Gas supply system in building
This chapter covers the safe use of gases for purposes like fuel, lighting, and medical in buildings.
The uses of gases for fuel and lighting purposes in buildings is becoming more and more common in different parts of the country, and with the advent of new petroleum complexes and piped gas system, community gas supply system in building is bound to become one of the important services like electricity and water supply in buildings.
The use of liquefied petroleum gas supplied in containers and cylinders is already quite popular. On the release of pressure, by opening the valve, they readily convert into the gaseous phase. In this state, they present a hazard comparable to any inflammable natural or manufactured gas, except that being heavier than air, low-level ventilation is necessary to avoid an inflammable concentration of gas.
Similarly, a series of precautions and regulations are necessary for laying of natural gas pipelines from city gas distribution entity to building premises and finally in the use location. Of late, the use of medical gases in hospitals through pipelines has become quite prevalent due to associated advantages, however, this needs to be supplemented with required care and precautions.
A minimum set of safety provisions are, therefore, laid down to safeguard the gas piping installation and the mode of operation in the interest of public safety.
1. Pressure regulation is required to economize the sizing of a piping system where the pressure to gas supplied to the domestic system or other low-pressure gas piping system in buildings is in excess of the pressure to be used in the appliance a gas pressure regulator of suitable specification shall be installed in service pipe of each system to prevent excess pressure reaching the appliance. The pressure regulators to be used can be from 400 kN/m² upstream pressure to 2.1 kN/m2 for domestic consumers and 10 kN/m², 30 kN/m? 200 kN/ m² for commercial consumers as the case may be.
2. If located inside a building, the required regulator shall comply with the following.
(a) If any of the diaphragms of the regulator rupture, the gas shall be sent to an outlet vent pipe made of brass or plastic in order to ventilate or drain the gas out of the building. The vent pipe will, however, lead to outer air about 1 m above the topmost story of the building.
(b) If the gas pressure at the outlet of the regulator falls below 50 % of the operating gas pressure or rises above twice the operating gas pressure, the gas input to the pressure regulator shall be cut off.
(c) In the event of malfunctioning of this safety device, a supplementary device shall connect the low-pressure circuit to the outlet circuit (Vent pipe) as soon as the exit pressure reaches 7 kN/m².
3. It shall also be ensured by the supply authority that the calorific value and supply pressure of gas shall not exceed the values for the type of gas used.
GAS SUPPLY SYSTEM SERVICE SHUTOFF VALVES
1. Service shut-off valves shall be provided on all new services including replacements and shall be installed in a readily accessible location.
2. Service shut-off valves shall be located upstream of the meter if there is no regulator or upstream of the regulator if there is one.
3. All gas services installation operating at a pressure greater than 7 kN/m2 shall be equipped and with a shut-off valve of the approved type installed on the service pipe outside the building.
4. Underground shut-off valves shall be located in a covered durable kerb box, manhole, vault, or standpipe which is designed to permit ready operation of the valve. The covers so provided shall be clearly marked “GAS'”.
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Nothing herein shall prohibit the continued use of an existing gas piping system without further inspection or test unless the authority has reason to believe that defects which make the system dangerous to life or property exist.
RULES FOR TURNING GAS ON GAS SUPPLY SYSTEM
1. No person, unless is an employee of the gas supply system company or having permission from the gas company, shall turn on the gas at a service shut-off valve or at any that controls the supply of gas to more than one consumer.
2. Gas shall not be turned on at any meter valve without specific permission from the gas company or the authority if any of the following condition exists.
(a) If the gas piping, appliances, or meter supply through the meter valve are known to leak or otherwise be defective.
(b) If required inspection of the piping or appliance has not been made.
(c) If the gas supply company or the authority has requested that the gas be left turned off.
(d) If the meter valve is found shut off for some reason not known to the gas fitter.
3. The gas shall not be turned on in the event of a fire.
4. Gas shall not be turned on at any branch line valve if any of the conditions listed in point No.2 above are found. Where a branch line valve is found closed, a gas fitter shall again turn the gas on at such valve only. It proper precautions to prevent leakage are taken and no other unsafe conditions are created thereby.
5. Gas shall not be turned on at either the meter valve on the service line unless all gas keys/cocks or valves installed on all outlets in the piping system are closed or all outlets in the piping system are capped or plugged.
RULES FOR SHUTTING OFF THE GAS
1. The gas fitter shall put the gas off to any appliance, pipe or piping system and shall leave the gas turned off until the causes for interrupting the supply has been removed in any one of the following cases.
(a) If ordered to do so by the authority.
(b) If leakage of gas is noted, which appears to be sufficient to cause fire, explosion or asphyxiation.
(c) If an installation of some gas appliance in found to be such as to cause a serious hazard to persons or property.
(d) If any condition exists which threatens interruption of gas supply which may cause burner outage or otherwise prove dangerous.
2. It shall be the duty of the installing agency when the gas supply is to be turned off to notify all affected consumers.
3. Before turning off the gas at the meter, for the purpose of installation, repair replacement or maintenance of piping or appliance, all burner and pilot valves on the premises supplied with gas through the meter shall be turned off and the meter test hand observed for a sufficient length of time to ascertain that there is no gas passing through the meter.
INSTALLATION OF GAS PIPES
1. Installation, repair, and replacement of gas piping or appliances shall be performed only by a qualified installing agency.
2. Piping shall be of wrought iron, steel, copper, stainless steel or cast iron when the gas pressure is less than 7kN/m2, with higher gas pressure use of cast iron shall be prohibited.
3. SS316/304/321 and flexible PE coated flexible pipe in roll shall be permitted in the low-pressure system provided the pipe meets the required standard, to avoid the bends, fittings, and leakage from the joint which are potential leakage points.
4. Heavy rubber flexible tube shall be permitted only as a direct connection to the burner from the appliance valve.
5. The size to gas piping depends upon the size following factors :
(a) Allowable loss in pressure from the meter or service regulator, when a meter is not provided, to the appliance.
(b) Maximum consumption to be provided.
(c) Length of piping and number of fittings.
(d) Specific gravity of the gas.
6. No gas pipe smaller than 8 mm shall be used.
7. As far as possible, straight lengths of pipe should be used. Where there are bends in the pipeline, these should have a radius of at leas five times the diameter of the pipe.
8. Piping shall be painted silver grey with a red band of 150 mm width.
9. The gas pipeline shall be painted canary yellow in case of natural gas.
10. Piping shall be buried to a minimum depth of 1m.
11. Pipe should not be in contact with the wall to ensure that no corrosion takes place.
12. Single pipe without joint shall be used for wall crossing
13. Gas pipe shall not be bent. Fittings shall be used when making turms in gas pipe.
14. Drip has to be provided in the case of gas consisting of moisture content,
15. No device shall be placed inside the gas piping or fittings that will reduce the cross-sectional area or otherwise obstruct the free flow of gas.
16. The distance between gas piping and electrical wiring system shall be at least 60 mm,
17. Meters shall be installed in such a way that there shall be no load transfer from the pipe line to the inlet/outlet of the meter and shall be easily accessible.
18. Piping installation shall be thoroughly gaslight
19. Smoking shall not be permitted when working on piping which contains or has contaminated gas.
20. The gas piping should run above the electrical wiring In this type of installation in the event of any leakage of natural gas, the gas would move up (natural gas being lighter than air) and would not come directly in contact with the electrical wiring.
USE OF PIPED NATURAL GAS (PNG)
1. The PNG infrastructure shall be in complete compliance with all the requirements of Petroleum and Natural Gas Regulatory Board (Technical standards and specifications including safety standards for city or Local Natural Gas Distribution Network) Regulations, 2008.
2. The user-group/housing society concerned (referred here in after in these clauses as ‘society should contact the local City Gas Distribution (CGD) entity at the stage of the design of the building. This ensures that all the adequate provisions are incorporated in the design itself, as also the compliance with all the safety standards stipulated required by the regulations/gas entities, as applicable from time-to-time. This ensures avoidance/mitigation of any rework at a later stage or even situations where in the corporation of any changes may become impractical or not possible, thereby rendering the building devoid of PNG infrastructure.
3. The entire gas pipeline infrastructure proposed to be laid in the premises of the society shall be easily |accessible in the future by the representatives of the CGD entity. Provision shall be made by the builder for the same.
4. Builder/society should ensure communication of the same to the future customer and should incorporate it in their agreements with the customer.
5. No permanent/temporary structure shall be erected on the ground along the paths where gas pipe line exists underground.
6. The PNG infrastructure inside the premises of societies primarily comprises the following
(a) Underground medium pressure (MP) pipe line networks, comprising mainly polyethylene (PE) pipes and fittings.
(b) Underground low pressure (LP)pipe line networks, comprising mainly polyethylene (PE) pipes and fittings.
(c) Service regulator modules,
(d) Above ground riser and lateral system, comprising mainly ERW GI pipes and fittings.
(e) Pipe line inside premise and/or kitchen of the individual customer, comprising various components like meter regulator, diaphragm gas meter, copper pipc, brass fittings, brass valves, etc.
GUIDELINES FOR MP AND LP PIPELINE NETWORKS
1. Gas pipe lines are required to be laid at a minimum top cover of 1 m from the finished surface level. Under PE pile line shall not be laid through the basement.
2. A minimum clearance of at least 300 mm is required to be maintained between the gas pipe lines and any other obstacles/services.
3. Gas pipe lines should be laid closer to properties than as stipulated below in Table.
4. If required provision underground ducts may be provided by the society within their premises at the time of construction of the building, to facilitate inserting of gas pipelines at a later stage. The duct through which the gas pipeline is to be laid should not be shared with pipeline of any other utility, for safety reasons.
5. The ducts/sleeves should be 150 mm of PVC. The top cover of the sleeve should be at least 1m below finish ground level.
6. Service chambers should be provided at 15 m to 20 m center-to-center (in case of straight sections) and also at bends, tecs, and before and after slope.
7. Size of the service chamber shall be 1.0x 0.6m (inside dimensions) and top of the cover of the duct should be at least 1.0 m high.
8. The ducts for the gas pipe line should be maintained at an offset distance of at least 1.0 m from electrical services. and 1.5 m from any other structure. Crossing with other utilities/services should be a difference in the level of at least 300 mm.
9. During the period between the laying of ducts and insertion of the gas pipeline, all the ends/entries of the ducts laid shall be temporarily closed to avoid the entry of mud, debris, rodents, etc, inside the ducts.
10. After the insertion of the gas pipe line through ducts, the annular space between the duct and the gas pipe at the ends should be plugged using an RCC half-round pieces and plastered with cement.
GUIDELINES FOR SERVICE REGULATOR MODULES
The user-group/society should provide adequate open spaces in the premises for the installation of gas equipment like regulating stations, which will be required to facilitate the supply of PNG to the residents of the building/premise.
2. The identified location shall be such that it does not obstruct any vehicular movement and is at a safe location in the premises.
GUIDELINES FOR ABOVE GROUND RISER AND LATERAL SYSTEM
1. The riser and lateral system supplying gas to multi-storeyed residential buildings shall be in compliance with the requirements of the PNGRB regulations.
2. multi-occupancy buildings having eight floors or more should have purpose-built utility shafts/ducts for accommodating riser and lateral system, which should be the preferred route for constructing/locating the riser.
3. Provision shall be made for safe access to the riser and lateral system by the representatives of the CGD
entity for future maintenance and repair.
4. Adequate provision for natural ventilation shall be provided in the building where PNG infrastructure is laid, so as to prevent any potential gas leaks for accumulating in the atmosphere to an unsafe level.
5. The minimum levels of ventilation in risers ducts/shafts shall be as given below:
6. Where the duct has a single ventilator that is part of the architectural designer near me of the building, the free area of the ventilator to the outside area shall be a minimum of 0.04 m? or 4% of CSAofthe duct, whichever is greatest
7. Pipe work shall be installed in an unventilated void.
8. Any duct containing a riser or lateral shall be ventilated either directly to outside air, or indirectly to the outside air.
9. The provision of ventilation should be via permanent ventilators within the area/duct containing pipe-work.
10. All flammable release sources shall be at a lower elevation than the bottom of the highest ventilation opening.
11. Pipes may run in the same duct as most other services, including hot and cold water services, heating pipe, electrical conduits and cables, and pipes containing other fuels.
12. There shall be provision for installing risers and laterals such that a minimum distance of 300 mm.
GUIDELINES FOR PIPELINE INSIDE PREMISE AND/OR KITCHEN OF INDIVIDUAL CUSTOMER
1. Kitchen is the preferred room to locate the meter.
2. The gas meter shall be installed in an area with adequate ventilation and at a proper location to facilitate safe and convenient meter reading and maintenance activities in the future.
3. A minimum ventilation area of 2% of the internal floor area of the room shall be provided in the room where the gas meter is located.
4. The gas pipeline inside the kitchen shall be laid along the walls of the kitchen and in a ventilated area.
5. In case pipe work is required to be laid in solid floors inside the kitchen, adequate provisions shall be provided to protect the pipeline against corrosion and failure caused by movement.
6. Provision of preformed ducts with protective covers should be made to facilitate the laying of the gas pipeline.
7. It is advisable to contact and CGD entity at the designing stage so that adequate provisions are incorporated in the design of the kitchen/floor plan to faciliate easy well safe installation of the PNG system.
8. Installation pipe work shall be placed within the cavity of a cavity wall.
9. In case of provision of a sleeve, the same should be of a diameter that provides a sliding fit to the pipe allowing normal pipe expansion/contraction
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