SAFETY managers at a Teesside power plant have changed their procedures after an explosion killed three workers and maimed one other.

An inquest in Teesside heard that the men had been carrying out maintenance work on a transformer at the site in Wilton, near Redcar, east Cleveland, on August 8, 2001, when it exploded.

The inquest jury heard the transformer was momentarily charged with enough energy to power five million electric fires when the men inadvertently short-circuited a device to alter the voltage.

Although the transformer automatically cut out in milliseconds, Andy Sherwood, 36, of Hartlepool and Darren Higgins, 28, of Normanby, caught the full blast of an explosion. They could only be identified by their dental records.

Another man, Paul Surtees, 40, of Hawthorne, east Durham, died in hospital the following morning after sustaining more than 90 per cent burns. A fourth man, Graeme White, of Billingham, who was at the plant to observe procedure, received ten per cent burns but survived.

The men worked for US company Enron which was then running the plant. They had been trying to manually "tap" the electrical transformer to adjust the voltages in order to close a circuit breaker for maintenance.

Speaking at the inquest yesterday, health, safety and environmental engineer Louise Russell told coroner Michael Sheffield that procedural rules had been changed since the accident. In future further checks will be carried out before keys to allow access to transformers are passed on. A review into the whole process of manual "tapping" has also been completed.

All the evidence was heard by the close of the inquest yesterday. The coroner will address the jury today.