Date of incident: August 2019
Notice of incident number 2019157620008
Employer: Building construction company

Incident summary
A worker was operating a mobile crane to deliver roofing supplies to a two‑storey building. The worker and his supervisor set up the crane. To deliver a pallet of shingles to the roof of the building, the worker telescoped the boom of the crane all the way out to its maximum extension length, orienting the boom toward the intended landing spot on the roof. The worker began lowering the boom, and the supervisor advised him to use a boom angle of 71°. As the boom descended, the crane tipped over onto its side. The worker and the supervisor jumped off the opposite side of the crane as the crane tipped over. Two buildings were damaged. No workers or other people were injured.

Investigation conclusions

Cause

• Crane’s rated load capacity was exceeded while making lift. To lift a load the required distance and height, given where the mobile crane was set up, the maximum load capacity of the crane was 1065.9 kg (2350 lb.). The load weighed approximately 2292.9 kg (5055 lb.), well over the rated load capacity. Thus, the crane tipped over during the lift. The load capacity and boom angle had been determined using a load chart located on the frame of the crane, which was not applicable to the crane as mounted on the truck. A custom load chart in the cab of the truck, which was outdated but applicable, was not used.

Contributing factors

• Lack of information, instruction, and training. In order to operate a crane, a worker needs to have completed practical training in addition to theoretical training. Training should include information on the use of the load chart for the crane as well as the manufacturer’s operating manual — specifically operator qualifications, operational aids, planning the job safely, and safe operation of the crane. Adequate information and instruction, including a custom load chart and a manufacturer’s operating manual, was not provided.
• Inadequate supervision. The employer failed to ensure that effective supervision was provided by creating a plan for supervision of workers and devising practical exercises for them such as placing loads onto elevated locations.
• Failure to use safe work practices. Appropriate safe work practices for working within the rated load capacity, including measuring the load radius, determining the load weight, and using the correct load chart, were not used.

Other safety issues

• Missing operational aid. The mobile crane was not fitted with an operational aid as required by the Occupational Health and Safety Regulation. Such an aid could have affected the incident outcome, depending on which device was present. A load weight indicator would have provided an accurate load weight. A load moment indicator (LMI) might have alerted the worker when the crane exceeded the rated capacity, allowing him to stop the lift. Or if the crane had had an LMI with the capability to disengage the crane’s functions, the incident might have been prevented.

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