Continuing our thoughts on hydraulic system maintenance we look at the sensors and experience of failures. When I worked In British Steel there were a lot of old hydraulic systems. We were working through schedules for all the systems in the strip mill, and during our implementation we had a failure on one of the systems not covered that taught us a valuable lesson.
There was smoke coming from one of the cellars one morning, going to investigate revealed smoke coming from the lid of the power pack. The emergency stop was activated and the system shut down. The oil was found to be above 80oC and that was causing the smoke. The prime failure determined after systems strip down was a loading valve keeping the system on load continuously. The secondary failure was the tank thermostat, which did not warn of high temperature or shut down the system on reaching 60oC. Level, pressure and temperature sensors protect the system, operators and maintainers from the effects of prime failures. It is important you know these work so they need to be checked during maintenance periods!
Interestingly the failure described above resulted in:
Disposal and replenishment of 2000 litres of oil. Cleaning out of the reservoir. Changing of all the systems seals. Removal all valves and pumps to clean due to the oil varnishing. Purchase and fitting of a new thermostat and loading valve. In all a very expensive and potentially very dangerous system failure.
