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Time：2025-05-14 13:16:08 Reading volume：
Detailed explanation of methods and technologies for removing water from oil
Water is one of the most common contaminants in oil (such as lubricating oil, hydraulic oil, transformer oil, etc.), which can cause lubrication failure, equipment corrosion, sludge generation and other problems. The following is an analysis of commonly used oil dehydration technologies in industry and their applicable scenarios.
| Type of water | Characteristics | Hazards |
|--------------|----------------------------------|----------------------------------|
| Free water | Sedimented at the bottom of the oil tank, visible to the naked eye | Accelerates oxidation and breeds microorganisms |
| Emulsified water | Forms a stable emulsion with oil (difficult to separate) | Reduces lubricity and clogs the filter element |
| Dissolved water | Molecular dispersion (usually <500ppm) | Promotes acid value increase and causes metal corrosion |
(1) Physical sedimentation method
- Principle: Use density difference to naturally precipitate free water.
- Equipment: static oil tank, sedimentation separation tank.
- Advantages: zero cost, simple and easy.
- Disadvantages: only applicable to free water, time-consuming (requires 24-48 hours), unable to handle emulsified/dissolved water.
- Applicable scenarios: rough dehydration pretreatment.
(2) Vacuum dehydration technology
- Principle: lower the boiling point of water in a vacuum environment, evaporate water and then condense and collect.
- Key parameters:
- Vacuum degree: usually <-0.09MPa (absolute pressure <10kPa)
- Temperature: 60-80℃ (avoid oil oxidation)
- Equipment: vacuum oil filter (such as transformer oil).
- Advantages:
- Can remove free water, emulsified water, and dissolved water at the same time (water content can be reduced to <50ppm).
- Remove gases (such as air, acetylene).
- Disadvantages: high energy consumption, regular maintenance of the vacuum pump is required.
- Applicable scenarios: deep dehydration of turbine oil, transformer oil, and hydraulic oil.
(3) Coagulation separation technology
- Principle:
1. Coagulation stage: Special filter materials make tiny water droplets merge into large droplets.
2. Separation stage: hydrophobic membrane blocks oil from passing through, and free water settles and is discharged.
- Equipment: Coagulation dehydration oil filter (such as aviation fuel, hydraulic system).
- Advantages:
- High efficiency demulsification (can handle emulsified water).
- No heating required, energy saving.
- Disadvantages: Ineffective for dissolved water, must be used with vacuum equipment.
- Applicable scenarios: gear oil and cutting fluid with severe emulsification.
(4) Centrifugal separation method
- Principle: high-speed rotation (≥ 5000 rpm) generates centrifugal force to separate water and oil of different densities.
- Equipment: centrifugal oil filter.
- Advantages:
- No filter material consumption, suitable for highly polluted oil.
- Can handle high viscosity oil (such as rolling oil).
- Disadvantages:
- Unable to remove dissolved water.
- Loud noise and complex maintenance.
- Applicable scenarios: pretreatment of ship engine oil and industrial gear oil.
(5) Adsorption dehydration method
- Principle: Use water-absorbing materials (molecular sieves, silica gel, activated alumina) to physically adsorb water.
- Equipment: portable adsorption filter truck, drying tower.
- Advantages:
- Suitable for trace water removal (can reduce dissolved water to <20ppm).
- The equipment is small and suitable for online purification.
- Disadvantages:
- The adsorbent needs to be replaced frequently (high cost).
- Dust pollution may be introduced.
- Applicable scenarios: precision instrument lubrication system, small hydraulic station.
| Water problem | Recommended solution | Expected effect |
|----------------------|------------------------------|------------------------------|
| Large amount of free water | Sedimentation + centrifugal separation | Water content reduced to below 0.1% |
| Stubborn emulsified water | Coagulation separation + vacuum dehydration | Demulsification + water content <100ppm |
| Trace dissolved water | Vacuum dehydration or adsorption method | Water content <50ppm |
| High viscosity oil with water | Heating centrifuge or vacuum oil filter | Efficient dehydration after viscosity reduction |
1. Temperature control:
- Heating temperature ≤80℃ to avoid oil oxidation (transformer oil recommended ≤65℃).
2. System compatibility:
- Check the equipment sealing material (such as nitrile rubber is not resistant to synthetic ester oil).
3. Moisture detection:
- Use a Karl Fischer moisture meter (accuracy ±10ppm) or an online sensor.
4. Safety protection:
- Choose Ex-certified equipment for explosion-proof environments (such as the petrochemical industry).
The selection of dehydration technology requires comprehensive consideration of water form, oil characteristics, treatment efficiency and cost. For key equipment (such as turbines and transformers), it is recommended to use a vacuum + coalescence combination process to achieve deep purification. Regular monitoring of oil moisture content (ISO 4406 standard is recommended) is an effective means to prevent lubrication failures.
