Centrifugal compr operated with anti-surge valve on 30% open position

[mucour]

Hello,

Please can you share with me the potential danger (or otherwise) of operating a centrifugal compressor plant with the anti-surge valve control system deactivated but running with the anti-surge valve opened permanently at 30% open position.

We have a situation in our plant (3 stage/section compressor station) where the station/plant overall recycle valve is damaged. The lead time for valve replacement is upto 8 months. There is pressure from management to operate the plant so it was decided by the operators to run the plant without the station recycle valve. An attempt was made to start the plant without the station recycle valve, but the field gas supply was too low and as a result could not run as it always shutdown on low suction pressure on one of the stages. The total gas available in the field is about 80% of the volume required to prevent the gas from operating at the surge control line. The operator then deactivated the anti-surge valve controls and through manual mode set it at 30% open position. The compressor was then started, it now runs and on load.

I have concerns with this kind of opeating mode used by the operators. My concern is that the anti-surge valve cannot respond automatically and fast in a condition whereby there is a loss in gas suction pressure/flow. Another concern is that when the plant experiences shutdown, the anti-surge valve will not be able to respond and open fully to divert 100% recycle of gas back to suction.

Are these concerns credible? What other problems can we face. Otherwise, is it acceptable to run on this mode even if temporarily for some few months.

Please your kind tips will be appreciated.

Thanks.

 

[dcasto]

I wouldn't go long, if at all without and antisurge valve. I'd find a replacement valve at so cost even multiples of the low bid long time repair quote. An antisurge valve is a common valve.

 

[mucour]

dcasto, thanks. I guess it is always a challenge dealing with operations department who want production at all cost. Engineering always battle with their short-cut measures.

I will make effort to escalate this issue to management so that operations can heed to our advice. Thanks again.

 

[dcasto]

Mucour, thats why the better operations people servered time in design and the better desin engineers some time in operations.

I'd rather have a $10,000 antisurge than none and I don't see where you can get ahead with a $100,000 surge system (unless the expensive one can save that amou nt in fuel over 4 years).