Fluid qualification tests – evaluation of the lubricating properties of biodegradable fluids

Abstract

To develop a new, biodegradable hydraulic fluid, numerous standard and in‐house screening tests are necessary to verify the lubricating properties. It was further determined that evaluation within a hydrostatic transmission, simulating field operating conditions, as a final test is critical but needed, as new fluids will occasionally fail this test, although all prior tests were passed. This paper describes recent experiences at the authors’ institute with ester based hydraulic fluids run in a heavily loaded hydrostatic transmission under laboratory conditions on the so‐called “flywheel test rig”. Change of fluid properties and wear behavior of the hydrostatic components are compared to derive statements about the fluids’ behavior to be expected in the field application.