Network Description

 

The Adani Energy Limited formerly known as Gujarat Adani Energy Limited started over the city gas distribution in Ahmedabad, considering the requirements of the city. The main considerations were the following.

·         Since the gas has to be purchased from other sources, the supply chain was to be identified and the location of the suppliers near by the acceptable distance limit, ie. The location at which the AEL receives the gas from the source.

·         The main source for the supply was GSPL(Gujarat State Petroleum Limited).

·         To ensure the continuous supply of gas to the city in the required pressure.

The network designed for the city gas distribution comprises of the following objects,

·         City Gate Station

·         Industrial metering or regulating station.

·         District regulation station(DRS) or Pressure regulating station(PRS).

·         Pipeline networks consisting of the Steel and MDPE.

    City Gate station(CGS)

CGS for the whole network of  is located outside the city.

 The main components of the CGS are

·         Two staged Pressure Reduction System.

·         Slam Shut valves.

·         Filtering unit.

·         Filtering unit is mainly installed to remove the small particles in gas to maintain the gas efficiency of 99.9%.

·         Piping with metering equipments (mainly orifice meters).

The pressure at which the GSPL delivers gas to CGS is in the range of 28-49barg. City gate station reduces the pressure to 26barg through the stepwise pressure reduction system.

The various skids in the City Gate Station includes,

·         Gas filtration skid

·         Pressure reduction skid

·         Flow metering skid

Filtration skid

 

The skid has been designed in such a way as to accept a single stream only. High efficiency filter separators are used for the removal of liquid and solid particles from the incoming gas stream over the entire operating range. The gas outlet from the processing industry is cautiously maintained at free of impurities, the filtration skid ensures the pure gas distributed to the line. The filter is normally designed to withstand a pressure in the range of 30-49 bar.

Pressure Reduction skid.

 

The pressure reduction skid is installed to reduce the pressure of the incoming gas from the source from the range of 30-49barg to 26barg.

Flow metering skid.

 

Flow meters are installed to for a single stream. The normal flow meters used in the CGS is orifice plates. Orifice flow meters finds its use as a large pressure drop is required. The various parameters such as temperature in the various sections of the line, pressure at the inlet and outlet joints, flow inlet and outlet are controlled by the SCADA systems in the control room.

District Regulation Station (DRS)

District Regulation system is a device used to reduce the pressure from 26barg to 4barg. It is the interface between the steel grid network and the medium pressure network. The location of the District Regulation Station mainly depends on the requirements of the area i.e., the type of customers to the company. Example, Group of small industries in an area and areal extent of the domestic area.

The various components in the DRS include the following,

·         Slam shut valves for controlling the flow.

·         Filtering skid

·         Pressure reduction skid

 The main supplier of the DRS equipment to the company is Control Plus, Oil & Gas Solution Pvt Ltd. The inlet to the DRS is from the steel line and the outlet is also the steel line, where it is joined to the PE line using the Steel – PE converter.

Odorizing unit

Odorizing unit is highly essential to ensure the safe distribution of the both CNG and PNG. The odorants mainly include the mercaptans, it can be a single odorant or a mixture of 2 odorants. These odorants are injected in to the natural gas to detect leaks if any. Odorants are selected in such a way the smell of its peculiar and unique and one can identify the leakage easily, it should not alter with any of the physical and chemical properties of the natural gas.

The odorant used is ethyl Mercaptan.

Pipeline Network

The main line is the steel grid network which is the outlet from the City Gate Station. This steel grid network is laid in such a way that it forms a ring around the whole city. The major advantages of maintaining a circular network is

·         To make use of looping to ensure continuous supply of gas throughout.

·         To avoid pressure reduction throughout the length of the pipe.

The laying of the PE pipeline purely depends on the requirements forecast. This primary network of steel line connects CGS to the DRS. The nominal diameters of the steel grid lines are restricted to 12” and 8”. As said earlier, they are laid depending on the load requirement. The secondary lines are the MDPE lines which originate from the steel lines. The largest diameter of the PE line used is 125mm.