City Gas Distribution: A Network Analysis

Overall view

City gas distribution in India Oil India ltd. was first to start distribution gas in Assam in 1960’s. As a pilot project first city gas distribution was taken up with help of ONGC at Vadodara city in 1972. GGCL was the first commercial city gas distributon company in India. MGL & IGL starts city gas distribution in domestic, commercial & transport sector in Mumbai(1995) & Delhi(1998) respectively.

Natural Gas Why Natural gas? Advantages: Safe and clean fuel. Excellent combustion properties. Cheap and easily available. Future fuel.

Demand of Natural Gas Domestic gas demand in India is of order of 179MMSCMD in 2006-07.

Consumption of Natural gas

Feasibility

System design Selection of route. Optimum route. System basic concept

Selection of route Maximum reach of potential demand centers with minimum length. Use of existing defined pipeline corridors by respective authorities. Minimum disturbance to agricultural land. Safety of people and property. Avoidance of rocky terrain. Flexibility of future expansion.

Optimum route Shortest length of pipeline grid. Least topographical variation and minimum obstacles. Minimum cost of system layout. Density of traffic should be low. Minimum no. of turning points.

System basic concept Pressure levels Medium pressure (26 barg) Low pressure (4 barg) High pressure (49 barg)

Network Steel mains (network) High pressure mains Medium pressure mains Above ground mains Polyethylene Cover clearance protection Sectionalizing

Construction activities Opening of Right of Way Clearing & grading Welding & radiography Joint coating Crossings Hydrostatic testing

Sectors for city gas distribution CNG – Transport sector PNG – Domestic sector PNG – Commercial sector PNG – Industrial sector

Various station involved in network City gate station (CGS) Industrial pressure reducing station (IPRS) District regulating station (DRS)

Layout of service connection Mild density polyethylene (MDPE) as gas pipe. Domestic connection layout

MDPE as gas pipe Balance rigidity & toughness Excellent ductility Very low permeation to gas Resistance to rapid crack Extremely smoother interior surface Easy to transport, handle & lay Longer life

Domestic connection layout

Polyethylene Pipe Joining An integral part of any pipe system is the method used to join the system components. Thermal heat fusion method 1. Butt fusion 2. Saddle/conventional fusion 3. Socket fusion Electro fusion

Thermal Heat Fusion Principle of heat fusion is to heat two surfaces to a designated temperature and then fuse them together by application of sufficient force. Jjjjjj Kkkkkkkkkkkkkk Kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk

Butt fusion Most widely used method of joining. It produces permanent, economical and flow efficient connection.

Saddle/conventional fusion This is used to join a saddle to a pipe. The external surface of both the pipe is heated and the matching surface are fitted with the help of concave and convex shaped heating tools.

Socket Fusion In this technique, both the internal as well as the external surface is heated.

Electro Fusion

Maintenance Pipeline failure investigation Periodic surveillance of pipelines Cathodic protection.

Future advancement Details of Non returning valve & metering device used in door to door supply of PNG. Fabrication of NRV Electric log model of city gas distribution Details of horizontal directional drilling & auger boring. Flow rate calculation of particular sections of a pipeline.