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Time：2025-04-27 11:35:08 Reading volume：
Water pollution in industrial oil will seriously affect the lubrication, insulation performance and oil life of equipment, and targeted filtering technology is required. The following are common filtering methods and applicable scenarios for water in industrial oil:
| Form | Characteristics | Hazards |
|----------------|----------------------------------|----------------------------------|
| Free water | Sedimented at the bottom of the oil tank, visible to the naked eye | Accelerate oxidation and breed bacteria |
| Emulsified water | Forms a stable emulsion with water (difficult to separate) | Reduces lubricity and corrodes metal parts |
| Dissolved water | Trace amounts dissolved in oil (<100ppm) | Long-term acidification of oil products and reduced insulation performance |
- Principle: Use density difference to naturally precipitate free water.
- Equipment: sedimentation tank, water separation tank.
- Applicable: Oil with high water content (>1%) and high viscosity (such as gear oil).
- Disadvantages: time-consuming, unable to remove emulsified/dissolved water.
- Principle: high-speed centrifugal force separates water and oil (density difference).
- Equipment: disc centrifuge, tubular centrifuge.
- Applicable: free water and emulsified water in turbine oil and hydraulic oil.
- Advantages: large processing capacity (up to 5,000L/h), no filter material required.
- Limitations: ineffective for dissolved water, regular slag discharge is required.
- Principle: heating the oil under negative pressure, condensing and discharging the water after evaporation.
- Equipment: vacuum oil filter (standard vacuum pump, condenser).
- Applicable: transformer oil, turbine oil and other oils that require high dryness (can be reduced to below 10ppm).
- Key parameters: vacuum degree (≤-0.095MPa), temperature (60-70℃).
- Principle:
- Coalescing filter element: gathers tiny water droplets into large water droplets.
- Separation filter element: Use hydrophobic materials to block water droplets from returning to the oil.
- Equipment: Coalescing oil filter (such as Pall, HYDAC brand).
- Applicable: emulsified water in aviation fuel and hydraulic oil (≤ 100 ppm after treatment).
- Principle: porous materials (molecular sieves, silica gel) adsorb water.
- Equipment: adsorption oil filter vehicle, offline filtration system.
- Applicable: trace dissolved water (such as insulating oil regeneration).
- Disadvantages: adsorbents need to be replaced frequently, and the cost is high.
- Principle: Selective permeable membranes separate water molecules (such as reverse osmosis membranes).
- Applicable: high-value oil products (such as synthetic lubricants).
- Advantages: high accuracy (up to 1 ppm), no thermal damage.
| Oil type | Recommended method | Target water content |
|----------------|-------------------------------|---------------------|
| Transformer oil | Vacuum oil filter + adsorbent | ≤10ppm (IEC 60422) |
| Hydraulic oil | Coalescing separation + vacuum dehydration | ≤200ppm (ISO 4406) |
| Turbine oil | Centrifuge + vacuum dehydration | ≤50ppm |
| Gear oil | Sedimentation separation + centrifuge | ≤500ppm |
| Fuel oil | Coalescing filter (such as ship fuel system) | ≤0.05% |
1. Temperature control: Heating temperature ≤70℃ to avoid oil oxidation.
2. Staged treatment: Oil with high water content should be first settled/centrifuged and then vacuum dehydrated.
3. Real-time monitoring: Use a moisture sensor (such as a Karl Fischer titrator).
4. System compatibility: The coalescing filter element must match the oil viscosity (ISO VG 32-68).
By properly selecting dehydration technology, the oil life can be extended by 3-5 times and the risk of equipment corrosion (such as bearing pitting and servo valve jamming) can be reduced.
