Search Results

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.

Hydraulic piston pump failures may be related to either hardware or fluid problems. In some cases, apparent hardware failures have been traced to various fluid problems. In this paper, selected examples of pump failures will be provided to illustrate some common modes of axial piston pump failures. In most cases, these will represent actual failures including: misalignment, insufficient fluid lubrication, particle contamination, brinelling, corrosion, and cavitation. Various examples of these and other pump failure modes are provided.

Currently, the industry standard pump test which is used to evaluate the lubricating performance of hydraulic fluids is ASTM D-2882 [1,2]. This test, and others, utilizes the Vickers V-104 vane pump [3]. Although ASTM D-2882 has been an industry standard for many years, it does not provide the necessary correlation required for prediction of the lubricating properties of a hydraulic fluid in various piston pump operations. The objective of this paper is to detail the recently proposed Rexroth Piston Pump Test which is being proposed as an ASTM standard. A description of the proposed hardware, pump testing strategies and methods of standardized wear determination will be provided.