For over 30 years the message has been “over 70% of hydraulic system failures are caused by contamination”. To clarify my position, I whole heartedly believe that a clean hydraulic system has a very good chance of being very reliable. However my experience of system failures would tend to question the statement above. In terms of pump and valve failures I have seen most probably five system failures directly attributable to contamination. In the steel works the systems were very clean and the number of failures were minimal. The biggest problems were hydraulic cylinder failures and cooler seal failures. Proactive maintenance sorted out those problems.
Outside of the steel industry I have seen a great deal of other hydraulic systems. Some systems have miraculously have kept operating with little or no filtration. These systems will be inefficient due to internal leakage from worn components. The major issues I have seen are poor hydraulic system design and build, plenty of leaking cylinders and plenty of leaking pipes. I have seen relatively few issues directly attributable to contamination.
Today you can easily detect if hydraulic systems are contaminated by taking a sample and sending it off to a lab or using an Automatic Particle Counter (APC). It is relatively easy to look after the condition of your hydraulic oil with the availability of hydraulic filters and filter carts.
In my view additional issues that need to be addressed to ensure hydraulic system reliability are:
Improved hydraulic system design with reduced short cuts taken for saving money.
Improved hydraulic cylinder design and repairs.
Improved selection and installation of hydraulic pipe fittings.
