How much should the transformer oil filter be heated to?

When filtering transformer oil, heating temperature is a key parameter that directly affects the dehydration, degassing and impurity removal effects. Generally, the heating temperature needs to be determined comprehensively based on the properties of the oil, the type of equipment and the degree of contamination. The specific range is as follows:

1. Conventional heating temperature range

- General standard:

- 50~70℃ (common range):

- Applicable to most vacuum oil filters or pressure oil filters.

- Balance dehydration efficiency and oil thermal aging risk.

- Extreme temperature:

- Maximum does not exceed 80℃ (to avoid oil oxidation or chemical degradation).

- Basis:

- Too low temperature (<50℃): slow evaporation of water and low degassing efficiency.

- Too high temperature (>80℃): accelerated oil oxidation, generating colloid or acidic substances.

2. Temperature requirements for different equipment types

| Equipment type | Recommended temperature | Function description |

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

| Vacuum oil filter | 60~70℃ | Promote water evaporation and remove it efficiently in a vacuum environment. |

| Pressure oil filter | 50~60℃ | Reduce oil viscosity and improve filtration fluidity. |

| Coalescing and separation oil filter | 40~50℃ | Avoid high temperature from damaging the structure of the coalescing material. |

| Adsorption regeneration device | 50~65℃ | Enhance the ability of the adsorbent to capture acidic substances. |

3. Adjustment for special working conditions

- Oil with high water content:

- Can be heated to 65~70℃ for a short time (accelerate water evaporation), but it needs to be combined with high vacuum (such as ≤0.1 kPa).

- High viscosity oil (such as a low temperature environment):

- Appropriately increase to 60~65℃ to reduce viscosity for easy filtration.

- New oil treatment:

- Maintain 50~60℃ to avoid unnecessary thermal stress.

4. Precautions

- Temperature uniformity: Ensure uniform oil temperature during heating to avoid local overheating.

- Temperature control accuracy: Use a temperature control system (such as PID adjustment), and the fluctuation range is recommended to be ±5℃.

- Safety limits:

- Flash point requirements: The heating temperature must be at least 20℃ lower than the oil flash point (usually the transformer oil flash point ≥140℃).

- Oxidation risk: Long-term operation at >70℃ requires monitoring of acid value and dielectric loss.

5. Operation suggestions

1. Pretreatment detection: First, measure the moisture and acid value in the oil, and then determine the heating parameters.

2. Step heating: Initial low temperature (40℃) cycle, gradually increase to the target temperature.

3. Real-time monitoring:

- Online monitoring of oil temperature, vacuum, and water content (such as a dew point meter).

- After filtration, check the breakdown voltage (≥50 kV) and moisture content (≤10 ppm).

Example process (vacuum oil filter)

1. Start the equipment and raise the oil temperature to 60℃.

2. Turn on the vacuum system and maintain the vacuum degree ≤0.5 kPa.

3. Circulate and filter until the moisture content is ≤5 ppm and the particle size is ≤NAS level 6.

Reasonable control of the heating temperature can significantly improve the filtration efficiency and protect the oil's life.