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How Filter Locations on Hydraulic Systems Can Make All the Difference ben lee

It’s no secret that removing particle contamination can greatly increase the life of the components in any hydraulic system. The truth is, is that there are always some particles present, even in brand new hydraulic fluid. How much contamination can be accepted is going to vary depending on the hydraulic system being used.

So how do you go about removing particles in a hydraulic system? If the system is large, then it’s recommended to add filters wherever you feel it’s going to give you the most advantage.

The strange thing about hydraulic system filters is that although they are there to help keep your machine running well, they can sometimes cause damage and shorten the life of your system.

Hydraulic filters run on a rating system that defers to the micron size of the particles being removed. To get the best results, take a sample of your hydraulic fluid so that you have some idea of where you’re starting from and which filters you’ll need. Ideally you’ll flush the fluid before adding new filters so that their main job will be to maintain its cleanliness rather than to clean it up.

No matter where you start from, it’s important to keep in mind that the filters that you use will affect pressure and it could drop it by providing restriction. If this occurs, then it’s possible that the bypass valve on the filter will open and therefore filtering will not be implemented.

If you’re an engineer who has the responsibility of deciding where to put the filters, it’s critical to do this with a mind to prevent any harm from occurring. There’s no point in delivering cure that is worse than the disease.

Here’s our take on what you need to know about where to fit filters on hydraulic systems:

Pressure line. Many components that are located downstream will benefit from positioning the filter in the pressure line. It’s possible to capture as small as 2 microns or less as the pressure will help as it forces the fluid through the filter. However, it’s possible that the filter will be reduced by the high flow velocities which can loosen up trapped particles. In the long term its pressure filtration that costs the most to maintain and the most to get going with.

Return line. The most effective principle to apply to this is that if you start out with a reservoir full of clean fluid, then keeping fluid clean by filtering it will keep it that way. Another benefit of using the return line to add a filter is that you’ll gain advantage from the higher pressure. It’s possible to gain good filtering results at a relatively low cost as there won’t be filter or housing design complications with a pressure of that measure. In actual fact, the lower flow will deliver a filtration that is efficient and low cost. The only disadvantage of this method is that there is a chance of the back pressure causing some issues.

Off line. Filtering your fluid using the off-line method will provide you with a continuous filtration that is multi-pass. The results are excellent filtering efficiency where you can pull out particles that are 2 microns or less in size. It’s also possible to extract water and even heat in order to give your fluid total conditioning. However, there is a cost disadvantage when starting out with this method, but this can usually be reclaimed over the life of the machine.

Suction. Positioning a filter next to the pump intake can provide advantages gained by not being in a high pressure area, however, it does have potential to cause some issues with regards to pump life.

Filtering is important in any hydraulic system and it’s not just about what you use, it’s about where you put it. 

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