ASTM D3337 method for determining life and torque of lubricating greases
ASTM D3337 standard test method for determining life and torque of lubricating greases in small ball bearings
10. Report
10.1 Report test results and test conditions on the report form shown in Table 1.
11. Precision and Bias
11.1 The precision of this test is not known to have been obtained in accordance with currently accepted guidelines (for example, in Committee D-2 Research Report RR: D02-1007, Manual on Determining Precision Data for ASTM Methods on Petroleum Products and Lubricants).
11.2 Grease life data generated in cooperative testing using this procedure show appreciable scatter and were found to conform in the general case to Weibull probability distributions rather than normal distributions. Conventional ASTM definitions of repeatability and reproducibility are meaningful only for data that can be described by normal distributions and, therefore, are not appropriate. Weibull parameters such as slope, L10 and L50, are used to describe the distribution of the test data.
11.3 Precision may be judged from Fig. 1 and Fig. 2, which are Weibull plots of the data obtained in test programs involving two greases and seven cooperators. Weibull parameters calculated for the data are summarized in Table 2.
11.4 The precision of the test may also be judged by considering Table 3, which summarizes the data obtained in the cooperative program.
11.5 Because the life results obtained show appreciable scatter, replicate testing is essential when using this procedure.
11.6 Bias - The procedure in this test method for measuring grease life in small ball bearings has no bias because the value of grease life in small ball bearings is defined only in terms of the test method.
12. Keywords
12.1 lubricating grease; lubricating grease life; lubricating grease torque; running torque; small ball bearings
