Ergonomic investigation of workers in tea factories using REBA and OWAS methods – case study: (Langroud Region, Guilan, Iran)

Work-related Musculoskeletal Disorders (WMSDs) are a leading cause of disability, work time loss and economic loss in both industrialized and developing countries. WMSDs include muscles, bones, joints, nerves and blood vessel disorders. According to the studies done by some researchers, lack of harmony between technology and the technology users in workplace can degrade the product quality and increase the injuries. In the present study, an ergonomic investigation was conducted and the position and posture of the workers of tea factories were evaluated. REBA and OWAS methods were used for analyzing the postures. The energy expenditure of workers was calculated by heart rate monitoring. In this study, 6 tea factories were considered and totally 48 workers were assessed. Production units of tea factories were classified into three categories, including withering unit, curling and oxidation unit and drying and grading unit. Results showed that 75 percent of used postures by the workers of tea factories need corrective measurements. Also, based on the OWAS results, 34% of used postures had high and very high risk level. Workers back flexion, placing one arm above shoulder and standing on one leg are the most important positions in tea factories that lead to musculoskeletal disorders. So the corrective measurements should be done to reduce them. Withering unit was the most energy-consuming unit for workers. The average of energy expenditure of tea factories workers was 21.843 kj.min -1 .