Investigator warns bearings failures cause fires

By: Steve Skinner


Accident investigator warns operators and drivers to be diligent when it comes to wheel end monitoring and maintenance

Investigator warns bearings failures cause fires
The result of a trailer catching fire after wheel bearing failure, which caused chaos on a major Sydney motorway.

 

A leading technical expert is warning the trucking industry of the significant risks of wheel-offs and wheel-related truck fires.

Wheels, bearings and tyres were a major focus of the most recent Technical and Maintenance Conference (TMC) in Melbourne.

The conference is organised every year by the Australian Trucking Association, Paccar and the Australian Road Transport Suppliers Association (ARTSA).

ARTSA president is engineer Dr Peter Hart, from Hartwood Consulting.

Amongst other things Hartwood does a lot of forensic accident investigation work, and a lot of that involves truck and trailer wheels.

Hart presented some pretty shocking statistics on the prevalence of fires related to wheels and tyres, and on wheels coming off.

The main culprits from his experience are not surprising: bearings; tyres; and nuts and studs. Bodgy brake actuators also feature when it comes to starting fires.

Hart concludes that wheel end fires are mainly due to wheel bearing failures causing the brakes to rub; rubbing brakes due to air system problems; deflated tyres rubbing and getting hot; and tyres rubbing on metal due to deflated suspension.

BAD BEARINGS

Hart says it’s usually the outer bearings that fail, resulting in dragging brakes. Then the usual fire mechanism is that the brake drums get red hot and heat spreads to the tyre rims via aluminium wheels.

Hart points out there are several causes of bearing failures.

For one, excessive bearing preload causes the outer bearing to get hot. And unfortunately it’s hard to pick when the bearings are too tight. On the other hand, loose adjustment results in bearing collapse.

Hart showed TMC delegates graphic photos of a B-double trailer which caught fire in Sydney because of bearing failure.

"It closed the M4 in Sydney for a morning and the costs involved in this fire are astronomical," Hart said.

The conclusion was that even though the bearings were only six weeks old after a recent service, they had been done up too tightly.

Water getting into the bearing lubricant is another problem, for example after fording a creek or driving through floodwater.

"We had a big boost in wheel bearing problems as a result of the Queensland floods," Hart recalled. "Trucks go through water, water gets into grease, grease no good."

Then there is poor maintenance leading to bearings wearing out; lubricant getting too old; and having no lubricant at all, because of broken hub caps and failed seals.

Hart presented a checklist of what to do to prevent wheel bearing failures, including:

  • Lift each wheel end at every service and shake and spin the wheel.
  • Get drivers to report all ‘fording’ events, and change the grease.
  • The obvious of being diligent with maintenance and using quality bearings.
  • Training drivers to inspect the wheels at every stop, which Hart concedes could be controversial.

The traditional method of driver checking is of course is to fleetingly feel each hub with the back of the hand.

But fellow engineer and forensic investigator Dr Shane Richardson, from Delta-V Experts, told the conference that a couple of operators he knows in WA have given their drivers the much more scientific thermal laser guns, to do a temperature check at every stop.

"If they can see a 10 degree difference in a set, that’s a criteria to report them," Richardson said, adding this "$200 tool" is a good investment.

Richardson added that pre-set hubs – as opposed to the traditional manually adjusted hubs – are performing "really well".

Check out the full feature on wheels and tyres in an upcoming issue of Owner//Driver.

 

 

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