Oil Filtration Services

Oil Filtration

Recommended to perform routine tests at least once a year in order to monitor the healthiness of your transformers. Faults can occur at any stage of transformer’s life and evolve rapidly. Testing your transformers on a regular basis will allow you to detect any unforeseen change in the condition of your transformers. Transformer oil purification is a process to remove sludge, dissolved moisture and dissolved gases from the oil. Transformer oil conditioning may also include to some extent improving the acidity of the oil.

A good oil purification system is able to deliver filtered oil with parameters as per the standard specification.

However, this revival of the oil by oil filtration plant to standard oil parameters is based on the quality of unprocessed oil and its initial process. In case the unprocessed oil does not match the standard oil parameters, then the effort of transformer oil filtration is all in vain. Alternate method of regeneration of transformer oil should be adopted in this case.

Transformer oil filtration by vacuum type dehydration and centrifuge type removal of solids and water separation.

Transformer oil conditioning is a stream line oil filtration process of sludge purification, moisture removal and gas removal.

First step in the transformer oil purification

The first step in this serial process is to raise the oil temperature to a desired level, generally upto 65 Deg C. This aids to give the oil latent heat which later aids to dissociate the moisture and gases from oil in the degassing chamber. Additionally the viscosity of the oil drops which aids in better filtration to some extent. Recommended heater design should consider an area of heating of about 1 to 2 W/sq.cm. In the transformer oil purification plant, the heating system is protected against over pressure built up and excess temperature rise.

Second step of transformer oil purification

The second step of transformer oil purification plant is removal of sludge and dirt from the transformer oil.

Two methods have been used for removal of the sludge:

Removal of sludge by filter candles. and/or Removal of sludge by centrifuging action.
Oil Filtration And Circulation (Min 3 Cycle) Cycle As Per IS:1866:2000.
Field testing of Dielectric strength (BDV) of the Transformer Oil should be carried out in accordance with the provisions of IS 6792 & IS 1866 at regular interval during filtration job. The readings must be submitted to EIC for acceptance before stopping the filtration job.

The BDV test shall only be conducted after giving sufficient time for the oil to settle down after stoppage of the filtration process. Min BDV Value after completion of filtration and cooling down of oil should be min 60KV using 2.5mm gap electrode as per IS 6792 & PPM should be less than 20.

Removal of all suspended particles such as dust, rust, scales, colloidal carbon oxidation sludge etc. up to < 1 micron. Degassing and Dehumidification of Transformer Oil under vacuum. Circulation of heated Oil and Filling of treated oil in Transformer tank. De-acidification by evaporation and adsorption method.

Our single stage plants are capable of attaining following oil parameters in 3-4 passes and Two Stage Plants in 1-2 passes.


Mainly consists of inlet pump (Gear type positive displacement), Outlet pump (positive displacement Gear type or Multistage Centrifugal) and necessary valves & piping to ensure easy operation and maintenance. Complete system is vacuum tight to have a leak -proof operation.


It is suitable for removing suspended particles such as colloidal carbon, oxidation sludge, dirt, rust, scales up to < 1 micron. It consists of PRE FILTER and FINE FILTER.


It is a metallic strainer with magnet. It removes magnetic and coarse suspended particles and to protect inlet pump from damage due to abrasion.


Removes all suspended particles up to < 1 micron. Filter Elements are either non-hygroscopic molded cellulose cartridges or cleanable (with reverse airflow) edge type filter candles. Filter cartridges are easily replaceable. Additional Intermediate filter can be provided to increase life of fine filter.


It is designed to remove large portion of dissolved impurities (Including Moisture) from oil. Rasching ring trays and oil dispersing system are provided to have sufficient exposure of oil to vacuum during filtration. Oil level is controlled with float switch.


Rotary oil-sealed vacuum pump or combination of Mechanical Booster Pump and Rotary oil-sealed pump is provided to get proper working vacuum during filtration. Necessary valves for easy operation and maintenance of the plant.


Ionic Reaction Column for acidity removal.
Transformer Evacuation System.
Filter Press as an intermediate filter to increase the cartridge life.
Additional Instrumentation such as Temperature Indicating Controller, Flow Meter, On-line Oil Testing Equipment.


These plants are designed for filtration and dehydration of Power and Distribution Transformers and oil in tank. These plants can also be used for hot oil circulation in transformers and transformer drying.