The secret to an efficient hydraulic system lies in its lifeblood - the hydraulic fluid. Ensuring the purity of the hydraulic fluid is key to the longevity, reliability, and efficiency of the entire system.
Hydraulic filters play a primary role in protecting the system from harmful contaminants and particles that can lead to premature wear. These filters remove harmful substances and ensure that sensitive system components, such as pumps, valves, drives, and lines, can continue to operate optimally.
Within the industry, there are two relevant filtration methods: surface filtration and depth filtration.
Surface filtration
Surface filtration is based on the principle that solid particles are retained on the surface of a filter due to their size. The mesh size of the filter must be smaller than the particles to be separated.
For simplicity, you can think of a surface filter like a sieve.
A disadvantage of surface filtration is that particles that should be retained due to their length can slip through the mesh size, depending on how they hit the "sieve."
In cases of very high particle loads, contamination can accumulate on the surface, forming a filter cake that then takes over filtration and separates significantly smaller particles. This leads to increased flow resistance of the filter and reduced filtrate flow, a faster increase in differential pressure (delta pQ), which is a sign that the filter is blocked.
Filters with short service lives usually end up in the lab for examination of dirt loading and particle type to identify what caused the filter to block so quickly.
Depth filtration
Depth filtration is an effective method for applications requiring high particle removal. Depth filtration is based on two principles: larger particles are retained on the surface if they are larger than the pores, while smaller particles penetrate deep into the pore structure of the filter material and are mechanically and absorptively retained there.
The effectiveness of depth filtration is expressed by the Beta value. The Beta value is a measure of a filter's efficiency and indicates how well a filter can remove particles of a certain size from a fluid. It is calculated by dividing the number of particles before the filter by the number after the filter. A high Beta value means effective filtration and high particle removal efficiency.
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