What is Transformer Oil Purification Procedure/ Transformer Oil Purification Process ?

This article will introduce transformers, transformer oil aging, the process of oil purifier purification, and introduce YUNENG transformer oil regeneration machine, and more.

Why Purification of Transformer Oil is Required?

What is a Transformer?

A transformer is static electrical equipment used to transform AC voltage and current to transmit AC power. At the same time, power transformers are also necessary equipment for power transmission and distribution and power user distribution.

Transformer oil

Transformer Oil Introduction

What is Transformer Oil?

Transformer oil is a type of mineral oil used in transformers.

It acts as the insulating medium of the transformer so that there is good insulation between the windings and between the windings and the grounded iron core and case. Depending on the voltage level of the transformer, the insulating oil needs to have a certain electrical insulating strength.

At the same time, it is a medium for heat dissipation. Transformer oil transfers the heat from the core and winding operation to the cooling device.

Deterioration of transformer oil

During the operation of the transformer, with the change of time, the transformer oil is contacted with oxygen, and the oil is oxidized to generate various oxides. Or because the temperature is too high, the oil cracks, and the lightning is reduced. In addition, metal particles and dust in the transformer will also pollute the transformer oil. If it is a transformer installed outdoors, it is very likely that rainwater will seep into it if it is poorly protected. These will cause pollution and deterioration of transformer oil.

Deteriorated transformer oil will darken in color, increase in acid value, increase viscosity, decrease flashpoint, decrease electrical properties, and even produce dark brown deposits.

As transformer oil ages and deteriorates over time, it needs to be maintained to ensure uninterrupted power transmission. Transformer oil is essential for the proper function and operation of the transformer.

We can carry out scientific filtration or purification processes for these aged and deteriorated transformer oils. Transformer oil purification removes solid particles, dissolved water, and dissolved gases. We can restore or enhance the physicochemical properties of transformer oil through filtration, dehydration, and degassing processes. Transformer oil purification keeps the transformer in good condition and prolongs its service life.

When do You Need a Transformer Oil Purification Machine?

Transformer oil should be tested regularly. Usually, we determine the condition of the oil by testing the following items:

  • color and appearance
  • Freezing point
  • Viscosity
  • water content
  • interfacial tension
  • Acid value
  • Water solubility pH
  • Oxidative Stability Test
  • Dielectric strength or breakdown voltage (BDV)
  • Flashpoint
  • pour point
  • Volume resistivity
  • dielectric loss
  • Dissolved Gas Analysis (DGA)
  • Sludge Test

If the above test for d exceeds a safe or acceptable value, the transformer oil should be filtered or decontaminated.

Transformer Oil Purification Procedure/Transformer Oil Purification Process

The filtration or purification process of transformer oil is the process of removing sludge, dissolved gases, and dissolved water from the oil. A good transformer oil purification system can provide filtered oil that meets standard specifications. The purification process of transformer oil is as follows:

The following will also introduce some transformer oil purification methods

First step

Transformer oil purification should first raise the oil temperature to the required level. Usually reaches 65 degrees Celsius. There are two benefits to doing this: First, raising the oil temperature will help separate moisture and gases from the oil in the degassing chamber. Second, as the temperature increases, the viscosity of the oil decreases, which will contribute to better filtration.

Second step

The second step in transformer oil purification is to remove sludge from the transformer oil.

There are two ways to remove sludge:

One is to remove sludge through filter candles. If the transformer oil is filtered through the filter candle, there are also two methods. They are filtering with a classic edge filter and filtering with a depth filter.

About the Classic Edge Filter

The advantage of edge filter systems is that they can be cleaned and reused. The disadvantage is that the cleaning and installation of edge filters require experienced staff and take a lot of time and effort.

We now have the option of using filter cartridges instead of edge pack filters, which reduce labor and time investment and are more convenient to use.

The second is to remove sludge by centrifugal action.

Sludge can also be separated from the oil by using a centrifuge. It is often possible to confuse transformer oil filtration with transformer oil centrifugation. Transformer oil centrifugation has little effect on improving oil parameters.

The advantage of centrifugation is that it saves the recurring cost of replacing filter elements. Power-driven centrifuges can remove tiny dirt and sludge and free water but not dissolved water. And the use of electric centrifuges increases the cost of filtration.

Third step

The third step in transformer oil purification is the dehydration and degassing of transformer oil.

The process of dehydration and degassing of transformer oil is carried out in a degassing chamber. It can be carried out under a vacuum by utilizing the difference in the boiling point of water, gas, and transformer oil. Free water can be removed by a powered centrifuge or by the coalescing principle. The coalescing principle is generally more efficient and economical in practice.

Transformer Oil Regeneration Machine

Transformer Oil Regeneration Machine

The YUNENG transformer oil regeneration machine is fully enclosed, weatherproof, and safe to operate.

It integrates low-temperature physical adsorption (including deodorization, decolorization, etc.) purification technology and online regeneration adsorption filter. The processing is simple and fast, the additives in the oil will not be destroyed, and it has functions such as oil quality protection.

Transformer Oil Purification Machine

Transformer Oil Purification Machine


This bipolar transformer oil purification machine is suitable for power transmission and transformation projects from 66KV to 500KV. It can effectively and quickly remove trace moisture, gas, particulate matter, etc. in transformer oil (insulating oil), and improve the performance of transformer oil. Thereby improving the performance of transformers, circuit breakers, transformers, and capacitors with insulation systems.

Note: The transformer oil purification machine is also called the transformer oil centrifuging machine in Bangladesh.

Transformer Oil Dehydration Machine

Transformer Oil Dehydration Machine


This transformer oil dehydration machine produced by YUNENG is developed for new and old transformer oil containing moisture, gas, particles, impurities, and acidic substances. Contaminants such as excess moisture, trace amounts of water, dissolved gases and particulate matter in insulating layers can be effectively and quickly eliminated.

Transformer Oil Purification Vacuum Pump

The startup speed of the transformer oil purification vacuum pumps are fast and the pumping speed is fast. Especially suitable for the installation and maintenance of various large transformers. It can also be used for vacuuming transformers in the substation industry, transformer manufacturing plants, power plants, vacuum metallurgy, pharmaceuticals, paints, welding, electronics and other industries, and can also be used as a backing pump for large vacuum systems.

YUNENG can provide 150m³/h, 500m³/h, 1000m³/h, 2000m³/h and other models, customers can choose or customize according to the specific needs of use.

Get in Touch with YUNENG

As a mature oil purifier manufacturer in China, YUNENG is able to provide transformer oil purification plants, transformer oil regenerators, lube oil purifiers, oil testers, tire oil purifiers, etc. We hope you can contact us anytime you need it.

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