Are Midel fluids compatible with all transformer materials?


As a rule, components and materials used in mineral oil transformers are also compatible with MIDEL fluids.

Midel Compatible Materials

The M&I Materials technical department has compiled a study based on thorough testing and research, which they continuously conduct. The compatible and incompatible materials lists produced incorporates a wide range of materials and components commonly used in transformers.

In all cases the user should confirm the suitability of any material to be used in equipment with MIDEL ester-based fluids. When investigating the compatibility of a material or product, ask the vendor or transformer manufacturer if they have run compatibility tests.

For gaskets, Midel recommend good maintenance practices

By the time a transformer is identified as a retrofill candidate, it has most likely been in operation for several years. The condition of the gaskets likely includes wear and tear (swelling from contact with oil) and mechanically set (it has taken a ‘set shape’, dried out, cracked). If untouched, gaskets may survive without incident. However, during retrofill it is likely gaskets will be touched, either physically or indirectly.

If the tank and/or the gasket itself (in an aged, set, potentially cracked condition) is moved, the outcome is likely to be less than desirable. This has nothing to do with any interaction with the fluid, but rather the mechanical integrity of the gasket. The same recommendations would apply to a service company flushing, reprocessing or refilling with mineral oil.The outcome is not provoked by the new mineral oil; rather, it is because the aged gasket was directly or indirectly moved.

Tap Changers and Midel fluids

MIDEL fluids are approved for use with a range of tap changers from industry leaders such as MR and ABB. For more information on tap changer compatibility, including other brands of tap changer, get in touch with Insulect’s technical team.

Transformer Components and Midel fluids

Our technical team can answer any questions you have regarding compatibility of ester fluids with all transformer components – we’ve been a trusted component supplier to OEMs, end users and service businesses for over 25 years.

Watch our Transformer Care video for more info.





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Retrofilling transformers with ester fluids