Lube-Tech
to corrosive effects with copper-based alloys. The consequence of this type of corrosion usually occurs only after several thousand hours and can lead to substantial damages.
The most relevant test to evaluate the anti-corrosion property on yellow metal is the dynamic Linde test according to VDMA 24570. This laboratory test is a screening method capable of establishing a correlation between field experience and the results of accelerated tests.
It consists of a thermostatically controlled heater plate with the test container. The container is filled with the test fluids (89% of fluid (ester), 10% of mineral oil and 1% of water) and glass beads (550g). Four specimens of different materials (brass, cast bronze, sintered bronze and steel) are fixed on a specimen holder which is attached to the stirrer. The stirrer is inserted vertically and rotated at 200 rpm. The vertical shaft is routed through a condenser in order to keep the water content of the fluid constant. The test duration is 100 hours at 120°C. Upon completion of the test run, the weight loss is measured on each specimen and reported in g/m².
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.137 page 6
occur with HE fluid and NBR seals or HL fluid and EPDM seals.
The compatibility of an elastomer with hydraulic fluid is a critical factor in system performance and reliability. As there is a broad range of chemical and mechanical interactions and environmental conditions, it is difficult to predict the compatibility without being exposed to the system’s fluid and environment. An attempt may however be made with the elastomer compatibility test. The evaluation is carried out by comparison of some seals parameters (hardness, volume, tensile strength and elongation at break) before and after a soaking period.
Figure 4. Description of static seals compatibility test ISO 6072
Figure 3. Description of dynamic Linde corrosion test VDMA 24570
4.5.2. Effect on seals when mineral oil based HF is mixed with a synthetic HF
Some incompatibilities are already known and may 28 LUBE MAGAZINE NO.166 DECEMBER 2021
Figure 5. Traction machine used for seal tensile strength and elongation at break
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