The ASTM D-892 Foam Test for Determining the Foaming Characteristics of Compressor Oil

Air compressors are unique in that they ingest large amounts of air for compression that then comes into direct contact with the operating oil.  It is this extreme aeration that requires air compressor oil to be formulated with special additives to inhibit foaming.  Without the proper oil and additives, the aeration would create large amounts of foam throughout the oil system, especially in the separator filter.  The end result is a loss of proper lubrication and then mechanical breakdown, usually due to the failure of the air end bearings.  Failure of these bearings will bring about the loss of the air end itself.

This foaming can be measured by the ASTM D892, which determines the foam tendency of the oil at specific temperatures.  A specific amount of oil is blown with air at a set temperature for five minutes.  The resulting foam is measured after this five minutes of air blowing, then again after 10 minutes.  Quality petroleum and synthetic compressor oil should be able to withstand the aeration of normal compressor operation with no foaming.  As additives in the oil breakdown, foaming can increase and cause mechanical failure