Modern hydraulic control systems are making increasing use of servo and proportional control valves. These devices are inherently at the critical stage of controlling the manufacturing process and quality of the end product. Proportional valves are also found in ancillary functions for materials handling where time is of the essence. Failure of control valves will cause very expensive loss of production many times more than the cost of prevention.
The principal means of prevention is the maintenance of the hydraulic fluid with regard to cleanliness and chemical composition. Cleanliness is a function of selection of the appropriate filters for the valve and application environment. Chemical properties relate to factors such as water content and various forms of break down that can occur due to chemical contamination, excessive heat or working of the fluid.
These factors can be monitored effectively at a relative low cost by laboratory tests offered by filter companies and suppliers of hydraulic fluids.