The ergonomic analysis of valve adjustment tasks for refinery unit operators at Kock Petroleum Group, St. Paul. Minnesota

Abstract

Refinery Unit Operators are routinely required to manually open and close valves that control the movement of fluids through pipes. At KOCH Petroleum Group, St.Paul, Minnesota, a total of 203 operators were assigned to this position and work in thirteen different units. These operators were responsible for monitoring and operating refinery process units. The most often tasks were opening and closing valve, which occurs when shutting down and starting up units. These tasks tend to generate shoulder injuries in operators while turning valve at eye-level or overhead many times a day. There are ergonomic risk factors associated with posture and force including poor shoulder postures and excessive force use. The body- positioning problem has the potential for inducing shoulder musculoskeletal injuries in varying degrees of severity. This study analyzes ergonomic risk factors involved in valve adjustment tasks and identifies potential high-risk valve types from three selected valves based on ergonomic risk factors when operators turned each individual valve. An in-charged Pumper Unit operator was selected for this analysis. Three different types of valves categorized by the stem direction criteria (chain loop, horizontal, and vertical gate valve) were selected for testing. The primary method of research used to complete this study was ergonomic instrumentation analysis. Penny and Giles M series twin-axis electronic goniometer, a force gauge, and a video camera were used to obtain the degree of shoulder movement in each operational cycle (opening/closing) and the amount of force required to turn the valve. Data analysis was performed by a combination of using Penny and Giles M series twin-axis electronic goniometer computer analysis program, testing data from a force gauge, and a visual analysis of body movement from the videotape. Significant effects that lead to shoulder injuries have been found. The results indicated that excessive force required to turn valves, and shoulder abduction (arm pulling away from the body) plus backward shoulder movement were the major ergonomic risk factors involved in turning valve operations. These findings have a particular occurrence depending on the types of valve. The chain loop gate valve is the highest risk valve type due to the greatest application of required force and highest degrees of shoulder abduction. Engineering controls such as redesign of the valve installation points or adding torque chain loop, as well as administrative controls; implementing a hazard assessment program, training, and acquiring design guidelines for torque specification in place for eliminating are recommended for prevention methodology evolution.