Traditionally, various testing methods are used to determine the lubrication properties of hydraulic fluids. The specific standard for mechanical testing of hydraulic fluids is based on a special type of hydraulic power unit, the vane pump (DIN 51 389, DIN 51 524). Numerous other procedures for mechanical testing of lubricants are used with the FZG-Test (DIN 51 354) being the most important one, in which the tested fluid is exposed to a certain load by shearing it in a gear set. Moreover industry uses several non-standard ‘in-house’ testing methods.
This situation cannot be satisfying in many respects: Since only part of the interaction between fluid and component is tested with the existing test procedures, the validity of test results is limited. Reproducibility of the test results is also limited, especially in the case of the vane pump test, due to the number of necessary test procedures, cost and time expense is too high. Finally, there is no proof that commonly used procedures will be suitable for more modern - for instance, biodegradable - fluids.
This paper describes the results of common laboratory and field tests with biodegradable fluids. Secondly, a new test procedure, which is developed by the authors, is described.