Transformer Oil Purification Machines: Understanding the Procedures and Processes

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

Why Transformer Oil Purification Machine 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.

What are Transformer Oil Purification Procedures and Processes?

Maintaining the integrity and performance of transformer oil is crucial for optimal transformer operation. Contaminants like sludge, dissolved gases, and water can significantly impact the oil’s insulating and cooling properties, leading to reduced efficiency, increased risk of electrical breakdown, and shortened transformer lifespan. To address these concerns, transformer oil purification procedures are employed.

1. Preheating: Initiating the Refining Process

The initial step in transformer oil purification involves preheating the oil to a designated temperature, typically around 65°C. This preheating serves two critical functions:

  • Enhanced Separation: The elevated temperature facilitates the separation of dissolved moisture and gas molecules from the oil within the degassing chamber. Higher kinetic energy promotes the release of these impurities by lowering their solubility.
  • Improved Filtration: As the temperature increases, the oil’s viscosity decreases. This reduced viscosity translates to enhanced flow characteristics, optimizing the efficiency of subsequent filtration stages.

2. Sludge Removal: Eliminating Contaminants

Sludge, a detrimental by-product of oxidation and degradation, must be effectively removed to maintain optimal oil performance. Two primary methods achieve this:

a) Filtration Systems

  • Classic Edge Filters: These traditional filters utilize reusable fabric bags that trap larger sludge particles. While cost-effective, they require experienced personnel and substantial effort for cleaning and reinstallation.
  • Depth Filters: Offering an alternative, depth filters consist of pleated media with varying pore sizes to capture progressively smaller sludge particles. These cartridges boast convenient disposal and replacement, simplifying maintenance.

b) Centrifugation

High-speed centrifugation offers another approach for separating sludge but primarily targets suspended particulate matter (free water, large dirt particles) and has limited impact on dissolved impurities. While it eliminates the recurring cost of filter replacements, centrifuges may increase operational costs due to electricity consumption.

3. Dehydration and Degasing: Purifying to Perfection

The final stage in transformer oil purification focuses on eliminating dissolved water and gas molecules. This typically occurs within a dedicated degassing chamber under vacuum conditions. The principle leverages the disparity in boiling points between water, gas, and transformer oil.

  • Moisture Removal: Free water can be efficiently separated through two methods: a powered centrifuge or the coalescing principle. Powered centrifuges offer high removal efficiency but are energy-intensive. The coalescing principle utilizes media surfaces to induce water droplets to merge and form larger droplets, facilitating easier separation. This method proves more economical and practical in most scenarios.
  • Gas Removal: Vacuum pumps facilitate the efficient extraction of dissolved gases from the oil. This improves the dielectric strength and breakdown voltage of the oil, minimizing the risk of electrical arc discharge within the transformer.

By comprehensively addressing these crucial stages, transformer oil purification systems ensure the continued reliable and efficient operation of these critical electrical components.

Transformer Oil Regeneration Machine

You can click here: Learn more about the transformer oil filtration process & transformer oil filtration procedure.

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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