Valves: Microscopic contamination (similar to erosion) can mill away tolerances which are used for sealing purposes. On spring centering valves, the debris may get caught between the valve and the wall surface. The contamination will cause the slowing down of the motion of the valve or causing sluggish or adverse mechanical actuation.
Abrasive particles enter the clearances between moving parts they score and hone the surfaces to greater tolerances. As these tolerances broaden, system performance is compromised by pressure losses incurred due to fluid leakage from high to lower pressures.
The worst occurrence is when particles that are greater than or equal in size to the orifice openings become wedged between the two surfaces. The contamination may cause wear to occur or it may cause the system components to seize.
Pumps & drives: Microscopic contamination can mill away material, creating leak points. These leak points rob the hydraulic system of pressure and cause poor responsiveness.
System cooling: Working fluid may not flow through to remove contaminants generated from metal to metal contact when passages become blocked. Lower flow rates mean greater heat buildup in systems and thermal breakdown of the working fluid.