Transformer mineral oil replacement with MIDEL 7131 helps a UK manufacturer reduce transformer fire risk 

The Customer

A high-value manufacturing facility in the UK.

The Problem

A potential fire risk was identified within its building – a 1500 kVa mineral oil-filled transformer located in proximity to large gas cylinders. Given the potential flammability of mineral oil, the customer reviewed options to mitigate this risk.

The MIDEL Solution

The decision was taken to replace (or “retrofill”) the mineral oil in the unit with MIDEL 7131 – a K Class, synthetic ester fluid with a very high fire point (>300°C).  MIDEL 7131 is also biodegradable and non-toxic, so delivering additional environmental benefits for the customer. As a result of retrofilling the transformer with MIDEL 7131, the asset will be able to run at higher operating temperatures, delivering more reliability for the end user.

Grosvenor Oil Services, a MIDEL Service Partner (MSP) was contracted to carry out the retrofilling work. To reduce disruption the work was completed on a one-day outage on site during the Christmas shutdown period.

The old mineral oil was drained into suitable containers and removed from site for disposal in accordance with Environment Agency legislation. The new MIDEL 7131 ester fluid was processed into the transformer in accordance with manufacturer M&I Materials guidelines for retrofilling. The transformer was returned to service shortly after the work was completed.


“Risk mitigation was central to the customer’s
concerns on this project. A transformer fire in
this high-tech, high-value facility would mean
huge disruption to productivity, not to mention
revenue loss and reputation damage.
A mineral oil replacement, or retrofill with MIDEL
ester fluids eliminates the transformer fire risk
because of the fluids’ high fire point. MIDEL fluids
are also biodegradable, unlike mineral oil which
is both toxic and non-biodegradable, so using
MIDEL also delivers environmental benefits.”



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