"My company uses rotary screw gas (methane) compressors with an oil pressure of about 150 psig. It's difficult to keep the water out of the oil and therefore out of the rotors. Currently we manually drain off about 1-2 gallons of water per day. Do you have any advice, or any products, that could help us?"
This must be a wet (flooded) screw and I assume that you are compressing raw field (unprocessed) methane (natural gas). The water is likely entering the compressor with the inlet gas. You should consider a properly sized dehydration system (scrubber with mist pads or coalescing filter) on the gas inlet to remove as much water as possible before it reaches the compressor.
If you already are properly treating the inlet gas, then possibly the discharge temperature of the compressor gas is too low. It should be kept at least 10 degrees F above the dew point of the gas mixture or as high as possible by controlling the oil supply temperature and the oil flow to the rotor to minimize cooling of the gas. The oil will not oxidize at these higher temperatures because it is not an oxidative environment.
I also assume that you are using a mineral oil and thus getting the water separation, which is good. Water, either free or dissolved, in the oil will damage the compressor bearings and the oil itself. Even a PAG or PAO synthetic will separate readily from water above 100F so changing to a PAG or PAO will not solve the problem. Remove the water upstream of the compressor.
Bob Scott, Noria Corporation
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