Ergonomics assessment and intervention for handwheel valves operation process

The study aims to examine, assess and improve the effects of the handwheel valves operation process in the chemicals industry. This activity is a physically demanding activity which requires the plant operators to exert high force repetitively in awkward postures. Prolong exposure to these activities contribute to the increase of complaints and development of MSDs problems. In this study, Ergonomics Risk Assessment (ERA) tools such as Nordic Musculoskeletal Questionnaire (NMQ), Initial ERA checklists, Rapid Entire Body Assessment (REBA), Borg Rating of Perceived Exertion (RPE) scale assessment, Revised Strain Index (RSI) and Composite Strain Index (COSI) were applied. A total of 49 male plant operators from different nationalities (Jordan, India, Egypt) and various ages ranging from 22-52 years as well as 35 valves at different heights ranges (17 cm, 224 cm), direction (vertical, horizontal), with diameter sizes range (10.8 cm, 43 cm) were subjected to this study. The results of the ERA tools showed that awkward posture and forceful exertion risk factors during the process of actuating the handwheel valves exposed plant operators to a high level of MSDs risk. The NMQ results showed that the most affected body parts between the plant operators were for the ankles, lower back and upper back, hands and shoulders whereas the Borg RPE showed that the intensity of force exertion were 9.28, 6.51, 3.77, and 8.93 for handwheel valves at heights ground to the knee, knee to waist, waist to shoulder, and above shoulder respectively. As for REBA method the level of MSDs risk recorded a range between 9-11, 5-11, 5-7, and 6-10 for handwheel valves at heights ground to the knee, knee to waist, waist to shoulder, and above shoulder respectively. In RSI and COSI methods, the results showed that the level of Distal Upper Extremities Musculoskeletal Disorders (DUEMSDs) risk has an 11.894 score for the right hand and 12.191 score for the left hand. In order to improve the process, the ergonomics intervention was carried out by proposing four tools and reassessment were conducted. The Borg RPE showed that the intensity of force exertion had reduced to 6.04, 4.87, 3.46, and 6.85 for handwheel valves at heights ground to the knee, knee to waist, waist to shoulder, and above shoulder respectively. For REBA method, the risk was reduced to a range between 5-8, 5-7, 3-7, and 6-8 for handwheel valves at heights ground to the knee, knee to waist, waist to shoulder, and above shoulder respectively. Finally, the level of DUEMSDs based on RSI and COSI methods had reduced to 8.26 and 7.01 for the right hand and left hand respectively. In conclusion, the ergonomics intervention showed a significant improvement in minimizing the awkward posture and forceful exertion risks during the process of opening and closing the handwheel valves especially when the valves heights ranges between ground to the knee, knee to the waist, and above shoulder.