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Filtration Facts


Lubrication oil contamination is the primary cause of wear. From studies it has been shown that the highest rates of engine/transmission component wear are due to contamination by particles as small as or slightly larger than the oil film thickness between working parts. These particles are known as ‘clearance size’ particles. Larger particles cause less wear damage because they are unable to get into the clearance between the working parts. A combination of water and particulate contamination results in oil oxidation, and increases acid levels. Unless lubrication systems are well filtered they will continue to generate metallic particles and increase wear rates still further. It follows that lubrication fluids function most efficiently and last longer when water and clearance size particles are controlled.



Even superclean fluids may be contaminated causing wear of components. For example a high humidity environment can damage an unprotected oil/fluid.


The types of wear below are caused by metallic particles, sand, dirt and other wear debris. All these sources of particulate contamination add to the chain reaction increasing the rate of wear further.

  • Abrasive wear occurs when particles enter the clearance space between components, bury themselves in one surface and remove material from the opposing surfaces by cutting into them. Particles generated by abrasive wear become harder than the material they originated from due to work hardening and add to the chain reaction of wear.
  • Fatigue wear is the result of stressing by particles trapped between bearing surfaces. Initial dents and cracks spread due to repeated stressing, eventually leading to surface failure and further metallic particles being released into the lubricating fluid.
  • Adhesive wear occurs when reduced viscosity of lubricating fluid allows metal to metal contact. Surface asperities become cold welded together and shear from the surfaces as they move apart.
  • Erosive wear is caused by particles suspended in high velocity fluids which erode the surfaces they impinge upon. This type of wear is common in servo and proportional valves.
  • Corrosive wear is caused by water or chemical contamination. This type of wear is accelerated by the breakdown of lubrication fluids, for example precipitation of additives and oil oxidation. Removing free water will contribute towards extending the effective life of the fluid.