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We have an issue with our RG compressor in hydroprocessing unit. The flow of the RG compressor (Reciprocating single stage) decreased all of a sudden while taking scheduled changeover of the RG compressor. Flow went from 22000 Nm3/hr to 17000 Nm3/hr. We thought it may be due to some problem with the compressor that we took changeover so after a while again C/O was taken and the previously running compressor was taken in line but the result was same.
The other process parameters are same like the HP separator pressure and temp remains same. the power consumption of the compressor got decreased from 125 KWH to ~85 KWH.
We have checked the spillback valve of the compressors and cleaned the strainer of the compressor but no results obtained.
MUG compressor flow remains same and the MUG discharge is in the Fin Fan outlet to HP separator. The purity of the RG remains same. And one thing to be noted is that the D/C pressure didn't change, the S/c pressure got inc by 1-1.5 KSC at the time of C/o but now its normal.
The RG suction drum is common for the both compressors. It was noted that for past few weeks the suction drum level got inc and draining was done a bit frequently, so could carry over of the Hcbn liq to the compressor cause this reduction in flow?. The one imp thing to be noted is that both the compressors are not developing the flow. the flow has got dec to 17000 nm3/hr and is constant at this value, no further reduction is there, it has been a week since the event.
(suction valve plate should be OK as the s/c temp is not inc) Pls give your valuable suggestions.

Additional:
Thank you Mr. Rupesh for your valuable time and comment. Actually we have checked the unloaded valves after taking the compressor for a maintenance and checked it at site (operational wise) but the working was found normal. Actually after doing a thorough study we have come to an conclusion (as of now) we found out that there is a increased liquid carry over to the compressor. We have checked the strainer in short durations. And the possible cause could be some internal integrity damage at RG suction drum or High pressure separator (suction point of comp). So this activity of integrity check could be done only in available shutdown activity. As the gas to oil ratio is less than earlier but not low at alarming level, management took the decision of waiting till planned shutdown. P.s: I will update you once the activity is being done.
 
Answers
27/03/2017 A: Rupesh Patel, Saudi Aramco Total Refining and Petrochemical Company, rupeshgpatel@gmail.com
May be compressor valve plate checked due to salt deposit.check functionality of valve plates which are installed on suction cylinders.
Many times we see it happen and found that one of suction loader not working in recip compressor.
27/03/2017 A: Rupesh Patel, Saudi Aramco Total Refining and Petrochemical Company, rupeshgpatel@gmail.com
Maybe compressor valve plate checked due to salt deposit.check functionality of valve plates which are installed on suction cylinders.
Many we it happen and found that one of suction loader not working in recip compressor.