HAZARD ALERT : Cab Tilt System Failure

Safety Alert Type: 
Mechanical Service (Field)
Location: 
Coastal British Columbia
Date of Incident / Close Call: 
2015-09-26
Company Name: 
Nootka Sound Timber Co. Ltd.
Details of Incident / Close Call: 

Mechanics were sent out to check the cab tilt system on a Madill 3800c. They found wiring needing repair for the system to function. After the repair was made, the cab was cleared of equipment & debris and anchor bolts were removed.

The cab tilt function was engaged and the cab began to rise as it should. When the cab reached an elevated level of approximately 6” it fell forward extremely fast. The mechanics immediately tried to reverse the cab by pushing the button in the opposite direction but it continued forward until it struck the track and the ground. In the process, the anchor strap came tight and broke under the strain.

At that point the house cylinder was over-extended and the rod was pulled from the cylinder (see photos in attached pdf), breaking at the piston retainer nut. Both mechanics were in the clear and were not injured in the incident. The investigation determined that there was no oil in the hydraulic cab tilt cylinder. Having no fluid to restrict the piston in the cylinder, there was no way the weight of the cab would be supported. It was also determined that the house /cab hydraulic power pack had been replaced at some point so the likelihood of air in the system was high.

This particular cab had not been tilted in a long time, factors which were not considered before lowering the cab.

Learnings and Suggestions: 
  • If a particular machine has not had a cab tilt function performed in considerable time, the cylinder rod should be unpinned and completely cycled to purge the system, and ensure the system is operating correctly before performing the actual cab tilt function.
  • Any time repairs have been made to the house / cab hydraulic power pack, the system must be purged to ensure all air is removed from the system and that fluid levels are adequate.
  • Amend relevant Job Safety Breakdown procedures to reflect the above findings.

 

For more information on this submitted alert: 

Virginia Mountan (250) 830-2292

File attachments
Safety_Alert_Nootka_Sound_Timber_2015-9-26.pdf
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