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Contamination Control in Hydraulic Systems    

Contamination Control in Hydraulic Systems

Contamination in hydraulic systems is now recognised as the most frequent cause of malfunction or failure of hydraulic equipment.

Depending on the nature, size and/or amount of contaminant, the effects can be:

  • Reduced component service life
  • Machine malfunction, particularly when operating near maximum capacity
  • Risk of frequent breakdowns under the same conditions
  • Production rates below scheduled
  • High product scrap and defect rates

Nature of contaminant

Contaminant can be either:

  • Particle contaminant


  • The product of fluid degradation

Particle contaminant:

  • Particle contaminant can be singular by product
  • Several types of contamination can be present at the same time i.e. metal, rubber, plastic, dirt, dust, fibre, sand, paint etc.
  • These can enter the fluid at any time after the fresh, clean fluid has been produced by the fluid manufacturer themselves.

Fluid degradation results in:

  • Oxidation and/or the formation of deposits and sludge from the combined effects of high temperature, air, water and particle contaminants. Such contaminants increase viscosity, viscid deposits and clog orifices/small passageways which impair the smooth mechanical movements and eventually form sludge like deposits.
  • Unstable emulsions of poor lubricity form when water is inadvertently emulsified with oil. Such contamination impairs the smooth mechanical movements and promotes wear.
  • Aeration or air bubbles in the fluid, at low pressures and in excess, can cause noise in pumps and valves leading to erratic or loose machine movements, resulting in premature wear and failure.

Preventative measures

  • Only remove protective caps just before connecting mating components.
  • Use a portable filtration and transfer unit to fill the reservoir system.
  • Flush new systems and those that have recently been repaired before starting up.
  • Temporarily remove actuators and replace with flushing manifolds or valves.
  • Make sure that air breathers and reservoir covers are properly installed and tightly secured.
  • Stop any leakages of water into the system from coolers or other sources, ensuring that there are leak-tight repairs.
  • Take regular fluid samples and analyse to determine whether effects of particle contaminants, heat, water and air indicate the need for more control of those factors or whether replacement of the fluid is required.
  • Whenever the reservoir is emptied, clean it out thoroughly and remove all residual contaminant.

Contamination affects all types of hydraulic equipment. Dirty fluids cause wear which accelerates leakage and the development of heat on a system. Heat lowers the lubricity of hydraulic fluid and causes additional wear.

When hiring equipment from HTL you don’t have to be concerned with fixing problems onsite or sourcing the correct solution yourself; HTL’s industry knowledge and expertise is available 24/7 to assist you. With express delivery available and our Fast Track Calibration Service, replacement equipment is sent direct to site reducing your downtime whilst your equipment is being repaired or calibrated by our fully qualified Service Engineers.

For more information or for an instant quote contact us today: call +44(0)1670 700 003 or email /

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