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Specialist Materials for Industry and Science

Products & Properties

Products & Properties

How Midel Esters Benefit Oil-filled Transformers

At M&I Materials, we offer two types of esters. Our synthetic fluid MIDEL 7131 and natural transformer oil MIDEL eN both provide the crucial combination of fire safety and environmental protection. These properties are absent in mineral oil, and are important in securing the ongoing safety of an installation.

Synthetic and natural esters have been successfully used in new and retrofitted oil-filled transformers for many years. Comparing these fluids reveals the full extent to which Midel esters offer a much higher performance level than mineral oil.

MIDEL 7131

MIDEL 7131 is a fire safe, synthetic ester-based transformer fluid that has been successfully serving the global market since the 1970s. The flexibility, reliability and high performance of this product when used in oil-filled transformers has established it as a favourite with customers in a wide range of applications.

Our synthetic ester has been specifically developed to provide a safe alternative to traditional fluid and dry-type transformers. It is able to perform at high temperatures, offers increased fire safety, environmental protection and superior moisture tolerance.

MIDEL 7131 has an enviable track record encompassing thousands of highly successful projects, often located in demanding areas such as offshore or underground, where a high performance level is critical.


Another dielectric fluid providing high fire protection, MIDEL eN is a natural ester fluid that has been specifically developed to offer a cost effective, safe alternative to traditional fluid and dry type transformers.

In addition to its high fire point, MIDEL eN is also manufactured using renewable materials. This provides a lower carbon footprint solution when compared with mineral oil. It is also readily biodegradable, further minimising the impact on the environment should a leak or spillage occur in your oil-filled transformer.

MIDEL eN offers superior moisture tolerance, and laboratory testing has proved that it could potentially increase the lifetime of cellulose based solid insulation used in transformers.

This natural ester is suitable for use in sealed transformers only and is fully compatible with standard insulating materials and components.

If you would like more information on any of our Midel transformers oils, contact us today or browse our documents for the topic you're interested in.

  • Apiezon
  • Metrosil
  • Midel
  • Wolfmet

Products of M&I Materials Ltd.