• WorkSafe BC Bulletin: Tower Crane Freefall Incident

    The importance of inspection and preventative maintenance on gear boxes

    A tower crane operator had just finished hoisting formwork form the upper level of a concrete residential high-rise to its first level, and was hoisting the load block while advancing the trolley toward the mast. Without warning, the empty hook, load block, and rigging chains (about 454 kg/1000 lbs altogether) plummeted to the ground, the load line spooling around them. No workers were injured, but several were working in close proximity to the falling equipment.

    Gearbox_Macropitting_GearsInspection of the hoisting gear box revealed that a gear had broken in half during operation. Lab tests showed that the gear was made of defective metal and prone to cracking, breaking down, and failing during operation.

    Other tower crane gear boxes have failed, most recently during a lift in Alberta in fall 2015. In this case, as above, regular and thorough gear box inspections could have identified gears needing repair or replacement. Such inspections are key to preventing crane equipment collapses and serious or fatal injuries.

    Safe work practices:

    • Regularly inspect and maintain all tower crane gear boxes according to the manufacturer’s instructions; seek written confirmation of their fitness for service from an engineer or person designated as qualified by the manufacturer
    • In the absence of the manufacturer’s inspection criteria, develop and implement an appropriate inspection and preventative maintenance program for all gear boxes
    • Pay particular attention to signs of fear fatigue or cracking; consider using X-rays or magnetic particle testing to detect hidden flaws
    • Repair or replace damaged or defective parts immediately. Have repairs certified by a professional engineer, or, if available, by the original equipment manufacturer
    • Keep detailed reports of gear box tests, inspections, maintenance, repairs, modifications, and pre-start inspection for the service life of the equipment
    • Keep the equipment logbook available on request to workers, supervisors, the operator, and/or the person responsible for inspecting, testing, or maintaining it, as well as anyone else on site.

     

     

     


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