What is the method of centrifugal separation of transformer oil?

Centrifugal separation of transformer oil is a purification method that uses mechanical centrifugal force to remove water, solid impurities and aging products from the oil. It is suitable for treating oil products with high water content or particle contamination. The following are the specific steps, technical points and precautions of this method:

Principle of centrifugal separation

The centrifugal force generated by high-speed rotation (usually 5000~15000 times the gravity of the oil) makes the impurities, such as water, metal particles, and colloids with higher density in the oil gather on the outer wall of the centrifuge drum, while the clean oil is discharged from the center to achieve layered purification.

2. Operation process

1. Pretreatment

- Filter coarse particles: First, remove large particle impurities through a 5~10μm filter to prevent clogging of the centrifuge.

- Heating the oil: Raise the oil temperature to 50~60℃ (not more than 70℃) to reduce the viscosity of the oil and improve the separation efficiency.

2. Centrifuge settings

- Speed adjustment: Set the speed according to the degree of oil pollution (usually 8000~15000 rpm), and increase the speed when the pollution is serious.

- Separation disc spacing: Adjust the disc spacing in the drum (0.5~1mm) to affect the separation accuracy.

- Flow control: The oil flow rate is usually 100~500L/h. Highly polluted oil needs to reduce the flow rate to extend the separation time.

3. Operation separation

- Start the centrifuge, slowly inject oil, and observe the accumulation of impurities at the slag outlet.

- Regularly stop the machine to clean the mud deposited in the drum (once every 2~4 hours, depending on the degree of pollution).

4. Post-processing

- Detect oil quality: Use a dielectric strength tester (breakdown voltage ≥50kV/2.5mm) and a moisture tester (target ≤15ppm).

- Add antioxidants: If the oil is aged, add additives such as T501 (2,6-di-tert-butyl-p-cresol)

Key technical points

1. Temperature control

- When the oil temperature is below 40℃, the separation efficiency decreases significantly, and the temperature needs to be maintained by electric heating or steam heating.

- High temperature may accelerate oil oxidation, and it is necessary to avoid exceeding 70℃.

2. Centrifuge selection

- It is recommended to use a disc centrifuge (such as Alfa Laval, Westfalia brand), with a processing capacity of up to 2000L/h.

- If it contains a large amount of metal debris, choose a model with a self-cleaning function.

3. Parameter optimization

- Separation factor (Z value): Z (rω²)/g, it is recommended that Z≥8000 (r is the drum radius, ω is the angular velocity).

- Residence time: The oil residence time in the centrifuge must be greater than 2 minutes to ensure sufficient separation.

Applicable scenarios and limitations

- Advantages: The removal rate of free water, metal dust, and fiber impurities is greater than 95%, and no filter element is required.

- Limitations:

- Unable to remove dissolved water (need to be combined with vacuum dehydration);

- Poor treatment effect on colloidal particles (<1μm);

- High energy consumption (average power consumption 0.5~1.2 kWh/m³).

Safety and Maintenance

1. Safe Operation

- The centrifuge must be fixed on the foundation to prevent accidents caused by high-speed vibration.

- Before shutting down, the oil inlet valve must be closed and the residual oil must be drained by idling for 2 minutes.

2. Equipment Maintenance

- Clean the drum and disc every week and check the bearing lubrication (use high-temperature lithium-based grease).

- Regularly calibrate the speed sensor, and the error must be controlled within ±2%.

Combined application with other methods

- Combined process:

Centrifugal separation → Vacuum dehydration (dissolved water treatment) → Precision filtration (colloid removal)

- Economic comparison:

- Centrifugal method: suitable for treating large amounts of highly polluted oil, low operating cost (about ￥0.3~0.8/L);

- Oil filter: suitable for low-polluted oil, high consumables cost (filter element ￥200~800/piece).

By reasonably adjusting parameters and regular maintenance, centrifugal separation can restore the withstand voltage value of transformer oil to more than 90% of the new oil standard, extending the service life of the oil by 3~5 years. For severely emulsified oil, it is recommended to demulsify (add polyether demulsifier) before centrifugal treatment.