How do you process and handle used transformer ester fluids?


Depending on their condition, Midel fluids can be reprocessed and reclaimed using similar equipment and methods to mineral oil.

  • High moisture content: vacuum filtration or treatment with absorbents such as zeolites

  • High acid value: treatment with Fuller’s Earth or similar absorbent material

In common with all natural ester liquids, if the viscosity of MIDEL eN 1204 has increased by more than 20% from the starting value then it cannot be reclaimed and should be sent for disposal – either through recycling or incineration for heat recovery.

Used MIDEL eN 1204 can be fed into recycling streams for other used vegetable oils, to produce products such as biodiesel, oils, lubricants and soaps.

Used MIDEL 7131 which cannot be reclaimed for transformer use can be utilised as a lubricant additive to mineral oil base stocks.




Read more on the benefits of alternative fluids such as ester for fire safety, the environment and moisture tolerance.


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Retrofilling transformers with ester fluids