There are three types of failure in a fluid power system.
1. Degradation. The performance of the component degrades over time as surfaces wear, clearances increase, and leakage increases.
2. Intermittent. Valves stick and then break loose such that operation is intermittent.
3. Catastrophic. Catastrophic failure occurs when a major component breaks apart. Often, debris causes the failure of other components, and a total replacement of the circuit is required.
Proper selection, placement, and servicing of contamination control devices will eliminate an estimated 80% of all system failures. Maintaining system cleanliness is a key issue in the operation of all fluid power systems, and particularly high-pressure oil circuits.