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Worker jumps off truck deck as crane's boom fell backwards

Date of incident: April 2013
Notice of incident number: 2013117080107
Employer: General trucking company

Incident summary

Several days before the incident, a hydraulic lift cylinder on a truck-mounted crane started to leak oil. The cylinder was removed and taken to another company for repairs. After the crane had been returned to service, the operator was at the controls and was lifting the boom up from the stowed position. He was not looking at the boom angle. The operator heard a bang and looked up to see that the main hydraulic lift cylinder had released from the cylinder barrel, and then the boom fell over backwards towards the truck deck.

As the crane's boom fell, it narrowly missed hitting a worker who was standing on the right side of the trailer deck. The worker jumped from the deck to prevent being struck as the boom fell over. He did not sustain any injuries.

Investigation conclusions


  • Failure of the hydraulic cylinder on the truck-mounted crane: The boom of the truck-mounted crane fell over backwards when the hydraulic lift cylinder failed after the operator raised the boom to a vertical position at the maximum stroke of the cylinder. The repair company had made a machining modification that reduced the amount of cylinder barrel wall material below the snap ring groove. As a result, the cylinder could not withstand the hydraulic pressure at full extension. The failure of the hydraulic lift cylinder caused considerable damage to the crane as well as the potential for serious injury or death.

Underlying factors

  • Repairs not completed as specified by the manufacturer: The employer did not ensure that repairs to the hydraulic lift cylinder were performed in accordance with the manufacturer's instructions or in compliance with the Occupational Health and Safety Regulation.
  • Failure to ensure engineering oversight: The employer failed to ensure that a professional engineer was consulted to certify the repair work completed on a load-bearing component of the crane.

Request the full report

Publication Date: Apr 2013 Asset type: Incident Investigation Report Summary NI number: 2013117080107