GAS FLOW & GAS TRAINS

Gas flow meters


Gases are compressible and changes volume when placed under pressure, when heated or are cooled. Gas meters can be used with LPG in vapour phase,and also Natural Gas. They measure volume of gas(Vm) in m3/hr. Low and medium pressure diaphragm gas meters may be used up to 1.5bar depending on the model.

Various types of flow meters include diaphragm GM, Diaphragm type pre paid meter ,AMR gas meters, Rotary displacement type FMs, Turbine type FMs, Ultrasonic FMs. ( Raychem ). It is important to select proper regulating system prior to FMs which require real experience in designing such system.


Gas Trains & Monitors


In order to ensure a sufficient degree of safety & reliability of gas supply, gas pressure reducing stations (PRS) are used.

A gas train consists of Filter, Slam-shut off valve, pressure regulator, and safety relief valve & flame arrestor. Filter helps to remove the dust / dirt particles in the gas which may damage the regulator parts. The slam shut off valve normally remains open. In case the outlet pressure of the regulator exceeds the permissible limits, the slam shut off valve senses it through the impulse line & instantly shuts off the supply to the downstream system. The safety relief valve is provided for additional safety. It is to be set at higher pressure than the slam shut off valve pressure so that the safety relief valve will operate only when slam shut off valve fails to operate. The outlet of the safety relief valve is vented well above the roof.

Designing gas trains and selection of every component used in the system at most care need to be taken to ensure total safety and required pressure for end equipment.




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