You invested in modern proportional valves. The machine runs smoothly like a dream, the cylinders silently lifting multi-ton loads with surgical precision. Two months pass, and suddenly... the system seizes up. The spool of the proportional valve is completely jammed, and the machine refuses to cooperate. What happened?
The culprit is most likely not a factory defect in the equipment, but an enemy often invisible to the naked eye: contaminants in the oil.
Many operators believe that if the oil looks reasonably clean, everything is fine. BRhydraulic experts debunk this myth. Find out why oil cleanliness is a matter of life and death for modern hydraulic power systems and how to build effective "three lines of defense."
1. Microns vs. Steel (Why dirt destroys valves?)
A human hair is about 70 microns thick. The human eye stops seeing particles smaller than 40 microns. Meanwhile, the gaps (clearances) between the spool and the body in modern proportional valves and servo valves are only 2 to 5 microns!
Even the smallest speck of dust, a metal shaving detached from the pump, or a grain of sand from a cylinder seal that gets into such a gap will act like a steel wedge. At best, it will scratch the precisely milled throttling edges (destroying the machine's smoothness), and at worst – completely jam the spool, leading to the burning out of the electromagnetic coil.
2. Three lines of defense, i.e., types of filters in the system
Effective machine protection involves not one, but several filters performing different roles. Where do we install them?
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Suction filters (Gatekeepers): Mounted inside the tank, on the pipe leading to the pump. Their task is to catch the largest "chunks" (e.g., pieces of packing, larger metal shavings, or screws that accidentally fell into the tank) before they damage the pump. They have a coarser mesh (e.g., 90-125 microns) to avoid blocking the flow of viscous oil.
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Pressure filters (VIP Protection): Absolutely crucial in systems with proportional valves! They are installed immediately after the pump and before the most expensive control components. They have very dense cartridges (e.g., 10 or even 3 microns) and robust housings that must withstand full operating pressure of around 350 bar. These are the ones that catch the microscopic metallic dust produced by the wearing pump.
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Return filters (Cleaners): Mounted on the pipe through which oil returns from the cylinders to the tank. They collect all contaminants generated during machine operation (e.g., flaking seals, shavings from cylinders) before the oil remixes in the tank.
3. The By-pass valve trap
Every modern filter has an element (paper, microfiber glass, or mesh) and a so-called contamination indicator (pressure gauge or electrical sensor). Many people ignore it. This is a huge mistake!
When the filter becomes clogged with dirt, the oil's resistance increases. To prevent the filter housing from bursting due to pressure, an emergency By-pass valve opens inside. Oil stops flowing through the filter element and bypasses it.
The machine continues to work, but the system is pumping completely dirty, unfiltered oil! That's why it's so important to react to the indicators and replace the elements on time.
Summary
In the world of hydraulic power systems, saving on filters and elements is the shortest path to replacing valves and pumps worth tens of thousands of zlotys. Clean oil (preferably in viscosity and cleanliness classes compliant with ISO 4406) is a guarantee of many years of trouble-free operation.
Take care of your machine's vital fluids. Contact us – we will help you choose a filter that will protect your machine from the invisible enemy!
