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Follow These Simple Steps to Flush Your Hydraulic System

People generally think about flushing their hydraulic systems when they are thinking about changing from one type of oil to another. The aim of flushing the system is to remove the old oil and clean the entire chamber so that bits of it doesn't mix with or contaminate the new oil. Some of the DIY solutions that people come up with include the use of diesel fuel, acid cleaning, and brake cleaner. While these may seem practical, it is crucial to note that some contain chemicals that could ruin your Ethylene Propane or EPDM seals. When choosing a flushing solution, the material of your O rings should be the first consideration you make.

Draining the system

The first step in the process is removing the old liquid. This is done correctly when the fluids are still at their optimum temperature. When draining the system, ensure that you pay attention to reservoirs, lines, cylinders, filters and any parts of the system where fluid likes to accumulate. It is also recommended that you remove filters before replacing the fluid, because they will also have accumulated enough contaminants to ruin the new fluid.

Mechanical cleaning

When all the parts of the system are clear from the fluid, get a lint-free rag and start cleaning the interior of the reservoir. The main aim of this dry scrubbing is to remove any sludge and other deposits that may have formed there. When doing your scrubbing, also make sure that you remove any paint that may have come loose during the cleaning process. 


Flushing is most effective when you use a fluid whose viscosity is similar to that of the liquid you are removing. Choose a fluid whose Reynolds number is between 2000 and 4000, as this creates perfect turbulence to get rid of any particles from the lines. Keep changing the fluid and cleaning the reservoir till you reach a cleanness level that is a step beyond the target cleanness level of the system. When done with the flushing, drain the flushing liquid as fast as possible and ensure it is as hot as possible when you flush. Inspect again for cleanness.

Replacing the fluid is the last step in the process. You will do this by filling the reservoir up to three-quarters full of the fluid which you want to use. Run the pump while stopping at intervals. Finally, you can keep sampling the fuel until you are sure that the system fluid has completely stabilised. 

The job can be made easier by using a Hydraulic Flushing Unit. Talk to a local supplier to learn more.