How to filter industrial oil most cleanly?

To make industrial oils (such as lubricating oil, hydraulic oil, transformer oil, etc.) as clean as possible, it is necessary to adopt a multi-stage purification process based on the type of oil contamination (water, particles, colloids, oxidation products, etc.), and combine physical, chemical and adsorption methods. The following is the most thorough industrial oil purification solution:

Main types of industrial oil pollution

| Pollutants | Impact | Common sources |

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

| Moisture | Accelerated oxidation, reduced lubricity, corrosion | Condensate, leakage, cleaning process |

| Solid particles | Equipment wear, valve core jamming | Metal chips, dust, sludge |

| Colloid/sludge | Blockage of filter element, oil line adhesion | Oil aging, high temperature oxidation |

| Acidic substances | Corrosion of metal, reduction of insulation performance (transformer oil) | Oxidation products, decomposition of additives |

The cleanest industrial oil treatment solution

(1) Pretreatment: Remove large particles and free water

- Sedimentation separation: Let the oil stand for 24 to 48 hours to allow large particles and water to settle naturally.

- Coarse filtration (30~100µm): Use a plate and frame oil filter or a metal mesh filter to remove large particles.

- Centrifugal separation (optional):

- Disc centrifuge (5,000~15,000 G) removes free water and particles >1µm.

- Tubular centrifuge (ultra-high speed, 30,000 RPM) to treat emulsified water.

(2) Deep dehydration: Remove dissolved water and trace water

- Vacuum oil filter (best choice):

- Heat the oil at 50~70℃ and evacuate to ≤5 mbar to evaporate the water.

- After treatment, the water content can be reduced to ≤10 ppm (by ISO 4406).

- Coalescing separation oil filter (for emulsified water):

- First, coalesce small water droplets and then separate them through hydrophobic filter media.

(3) Fine filtration: remove tiny particles

- High-precision filter element (β≥200):

- 1~3µm (hydraulic oil, turbine oil)

- 3~5µm (gear oil, lubricating oil)

- Electrostatic oil filtration technology (optional):

- Used to remove 0.1µm colloidal particles (such as transformer oil).

(4) Adsorption purification: remove colloids and acidic substances

- Activated alumina/silica gel adsorption:

- Reduce acid value (TAN) and dielectric loss (tanδ).

- Fuller’s Earth (activated white clay):

- Adsorb sludge and colloids, suitable for waste oil regeneration.

- Ion exchange resin (high-end application):

- Deeply remove polar pollutants (such as transformer oil).

(5) Chemical treatment (optional)

- Add antioxidant (such as T501): Delay oil oxidation.

- Demulsifier (such as T1001): Improve oil-water separation performance.

Optimal purification solutions for different industrial oils

| Oil type | Key pollutants | Recommended purification process |

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

| Hydraulic oil | Particles, moisture | Vacuum oil filter + 3µm high-precision filtration + adsorbent |

| Transformer oil | Moisture, gas, acid | Vacuum oil filter + electrostatic filtration + silica gel adsorption |

| Gear oil | Metal chips, colloid | Centrifugal separation + 10µm filtration + activated clay regeneration |

| Turbine oil | Micro-water, particles | Coagulation and dehydration + 1µm filtration + antioxidant treatment |

| Waste lubricating oil | Sludge, acidic substances | Centrifugal + clay adsorption + distillation regeneration (such as waste oil regeneration plant) |

Testing standards (oil products should reach after treatment)

- Moisture: ≤50 ppm (ISO 4406)

- Cleanliness: ≤NAS 1638 Class 6 (or ISO 15/13/11)

- Acid value (TAN): ≤0.1 mg KOH/g (new oil standard)

- Dielectric loss (tanδ) (transformer oil): ≤0.005 (90℃)

Maintenance recommendations

- Online monitoring: Install particle counters and moisture sensors to monitor oil quality in real time.

- Regularly ｒｅｐｌａｃｅ filter elements: High-precision filter elements (such as 3µm) are recommended to be replaced every 500~1000 hours.

- Avoid overheating: Heating temperature ≤70℃ to prevent secondary oxidation of oil.

The cleanest method for industrial oil treatment is "multi-stage combined purification":

1. Physical separation (centrifugation, filtration) → 2. Deep dehydration (vacuum/coagulation) → 3. Finally, adsorption purification (silica gel/kaolin).

For key equipment (such as steam turbines and transformers), it is recommended to use a full-process purification system to ensure that the oil quality is close to the new oil standard.