We are running two Howden 504's in our refrigerant plant. We have been having issues with our lube oil backing up into the suction scrubber on the skid. So far, we have not been able to pinpoint how the oil is getting in there, but there are only a couple of possible ways. Right now, the thoughts are that it is backing up the suction line of the compressor and dumping in that way, just not sure how or why. The suction line is a 16" line and it comes down off the top of the suction scrubber aprox 5' high, so it would have to back all the way up that and into the scrubber. Just this past week we have emptied aprox 90 gallons from one unit, and 40 from the other. All units share a common suction header before it goes into the scrubber, including a smaller unit 204 which at this time we are not having this issue, so I don’t think its coming in that way. Is anyone running this similar setup, or have any input.

Basic rundown of process. Propane vapor enter into the suction side of the compressor through a common suction header then into suction scrubber so as not to introduce liquid propane into the compressor. Propane is mixed with lube oil within the unit, compressed then discharged into an oil separator where the oil is dropped out through coalescent filters. The compressed propane is the discharge into a common header then run through condenser fans. Suction pressures on are maintained at roughly 2psi using the slide valve. Discharge pressures run in the mid 140psi range. We also have a side stream into the compressor through what we call an economizer loup.