Lube-Tech
After the above examples, a selection of the most relevant tests that can reveal a long-term incompatibility between hydraulic fluids are listed in the table above.
The mentioned properties must consider the fluids composition, the operating conditions, the materials, the seals, and the environment, ...
5. Conclusion
Hydraulic fluid is one of the most vital components of a hydraulic system.
Interpretations must be done carefully when we speak about fluid compatibility. Even if a lubricant manufacturer or an operator declare the hydraulic fluids are miscible, are they compatible? In other words, does the HF mixture still provide the required properties at the same performance level as the original fluids.
The evaluation proposed in this article is a step-by- step approach. Firstly, a review based on information we have on HF components chemistry.
Next, there is an evaluation of some mixtures to check signs of visual incompatibilities before carrying out filterability tests and surface properties deterioration.
The last step is to check the long-term compatibility through laboratory performance tests, considering the fluid’s composition, operating conditions, materials, seals, and the environment.
At each step, if an incompatibility is detected, it’s not necessary to go further. The last step is important in order to detect a long-term risk which originally comes from a hydraulic fluids mixture.
LINK
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PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.137 page 8
6. References [1] George E. Totten, Victor J. De Negri, CRC Press, 2012, Handbook of hydraulic fluid technology, second edition.
[2] ASTM D7752 standard “Evaluating Compatibility of Mixtures of Hydraulic Fluids, 2018.
[3] Jim Fitch, 9/2006, Noria corporation, Recognizing the Symptoms of Lubricant Incompatibility.
[4] Bernd Krause, Ferdinand Megerlin and Herbert Oswald, 1998, The “Linde Test” – A sreening method for biodegradable oils with respect to copper-alloy-corrosion.
[5] Bosch Rexroth AG, 09/2018, RE 90221, Environmetally acceptable hydraulic fluids, Germany.
[6] S.P. Srivastava, 2014, Developments in Lubricant technology, TJ1077.S74, Edition Wiley, India.
[7] ISO 13357-1/2, ISO 6072, ASTM D2619 test methods.
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