Date of incident: January 2020
Notice of incident number: 2020188280001
Employer: Structural concrete forming company

Incident summary
At a highrise apartment building construction site, a crane operator accessed an electrical crane control cabinet located in the operator’s cab of the crane. He touched and wiggled a wire that looked out of place. An arc flash occurred, causing several electrical components within the control cabinet and the worker’s jacket and pants to catch fire. The worker removed himself from the cab, took off his jacket, and used his hands to extinguish flames on his pant leg. He then climbed down the crane mast ladder to the ground below. The worker sustained serious injuries.

Investigation conclusions

Cause

• Not locking out 480 V power supply. The worker did not lock out the 480 V electrical power supply coming into the crane cab from the International Electrotechnical Commission (IEC) rotary switch, located in the slewing ring underneath the crane’s cab, before accessing the crane control cabinet. As a result, although the worker had switched the control cabinet’s electrical power rotary switch to the OFF position, the control cabinet still had 480 V power within it.

Contributing factors

• Worker not qualified to work on energized electrical equipment. The operator was trained and qualified to work on de-energized electrical components. The control cabinet was still energized with 480 V power, as the IEC rotary switch in the slewing ring was in the ON position.
• No weekly inspections. Neither the manufacturer's instructions nor the employer’s weekly inspection checklist were followed to ensure that electrical connections in the crane control cabinet were secured. The employer failed to ensure that the crane's weekly inspection checklist was being completed.

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