Hydraulic oil filtration equipment principle

The principle of hydraulic oil filtration equipment is to remove pollutants (such as solid particles, moisture, gas and oxidation products) in the oil by physical or chemical methods to restore the cleanliness and performance of the oil and ensure the stable operation of the hydraulic system. Its core principles can be divided into the following key links:

Physical filtration principle

1.1 Mechanical interception (solid particle removal)

- Filter element/filter material structure: use multi-layer filter screen, fiber filter paper, or sintered metal and other materials to intercept particle pollutants through different pore sizes (such as 1~100 microns).

- Filtration method:

- Surface filtration: large particles are intercepted by the surface of the filter material (such as metal mesh).

- Depth filtration: small particles are adsorbed in the pores inside the filter material (such as a glass fiber filter element).

1.2 Adsorption filtration

- Activated carbon or diatomaceous earth: adsorb colloids, oxides and tiny particles in the oil.

- Magnetic filtration: adsorbs ferromagnetic metal chips through magnetic elements (suitable for oil containing iron wear particles).

Dehydration and degassing principles

1 Vacuum dehydration

- Vacuum flash evaporation: Reduce the pressure in the vacuum tank (usually -0.08 ~ -0.098 MPa) to reduce the boiling point of water, and then discharge it through a vacuum pump after evaporation.

- Condensation separation: The evaporated water vapor is condensed into liquid water by the condenser and then discharged.

2 Coalescing separation (water removal)

- Coalescing filter element: Aggregate tiny water droplets into large droplets, and use the density difference to naturally settle and separate.

- Hydrophilic-oleophobic material: Preferentially adsorbs water and discharges it through a separator.

3 Degassing

- Vacuum degassing: In a vacuum environment, dissolved gas (such as air) escapes from the oil and is extracted.

- Diffusion degassing: Increase the surface area of the oil (such as a film or spray) to accelerate gas release.

Chemical purification principle

- Additive regeneration: Some equipment restores the chemical properties of the oil by adding antioxidants or acid neutralizers.

- Electrostatic adsorption: Use electrostatic fields to adsorb charged colloidal particles (less common, used for high-precision purification).

The working process of a typical hydraulic oil filtration equipment

Take the vacuum oil filter as an example:

1. Coarse filtration: The oil first passes through a 100-micron filter to remove large particles.

2. Heating: The oil temperature rises to 50~70℃ (reduces viscosity and improves dehydration efficiency).

3. Vacuum dehydration and degassing: The oil is sprayed into the vacuum tank, and the water and gas evaporate and separate.

4. Fine filtration: Residual particles are removed through a 1~5 5-micron filter element.

5. Output purified oil: Clean oil returns to the hydraulic system or oil storage tank.

Key performance parameters

- Filtration accuracy: 1~10 microns (NAS 1638 level can reach 6~8).

- Flow range: 10~200 L/min (ｓｅｌｅｃｔ according to system requirements).

- Water content control: ≤100 ppm after treatment (international standard ISO 4406).

- Cleanliness: up to ISO 15/13/10 or higher.

Application scenarios

- Engineering machinery: maintenance of hydraulic systems of excavators and cranes.

- Industrial production lines: circulation purification of hydraulic oil of injection molding machines and die-casting machines.

- Power system: online filtration of hydraulic oil for turbine speed regulation.

- Aerospace: high-precision treatment of hydraulic oil for aircraft landing gear.

Key points for equipment selection

- Oil type: different media such as mineral oil, synthetic oil, or water-ethylene glycol need to match filter materials.

- Pollution level: highly polluted oil requires multi-stage filtration (such as centrifugation before vacuum).

- Explosion-proof requirements: ATEX or GB 3836 certified equipment is required for hazardous environments such as the chemical industry.

- Automation function: Equipment with PLC control can realize unattended operation.

Hydraulic oil filtration equipment efficiently removes pollutants through the coordination of multiple technologies such as mechanical interception, vacuum dehydration, coalescence separation and chemical treatment. Its core goal is to extend the life of the oil, reduce equipment wear, and ensure the reliability of the hydraulic system. Users need to choose a matching filtration solution based on the type of oil contamination (particles, water, gas) and operating conditions (flow rate, temperature).