Decontamination of oil-filled transformers contaminated with PCB "in situ" for reuse


In the business there are several processes for decontamination of oil-filled transformers with PCB by means of continuous circulation in transformer using different products as:

  • • Metallic Sodium.
  • • Sodium methylate
  • • Metallic Litium
  • • Polyethyleneglycol
  • • Potassium hydroxide
  • • Polyethylenes mixures.
  • • Decontamination of PCB oil transformer.
• Polypropyleneglycoles.
  • • Catalysts, etc...

To decontaminate the oil with temperature and vacuum, will destroy the dielectric properties of the same and the recirculation through the inside of the transformer, part of reagents attack the varnish of windings and the insulation paper.

On the other hand, the oil of the tank can be decontaminated but not the oil that is on the inside of the transformer winding.

With the transformer on service, the balance by capillarity between the contaminated oil inside of the coil and the decontaminated oil of the tank is reached in a period of six months. This can mean an increase of the PCB content in the decontaminated oil.

Depending on the Company, the guarantee of those processes could vary between three to five months.

Rymoil process

  • It keeps the dielectric properties of the oil in their maximum values.
  • It does not degrade the insulation properties and even improved it.
  • We guarantee the transformer decontamination with the oil during its lifetime.

Rymoil process technique

This technique should be held with the transformer out of service by and PCB authorized manager, RYMOIL is PCB AUTHORIZED MANAGER from 1991.

Process steps

  • Emptying of the contaminated oil to a cistern for its decontamination in AGR by metallic sodium and regenerated oil
  • RYMOIL process of cleaning, winding removal by vacuum and internal decontamination.
  • Cleaning with an oil just used for treatment.
  • Filling of the transformer either with new oil treated or with decontaminated and regenerated oil.

Duration of the process

  • 8 hrs for transformers up to 5.000 kg.
  • 2 days for transformers up to 25.000 kg.
  • 3 or 4 days for transformers > 25.000 kg.

Number of intervetions

  • 1 intervention for transformers < 500 ppm PCB.
  • A 2nd intervention after one year for transformers with 500 ÷ 2500 ppm PCB.


  • Permanent decontamination of the transformer and its reclassification as transformer oil with < 50 ppm. (Decontamination for lifetime).
  • 5 years for oil in the case of using decontaminated and regenerated oil. In the case of new oil, the manufacturer guarantees.
  • Improvement of isolation and cleaning of the insulating material.