A hydraulic system used force applied at one point to transmit it to another point using an incompressible (hydraulic) fluid. One of the most important requirements for hydraulic fluids is cleanliness. Particle contamination is the most common hydraulic system failure mode leading to wear and damage to the fine tolerances of valves, motors and actuators.
Filtering and condition monitoring are used in conjunction with each other to prevent system failure. A condition monitoring program will analyze hydraulic fluids for particle contamination from dirt and wear metals, corrosion due to water, and lacquer buildup due to degradation or additive depletion.