It is well known that the wear rates of materials evaluated in bench testers are fairly reproducible. However, the performance of the materials obtained in bench tests and practical uses were sometimes completely different from each other. This paper discusses the reasons for such discrepancies observed in hydraulic pump testing in terms of the test conditions and the response of the fluid to them. By analyzing the test condition that reproduced the pump wear in bench tests, it is suggested that at lower temperatures and pressures, the behavior of the fluid at higher temperatures and pressures could be reproduced. Then it is concluded that applying the estimated load and sliding velocities in actual pump to bench tests that use different contact configuration may cause the erratic results. It is also concluded that estimating the phenomena governing the performance in an actual pump is one of the keys to conducting useful bench tests.

The factors that affect the test results and the usefulness and limits of the bench tests are also discussed.