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Time：2025-04-16 10:54:47 Reading volume：
The transformer oil dehydration system is mainly used to remove moisture from oil to restore or maintain the insulation performance and chemical stability of the oil. Common dehydration technologies can be divided into physical separation methods, adsorption methods and chemical methods. The specific system types are as follows:
Principle: Use vacuum negative pressure to lower the boiling point of water, supplemented by heating (usually 50~70℃) to evaporate and separate water.
Core equipment:
- Vacuum pump: Create a high vacuum environment (residual pressure can be as low as 50Pa or less).
- Heating device: Preheat the oil to improve the efficiency of water evaporation.
- Atomization/thin film evaporator: Increase the contact area between oil and vacuum (such as spray tower or packing tower).
- Condenser: Collect evaporated water vapor to prevent backflow.
Features:
- High efficiency dehydration (can reduce moisture to below 10 ppm).
- Synchronous removal of dissolved gases (such as oxygen).
- Suitable for large-scale treatment (such as transformer on-site oil filtration).
Principle: Separate free water and solid impurities (density difference) in oil through high-speed centrifugal force.
Equipment: High-speed centrifuge (such as a disc centrifuge).
Features:
- It has a significant effect on free water (>100ppm), but is ineffective for dissolved water.
- It is often used as a pretreatment and combined with vacuum dehydration.
Principle: Use porous adsorption materials to directly absorb water in oil.
Commonly used adsorbents:
- Molecular sieves (such as 3A, 4A): selectively adsorb water molecules.
- Silica gel: low cost, but needs to be replaced regularly.
- Activated alumina: takes into account the adsorption of both water and acidic substances.
Equipment form:
- Fixed bed adsorption tower: oil flows through the adsorbent layer (needs to be regenerated or replaced regularly).
- Online adsorption filter element: integrated in the oil filter for easy replacement.
Features:
- Suitable for deep removal of trace moisture (can be reduced to below 5ppm).
- Adsorbent needs to be regenerated (heating or vacuum desorption).
Principle: Use a hydrophilic membrane (such as polyimide) to selectively permeate water molecules to achieve oil-water separation.
Features:
- No heating required, low energy consumption.
- Suitable for small flow and high-precision dehydration (laboratory or precision equipment).
Principle: Use a coalescing filter element to merge tiny water droplets in oil into large droplets, and then separate them by gravity or centrifugation.
Equipment: Coalescing filter + separation tank.
Features:
- Good treatment effect on emulsified water (such as oil-in-water type).
- Commonly used in fuel oil or lubricating oil, less commonly used in transformer oil.
Principle: Utilize the oil temperature change when the transformer is running, and circulate the oil through the adsorbent (such as silica gel) tank through the thermosyphon effect.
Features:
- No additional power is required, and trace moisture is continuously adsorbed.
- Commonly used in old transformer designs.
Selection basis
- Moisture content: Vacuum dehydration is preferred for high moisture (> 100 ppm), and adsorption is used for trace moisture.
- Processing speed: The Vacuum system is suitable for large flow, and the membrane separation is suitable for small flow precision processing.
- Comprehensive requirements: If simultaneous degassing and deacidification are required, ｓｅｌｅｃｔ a vacuum + adsorption combination system.
Precautions
- After dehydration, the oil dielectric strength (≥60kV/2.5mm) and moisture content (≤15ppm, depending on the standard) need to be tested.
- Avoid excessive heating (oil temperature ≤80℃) to prevent oil oxidation.
- The adsorbent needs to prevent oil contamination, and the molecular sieve needs to be activated before use.
These systems can be used individually or in combination, depending on the degree of oil degradation and equipment operating conditions.
