Height of Industrial Hand Wheel Valves Affects Torque Exertion
Objective: The aim of this study was to determine how height of a hand wheel affects maximum torque production and risk of injury to the shoulders and back of workers.
Background: Workers in the processing, refinery, and energy generation industries manually open and close valves with hand wheels that require high torque. This task is physically strenuous and can lead to shoulder musculoskeletal disorders (MSDs).
Method: Maximum torque exertions in the clockwise and counterclockwise directions at three heights (knee, chest, and overhead) were tested.
Results: The torque production in the counterclockwise (left) direction was greater than that of the clockwise (right) direction (150.5 N·m vs. 141 N·m). This main effect was independent of valve height, as there was no interaction between direction and valve height (p = .686). Participants exerted at least 10% greater torque at the overhead level than at the chest level (means of 153.2 N·m vs. 138.3 N·m). There was no difference in maximum torque between knee and overhead levels and between knee and chest levels.
Conclusion: According to ergonomics principles, the risk of MSDs affecting the shoulder and trunk from turning valves should be lowest at chest height because the postures of the shoulder and trunk are at or near neutral. However, workers exerted greatest torque when the valve was located overhead. Whether valves located at overhead height, compared with chest height, present greater risk of MSDs to workers is not known.
Application: Design engineers should avoid placing hand wheel valves at knee height or lower.