There are four types of oil filters according to their filtration accuracy (the size of particles to filter out impurities). There are coarse filters, ordinary filters, precision filters and special filters. They can filter out more than 100μm, 10-100μm, 5～10μm and 1～5μm size impurities.
Note: When selecting the oil filter, the following points should be considered:
(1) The filtration accuracy should meet the predetermined requirements.
(2) It can maintain sufficient flow capacity for a long time.
(3) The filter element has sufficient strength and will not be damaged by hydraulic pressure.
(4) The filter has good corrosion resistance and can work for a long time at the specified temperature.
(5) The filter element is easy to clean or replace.
Therefore, the oil filter should be selected according to the technical requirements of the hydraulic system, filtration accuracy, flow capacity, working pressure, oil viscosity, working temperature and other conditions.
The installation positions of the oil filter in the hydraulic system are usually as follows:
It must be installed at the suction port of the pump: a surface-type oil filter is generally installed on the suction line of the pump to filter out larger impurities and particles to protect the hydraulic pump. In addition, the filtering capacity of the oil filter should be the pump More than twice the flow rate, the pressure loss is less than 0.02MPa.
Installed on the outlet oil circuit of the pump: The purpose of installing an oil filter here is to filter out pollutants that may invade valves and other components. Its filtration accuracy should be 10-15μm, and it can withstand the working pressure and impact pressure on the oil circuit, and the pressure drop should be less than 0.35MPa. At the same time, a safety valve should be installed to prevent clogging of the oil filter.
Installed on the oil return line of the system: this kind of installation plays an indirect filter role. Generally, a back pressure valve is installed in parallel with the filter. When the filter is blocked and reaches a certain pressure value, the back pressure valve opens.
Install on the branch oil circuit of the system.
Separate filter system: Large hydraulic system can be specially equipped with a hydraulic pump and oil filter to form an independent filter circuit.
In addition to the oil filter required by the entire system in the hydraulic system, a special oil filter is often installed in front of some important components (such as servo valves, precision throttle valves, etc.) to ensure their normal operation.
