Experience of Maintaining Hydraulic Systems
20 November 2020 by Mike Retford
Whilst maintaining hydraulic systems over a number of years we have come across some surprising faults and others that are preventable. We have shared some of experience below:
When working with a gauge control system in a Steel Mill, it was noticed that there was a large amount of leakage from the cylinders seals. The fluid was released down some pipe work to a oil collection tank and the amount was increasing daily. During the maintenance downshift, one cylinder was removed and the main rod pressure seal, a "U" shaped seal was found to have spilt around its circumference. Looking into the "U", light could be seen through it. Discussions with the seal manufacturer revealed an inherent fault in the seal and its material. New seal material was specified and this solved the problem.
Another problem was the overheating of oil in a reservoir, so much so, that smoke was coming from it. The major issue was that the cooling water supply had been severly reduced due to a blocked pipe, reducing the effectiveness of the oil cooler. Secondly the high temperature switch had failed, providing no warning or system shut down. This was a problem that could have been prevented by good maintenance. Having a flowmeter on the cooling water would have identified any degradation and regular maintenance of instrumentation would have found the problem temperature switch.
When working on a moving floor in a swimming pool hydraulic system, we found an incompatibility of the system fluid with the swimming pool water, that caused issues with the power unit's filtration. The swimming pool fluid had entered the hydraulic cylinder through poor maintenance and then entered the system reservoir. The system fluid was biodegradable and when mixed with the pool fluid formed a lacquer/paste, which coated components and blocked filters. This caused multiple valve, pump and cylinder failures. Improved maintenance, a new fluid and a more robust design solved the problems.
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