OIL SEPARATION FROM GREASE BY CENTRIFUGING (KOPPERS METHOD): ASTM D4425
EXPLANATION
This test method is useful in evaluating the degree to which a grease would separate into fluid and solid components when subjected to high centrifugal forces. Flexible shaft couplings, universal joints, and rolling element thrust bearings are examples of machinery which subject lubricating greases to large and prolonged centrifugal forces. This test method has been found to give results that correlate well with results from actual service. The test method may be run at other conditions with agreement between parties but the precision given in this test method may not apply.
TEST SUMMARY
Pairs of centrifuge tubes are charged with grease samples and are placed in the centrifuge. The grease samples are subjected to a centrifugal force equivalent to a G value of 36000 at 50° C +/- 1 ° C, for specific periods of time. The resistance of the grease to separate the oil is then defined as a ratio of the percent oil separated to the total number of hours of testing.
TEST PRECISION
Repeatability: 4.8 % points of value of oil separation in vol. %
Reproducibility: 18.7 % points of value of oil separation in vol. %
The procedure in this test method has no bias because the value can be defined only in terms of the test method.
