2 replies to this topic

[Poosticks]

I have noticed that on the main discharge line from a natural gas compressor station there will typically be a discharge valve (for example I am currently looking at a station with a 32" main line valve).

However I always see a by-pass around this valve (in this case a 12" by-pass).

 

Does anyone know why compressor plants have these much smaller bypass valves?

 

Thanks for any help

[Bobby Strain]

Maybe you can show us a P&ID. That might help. Be sure to include any controls and check valves.

 

Bobby

[ankur2061]

Poosticks,

 

Smaller by-pass valves are for start-up purpose. During start-up the upstream pressure is very high where the downstream pressure is close to atmospheric (high differential pressure). In case you open the bigger mainline valve the large flow of gas from a high pressure to low pressure zone will create a hydraulic shock in the downstream pipeline system.

 

The smaller by-pass valve is opened during start-up and this ensures that hydraulic shock in the downstream piping is minimized or eliminated.

 

Once the smaller amount of flow through by-pass valve is stabilized the mainline bigger valve can be opened without any concerns of hydraulic shock to the downstream piping. Subsequent to the mainline valve being fully open, the bypass valve can be closed.

 

Regards,

Ankur