Dry Core transformer oil reclamation plant

The Dry Core transformer oil reclamation plant is responsible for one of the most important processes in power transformer maintenance: the deep restoration of the oil’s operational properties after aging. During transformer operation, chemical reactions, high temperatures, moisture exposure, and cellulose decomposition products gradually destroy the oil’s structure. If regular reclamation is not performed, sludge, resins, asphaltenes, and deposits form in the tank, settling on the windings and tank walls. As a result, this increases the risk of local overheating, worsens heat dissipation, and may cause insulation failure.

Fresh transformer oil has a light-yellow tint, but after several months of operation it darkens due to contamination, overheating, and oxidation processes. During accelerated aging or the presence of foreign contaminants, the color changes much faster. Darkening itself is not a defect, but it indicates the degree of degradation. Particularly dangerous are the decomposition products of varnish coatings, insulation, and sludge from degraded oil. They are hygroscopic and create conditions for reduced dielectric strength and partial discharge formation.

Causes of changes in transformer oil properties

Transformer oil in a healthy transformer has a light-yellow color and high transparency. However, its darkening is a natural consequence of:

This approach uses reagents that interact with contaminants and convert them into forms suitable for removal. Common processes include:

• hydrogenation;
• alkaline–acid purification;
• oxidation;
• neutralization of acids;
• purification using metal hydrides, carbides, and oxides.

Chemical methods can break molecular bonds of resinous and asphaltene compounds but often require additional fine processing.

Physical method

Physical methods target the removal of moisture, mechanical impurities, and light fractions. These processes include:

• centrifugation;
• gravitational sedimentation of particles;
• magnetic and electrostatic fields;
• vacuum distillation;
• washing and evaporation.

Vacuum is especially important: at pressures down to 0.04 inHg, water and gases evaporate at much lower temperatures, stabilizing dielectric strength and eliminating bubble formation risks.

Physico-chemical method

Combining both approaches yields the best results. Key processes include:

• selective absorption of acids, sulfonates, resins, and asphaltenes;
• coagulation of colloidal contaminants;
• ion-exchange reactions.

Physico-chemical methods are most effective for restoring heavily degraded oil. They combine adsorption and coagulation processes, where special sorbents selectively absorb polar compounds, acids, and resinous aging products. This group of methods forms the basis of the DC-R Dry Core transformer oil reclamation plants.

Dry Core transformer oil reclamation plant

The Dry Core equipment line (DC-R series) consists of modern deep-sorption reclamation systems designed for effective purification of transformer and other insulating oils without using acids, alkalis, or hazardous reagents. All DC-R systems operate on the same principle: passing the oil through a multicolumn sorption block where a special adsorbent captures oxidation products, sludge, resins, acids, and other polar contaminants. Thanks to their design, DC-R units ensure high reclamation speed, stable purification quality, and long adsorbent life, which can be regenerated up to 500 cycles. The assortment includes models with different capacities—from compact solutions for small substations to high-performance systems for large power facilities, with optional degassing and thermal-vacuum drying modules.

Efficiency depends on the condition and type of processed oil:
DC-12R — 4.4 to 8.8 gpm (1000–2000 l/h)
DC-6R — 1.98 gpm (450 l/h)
DC-10R — 3.3 gpm (750 l/h)

Physico-chemical processes of Dry Core
The Dry Core transformer oil reclamation plant uses adsorption processes based on Fuller’s Earth. This adsorbent has porosity up to 250 square feet per gram and selectively absorbs:

• acids;
• resins;
• sulfonates;
• asphaltenes;
• oxidation and aging products.

It is adsorption-based reclamation that ensures complete restoration of thermo-oxidative stability, color, transparency, and dielectric strength of transformer oil.

Advantages provided by the Dry Core transformer oil reclamation plant

Using Dry Core not only fully restores oil properties but also stops the degradation of solid insulation in the transformer. Removing polar aging products prevents sludge formation, which can block cooling channels and reduce thermal efficiency. After reclamation, breakdown voltage increases, transparency and stability are restored, and the transformer oil reclamation plant can operate together with Dry Core DC-D degassing modules, providing a complete purification cycle—from drying to deep sorption reclamation.
Key DC-R technical solutions:

• continuous circulation through sorbent columns;
• ability to regenerate the adsorbent without replacement;
• temperature control within 158–194°F (70–90°C);
• 20–40% increase in breakdown voltage;
• several-fold reduction of dielectric loss tangent.

The result is restoration of up to 80% of aged oil, which after treatment meets the parameters of fresh oil. This extends transformer service life by decades, especially when reclamation is combined with degassing and filtration.
Thanks to the combination of multistage sorption, adsorbent reactivation capability, and adaptive modularity, Dry Core is one of the most reliable and cost-effective technologies on the market. Each Dry Core transformer oil reclamation plant not only returns oil to a like-new state but also allows the reclamation cycle to be repeated many times.