การประเมินและการปรับปรุงภาระงานทางการยศาสตร์ในอุตสาหกรรมตีมีด

Abstract

This research aimed to evaluate and analyze the ergonomics loads in order to improve working conditions and reduce the ergonomics risks of workers who had strenuous work in hot environment in OTOP knife forging industry in Chiangmai. Ergonomics loads were evaluated by three main methods: 1) Observational assessment methods were performed using RULA and Strain Index technique. 2) Direct measurement methods were conducted by measuring heart rate, body temperature and heat stress (WBGT) in work area. 3) Subjective evaluation was assessed using discomfort level-questionnaire. The initial investigation indicated that for RULA technique, the working postures in most of tasks were in high risk (level 4). For Strain Index, the working conditions in forging task were the highest risk (SI Score 91.1 in intensity of exertion factor). The results from RULA and Strain Index were harmoniously with the discomfort level-questionnaire that forward discomfort happened at shoulder, upper arm and mid-to-lower back. For the analysis of heart rate when resting by Brouha’s criterion, it was found in normal workloads. Moreover, the body temperature of the workers in knife holding-task, forging task and knife hardening-task were founded more than 38°C which conformed to heat stress in work area that WBGT temperature was 33.3°C higher than the standard value. The working conditions were improved by 1) the design of new chairs to be more appropriate postures working to ergonomically, 2) change the condition in forging task from hit by one worker to hit by three workers in order to reduce workloads, 3) renovating the kiln to have higher wall to protect heat conducted from the kiln to the workers’ body, and 4) the workers were asked to wear the personal protective devices while working. Finally, the ergonomics risks can be reduced. After improvement, the risk levels of working postures were decreased to level 2, the Strain Index score was decreased to 20.3, the body temperature of the workers was decreased to 37.9°C, the heat stress in work area (WBGT) was decreased to the standard value of 30.5°C and all of the workers satisfied in the conditions that were improved as well.