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Fluid Contamination Measurement & Analysis: Filtration 

When it comes to the maintenance of a hydraulic system, nothing is more important than proper filtration. Most component failures are the direct result of contaminated hydraulic oil. The expense of having to replace hydraulic components damaged by contamination is often minor compared to the even higher cost of unscheduled downtime for the machine. 

Simply putting a filter on the return line of a hydraulic system is not the solution in today’s highly technical hydraulic systems. With system operating pressures increasing and the prevalence of even more contamination-sensitive proportional and servo controls, the hydraulic system designer must take an aggressive approach to hydraulic system cleanliness.

Today’s filter manufacturers have spent millions in testing and developing filters that have extremely high efficiencies and particle-retention capabilities. In addition, many innovative methods for testing and monitoring hydraulic oil cleanliness can take the guesswork out of knowing the condition of the oil and predicting contamination-related failures before they occur.

Specifying the filter and element combination has become an art, with most component manufacturers specifying both the Beta ratio required as well as the ISO cleanliness level required for their equipment. This optimum ISO cleanliness level will depend not only upon the types of components in the system, but also on the:

  • operating pressure
  • ambient temperature
  • what types of ingression might occur
  • fluid type
  • additives in the fluid
  • compatibility of component seals

A hasty approach to filter selection could result in serious system problems. Too fine a filter/element will increase cost of the filter, generate heat in the system, cause higher than desired pressure drops, and could potentially filter out the fluid’s desired additives. Too coarse a filter/element will not adequately protect the components in the system.

Much has changed for filters in hydraulic systems in recent years, as further developments are made in components, fluids, and seals. In the past, a screen or suction strainer might have been used on the inlet of a pump. Today, most manufacturers advise against a suction screen because it is more likely to cause an unwanted high vacuum at the pump inlet.

The Fluid Power Specialists at Quality Hydraulics & Pneumatics, Inc. are well educated and know all the current standards to help specify the appropriate return line, pressure line, or offline filtration required to optimize your particular system or application.

For more information contact Gary Alexander, Fluid Power Specialist, at (847) 680-8400.

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