Raufeek M H, et al., International Journal on Occupational Health & Safety, Fire &Environment – Allied Science ISSN 2349-977X

Page 1 of 8Int J OSHFE-Allied Sci./Article. 1/Vol.1/Issue 1/Jan-Dec, 2018

INTRODUCTIONHistorically, India has relied on

coal to power its electricity sector,liquid fuels as feed stock and oil forits transport sector. But forenvironmental reasons we need to focuson cleaner fuels. Gas is one of thecleanest fuels with less carbon dioxideper joule delivered than either by coalor oil and far fewer pollutants thanother hydrocarbon fuels.

Natural Gas, is a new age fuel is thecleanest, efficient, non-polluting,environmental friendly and relatively

economical of the fossil fuels in themodern day industrial society. NaturalGas Pipeline Infrastructure connectsvarious gas sources to different gasmarkets to the meet the existing/ futurenatural gas demand of various Powers,Fertilizer, CGD and other industries inthe Country.

A big challenge lies in bridging thephysical gap between demand and supplycenters in an efficient, safe and eco-friendly manner. Pipelinetransportation of gas offers a safe,economic and environmentally sound

Review Paper

SAFETY OF NATURAL GAS CROSS COUNTRY PIPELINENETWORKS, IN INDIAN CONTEXT

Raufeek MH1, Dr. Nihal Anwar Siddiqui1

Address for Correspondence

1Department of Health and Safety & Environment, University of Petroleum and Energy

Studies, Dehradun, India.

ABSTRACTCan Natural gas industry meet increasing customer needs? This question is verycommon these days amongst many Natural Gas customers and Natural Gas industryexecutives all over the country. Today Indian customer wants to know if there wouldbe enough natural gas with an adequate transportation and distribution system tomeet the growing needs of clean fuel.

When hazardous materials like Gaseous Hydrocarbon / Natural gas are transferredthrough pipelines, they pose severe hazard problems for human beings and propertyin vicinity. In view of this safeguard for pipelines are essential and one ofimportant needs to be considered during designing, operating and maintaining apiping system. Initiating and contributing Hazards associated with pipelinecarrying Hydrocarbons like Natural Gas can be mainly human errors, equipmentfailure, system or procedure failure, external reason and the Consequences ofvarious hazards are gas leakage, fires, Health Hazard etc.Operating the Cross Country Natural Gas pipeline system at high pressure, passingthrough thickly populated area, lack of public awareness, ongoing constructionactivities etc. poses significant hazard in Indian context on Safest Method ofTransportation.Hence, it is important to established robust mechanism for safe operation andmaintenance of cross country pipeline in India. This includes: Health, Safety &Environment Management System; Awareness; Pipeline Maintenance and FireProtection Systems.

The integrity of Natural Gas Pipeline System comes through the continuous effortsin all stages to ensure that pipeline is designed, commissioned, operates andmaintained as per stipulated codes and standards. Further, technological up-gradation in operation, inspection and maintenance enhance the safety of pipelinesystem and increase the safety at a greater extend.

Keywords: Safety of Natural Gas, Hydro Carbons.

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Raufeek M H, et al., International Journal on Occupational Health & Safety, Fire & Environment – Allied Science ISSN 2349-977X

alternative to most other modes ofenergy transport.

NEED OF A LARGE NETWORK OF CROSSCOUNTRY PIPELINE IN INDIA

FIGURE: Demand Supply Balance of NaturalGas From 2012-13 to 2029-30

TABEL: List of Natural Gas Pipelines inIndia.

It is perceived that by 2017 India willhave a natural gas pipeline grid of30,000 km connecting consumptioncenters to source of fuel. A Natural Gaspipeline system may contain followingelement:

♣ Buried Pipelines♣ Above Ground Pipelines♣ Compressor Stations

♣ Isolation Valves – Manually,Remotely or Automaticallyactivated

♣ Relief Valves – Pressure or Thermal♣ Pipe Bridges or other Supports♣ Casing Sleeves under Road/Rail

Crossing♣ Leak Detection System♣ Pig Launchers/Receivers♣ Control Systems

FIGURE: Natural Gas Pipeline Network

HAZARDS ASSOCIATED WITH NATURALGAS CROSS-COUNTRY PIPELINESWhen highly flammable hydrocarbons likenatural gas are transferred throughpipelines, they pose severe hazardproblems for human beings and propertyin vicinity. In view of this safeguardfor pipelines are essential and one ofimportant needs to be considered duringdesigning, operating and maintaining apiping system. Initiating andcontributing Hazards associated withpipeline carrying Hydrocarbons likeNatural Gas can be mainly following:-

Human Errors: during Pigging operation,hot tapping, Slug Operation, repair/replacement of the sections, Valve

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Raufeek M H, et al., International Journal on Occupational Health & Safety, Fire & Environment – Allied Science ISSN 2349-977X

operation etc.

Equipment Failure: Due to ThermalExpansion, Internal corrosion, Externalcorrosion, Fatigue, CP Failure, Failureof Support, Failure of gaskets, etc.

System or procedure Failure:Inspection, operation, Shutdown,Startup, Leak detection, Temporaryrepairs, Material specification andtesting, etc.

External Reason: Accidental Excavation,Earthquake, Flood, Fire, Lightning,Rail / road accident, etc.

CONSEQUENCES OF VARIOUS HAZARDSThe consequence of failures of gaspipelines are of following types:

Gas leakage: In gas pipelines, gas willcontinue to release from the pipe leak.Sometimes, the high compressibilitynature of gas results in a high level ofenergy remaining in the vicinity ofpuncture for a sufficient time to allowsmall holes to propagate to full borerupture. However, in volatile liquidspipelines, say for LPG where material isconveyed as liquid under pressure, theloss of pressure due to rupture orleakage will flash the fluid to a mixtureof vapour and liquid.

The slugs of liquid and gas arealternatively released producing aheavier than air flammable vapour cloud.Finally, all the liquid is evaporatedand a simple gas release takes place.

Fires:

a) Jet fire: Generally gas inside pipeis at a very high pressure. In case itcomes out into atmosphere it will be inthe form of a jet. There is everylikelihood that it will immediatelycatch fire either through some externalheat source or through its own hightemperature (if it has already beenexposed and temperature has risen aboveits auto ignition temperature) and eventhrough static electricity, which mightgenerate due to high velocity at the tipof the rupture opening. Severity of thistype of incident depends upon diameterof pipeline, pressure inside, size ofrupture etc. Jet fire has potential to

cause harm in following two ways:

✯ Cutting anything coming in its way andhence it may have domino effect.

✯ Adjoining area may get exposed andhence they may get their temperaturerisen at a very high pace.

b) Fire Ball: Fire ball scenario isbecause of immediate ignition ofreleased gas. Thermal radiation fromfireball is intense. The casualties fromthe fireball will depend on the thermaldose experienced by surroundingpersons.

c) Delayed ignition: Gas release andfire hazards on immediate ignition areoften considered as the safest scenariofor flammable chemicals since theflammable material gets consumed in thisprocess. Delayed ignition can occur incase the released gas is not immediatelyignited but finds an ignition sourceafter the gas has dispersed and itsconcentration is still in flammablerange. Methane is lighter than air andhence will disperse more rapidly in openterrain on release and hence delayedignition for methane can only result inflash fire with no overpressure wave.

d) Unconfined/ Confined vapor cloudexplosion: On the other hand LPG, whichis heavier than air due to presence ofheavier fractions like Propane andButane, may not disperse so easily, Dueto terrain conditions if there ispossibility of these gases gettingaccumulated or confined, on release frompipeline, there may be unconfined/confined vapour cloud explosion, if asource of ignition is also available.

HEALTH HAZARD

a) Asphyxiation: Due to release of highvolume of these gases into atmosphere,the concentration of oxygen may go downto unsafe level, i.e. below 19.5 %. Inthis atmosphere a person may fallunconscious or even die. The same is truefor other fauna and animals that may comein contact of such atmosphere especiallyin country side.

b) Frost bite: In case temperature of

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Raufeek M H, et al., International Journal on Occupational Health & Safety, Fire & Environment – Allied Science ISSN 2349-977X

released gas is sub zero, there islikelihood of frost bite/ cold burn toliving beings coming into contact.

SOURCES OF IGNITION

The minimum ignition energy for pureMethane at atmospheric pressure is 0.29mJ, which is very low when compared tostatic discharge of 22 mJ (on walking)or Ordinary spark plug discharge of 25mJ, hence ignition can occur at any timeduring the gas release. (Source: Crowl& Louvar, 1990).

Various sources of ignitions can be:

1. Electrical Spark: From Switches,lamps, motors, lamp boards, panelsetc.

2. Friction: Vibrations of pipelines, hot bearings, brokenmachine parts, etc.

3. Open flames: From Cutting andwelding torches gas burner, etc.

4. Using match sticks, SmokingCigarettes etc.

5. Hammering, scraping, digging, roadcutting, etc.

6. Hot surfaces

7. Static electricity.

8. Lightening.

MITIGATIONS OF HAZARDS -PRECAUTIONARY MEASURES

Protection against External Corrosion –Cathodic Protection: To protectcorrosion external coating should beused on the pipelines. Cathodicprotection systems are designed toreduce the likelihood of externalcorrosion. In this system electricalpotential difference are set up betweenthe pipe and surrounding earth toprevent the formation of corrosion cellswhere the pipe external coating hadfailed locally.

Protection against Internal Corrosion –Chemical Inhibitors: Internal corrosionis a function of the contain and conveysof pipeline. Its mitigation can be done

by injecting chemical inhibitors alongwith the product flow. However,selection of inhibitor type is verycritical so that it will not changeactual fluid properties or create unsafeconditions. Another method of safetyagainst internal corrosion is to providelining on the inner wall of pipeline withan inert protection material compatiblewith the fluid transported.

Protection against third party damage:This type of failure occurs because ofunawareness of third party about thepresence of pipelines. This type ofdamages can be reduced by ensuring theproper awareness amongst the public,landowners and state authorities.Pipelines crossing other utilities liketelephone, electrical cables, water/sewer mains etc nearby are more prone fordamage, they should be duly providedwith markers / pipeline indicators.

Protection for pipe supports:Appropriate usage of piping supports andexpansion joints is very important inany piping system. These piping supportsshould be designed to take care selfweight plus the transported fluid weightplus insulation and also to ensure theflexibility provided to take care of thethermal expansion of pipes.

Leak Detection system: the most basicmethod involves either walking, drivingthe pipe line right of the way, to lookfor evidence of discoloration ofvegetation near the line or hear or seethe leak. There are methods of leakdetection in case of non-flammableproducts, i.e. addition of odorant tothe fluid and detection of the leak bysmell. This can also be done by checkingthe gross in-balance over hourly ordaily basis, by line flow mass balanceor by monitoring through a leakdetection device, etc. Infrareddetector are being used for finding outthe leaks from pipelines, Leak Apps arebeing used by various industries.

Pig Based Monitoring System: Pigs arefrequently used for pipelinecommission-ing, cleaning, filling, de-waxing in general. But now a days“intelligent pigs” are available thattravels internally along the pipeline

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Raufeek M H, et al., International Journal on Occupational Health & Safety, Fire & Environment – Allied Science ISSN 2349-977X

and measures the conditions of the pipewalls. These pigs are designed to carryspecial monitoring equipment for thepurpose.

Protection against Overpressures: Overpressurization relief devices must beprovided to piping system in order toprevent pipeline failure because ofover-pressurisation. Installation ofPressure relief valves (PRVs) can beused as protection against overpressure.

Protection against Detonation Hazards:Flame arrestors are essential safetydevices that stop the propagation of asubsonic flame front and cool the flamein order to sustain the combustion.Inline detonation arrestors are similartype of devices designed to preventexplosion in a piping system bydetonation hazards.

SCADA SYSTEM - SAFE WAY OF PIPELINEOPERATION AND LEAK DETECTION SYSTEM

Supervisory control and dataacquisition (SCADA) system is anextension of the instrumentationcontrol system. The SCADA systemconsists of the following basic sub –systems.

1. SCADA Master Control Station(SMCS)

2. Remote Terminal Units (RTU)3. Communications Link

SCADA Based Leak Detection System:

The SCADA package may include a leakdetection system (LDS). LDS may behardware based or software based. In atypical hardware based LDS, transducersare installed at regular intervals onthe pipeline. Negative pressure wavesgenerated during a leak are picked up bythe transducers on either side of theleak location and on the basis of arrivaltime of signals, the leak location isdetermined. The LDS can also determinethe size of the leak. Software based LDStakes flow, pressure, temperature,density, pipe characteristics etc. asinputs. The variation in flow andpressure are regularly computed and are

compared with leak models alreadysimulated and stored in the computer.Voting mechanisms are developed in orderto minimize false leak alarms. Thehardware based LDS can offer accuracy(leak location and leak detection time)better then software based LDS. However,if there is a communication break at thetime of leak occurrence, the hardwarebased LDS is likely to miss the leakaltogether.

PIPELINE EMEGENCY HANDLING

Proper Emergency action plan makes thehandling of pipeline emergency easierand situations can be handled in lesstime and with minimum losses.

In case of Gas leakage:

In case of gas leakage following actionsmust be taken immediately:

a. Control consists of directing,diluting & dispensing the gas toprevent contact with persons,preventing it from infiltratinginto structures if release isoutdoors, and avoiding its contactwith ignition sources, while ifpossible, simultaneously stoppingthe flow of escaping gas.

b. Air, steam & water have proven to bebest for this purpose.

In case of Fire:

Don'ts

✯ Do not extinguish fire immediately.✯ Do not close valve immediately.

Do's (in sequence)

✯ Try to minimize radiation and locatefuel supply valve simultaneously.

✯Keep DCP Ext. ready near fire & closevalve 95%.

✯ Extinguish Fire.✯ Close remaining 5% of valve.

Control of Fire emergency is generallythe control of heat from the fire by theapplication of water & if possible, bystopping the flow of escaping gas.

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Raufeek M H, et al., International Journal on Occupational Health & Safety, Fire & Environment – Allied Science ISSN 2349-977X

SAFETY FEATURES OF PIPELINE

Design and Construction:

1. Sizing of line pipe wall thicknessaccording to the populationdensity of the area, designpressure, specified minimum yieldstrength, diameter of pipelongitudinal joint factor andtemperature derating factor, asper ANSI/ASME b 31.8.

2. Additional corrosion allowance of2 mm of design wall thicknessconsidering 30 years pipelinedesign life and moderate corrosionrate.

3. Providing minimum ground cover of1m for the buried pipelineirrespective of pipeline diameterwhich is more than specified depthas per ASME b-31.8.

4. Line pipes are having 3 layerpolyethylene external coatinginstead of conventional coat-tarcoating.

5. Specifying and adhering toqualification of the welders andwelding processes for enhancingpipeline safety.

6. 100% radiographic inspection ofwelded joints using x-rays andgamma rays. Destructive &ultrasonic testing for selectedjoints for ensuring quality work.

7. The total length of pipeline andits installations werehydrostatically tested at apressure of 1.4 times of designpressure i.e., 128.8kg/cm2.

8. Installation of remotely operatedsectionalizing valves (sv) atregular intervals of approx. 30-35kms..

9. Sectionalizing valves installedacross major river. Averagedistance between two valvesapprox. 20 kms.

10. Pressure safety valves at theintermediate pigging (ip)stations.

11. Installation of casing pipes atall railway crossings and highwaycrossings as per internationalstandards.

12. Anti-buoyancy measures byproviding saddle weight or

continuous concreting for thepipeline sections which arepassing through minor and majorwater crossing.

13. Bank protections for canals /minor river crossings by providingmattresses / cabions.

14. Lying of pipeline at a depth of4-5 mtrs. Below the secure level atmajor river crossings byhorizontal directional drillingmethod (HDD).

15. Pipeline markers like warningboards, kilometer / aerial, r.o.u.boundary pillars etc.

16. Fire detection & CO2 floodingsystem at all radio repeaterstations.

17. Corrosion sensing probes (CSP)for monitoring external corrosionrate at every 10 kms.

18. Computerized test stations (CTS)at vulnerable locations whereround the clock monitoring of pipeto soil potential is required.

19. Temporary C.P. till permanentC.P. system installed forprotecting the pipeline againstcorrosion.

Operation & maintenance:

1. Supervising the operation ofentire pipeline round the clockfrom MICC and regular healthmonitoring through SCADA.

2. Monthly helicopter surveillanceof the entire pipeline route forpossible encroachment in rou, soilerosion etc.

3. Monitoring the pressure profileof pipeline. In case of suddenpressure drop 0 0.5 kg/cm2 perpolling cycle due to any leak /burst in pipeline, MCC willreceive alarm.

4. Half yearly monitoring ofcorrosion sensing probes, &corrosion rate measurement.

5. Pipeline installations guardedround- the- clock by ex-servicemenguards who are being monitoredshift-wise from maintenancebases.

6. Internal & external audit of thepipeline system being carried outas per ISO 9002.

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Raufeek M H, et al., International Journal on Occupational Health & Safety, Fire & Environment – Allied Science ISSN 2349-977X

7. External safety audits conductedby OISD.

8. Regular physical inspection ofthe above ground installations(SV, IP & RR stations) along thepipeline route.

9. Vulnerable locations identifiedand periodically checked.

10. Half yearly performance test ofall valves including remoteoperations.

11. Quarterly monitoring of pipe tosoil potenial and analysing thepsp trend. Corrective actionstaken accordingly.

12. Post-monsoon foot patrollingalong the pipeline.

13. Dry chemical powder (DCP) typefire extinguishers installed ateach IP stations and areperiodically checked.

14. Removal of encroachments andmaintenance of rou.

15. Operational mechanism of mainline valves are kept under lock &key.

Pipeline Maintenance:

♣ Right of Way Inspection andMaintenance:• Road and Highway Crossing –

Once in a 3 months.• River Crossing – Twice in a

year (Before and afterMonsoon)

♣ Pipeline Patrolling:• Ground Patrolling – Once in a

month• Foot Patrolling – Line walk

by Company Official twice inyear (Before and afterMonsoon)

♣ Pipeline Pigging:• Pigging Activities for Wet Gas

– Once in a year• Pigging Activities for Dry

Gas – Once in a 3 years♣ Intelligent Pipeline Pigging to be

carried out once in a 10 years anddata must be compared with dataobtained during Geometric Piggingbefore commissioning to ensure

health of pipelines.♣ Inspection of Cathodic Protection

System:• PSP (Pipeline to Soil

Potential) at feeding point– Once in a fortnight

• PSP Reading at Test LeadPoint all along the Pipeline– Once in a 3 months

• Cathodic Protection Rectifier– Once in a 2 months

• Installation of CorrosionCoupon and probe.

♣ Coating Survey: Pearson Survey /Direct Current Voltage Gradient(DCVG) / Continuous PotentialLogging (CPL) survey / CurrentAttenuation Test (CAT) to becarried out once in 5 years.

Equipment Safety:

1. Programmable logic controllers &safety interlocks.

2. Use of zener barriers to protecthazardous areas from over voltage.

3. Compulsory use of doublemechanical seals for all liquidhydrocarbon pumps.

4. Use of swivel joint metallic armsinstead of hoses for tankerloading.

5. Remote/auto loading of tankers/railway wagons through computercontrolled batch, controllerscalled "accuload".

6. Going for mounded storage vesselsinstead of above ground storagebullets / Horton spheres.

7. Installation of flame proof &increased safety motors.

8. Fire proofing of structure,equipment base and support legs.

Other General Safety measures:

1. Area Classification is done as perfollowing guidelines.(As per IS 5572: 1994 & Indian

Electricity Code SP -30 (BIS)

• Zone '0' area: dangerousatmosphere existscontinuously.

Raufeek M H, et al., International Journal on Occupational Health & Safety, Fire & Environment – Allied Science ISSN 2349-977X

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• Zone' 1 ' area: dangerousatmosphere likely to occurduring normal operation.

• Zone '2' area: dangerousatmosphere may arise throughfailure of the conditions.

2. Work Permit system must befollowed.

3. Vehicle Movement Control4. Restricted Smoking5. Emergency Planning6. Mock Fire Drill7. Fire Safety Training8. Personal Protective Equipment9. Safety Auditing10. Safety Committee

CONCLUSIONOperating the Cross Country Natural Gaspipeline system at high pressure,passing through thickly populated area,lack of public awareness, ongoingconstruction activities etc. posessignificant hazard in Indian context onSafest Method of Transportation. Hence,it is important to established robustmechanism for safe operation andmaintenance of cross country pipeline inIndia.

The integrity of Natural Gas PipelineSystem comes through the continuousefforts in all stages to ensure thatpipeline is designed, commissioned,operates and maintained as perstipulated codes and standards.Further, technological up-gradation inoperation, inspection and maintenanceenhance the safety of pipeline systemand increase the safety at a greaterextend.

REFERENCES1. http://www.pngrb.gov.in2. http://www.peso.gov.in/3. http://www.oisd.nic.in/4. ASME-B31.8 - Gas Transmission and

Distribution Piping Systems5. OISD-STD-138 - Inspection of cross

country pipelines – Onshore6. OISD-STD-105 – Work Permit System7. IGE/TD/1 – Steel Pipelines for High

pressure Gas Transmission8. API 1102 Recommended Practice for

Steel Pipelines Crossing Railroadsand Highways.

9. API 1104 Standard for WeldingPipelines and Related Facilities.

10. API 1107 Recommended PipelineMaintenance Welding Practices.

11. NACE-RP-01-69 RecommendedPractice Control of ExternalCorrosion on Underground orSubmerged Metallic PipingSystems.

12. NACE-RP-01-75 RecommendedPractice - Control of InternalCorrosion in Steel PipelinesSystems

13. OISD-STD-195 Safety in design,operation, Inspection andMaintenance of Hydrocarbon GasCompressors stations andTerminals.

14. OISD-STD-141 Design andConstruction requirements forcross country hydrocarbonpipelines.

15. API 1109 Recommended Practice forMarking Liquid Petroleum PipelineFacilities.

16. API 1110 Recommended Practice forPressure Testing of LiquidPetroleum Pipelines.

17. API 500C Classification ofLocations for ElectricalInstallations at PipelineTransportation Facilities.

18. API- 5L Specification for Linepipes

19. API- 6D Pipeline Valves