SUMMER INTERNSHIP PROJECT REPORT ONOVERVIEW ON TECHNICAL ASPECTS OF CITY GASDISTRIBUTION

Undertaken atSITI ENERGY LIMITED, MoradabadUnder guidance ofMr. Jeet Ram Verma (Chief Manager- Projects) M. A. Azeem (Chief Engineer)

Submitted by: Vibhu Yadav R010208064 B.TECH (Applied Petroleum Engineering (Gas)-7th Sem) University of Petroleum & Energy Studies (Dehradun)

CERTIFICATE FROM THE MENTOR

This is to certify that the project work on OVERVIEW ON TECHNICAL ASPECTS OF CITY GAS DISTRIBUTION has been prepared by Vibhu Yadav (R010208064), during his Summer Internship of 08 weeks at Siti Energy Limited, Moradabad under the Guidance of Mr. Jeet Ram Verma, Chief Manager (Projects).This project is a result of their original efforts and findings. This work has not been submitted to any other University or published any time before.

FORWARDED BY:Mr. Sabir Ahmed Siddique Mr. Tarang AroraDesignation: ManagerDesignation: Deputy Manager (Pipeline)(CNG)

-------------------------------------------------------- (SIGNATURE) (SIGNATURE)

Place: Moradabad Date: 05 August 2011

ACKNOWLEDGEMENTI am very thankful to SITI ENERGY LIMITED for providing me this opportunity to practically see all these things which we had studied during the last 3 years of our graduation. We are especially thankful to Mr. JeetRam Verma (Chief Manager-Projects) and M.A. Azeem (Chief Engineer) for giving us this project and for their continuous guidance during the course of our training. My sincere thanks to Mr. Tarang Arora (Deputy Manager CNG) and Mr. Sabir Ahmed Siddique (Manager Pipeline) who made all the possible effort for providing me the necessary practical/technical exposure and all the departments in the company (Management/Accounts/C&P and O&M.) which provided the necessary statistics to make the project more useful. I am grateful to Mr. Neeraj Joshi (Deputy Manager Pipeline), Mr. Gaurav Kumar Arya (Sr. Engineer Pipeline), Mr. Nishant Jain (Engineer Pipeline), MR. Gaurav Arora (Engineer CNG), Mr. Dhruv Pal Negi (Engineer CNG), for their encouragement and co-operation. They took painstaking effort in helping me to complete my project, a fruitful learning experience.

Submitted By: Vibhu Yadav R010208064 B.TECH (Applied Petroleum Engineering (Gas)-7th Sem) University of Petroleum & Energy Studies(Dehradun) Table of ContentsS. No. TOPICPAGE NO.

1.Certificate 2

2.Acknowledgement 3

3.List of tables5

4.Abstract6

5.Introduction7-9

6.Present scenario of natural gas in India10-12

7.Government regulation on CGD13-15

8.Company profile15-18

9.Technical standards19-20

10.Major components of CGD network20-62

11.Conclusion 63

12.References64

13.Annexure65

List of tablesS.No.Table no.Page

1.Table 1-Properties of natural gas7

2.Table 2- Comparative study of natural gas with other fuels8

3.Table 3-Demand of natural gas in India10

4.Table 4-India primary energy supply11

5.Table 5- Energy deficit in India11

6.Table 6-Spot LNG supply12

7.Table 7-Fuel characteristics21

8.Table 8- Gas analysis 25

9.Table 9- Cylinder data25

10.Table 10- Inter distance between buildings 33

11.Table 11- Inter distance between facilities at a CNG station33

12.Table 12- Economics of CNG usage34

13.Table 13-Comparison between PNG and LPG36

14.Table 14- 1 scm of gas is equivalent to..37

15.Table 15- Pipeline fittings39

16.Table 16- Flow meters46

17.Table 17- Meter specifications48

18.Table 18- Domestic regulator specifications50

19.Table 19- Conversion factors65

Abstract City gas distribution is an interconnected network of pipelines used for the distribution of gas to domestic/commercial/industrial consumers in the form of PNG (low pressure distribution network) and to the automobiles in the form of CNG (high pressure distribution network). PNG deals with the distribution of natural gas from bulk supply high pressure transmission grids and subsequently to medium pressure distribution mains through service distribution mains to the domestic consumers(at a pressure of 21 mbar) and to the commercial/industrial consumers at a pressure depending upon the demand of the consumer.On the other hand, CNG system deals with the dispensing of natural gas into vehicles at a pressure of 200 bar. The project throws light on the following points: Scenario of natural gas supply in India Opportunities available for establishment of CGD network. Major components of CGD network and their functioning. Technical standards and design constraints (of both national and international applicability) Fire & Safety aspects in CGD Business

INTRODUCTION Natural gasNatural gas is a gaseous fossil fuel consisting primarily of methane and other heavier hydrocarbons like ethane, propane, butane etc. until Heptanes along with some non hydrocarbon components like Hydrogen Sulfide, Nitrogen, Carbon Di Oxide and traces of Helium. It is formed from organic material that was formed as a result of deposition of dead plant and animals under high pressure and temperature beneath the earths surface. Typical Composition of natural gasMethane: 88%Ethane: 5%Propane: 1% CO2: 5%Others: 1%TABLE1: PROPERTIES OF NATURAL GAS Property Value/significance

AppearanceClear gas and burns with a blue flame

Density & phase0.717 kg/m3, gas

Boiling point-161.6 deg centigrade

Flash point-188 deg centigrade

Explosive limit5 to 15 % in air

Maximum flame temperature2148 deg centigrade

Color Colorless

Odor Odorless

Calorific value8500 kcal/scm

Specific gravity0.65(approx)

Note: The energy derived from natural gas is a result of the energy released by the breaking of molecular bonds in the presence of oxygen.Advantages of natural gas over conventional fossil fuels It is not toxic like hydrogen sulfide and ammonia. It is not corrosive like acid gases. It does not contaminate ground water. Simplest carbon structure. Complete and clean burning fuel. Least possible particulate emission. Environmental friendly

TABLE 2: COMPARATIVE STUDY OF NATURAL GAS WITH OTHER FUELSFuel unitNatural gas(1 scm)LPG 1 kgHSD 1 kgKerosene 1 kg

Cal. Value in k.cal/kg8500117501050010420

Heat transfer efficiency in %85805540

Net cal. Value in k.cal/kg7225940057754168

Combustion related properties of gasoline & CNGPropertiesGasolineCNG

Motor octane number80-90120

Research octane number92-98120

Molar mass (kg/mol)11016.04

Stoichiometric air-fuel ratio14.616.79

Stoichiometric mixture density(kg/m3)1.381.24

Lower heating value(MJ/kg)43.647.377

Lower heating value of stoichiometric mixture(MJ/kg)2.832.72

Flammability limits(vol% in air)1.3-7.15-15

Spontaneous ignition temperature(deg C)480-550645

Fossil fuel emission levels-pounds per billion Btu of energy inputPollutantNatural gasOilCoal

Carbon Dioxide117000164,000208,000

Carbon Monoxide4033208

Nitrogen Oxide92448457

Sulphur Dioxide111,2222,591

Particulates742,744

Mercury0.0000.0070.016

Present scenario of natural gas and its utilization in India Natural gas has emerged as the most preferred fuel due to its inherent environmentally benign nature, greater efficiency and cost effectiveness. The demand of natural gas has sharply increased in the last two decades at the global level. In India too, the natural gas sector has gained importance, particularly over the last decade, and is being termed as the Fuel of the 21st Century.TABLE 3: DEMAND OF NATURAL GAS IN INDIAYearOil(MTOE)GAS (MTOE)GAS (BCM)

2007-081404033

20011-121664449

2016-172146471

2021-2227897108

2026-27365135150

2031-32486197219

% growth5%7%

Source: integrated energy policy of the government,2006Assumptions: GDP growth assumed to be 9%, population growth assumed to be 1.1%, includes only commercial energy requirements

TABLE 4: INDIA PRIMARY ENERGY PROJECTED SUPPLY (MTOE)Year20102015202020252030CAGR

Oil45455555500.53

Natural gas39495658582.00

Coal2182202302352500.70

Nuclear energy8142229327.18

Hydroelectric23293641443.22

Total3333573994174341.34

TABLE 5: ENERGY DEFICIT IN INDIA (Mtoe)Year2011-122016-172021-222026-272031-32CAGR

Demand496665907122216516

Supply3333573994174341

Gap163308508805121711

Source: EIA statistics: 2008The domestic oil and gas sector in the country got a boost after the commencement of production of natural gas from Reliance Industries Ltds (RIL) Krishna Godavari fields and production of crude oil from Cairn India Ltds fields in Rajasthan.The gas produced in the western offshore fields is brought to Uran plant (ONGC) in Maharashtra and partly in Gujarat (ONGC-Hazira). The gas brought to Uran is utilised in and around Mumbai. The gas brought to Hazira is sour gas which has to be sweetened by removing the sulphur present in the gas. After sweetening, the gas is partly utilised at Hazira and the rest is fed into the Hazira-Vijaypur-Jagdhishpur(HVJ) pipeline which passes through Gujarat, Madhya Pradesh, Rajasthan, U.P., Delhi and Haryana. Major gas producing fields: Kg basin off AP collectively operated by reliance industries ONGC, GSPC. Mahanadi basin- ONGC Fields off Gujrat - Cairn Energy TABLE 6: Spot LNG supplied by LNG Petronet and other sources 1.Petronet LNGLNG supply in MMT

Dahej10

Kochi2.5

2.Shell Hazira3.0

3.Ratnagiri Gas Dabhol5.0

4.GSPC LNG5.0

Total(in MMT)25.5

Total( in MMSCMD)100

Source :EIA statistics 2008.(Note: the LNG received is then converted to RLNG and then transported through HVJ pipeline)

GOVERNMENT REGULATION ON CGD MARKET: PNGRB was setup on October 1 2006 in order to develop and increase fuel growth of natural gas market in India. It has laid down rules and regulations for CGD network for supplying gas to CNG station and PNG to household, industrial and commercial consumers. The players in this field can be classified into two: those who own the pipeline (today, GAIL is the biggest, followed by Reliance) And those who distribute the gas (Indraprastha Gas, Gujarat Gas and GSPC etc.).Bidding procedure There's a step-wise competitive bidding process for the licences. To start with, companies submit an expression of interest (EOI) to PNGRB for the cities they are interested in. If there's sufficient interest in a city, PNGRB calls for bids. Bidders have to meet financial (net worth-related) and technical (experience) parameters to submit bids.

PNGRB is targeting CGD bidding in 200 cities by 2012. For most cities, it will be a head to head contest between Reliance and GAIL. Currently CGD networks are operative in multiple cities including Delhi, Mumbai, Indore, Pune, Vijayawada, Vadodara, Surat, Ankleshwar, Ahmadabad and Kanpur.

Important characteristics of CGD business significant investment lengthy gestation period provision of tax incentives to companies interested in setting up these networks by the government Currently, the domestic tax law provides a 10 year tax holiday for laying and operating 'cross country' natural gas distribution network, including pipelines and storage facilities. Infrastructure of Natural gas interstate pipeline in India GAIL was the first company in India to pioneer city gas distribution project. In addition to marketing Natural Gas through Trunk and Regional Transmission systems, GAIL has formed joint venture companies to supply gas to households, commercial users and the transport sector. The backbone of this pipeline system is a national grid that circumnavigates and criss-crosses the country, and whose size is increasing by the day. GAIL has completed 7,000 km and is aiming for 13,000 km by 2012; Reliance has 1,400 km and is waiting for government clearance for another 3,000 km.CGD (City Gas Distribution)City Gas Distribution means an interconnected network of gas pipelines and the associated equipments used for transporting natural gas from a bulk supply high pressure transmission main to the medium pressure distribution grid and subsequently to the service pipes supplying natural gas to domestic, industrial or commercial premises and CNG stations (where pressure is increased instead) situated in a specified geographical area.Scope of CGD Business in IndiaNatural Gas usage in Indian cities has been limited primarily due to the scarcity of supply. However this scenario is undergoing change with several LNG projects/transnational pipelines under implementation, which together with new domestic Gas finds are expected to shore up the supply deficit in the next few years. Meanwhile the market for city gas distribution is also set to grow at an accelerated pace. The CNG demand got a boost with the Supreme Court directive on pollution reduction in 12 major cities in India. With a growing demand base and increasing supply options City Gas Distribution networks offer a tremendous investment opportunity. However in order to tap this opportunity the developers need to analyze several critical aspects of the project like: Demand build-up. Supply Infrastructure required Technological challengesWith the growing concern about environmental aspect, GOI started CNG distribution in cities. Various organizations like GAIL, IOCL, BPCL, GGCL etc. entered into this sector by forming JVs with other players and provided this sector the necessary thrust. The CGD network caters to the supply of PNG to domestic households and small commercial/industrial establishments and CNG to automobile sector. With the introduction of PSUs the Indian gas chain has become more structured and organized. Currently major oil PSUs like IOCL, BPCL and HPCL are providing substantial support in all parts of the gas chain with the formation of JVs like Green Gas Limited in Lucknow &Agra; IGL in Delhi-NCR etc.

COMPANY PROFILE SITI ENERGY LIMITEDSiti Energy Limited (SEL) is a .Company was incorporated in 2006 and was given work for implementation of City Gas Projects for supply of Piped Natural Gas (PNG) to domestic, commercial and industrial customers and Compressed Natural Gas(CNG ) to automobile consumers in the cities Agra and Lucknow. Now GGL is the only player in PNG & CNG distribution field of above cities.

Operation of Siti Energy in MoradabadSiti Energy Limited established its Daughter booster station in Lodhipur in 2006 which is situated on Delhi road about 18 km. from Moradabad city. It is distributing CNG to Automobile consumers by installing 3 dispensers there. Now SEL is completing its 38 km. pipeline from Lodhipur to Moradabad city. Except Lodhipur station SEL has 1 other daughter booster station on Kanth road. SEL taps the source of natural gas from GAILs pipeline. Gas from GAIL pipeline is given to CGS at Lodhipur (point of custody transfer) where it is supplied to 300 class pipes which are owned by CGD Company connected to pressure valve. This is connected to 300 class pipe; a Butterfly valve is installed here. Odorizing unit contains Ethyl Mercaptan which is mixed with natural gas. Then it is resent into the line going to filling station.

FUTURE PLANSSiti Energy Ltd. has vigorous expansion plans for the implementation of City Gas Distribution (CGD) projects in its authorized areas. Simultaneously, SEL is striving hard to explore business opportunities in other parts of the country as well.SEL is looking forward to provide the complete energy solution by moving beyond the CNG and PNG applications currently in existence which would enable it to enhance value for the stakeholders including customers, shareholders and employees. The company is committed to be a customer-oriented organization by adopting world class operational practices. Recognizing the fact that vehicle owners will not convert their vehicles to CNG until and unless CNG has been made available in adequate quantity and at many locations across the city, SEL has decided to make CNG available at multiple places and to ramp up the availability of CNG both in terms of quantity and geographical spread. NOTE: In Delhi, Company Secretarial and HR departments are not present

Major players in City Gas Business Mahanagar Gas Limited. Indraprastha Gas Limited. Bhagyanagar Gas Limited. Tripura Natural Gas Limited. Maharashtra Natural Gas Limited. Avantika Gas Limited. Sabarmati Gas Limited. Green Gas Limited. Gujrat Gas Company Limited Central U.P. Gas Limited Gail Gas Limited Adani Gas Limited MPCL Vadodra Mahanagar Gas Seva Sadan GSPC Assam Gas Company Limited Calcutta Gas Company Bombay Gas Company Great Eastern Energy Corporation Limited Siti Energy Limited HPCL Haryana Gas Company Limited

Technical Standards: In city gas distribution, some of the widely used standards referred for establishing the gas network and ensuring the safety of customers include: PNGRB Norms ASME B31.8 OISD Standards GAS CYLINDER RULES, 2004

1. PNGRB-Petroleum and Natural Gas Regulatory Board (PNGRB) Act came into force on April 03, 2006 to protect the interest of consumers and is engaged in specified activities to ensure uninterrupted and adequate supply of petroleum, petroleum products and natural gas in all parts of the country and promote competitive markets in Oil and Gas sector of India. This document lays down certain standards which need to be followed during setup of a CGD network in comparison with other standards as well. Some of the important aspects discussed in this document include: material and equipment (Schedule1A), welding (Schedule1B), piping system components and fabrication (Schedule 1C), design, installation and testing (Schedule1D), operating and maintenance procedures (Schedule1E), corrosion control (Schedule1F) and miscellaneous (Schedule1G).

2. Oil Industry Safety Directorate- The Oil Industry Safety Directorate (OISD) is an organization supported by all petroleum companies of India, like IOCL, ONGC, BPCL, HPCL, OIL etc. OISD has basically framed rules and guidelines for Safe Distances to be observed for various Facilities in an oil/gas installation.Eg: OISD-179: This standard lays down the minimum safety requirements at installations handling Natural Gas for dispensing into vehicles and minimum checks required in the vehicles by refueling stations. (For more details refer OISD-179 norms)

3. Gas cylinder rules: It is a draft published under explosives act 1884, and states following procedures with respect to CNG cylinders: filling, possession and import of cylinders markings on cylinders repairing of gas cylinders testing, handling and use general precautions safety aspects

4. ASME B31.8: This document lays down codes and procedures for designing, operation and maintenance of gas transmission & distribution piping systems. (for more details refer ASME B31.8 norms)

Major components of CGD CNG System: CNG is an acronym for compressed natural gas. The natural gas has less density as compared to liquid fuels and hence it is compressed to over 200 Kg/cm2 pressure to make it CNG for the use in automobile sector.TABLE 7: Fuel characteristicsCharacteristicsCNGPetrol Diesel

toxic to skinNo ModerateModerate

toxic to lungsNoModerateModerate

specific gravity (air =1)0.55(lighter)3.44

SourceNatural gasPetroleumPetroleum

The fundamental purpose of a CNG station is to dispense natural gas to vehicles. Where, practical CNG stations have been located close to a transmission pipeline. At these stations natural gas is tapped from pipeline and connected to the suction side of a compressor. The natural gas is then compressed and transferred to storage cylinders (cascades) and held until a vehicle is connected. When it has not been possible to locate a dispensing station close a transmission pipeline; mother-daughter concept has been used whereupon a mother station compresses the gas into cascades which are then transported by a road vehicle to daughter dispensing outlet. In some cases mother station also acts as a dispensing station.Types of CNG Stations Mother station Online station Daughter station Daughter /Booster Station

CNG Mother Station:CNG facility connected to natural gas pipeline at the CGS and at the isolation point. It is having compression capacity meant primarily to fill stationary cascades/mobile cascades (LCVs) for daughter stations and dispeners. Their filling capacity is also high.

CNG Online Station:CNG facility is connected with natural gas pipeline and having a compression capacity primarily to fill stationary cascades for dispensing CNG to vehicles. In case the online station has enough space to accommodate mobile cascades filling, it can be used to act as mother compressor station. Moreover its filling capacity is lower than mother station. CNG Daughter Station:In this station, CNG facility is not connected to natural gas pipeline and dispensing of CNG to the vehicles is done through mobile cascades. Gas is transported to stations through LCVs. These stations are generally not economical for the operating company as the pressure in the mobile cascades goes down very rapidly as a result of which the residual gas content left is more which remains unutilized. CNG Daughter Booster Station:Hydraulic Booster Compressor operated electrically is provided in CNG Daughter Booster Station, which is used to supplement the pressure energy of the residual gas in the cascade cylinders.CNG station components: The CNG system mainly comprises of:1. Compressors2. Cascades3. Dispensers4. LCVs1. COMPRESSOR:

Compressors are used to compress incoming natural gas for converting into CNG. Compressors are used for increasing the suction pressure (from 17-19 bar to 250 bar). Air Actuated Valves starts the engine of the compressor. Air coming from air compressors at pressure of 7-8 kg/cm2 is stored in a vertical vessel which provides storage of compressed air at constant pressure for pneumatic startup of the gas compressor. During pneumatic startup firing takes place and the compressor engine then continues to operate.Compressors are classified: According to the numbers of stages According to the capacity According to the design of crank case According to the arrangement of the cylinder According to prime mover used for driving the crank case (Motor driven or Engine driven)Compressors of following makes are generally used: Chicago Pneumatic DR( Dresser Rand)-used by GGL Safe Delta Sulzer Knox western BPCL

TABLE 8: GAS ANALYSIS AND ADDITIONAL OPERATING DATA OF DRESSER RAND- COMPRESSOR USED BY SELGAS COMPOSITIONMOLECULAR WEIGHTWT%

Nitrogen280.057

Cabon di oxide443.068

Hydrogen sulfide34-

Hydrogen2-

Methane1686.1

Ethane307.27

Propane442.34

Iso butane580.52

Normal butane580.64

Iso pentane72-

Normal pentane720.0053

Ethane plus components--

Ethylene 28-

Propylene42-

Water vapour18-

Total %100

TABLE 9: CYLINDER DATA AND PERORMANCESERVICECNG

STAGE123

CYLINDERCYLINDER 1CYLINDER 2CYLINDER 3

CYLINDER DIA(in.)43.1253.125-2.25

STROKE(in.)777

CYLINDER TYPEDASAHESACE

MATERIALC.IF.SF.S

STAGE(ONE)CYLINDER 1CYLINDER 2CYLINDER 3

INLET PRESSUREKSCG16.3152.1115.08

INLET TEMP.0C305555

DISCHARGE PRESSUREKSCG53.2117255

DISCHARGE TEMP.0C120116.11123.33

BHPHP203203203

SPEEDRPM685685685

CAPACITY AT INLETSCMH120012001200

C.I.- Cast Iron F.S.- Forged Steel KSCG- kg/cm2 SACE- Single Acting Frame End DA- Double Acting SAHE- Single Acting Outer End Engine driven by DR Make- Chicago Pneumatic Model- NG 1200M KW-200 RPM- 1485 Belt drive- V-belt drive

2. PROIRITY PANEL: It is situated inside the compressor house .The flow of the compressed gas from the compressor to the various equipments is decided by the priority panel & priority is given by programming. PRIORITY PANEL BANK FOR DISTRIBUTING GAS TO VARIOUS FACILITIES It is available in 3 bank modes i.e. 5,7 & 9 bank. The 9 bank priority panel has following lines in priority Car dispenser high Car dispenser medium Car dispenser low Car cascade high Car cascade medium Car cascade low Bus dispenser Bus dispenser cascade Mobile cascade( LCV) There is one inlet line directly coming from the discharge of compressor and a number of outlet valves depending on the station variable of cascade and dispensers. Check valves are provided in all the three outgoing lines of priority panel to prevent backflow of gas towards compressor. The pressure is set at two reference tubing.

Functions - Decides the supply of CNG from compressor discharge to either Dispensers/ Stationary cascades/ Mobile cascade, and Priority to first fill Low bank/ Medium bank/ High bank of the dispenser or stationary cascade.

3. DISPENSER: Dispenser is used to supply the CNG from compressor/ cascade to the vehicles (up to 200 bars). It acts a primary interface between a CNG station and the fueling customer. Since all the filling is dependent on the proper functioning of the dispensers, we have to ensure that these are always working properly. Dispensers consist of three banking system. SS316 tubing is used in dispensers. The flexible hoses fitted on the dispenser shall be mechanically and electrically continuous. The design, material and construction of hoses shall be suitable for CNG and shall withstand not less than four times the maximum working pressure of the system. The main components are:

Coalescent filter: it removes the oil content in the CNG. Particulate filter: this filters out the dust and dirt particles present in the gas. SOVs (solenoid operated valves/pneumatic valves): SOV comprises of an actuating coil and a plunger arrangement. The plunger gets picked up when coil is excited by a signal, thus allowing the gas to flow. When the signal is removed plunger moves to its original position due to spring force. Pneumatic valves are basically ball valves that operate with the force exerted by a pressurized fluid (air). Mass flow meter: it comprises of a sensor and a transmitter. Sensor works on the principle of coriolis force and senses the mass of gas flowing through it. Transmitter uses HART or modbus protocol using several configurations. It is connected to a voltage source of 18-100 V DC or 85-250 V AC. It transmits the pulses received from the sensor to CPO. Transmitter output range is 4-20mA. Isolation valve: it is used to isolate the hose from the dispenser in case of any leakage from the hose or three way valves or breakaway coupling etc. Safety valve: it is used to prevent excess pressure which can be there under abnormal conditions. The valve is set in way that whenever pressure in dispenser reaches above a particular pressure, it pops up and discharges the excess pressure in atmosphere. 3-way valve: it is used to dispense the gas into the vehicles. The three way valve is used because after filling we have to vent the remaining gas in nozzle to the atmosphere. Some common dispensers used in CNG station are: Compaq SAFE FTI TGT Nuovo PignoneThe flow of compressed gas into the dispenser is accordingly: The compressed gas from the priority panel goes to the dispenser through three pipes transporting gas at low, medium or high pressures. The compressed gas goes through the gas filters. Gas filters are according to the pipes as low, medium or high. The compressed gas from the low pressure pipe is going to go in low gas filter and accordingly. Then the compressed gas passes through the actuators. There are NRVs (No Return Valve) fitted. After passing through NRV the gas cannot return back into the system. The compressed gas then goes through the main pipe and flows through the mass flow meter where the amount of gas flowing into the dispenser is measured. There is a safety valve besides the mass flow meter to release high pressure gas safely and instantaneously into the atmosphere with any hazard. Then the compressed gas goes into refueling probe. There is an electrical panel too in the dispenser that sets all the valves and the flow of CNG through the probe is controlled. The electronic panel calculates the total price of gas filled in a vehicle. The dispensing unit shall be of a type approved by the chief Controller of Explosives/Statuary Authorities.

4. CASCADES: CNG Cascadesare consisting of a series of high-pressure cylinders arrayed in a manner to supply CNG to other vehicles. These CNG Cascades are known for their robust build quality. They also have a higher working, test and burst pressure parameters than CNG cylinders used in vehicles. The cascades are filled in three modes viz. low, medium, high. The cascades are filled at a pressure of 250 bars. The gas is withdrawn from a cascade in the reverse mode i.e. high, medium and then low. Cascades are primarily of two types: Stationary cascade: Stationary CNG stations are commonly installed in utility companies or other locations including automotive service stations, bus depots, and fleet garages.

Features :- Commonly installed in utility companies including automotive service stations, bus depots, and fleet garages Consists of an assembly of components Used to draw the gas from a distribution pipeline Compress gas into the storage system Located outdoors at ground level

Mobile CNG Cascades: - Mobile cascade is used for transportation of CNG. It is a structural container with an array of cylinders which can be loaded on a carrier truck and transported from one place to another. It is also known as LCV (Light Commercial Vehicle) and is used to transport CNG from Mother Station to Daughter station/ Daughter Booster Station. Mobile cascade

Features:- Consists of an assembly of components Require a booster compressor Designed to draw CNG from a CNG supply source Dispense it into vehicle mounted cylindersParameters to be considered during/after CNG station design as per Gas Cylinder Rules, 20041. The licensed premises shall be used only for the purpose and facilities it is licensed for. 2. CNG shall be dispensed only into those cylinders of motor vehicles, which are approved by the Chief Controller and have passed the periodic statutory tests under these rules conducted by a testing station recognised by the Chief Controller. 3. The CNG cascades, dispensers, compressor, piping, and other fittings shall be of a design suitable for CNG in conformity to OISD Standard 179. 4. The cascade should be made in a well-ventilated shed having a light roof or canopy with at least one side open. An area of at least 1 meter around the cascade shall be provided within the shed and the same shall be demarcated either by raised platform or by curb wall. In case, the cylinder cascade is mounted on LCV (Light Commercial Vehicle), the same shall be made totally immovable by suitable application of brakes and chokes. 5. No cylinder shall be filled with CNG in excess of the design working pressure. 6. Inter-distances between various equipments, storage cascades, dispensers, etc. installed in CNG dispensing station shall observe safety distances as per Table 10 & 11.7. The dispenser for dispensing CNG shall be of a type approved by the Chief Controller. 8. The vehicle shall have approved type of CNG kit fitted in accordance with guidelines of Ministry of Road Transport and Highways, Govt. of India. 9. No motor vehicle shall be fuelled while the engine is running and, where the vehicle is licensed for the conveyance of more than six passengers on hire, while any passenger remains in the vehicle. 10. Warning signs with the words STOP VEHICLE, NO SMOKING, NO OPEN FLAME PERMITTED, FLAMMABLE GAS, shall be displayed at dispensing station and compressor areas prominently. 11. All electrical fittings and equipment such as compressors, motors, switches, starters, etc., installed in the premises used for compressing and filling of CNG shall be of flameproof construction conforming to IS:2148 or such other specification as approved by the CCOE. 12. No alterations or additions shall be carried out to the premises without prior approval of the licensing authority. TABLE 10: INTER DISTANCES From buildings and outer boundaries to gas storage units Total capacity of gas storage cascade units (in liters) Minimum distance from buildings and boundaries (in meters)

Up to 4500 2.5

4500 to 10000 4.0

10000 to 100000 10.0

TABLE 11: Inter distances between various facilities in the CNG fuelling station Sl. No. Distance from (in meters) CNG Compressor CNG dispensing Unit Storage cascade Outer boundary wall/ CLF* MS/HSD Dispenser Vent of MS/HSD u/g storage tanks Filling point of MS/HSD

1 CNG compressor - 3 2 3 6 6 T-1 (Min-3)

2 CNG dispensing Unit 3 - 2 4 6 4 -do-

3 Storage cascade 2 2 - T-1 T-1 (Min-6) T-1 (Min-4) -do-

4 Outer boundary wall/CLF* 3 4 T-1 - 6 4 -do-

5 MS/HSD Dispenser 6 6 T-1 (Min-6) 6 - 6 -do-

6 Vent of MS/HSD u/g storage tanks 6 4 T-1 (Min-4) 4 6 - 6

7 Filling point of MS/HSD T-1 (Min-3)

*CLF - Chain Line Fencing. Note:- i) T-I denotes Table-I. ii) Distances shown as -shall be any distance necessary for operational convenience. iii) A suitable curbing platform shall be provided at the base of the dispensing unit to prevent vehicles from coming too near the unit. iv) A CNG cascade having cylinders of total water capacity not exceeding 4500 liters can be mounted on top of the compressor super structure. 13. Smoking, naked lights, lamps, source of fire, mobile phones or any other implements capable of igniting flammable vapour or gas shall not be allowed inside the premises. 14. Every person managing or employed on or in connection with the licensed premises shall abstain from any act whatsoever which tends to cause fire or explosion and which is not reasonably necessary and to the best of his ability, shall prevent any other person from doing such act. 15. The operators and attendants shall be fully conversant and trained with all the facets of the dispensing activities including operations, procedures, maintenance and hazards of CNG and the risk associated with the handling of the product. 16. The emergency telephone numbers of local fire service, police and the principal marketing company and emergency instructions shall be conspicuously displayed in the licensed premises.

TABLE 12: Economics of CNG usage (cost in Rs/km)FuelCarBusAuto

Petrol3.07-1.84

Diesel2.209.431.32

CNG1.338.750.70

Maintenance of CNG vehicles After conversion, the vehicle should be turned on gas at workshop after 1000 km to 1500 km. During normal servicing, nothing special is required for CNG kit except for cleaning of air filter. However in case of major maintenance/troubleshooting on CNG kit, it advisable to get serviced at the CNG workshop. Annual inspection of the kit should be carried out. The cylinder should be hydro-tested after every 5 yrs.

Gasoline engine conversions May need to improve cooling system efficiency May need engine oil cooler May need new valve seats Engine compression can be increased to increase efficiency

Diesel engine conversions May need to improve cooling system efficiency May need engine oil cooler May need new valve seats, guides and seals May need new pistons and rings Engine compression must be lowered May need a new camshaft Ignition system must be installed Cylinder head modifications are needed to install spark plugs Custom cam or crankshaft position sensors must be made

PNG System: PNG implies Piped Natural Gas i.e. natural gas which is supplied through pipes to homes and establishments.PNG is continuously supplied through the Hazira Vijaypur - Jagdishpur (HVJ) pipeline of GAIL.Characteristics and advantages over LPG system Pollution free Uninterrupted supply at all times Less storage area occupied as compared to LPG cylinders Gives a cost benefit of 10% to the user as compared to LPG. Can be used for multiple purposes like A/C, geysers, lanterns etc. System design is temper proof Environmental friendly and clean source of fuel: Its combustion results in virtually no atmospheric emissions of sulphur di oxide (SO2), and far lower emissions of carbon monoxide (CO), reactive hydrocarbons and carbon dioxide, than combustion of other fossil fuels. In fact, when natural gas burns completely, it gives out carbon dioxide and water vapor. Other properties are summarized in the table 13 below:Characteristics LPGPNG

CompositionMixture of propane & butanePrimarily methane

Relative densityb/w 1.4- 2.10.65( hence lighter than air)

Auto ignition temperatureb/w 410- 470 deg C570 deg C

Calorific value 10900 kcal/kg13570 kcal/kg

Physical propertyLiquefied at high pressure to store a high volume of gas in cylinders Remains in gaseous form under normal temperature and pressure

TransportationThrough LPG cylindersThrough pipeline

Source of supplyRefineries and fractionizing plantsFrom gas sources via processing plants

SafetyIn gaseous state, it is twice as heavy as air, hence remains trapped at ground level in case of any leakage. Hence dangerous.In the eventuality of any leakage, natural gas being lighter than air will disperse faster than LPG, hence the chances of accident are reduced. Moreover the PNG connection has built-in safety system that ensures tripping of regulator in case of leakage

Convenience Requires booking of cylinder and its changing, hence tiring job.Continuous round the clock supply.

TABLE 14: 1 scm of natural gas is equivalent to:-WoodCoalFurnace oilLPGElectricity

5-7 kg3-4 kg2 kg0.9 kg11.4kwh

Major components of PNG network1. DPRS (Distribution pressure regulating station/district regulating station) Located at various demand centres for domestic / commercial users typically consists of: Gas filter Heater (if required) Pressure reduction skid comprising active and monitor combination with minimum 50% redundancy with stream discrimination arrangement, including slam shut valve for over and under pressure protection with additional feature of under pressure protection if required(stream redundancy shall not be less than 2+1). Inlet and outlet isolation valves.Its main function is to reduce the pressure from 19 kg/cm2 to 4 kg/cm2.The capacity of the DPRS is determined based on the peak hour load.

Figure showing important components of DPRS

District pressure regulating station

2. IPRS( Individual pressure regulating station) : Located at the premises of an individual customer having facilities similar to DPRS however, monitor regulator may or may not be provided. Metering facilities may or may not be part of this station. Filtration facilities not provided

3. MRS MRS is metering and regulating station Located at the premises of an individual customer having facilities similar to DPRS however Metering facilities an integral part of this station. Filtration facilities provided

4. PIPELINES & FITTINGS: Steel, MDPE, G.I., Copper(TABLE 15)

G.I pipe

Copper tubing

MDPE pipeline

Carbon steel pipes

Copper fittings

Carbon steel fittings

Plastic fittings

Split tees

Important constraints to be considered while laying of PNG network as per standards of PNGRB & ASME B31.8 The area under consideration shall be classified under location class 1,2,3 or 4. Consideration shall also be given to loading due to following while selecting nominal wall thickness t as per ASME B 31.8 as appropriate: Overburden loads Dynamic and seismic loads Cyclic and vibratory loads Internal pressure fluctuations Geo-technical loads (including slides, differential settlement of piping, loss of support, and thermal effect of the pipeline on soil properties). Pipeline on bridges should be avoided. Upstream dry gas filter(s) shall be installed when rotary or turbine meters are used Protection against over pressure of pipeline or mains downstream of city gate station (CGS) shall be provided by means of: Active / Monitor Regulator System pressure relief valve(s) Over pressure shut-off valve(s) Sound pressure levels shall be limited to 100 dba. In order to prevent over pressurization of piping downstream of regulators / control valves, creep relief valve should be provided, When steel pipelines or mains are installed in areas that are normally under water, anti-buoyancy measures adopted shall be such that specific gravity of resulting installation is 1.10 or more. For eg. concrete weight coating, geo-textile bags filled with graded stones or anchorages, etc. to be used to prevent floatation When a buried steel pipeline or main has to cross any existing underground pipeline, cable, drain or other services, the pipeline shall be laid at least 300 mm below from such services. Clear distance between new steel pipeline or main running parallel to existing pipeline should be minimum 5.0 meters when heavy conventional construction equipment is expected to be utilized Miter bends and wrinkle bends are not permitted in pipelines and mains used in CGD networks regardless of operating hoop stress. Use of ductile iron piping is not permitted for CGD networks as per this standard. Plastic pipe shall not be used for Pipeline and Distribution Mains operating at pressure in excess of 100 psig. Nominal wall thickness of plastic pipe shall be calculated as per following formula: P = 2S * (t / (D-t)) * 0.32 WhereD = Specified outside diameter in mmP = Design pressure in psigt = Nominal wall thickness in mmS = Long term hydrostatic strength in barg (psig) determined in accordance with applicable pipe specification at temperature equal to 73F, 100F or 120F. Threaded joints in plastic pipe are not permitted. Plastic piping joints shall be made by Electro Fusion fittings only. Jointing of plastic piping by butt fusion method, solvent cement method, adhesive method, heat fusion method or by means of compression couplings or flanges is not permitted Use of thermoplastic piping in above ground piping is not permitted unless the piping is completely protected against deterioration Thermoplastic piping shall not be tested at material temperature above 120F (50 degree centigrade). Test medium shall be air or nitrogen for test pressure up to 100 psig. For test pressure higher than 100 psig, water shall be used as test medium. Test duration shall be minimum 24 hours for plastic distribution mains of length greater than 1 km and minimum 4 hours for length shorter than 1 km. Use of automatic shut-off device (slam shut valves) as a means of accidental over-pressure of high pressure distribution system is preferred DPRS/IPRS shall normally be equipped with minimum two safety devices. In steel distribution mains valve spacing should normally not be more than 3 km, In plastic distribution mains valve spacing should normally not be more than 1 km. Customer meter shall preferably be located in a well ventilated area. Service lines shall be sized for a maximum flow velocity of 15 m / sec. All plastic pipe and fittings shall be laid underground and shall not be exposed. The buried service lines shall be provided with a minimum cover of 1.0 m. For transition from plastic pipe to GI pipe, transition fittings shall be used. In case carbon steel section beyond transition fitting is below ground, it shall be protected against corrosion. Use of ductile iron service lines is not permitted. Piping connecting consumer meter set assembly to consumer gas appliance shall be either GI or copper up to last valve located near actual appliance. A metal seated leak detection cum excess flow shut off valve shall be provided near the appliance. Appliance shall be connected to gas line with a flexible and braided hose as per IS 9573. In no case the length shall be more than 1.5 meters. Both ends of the hose shall be firmly clamped on the nozzle by metallic clamps.

LAYING OF PIPELINE COMPLIANCE Road signs, warning lamps and barrier systems shall be provided on highway or other work locations which are accessed by pedestrians or vehicles. Underground utilities shall not be disturbed or altered without the prior consent and approval of the owner or authority concerned. Electricity cables shall be treated as "Live, unless the owner certifies them as "Dead".' The dead cable shall also be checked for any residual voltage. Where open cut techniques are used, a warning tape of Yellow colour shall be laid above the pipe, the difference in elevation of the pipe and warning tape shall be minimum of 200 mm. Trench width shall be at least 300 MM. The bed of the trench shall be free of sharp objects, stones etc. The trench should be padded with soft soil / sand to minimum of 100 mm below the pipe. At identified locations pipelines shall be provided with impact protection from excavating machinery as indicated in the figure below where h shall not be less than 500 mm,250 mm.

Where it is necessary to cross or run close to any other utility, a minimum of 250 mm clearance shall be maintained. In case the clearance is less, appropriate protection measures shall be taken. The relative position of PNG pipeline with respect to other underground utilities shall be as shown along side:Provision shall be made for locating the buried PE pipe by installation of electrical conductive trace wire or plastic coated metallic tape or any alternate proven locating method.

PIPELINE MARKERS: Basically 4 types of markers are used. Rout markers shall be placed on the entire pipeline at a distance not exceeding 50 m. and also at bends in the city. Additional sign/ markers should be installed to indicate the presence of pipeline at the road, highways, rail-crossings, stream crossings and places there is a probability of damage or interference. Further, warning signs shall be displayed on the service line to consumer premises. A marker shall be marked in easily readable local language with at least the following: Name of PNG distribution company Contact telephone number(s) in emergency. Location code Warning- High Pressure Gas Line and Other Utilities to take permission from PNG Distribution Company before digging etc.Working of PNG Network Supply of natural gas at 47 bar from the main cross country pipeline (carbon steel pipeline network) to the CGS. Pressure reduction skid with 50% redundancy reduces the pressure from 47 bar to 19 bar and odorises the gas to facilitate leak detection. The gas at 19 bar is provided to large scale industrial consumers Tappings from this pipeline transfer natural gas to various areas where depending upon the demand, DRS are installed for further reduction in pressure from 19 bar to 4 bar. Piping system downstream of DRS consists of MDPE pipeline whose grade, nominal outside diameter, wall thickness, tensile strength and other parameters are calculated from various software available in the market. Downstream of DRS, Metering and Regulating Stations(MRS) are provided which further reduce the pressure (depending upon the customer like small scale industries may reduce the pressure to 2 bar) At the customer premises, transition joint is provided which allows change of pipeline type from MDPE to GI due to safety and durability constraints. Service regulators reduce the pressure from 4 bar to 100 mbar GI risers enable the pipeline to be raised uptil the customer meter which again reduces the pressure from 100 mbar to 21 mbar. Isolation valves are also provided for emergency shut off of gas supply And finally, the gas is supplied to the customer appliance through copper tubings.5. Metering & Regulatory system-Metering system- Generally Rotary or Turbine meter are used for metering facility. Gas flow is generally measured by RPD meters.TABLE 16: TYPES OF FLOW METERS Meter Principle Advantages Diagram

Diaphragm/BellowDiaphragm expands and contracts, liver converts linear motion of it in rotary motion of crank shaft.These are positive displacement type meters.

RotaryThe rotational movement of the crank shaft serves as a primary flow element and may produce electrical pulses for a flow computer.These are highly machined precision instruments capable of handling higher volumes and pressures than diaphragm meters

TurbineA small internal turbine measures the speed of the gas, which is transmitted mechanically to a mechanical or electronic counterTurbine gas meters infer gas volume by determining the speed of the gas moving through the meter.

OrificeA type of differential meter which infer the rate of gas flow by measuring the pressure difference across a deliberately designed and installed flow disturbanceThey are well accepted and understood in industrial applications since they are easy to field-service and have no moving parts.

Ultrasonic flowUltrasonic meters measure the speed of gas movement by measuring the speed at which sound travels in the gaseous medium within the pipe.Inexpensive varieties of ultrasonic meters are available, which can be used to measure flow in any dia. of pipe without modification

TABLE 17: METER SPECIFICATIONSMETER SPEC METER TYPE MIN. FLOW (/100) SCMHMAX. FLOW (*1.6) SCMHMOP (BAR)

DiaphragmG1.60.0162.50.5

RPDG2.50.02540.5

TurbineG40.04060.5

UltrasonicG6.50.065101

G100.10161

G160.16251

G250.2540

G400.4060

G600.60100

G1001.00160

G1601.60250

G2502.50400

G4004.00650

G6506.501000

G100010.001600

Regulating System: A pressure regulator is a valve that automatically cuts off the flow of a liquid or gas at a certain pressure. Regulators are used to allow high-pressure fluid supply lines or tanks to be reduced to safe and/or usable pressures for various applications.A regulator includes a restricting element, a loading element, and a measuring element: The restricting element is a type of valve. It can be a globe valve, butterfly valve, poppet valve, or any other type of valve that is capable of operating as a variable restriction to the flow. The loading element applies the needed force to the restricting element. It can be any number of things such as a weight, a spring, a piston actuator, or more commonly the diaphragm actuator in combination with a spring. The measuring element determines when the inlet flow is equal to the outlet flow. The diaphragm is often used as a measuring element because it can also serve as a loading element.In the single-stage regulator shown below, a diaphragm is used with a poppet valve to regulate pressure. As pressure in the upper chamber increases, the diaphragm is pushed upward, causing the poppet to reduce flow, bringing the pressure back down. By adjusting the top screw, the downward pressure on the diaphragm can be increased, requiring more pressure in the upper chamber to maintain equilibrium. In this way, the outlet pressure of the regulator is controlled.

Types of regulators used in CGDService regulator: it is a regulator installed on a gas service line to control the pressure of gas delivered to the customer.Monitoring regulator: it is a pressure regulator set in series with another pressure regulator for the purpose of automatically taking over in an emergency the control of the pressure downstream of the station, in case that pressure tends to exceed a set maximum.Pressure regulating station: it consists of equipment installed for the purpose of automatically reducing and regulating the pressure in the downstream pipeline or main to which it is connected. Including are piping and auxiliary devices such as valves, control instruments, control lines, the enclosure and ventilation equipment.Pressure limiting station: It consists of equipment which under abnormal conditions will act to reduce, restrict, or shut off the supply of gas flowing into a system in order to prevent the gas pressure from exceeding a predetermined value. While normal pressure conditions prevail, the pressure limiting station may exercise some degree of control of the flow of the gas or may remain in the wide open position. Some common examples of gas regulators include pressure relief valves (PRV) pressure regulating valve(PRV) pressure control valve(PCV) slam shut valve(SSV)TABLE 18: Important specifications of domestic regulatorServiceNatural gas

DesignDirect acting spring control pressure regulator with in-built pressure regulating valve type balance regulating unit to ensure a constant outlet pressure having insufficient downstream pressure slam shut device and relief valve.

InstallationSuitable for outdoor installation, tamper proof and corrosion resistance for a life period of 25 years.

Installation positionHorizontal/vertical

Capacity2.5 m3/hr (actual)

Inlet pressure100 mbar(g)/(100-300 mbar(g)

Design pressure6 bar

Outlet pressure set point21 mbar(g)(factory set point)(spring range 18-30 mbar)

Over pressure cut off point-

Under pressure cut off point15 mbar(g)

Creep relief valve-

Operating temperature0-40 deg C, Design 65 deg C

CasingCasing and body of die cast aluminium / steel conforming to ASTM A216 WCB and water weather proof/corrosion resistant for outdoor installation.

Fire resistanceAs applicable

DiaphragmSynthetic rubber

InternalsStainless steel, brass seal of nitrile rubber or aluminium

FilterEssential(inbuilt)

Failure positionClosed

Type of resetAuto/manual (vendor to confirm)

Note: The domestic regulators are mainly of diaphragm type and are designed on various operating capacity, pressure and temperature depending on the requirements of the customer.Advantages of PE over steel: PE is non-conductor and therefore is not subject to galvanic corrosion. It is almost completely resistant to inorganic chemicals and most organic chemicals. It is a thermoplastic material and is easily jointed by heating and pressing together two components to form a joint as the parent components. Because of its flexibility, small diameter pipe can be coiled into long lengths for easy transport and installation. Its flexibility also allows PE in the smaller sizes to squeezed shut in an emergency situation thus reducing the need for the installation or large numbers of expensive and potentially high maintenance system block valves.

Disadvantages of PE over steel: The pipe is softer and more susceptible to damage during transport, installation and future third party activities in the vicinity of the installed pipe. Because of its thermoplastic nature PE is weaker at higher temperatures. At full design pressure it should not operate at temperatures above 40C. Its use is therefore restricted to underground only. Because of its thermoplastic expansion (10 times greater than steel) temperature changes need to be taken into account during construction. It has a tendency to cold flow or creep under load. An internal stiffener is required to prevent cold flow whenever a mechanical joint is employed.

Pipeline System Pipeline network consists of steel pipeline, polyethylene pipeline, galvanized iron pipeline and finally copper pipeline. A typical CGD network should consist of the following Primary network: A medium pressure distribution system comprising of pipelines, gas mains or distribution mains normally constructed using steel pipes and connects one or more transmission Pipeline to respective CGS or one or more CGS to one or more DRS. The maximum velocity in the pipeline network should be limited to 100 ft / sec (30 m/sec) immediately after pressure regulating instrument. Secondary Network: A low pressure distribution system comprising of gas mains or distribution Mains usually constructed using thermoplastic piping (MDPE) and connects DRS to various service regulators at commercial, industrial, and domestic consumers. The network should be sized for maximum flow velocity of 100 ft / sec (30 m/sec). Tertiary Network: A service pressure distribution system comprising of service lines, service regulators and customer /consumer meter set assemblies constructed using a combination of thermoplastic (MDPE) piping and GI /copper tubing components. Tubing / Hose pipe for connecting consumer meter set assembly and consumer appliance: The connection between consumer meter set assembly and gas appliance (provided by consumer) may be made by GI pipes or copper tubing or steel reinforced rubber hose. Steel reinforced rubber hose shall conform to IS: 9573 LAYING OF PIPELINE NETWORK Laying of the pipeline starts after the issue of right of issue and the route of pipelines under the City gas pipeline project. Excavation works are performed so as to enable the pipe to be laid in conformity with the levels depths, slopes, curves, dimensions and instructions shown on drawings, specifications. Detailed Process Of PE Laying. The detailed process of laying of the PE is handed over to the contractors. The various steps or the technical requirements for the PE laying are as follows, PE Excavation. PE Trenching. PE laying. Electro fusion jointing. PE Valve chamber. PE testing. Tap off from in operation gas mains. PE route marker.PE Excavation Excavation for the PE starts after the issue of right of issue and the route of pipelines under the City gas pipeline project. Excavation works are performed so as to enable the pipe to be laid in conformity with the levels depths, slopes, curves, dimensions and instructions shown on drawings, specifications. It is done under the direction of the company. Trail holes refers to the small pits which are generally dug before the actual excavation process for determining the pipe route and locate other underground plant or investigate possible obstruction if any e.g. telephone wires, cables, water lines, pipelines belonging to other companies. The trial holes are normally preplanned i.e. the location of between the trial holes is normally at a distance of 25m. They are excavated to a depth of pipe and an addition of 250mm. These holes are not closed immediately. They are protected and fenced. The trial holes are planned in such a way that there are no abandoned trenches and also to avoid insufficient trial holes. The excavated trench is maintained on stacked centre line as per the sheets approved and also taking into account of the curves of the pipelines. Proper care is taken while trenching to ensure all underground structures and utilities are disturbed to the minimum. The crossings wherever necessary is provided and maintained for the general public property owners or tenants to cross and also to move any stock from one side of the trench to another. Trenching is made in sufficient slopes on sides in order to minimize collapsing of the trench. In places, where there is any danger of landslides the pipeline trench is maintained open for time required to lay the line i.e. the work in that area is completed in less time and covered. The soil stability is analyzed in areas like drainage, ditch etc. The bottom of the trench is normally maintained in the square form to the maximum extent with the equipments so as to avoid the hand grading at the bottom of the trench. The bottom of the trench is made free of loose rocks, pebbles and trim protruding routes from the sides of the trench wall. A stretch of 12m is allowed to remain excavated before joining or back filling. Any kind of rock which cannot be drilled using sledge hammer, chisel is considered as hard rock. Any other Plain cement concrete (PCC) or Reinforced cement concrete (RCC) encountered during excavation are removed in supervision of authorities as the cost of removing those type of obstructions is high.PE Trenching Trenching refers to the making of holes i.e. opening the ground wide apart. It is classified into 2 types,

Open Cut.

Boring.

Red boring.Red boring refers to the boring of ground without opening the ground wide apart using the normal tools i.e. by hand.

Machine Boring.When the boring is not possible by red boring, machine boring is made use of. This happens when hard obstructions are encountered.The design of the depth of the trench varies for different locations as follows,

For distribution main 1.5m

Minor water crossing or canal 1.5m

Uncased or cased road crossing 1.5m

Rail or road cased crossing 1.5m

Normal areas 1.2m

The above mentioned depths may vary depending on the locality. In case of any difficulties in maintaining the required depth due to unavoidable factors the new depth shall be decided and put in to effect in the particular area only.

The width of the trench is maintained in wide enough to provide bedding around the pipe and to prevent damage to the pipe inside the trench. The distance between the ground and the bottom edge of the pipe is 50 mm for 63mm diameter pipelines and 100 mm for pipes larges than 63 mm which included the 90 and 125 mm pipes.

The following clearances are provided between the external wall of the gas pipe and the external surface of the other underground assets in the locality.

150 mm where the gas pipe crosses other assets, other than electric cables where the clearance is 300mm.And 300 where the gas pipe to be laid is on a similar alignment to the other assets.

In places where this clearance cannot be maintained due to various reasons, suitable barrier protections are installed between the pipe and the service line like the electric cable. RCC half round hume pipe is constructed along the trench.

All the works in the municipal or public roads are required to be executed as per there codes and conduct with a view to cause minimum inconvenience to pedestrian and vehicular traffic. All the trenching works are carried out with proper caution. E.g. before commencing of the excavation the caution board & information board as per the standard size, shape and color are installed at the site. The crown of the backfilled earth is maintained between 50mm and 100mm and is free from sharp edged stones & boulders. The site is maintained neat and clean without causing any nuisance to the public until the completion of the work.

In case of rain dewatering is done prior to back filling. This is maintained strictly for the protection of the gas pipeline. While back filling the mud or the soil is cautiously done such that there is no extraneous material or hard lumps of soil near the laid pipeline which could damage the line or the coating or leave void spaces in between the fillings. The surplus material is neatly crowned over the trench and adjacent excavated areas on both sides of the trench. Little extra allowance of mud is put over the trench such that it comes to the normal level during settling.

In cases where rock, gravel, lumps of hard soil or materials are encountered at the time of trench excavation, sufficient sand is placed around and over the pipe to form a protective cushion extending at least to a height of 100 mm above the top of the pipe. Thorough and proper compaction is done where in places where the trench is dug like, the drive or road ways. Special compaction methods are adopted. Trench excavated in dikes which belonging to the property of railways or which are the part of the main roads are graded and backfilled in their original profile and condition. The backfill materials if required are supplied.

PE warning grid or mat are placed on the distribution main and on service lines inside premises after backfill of the trench up to a height of 300mm after the sand bedding. The warning mat is unrolled centrally over the pipe section and thereafter the backfilling is done. All the excavated material which will be required for backfilling are kept separately and properly. In areas of roads or pedestrian places the refilling are done immediately to avoid inconvenience to the public. The back filling is assumed to be complete after the joining of pipes are complete. During the backfilling of the trenches in private society premises, municipal premises and panchayat premises, watering and ramming or mechanical compaction are carried out. Excess soil in the area is cleared off the site and is dumped at suitable location. Experienced supervisor is always present at the site to decide on various factors in the required situations. A third party officer is also made to be always available on the site. A prior information of excavation is given to the people in the area where the work is to commence in advance for their prior arrangements. Turf is replaced in highly developed grass area. In lesser grassed area top soil are replaced during the restoration process. In areas where the restoration works cannot be completed immediately, alternate arrangements are done temporarily for the traffic and the pedestrians.Boring In some areas where the normal trenching cannot be carried out, trenchless technology is carried out which is known as the boring. This is mainly done while the crossing of the roads. The boring is carried as per the requirement. The survey of the underground utilities are done before the boring process so that the other pipelines are not damaged. The cost of boring is costly i.e. 5 times the normal trenching. Hence, the boring is done in required areas only.

In areas like road junction, front of the society main gates, crossings are done in phases during the night times due to the traffic problems. The works are done so as to finish the work in night itself. If in case any area is left uncovered or not completed by night, steel plates are provided are for the movement of traffic in day time. PE laying The laying of the MDPE pipelines commence only after the ensuring of the proper dimensions and clean surface of the trench. The trench bottom is made to be free from the presence of cuts, stones, roots, debris, stakes and rock projections up to 150 mm below the underside of the pipe and any other material which could make perforations or tearing of the pipe wall. After ensuring of all the above factors, the MDPE coil is uncoiled smoothly inside through proper process and care inside the trench ensuring no damage to pipe coil during laying. It is ensured that the pipe caps are provided before the lowering of the pipeline. The trench after this is released for backfilling leaving adequate lengths open to the ends for joining. Before lowering of the pipeline a sand bedding of fine soil is done at the trench bottom. Similarly after lowering of the pipe the trench is filled with sand around and up to 100mm from the top of the pipe. Proper inspections of pipes and fittings are done before the releasing of the latter from the store and the defects are reported to store authorities. Proper care is taken for PE pipe and fittings after issued from the store till the transporting storing sheltering the pipe near the trench, uncoiling of the pipe by proper process and sufficient man power, lowering of pipe in the trench or pulling of the pipe through the trench such that no external damage is caused to the pipe. Electro fusion jointing Jointing of the pipes is normally carried out by the electro fusion process based on the requirements. Proper care is taken during the EF jointing such that there is no failure of the joint. Electro fusion Electro fusion is a simple method of joining PE pipes in circumstances where butt fusion is not practicable, such as where valves, elbows, and tees must be added. Prefabricated fittings are used, incorporating an electrical heating coil which melts the plastic of both the fitting and the pipe, causing them to fuse together. The characteristics of the fitting to be welded, such as the fusion time, are registered via a barcode on the fitting. On swiping the sensor over the bar code the required setting time and temperature are set and on click of start the process starts. An electro fusion control unit (ECU) supplies the electrical energy necessary to heat the coil. When the coil is energized, the material adjacent to it melts and forms an expanding pool which comes into contact with the surface of the pipe. The continued introduction of heat energy causes the pipe surface to melt and a mixing of pipe melt and fitting melt takes place, this is vital to produce a good weld. Following the termination of the heat cycle, the fitting and the pipe are left to cool and the melted material solidifies to form a sound joint. Hot and cold zones, sometimes called melt and freeze zones, are formed after energizing the coil. The length of these zones is particularly important. Each zone ensures that fusion is controlled to a precise length of the socket of the fitting and that the melt pressure is also controlled throughout the entire jointing process. The precisely controlled pitch and positioning of the coil in relation to the inner surface of the socket ensures uniform heat distribution. The basic fusion parameters: temperature, pressure and time, are controlled by the ECU which is programmed to establish these parameters from the barcode read from the fitting itself. The ECU also provides a permanent record of the procedure followed. Compact ECUs are now available that allow in-trench electro fusion welding to be carried out safely by just one man. The effectiveness of electro fusion depends on attention to preparation of the jointing surfaces and ensuring that the surfaces to be welded have satisfactory contact during the welding and cooling cycles. The pipe surfaces to be fused need to be scraped to remove the surface oxidation layer prior to fusion. Pipe clamps or other approved methods of restraining, aligning and re-rounding the pipes during the fusion cycle should be used. To prepare the jointing surfaces the pipe surface must be scraped with an appropriate pipe scraper, as recommended by the pipe or fitting manufacturer, to remove the entire surface of the pipe over the area indicated, to a depth of approximately 0.3mm. Metal files, rasps, emery paper etc are not suitable end preparation tools. Following scraping the scraped surface must be wiped with an authorized Isopropanol impregnated pipe wipe, as recommended by the pipe or fitting manufacturer, to remove any dust residue. Methylated spirits, acetone, methyl ethyl ketone (MEK) or other solvents are not recommended for wiping the scraped surface. The prepared surfaces must completely dry before proceeding. The resulting joint, when properly made, is as strong as the original pipe and can withstand all the loads applied during routine installation and operation. All the fittings related to electro fusion are according to the design standards. The pipeline is normally flushed with air to remove dust, water mud etc which would have entered the pipe during the laying process. Before jointing the packing sand is placed under the pipes on both the sides of the joint to keep the pipes in line and correct during the jointing process. The alignment clamps with correct size are used whenever necessary to align the pipe during the electro fusion jointing cycle. It is a usual practice to make a joint of electro fusion fitting on the same day of laying. The electro fusion joint is inspected before the restoration of the trench so as to ensure the leakage. In case of leakage the joint is redone with a separate coupler to prevent future damages to line. The time of electro fusion for the normal 90mm MDPE is around 42secs and a temperature of 48 deg C is to be maintained. This reading is noted from the meter. The various types of the joints which are used in the coupling or jointing of the MDPE pipes are normally 3 typesI. Coupler II. Tee III. Elbow Figure 6.1 Types of Joints used for coupling PE Valve chamber At certain areas the installation of the PE stop valves and the construction of the valve chamber is required. The valve chamber can be constructed in any type of soil. It includes conveying and spreading the stuff embankment within 200mm from the end of the cutting with all required lead and lift to required gradient and chamber. The cement, bricks, coarse sand are supplied and the fine gravel (machine crushed). The ratio of cement, coarse and aggregate 40mm is 1:4:8. The necessary PCC work in the annular space is carried between PE pipe and brick wall for sealing. The fix heavy duty RCC manhole chamber circular cover with square frame with the desired load capacity and the dimensions mentioned in the designed standard drawing. The remaining PCC work around the precast frame is carried out to fix the precast frame on the chamber to avoid any displacement. The PE stop off valves are installed in pipe system operating at the pressure above 110mbarg. The distance between each stop off valve is 1500m approximately for 125mm dia. pipe and 2000m for 90mm dia. pipe. This scope covers the necessary reopening of the charged pipe i.e. providing temporary bypass, squeeze off & cutting of PE pipe, installation of PE stop off valve, removal of temporary by pass, construction of valve chamber as mentioned above.

In case of delay in construction of valve chamber on any charged or uncharged pipeline, the PE stop off valve is properly wrapped and is backfilled in such a manner that the valve is not damaged.PE Testing Pressure testing is carried out with compressed air or nitrogen gas. The progressive pressure testing for the main pipelines and all the PE 100 pipelines SDR11 are carried out at a pressure of 6barg, for a time period of 24 hours. The reading of pressure is taken for every one hour. The leakages in the pipeline can be found out by this method. Any unaccountable loss in pressure in the line during the test period implies the leakage in the pipe, else vice versa. The stabilization period throughout the length of the pipe is normally half an hour which is assumed. All the measuring instruments which are used are totally tested and approved by the company. All the testing are witnessed by the company authorities. Purging is also done with the help of nitrogen. The nitrogen cylinders used are checked for their label, certification and tests. The testing carried out during the commissioning process includes the testing of the charged line for the composition of the gas. The methane content in the gas is tested using the specified meters. The oxygen content in the line is also checked up. The maximum allowable range of oxygen in the line is 0-2%. Normally the oxygen content in the line is 0.2%. The testing is done with all necessary regulators, hoses and connections, which are in good condition and working order. A record of all the purging plan before the commencing of the purging work is kept as a reference drawing. The plan includes the provision of the following materials and equipments. Fire extinguisher.

Purging adaptor

Purge stack with flame trap and gas sampling point.

Gas sampling equipment

Squeeze off tool.

The design of PE pipe networks should follow conventional network practices with the installation of valves at convenient or critical locations. The valves can then be operated to isolate sections of the pipe network for maintenance.

Additionally however PE pipe networks have the advantage that more localized isolation can be implemented by the use of pipe squeeze-off. Squeeze-off is used in routine and emergency situations to stop or nearly stop flow in PE pipe by flattening the pipe between parallel bars.

PE pipe squeeze-off utilizes the ductility of PE by allowing the pipe to be squeezed together using relatively simple but specially designed squeeze-off tools thus preventing the flow of fluid and isolating the pipe section. It is important that only specifically designed tools are used and that the squeeze-off controls are set for the specific diameter and SDR of the pipe in order to control the degree of compression of the PE pipe and prevent any damage.

The squeeze off tools are generally mechanically operated up to about 125mm diameter and hydraulically operated for larger diameters. However squeeze-off equipment is not readily available for the largest diameters of PE pipe. It is important to follow the manufacturers instructions when using these tools and to use tools appropriate for the pipe diameter and SDR. Also the tools need to be capable of resisting the operating pressure of the pipe, and there are limits to the pressures that they can sustain.

Properly implemented squeeze-off, using the correct tools, is not expected to cause damage to the PE pipe, which regains its circular cross-section after the tool is released. However squeeze-off is not recommended to be done more than once at any location. If repeated flow control is required a valve or an appropriate flow control device should be installed in the system.

Squeeze-off is not intended as a means to throttle or partially restrict flow. Complete flow stoppage may not occur in all cases. When squeezing larger pipes, particularly at higher pressures, some seepage is likely. When seepage is not acceptable, it may be necessary to vent the pipe in-between two squeezes-offs. Any work performed must be downstream of the second squeeze-off.

Inflatable bag flow stopping equipment can also be used for PE pipes. A saddle fitting needs to be fixed to the pipe, through which the inflatable bags are inserted. It is important that the correct saddle fitting is used compatible with the equipment being used. Reference should be made to the manufacturers instructions.

Adequate and sufficient trench is provided for commissioning process or providing tap off. The reopening of any trench might be required during the commissioning process. . The maximum trench dimensions which might be required during the commissioning is 2.5m by 1m.

PE Route Marker The route marker can be defined similar to a milestone. The PE route marker shows the route of the laid pipeline. This is for the easy reference for finding the route. The Route marking process is to be completed before the commissioning process. The route marker is normally laid for lines in which the pressure of the line is greater than 110mbarg. The distance between each route marker is approximately 300m. The precast of RCC mix of 1:1.5:3 is required for the route marker stone. The route marker stone is casted as per the design requirements. For easy understanding of the route marker in the diagrams it is represented by the yellow color. A 6mm smooth thick cement plastering work is to be done over the projected route marker including scaffoldings, curing etc.

Tap of from charged gas mains The taping process from the charged gas line is a tedious and time taking work. This is done in case of emergency purposes. The number of live connections from the charged lines can be minimized by proper planning and synchronizing medium pressure network charging for a particular area. The flow stopping devices are used such as squeezers. These are used only on the MDPE lines as they have their property of regaining their after squeezing. The method to be used for each connection, the number and type of flow stop devices to be used is to be determined by the company. Records to be maintained The various records which is maintained to ensure the proper laying of the line and also the cost of laying is as follows, Daily progress report. Approval for technical deviation if any. Material reconciliation report as in the designed format. The testing report of the PE network with reference drawings as per the desired codes Employees presence registers on site during the PE laying. Other specific documents wherever necessary. Organizational chart before the starting of the work. Details of tools resources and tackles before start. Figure 6.2: Typical commercial gas main line trench

CONCLUSIONOn Demand / Supply Terms Large gas finds from domestic sources Availability of gas is increasing. Dependence on liquid fuels is decreasing As a result of above factors the opportunities for utilization of natural gas in sectors like fertilizer, power and city gas is also increasing. Moreover environmental constraints on reduction of carbon emissions and the government declarations on the increase in the subsidy of LPG have also boosted the growth of CGD network. Which standard to follow? In city gas distribution, safety is given prime importance i.e. while referring standards such as PNGRB/ASME B31.8 etc. then standard providing maximum safety factor is considered.On technical terms City gas distribution is a highly complex system consisting of network of pipelines, compressors, metering and regulating facilities and pressure reduction skids; hence requires highly trained personnel to control their operation. Effective monitoring of the network can be achieved with the help GIS/GPS/MMI/SCADA systems. Pipeline laying activity involves great risk and responsibility as the engineers need to incorporate maximum design factors, safety factors and rugged material specifications in order to ensure optimum operation and safety against unavoidable accidents. Continuous and effective functioning of the systems can be achieved by means of conducting Performance Tests & Schedule Maintenance within regular intervals of time. The operating company are emphasizing on the connection of their dispensing stations directly to their pipelines rather than opting for DBS.On human grounds: Team work and feeling of collective responsibility are the only mantras to ensure success story of an industry. Employee retention and talent pool conservation are also important factors to consider

REFRENCES Regulations of Petroleum & Natural Gas Regulatory Board ASME B31.8 (Design, Installation and Testing) Gas Cylinder Rules,2004 OISD STD-179 Other documents provided in GGL eg: equipment catalogs http://www.ontime.methanetomarkets.org/m2mtool/index.html http://www.sitienergy.com http://www.angiinternational.com http://www.petroleum.nic.in http://www.kgbasin.in http://www.gglonline.net http://www.gailonline.com http://www.wikipedia.com http://www.mahanagargas.com http://www.adanigas.com http://www.iglonline.net

ANNEXURE 1Table 19: Important conversions used in this industryMultiplyByTo obtain

in.25.4Mm

Lbs0.454Kg

Gal3.785L

HP0.746kW

Btu1055J

Deg F0.556 (f-32)Deg C

Psi0.0703kg/cm2

6.895Kpa

0.069Bar

Cfm0.0283m3/min

GPM3.785L/min

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