Purification of Hydraulic Oils

Purification of Hydraulic Oils

Hydraulic oil is a fairly common product and in many cases it is used in sensitive equipment and technology.  Since recently, filters with a mesh size of 25 to 50 micron have been coming into use in most oil systems.  This was enough to meet purity conditions, for instance, for valves.  But components in hydraulic systems contain narrow passages with low flow rate, which, in the event of oil contamination, can have a significant influence on the entire system as well as its wear.

Types of hydraulic fluid contaminants

Hydraulic fluid may become contaminated as a result of several factors.  First we need to understand the basic difference between primary and secondary pollution.  Primary pollution occurs in the system before commissioning.  Accordingly, secondary pollution is the pollution that occurs directly during equipment operation.  Primary system contamination occurs due to the presence of residues of machining and assembly, as well as the impurities contained in fresh oil.  Secondary contamination is most often caused by machining residues, products of abrasion and corrosion, and dirt, which gets into the system from sealing materials of cylinders or through breather channels in tanks.

Previously, less attention was paid to the dependence between hydraulic equipment service life and the purity of hydraulic oil.  But recent studies have shown that there is a strong relationship between these parameters.  Therefore, hydraulic oil purification should be a mandatory procedure, an important part of measures aimed at extension of service life of machinery and equipment and reduction failure rate.

For example, the all-knowing statistics says that the main causes of premature failure of roller bearings include inadequate lubrication, the presence of particulate matter in oil and overload.

Hydraulic oil purification using filtration method

The general use of filters is the removal of mechanical impurities from hydraulic oils.  The best cleaning results are achieved by installing these devices in several points within the system:

At the tank outlet channel.  This filter is needed to remove the dirt which got into the system with the air;

  • At the pump inlet.  These filters are called filter presses;
  • In the upper part of the tank;
  • In the tank circuit (bypass filter);
  • In the fluid recirculation lines (return filters).

Filter parameters include mesh size and the degree of separation.  For example, if there is a designation β3> 200, it means that you deal with a mesh size of 3 microns, and the degree of separation is 200.  It says that only one particle out of 200 can pass through the filter.

The filtration process efficiency depends on the materials used.  The most common materials are: fiberglass, cellulose paper and metallic mesh.

In general, a hydraulic oil filter consists of a filtering element, pollution indicator and other components.  Filter selection is a strictly individual issue for each system.  Mesh size is usually determined empirically in accordance with the requirements of critical components.  Most frequently, hydraulic systems utilize filters with mesh size from 3 to 40 microns.  It is possible to use devices with a mesh size up to 1 micron, but in this case it is necessary to monitor filter condition, as viscous additives and corrosion inhibitors may lead to clogging of the filter.

GlobeCore offers CMM-type hydraulic oil filtration plants, known for their mobility, cost effectiveness and high quality of product purification.  The required filtration fineness is ensured by repeated passage of oil through a special filter unit.  The equipment is versatile, because it can also work with other types of oil and can be used for oil heating.


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