Method for filtering impurities from industrial lubricating oil

The method of filtering impurities in industrial lubricating oil needs to be selected according to the type of impurities (solid particles, moisture, colloid, etc.), oil characteristics and cleanliness requirements. The following is a systematic solution:

Matching filtration technology by impurity type

1. Solid particle filtration

- Method:

- Mechanical filtration: Use filter elements (cellulose, glass fiber, metal mesh) to intercept particles with an accuracy of 1~50μm.

- Magnetic filtration: Add a strong magnetic bar or magnetic filter to absorb iron filings (suitable for gear oil and rolling oil).

- Equipment examples:

- Offline: Plate and frame oil filter, high-precision filter cart (such as PallPFC series).

- Online: Pipeline filter (with pressure difference alarm).

2. Water separation

- Method:

- Vacuum dehydration: 60~70℃ heating + high vacuum (≤5Pa) to evaporate water (preferred for transformer oil).

- Coalescing separation: Coalescing filter element merges water droplets, and hydrophobic filter element blocks water from passing (applicable to turbine oil).

- Centrifugal separation: high-speed centrifuge to throw out free water (commonly used in ship lubricating oil).

3. Gel/sludge treatment

- Methods:

- Adsorption purification: activated clay and silica gel adsorb colloid (requires subsequent fine filtration to remove residual adsorbent).

- Electrostatic oil purification: high-voltage electrostatic field causes colloid to precipitate (suitable for high-viscosity lubricating oil).

Key equipment and technical parameters

|          Technology           |    Applicable impurities    |                  Accuracy/effect                       |  Typical equipment  |

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

| Vacuum oil filter            | Water, gas, light particles | Moisture ≤10ppm, NAS 1638 level 6       | ZJD-50 (domestic)  |

| Centrifugal oil filter       | Water, metal chips            | Free water removal rate > 90%                | Alfa Laval MOPX     |

| Coalescing dehydrator  | Emulsified water               | Moisture ≤100ppm                                  | Hifi Filter DU series |

| Electrostatic oil purifier | Gel, oxide                          | Oil sludge reduction of more than 80%   | CJC HDU series       |

Operation specifications and precautions

1. Pretreatment test:

- Test moisture (ASTM D6304), particle count (ISO 4406), acid value (ASTM D664).

2. Temperature control:

- The oil temperature should be kept at 40~60℃ during filtration (viscosity affects filtration efficiency).

3. Filter element replacement standard:

- Pressure difference > 0.3MPa or use time > 200 hours.

4. Environmental protection treatment:

- Waste filter elements should be treated as hazardous waste (professional recycling is required when heavy metals are contained).

Maintenance and cost optimization suggestions

- Online monitoring: Install particle sensors (such as Pall Ultra monitors) for real-time warning.

- Combined filtration: coarse filtration (to protect equipment) + fine filtration (to meet standards) in stages to extend the life of the filter element.

- Recycling: Severely contaminated oil can be treated with bleaching clay first, and then supplemented with additives (saving 30%~50% of costs).