Oil Testing / Replacement 


Testing of electrical insulating oil is an essential part of maintaining transformers and high voltage equipment in first class condition.

Rosh Engineering’s trained staff can take oil samples in the approved manner for submission to the laboratory that is UKAS accredited to ISO17025 for analysis.

Tests carried out include:


Physical Testing


General Condition   appearance, contamination, colour, odour
Acidity   total acid number (mgKOH/g)
Moisture Content   Karl Fisher titration (ppm)  
Electric Strength  average of six breakdowns (kV)



Dissolved Gas Analysis (DGA) can also be carried out for the identification of hot spots and potential fault conditions. This includes the identification of:

Oxygen, Nitrogen, Carbon Dioxide & Monoxide, Hydrogen, Methane, Ethylene, Ethane, and Acetylene.


Furfuraldehyde (FFA) test can also be carried out to estimate degradation of insulating papers in power transformers. With sufficient history and operating experience the life of a transformer can be managed.

A problem solving capability is provided to achieve the most efficient solution.

Oil replacement or filtration can be carried out on site.  When applicable on line processing devices can be fitted to return the transformer’s insulating liquid to the best operating standards.

Silicon fluids and synthetic esters such as Midel insulating liquid can also be tested and replaced as necessary. Retrofilling mineral oil for Midel in fire hazard areas can be carried out on site with full management and handling of all materials following appropriate recycling and disposal routes under UK Environment Agency rules.

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