How An Air Oil Separator Works

Mar 14, 2013

Most of the oil is separated by a centrifugal force. The air-oil mixture enters the separator vessel at an angle so most of the oil is pushed outside and drops down into the oil vessel. Usually, there is a splash plate installed that prevents the air-oil mixture from hitting the separator filter directly, 85% of the oil is separated this way. The remaining 15% exists the compressed air as small droplets and mist. As this oily compressed air flows through the separator filter, the small droplets combine and form large drops until they fall and collect at the bottom of the separator filter, this oil is then sucked up and removed by the scavenge line.

Basic checks when you have oil carryover problems and suspect it is the oil separator

Should there be a lot of oil inside the oil separator, then the scavenge line is faulty.

Should the oil level at the base of the element be higher than five centimetres this will indicate that the separator is starting to saturate, meaning that the filter media is filling up with oil.

Should the separator feel heavy, looks dark in colour and saturated from the bottom to the top then it is really time to replace the oil separator.

This can only be measured when the compressor is running loaded, the differential pressure can be checked and should not be above 0.2 to 0.3 bar under load.

The above points can only be checked when the oil separator is removed from the separator vessel.