Serious Incident/Close Call: Overhead Hoist Failure

Safety Alert Type: 
Heavy Equipment
Location: 
Ladysmith dry land sort (Vancouver Island)
Date of Incident / Close Call: 
2011-11-08
Company Name: 
ALJAQ Contracting
Details of Incident / Close Call: 

A logging truck driver was in the process of loading his trailer using a Mizia 7.5 ton overhead electric trailer reloader. The driver had raised his trailer to a height that would allow him to back his truck underneath, when the trailer came crashing back down. There was no injury to the driver but there was some damage to the truck and trailer.

An investigation was immediately conducted. The investigation revealed that the side of the sheave had broken and the weight of the trailer pulled the hoist line off the sheave causing it to land on the sheave axle pin. The sheave axle pin is held in place by two 3/16” metal ears which were easily spread apart by the weight of the trailer due to the fact that the axle pin does not extend past the metal ears and there is no retainer system to prevent the retainer ears form being spread past the end of the axle pin.

In summary the sheave failure caused the line to fall several inches landing on the sheave axle pin and the failure of the sheave axle pin assembly allowed hoist line, and trailer, to free fall until it hit the ground.

The hoist had passed an inspection on June, 07, 11 and daily inspections had been carried out and documented in accordance with the inspector’s recommendations.

Learnings and Suggestions: 

1. The manufacturer needs to reevaluate the material it constructs the sheave out of because it appears to be a very porous cast material that is not very resistant to wear.

 2. An appropriate method for retaining the sheave axle pin in place to prevent it from being pried apart if a sheave were to ever fail again.

3. ALWAYS ensure that you are not in the bight when using an overhead lifting device. You should always assume that it could fail at any time and position yourself accordingly.

*The manufacturer has already developed a retainer system for the sheave axle pin and is in the process of manufacturing and distributing the new modification to their similar hoists.

For more information on this submitted alert: 

Alben Stromquist, ALJAQ Contracting 250-714-3670

File attachments
Serious Incident/Close Call: Overhead Hoist Failure.pdf
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