An Effective Bench Test for Hydraulic Fluid Selection

The selection of a proper fluid to be used in a hydraulic system is an important part of any design effort. The hydraulic fluid must normally transmit, transform, and control the power from the system input to the output. In addition, the fluid is expected to provide lubrication and antiwear protection to many of the other components in the system. Although there are at least 22 parameters which describe a hydraulic fluid, most of these parameters are well defined. However, the antiwear and lubrication properties of a hydraulic fluid deserve more discussion.

There are several test methods which have been developed to assess the antiwear properties of liquids. Most of these procedures are intended to evaluate fluids other than those directed toward use in a hydraulic system. This paper will present a bench type wear test method designed to overcome the recognized problems of other wear test procedures. Developed by the authors at the Fluid Power Research Center, formerly at Oklahoma State University, this bench test method is called the Gamma Wear System. In addition to describing this type of method, the paper will present actual test data obtained from hydraulic fluids.