Various test methods have been developed to determine the performance limits of various classes of hydraulic fluids. Lubrication capacity depends on various fundamental fluid parameters including viscosity and anti-wear properties. Critical elements of hydraulic pump and motor lubrication, which is characterized by sliding line-contact wear, will be discussed here. In vane pumps, the pressure loaded tips of the vanes are under Hertz-type load in contact with the surface of the cam ring, and rotate at a high speed creating a sliding line-contact. Due to this sliding line contact, the vane pump is the best-suited instrument for determination of the anti-wear performance of hydraulic fluids within acceptable time and at reasonable expense.
Alternatively, hydraulic pump and motor testing may require greater energy, 150 kW or more over a period of more than 1000 hours significantly increasing the cost of testing. Furthermore, tests on smaller versions of one type of pump or motor do not necessarily correlate with larger units of similar design. Therefore, it would be desirable to develop a laboratory test that: utilizes a rig with standard wear parts, provides a selective method for identifying various forms of lubricant failure, and that permits tests correlation with a wide variety of hydraulic pumps and motors used in the industry today.