How to filter industrial oil?

Industrial oil filtration is a key step to maintain equipment performance and extend the service life of oil products. It is necessary to ｓｅｌｅｃｔ appropriate filtration methods according to the type of oil (such as hydraulic oil, lubricating oil, gear oil, etc.) and the degree of contamination. The following are the process flow, equipment selection and operation points of industrial oil filtration:

Purpose of industrial oil filtration

1. Remove impurities: metal particles, dust, sludge, etc., to prevent equipment wear.

2. Separate water: avoid emulsification and oxidation of oil products, and protect metal parts from rust.

3. Remove gas: reduce poor lubrication or cavitation of hydraulic systems caused by bubbles.

4. Restore performance: extend the oil replacement cycle and reduce operation and maintenance costs.

Industrial oil filtration methods and equipment

1. Mechanical filtration (removal of solid particles)

- Equipment: plate and frame oil filter, centrifugal oil filter, filter element oil filter.

- Filtration accuracy:

- Coarse filtration: ≥25 μm (for pre-filtration).

- Fine filtration: 1~10 μm (high-precision hydraulic system requires ≤5 μm).

- Applicable oils: lubricating oil, gear oil, hydraulic oil, etc.

2. Vacuum dehydration (removal of moisture and gas)

- Equipment: vacuum oil filter (combined with heating and vacuum evaporation).

- Process parameters:

- Vacuum degree: ≤-0.095 MPa.

- Oil temperature: 50~65℃ (avoid high temperature oxidation).

- Applicable oils: hydraulic oil and transformer oil with severe emulsification.

3. Adsorption purification (removal of colloid and acidic substances)

- Materials: silica gel, activated clay, molecular sieve.

- Application:

- Silica gel: adsorption of trace moisture and acidic substances.

- Activated clay: deep removal of sludge and oxidation products.

- Applicable oils: industrial lubricants with severe aging.

4. Electrostatic filtration (ultrafine particle separation)

- Principle: Use an electrostatic field to adsorb submicron particles (0.1~1 μm).

- Applicable scenarios: Turbine oil and aviation hydraulic oil with high cleanliness requirements.

Industrial oil filtration standards and indicators

| Oil type | Key filtration indicators | Target value |

|--------------|----------------------------------|-------------------------------|

| Hydraulic oil | Particle contamination (ISO 4406) | ≤ISO 15/13/10 (high-voltage system requirements) |

| Gear oil | Moisture content | ≤500 ppm (water content) |

| Lubricating oil | Acid value (TAN) | ≤0.5 mg KOH/g |

| Transformer oil | Breakdown voltage | ≥40 kV (operating oil) |

Operation process (taking hydraulic oil as an example)

1. Pretreatment:

- Sampling and testing (particle count, moisture, acid value).

- Stand for 24 hours to precipitate large particles.

2. Coarse filtration:

- Use a plate and frame oil filter (25 μm filter element) to remove visible impurities.

3. Fine filtration:

- Switch to a cartridge oil filter (5 μm cartridge) or centrifugal oil filter.

4. Dehydration and degassing (optional):

- Vacuum oil filter until the water content is ≤200 ppm.

5. Adsorption purification (aging oil):

- Add silica gel (1%~3%) and filter for 8 hours.

6. Acceptance test:

- Test particle size, water content, and acid value, and re-inject the equipment after meeting the standards.

Precautions

1. Safety protection:

- Prevent burns when filtering oil at high temperature, and ventilate and explode on site.

- Waste oil is treated according to environmental protection standards (GB 17145).

2. Equipment maintenance:

- ｒｅｐｌａｃｅ the filter element regularly (ｒｅｐｌａｃｅ when the pressure difference is ≥0.3 MPa).

- Check the vacuum pump oil monthly to avoid water contamination.

3. Oil compatibility:

- Different types of oils are prohibited from mixing. Confirm the oil base (mineral oil/synthetic oil) before filtering.

Common problems and solutions

| Problems | Causes | Solutions |

|-------------------|------------------------|----------------------------------|

| Slow filtration speed | Low oil temperature, filter element clogged | Heat to 40~60℃, ｒｅｐｌａｃｅ filter element |

| Oil emulsification | High water content | Vacuum dehydration or addition of demulsifier |

| Acid value increases after filtration | Adsorbent failure or oil oxidation | ｒｅｐｌａｃｅ adsorbent and strengthen anti-oxidation measures |

Industrial oil filtration needs to ｓｅｌｅｃｔ appropriate processes according to oil type, pollution degree and equipment requirements.

- Routine maintenance: mechanical filtration + regular inspection.

- Deep treatment: vacuum dehydration + adsorption purification.

- High-precision system: electrostatic filtration or offline filtration system.

Proper filtration can extend the oil life by more than 50% and significantly reduce equipment failure rate.