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Young worker seriously injured when steel truss fell from sawhorse

Date of incident: August 2020
Notice of incident number: 2020178260015
Employer: Heavy equipment company

Incident summary
A young and new worker was using an angle grinder to cut tack welds that were temporarily securing a support beam (strongback) to a steel truss. The truss and the attached strongback were placed on sawhorses, and the worker was cutting the tack welds from underneath. When the worker cut the 5th of 10 tack welds, the strongback separated from the truss. Both the strongback and the truss fell on the worker, who sustained serious injuries.

Investigation conclusions


  • Improper orientation of sawhorses. The worker was cutting upper and lower tack welds that were securing a steel truss to a strongback. The truss and the attached strongback were supported by improperly placed sawhorses. Two sawhorses on the opposite side of the strongback were placed perpendicular to the truss, which is an industry-accepted standard, and one sawhorse was placed parallel to the truss and strongback, supporting the strongback only. When the last lower tack weld was cut, the upper tack welds were not sufficient to hold the strongback to the truss, and the strongback broke away from truss. Both the truss and the strongback fell on the worker.

Contributing factors

  • Inadequate information and instruction. The employer did not have a policy or procedure for young or new worker training and orientation. The employer ought to have provided an orientation specific to young or new workers when the worker was hired but didn’t. The employer’s new worker orientation presentation, provided later, when the worker was assigned to a different work location, was inadequate as it did not provide orientation and training on how to recognize the hazards of cutting tack welds, nor on the employer’s occupational health and safety program, the location of first aid facilities, or who the first aid attendant was for the worksite.
  • Inadequate supervision. The worker was left to work alone on the truss and strongback after a discussion with the supervisor about the basic steps of how the strongback was to be removed from the truss. The sawhorse under the strongback was inappropriately oriented and not providing adequate support for the truss and strongback. In addition, the employer did not provide any supervisory training to the supervisor.
  • Lack of safe work procedures. Although the employer had safe work procedures in its new hire package, it did not have any written work procedures for removing tack welds from a strongback or placing sawhorses to support a load.
  • Lack of hazard assessment. The employer conducted general morning safety meetings but did not have a process for conducting task-specific hazard assessments. A hazard assessment was not conducted to identify, control, or communicate the hazards of cutting tack welds used to hold a strongback to the truss.

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Publication Date: Jun 2022 Asset type: Incident Investigation Report Summary