The design and evaluation of an ergonomic valve-wrench

Abstract

BACKGROUND: The torque required to manually turn a handwheel-valve typically exceeds operators’ capabilities, requiring them to use a valve-wrench. Although valve-wrenches are commonly used, an ergonomic wrench has not yet been developed. OBJECTIVE: To introduce an ergonomically designed valve-wrench and evaluate it with respect to conventional valve opening methods. METHODS: Four methods were compared including: bare hands, restricted conventional wrench (assumes presence of obstructions), unrestricted conventional wrench, and ergonomically-modified wrench. Each method was performed at two torque settings, 15 Nm and 30 Nm. Electromyography activities were measured from eight trunk and shoulder muscles. The time to fully open the valve and Borg-ratings were recorded for each method. RESULTS: The modified wrench resulted in the lowest average time and Borg-rating; however, these averages were not significantly different from the averages of the unrestricted conventional wrench. The method that was associated with the lowest overall electromyography activities was restricted conventional wrench, followed subsequently by bare hands, modified wrench, and unrestricted conventional wrench. CONCLUSIONS: Although the ergonomically-modified wrench was associated with relatively high electromyography activities, it was the most time-efficient method, allowing the muscles to sustain physical loads for shorter periods of time. Overall, participants rated this method as the least physically demanding.