4 replies to this topic

[mohammad reza]

Dear All

1. What is the reason of consideration "Compressor Anti Surge Control Valve" on anti surge line with out any block valve?

2. It is any difference between Depressurizing of Reciprocating & centrifugal compressor?

3. Is it necessary to consider design pressure of suction drum in reciprocation compressor equal to settle-out pressure of compressor same as Centrifugal compressor?


Regards

[djack77494]

Mohammad,
I will venture into your queries mainly because it appears no one else is. I have some experience with centrifugals, but very little with reciprocating compressors. For a centrifugal, the anti-surge system is a key component of the overall control. Centrifugals can rapid sustain severe damage if allowed to go into surge, so that must be avoided. It is a phenomenum that develops very quickly, so your control system must be designed accordingly.

Regarding Question #1) I see no reason for a block valve in the anti-surge line since it must be functional at all times when the compressor is operating.
Question #2) I do not understand your question. Recips, by their very nature, have essentially check or non return valves built in, and so backflow is impeded. This is not generally the case for centrifugals.
Question #3) Despite my answer to question #2, I would still assume backflow could occur and would design a recip suction drum for settle out pressure. (But remember my 2nd sentence)
Doug

[mohammad reza]

Doug

I see in another project, for Recip. compressor suction drum design pressure lower than settle-out pressure. But I have doubt is it correct or not.

Anti surge control valve failing position, shall be Fail open always. Is it correct?

Mohammad Reza

[Nikhil Kulkarni]

Doug

I see in another project, for Recip. compressor suction drum design pressure lower than settle-out pressure. But I have doubt is it correct or not.

Anti surge control valve failing position, shall be Fail open always. Is it correct?

Mohammad Reza

Dear Reza,

As per my information, anti surge control valve failing position is always failed-open.

[JoeWong]

Mohammad,

Doug has given you basically most (if not all) of the response. I chime in to provide my minor opinions.

Requirement of block valves on inlet and outlet of Anti-surge control valve may subject to cost of the valves, cost for blowdown during valve maintenance and valve & compressor maintenance frequency. Normally the valve inspection & maintenance could be conducted together with compressor maintenance. Thus there is no point to provide the block valves at the inlet and outlet of the valve. This may not always the case...

It is subject to type of compressor, whether you have full flow recylce for reciprocating compressor case, if you will blowdown the compressor for every shutdown, potential of liquid condensation in the compressor after shutdown, can the compressor bearing allow liquid condensation, etc...It is very case dependent.

Without detail informations available, i guess it is hard to answer you question.