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Stud Failure leads to “Wheels Off” Incident

Safety Alert Type: 
Vehicles
Location: 
Hudson Bay, SK
Date of Incident / Close Call: 
2018-12-10
Company Name: 
Weyerhaeuser
Details of Incident / Close Call: 

Small cracks were visible on the back face of the outer rim (aluminium) of a heavy commercial vehicle's wheel. Experts indicate that these cracks form between stud holes as a result of wheels being “run loose” at some point. When cracks form from stud hole to outer rim edge, it is the result of contact stress (weights too heavy, hit bad bump etc).

In this incident a single stud had broken approximately 2 months prior to the wheels off incident (due to the cracked rim). Only the damaged stud was replaced and the cracked rims went unnoticed and uncorrected. When the single stud broke, it compromised the remaining studs, that were not replaced. At this point it was only a matter of time before another failure occurred.

Two months later, a catastrophic failure of all 10 studs occurred within 50-100km resulting in a wheels off on a public highway.

 

Learnings and Suggestions: 
  • When you have problems with wheel end components: a broken stud, a loose nut etc, you must investigate and correct the cause, not just the part that is broken. In this case the cause of the stud failure was the cracked rim. Fixing the broken stud did not - and would not - have prevented this occurrence without also replacing the rim.
  • Manufacturer’s recommendations must always be followed when completing a repair.  Common manufacturers such as Accuride Wheel End Solutions recommend replacing at least one additional stud on each side of a broken one. If two or more break, all must be replaced. From this investigation experts have recommended (due to haul weights) that in the event of even a single stud failure, all should be replaced and all additional wheel end components checked for issues.
  • The location of these cracks would have been extremely difficult to detect unless the wheels were off for maintenance. It is critically important that when wheels are off to change tires or complete other maintenance their components are assessed for damage and replaced if necessary (the age of these cracks was estimated to be at least one year old).
  • Work together with those completing maintenance and repairs, whether they be shops, yourself, or a mechanic you employ. Training and education on how to properly maintain your equipment is paramount and could have prevented this “wheels off” incident. The governing body that inspects the shops which perform this maintenance commercially have followed up and are working with them to ensure that training is provided to their employees.

 

File attachments
Safety_Alert_Cracked_Rims_wheels_off.docx
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