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Time：2025-07-17 13:47:46 Reading volume：
Ordinary oil purifiers (such as those that rely solely on mechanical filtration or centrifugal separation) are usually unable to effectively remove trace amounts of water. The specific reasons and alternatives are as follows:
(1) Technical principle limitations
- Mechanical filtration: can only intercept solid particles (such as metal chips, dust), but water exists in a dissolved or free state and will directly penetrate the filter.
- Centrifugal separation: only effective for large amounts of free water (such as water-oil stratification), almost ineffective for trace amounts of dissolved water (<500ppm) or emulsified water.
(2) Actual effect
- Water content after treatment: may increase instead of decrease (because the oil temperature increases during filtration and the hygroscopicity increases).
- Risks: trace amounts of water (especially dissolved water) will reduce the insulation of the oil (such as the breakdown voltage of transformer oil decreases) and accelerate oxidation.
| Method | Applicable scenarios | Dehydration effect | Cost |
|------------------------|--------------------------------|--------------------------|----------------|
| Vacuum oil filter | Transformer oil, hydraulic oil, etc. | Can be reduced to ≤10ppm | High (equipment investment required) |
| Coalescing separator | Emulsified water (water and oil mixed into emulsion) | Free water→≤100ppm | Medium |
| Adsorption filter | Small flow system (such as lubrication station) | Dissolved water→≤50ppm (frequent replacement required) | Low (consumables cost) |
| Molecular sieve/silica gel adsorption tower | Extremely low water content requirements (such as precision instrument oil) | Can be reduced to ≤5ppm | High |
If professional equipment cannot be used immediately, the following methods can be tried, but it should be noted that the effect is limited and may introduce secondary pollution:
- Standing sedimentation: Store the oil in a sealed container and let it stand for several days. Free water may sink (but it is ineffective for dissolved water).
- Heating evaporation: Heat to 60~80℃ and stir (the temperature must be strictly controlled to avoid oil oxidation).
- Add water absorbent: such as a small amount of dry silica gel (the silica gel powder needs to be filtered and removed later).
- Priority options:
If moisture affects key performance (such as insulating oil withstand voltage value, hydraulic system accuracy), it is recommended to use a vacuum oil filter or a coalescing oil filter directly.
- When the budget is limited:
Choose a combination of "ordinary oil purifier + adsorption filter element" (such as adding a Hy-Pro waterproof filter element).
- Prohibited operations:
Mixing alcohol or other solvents into the oil to "absorb water" (which will destroy the chemical properties of the oil).
After treatment, the moisture content must be tested. Methods include:
- Coulometric method (ASTM D6304): laboratory precise measurement (ppm level).
- Visual method: ｄｒｏｐ the oil sample on a hot plate. If there is a crackling sound, it indicates that there is water (qualitative only).
- Quick detector: portable dew point meter or capacitance sensor (suitable for on-site).
Conclusion: Ordinary oil purifiers cannot reliably remove trace moisture. Professional dehydration equipment must be selected according to the oil type and moisture content. If you need further help, please provide oil type and moisture data!
