David Wormleaton's right leg was amputated below the knee after the March 2009 incident, which occurred during work to dismantle a large sinter cooling system being trialled at the BlueScope Steel site.

Transfield Services Engineering Group (TSEG) was subcontracted to carry out the dismantling work.

Workers were removing pieces of the cooling system when a large fabricated steel frame weighing 1.7 tonnes and measuring 2.3 metres high and 8.1 metres long toppled onto Mr Wormleaton, causing serious crush injuries.

He was unaware that nuts securing the structure to concrete had been loosened and removed by other workers before it was to be secured by chains to a crane.

WorkCover launched an investigation into the incident, which led to proceedings in the NSW Industrial Relations Commission in April.

TSEG pleaded guilty to a breach of the Occupational Health and Safety Act and was fined $100,000.

The court found TSEG had failed to put in place adequate safety processes to prevent the frame from being unbolted before it had been attached by chains to the crane.

Last year, building firm Thomas and Coffey pleaded guilty to two charges and was fined $270,000 over the incident.

Thomas and Coffey was a subcontractor on the project which in turn contracted Allstate Cranes and Plant Hire, for whom Mr Wormleaton worked.

WorkCover NSW's General Manager of Work Health and Safety Division John Watson said safety for workers must be the highest priority for all employers, especially those working in manufacturing or with heavy machinery.

"Working with such heavy machinery or large products can be very dangerous, which is why every safety precaution must be taken," he said.

Mr Watson said WorkCover would work with TSEG to ensure no similar incidents occurred in the future.

During court proceedings, a company representative expressed remorse and regret over the incident and said arrangements had been made for a safety and fund-raising program to assist Mr Wormleaton.