Std-141

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OISD 141

FOR RESTRICTEDCIRCULATIONNo.

DESIGN AND CONSTRUCTION REQUIREMENTS

FOR

CROSS COUNTRY HYDROCARBON PIPELINES

OISD STANDARD 141

First Edition, April 1990

OIL INDUSTRY SAFETY DIRECTORATEGovernment of India

Ministry of Petroleum & Natural Gas

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OISD STANDARD - 141First Edition April 1990

FOR RESTRICTEDCIRCULATION

No.

DESIGN AND CONSTRUCTION REQUIREMENTS

FOR


Prepared by

COMMITTEE ONDESIGN AND INSPECTION OF

PIPELINES

OIL INDUSTRY SAFETY DIRECTORATE2ND FLOOR, “KAILASH”

26, KASTURBA GANDHI MARGNEW DELHI -110001

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NOTE

OISD publications are prepared for use in the oil and gasindustry under Ministry of Petroleum & Chemicals. These are theproperty of Ministry of Petroleum & Chemicals and shall not bereproduced or copied and loaned or exhibited to others withoutwritten consent from OISD.

Though every effort has been made to assure the accuracy andreliability of the data contained in these documents. OISD herebyexpressly disclaims any liability or responsibility for loss or damageresulting from their use.

These documents are intended to supplement rather than

replace their prevailing statutory requirements.

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FOREWARD

The Oil Industry in India is 100 years old. Due to variouscollaboration agreements, a variety of international codes, standards andpractices are in vogue. Standardisation in design philosophies andoperating and maintenance practices at a national level was hardly inexistence. This, coupled with feed back from some serious accidents thatoccurred in the recent past in India and abroad, emphasised the need forthe industry to review the existing state of art in designing, operating andmaintaining oil and gas installations.

With this in view, the then Ministry of Petroleum and Natural Gas in1986 constituted a Safety Council assisted by Oil Industry SafetyDirectorate (OISD) staffed from within the industry in formulating andimplementing a serious of self regulatory measures aimed at removing

obsolescence, standardising and upgrading the existing standards toensure safer operations. Accordingly OISD constituted a number of Functional Committees comprising of experts nominated from theindustry to draw up standards and guidelines on various subjects.

The present standard on “Design and Construction Requirementsfor Cross Country Hydrocarbon Pipelines” was prepared by the FunctionalCommittee on “Design and Inspection of Pipelines”. This standard isbased on the accumulated knowledge and experience of industrymembers and the various national and international codes and practices. This standard is meant to be used as a supplement and not as areplacement for existing codes and practices. It is hoped that the

provision of this standard if implemented objectively, may go a long wayto improve the safety and reduce accidents in the Oil and Gas Industry.Users are cautioned that no standard can be a substitute for the judgement of responsible and experienced engineer. Suggestions areinvited from the users after it is put into practice to improve the standardfurther. Suggestions for amendments to this standard should beaddressed to the Coordinator, Committee on Inspection of “Design andInspection of Pipelines”, Oil Industry Safety Directorate, 2nd Floor, “Kailash”,26, Kasturba Gandhi Marg, New Delhi-110 001.

This standard in no way supersedes the statutory regulations of Chief Controller of Explosive (CCE), Factory Inspectorate or any otherStatutory body which must be followed as applicable.

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COMMITTEEON

DESIGN AND INSPECTION OF PIPELINES

List of Members

--------------------------------------------------------------------------------------------------------------------------------------Name Designation & Position in

Organisation Committee--------------------------------------------------------------------------------------------------------------------------------------

1. Sh.V.T. Karode Chief Engr. (P/L), OIL Leader

2. Sh.R.A. Shanbhag GM (Proj), IOCL (P/L) Member/Leader *

3. Sh.Rao Rudravajala COM, IOCL (P/L) Member

4. Sh.S.K. Goyal DGM, ONGC Member

5. Sh.C.N. Char CE (C & M), ONGC Member

6. Sh.E.M Bhumgara DGM, (T&P/L), HPCL Member

7. Sh.R.K. Mulla COM (P/L), HPCL Member

8. Sh.R.K. Dhadda Manager (P/L), EIL Member

9. Sh.G.V.S. Saiprasad Sr. Manager (P/L), GAIL Member

10. Sh.K.K. Dutta Dy.CE (P/L), OIL Member

11. Sh.R.K. Baruah SE (M), OIL Member

12. Sh.M. Bhandari Jt.Director, OISD Member Co-Ordinator

--------------------------------------------------------------------------------------------------------------------------------------In addition to the above, several other experts from the industry contributed in the preparation, reviewand finalisation of this document.

*(Took over as Leader w.e.f June/89 on Shri Karode’s retirement from Oil India Ltd).

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DESIGN AND CONSTRUCTION REQUIREMENTSFOR


CONTENTS

SECTION PAGE NO.

PART-I Liquid Petroleum Transportation Systems

1.0 Introduction, Scope and Definitions

2.0 Design

3.0 Materials

4.0 Dimensional Requirements

5.0 Construction, Welding and Assembly

6.0 Inspection and Testing

7.0 Operation and Maintenance Procedures

8.0 Corrosion Control

Appendix - A

Appendix - B

PART-II Gas Transportation Systems

9.0 Scope, General Provisions and Definitions10.0 Materials and Equipment

11.0 Welding

12.0 Piping System Components and Fabrication Details

13.0 Design, Installation and Testing

14.0 Operating and Maintenance Procedures

15.0 Corrosion Control

16.0 Miscellaneous

Appendix - C

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DESIGN AND CONSTRUCTION REQUIREMENTSFOR


PART-I LIQUID PETROLEUM TRANSPORTATION

SYSTEMS

1.0 INTRODUCTION, SCOPE ANDDEFINITIONS (B 31.4-CHAPTER I)

1.1 INTRODUCTION

Safety in petroleum installations andpipelines comes through continuous efforts atall stages and as such it can be ensured byobserving that installations and pipelines aredesigned, constructed and tested as per recognised engineering standards and they areperiodically inspected and maintained.

1.2 SCOPE

The minimum requirements for the design,materials, construction, assembly, inspection,testing and safety aspects of operation andmaintenance of piping transporting liquids suchas crude oil, condensate, natural gasoline,

natural gas liquids, liquefied petroleum gas(LPG) and liquid petroleum products betweenproducers lease facilities, tank farms, naturalgas processing plants, refineries, stations,terminals (marine, truck and rail) and other delivery and receiving points shall be governedby American National Standard Code for Pressure Piping ASME/ANSI B 31.4 - 1986Edition "Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous, Ammonia and Alcohols" with thefollowing additions, exceptions andmodifications. All requirements contained in

the code ASME/ANSI B 31.4 shall be fully validunless cancelled, replaced or amended in thisstandard. Only those clauses of Code ASME/ANSI B 31.4, which are cancelled,replaced or amended, are referred herein.Clause numbers of Code ASME/ANSI B 31.4are included in the parenthesis. Whenever anyreference is made to the ASME/ANSI B 31.4’sundermentioned clauses in Code B 31.4 or inany other code incorporated into ASME/ANSI B31.4 by reference, the undermentioned clausesof this standard shall be referred.

For convenience 'ASME/ANSI Code B31.4 herein after is referred' as 'B 31.4'.

Note: For the design, material, construction,assembly, inspection, testing and safetyaspects of operation and maintenance of 'Submarine Pipeline Systems' the ' Rules For Submarine Pipeline Systems', Det NorskeVeritas (DNV) 1981 shall be followed asguideline standard together with established

industry practice. A 'Submarine PipelineSystem' by definition (Ref. DNV) is 'aninterconnected system of submarine pipelines,pipeline risers, their supports, all integratedpiping components, the corrosion protectionsystem and weight coating'.

1.3 DEFINITIONS (400.2)

Following definitions are added:

a) High vapour pressure (HVP) pipeline - Apipeline transporting hydrocarbons or

hydrocarbon mixtures in the liquid or quasi- liquid state with a vapour pressurein excess of 240 kPa (35psi) at 380C(1000F).

b) Low Vapour Pressure (LVP) pipeline - Apipeline transporting hydrocarbons or hydrocarbon mixtures in the liquid or quasi-liquid state with a vapour pressureof 240 kPa (35psi) or less at 380C (1000F).

c) Multiphase fluids - Multiphase fluidsmeans oil, gas or water in any

combination produced from one or moreoil wells or recombined oil well fluids thatmay have been separated in passingthrough treatment/processing facilities.For the purpose of this standard,multiphase fluids are considered to be lowvapour pressure fluids.

d) On shore - Areas not covered by'Offshore' as defined in B 31.4 clause400.2- Definitions is defined as 'Onshore'.The definitions of 'Offshore' as per B 31.4is reproduced hereunder for easy

reference: Offshore - Areas beyond the line of

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ordinary high water, along that portion of the coast that is in direct contact with theopen seas and beyond the line markingthe seaward limit of inland coastal waters.

e) Shall - The word 'Shall' is used to indicate

that the provision is mandatory.

f) Should - The word 'Should' is used toindicate that the provision isrecommendatory as sound engineeringpractices.

2.0 DESIGN (B 31.4 - CHAPTER-II)

2.1 DYNAMIC EFFECTS (401.5)

The following paragraph is added:

Other Loadings:

Unusual loadings such as those caused byscour, erosion soil movement and slides,installation forces, vortex shedding and other phenomena shall be considered and providedfor in accordance with sound engineeringpractice.

2.2 WEIGHT EFFECTS (401.6)

Live Loads (401.6.1)

Weight of water during hydrostatic testingshall also be considered.

2.3 HVP PIPELINES - ZONE LOCATION(ADDITIONAL CLAUSE)

Zone locations as described in this clause shallapply only to HVP pipelines.

2.3.1 A Zone 1 location is an area extending 200metre on either side of the centreline of any continuous 1 km. length of pipelinethat contains 5 or fewer dwelling units

intended for human occupancy.'Offshore' shall be considered as Zone 1location.

2.3.2 A Zone 2 location is an area as defined inclause 2.3.1 above that contains morethan 5 dwelling units intended for humanoccupancy, or is a facility that contains20 or more persons during normal use.

2.3.3 Each dwelling unit in a multiple dwellingunit building shall be counted as aseparate unit.

2.3.4 When a facility creates a Zone 2 locationrequirements, the Zone 2 area shall

extend at least 200 meter from thatfacility.

2.3.5 While classifying the Zone locations, dueconsideration shall be given to thepossibility of future development of the

area. If at the time of planning a newpipeline this future development appearslikely to be sufficient to change the zonelocation, this shall be taken intoconsideration.

2.4 ALLOWABLE STRESS VALUES (402.3.1)

2.4.1 B 31.4 Clause 402.3.1 (a) is replaced bythe following clause:

The allowable stress value S to be used for design calculations in B 31.4 clause 404.1.2 for

new pipe of known specification shall beestablished as follows:

S = F X E X Specified Minimum Yield Strengthof the pipe in psi (MPa)

where

F = Design factor in accordance with Table 2.4of this standard.

In setting design factor, due consideration hasbeen given to and allowance has been made for underthickness tolerance and maximumallowable depth of imperfections provided for inthe specifications approved by B 31.4.

E = Weld joint factor (in accordance withB 31.4 clause 402.4.3 and Table 402.4.3)

Table 2.4-------------------------------------------------------------Pipeline Category F-------------------------------------------------------------LVP 0.72HVP, Zone 1 0.72HVP, Zone 2 0.576

-------------------------------------------------------------Note: The allowable stress values given in

B 31.4 Table 402.3.1(a) shall not be validas the same shall stand modified for different values of design factor (F) givenin Table 2.4 of this Standard.

2.4.2 B 31.4 clause 402.3.1(c) is replaced bythe following clause:

The allowable stress value S to be usedfor design calculations in B 31.4 clause 404.1.2

for new or used (reclaimed) pipe of unknown or ASTM A120 specification shall be established in

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accordance with the following and limitation inB 31.4 clause 405.2.1(c).

S = F X E X Minimum yield strength of the pipein psi(MPa)[24,000 psi(165MPa) or yieldstrength determined in accordance with

B 31.4 clause 437.6.6 & 437.6.7].

Where

F = Design factor determined from Table 2.4 of this standard.

E = Weld joint factor (See Table 402.4.3 of B 31.4).

2.5 CORROSION (402.4.1)

The clause is modified as under:

A corrosion allowance on the design wallthickness need not be made unless internal or external corrosion is expected, nor is anallowance required where a corrosive fluid is tobe transported or soil conditions are conduciveto corrosion, or both, provided the pipe andcomponents are protected against corrosion inaccordance with the requirements andprocedures prescribed in Chapter VIII of B 31.4.

Where there is a possibility of internalcorrosion taking place, a corrosion allowanceshould be made. Such corrosion allowanceshall provide that the increase in wall thicknessis additional to the wall thickness requirementfor pressure. The allowance should be basedupon a specialist investigation of the corrosiveprocess involved and will also be influenced bythe required life of the pipeline.

2.6 PRESSURE DESIGN OF COMPONENTS(404)

Straight Pipe (404.1)

Following requirement is added to B 31.4

clause 404.1.1:

The least nominal wall thickness (tn) for steel pipe, as indicated in B 31.4 clause 404.1.1shall not be less than the dimensions indicatedin the specifications for line pipe approved by B31.4. Further, pipe having a D/tn ratio greater than 150 shall not be used, where D = outsidediameter of pipe.

2.7 BENDS MADE FROM PIPE (406.2.1)

B 31.4 clauses 406.2.1 (b) and 406.2.1 (c)

are cancelled and replaced by following:

The minimum radius of field cold bendsshall be as follows: _____________________________________ Nominal Pipe size Minimum Radius of Bend

in in Pipe Diameter _____________________________________

NPS 12 and smaller 21DNPS 14 u/i 18 30DNPS 20 and larger 40D _____________________________________

2.8 MITERED BENDS (406.2.2)

A mitered bend is not permitted with theexception of deflections upto 3 degrees that arecaused by misalignment.

2.9 VALVES (407)

B31.4 clause 407.1 (b) is cancelled andreplaced by the following:

Valves having shell (body, bonnet, cover and/or end flanges) components made of caseiron or ductile iron shall not be used.

2.10 THREADED JOINTS (414)

Following paragraph is added:

Threaded joints shall not be used in

a) HVP pipelinesb) Buried Multiphase pipelinesc) Offshore pipelines

2.11 SLEEVE, COUPLED, AND OTHERPATENTED JOINTS (418)

The following clause is added:

HVP Pipelines

Sleeve, coupled and patented joints shall notbe used on HVP Pipelines.

2.12 PROPERTIES (419.6)

Stress Valves (419.6.4)

Add the following para in B31.4 clause419.6.4 (a) 'General'. Consideration shall begiven to the use of lower allowable designstresses if there is the likelihood of repeatedstress changes giving rise to fatigue conditions.

2.13 DESIGN OF PIPE SUPPORTINGELEMENTS (421).

Supports, Braces and Anchors (421.1)

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2.13.1 Clause 421.1 (c) add as below:

Wherever non integral attachments,such as pipe clamps and ring girdersare used, adequate precautions shallbe taken to prevent corrosion at or near

the contact points.

2.13.2 Clause 421.1 (d) stands modified asunder:

If a pipeline is designed to operate atstress level of more than 50% of thespecified minimum yield strength of thepipe, all connections welded to the pipeshall be made to a separate cylindricalmember which completely encircles thepipe, and this encircling member shallbe welded to the pipe by continuous

circumferential welds at both ends.

3.0 MATERIALS (B31.4 - CHAPTER-III)

3.1 LIMITATIONS ON MATERIALS (423.2)

Following clauses are added to B 31.4 clause423.2.1

Notch Toughness Requirements (Additionalclause)

3.1.1 For steel pipe and associated steelcomponents in LVP pipeline systems of all sizes and in HVP pipeline systemssmaller than 2" NPS, no proven notchtoughness shall be mandatory.

3.1.2 For steel pipe and associated steelcomponents in HVP pipeline systems of 2" NPS and larger, notch toughnessproperties shall be specified based onthe design operating stress and thelowest expected operating temperature.

3.1.3The lowest expected operatingtemperature shall be taken lowest

expected operating or metal temperaturewhen the hoop stress exceeds 50MPa(7000psi), having due regard to pastrecorded temperature data, the minimumfluid temperature that may occur, and theeffect of lower ambient temperatures in thearea.

3.2 STEEL (423.2.3)

Following clauses are added:

3.2.1 Carbon Equivalent shall be calculated

based on the formula given below:

CE = C + Mn + Cr+Mo+V + Ni+Cu6 5 15

3.2.2 Additional test requirements shall bespecified as per Appendix-B of Part-I of this standard for steel pipes

manufactured by Electric ResistanceWelding and/or Electric Inductionwelding.

3.3 MATERIALS FOR SOUR MULTIPHASESERVICE (ADDITIONAL CLAUSE)

3.3.1 Definition:

NACE Standard MR-OI-75 'Sulfide StressCorrosion Cracking Resistant Metallic Materialsfor Oil Field Equipment defines limitingconcentrations on hydrogen sulphide in the

fluid transported' for it to be considered as sour service.

Note: While past experience has indicated thisto be the accepted minimumconcentration at which sulphide stresscorrosion cracking may occur, thepresence of other constituents in thephases making up the multiphase fluid,such as carbon dioxide in the gas andsalt in the water or larger amounts of free water or gas, may cause problemsto occur at lower concentrations of hydrogen sulphide.

3.3.2 General

In addition to these applicablerequirements of B31.4 and this standard, allmaterials used in sour multiphase service shallmeet the following requirements.

3.3.2.1 Pipe, valve, fittings, flanges bolting andother equipment exposed to or whichare necessary to contain sour multiphase fluids may be susceptiblestress corrosion cracking and hydrogen

induced stepwise cracking and thusdue consideration shall be given tomaterial selection in design.

3.3.2.2 Materials for sour multiphase serviceshall conform to the requirements of NACE Standard MR-01-75, 'SulphideStress Corrosion Cracking ResistantMetallic Material for Oil FieldEquipment'. Depending upon theservice and the materials involved, theSulphide Stress Corrosion Cracking(SSCC) and Hydrogen Induced

Cracking(HIC) tests should beconducted as per NACE standards

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referred in Appendix A of this standard.The acceptance criterias shall be basedon current established industrypractice.

3.3.2.3 Pressure containing components

(excluding pipe) intended for sour multiphase service shall be fullyidentified with a permanent marking.

3.3.3 Pipes made of cast iron, ductile iron,bronze and other copper basedmaterials shall not be used in sour multiphase service.

4.0 DIMENSIONAL REQUIREMENTS(B31.4 - CHAPTER-IV)

All provisions of B 31.4 Chapter IV shall apply.

5.0 CONSTRUCTION, WELDINGAND ASSEMBLY (B31.4 –CHAPTER-V)

5.1 LOCATION (434.3.1)

Following paragraph is added

The location of a new undergroundpipeline, when running parallel to an existingunderground pipeline, should be at a minimumclear distance of 5.0 meter from the existing

underground pipeline when heavy conventionalconstruction equipment is excepted to beutilized. This distance may be reduced after careful assessment of constructionmethodologies. Such that it does not result inunsafe conditions during construction. In anycase the minimum clear distance shall not beless than 3.0 meter. These areas shall bedistinctly identified on ground duringconstruction.

No pipeline should be located within 15.0meter of any private dwelling or any industrial

building or place of public assembly in whichpersons work, congregate or assemble, unlessit is provided with at least 300 mm of cover inaddition to that provided in Table 5.3.3 of thisstandard.

5.2 HANDLING, HAULING, STRINGINGAND STORING (434.4)

The following paragraph is added:Pipe shall not be strung along the right of

way in rocky areas where blasting may berequired, until all blasting is complete and the

area cleared of all debris. Material other thanline, pipe shall not be strung on the right of waybut shall be transported to site for use only at

the time of installation.

5.3 DITCHING (434.6)

5.3.1 Following is added to B 31.4 clause 434.6(b)

The width of trench shall be such that aminimum clear distance of 200mm for trench normal soil and 300mm for trenchin rock is maintained between edge of pipe and the trench wall at the bottom of trench.

5.3.2 The following paragraph is added:

Pipelines shall be buried below groundlevel, unless construction above groundis found to be desirable for exceptionaltechnical, economic or topographical

reasons.

5.3.3 Minimum cover for Buried Pipelines [Table434.6(a)]

B 31.4 Table 434.6(a) stands cancelled and isreplaced by Table 5.3.3 given below.

TABLE 5.3.3Minimum Cover for Buried Pipelines

____________________________________ Location Minimum Cover in meter ____________________________________ Industrial, Commercial 1.0 (2)and Residential AreasStream, Canal and other minor 1.5 (3)water crossingsDrainage ditches at roadways 1.0and railroadsRocky Areas 1.0Uncased/Cased Road 1.2 (1)CrossingsRailroad Crossings 1.4 (1)Other Areas 1.0------------------------------------------------------------

1. Cover shall be measured from the top of

road or top of rail, as the case may be.

2. Minimum cover for pipelines transportingLPG and other HVP liquids shall be 1.2meter of normal excavation in zone 2 areas.

3. In case of rivers/water bodie, which areprone to scour and erosion, adequatelysafe cover (minimum 1.5 meter) shall beprovided below the predicted scour profileexpected during the life time of the pipeline.

5.4 BENDS, MITERS AND ELBOWS

(434.7)

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Bends made from pipe (434.7.1)

5.4.1 Clause 434.7.1 (d) is modified asfollows:

The ends of each bent length shall be

straight and not involved any way in thebending. The length of the straightsection shall permit easy jointing.Tangents approximately 1 meter inlength shall be provided on both ends of cold bends. A field bend shall not bemade within two pipe diameters of a fieldweld, which has already been made.

5.4.2 Pipes with longitudinal welds shall bebent in such a way that weld lies in theplane passing through neutral axis of thebend which shall be installed positioning

the longitudinal weld in the upper quadrants.

5.5 INSTALLATION OF PIPE IN THEDITCH (434.10)

The following paragraphs are added:

Before lowering operations arecommercial particular attention shall be paid tothe suitability of the trench to allow the pipelineto be lowered without the coating beingdamaged and to give a reasonably evensupport to the pipeline.

When already coated pipes are beinglowered, a complete check of the pipe coatingand field joint coating shall be carried out andall damages repaired.

Wherever pipeline is laid under tensionas a result of an assembly error(for exampleincorrect positioning of bends, either horizontalor vertical), the trench shall be rectified or inexceptional cases a new assembly shall becarried out so that it fits the excavation and thelaying bed.

Care must be taken that during laying, thedeformation caused during the raising of thepipe from the support does not exceed thevalues for the minimum allowable radius of elastic curvature, so as to keep the stresses inthe steel pipe and on the coating within safelimits.

In laying parallel pipelines in the sametrench, the minimum clear distances betweenthe pipelines shall be 500mm.

5.6 SPECIAL CROSSINGS (434.13)

5.6.1 Water crossings (434.13.1)

The following is added:

Special considerations shall be requiredfor submerged crossing by pipelines of rivers

which are characterized by their perennialnature, meandering course, steep andpotentially erodable banks, potentially scouringbed, large erodable flood plain and wide water course (high water mark to high water mark)both during the design and installation of suchcrossings.

For river crossing such as those describedand established as above the followingadditional requirements are to be considered.

a) Hydrological and geotechnical surveys to

establish the river bed and water currentprofiles to predict the behaviour of theriver with respect to change of course,scour of bed and erosion of banks and toobtain all other parameters related todesign and installation of such crossings.

b) The pipeline at such crossings shall beinstalled with extra depth of cover. Thecover provided shall be adequate toprevent exposure of the pipeline for theentire design life of the pipeline.

c) To ensure the stability of the underwater pipeline. It may be necessary to addweight to sink and hold the pipeline inposition.

d) A heavier wall thickness pipe shall beprovided for the river crossing section.

e) A detailed stress analysis for the pipesection for river crossings should becarried out, taking into consideration theeffect of all loads during laying and itshall be ensured that the stresses remainwithin permissible limits in accordance

with B 31.4.

f) Whenever considered desirable, thesection of the pipeline corresponding tothe river crossing should beforeinstallation be subjected to hydrostaticpre-testing. However, the completepipeline corresponding to river crossingshall be tested after installation.

5.6.2 Crossing of or by Utilities (AdditionalClause)

5.6.2.1 A minimum clearance of 300mm shallbe maintained at the point of crossing

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and the utility or pipeline shall beinstalled at a uniform depth for the fullwidth of the right of way, provided that,where it is not practicable to obtain theabove mentioned clearance specialdesign and construction shall be used.

5.6.2.2 A clearance sufficiently large to avoidelectrical fault current interference shallbe maintained between the pipeline andthe grounding facilities of electricaltransmission lines.

5.6.2.3 Interference with, or from, other systemsthrough the application of cathodicprotection shall be dealt with by mutualaction of the parties involved.

5.6.2.4 When laid parallel to , along or near

underground power and/or communication cables, conductors or conduit, underground pipes shallmaintain a horizontal clearancebetween vertical planes through theadjacent external surfaces on thepipelines and cables, conductors or conduct, or structures of theunderground utility of at least 300 mm.Where these clearances cannot bemaintained, extra precaution shall betaken to ensure the maximum possibleclearance and to prevent future contact.If pipelines and communication and/or power utilities share the same trench,the above horizontal clearance shall bemaintained with the pipeline preferablyat a lower level.

5.6.2.5 A minimum separation of 3.0 metreshould be maintained between pipelineand transmission tower, footings,ground cables and counter poise.Regardless of separation, considerationshould always be given to lightningfault current protection of pipelines andsafety of personnel.

5.6.3 All crossings shall be made in such amanner that the angle between thecenterline of the railway, highway, river,stream, canal or utility being crossedand the centerline of the pipeline shallbe as close as possible to 90 but in nocase less than 45.

5.7 BLOCK AND ISOLATING VALVES(434.15)

Following requirements are added for HVP

pipelines:

5.7.1 Requirements of Mainline valves for piping systems transporting LPG asgiven in B 31.4 shall be fully applicableto all piping systems transporting HVPliquids.

5.7.2 Valves shall be installed outside cities,towns and villages at the transition fromZone 1 to Zone 2. In Zone 2 themaximum spacing between valves shallnot exceed 12 K.M.

5.8 PUMP STATION, TANK FARM ANDTERMINAL CONSTRUCTION (434.20)

5.8.1 Location (434.20.2)


Minimum distances from property linesand road allowance limits to buildings andequipment etc. shall meet the requirements of OISD Standard 118 "Layouts for Oil and GasInstallations".

5.8.2 Pump Station, Tank Farm andTerminal Piping (434.20.5)

All HVP piping and components shall bedesigned to Zone 2 stress levels as defined inthis standard.

5.9 AND WORKING TANKAGE STORAGE(434.21)

Underground Storage (Additional Clause)

Prior to design and construction of anunderground storage chamber, an engineeringand geological investigation shall be carried outto determine the feasibility of such a system atthe proposal site. Such chambers shall beconstructed and operated in accordance withGPA Publication 8175, Method for UndergroundStorage of National Gas Liquids

5.10 ASSEMBLY OF PIPING COMPONENTS(435)

Auxiliary Liquid/Petroleum or LiquidAnhydrous Ammonia Piping (435.5)

The requirements covered in this clauseB31.4 shall be fully applicable to HVP pipelinesalso.

6.0 INSPECTION AND TESTING(B31.4-CHAPTER-VI)

6.1 TYPE AND EXTENT OF EXAMINATIONREQUIRED (436.5)

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Construction [436.5.1 (b)]


6.1.1 Field pipeline coating shall be applied

on a properly prepared surface andvisually inspected during application. Any cutting or removal of the coatingshall be promptly and carefullyrepaired.

6.1.2 Yard-coated pipe shall be examined after field bending to ensure that the qualityof the coating has not been impaired.

6.1.3 Additional precautions such as doublecoating, rock shield, selected backfill,and ditch padding shall be taken where

conditions are such that damage to thepipe coating could occur.6.1.4 If moisture is present on the surface of

the pipe, no coating materials shall beapplied.

6.1.5 Unless special procedures can betaken, no coating shall be applied whenthe ambient temperature might have adetrimental effect on the coating either during or after application.

6.2 TESTING (437)

6.2.1 General (437.1)


All sections which have been previouslyhydrostatically tested viz. road/rail crossingsand river crossings shall be retested alongwiththe completed mainline sections.

A gauging pig shall be passed throughthe pipeline to prove the internal diameter of theentire line. The gauging plate shall have adiameter of 95% of the internal diameter of the

pipeline.

When water is used as the test medium,inhibited water, i.e. water to which suitabledoses of corrosion inhibitors are addeddepending upon quality of water, shall be used.

6.2.2 Test Pressure (437.4)

Hydrostatic Testing of Internal PressurePiping (437.4.1)

Following amendment is made to B31.4

clause 437.4.1(a). The duration of hydrostaticproof test shall be minimum 24 hours.

Following requirement is added for HVPpipelines.

For Zone 2 HVP pipelines, the minimumpressure for hydrostatic proof test shall be 1.4times the internal design pressure and the

minimum pressure for leak test shall be 1.1times the internal design pressure.

6.2.3 Acceptance of Test (Additional Clause)

The test is successful when the pipelinehas withstood the strength and leak tests andduring the test period there is no observabledrop in pressure that cannot be accounted for by temperature changes.

6.2.4 Termination of Testing (AdditionalClause)

The pipeline shall be slowlydepressurized at a moderate and constant rate.During dewatering, care shall be taken toproperly dispose the discharging water in order to avoid pollution, damages to fields under cultivation and/or existing structures andinterference with the traffic.

6.2.5 Pre- tested Pipe (Additional Clause)

Pipe used for making repairs shall bepre-tested to a pressure equal to or greater thanthe original pipeline strength test pressure.

6.2.6 Preservation of Pipeline (AdditionalClause)

If the pipeline is to be preserved for aspecified duration before it can becommissioned, the pipeline shall be completelyfilled with water with sufficient quantities of corrosion inhibitors depending upon the qualityof water and the period of preservation and at asuitable pressure.

6.3 COMMISSIONING ADDITONAL

CLAUSE)

6.3.1 Commissioning shall consist of displacing the hydrostatic test water from the pipeline by pumping in theliquid to be transported. Batching pigsor spheres shall be used not only tominimize mixing at the interface but alsoto enable the progress of the interface tobe followed.

6.3.2 In cases where the water has to becleared from the pipeline before

commissioning because of possiblechemical or physical action between the

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water and the liquid to be transported,the pipeline shall be first drained andthen dried as thoroughly as possible. After drying, the pipeline shall be filledwith the liquid. Care shall be taken toclear pockets of water from valves and

fittings.

6.4 RECORD (437.7)

The following is added as an additionalrequirement

Pipe Book

A pipe and welding book shall bemaintained for all projects. The purpose of thepipe book shall be to indicate and maintain as apermanent record the exact position in the

pipeline of each pipe length and each pipelinematerial like valves, scraper traps, bends,flanges, and other fittings installed in theproject. Each item shall be recorded by itsidentification number. Location of each weldincluding weld number, welder number, type of welding and electrode, weld treatment anddetails of equipment used for radiography shallbe recorded in the pipe book.

7.0 OPERATION AND MAINTENANCEPROCEDURES (B31.4-CHAPTER-VII)

All provisions of B 31.4-Chapter-VII shall apply.

8.0 CORROSION CONTROL (B31.4-CHAPTER-VIII)

8.1 PROTECTIVE COATING (461.1.2)

a) The following is added to clause 461.1.2 (a)of B 31.4:

Coatings shall electrically isolate theexternal surface of the piping system from

the environment.

b) The following paragraph is added:

All joints, fittings, repairs and tie-insshall be coated with a material compatiblewith the existing coating.

8.2 CATHODIC PROTECTION SYSTEM(461.1.3)


a) Existing Bare Pipelines Systems

Investigation shall be made to determine

the extent or effect, of corrosion on existingbare pipeline systems. When theseinvestigations indicate that continuingcorrosion will create a hazard, corrosioncontrol measures or other remedial actionshall be undertaken.

b) Cathodically Protected Pipeline SystemsTemporarily Out of service.

Cathodic Protection system shall bemaintained on any pipeline that istemporarily out of service.

8.3 ELECTRICAL ISOLATION (461.1.4)

The following is added to clause 461.1.4 (b) of B 31.4

Whereas such insulating devices areinstalled, they shall be properly rated for temperature, pressure, electricalproperties, and shall be resistant to thecommodity carried in the pipelinesystems.

8.4 TEMPORARY CATHODIC PROTECTIONSYSTEM (ADDITIONAL EQUIREMENT)

When considered necessary a temporary

cathodic protection system with sacrificialanodes shall be installed to ensure adequateprotection of pipeline from external corrosionfrom the time the pipeline is laid in the trench tillthe permanent cathodic protection system iscommissioned.

The temporary C.P system shall preferablybe installed simultaneously keeping pace withthe pipeline laying/installation work and shall bemonitored periodically.

ANSI B31.4 APPENDIX-A

The following is added to B31.4 Appendix-A

List of numbers and subjects of thosestandards and specifications, which do notappear in the text of B 31.4, but may be of informational benefit.

DIN

30670 Polyethylene Sheathing of Steel Tubesand of Steel Shapes and Fittings.

30672 Corrosion Protection Tapes and HeatShrinkable Sleeves- Coatings madefrom Corrosion Protection Tapes and

Heat Shrinkable Sleeves for Underground Pipelines.

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AWWA

C203-86 Standard for Coal-Tar ProtectiveCoatings and Linings for Steel Water Pipelines-Enamel and Tap-Hot Applied.

BSI

BS 4146 Specifications for Coal-Tar Based Hot1987 Applied Coating Materials for protecting

iron and Steel, including suitablePrimers where required.

NACE

TM-01-77 Testing of Metals for Resistance toSulphide Stress Cracking at AmbientTemperatures.

TM-02-84 Testing of Metals for Resistance to

Stepwise Cracking.

Name and address of the organisationwhose standards and specifications appear above.

DIN: Deutsches Institute for NormungObtainable from:Foreign Standards DistributionBeuth Verlag GmbHBurggrafen Strasse 4-10D-1000 BERLIN 30

BSI British Standards Institution2, Park Street,London : WIA 2BSTelephone : 01-6299000Telex : 266933

AWWA American Water Works Association6666 West Quincy Avenue,Denver, Colorado 80235

APPENDIX - B (ADDED APPENDIX)

ADDITIONAL REQUIREMENTS FOR

ELECTRIC RESISTANCE/ELECTRICINDUCTION WELDED LINE PIPE

B.1 Reverse Bend Tests

Reverse bend tests shall be performedon the pipe piece cut from the crop end from thefront end of the first length and the back end of the last length produced from each coil. Thespecimen shall be 100mm to 115mm long andshall be reverse bend tested in accordance withprocedure given below and Figure B.1.

a) Selection of Mandrel

The reverse bend test shall be carried outwith a mandrel, who radius(R), width(A) shall becalculated for any combination of diameter, wallthickness and grade with the formula.

A = 2R = 1.4 (D-t) t------------- -t

e(D-2t)-1.4t where, D - Outside diameter of pipe

t - Wall thickness of pipe1.4 - Peaking factor e - Strain

Minimum values of 'e' shall be as follows:

Grade of Steel Min 'e' value------------------------------------------------------------- ASTM A53 B 0.1425 ASTM A 135 B 0.1425 API 5L B 0.1425 API 5L X-42 0.1375 API 5L X-46 0.1325 API 5L X-52 0.1275-------------------------------------------------------------

b) Procedure

The mandrel is to be plugged into thespecimen, with the weld in contact withmandrel, to such a depth that the angle of engagement between mandrel and specimenreaches 600 (see Fig. B1). If the combination of diameter and wall thickness of pipe, and radiusof mandrel is such that the angle of engagement does not reach 60, the mandrelshall be plugged into the specimen untilopposite walls of the specimen meet.

c) Acceptance Criteria

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A specimen which fractures completely prior to the specified engagement of mandrel andspecimen, or which reveals cracks and rupturesin the weld or heat affected zone longer than4mm, shall be rejected. Cracks less than 6mmlong at the edges of the specimen shall not be

cause for rejection.

B.2 Micrographic and HardnessExamination

A test specimen shall be taken acrossthe longitudinal weld from one length of finishedpipe from each lot of maximum 50 lengths fromthe same heat manufactured from the sameprocess.

These specimens shall be polished andetched for micro-examinations. Theexaminations shall provide evidence that heattreatment of weld zone is adequate and there isno untempered martensite left.

The Manufacturer shall make hardnessmeasurements on each specimen as indicatedin Fig. B.2 in accordance with ASTM E-32. Themaximum difference in hardness between basematerial and any reading taken in the heataffected zone shall be less than 80 pointsVicker's HV10.

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PART-IIGAS TRANSPORTATION SYSTEMS

9.0 SCOPE, GENERALPROVISIONS ANDDEFINITIONS

9.1 SCOPE

The minimum requirements for thedesign, fabrication, installation, inspection,testing and safety aspects of operation andmaintenance of gas transmission anddistribution systems including gas pipelines,gas compressor stations, gas metering and

regulation stations, gas mains and servicelines upto the outlet of the customer's meter set assembly shall be governed by AmericanNational Standard Code for Pressure Piping ANSI/ASME B 31.8-1986 Edition "GasTransmission and Distribution PipingSystems" with the following additions,exceptions and modifications. All requirementscontained in the Code ANSI/ ASME B 31.8shall be fully valid unless cancelled, replacedor amended in this standard. Only thoseclauses of Code ANSI/ ASME B31.8 which wascancelled, replaced or amended are referred

herein. Clause numbers of Code ANSI/ ASMEB 31.8 are included in the parenthesis.Whenever any reference is made to the ANSI/ASME B 31.8's undermentioned clausesin Code B 31.8 or in any other codeincorporated into ANSI/ ASME B 31.8 byreference, the undermentioned clauses of thisstandard shall be referred. For convenience, "ANSI/ ASME Code B 31.8"hereinafter is referred as 'B 31.8'.

NOTE : For the design, material, construction,

assembly, inspection, testing andsafety aspects of operationmaintenance of 'Submarine PipelineSystem' the 'Rules For SubmarinePipeline Systems' Det Norske Ventas(DNV) 1981 shall be followed asguideline standard together withestablished industry practice. A'Submarine Pipeline System' bydefinition (Ref. DNV) means 'aninterconnected system of submarinepipelines, pipeline risers, their supports, all integrated piping

components, the corrosion protectionsystem and weight coating'

9.2 PIPING SYSTEMS DEFINITIONS(803)

General Terms (803.1)

The following definition is added:

On shore-Areas not covered by 'Offshore' asdefined in B 31.8 clause 803.17 is defined as'Onshore'. The definition of 'Offshore' as per B31.8 is reproduced hereunder for easyreference:

'Offshore-Areas beyond the line of ordinaryhigh water, along that portion of the coast thatis in direct contact with the open seas andbeyond the line marking the seaward limit of inland coastal waters.'

10.0 MATERIALS AND EQUIPMENT(B 31.8 CHAPTER-I)

10.1 MATERIALS AND EQUIPMENT (810):

Following is added to Clause 810.1

When the maximum design temperatureexceeds 120 deg.C (250 deg. F), particular attention shall be given to the tensileproperties of the material to ensure that thederating for temperature specified by Clause841.11 of B31.8 is adequate.

10.2 Operating Conditions, Temperatureand Notch ToughnessRequirements (Additional Clause):

10.2.1 For steel pipes smaller than 2" NPSand steel valves, fittings and flangessmaller than 2" NPS, proven notchtoughness properties are notmandatory.

10.2.2 For steel pipes and associated steelcomponents of size 2" NPS and larger,Notch toughness valves shall bedetermined to provide protectionagainst fracture initiation andpropagation. Notch toughness valves(minimum absorbed energy valves)shall be specified based on the designoperating stress and the minimum

design temperature.

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12.0 PIPING SYSTEM COMPONENTSAND FABRICATION DETAILS(B31.8 CHAPTER-III)

12.1 VALVES AND PRESSURE

REDUCING DEVICES (831.1)

B 31.8 Clause 831.11(b) and(c) are cancelledand replaced by the following:

Valves having shell (body, bonnet, cover and/or end flanges) components made of castiron or ductile iron shall not be used in gaspiping systems.

Note:- Manufacturing standards for cast ironvalves viz. MSS-SP-70, MSS-SP-71and MSS-SP-78 referred in B 31.8

clause 833.11 (a) stand cancelled.

12.2 EXPANSION AND FLEXIBILITY (832)

12.2.1 B 31.8 Clause 832.1 stands cancelledand is replaced by the following:

"This section is applicable to both aboveground and buried piping and covers allclasses of materials permitted by thisstandard. Formal calculations shall berequired where reasonable doubt exists as tothe adequate flexibility of the piping".

Note : For the purpose of this standard,'unrestrained' means that the pipe isable to strain along its length, movelaterally, or both. Pipe that does notmeet both of the above requirementsis referred to as 'restrained'. Typically,long straight lengths of buried pipeand above ground pipe on closelyspaced rigid supports are classified asrestrained, whereas buried pipelinesadjacent to bends or unanchored endcaps could be regarded as restrained

or unrestrained, depending on specificcircumstances.

12.2.2 Following clauses are added to B 31.8Section 832 "EXPANSION ANDFLEXIBILITY"

12.2.2.1 Expansion calculations arenecessary for buried lines if significant temperature changes areexpected. Thermal expansion of buried lines may cause movement atpoints where the line terminates,changes in direction, or changes insize. Unless such movements arerestrained by suitable anchors, the

necessary flexibility shall beprovided.

12.2.2.2 Means of providing Flexibility

If expansion is not absorbed by

direct axial compression of the pipe,flexibility shall be provided by theuse of bends, loops, or offsets or provision shall be made to absorbthermal strains by expansion jointsor couplings of the slip joint, ball joint, or bellows type. If expansion joints are used, anchors or ties of sufficient strength and rigidity shallbe installed to provide for end forcesdue to fluid pressure and other causes.

12.3 COMBINED STRESSCALCULATIONS (833)

B 31.4 clauses 833.1, 833.2, 833.3, and 833.4stand cancelled and are replaced by thefollowing:

12.3.1 General

In addition to satisfying the requirements of clause 841 of B 31.4, it may be necessary tocalculate the longitudinal, axial, and bendingstresses, the torsional stresses, the hoopstresses, the stress interactions and thereactions at significant points in the system. Incalculating these stresses and reactions andthe effects of various loadings on the pipingthe designer shall use establishedfundamental analysis methods.

12.3.2 Loading Considerations

12.3.2.1 Consideration shall be given to thestresses and reactions caused by,but not necessarily limited to thefollowing loadings.

(a) Internal pressure;

(b) Thermal expansion and contraction;

(c) Differential support movements;

(d) Self-weight and gravity dead loads;

(e) Static wind loads and static fluid loads. ] 12.3.2.2 In addition to the requirements of

Clause 12.3.2.1 above, considerationshall be given, where applicable, to

the service conditions to which thepipe and support system are to be

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subjected. Consideration shall alsobe given to, but not necessarilylimited to the effects of the followingadditional loadings:

(a) Overburden loads;

(b) Live loads;

(c) Buoyancy;

(d) Dynamic and seismic loads;

(e) Cyclic and vibratory loads including theeffect of Stress Intensification. Factors onthe fatigue life of components);

(f) Internal pressure fluctuations;

(g) External hydrostatic pressure (includingcollapse, wave loadings and all significantfluid loads to which a submerged linemight be submitted);

(h) Geotechnical loads (including slides,differential settlement, loss of support,and thermal effect of the pipeline on soilproperties).

12.3.3 Stress Values

12.3.3.1 General:

There are fundamental differences in loadingconditions for the buried, or similarlyrestrained positions of the piping and theabove ground portions not subject tosubstantial axial restraint. Therefore, differentlimits on allowable longitudinal expansionstresses are necessary.

12.3.3.2 Restrained Lines:

The net longitudinal compressive stress dueto the combined effects of temperature riseand fluid pressure shall be computed from the

equation:SL = Ea (T2-T1) - v Sh

in which,

SL = The longitudinal compressive stress,psi(MPa)

Sh = Hoop stress due to internal fluid pressure,psi (MPa)

T1 = Temperature at time of installationdegrees F(degrees C)

T2 = Maximum or minimum operating

temperature degrees F(degrees C)

E = Modulus of Elastici ty of steel, psi (MPa)

a = Linear coefficient of thermal expansion,inch per inch per degree F (mm per mm

per degree C)

v = Poisson's ratio = 0.30 for steel

Note that the net longitudinal stress becomescompressive for moderate increases of T2 andthat according to the commonly usedmaximum shear theory of failure, thiscompressive stress adds directly to the hoopstress to increase the equivalent tensile stressavailable to cause yielding. This equivalenttensile stress shall not be allowed to exceed90 per cent of the specified minimum yield

strength of the pipe, calculated for nominalpipe wall thickness. Beam bending stressesshall be included in the longitudinal stress for those portions of the restrained line which aresupposed above ground.

12.3.3.3 Unrestrained Lines:

Stresses due to expansion for those portionson the piping without substantial axial restrainshall be combined in accordance with thefollowing equation:

SE = Sq. Root of (Sb2 + St

2 )

Where,

SE = Stress due to expansion.

Sb = Sq. Root of{ ( i1 M1)2 + ( i0 M0)

2}/Z

= equivalent bending stress, psi (MPa)

St = Mt/2Z = torsional stress, psi(MPa)

M1 = Bending moment in plane of member (for members having significant orientation,

such as elbows or tees, for the latter the moments in the header and branchportions are to be consideredseparately) in.lb. (N.m)

M0 = bending moment out of, or transverse,toplane of member, in lb. (N.m)

Mt = torsional moment, in lb. (N.m)

ii = stress intensification factor under bending in plane of member (B 31.8 Appendix E)

io = stress intensification factor under

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belonging out of, or transverse to,plane of member (B 31.8 Appendix E)

Z = section modulus of pipe, inch3(mm3)

The maximum computed expansion stress

range, SE without regard for fluid pressurestress, based on 100 per cent of theexpansion, with modulus of elasticity for thecold condition, shall not exceed 0.72 times thespecified minimum yield strength of the pipe.

The total of the following shall not exceedthe specified minimum yield strength, S.

a) the combined stress due to expansion, SE.

b) the longitudinal pressure stress.

c) the longitudinal bending stress due toexternal loads, such as weight of pipe andcontents, wind etc.

The sum of the longitudinal stresses due topressure, weight, and other sustained externalloadings shall not exceed 0.75 time theallowable stress in the hot condition (ref. B31.8 clause 841.11, (SXFXT)

The sum of the longitudinal stresses producedby pressure, live and dead loads, and thoseproduced by occasional loads, such as wind or earthquake, shall not exceed 80 per cent of thespecified minimum yield strength of the pipe.It is not necessary to consider wind andearthquake as occurring concurrently.

Stresses due to test conditions are not subjectto the above limitations. It is not necessary toconsider other occasional loads, such as windand earthquake, as occurring concurrentlywith the live, dead and test loads existing atthe time of test.

12.3.4 Following correction is made in B 31.8clause 833.5

R' = CsR when Cs is between 0.6 to 1.0

12.4 SUPPORTS AND ANCHORAGE FOREXPOSED PIPING (834)

Attachment of supports on Anchors (834.5)

The following sentence is added to B 31.8clause 834.5 (b)

Due consideration shall be given to theeffect of such attachments on possible fatigue

failures and local stress concentrations.

12.5 PRE-OPERATIONAL STRESSES(ADDITIONAL CLAUSE)

It is desirable to limit stresses during pre-operational manipulation of the pipe so as toavoid damage that might impair the operability

of the line. The designer shall ensure that pre-operational stresses are controlled and thatthey are non-injurious to the pipe.Consideration shall be given to, but notrestricted to, the effect of the following pre-operational loads:

a) Transportation and stockpiling of the pipe;

b) Stringing, coating and wrapping, andlaying.;

c) Backfilling;

d) Loads imparted by construction traffic;

e) Field bending;

f) hydrostatic test pressure loads(particularly when the pipeline isconstructed as an above grade installationor is buried in unstable soils).

13.0 DESIGN, INSTALLATION ANDTESTING (B 31.8 CHAPTER-IV)

13.1 GENERAL PROVISIONS (840.1)

The following clause is added to B 31.8 clause840.1 (a):

The selection of design for pipeline systemshall be based on the following evaluation of the properties and required flow rate of thefluid to be transported, together with theenvironment in which the pipeline is to beinstalled.

a) Sweet or sour natural gas, single or multiphase flow conditions, vapour phaseLPG.

b) Operating pressures and temperatures.

c) Gathering system, transmission system,distribution system, or service lines;

d) Onshore or offshore pipeline.

13.2 POPULATION DENSITY INDEX(840.2)

The following is added to B 31.8 Clause 840.2

(b) (4) Class 4 Locations.

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A Class 4 location ends 220 metre from thenearest building with 4 or more stories aboveground.

13.3 STEEL PIPE DESIGN FORMULA(841.11)

The following is added to B 31.8 clause841.11:

Corrosion Allowance:

A corrosion allowance on the design wallthickness need not be made unless internal or external corrosion is expected, nor is anallowance required where a corrosive fluid isto be transported or soil conditions areconducive to corrosion, or both provided thepipe and components are protected against

corrosion in accordance with the requirementsand procedures prescribed in Chapter VI of B31.8

Where there is a possibility of internalcorrosion taking place, a corrosion allowanceshould be made. Such corrosion allowanceshall provide that the increase in wallthickness is additional to the wall thicknessrequirement for pressure. The allowanceshould be based upon a specialistinvestigation of the corrosive process involvedand will also be influenced by the required lifein the pipeline.

13.4 COVER REQUIREMENTS FORPIPELINES (841.142)

Table for cover requirement for pipeline in B31.8 Clause 841.142 stands cancelled and isreplaced by the following:-------------------------------------------------------------Location Minimum cover in

meter -------------------------------------------------------------Industrial, Commercial and 1.0 (2)Residential Areas

Drainage ditch, Canal, Nala, 1.5small, rivers and other minor water crossings

Drainage ditches at roadways 1.0& railroads

Rocky areas 1.0 (2)Uncased/Cased road crossings 1.2 (3)Railroad crossings 1.4 (3)Other areas 1.0 (2)

(1) The above mentioned minimum cover requirements shall be valid for all class

locations.

(2) Minimum depth of cover shall bemeasured from the top of pipe coating tothe top of undisturbed surface of the soil,or top of graded working strip, whichever

is lower. Fill material in working strip shallnot be considered to add to the depth of cover.

(3) Cover shall be measured from the top of road or top of rail, as the case may be.

(4) In case of rivers/water bodies, which areprone to scour and erosion, adequate safecover (minimum 1.5 metre) shall beprovided below the predicted scour profileexpected during the life time of thepipeline.

13.5 CLEARANCE BETWEEN PIPELINESOR MAINS AND OTHERUNDERGROUND STRUCTURES(841.143)

Following clauses are added to B 31.8 clause841.143

13.5.1 In laying parallel pipelines in the sametrench, the minimum clear distancesbetween the pipelines shall be 500mm.

13.5.2 The location of a new undergroundpipeline, when running parallel to anexisting underground pipeline shouldbe at a minimum clear distance of 5.0metre from the existing undergroundpipeline when heavy conventionalconstruction equipment is expected tobe utilized. This distance may bereduced after a careful assessment of construction methodologies, which donot result in unsafe conditions duringconstruction. In any case theminimum clear distance shall not be

less than 3.0 meter. These areas shallbe distinctly identified on groundduring construction.

No pipeline should be located within15.0 metre of any private dwelling, or any industrial building or a place of public assembly in which personswork, congregate or assemble, unlessit is provided with atleast 300 mm of cover in addition to that provided inclause 13.4 of this standard.

13.6 CASING, REQUIREMENTS UNDERRAILROADS, HIGHWAYS, ROADS,

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OR STREETS (841.144)

Following is added to B 31.8 Clause 841.144:

Pipeline, casing pipe and vent pipesshall be at least 1.2 metre away (vertically)

from aerial electrical wires and shall besuitably insulated from underground conduitscarrying electric wires on railway land.

13.7 FOLLOWING IS ADDED TO B 31.8CLAUSE 841.15:

Design and construction of gas pipelinescrossing Railroads, Highways, Roads or Streets shall be done in accordance with theprovisions of "Recommended Practice for Liquid Petroleum Pipelines Crossing Railroadsand Highways" API RP 1102 and applicable

clauses of B31.8 and this standard.

13.8 BENDS, ELBOWS AND MITERS INSTEEL PIPELINES AND MAINS(841.23)

13.8.1 B 31.8 Clause 841.231 (b) and841.231(c) are canceled and replaced by thefollowing :

The minimum radius of field cold bends shallbe as follows:

_____________________________________ Normal Pipe Size Minimum Radius of

in Bending in PipeDiameters

_____________________________________ NPS 12 and smaller 21 DNPS 14 u/i 18 30 DNPS 20 and larger 40 D _____________________________________

13.8.2 Following clauses are added to B31.8 clause 841.231.

13.8.2.1The ends of each bent length shall bestraight and not involved anyway inthe bending. The length of thestraight section shall permit easy jointing. Tangents approximately 1metre in length shall be provided onboth ends of cold bends. A fieldbend shall not be made within twopipe diameters of a field weld, whichhas already been made. Tangentlengths should not be reduced in thefield.

13.8.2.2 Pipes with longitudinal welds shall be

bent in such a way lies in the planepassing through neutral axis of thebend which shall be installedpositioning the longitudinal weld inthe upper quadrants.

13.8.3 B 31.8 Clause 841.232 is cancelledand replaced by the following:

A mitered bend is not permitted withthe exception of deflections upto 3degrees that are caused bymisalignment.

13.8.4 The following sentence is added to B31.8 Clause 841.233.

Field-cut segments of elbows NPS 12"and larger are not recommended.

13.9 MISCELLANEOUS OPERATIONSINVOLVED IN THE INSTALLATIONOF STEEL PIPELINES AND MAINS(841.25)

13.9.1 Handling, Hauling, and Stringing(841.251)


Pipe shall not be strung on the Right-of-Wayin rocky areas where blasting may be required,until all blasting is complete and the areacleared of all debris. Material other than linepipe shall not be strung on the Right-of-waybut shall be transported to site for use only atthe time of installation.

13.9.2 Installation of Pipe in the Ditch(841.252)


Pipelines shall be buried below ground level,unless construction above ground is found to

be desirable for exceptional technical,economic or topographical reasons.

Before lowering operations are commenced,particular attention shall be paid to thesuitability of the trench to allow the pipeline tobe lowered without the coating being damagedand to give a reasonably even support to thepipeline.

When already coated pipes are beinglowered, a complete check of the pipe coatingand field joint coating shall be carried out and

all damages repaired.

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Wherever pipeline is laid under tension as aresult of an assembly error (for example,incorrect positioning of bends, either horizontal or vertical), the trench shall berectified or in exceptional cases a newassembly shall be carried out so that it fits the

excavation and the laying bed.

Care must be taken that the deformationcaused during the raising of the pipe from thesupports does not exceed the valves for theminimum allowable radius of elastic curvature,so as to keep the stresses on the steel pipeand on the coating within safe limits.

The width of trench shall be such that aminimum clear distance of 200mm for trenchin normal soil and 300mm for trench in rock ismaintained between edge of pipe and the

trench wall at the bottom of trench.

13.10 WATER CROSSINGS (ADDITIONALCLAUSE)

Special considerations shall be required for submerged crossing by pipelines of riverswhich are characterized by their perennialnature, meandering course, steep andpotentially erodable banks, potentiallyscouring bed, large erodable flood plain andwide water course (high water mark to highwater mark) both during the design andinstallation of such crossings:

For river crossings such as those describedand established as above, the followingrequirements are to be considered:

(a) Hydrological and geotechnical surveysto establish the river bed and water current profi les, to predict thebehaviour of the river with respect tochange of course, scour of bed anderosion of banks and to obtain allother parameters related to designand installation of such crossings.

(b) The pipeline at such crossings shallbe installed with extra depth of cover.The cover provided shall be adequateto prevent exposure of the pipeline for the entire design life of the pipeline.

(c) To ensure the stability of theunderwater pipeline, it may benecessary to add weight to sink andhold the pipeline in position.

(d) A heavier wall thickness pipe shall be

provided for a river crossing section.

(e) A detailed stress analysis for the pipesection for river crossings should benecessary taking into considerationthe effect of all loads during laying andit shall be ensured that the stressesremain within permissible limits in

accordance with B 31.8 and thisstandard.

(f) Whenever considered desirable, thesection of the pipeline correspondingto the river crossing should, beforeinstallation, be subjected tohydrostatic pretesting. However, thecomplete pipeline corresponding toriver crossing shall be tested after installation.

13.11 CROSSING OF OR BY UTILITIES

(ADDITIONAL CLAUSE)

13.11.1 A minimum clearance of 300mm shallbe maintained at the point of crossingand the utility or pipeline shall beinstalled at a uniform depth for the fullwidth of the right-of-way, providedthat, where it is not practicable toobtain the above mentionedclearance, special design andconstruction shall be used.

13.11.2 A clearance sufficiently large to avoidelectrical fault current interferenceshall be maintained between thepipeline and the grounding facilities of electrical transmission lines.

13.11.3 Interference with, or from, other systems through the application of Cathodic Protection shall be dealt withby mutual action of the partiesinvolved.

13.11.4 When laid parallel to along or near underground power and/or communication cables, conductors, or conduit, underground pipes shall,

maintain a horizontal clearancebetween vertical planes through theadjacent external surfaces of thepipelines and cables, conductors, or conduit, or structures, of theunderground utility, of at least 300mm.Where these clearances cannot bemaintained, extra precaution shall betaken to ensure the maximum possibleclearance and to prevent futurecontact. If pipelines andcommunication and/or power utilitiesshare the same trench the above

horizontal clearance shall bemaintained with the pipeline preferably

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at a lower level.

13.11.5 A minimum separation of 3.0 metreshould be maintained betweenpipeline and transmission tower footings, ground cables and counter

poise. Regardless of separationconsideration should always be givento lightning fault current protection of pipelines and safety of personnel.

13.11 6 All crossings shall be made in such amanner that the angle between thecenterline of the railway, highway,river, stream, canal or utility beingcrossed and the centreline of thepipeline shall be as close as possibleto 90 deg. but in no case less than 45deg.

13.12 TESTING AFTER CONSTRUCTION(841.3)

13.12.1 General Provisions (841.31)

B 31.8 Clause 841.31 stands modified asfollows:

a) All Pipelines, mains, and service linesshall be tested in place after construction, except as provided for in(b) below.

b) Tie-ins

For pipelines intended to operate athoop stresses of 30% or more of thespecified minimum yield strengthpretested pipe shall be used in tie-insections and for those sections wherein-place testing is not practicable.

13.12.2 Test Required to Prove Strength of Pipelines and Mains to Operate atHoop Stresses of 30% or More of theSpecified Minimum Yield Strength of

the Pipe (841.32)

13.12.2.1 The following paragraphs are addedto B 31.8 Clause 841.321

All test assemblies used in testing shall befabricated and installed in accordance withprovisions of B 31.8 covering permanentassemblies and fabrications.

For all buried and submerged piping, the testpressure shall be maintained for a period of 24hours after temperature stabilization and

stabilization of surges from pressurizingoperations. The test pressure for above

ground piping and offshore platform pipingshall be maintained for a minimum period of 4hours, during which time the piping shall beinspected for leaks.

All sections, which have been previously

hydrostatically tested viz. road/rail crossingsand river crossings, shall be retested alongwith the completed mainline sections.

A guaging pig shall be passed through thepipeline to prove the internal diameter of theentire line, the guaging plate having adiameter of 95% of the internal diameter of thepipeline.

When water is used as the test medium,inhibited water, i.e. water to which suitabledoses of corrosion inhibitors are added

depending upon quality of water, shall beused.

13.12.2.2 B 31.8 Clause 841.322 (a) and814.322 (b) stand cancelled andare replaced by the following:

Pipelines and mains located in class 1 andclass 2 location shall be tested with air, gas or water to at least 1.25 times the maximumoperating pressure. Testing, wherever practicable, shall be by means of water rather than a gaseous medium. Where a gaseousmedium is used, the test pressure shall notexceed 1.25 times the maximum operatingpressure. Sour gas shall not be used as a testmedium.

13.12.2.3 Following is added to B 31.8 clause841.322 (c):

Compressor station, regulator station andmeasuring station gas piping, including thepiping connecting the station to valvingemployed for isolating the station from thepipeline and designed in accordance withType-C construction (Design factor = 0.5) shall

be tested to atleast class 3 location testrequirements.

13.12.2.4 Following is added to B 31.8 clause841.322 (d):

Where testing of offshore platform gas pipingand pipe riser cannot be accomplishedseparately from the main offshore pipeline, thepiping components shall be pretested toatleast 1.4 times the maximum operatingpressure, provided that all final welds areinspected in accordance with the provisions of

B 31.8 and all such piping is retested with themain offshore pipeline to class 1 location test

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requirements.

13.12.2.5 B 31.8 Table 841.322 (e) 'TestRequirements for Pipelines andMains to Operate at HoopStresses of 30% or More of the

Specified Minimum YieldStrength of the Pipe' standscancelled and is replaced by Table13.12.2.5 of this standard.

GENERAL NOTES:

mop = Maximum operating pressure (notnecessarily the maximum allowable

operating pressure)dp = design pressuretp = test pressure

This table brings out the relationship betweentest pressures and maximum allowableoperating pressures subsequent to the test. If an operating company decides that themaximum operating pressure will be less thanthe design pressure, a correspondingreduction in prescribed test pressure may bemade as indicated in the pressure Test

Prescribed, Minimum, column. However, if this reduced test pressure is used, theMaximum operating pressure cannot later beraised to design pressure without retesting theline to the test pressure prescribed in thePressure Test Prescribed. Maximum, column.See B 31.8 clause 805.214, 845.213 and845.214.

NOTE:

(1) For exceptions, see B 31.8 clause 841.322

(d)

(2) For definition of terms S, D, t, E and see B

31.8 clause 841.11 (a).

13.12.2.6 B 31.8 Clause 841.323 (c) iscancelled and is replaced by thefollowing:

In such cases an air test to 1.25 times themaximum operating pressure shall be madeand the limitations on operating pressureimposed by Table 13.12.2.5 of this standard donot apply.

13.12.2.7 Records (841.327)

B 31.8 Clause 841.327 is cancelled and isreplaced by the following:

The operating company shall maintain in its

file for the useful life of each pipeline and main,records showing the procedures used and thedata developed in establishing its maximumallowable operating pressure.

The record shall contain at least thefollowing information:

(a) Time and data of Test;

(b) Pipe Specifications of sections under test; (c) Elevation profile and the location of the

test section and testing points, if applicable;

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to resist damage due to normalhandling (including concrete coatingapplication, or river weightinstallation, where applicable) and soilstress;

e) Be compatible with cathodic protectionsystem.

15.2 ELECTRICAL ISOLATION (862.114)

The following clauses are added:

a) This clause shall not take precedence over recognized electrical safety practices andcodes.

b) Where insulating devices are installed toprovide electrical isolation of pipelinesystems to facilitate the application of

corrosion control, they shall be properlyrated for temperature, pressure, andelectrical properties, and shall be resistantto the commodities carried in the pipelinesystems. These devices shall not beinstalled in enclosed areas wherecombustible atmospheres are likely to bepresent unless precautions are taken toprevent arcing. (After refer Clause 15.4 of this standard)

c) Pipeline system shall be installed so thatthe belowgrade or submerged portions arenot in electrical contact with any casing,foreign piping systems or other metallicstructures. This shall not preclude the useof electrical bonds where necessary.

d) Provision shall be made to preventharmful galvanic action at below-grade or submerged connections between copper and steel piping.

Consideration should be given to:i) Installing an insulated coupling or

insulating gasket set between the copper and steel, or

ii) Protecting the piping with an insulatingcoating material to provide a spatialseparation of not less than 0.5m betweenbare copper and steel.

15.3 ELECTRICAL CONNECTIONS ANDMONITORING POINTS (862.115)

15.3.1 The following paragraph is added to B31.8 Clause 862.115 (b)(1):

Where a higher current carrying capacity is

required, a multistrand conductor shall beused and the strands shall be arranged into

groups no larger than No.6 AWG. Each groupshall be attached to pipe with a separatecharge. Attaching test leads directly to thepipe by other methods of brazing is prohibited.15.3.2 The following paragraph is added:

When a thermit welding process is used for electrical lead installation on pressurizedpipelines, precautions shall be taken to avoidpossible failure of the pipeline duringinstallation due to loss of material strength atthe elevated welding temperatures. Where athermit welding process is not deemedsuitable. Consideration shall be given to other methods of installation.

15.4 ELECTRICAL INTERFERENCE(862.116)

Following is added to B 31.8 Clause 862.116Electrical Interference-Alternating Current andLighting.

15.4.1 Fault Current Interference

Fault current interference shall be taken intoconsideration.

NOTES:

a) Fault current resulting from lighting or upset conditions of electrical facilitiescould result in serious damage tocoating and pipe wall and danger topersonnel. These adverse effects mayoccur where a pipeline is close to thegrounding facilities of electricaltransmission line structures, sub-stations, generating stations or other facilities that have high short circuitcurrent-carrying grounding networks.

b) Where a buried pipeline system is closeto grounding facilities, remedialmeasures may be necessary to controlthe effect of these fault currents in order

to reduce the resultant rise in potentialgradient in the earth near the pipelinesystem to an acceptable level.

15.4.2 Induced Potential Interference

Pipelines paralleling alternating currentelectrical transmission lines are subject toinduced potentials as well as the effectsmentioned in Notes to Clause 15.4.1 above.

a) When studies or tests show thatalternating current potentials will be or

are being induced on a buried pipelinesystem, devices shall be installed to

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reduce these potentials to a tolerablelevel.

b) When such pipelines are under construction, or when personnel are incontact with the pipelines, special

precautions shall be taken to nullify thepossible effects of induced alternatingcurrent potentials.

15.4.3 Safety Requirements

Following precautions shall be taken:

a) Employ blowdown connections that willdirect the gas away from the electricconductors;

b) Install bonding across points where the

pipeline is to be separated and maintainthis connection while the pipeline isseparated;

c) Make a study in collaboration with theelectric company on the commonproblems of personnel safety, corrosion,electrical interference and lightingproblems.

15.5 EXISTING INSTALLATIONS (862.2)

The following clauses are added:

15.5.1 Existing Coated Pipeline Systems

Cathodic Protection shall be applied andmaintained on all existing coated pipelinesystems.

15.5.2 Existing Bare Pipeline Systems.

Investigations shall be made to determinethe extent or effect of corrosion on existingbare pipeline systems. Where theseinvestigations indicate that continuingcorrosion will create a hazard, corrosion

control measures or other remedial actionshall be undertaken.

15.5.3 Cathodically Protected PipelineSystems Temporarily out of Service

Cathodic Protection systems shall bemaintained on any pipeline system temporarilyout of service.

15.6 TEMPORARY CATHODICPROTECTION SYSTEM(ADDITIONAL CLAUSE)

When considered necessary, a temporary

Cathodic Protection system with sacrificialanodes shall be installed to ensure adequateprotection of pipeline from external corrosionfrom the time the pipeline is laid in the trenchtill the permanent Cathodic Protection systemis commissioned.

The temporary cathodic protection systemshall preferably be installed simultaneouslykeeping pace with the pipelinelaying/installation work and shall be monitoredperiodically.

15.7 INTERNAL CORROSION CONTROL(863) General (863.1)

B 31.8 Clause 863.1 is deleted and is replaced

by the following:

15.7.1 Any gas whose water dew point is at alltimes below the minimum pipelineoperating temperature is considered tobe non-corrosive, unless tests or experience indicate otherwise.

15.7.2 Any gas whose water dew pointexceeds the minimum pipelineoperating temperature is considered tobe corrosive, unless tests or experience indicate otherwise.

15.7.3 Any gas containing hydrogen sulphideor carbon dioxide whose water dewpoint exceeds the minimum pipelineoperating temperature is considered tobe corrosive, unless tests or experience indicate otherwise.

15.7.4 Any gas containing hydroten sulphideor carbon dioxide whose water dewpoint is maintained below theminimum pipeline operatingtemperature by dehydration, or issuitably inhibited, is considered to be

non-corrosive, unless tests or experience indicate otherwise.

16.0 MISCELLANEOUS (B31.8CHAPTER-VII)

All provisions of B 31.8 Chapter VII shall apply.

ANSI B 31.8 APPENDIX-C

List of numbers and subjects of thosestandards and specifications which do not

appear in the text of B 31.8 but may be of informational benefit.

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Following is added to B 31.8 Appendix-C

DIN30670 Polyethylene Sheathing of Steel Tubes

and of Steel Shapes and Fittings.

30672 Corrosion Protection Tapes and HeatShrinkable Sleeves-Coatings madefrom Corrosion Protection Taps andHeat Shrinkable Sleeves for Underground Pipelines.

BSIBS-4146Specifications for Coal-Tar BasedHot1987

Applied Coating Materials for protectingIron and Steel, including suitable

Primers where required.

AWWAC203-86 Standard for Coal-Tar Protective

Coatings and Linings for Steel Water Pipelines-Enamel and Tape-Hot

Applied.

TM-02-84 Testing of Metals for Resistance toStepwise Cracking.

Name and address of the organisation whose

standards and specifications appear above:

DIN Deutsches Institute fur NormungObtainable from:Foreign Standards DistributionBurggrafen Strasse 4-10,D-1000BERLIN 30

BSI British Standards Institution2, Park Street,London: WIA 2BSTelephone : 01-6299000Telex : 266933

AWWA American Water Works Association6666,West Quincy Avenue,Denver, Colorado 80235.

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