‘Faulty switch led to fatal explosion'

Electrical supervisor Graham Hiles suffered first degree burns and died three weeks after the “arc flash” incident at the ConocoPhillips terminal at Seal Sands, Teesside.

The tragedy at the oil refinery happened on July 19, 2006, after the 52- year-old father-of-two had approved the wiring work of senior electrical technician Chris Emery.

It was the first time Mr Emery, from Billingham, near Stockton, had installed a test switch on a substation and it was a different model from the one he removed.

Yesterday, at an inquest in Newcastle, Mr Emery relived the moment he and Mr Hiles, from Yarm, near Stockton, suffered the full force of the electrical explosion that left him unable to work for eight months and killed his colleague.

He said: “Graham energised the unit and when he turned the handle there was a big bang.

“I was directly behind him and we were both facing it. I could vaguely picture Graham. He looked a bit black. I recall him saying he had lost his hair.”

The inquest heard how two connections in the test switch were cross-wired, which, on its own, would not be enough to cause the explosion.

But an investigation revealed there was damage to a control cable laid underground 30 years ago, which led to an earth fault. This, coupled with inaccurate wiring, created an “energised” electrical system, ionising the air and building up energy in a compressed space.

All of this happened in a split second and led to the explosion.

Stephen Jackson, from Blackhall, County Durham, was an electrical supervisor who worked on the substation the previous week while Mr Hiles was on holiday and rushed to the plant medical centre after hearing about the blast.

He said: “Graham was walking by himself, but he was full of adrenaline and pumped up. He had burns on his face and head.”

Mr Hiles died after treatment at the Royal Victoria Infirmary in Newcastle.

The inquest continues.