# Reduced efficiency and Instability in Centrifugal Compressor



## Zain Ali Shah (5 mo ago)

Hi,

We have Atlas Copco Centrifugal Compressor HMH7-2.45-267 installed with rated capacity of 10 T/hr and 23 bar max pressure. During initial 5-6 years the compressors response was fine, but after several years it has been surging continuously. During Surge condition compressor anti surge system works fine, but eventually results energy and production loss. So can anyone recommend what could be the possible reason behind this, maybe we can improve our compressor control system or change the P & I values of the BOV or IGV for fast action of the control system.


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## iowagold (Jan 22, 2020)

so how many cfm do you need? at the 333 psi? (23 bar)
pretty high pressure..
what is the application or industry?


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## MacMcMacmac (9 mo ago)

If nothing has changed in your process, I would suspect a faulty pressure transducer sending inaccurate data to the surge controller. Your PID setting should not need to be changed unless something has physically changed in the machine or process. Is there any abrasive qualities to the process gas? Corrosive? Wet? Is there the possibility of debris build up on any of the rotors? Erosion of the rotors? Are there any inlet filters that may be fouling and reducing inlet flow? Has inlet pressure fallen? Have there been any piping modifications? Might there be a failing valve downstream of the compressor? Might there be buildup of debris in the outlet piping or the vessel into which it is discharging? Might there be build up inside the intercoolers causing back pressure rise between stages? Is the inlet temperature or temperature between stages getting too high? Something is preventing the compressor from overcoming the back pressure in the system, so either the pressure is too high, the process condition feedback is inaccurate or there is insufficient flow.

I ran one centrifugal which was unusually sensitive to moisture in the air. We have two 2500hp HM-7s at work and they have been very reliable for 20 years now.


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## iowagold (Jan 22, 2020)

have your vibration techs take a few readings.
that helps in diagnostics.
do you have lab view for the motor drive control?


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