FLUID POWER HANDBOOK
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HYDRAULIC
IMAGE COURTESY OF MP FILTRI
FILTERS
Many fluid power systems fail simply because there is too much particle contamination in the fluid medium. In fact, some estimate that 75% of all fluid power failures can be attributed to contamination-related issues. Thus you, as an engineer, technician or end-user, who ignores filtration does so at the peril of your hydraulic system. There are multiple reasons why your hydraulic fluid becomes contaminated. Every hydraulic machine is first manufactured with built-in contamination during machining, cutting, welding and grinding of the reservoir and fixed plumbing. Additionally, contamination ingression also occurs from either new oil (which is dirtier than you imagine) or external sources such as fallout, grime, mud and dust. Finally, the components in your system generate their own particles when friction components such as bearings, pistons, spools and swashplates rub together. Removing all forms of particle contamination is your highest priority to ensure a long, reliable life for your hydraulic machine. Filters are your first line of defense to reduce the number of particles in your fluid. Filters also prevent excessive internally-generated contamination, considering particles exacerbate the rate of internally generated contamination, acting like liquid sandpaper. There are several types of filters for you to choose, the most popular of which are inline cartridge and spin-on filter assemblies. The inline cartridge filter assembly is popular and is available for
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Hydraulic Filters 7-19_FPW Vs3.indd 22
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pressure and return lines. These assemblies have a drop filter cartridge (as shown in the cutaway on this page) that can be removed and replaced when they become clogged. Spin-on filter assemblies are also used for inline applications, although their location is typically limited to return lines. Some manufacturers make heavy-duty assemblies, rated for upwards of 500 psi, which make them ideal for you to use in return lines experiencing pressure spikes. Other filter options exist, such as bag filters and suction strainers. Bag filters are used when large volumes of fluid are being processed, such as is required in steel mills. They are less common in a “live” system where they’re exposed to primary pump flow but are instead more popular in high volume
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7/15/19 9:31 AM
