Effect of Handwheel Height and Angle on Operators' Torque Production Capabilities

OCCUPATIONAL APPLICATIONS From investigating the maximum isometric torque exertions of participants on a handwheel set at different heights and angles, it was determined that torque production capability is greatest when the handwheel is set overhead at 45° and is lowest when overhead at 0°. The mean torque production capacity of the participants was substantially lower than the torque demands in the field and in existing standards. Therefore, maximum recommended torque that accommodates the strength of most of the male population was determined for each handwheel height and angle investigated. The findings of this study may be useful for forming guidelines for handwheel-valve system designs, such as in standardizing the height and angle of a handwheel and defining a maximum recommended torque for handwheel-valve systems. TECHNICAL ABSTRACT Background: Handwheel-valve operation is a common task in many workplaces, including power, chemical, water, and oil industries. Handwheels of various angles and heights are common in a typical plant. The torque required to turn a handwheel differs from one valve to another, and there are no well-established torque standards derived specifically from operators' capabilities. Purpose: The purpose of this research was (1) to determine the effects of handwheel height and angle on torque production and (2) to propose maximum recommended torque limits for valve systems. Methods: Sixty male and female college students participated. Handwheel heights included knee, elbow, shoulder, and overhead levels, while handwheel angles included 0°, 45°, and 90°. At each height–angle combination, maximum isometric torque exertions on a handwheel were measured. These data were used to compute maximum recommended torque limits using the 25th percentile torque strength values of the female participants. Results: The mean maximum torque exertions ranged from 51.6 Nm (overhead at 0°) to 74.9 Nm (overhead at 45°). The height–angle and height–gender interaction effects were statistically significant. Male participants produced significantly greater torques (88.1 Nm) than the female participants (44.7 Nm). The 25th percentile torque strength values ranged between 25.2 and 38.9 Nm, depending on the height and angle of the handwheel. Conclusions: The relationship between torque production and handwheel height depends on the handwheel angle and vice versa. Overall, torque production was greatest when the handwheel was at shoulder or overhead levels, at either 45° or 90°, and lowest when overhead at 0°. The mean torque production capacity of the participants was substantially lower than torque demands in the field and even existing standards (about 40% lower). Maximum recommended torque limits for handwheels that would accommodate most of the male population's strength are proposed.