A former apprentice has been convicted and fined over a fiery workplace prank at a Hallam factory, in eastern Melbourne, in 2008.

Daniel Bridgborn was badly burnt when he was drenched in flammable brake cleaner and set a light while working under a truck at MTU Detriot Diesel in Hallam.

The Ringwood Magistrates' Court heard Gladysdale man Matthew Lever, 23, and his two workmates, Dylan Poulton and Robin Marshall, had been fooling around by setting themselves alight as well as work benches in the days leading up to the attack.

One had set "fire to his bum" the day before.

Prosecutor Susan McCarthy said it was Lever who poured the highly explosive chemical on Mr Bridgborn. His workmate then set him alight.

Lever's lawyer Tim Marsh told the court the burning of the worker was not a case of workplace bullying, but the result of a four-day carry on.

"There was a degree of amusement or entertainment value on the day. It was all done for a laugh," he said.

Mr Marsh said there was a misunderstanding between all three men about what was about to happen but agreed it was risky and dangerous behaviour.

Lever quit his job the same day and his two accomplices were fired.

Magistrate Kate Hawkins convicted and fined him $5,000 plus court costs.

His two co-accused were dealt the same punishment in 2008.

The court heard the diesel company had carried out its obligations under the health and safety act in educating the workers.