Hydraulic Filtration and Particle Count

Hydraulics filtering systems can be found on most modern machinery and equipment. Especially earth-moving equipment and heavy machinery because these machines use hydraulic fluid to displace heavy components of the machine design.

What are hydraulic filtering systems?

A hydraulic filtering system is a filtration system used in hydraulic applications to keep the oil purified and filtered. An example of a hydraulic system would include heavy machinery; trucks that use out-rigging have a hydraulic system and presses in a machine shop.

Much like the filter in a water filtration system catches foreign matter, dirt particles, and impurities in the water, a hydraulics filtering system is a system that purifies the oil within the system and catches all dirt particles and foreign matter in the filter. The filter itself is usually replaced by scheduled maintenance, breakdown repairs, or servicing. When these repairs are conducted, a full refurbishment of the hydraulics system is completed. All components will be measured to see if they meet the specifications, and seals will be replaced along with the oil in the system.

A hydraulics filtering system uses a specialized filter because the oil viscosity is thicker than water. This means that the design of the hydraulics filter will accommodate the viscosity of the oil flow and pressure while still capturing dirt particles, debris, and foreign matter. These particles, debris, and foreign matter usually break away from the seals, and this is what contaminates the oil, hence the need for the filtration system.

If the system is left unchecked, the debris and foreign matter can cause irreversible damage to the hydraulics system.

Different types of hydraulic filtration systems

Different hydraulic systems will have different requirements for a filter. It’s important to use the right filter on the right system.

• Spin-on filters – These filters work best on low-pressure systems that do not have any high-pressure surges, from time to time, and are manufactured for inline applications.
• Suction filters/strainers – These filters are placed in the hydraulic reservoir and prevent contaminants from flowing with fluid into the hydraulic pump. They are the last effort in the system to prevent dirt and debris from passing through.
• Reservoir breather filters – These filters are placed inside the reservoir and prevent dirt that enters via the air from moving to the hydraulic tank.

How fast can I filter hydraulic oil, and how small a particle count should it be?

Harvard filters to one micron and removes water. Shell Oil did research that shows the majority of valve wear comes from particles 3 microns in size. The oil filtration process to a one-micron level is not a fast process. Therefore, it is not a full-flow filtration. Oil is slowly passed through a depth filter and returned to the sump. To get a faster flow, more canisters and filters must be added to a process in parallel, usually with a larger pump and motor.

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