Check Valve downstream Anti Surge Valve

[HamzaNossair]

Hello Everyone,

I have a simple issue, does any one know the reason of installing a check valve downstream the Anit Surge valve?

One of our vendors is eleminating that valve thinks that it will cause chock, while after we started that Wet Gas Compressor, we faced some high spill back to the Compressor?
Is that eleminated check valve is the reason?

 

[pmover]

not sure what is meant by "chock".

not sure of the exact location of check valve . . . anti-surge piping or compressor discharge piping?

a check valve is typically installed in compressor discharge piping, downstream of the branch connection to anti-surge valve, to prevent a reverse flow condition through the gas compressor. any/all possibility of reversing gas flow through a compressor should be eliminated. the compressor bearings loads and any labyrinth seals are designed for a specific rotation and load (thrust bearings). changing that rotation may very well be catastrophic to the compressor components.

additionally, if compressor is in parallel with other compressors, not having the check valve may be difficult to bring the compressor online.

if the proposal is to install the check valve on the anti-surge piping, i'm not aware of any purpose.

hope this helps.
-pmover

 

[HamzaNossair]

Thank you...
Ya, my basic question is regarding a check valve typicaly installed after the Anti Surge valve within the recycle line, any purpose?

 

[BigInch]

I wouldn't think it is necessary. Not that I have tremendous experience with compressor stations, but I have done a few and I don't ever recall seeing a check in the antisurge line. They are always in the downstream connecting piping. I would suspect your backspill was from a downstream upset and perhaps not having your check valve there, you had no protection from that downstream segment either.

From "BigInch's Extremely simple theory of everything."

 

[jbattershell]

I have never put a check valve downstream of a recycle valve in 25 years of designing centrifugal compressors. it is not needed.

if you want to provide more detail on the actual arrangement of piping and the process, maybe there something strange with your installation than can be assumed from the very scarce amount of detail provided.

good luck

 

[MortenA]

A chack valve down stream the recycle line seem like a good idear to me. Theres a higher pressure downstream, you start the compressor agains no head and ramp it up over the recycle valve (in manual) and then once the compressor is up and running you close the recycle valve slowly, once the pressure is high enogh the check valve will open and flow (to next stage, export whatever) will commence.

WRT chock - i expect the worry is that when the compressor trips pressure will drop rapidly and the check valve will slam slut, thus breaking the valve. This is a real concern and indeed check valves in gas service often fails.

Best regrads

Morten

 

[BigInch]

or ... check valve parts in the compressor?

From "BigInch's Extremely simple theory of everything."

 

[jbattershell]

MortenA, what you are describing is a discharge check valve. And you are correct, that check valve is needed and has always been installed in the final discharge line from a centrifugal compressor.

however, the literal meaning of "check valve downstream of the recycle valve" means to me, installation of a check valve directly downstream of the recycle valve, which would be in the same piping as the recycle valve and this is not where a check valve should be installed.

the original poster might have been trying to describe the discharge check valve which is installed in the piping coming from the compressor. prior to this check valve in the discharge piping, is a tee to which the recycle line is connected. in that recycle line, a recycle valve is installed and the gas is directed back to the inlet. That line is called the recycle piping line. Down stream of this tee, is where the discharge check valve is installed.

if you eliminate this valve, there can be serious problems. the most serious is spinning the compressor backwards after a shut down. stored gas pressure downstream will be allowed to turbine the compressor backwards if the check valve is removed. this can destroy a compressor and cause a catastrophic crash of the machine. if the person thought that the check valve was causing some excess pressure drop (choke as described), then it is necessary to actually measure the pressure drop. most check valves installed will have less than 1 psi of pressure drop which is not very much.

 

[MortenA]

Cant say that i remember having seen a check valve in the recycle line itself (up or downstream the valve. Bit of a contradiction really. Since theres a risk associated to the check valve i wouldnt recommend it - and im not that happy about the one in the main line either although they do have advantages.

So theres some confusion wr to the desription given by the original poser - does he mean downstream the recycle line branch (on the main line) or does he mean downstream the valve itself on the recycle line.

Best regrads

Morten

 

[BigInch]

I believe he meant in the same pipe holding the surge valve.

From "BigInch's Extremely simple theory of everything."

 

[HamzaNossair]

Correct!
I meant a check valve on the Recycle line it selft, in series with the ASV

 

[jbattershell]

then you should remove that check valve. it is not needed. the recycle line should only contain the recycle valve and in many cases, a diffuser or silencer to reduce the noise level of the valve during operation. the requirement of the silencer is usually dictated by the vendor supplying the valve.