Oil Treatments

Oil drums

"In situ" treatment of transformers oils

Our 30 years experience in the treatment of dielectric oils, has allowed us to develop equipment and procedures that allow us to make the process "in situ" WITH THE TRANSFORMER IN SERVICE widely outperforming European standard IEC 60422:2013 and its equivalent Spanish EN-60422.

Before any treatment to the transformer oil, it is necessary to know its history and recent analytical.

Treatments Equipment

Our equipments are developed by RYMOIL S.A. according to the type of transformer to be treated, our experience, our R+D+i department and collaboration of leading universities and manufacturers in the industry.

There is the wrong idea that an equipment is more powerful if it has much more flow, nothing is further from reality. Equipment will be more powerful as more water, particles and gases is capable of eliminating in the unit of time, maintaining the quality of the oil in optimal state.

Our equipments have special filters, optimized degasser, automatic heaters, particulate filters, steam and condensation trap and double vane pumps and roots for maximum results of quality oil in the minimal time invested.

Our power equipment, developed by RYMOIL are mobile, mounted on truck and laboratory.

Our distribution equipment, mounted on a chassis with wheels allow us to reach the more inaccessible places, such as the electrostatic precipitators in thermal power stations and Underground Transformer Stations.

Processes whith the transformer in service

RYMOIL S.A., has own procedures which allow, with total safety, perform these processes with the transformer in service.

Under vacuum reconditioning

Including dehydration, degassing and removal of particles, in order to ensure that the properties of the oil are kept in a range of appropriate values to avoid electric arcing against intense electric fields.

Oil reclaiming and additivation

RYMOIL S.A Before make this process requests a sample analysis for free of:

  • Reclaiming viability.
  • Determination of absorbent, sepiolites, bentonites, fouler, activated or burned soils, etc.
  • Type of inhibitor, compatibility and percentage to add.

With the reclaiming a new oil typical properties are retrieved, the transformer insulation ensuring the reliability of the same and avoiding costs of replacement of oil with a new one. If it is appropriate to replace the used oil and the filling of the transformer with new oil, without previously making an internal cleaning to remove the old oil sludge, these would act like catalyst, rapidly aging the new oil.

The process has a 5-year guarantee.

Another process

  • Oil degassing.
  • Antigazing additivation.
  • Special additivations.
  • Isolation recovery.

In our database we have the analytical results of transformers regenerated in 1984 that a maximum of two or three reclaiming during this time, the oil is kept in perfect condition until today.

Processes with the transformer out of service

Filling and commisioning of new transformers

Transport of transformer with dry air, carbon dioxide or nitrogen

Drying of windings "in situ"

Using a mobile oil treatment unit. Should be done, both, at the time of commissioning, after a period of exposure to the ambient humidity (case of repairs), as well as when cellulosic insulation reach a significant moisture content, as a result of the absorption of part of the water content of the insulating oil.

The moisture in the winding produces:

  • A low insulation among phases.
  • A high content of water in oil.
  • Low dielectric strength.
  • A major risk of short circuit.

RYMOIL S.A., depending on the transformer tank support or not vacuum, use the following procedures:

  • OIL SPRAY drying.
  • Drying by rising.
  • Drying by recycling.
  • RYMOIL’s drying.

RYMOIL fter windings drying which occurs in the extraction of water and other products of oxidation, recommend a reclaiming process.


During the RYMOIL process will do periodic analysis to monitor and control the process in his mobile laboratory.

  • RYMOIL S.A. guarantees all the processes carried out. In the case of reclaiming, this guarantee will for 5 years.
  • At the end of the process is prepared a report in which it is noted the analysis carried out initially, during and at the end of the process, in our Head Laboratory, as well as the procedure performed.

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

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

Duración del proceso

  • 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.

Número de intervenciones

  • 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.

PCB Management

RYMOIL is Manager of hazardous PCB waste since 1991, allowing it to handling, loading, transport, management and destruction in the facility of its Company AGR in Asturias - Spain.

The authorization also allows processes of decontamination “in situ”, collection, transport, administrative management and decontamination of PCB contaminated oil by means of metallic sodium in AGR, for reuse as dielectric oil once reclaimed and additivated by RYMOIL.