The so-called oil filter generally refers to a filtering device for filtering hydraulic oil. It is generally composed of a housing and a filter element.
According to the material of the filter element, it can be divided into paper filter oil filter, chemical fiber filter oil filter, glass fiber filter oil filter, stainless steel filter oil filter and so on.
According to the structural form, it can be divided into a net type oil filter, a line gap type oil filter, a folded filter type oil filter, a sintered type oil filter, a magnetic oil filter, and the like.
According to the position where the oil filter is placed, it can also be divided into an oil suction filter, a pipeline oil filter and a return oil filter. Considering the self-priming performance of the pump, the oil suction filter is generally a coarse filter.
The hydraulic oil often contains particulate impurities, which will cause the wear of the hydraulic components relative to the moving surface, the slippage of the spool, and the blockage of the orifice, which greatly reduces the reliability of the system. Installing a certain precision oil filter in the system is a necessary means to ensure the normal operation of the hydraulic system. The filter accuracy of the oil filter refers to the size of the smallest impurity particles that can be filtered by the filter element. It is expressed in micrometers and can be divided into coarse oil filter (80 micron to 250 micron) ordinary oil filter according to accuracy (10 micron-40). Micron), fine oil filter (3 microns - 5 microns), special oil filter (1 micron).
Generally, the basic requirements for the oil filter are: (1) It can meet the filtration system accuracy requirements of the hydraulic system, that is, it can block impurities of a certain size from entering the system. (2) The filter element should have sufficient strength and will not be damaged by pressure. (3) The flow capacity is large and the pressure loss is small. (4) Easy to clean or replace the filter element.
Type characteristics:
Net filter
The net type oil filter has a filter mesh made of copper mesh or stainless steel mesh, and is surrounded by a plastic or metal cylindrical frame with a lot of holes around it, and is coated with one or two layers of copper mesh, and the filtering precision depends on copper. The number of mesh layers and the size of the mesh. The oil filter has the advantages of simple structure, large flow capacity, convenient cleaning, but low filtration precision, and is generally used for the oil suction port of the hydraulic pump.
2. Line gap type oil filter
The line gap type oil filter is formed by tightly winding a steel wire or an aluminum wire around the cylindrical frame to form a filter element, and the small gap between the copper wires is used to filter out impurities mixed in the liquid. The utility model has the advantages of simple structure, large flow capacity, high filtration precision than the net type oil filter, but is not easy to clean, and is mostly a return oil filter.
3. Paper oil filter
The paper oil filter has a paper core made of plain or corrugated phenolic resin or wood pulp microporous filter paper, and the paper core is wrapped around a skeleton made of perforated tinplate to increase the strength. In order to increase the filtration area, the paper core is generally formed into a folded shape. The filter has high precision and is generally used for fine filtration of oil, but it cannot be cleaned after clogging, and the filter element must be replaced frequently.
4. Sintered oil filter
In the sintered oil filter, the filter element is sintered by metal powder, and the micropores between the particles are used to block the passage of impurities in the oil. The filter element can withstand high pressure, good corrosion resistance and high filtration precision, and is suitable for high pressure and high temperature hydraulic systems requiring fine filtration.
installation:
(1) The oil suction strainer at the inlet of the pump is used to protect the pump from inhaling large mechanical impurities. According to the requirements of the pump, a coarse or normal precision oil filter can be used to prevent the oil absorption performance of the pump from being affected. Cavitation, the filter capacity of the oil filter should be more than twice the pump flow, and the pressure loss should not exceed 0.01~0.035MPa.
(2) High-pressure oil filter on the oil outlet of the pump. This installation is mainly used to filter out the pollution impurities entering the hydraulic system. Generally, the oil filter with filtration accuracy of 10~15mm is used. It should be able to withstand the working pressure and impact pressure on the oil circuit, the pressure drop should be less than 0.35MPa, and there should be a safety valve or blocked state signaling device to prevent pump overload and filter damage.
(3) The low-pressure oil filter on the system returning oil can filter out the pollutants before the oil flows into the fuel tank to provide clean oil for the hydraulic pump. Because the return line pressure is very low, the fine oil filter with low filter strength can be used, and the oil filter has a large pressure drop.
(4) Bypass filtration system installed outside the system The large hydraulic system can be specially equipped with a filter system composed of a hydraulic pump and an oil filter to filter out impurities in the oil to protect the main system. When installing the oil filter, please note that the general oil filter can only be used in one direction, that is, the inlet and outlet are not interchangeable.
Advantages and disadvantages:
The oil suction filter is generally installed at the oil suction port of the oil pump to protect the oil pump and other hydraulic components to avoid inhalation of contaminated impurities, and can effectively control the cleanliness of the hydraulic system.
The oil return filter is used for oil system oil return filtration, filtering metal particles generated in the hydraulic system due to component wear, and pollutants generated by the heart seal, so that the oil flowing back to the oil tank is kept clean.