5 replies to this topic

[Sonu Kumar Balaraman]

& A > Question Details
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.

[Bobby Strain]

It might help if you tell us how many cylinders you have on each machine. And any unloaders or clearance pockets and whether they are manual or pneumatic, automatic, etc. If both machines use the same power of 85 vs 125 KW at the lower flow, then it's likely you have unloaded the cylinders in some manner. If there were recycle flow, you would see greater power.

 

Please explain in English "the S/c pressure got inc by 1-1.5 KSC at the time of C/o but now its normal." Please refrain from using abbreviations because we don't necessarily understand what they mean. You might begin by editing your query for some clarity. I presume you have estimated power based on current draw. And that the speed has not changed.

 

Bobby

[Sonu Kumar Balaraman]

Sir thanks for commenting. Actually our compressor is single stage having two cylinders with unloader 0-50 & 50-100%. The unloader is finger type.

And for the abbreviation - "the Suction pressure got inc by 1-1.5 Kg/cm2 at the time of Changeover but now its normal."

Sir the peculiar thing is that both the compressors are having the same issue that is the drop in flow and discharge pressure of compressor. (Operation philosophy is one in running condition and other stand by)

[Bobby Strain]

The capacity decrease you experience is about what you would expect if one end of one cylinder is unloaded. So go check the actual position of all the unloaders on each cylinder. You should provide complete information for before and after, including all temperatures and pressures.

 

Bobby

[Sonu Kumar Balaraman]

Before the change conditions: suction pressure 64 to 66 kg/cm2, discharge pressure 74 to 75 kg/cm2, suction and discharge temperature 40 & 70℃ respectively, power consumption 125 kWh discharge Flow ~22000 Nm3/hr

After conditions: Suction pressure 64 to 66 kg/cm2, discharge pressure 70 to 71 kg/cm2 the temperatures are same no major change, power consumption is 85 kWh and flow is 17000 Nm3/he, molecular weight and purity of recycle gas has not changed.

All this change happened at the moment when compressor change over was taken so I think it could be due to some mechanical part but sir both the compressors are having the same issue.. Then how could some mechanical part failure happened in both compressors at same time.
And I suspect there could be a bit of liquid carryover to compressor as we got some liquid (hydrocarbon) while cleaning the strainer. Pls give your valuable comments sir

[Sonu Kumar Balaraman]

Before the change conditions: suction pressure 64 to 66 kg/cm2, discharge pressure 74 to 75 kg/cm2, suction and discharge temperature 40 & 70℃ respectively, power consumption 125 kWh discharge Flow ~22000 Nm3/hr

After conditions: Suction pressure 64 to 66 kg/cm2, discharge pressure 70 to 71 kg/cm2 the temperatures are same no major change, power consumption is 85 kWh and flow is 17000 Nm3/he, molecular weight and purity of recycle gas has not changed.

All this change happened at the moment when compressor change over was taken so I think it could be due to some mechanical part but sir both the compressors are having the same issue.. Then how could some mechanical part failure happened in both compressors at same time.
And I suspect there could be a bit of liquid carryover to compressor as we got some liquid (hydrocarbon) while cleaning the strainer. Pls give your valuable comments sir