Modern hydraulic systems are operating at higher pressures and higher temperatures than ever before. In addition, the life and reliability of the hydraulic components and hence the hydraulic system is becoming more and more dependent upon the characteristics of the circulating fluid in the system. The hydraulic component which normally suffers most when the correct fluid is not used in the system is the hydraulic pump. Three different types of hydraulic pumps are widely used in hydraulic systems. Vane pumps have been the dominant type of pump for hydraulic systems. Gear pumps have replaced vane pumps in many applications. Piston pumps are rapidly gaining popularity. Therefore, the pump manufacturers are conducting tests to qualify fluids for use with their pumps and the fluids formulators are conducting tests to show that their formulations are compatible with hydraulic components. Unfortunately, the tests most widely used are either not industry standards or do not address problems encountered with some hydraulic pumps.
This paper presents an overview of the pump tests which are currently available or which are specific to certain hydraulic pumps. Since there are few standard pump tests, many companies have devised their own tests to be confident of the fluids which they qualify. Additional concepts in pump testing are proposed and discussed.