VALVE OPERATOR BIOMECHANICS WITH RESPECT TO HANDWHEEL DIAMETER AND ORIENTATION – AN ELECTROMYOGRAPHY ANALYSIS

Abstract

Handwheel operated valve systems are prevalent in numerous industries, including the petroleum, chemical, power generation, water supply, and waste processing industries. The function of handwheels is primarily to regulate the flow of material within a valve. In many cases, the torque required to manually turn a handwheel far exceeds operators’ strengths, reducing operators’ efficiency and posing risk for musculoskeletal disorders. Furthermore, handwheels of various diameters and orientations are common in a typical plant as there is no standardized design for handwheels. Therefore, the objective of this research was to assess the effects of handwheel diameter size and orientation on user preference and biomechanics, in order to identify a design that reduces and/or distributes biomechanical loads across the body. An electromyography (EMG) device was utilized to assess biomechanical loadings acting on the upper extremities, shoulders, and back muscles. Twenty healthy male participants were recruited from the student population at the American University of Beirut. Four handwheel diameters were examined (35, 45, 60, and 70 cm), each at three different orientation angles (0, 45, and 90 degrees from the horizontal). For each diameter-orientation combination, participants were asked to gradually increase their force production up to a fixed torque level. The maximum EMG amplitude generated by each muscle of interest were recorded. Three repetitions were performed at each handwheel condition, and the average EMG recordings of the three repetitions were analyzed. In addition, at each handwheel orientation, participants were asked to rank the handwheel diameter sizes in terms of comfort and ease of generating the targeted torque. Then they were asked to rank the “winning” handwheel conditions to determine the overall most preferred handwheel diameter-orientation combination. Our results show no interaction between handwheel orientation and angles. However, biomechanics stress on studied muscles were lower at larger handwheel diameters. Vertically oriented (90°) handwheels were found to be associated with the lowest EMG activity. A tradeoff between user biomechanics and user perceived preference/comfort was noted as necessary for determining an optimal handwheel.