The Four Ball Wear Test
The four ball test for wear as outline by ASTM D-4172 is used to determine
the ability of a lubricant to prevent wear by operating the oil in conditions of
sliding contact. During this test three metal balls are clamped together
in the fluid to be tested to form a base upon which the fourth ball will rotate
under pressure. The fourth ball has 40 kg of pressure applied to it and is
rotated at a speed of 1200 rpm at a set temperature for a period of one hour.
Wear scars will form on all four metal balls, which can then be measured under a
microscope to determine to determine the measurement in millimeters. The
smaller the size of the wear scar, the more effective the air compressor oil is
at handling the the wear contact that is encountered in all parts of the
compressor, but especially at the bearings of the compression element or rotors.
A good way to compare synthetic oil and petroleum based products
The four ball wear test is a means to compare compressor oils, and is often
seen as a good comparator, along with other standard testing to determine if
non-OEM oil is suitable to replace the current manufacturers product offering.
It also is a good indicator of the advantages of synthetic oil over its