What are Hydraulic Filters and Why Do I Need Them?


Fluids can get contaminated because of many factors. Components, unsanitary plumbing, and contaminants are all contained in fresh fluid, which is one of several causes. Without the employment of a filter, any fluid power system is incomplete. Hydraulic filters are essential to maintaining a contaminant-free hydraulic fluid.

Types of Hydraulic Filters

Several filtration options exist, including bag, screen, and magnetic. Here, the impurities are unable to flow through the bag. Filtering out dirt, rust, and various particles brought into the system by a cylinder rod is made easier by this, in particular. To manufacture a screen filter, tiny wires are braided together to form a metallic fabric.

Engineers can use these filters to set a very specific pore size, which makes it possible to select the most appropriate filter size for the type of contamination they predict. Finally, magnetic filters are included. Metal particles stick to these magnetically charged plates, which can be found in many types of filters. One significant criterion for selecting a filter is the process of constructing it. Included in this is information on the filter and alignment.

Knowing whether a filter includes the housing is vital when purchasing a filter because a filter may or may not need the housing. There are multiple filter alignment possibilities. This is called an “in-line” alignment because when all the outlets, inlets, and filters are lined up, it creates a single line. An “off-line” alignment occurs when the filter is placed on a hydraulic system’s loop that does not pass through the system that contains the filter.

Another type of setup, which is called “duplex,” exists. When there are two filters, they are put together. Changing the filter elements doesn’t affect the system because of these filters. In a “return-line” setup, the system can catch all of the pollutants introduced.

How Effective is the Filter?

A filters’ effectiveness is measured by its rating. ISO 4406, which is used to gauge contamination levels, is one such measurement. A 2-3 digit code contains numbers that reflect logarithmic measures of the number of pollutants present in fluids with contaminants measuring 4, 6, and 14 µm in three respective measurement categories of 1 ml.

For instance, you may get a fresh sample that reads 18/15. The first measure relates to 1300-2500 particles ranging in size from 4 microns, while the second refers to 160-320 particles that are larger than 14 microns. To extend the life of the components in the hydraulic system, install a filter with a low ISO cleanliness grade, which will be better at filtering out impurities and making the system more effective for twice as long.

A filter’s beta ratio is a ratio of the number of contaminants upstream of the filter to the number downstream. This metric of filter efficiency is important. To get the filter’s overall percentage efficiency in catching contaminants of a certain size, remove 1 from the beta ratio, divide by the beta ratio, and multiply by 100. When looking for a hydraulic filter, consider going with one that has a higher beta ratio.

Selection Criteria

Hydraulic filtration products help to keep the hydraulic oil clean, reducing the presence of pollutants in the system introduced by normal use and wear or new parts or fluid. The flow level dictates how much fluid flow is allowed through the filter and also defines the maximum flow rate.

  • The “maximum operating pressure” that the filter can tolerate is known as “pressure.”
  • Port size refers to the size of the input and outlet ports and is measured in millimeters.

Properly maintained fluid helps keep the components of a system in good shape longer, reducing upkeep costs and extending the use of the equipment.