We have just experienced a step increase of Acid no. of centrifugal CO2 compressor from 0.17 to 0.45. what reasons can be listed and investigated. can any one help. compresor oil console is continuously centrifuged by a centrifuge and Nitrogen sparger is also being used inside the tank to stripp off any gas in oil.

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Originally posted by LOGICLOVER:
We have just experienced a step increase of Acid no. of centrifugal CO2 compressor from 0.17 to 0.45. what reasons can be listed and investigated. can any one help. compresor oil console is continuously centrifuged by a centrifuge and Nitrogen sparger is also being used inside the tank to stripp off any gas in oil.

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Since it is a CO2 compressor, I presume that the compressor oil be based on group III or IV base oils. Here, the important parameter that to be monitored is the oil temperature. As long as the temperaure is controlled and maintained as per the OEM limits, TAN will not increase. In the event the temperaure shoots even for a short period, CO2 tend to react with oil and form weak carbonic acid. You said that nitrogen purging is done to strip of gas but the formation of weak acid takes place before the oil reaches oil tank at high temperaure zone. This is one of the reasons that oil selection for CO2 compressors is to be done very cautiously and follow OEMs guideline. I must point out here that oils for this application should be free from aromatics and sulfur content, this means base oil used for blending compressor oils for this kind of compressor applications are mostly Group III or Group IV.

Kumar
kumartr2@yahoo.com