2009-01-15 Trailer Brakes Malfuntion Results in Rollover

Safety Alert Type: 
Log Hauling
Upper Similkameen
Date of Incident / Close Call: 
Company Name: 
Weyerhaeuser Company Ltd.
Details of Incident / Close Call: 

On January 15, 2009, a loaded logging truck entered a curve on a logging road when the trailer brakes unexpectedly locked up. The forward momentum of the trailer caused it to run straight, forcing the truck and trailer off the running surface. The trailer tipped over the bank followed by the tractor unit. 

The investigation concluded that the emergency port screens were plugged with dirt likely causing the trailer brakes to lock-up.


  • Dirt and debris can get into air systems if connections are left exposed.
  • When air is compressed, it’s temperature rises. With a truck air compressor operating at a pressure of 120 p.s.i (827 kPa), the air temperature as it leaves the compressor is over 2040C (4000F). As a result, the air that is delivered from the compressor usually contains some water vapour that condenses into liquid water. Most compressors also pass a small amount of oil, and carbon particles. The oil and any other contaminants mix with the water, making a grey sludge. Most contaminants settle in the supply reservoir. If allowed to accumulate, this sludge would enter other components of the braking system.
  •  In winter, water in the system may freeze causing the malfunction of valves or brake chambers.
  • Break failure occurring in the wrong place and time can lead to a serious incident.



  • Most manufacturers recommend that reservoirs be drained daily, preferably at the end of the day.
  •  Even if the air brake system includes an alcohol evaporator, or alcohol injector, air reservoirs must still be drained daily.
  • Change air dryer filter cartridge as per manufacturer’s recommendations. Bendix, for example, recommends every 900 hours or 40,000 km for some of their filters.
  • When not in use, glad hands should be fastened to dead-end (dummy) couplers or to each other to prevent dirt and debris from entering the air lines.



For more information on this submitted alert: 

Weyerhaeuser Company Ltd.

Peter Forbes, RPF

Logging Supervisor


File attachments
2009-01-15 Trailer Brakes Malfunction Results in Rollover.pdf
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