This website uses 'cookies' to give you the best, most relevant experience. Using this website means this is Ok with you. To find out more click 'how we use cookies'.x

Select your language

Specialist Materials for Industry and Science



We refer to train mounted transformers as ‘traction transformers'. In contrast, the term ‘trackside' is used with reference to the transformers supplying overhead lines, ancillary equipment and third rail systems. 

Trackside transformers tend to be located close to the railway line and occasionally in densely populated or environmentally sensitive areas. In these situations it is sensible to choose a greater level of protection against environmental contamination and fire hazard than can be provided by using mineral oil.

Unlike mineral oil, MIDEL ester fluids have high fire points and have been approved for use in high risk areas such as tunnels and buildings. MIDEL esters also have 100% fire safety records, demonstrating a hig level of assurance.

MIDEL esters are also readily biodegradable which stands them apart from less environmentally friendly options such as mineral oil. If there was a spillage from a MIDEL-filled transformer the risk of contamination would be greatly reduced in comparison to the threat from other fluids.

Benefits of Midel Ester based fluids in Trackside 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 
  • 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.