Hand Fed Chipper Winch Line Accident

Biomechanical accident reconstruction analysis methodologies were used to address injury modes associated with human operator involvement with a commercial hand fed tree chipper winch line or auxiliary rope being pulled into the machine by the cutter drum at speeds in excess of 100 miles per hour. Various case studies are presented demonstrating the injury sequences of unwitnessed events. The injuries are used as physical evidence and analyzed in the scientific method along with the human factors of the operator, laws of physics, physical evidence of the site and machine, and the operator’s final resting position.

This research analyzes three separate chipper winch line accident reconstruction case studies involving the winch line or auxiliary rope being fed with the brush into the chipper. The first case study analyzes a hand injury sustained when a wire rope winch line cable cinched and became embedded in the worker’s hand. The second case study involves a worker decapitation incident involving an auxiliary rope that was pulled into the tree chipper. The third case study addresses a chipper operator that sustained a left hand and right foot amputation injury as well as head and neck injuries due to a wire rope winch line cable being rapidly pulled by the cutter drum. The biomechanical accident reconstruction analysis utilized a male surrogate and an exemplar chipper equipped with a wire rope winch line. Based upon the biomechanical accident reconstruction analysis, an animated sequence of the accident is developed.

The three chipper winch line/auxiliary rope accident reconstruction case studies presented in this research address body entanglement/shear injury mechanisms where the winch line or auxiliary rope is rapidly drawn into the chipper by the cutter drum. Biomechanical accident reconstruction analysis that is based on the scientific method and utilizes the physical evidence (including the injuries) and laws of physics is a useful tool for determining accident sequences. In essence, biomechanical accident reconstruction analysis “tests” accident sequence theories with the available evidence. Finally, following the chipper winch safe work practices provided in chipper manufacturer’s instructions, Tree Care Industry Association chipper operator training program and safety literature, ANSI Z133.1 safety standard requirements, and OSHA regulations will contribute to reducing tree worker winch line and auxiliary rope injuries.

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