Transformer Oil Restoration

Transformer oil restoration is one of the most practical ways to enable its reuse. Therefore, the widespread development and implementation of effective technologies for waste transformer oil regeneration are an important part of resource-saving and energy-efficiency improvement programs in the fuel and energy sector.

Aging or deterioration of insulating oil is typically associated with oxidation. When oxygen and water are present in the oil, oxidation occurs even under relatively favorable operating conditions. The performance of insulating oil is also affected by contaminants originating from solid insulation and other materials that dissolve into the oil. Chemical reactions between unstable hydrocarbons, oxygen, and catalysts such as moisture and dissolved gases lead to oil oxidation. Moisture accumulation significantly accelerates the aging process.

Timely moisture removal and maintenance of low moisture levels in the insulation are therefore critical for preserving the performance of oil and extending the service life of transformer insulation.

Understanding the acid number

The acid number is defined as the amount of potassium hydroxide (KOH), expressed in milligrams, required to neutralize all free acids present in one gram of oil. This parameter provides valuable insights into the oil aging process and its potential impact on transformer performance.

New transformer oil has a very low acid number, typically around 0.03 mg KOH/g, indicating a minimum content of acidic compounds. However, over time, due to exposure to oxygen, moisture, and thermal stress, the oil undergoes oxidation, leading to the formation of acidic by-products. As the acid number increases, the ability of oil to provide effective insulation and cooling deteriorates, eventually necessitating oil restoration or replacement.

An increased acid number indicates the progression of chemical degradation processes in the oil, which can:

• Corrode metal components inside the transformer

• Reduce the dielectric strength of oil, compromising the insulation performance

• Accelerate the degradation of cellulose-based insulation

• Promote moisture absorption in the transformer, further intensifying aging and wear processes

Causes of increased acid number in transformer oil

The increased acid number of dielectric fluid is primarily due to oxidation, but several factors can exacerbate this process:

1. Oxidation reactions: when transformer oil is exposed to oxygen, it undergoes a chemical reaction that produces low-molecular-weight organic acids. Over time, these acids lead to the formation of heavier compounds that further degrade the oil.
2. Moisture contamination: water, whether from external leaks or condensation, accelerates oxidation and facilitates the breakdown of oil molecules.
3. Thermal stress: high operating temperatures, often exceeding 176°F, speed up the aging process for both the insulating oil and the cellulose insulation.
4. Contaminants: metal particles, sludge, and dissolved gases in the oil act as catalysts for oxidation, creating a medium that promotes the formation of acidic compounds.

These factors not only degrade the oil, but also compromise the overall efficiency and reliability of the transformer.

Addressing the acid number issues: transformer oil restoration

During transformer oil restoration, water, solids, and oxidation by-products are removed, which leads to restoring the properties of dielectric fluid to their initial state. Among the most effective techniques is the use of Fuller’s Earth, a natural clay with exceptional adsorptive properties.

Oil treatment with the use of Fuller’s Earth 

• Circulation: oxidized transformer oil is circulated through the layers of Fuller’s Earth, which adsorbs polar contaminants, including acids, sludge, and oxidation by-products.
• Neutralization: acidic substances in the oil are neutralized, reducing the acid number and restoring the dielectric strength of oil.

Positive aspects of transformer oil restoration by means of FLD 12R system

The FLD 12R system is specifically designed for transformer oil restoration. It employs advanced technology to maximize efficiency while minimizing waste, offering a range of key benefits:

• Reusable Fuller’s Earth layers: Unlike conventional systems, the FLD 12R allows Fuller’s Earth to be reused up to 500 cycles before replacement, significantly reducing material and labor costs.

• Environmental sustainability: By minimizing the disposal of spent Fuller’s Earth, the system addresses environmental concerns and supports compliance with waste management regulations.

• Cost savings: The system reduces oil losses by more than 90%, decreasing the need for new oil purchases and lowering the overall operating expenses.

• Improved oil quality: The FLD 12R restores the chemical and physical properties of transformer oil, ensuring stable performance and long-term transformer reliability.

As oil degradation progresses, the insulating and cooling properties of transformer oil deteriorate, increasing the risk of equipment failure. Restoration processes such as those provided by the FLD 12R system help extend transformer service life, reduce maintenance costs, and improve overall energy efficiency.

Moreover, oil restoration contributes to sustainability by reducing waste and promoting the reuse of valuable resources. Through technologies such as oil treatment with the use of Fuller’s Earth, industries can meet their energy demands while minimizing environmental impact.