ASTM D942 test method for oxidation stability of lubricating greases
ASTM D942 standard test method for oxidation stability of lubricating greases by the oxygen pressure vessel method
3. Summary of Test Method
3.1 The sample of grease is oxidized in a pressure vessel heated to 99°C (210°F) and filled with oxygen at 110 psi (758 kPa). Pressure is observed and recorded at stated intervals. The degree of oxidation after a given period of time is determined by the corresponding decrease in oxygen pressure.
NOTE 1 - The pressure vessel has been referred to as "a bomb" in previous issues of this test method.
NOTE 2 - The accepted unit of pressure is the pascal (Pa) for ASTM methods and will be parenthetically included after the conventional pound-force per square inch (psi) value. The Institute of Petroleum uses the bar as a pressure measurement. Conversion of units may be obtained as follows:
To convert from pound-force per square inch (psi) to pascal (Pa) multiply by 6.894757 x 10(3).
To convert from pound-force per square inch (psi) to bar multiply by 0.06894757.
To convert from bar to pascal (Pa) multiply by 10(5).
4. Significance and Use
4.1 This test method measures the net change in pressure resulting from consumption of oxygen by oxidation and gain in pressure due to formation of volatile oxidation by-products. This test method may be used for quality control to indicate batch-to-batch uniformity. It predicts neither the stability of greases under dynamic service conditions, nor the stability of greases stored in containers for long periods, nor the stability of films of greases on bearings and motor-parts. It should not be used to estimate the relative oxidation resistance of different grease types.
