According to the filtration accuracy, the oil filter can be divided into: coarse filter, ordinary filter, precision filter, and special precision filter. Their filtration efficiency is 100μm, 10～100μm, 5～10μm and 1-5μm, so it is said. In the purchase of oil filter is to buy the right product according to demand, prevent the purchase of products can not be used, pay attention to the following points:

 

(1) The filtering accuracy should meet the predetermined requirements.

 

(2) It can maintain sufficient flow capacity for a long time.

 

(3) The filter core has sufficient strength and is not damaged by the action of hydraulic pressure.

 

(4) The filter core has good corrosion resistance and can work continuously at the specified temperature.

 

(5) The filter is easy to clean or replace.

 

Therefore, the oil filter should be selected according to the technical requirements of the hydraulic system according to the conditions of filtration accuracy, flow capacity, working pressure, oil viscosity, working temperature and so on.

 

2. The installation position of the oil filter in the hydraulic system usually has the following types:

 

(1) The surface type oil filter is generally installed on the suction line of the pump at the suction port of the pump. The purpose is to filter out the large impurity particles to protect the hydraulic pump. In addition, the filter capacity of the oil filter should be the pump flow. More than twice the pressure loss is less than 0.02 MPa.

 

(2) Installed on the pump's outlet oil line: The purpose of installing the oil filter here is to filter out contaminants that may invade components such as valves. The filtration precision should be 10-15 μm, and it can withstand the working pressure and impact pressure on the oil circuit, and the pressure drop should be less than 0.35 MPa. A safety valve should also be installed to prevent the oil filter from becoming clogged.

 

(3) Installed on the return line of the system: this installation serves as an indirect filter. A back pressure valve is generally installed in parallel with the filter, and when the filter is blocked to a certain pressure value, the back pressure valve is opened.

 

(4) Installed on the system branch oil circuit.

 

(5) Separate filtration system: Large hydraulic system can be equipped with a hydraulic pump and oil filter to form an independent filtration circuit. In addition to the oil filter required for the entire system, the hydraulic system often installs a dedicated fine oil filter in front of some important components (such as servo valves, precision throttle valves, etc.) to ensure their normal operation.