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Specialist Materials for Industry and Science



Distribution of power to underground applicators can pose a wide variety of problems not least fire safety, maintenance cycles and environmental considerations. These challenges are particularly pertinent when supplying to underground transport networks.

The transformers supplying the trains and ancillary equipment are predominantly in enclosed underground locations within close proximity to railway staff and passengers. As such fire safety is a key concern and undoubtedly a major reason why our customers choose a high fire point fluids such as MIDEL 7131 and MIDEL eN.

MIDEL 7131 has been used in underground applications for many years providing a fire safe solution for respected customers such as London Underground and Hong Kong MTR.

Besides the obvious fire safety, MIDEL 7131 is robust and delivers long term stability even when experiencing extreme temperatures and high overloads.

Benefits of Midel Ester based fluids in Underground Transformers

Increased Fire Safety

High Performance

  • Greater moisture tolerance than mineral oil
  • Robust and stable, conducive to lower levels of maintenance

Greater Environmental Protection

  • Readily biodegradable according to OECD 301 and fully biodegradable according to IEC 61039
  • Non-toxic and non-water hazardous
  • MIDEL eN is a natural ester from a renewable vegetable oil

Excellent Customer Service

  • Multilingual commercial team
  • First-rate customer care
  • Continued technical support from the transformer fluid experts

Additional Benefits of MIDEL 7131

  • High temperature performance allowing for compact transformer designs
  • Proven in demanding conditions throughout the world
  • Greater moisture tolerance than MIDEL eN
  • Reputation as the ‘fill and forget fluid'
  • Flexible, suitable for breathing and sealed transformers
  • Popular choice for retrofilling breathing transformers

For further information please visit our Documents or Contact Us.

  • Apiezon
  • Metrosil
  • Midel
  • Wolfmet

Products of M&I Materials Ltd.