Search Results

It is difficult, if not impossible; to select any single test that will model the expected performance of any hydraulic fluid in a wide range of hydraulic pumps made by many different manufacturers. Increasing pressures often encountered in new hydraulic pump applications compounds this problem. However, some basic assessment of hydraulic fluid performance is necessary for numerous reasons such as: developing an appropriate fluid purchase policy, international standard development, fluid classification and others. Since the now-classic standard tests such as: ASTM D-2882, DIN 51389 and others are simply inadequate for this task and also since the manufacturer, Eaton Inc., no longer manufactures these pumps, it has been necessary to develop an alternative testing strategy [1, 2 and 3]. The Bosch-Rexroth Corporation has developed a high-pressure piston pump test that has been an excellent predictor of hydraulic fluid performance for many years.

Although the selection and role of hydraulic fluids as energy transfer agents is relatively well understood, there is no consensus on the appropriate procedures to evaluate lubrication properties on a laboratory scale. Because the use of bench tests such as the Shell 4-ball has traditionally produced poor pump wear correlations, it has been necessary to develop various hydraulic pump tests for this purpose. Since hydraulic fluid lubrication is being modeled, it is necessary to view these hydraulic pump tests as tribological tests. The objective of this paper is to provide an overview of various vane, piston and gear pump tests that have been reported as tribological tests.

In many situations, the root cause of a particular failure may be determined based on the observation of a single part, or perhaps a photograph, taken from the failed system. However, when failure analysis is conducted on the complete component, a different result often emerges. Such is the case described here for a piston pump that was operating on an anhydrous poly(alkylene glycol) - PAG at high pressure. Initial observation suggested the fluid was the root cause of the failure. However, when failure analysis was properly applied, it was learned that the root cause of the failure was due to mechanical failure caused by the motor-to-pump coupling. This analysis procedure is presented as a case history in this report.