Technical Committee Lubricants

Mechanical testing of hydraulic fluids

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, especially in the case of the vane pump test. Run under the same conditions, some tests are leading to results of widespread variation with the problem of reproducibility; due to the number of necessary test procedures, cost and time expense is too high.
Aim of the project was to develop a new application related test procedure, which is able to overcome these malfits. Starting with an extensive analysis of tribological loads in hydrostatic machinery a new application related test procedure is developed. The design of the test rig and its running-in process is drawn out in this report.