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Assessment of Fall-Arrest Systems for Scissor Lift Operators

Objective: The current study is intended to evaluate the stability of a scissor lift and the performance of various fall-arrest harnesses/lanyards during drop/fall-arrest conditions and to quantify the dynamic loading to the head/neck caused by fall-arrest forces. Background: No data exist that establish the efficacy of fall-arrest systems for use on scissor lifts or the injury potential from the fall incidents using a fall-arrest system. Method: The authors developed a multibody dynamic model of the scissor lift and a human lift operator model using ADAMS™ and LifeMOD™ Bio-mechanics Human Modeler. They evaluated lift stability for four fall-arrest system products and quantified biomechanical impacts on operators during drop/fall arrest, using manikin drop tests. Test conditions were constrained to flat surfaces to isolate the effect of manikin-lanyard interaction. Results: The fully extended scissor lift maintained structural and dynamic stability for all manikin drop test conditions. The maximum arrest forces from the harnesses/lanyards were all within the limits of ANSI Z359.1. The dynamic loading in the lower neck during the fall impact reached a level that is typically observed in automobile crash tests, indicating a potential injury risk for vulnerable participants. Conclusion: Fall-arrest systems may function as an effective mechanism for fall injury protection for operators of scissor lifts. However, operators may be subjected to significant biomechanical loadings on the lower neck during fall impact. Application: Results suggest that scissor lifts retain stability under test conditions approximating human falls from predefined distances but injury could occur to vulnerable body structures.