antisurge for large (2 stage) compressors

[dabdool]

hi everyone,
can anyone explain to me what exactly is antisurge in compressors, what causes it and how does it affect the machine. also how is it controlled, what is this whole issue of antisurge control.

thanks

 

[hacksaw]

Complex subject, but in a nutshell it has to do with maintaining a certain amount of flow through the compressor.

It is at low flows that the flow characteristic of the machine is unstable. It can be a seismic experience if you are on the compressor deck when the machine goes into surge...

Simple systems use flow/diff. pressure to control the recycle valve. More sophisticated systems used a combination of discharge flow, machine d/p, and temperature to detaermine the on-set of surge and adjust the recylce valve accordingly.

 

[SooCS]

Simply an antisurge control system is a control system to prevent the compressor operates outside a certain regime. When a compressor is compressing the gas to a pressure higher than the operating regime, the gas leaks back into the compressor. This leak back into the compressor is so violent that it causes exessive vibration like thunder storm and may even explode.

The other extreme is the stone.