,8 7,1 11 20 40 60 120 185 330

2,5 1,1 2,5 5,5 10,2 15 28 57 85 170 265 470

4,0 1,7 3,7 8,3 15,4 23 44 89 135 260 410 725

6,3 2,5 5,7 12,6 23,4 35 65 133 200 390 620 14085

8,0 3,1 7,1 15,8 29,3 44 83 168 255 490 780 14375

10,0 3,9 8,8 19,5 36,2 54 102 208 315 605 965 14695

*Air flow rates in dm3/s free air at standard atmospheric pressure of 1 013 mbar.General notes

The flow values are based on a pressure drop (DP) as follows:10% of applied pressure per 30 metres of pipe 6 – 15 mm nominal bore inclusive5% of applied pressure per 30 metres of pipe 20 – 80 mm nominal bore inclusive

Figure 39.

DRYER COMPARISONDryer Type Pressure Atmospheric Drying Media Power Initial Cost Pre Filters After Filters Maintenance

Dew Point Dew Point Replacement Consumption Cost

Refrigerated 2°C –23°C Nil For Medium General purpose None Regular refrigeration and coalescing maintenance

motor of refrigeration

Regenerative –40°C –57°C Infrequent For drying High General purpose Coalescing SmallDesiccant desicant and coalescing

Deliquescent 10°C –15°C Regularly, Nil Low General purpose Coalescing Rechargingminimum and container6 monthly coalescing

Norgren is a leading world manufacturer

and supplier of pneumatic solutions,

offering a comprehensive range of

pneumatic control and automation

components via a global sales and

service network which covers 70

countries worldwide. The company is

a principal member of the diverse and

internationally successful £1 billion

IMI Group

a subsidiary of IMI plc

For further details, contact your local Technical Sales Centre on 0345 662266IMI Norgren Limited

PO Box 22, Eastern Avenue, Lichfield, Staffordshire, WS13 6SBhttp://www.norgren.com

‘Olympian’, ‘Excelon’, ‘Quikclamp’, ‘Micro-Fog’, ‘Ultraire’, ‘Puraire’, the Roundel, ‘Norgren’ and ‘IMI’ are registered trade marks.© IMI Norgren Limited 1997

Due to our policy of continued development, Norgren reserve the right to change specifications without prior notice.

BSI

NATIONALACCREDITATION

OF CERTIFICATIONBODIES

Certificate No. FM 20822

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