Compressor, and discharge PSV capacity
Compressor, and discharge PSV capacity
(OP)
I have to size the PSV on discharge of recip-compressor for blocked outlet case.
I believe, it should be sized for 110% of comp. rated capacity, as the segment has to be protected with margin, when compressor is running at it's rated capacity.
Others feel it should be at rated capacity only.
I feel the compressor is definitely capable of reaching it's rated capacity and can deliver little bit more...
Thank you, in advance for spending time on this and I look forward to your advice..
Regards,
SAA
PS:
Please comment on the rated capacity and whether compressor can deliver little bit more..
I believe, it should be sized for 110% of comp. rated capacity, as the segment has to be protected with margin, when compressor is running at it's rated capacity.
Others feel it should be at rated capacity only.
I feel the compressor is definitely capable of reaching it's rated capacity and can deliver little bit more...
Thank you, in advance for spending time on this and I look forward to your advice..
Regards,
SAA
PS:
Please comment on the rated capacity and whether compressor can deliver little bit more..





RE: Compressor, and discharge PSV capacity
Regards,
RE: Compressor, and discharge PSV capacity
The compressor is a recycle gas compressor, containing ~76% hydrogen. Mole. wt. can be varying...
I feel, it can go up by 1-2% above rated compressor, as compressor vendor will, no matter how small, will have his safety margin with regards to rated capacity.
What do you feel?
Regards,
SAA
RE: Compressor, and discharge PSV capacity
Check the rated capacity of the PSV you select, it may also already have the 10% you required.
RE: Compressor, and discharge PSV capacity
Yes, I would want some margin to account for changes in MW or other process conditions but I'm not sure I would arbitraily use 10% on top of the compressor rated capacity.
RE: Compressor, and discharge PSV capacity
You didn't mention to where the relief valve would discharge.
Just so there is no misunderstanding, it's not back to suction is it?
RE: Compressor, and discharge PSV capacity
RE: Compressor, and discharge PSV capacity
As far as compressor rating is concerned, actually it is always less at site than what is being suggested by the manufacturer.
If you still feel insecure, the required redundancy in capacity should be the percentage change in density.
I vote for TD2K anyhow.
Regards,
RE: Compressor, and discharge PSV capacity
I don't know what your system looks like, but are you protecting equipment or just piping? The allowable overpressure is different if you are just protecting piping, typically 10% for equipment and 33% for piping. The cylinders themselves are usually rated for much more that anything downstream.
RE: Compressor, and discharge PSV capacity
Assuming that there are no differences in the suction conditions for the manufacturer's rated capacity at design conditions and at relief conditions, wouldn't the capacity of the compressor at relief conditions (higher discharge pressure) actually be lower than at design conditions? It would then seem appropriate to just use the rated capacity at design conditions without a percentage increase.
RE: Compressor, and discharge PSV capacity
Best Regards,
Satish