What are the requirements when retrofilling transformers with Midel fluids?


There are four main steps to follow to retrofill transformers with ester fluids, as follows:

1. Set up retrofilling plant

  • Follow site procedures

  • Ensure transformer is fully de-energised and grounded

  • Perform site inspection and complete safety handover

2. Reduce mineral oil content as much as possible

  • Connect pumps and hoses

  • Ensure all pumps, lines and hoses are bonded and earthed

  • Pump the mineral oil from the transformer to the waste container

  • Rinse core and windings with heated ester fluid

  • Allow time for the tank to fully drain

3. Fill again using new ester fluid

  • User heated fluid

  • Use dedicated hoses and pumps to prevent contamination

4. Test and nameplate

  • Perform safety inspection and complete handover

  • Take fluid sample to carry out appropriate testing

  • Attached MIDEL nameplate as confirmation that the transformer has been retrofilled.


The video below goes through the process and benefits of retrofilling with Midel ester fluids.




For more detailed information on retrofilling with Midel ester fluids, visit our dedicated Retrofilling page, which has information on the reasons for retrofilling, case studies and supporting technical documents.


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Retrofilling transformers with ester fluids