According to the installation location and function,Hydraulic filter is mainly divided into the followings;

1. Suction filter

   - Installed at the suction port of hydraulic pump to filter large particles of contaminants.

   - Usually has a larger filtration area and lower filtration accuracy to avoid affecting the oil suction performance of the pump.

2. Pressure line filter

   - Installed in the pressure line to protect downstream components (such as valves, cylinders, etc.) 

   - Need to withstand higher system pressure and usually have higher filtration accuracy.

3. Return filter

   - Installed in the return oil line to filter contaminants in the oil returning to the tank.

   - Used to filter particulate matter and wear debris generated during system operation.

4. Bypass filter

   - Independent of the main system, and filters hydraulic oil through a bypass cycle.

   - Usually used for high-accuracy filtration or oil purification.

5. Tank vent filter

   - Installed at the tank vent to prevent external dust and contaminants.

The filtration accuracy of the hydraulic filter is usually expressed in microns (μm), indicating the minimum particle size.

Common filtration accuracy;

   - Low accuracy; 25μm ~ 100μm (for suction filter)

   - Medium accuracy; 10μm ~ 25μm (for pressure line or return filter)

   - High accuracy; 1μm ~ 10μm (for high-accuracy system or bypass filtration)

The filter element material directly affects its filtration performance and service life. Common filter element materials include;

   - Paper filter element; low cost, suitable for general working conditions, but with poor high-temperature and corrosion resistance.

  - Metal mesh filter element; high temperature and corrosion resistance, suitable for harsh environments, but with low filtration accuracy.

   - fiber filter element; high filtration accuracy, suitable for high accuracy systems.

   - Stainless steel filter element; high strength, corrosion resistance, suitable for high-pressure and high-temperature environment.

Hydraulic filters need to be checked and replaced regularly to ensure the performance.

The replacement depends on the working environment, the degree of oil contamination and the type of filter.

Common replacement signals;

   - System pressure drops

   - Hydraulic oil becomes dirty or turbid

   - Filter clogging indicator alarms

   - Blockage; The filter may be clogged with contaminants after long-term use, resulting in a drop in hydraulic system pressure and reduced flow.

   - Oil leakage; If the filter is poorly sealed or damaged, it may cause hydraulic oil leakage.

   - Reduced filtration effect; Aging or damage will cause reduced filtration performance and contaminants to enter the system.

Hydraulic filters are widely used in the following;

   - Construction machinery (such as excavators, bulldozers)

   - Metallurgical equipment

   - Marine hydraulic system

   - Aerospace hydraulic system

   - Industrial production line hydraulic equipment

Accuracy

Materials

Maintenance and replacement

Common faults

Notes