This news article featured in issue no. 8 in CHSP’s November 2021 newsletter.
A 56 year old high voltage Electrical Engineer died due to carbon monoxide asphyxiation whilst working for a plant hire company on a faulty industrial transformer on the 19th June 2021.
The experienced Engineer, Mr Audsley, had been working on the transformer after it was sent back from the customer as faulty, later it was found there was not enough oil to allow the transformer to work sufficiently. The transformer of its type was capable of operating at 11,450 volts (similar size as the one pictured) and was supposed to run on 2,500 litres of mineral oil.
Cause
The transformer was on hire to a customer of the Engineers Employer Hirst Electrical Plant Hire Services UK based in Wakefield. The customer had had the transformer on hire for approximately 3 years and had been sub hiring it to a number of customers within that time. When the customer reported a defect the transformer had been returned and was being worked on at the Wakefield site to identify the fault for re-pair.
On inspection the following observations were made:
- There was a burning smell considered to be an indication the transformer had been operated without sufficient oil.
- a drain valve looked as if it had been removed and replaced using fresh Polytetrafluoroethylene (PTFE) sealing tape.
- The HSE discovered there was only 170 litres of oil in the transformer, the rest of the space had been filled with carbon monoxide where the rest of the oil should have been.
The oils function is to cool and insulate the outer casing. When the copper wires are energised. The copper windings were covered in cellulose paper. The IEC 60599 notes that “cellulose paper decomposes at higher temperatures forming carbon monoxide, carbon dioxide and other gases.”
Outcome
Mr Audsley used an overhead crane to lift the lid off the transformer and a step ladder to get up and un-screw the bolts. He was found slumped over the transformer unresponsive and could not be revived after CPR was given. He was pronounced dead by paramedics at 3.04pm.
The Coroner issued a Future Deaths report to the hire company to prevent further occurrences with this type of transformer that may be in use across the UK.