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Worker struck by chipper shroud

Date of incident: November 2014
Notice of incident number: 2014130750088
Employer: Wood products manufacturing company

Incident summary
A worker was preparing to change the knife assemblies of a waste wood chipper. The knife assemblies were secured to a 48-inch disc that turned on a shaft supported by external bearings located on both sides of the chipper frame. The worker turned off the chipper disconnect. In order to gain access to the knife assemblies, the worker removed the two bolts fastening the protective shroud to the machine frame. The disc was still rotating when the bolts were removed, and due to high vibration of the chipper, the shroud moved sideways and came in contact with the knife assemblies. The shroud was knocked open and struck the worker on the head, seriously injuring him.

Investigation conclusions
Cause

  • Chipper shroud struck worker as a result of uncontrolled hazardous energy: The worker removed the bolts fastening the top of the chipper shroud to the frame while the disc was still rotating. The shroud moved sideways toward the disc and made contact with the knife assemblies and fins on it. The shroud was propelled open, striking the worker in the head and causing serious injuries.

Underlying factors

  • Inadequate information and instruction: The training provided to the worker and the work procedures posted in the chipper room and near the power control panel did not include the hazards associated with kinetic energy and did not provide clear, specific instructions for shutting down and locking out the chipper. After the chipper power was turned off, it usually took about 10 minutes for the disc to stop rotating, and during this time there was the hazard of kinetic energy.
  • Performance of unauthorized work: The worker started work before his shift in order to change the chipper knife assemblies. Although he had completed the task more than 20 times previously, he was not authorized to do the work without oversight.

Request the full report

Publication Date: Jan 2017 Asset type: Incident Investigation Report Summary NI number: 2014130750088