Abstract
Welding, a key technology in the shipbuilding industry, is mostly performed by hand, owing to the complex structure and shape of production blocks. This manual welding requires a variety of working postures, which have become an important determinant of the worker’s workload and, consequently, assembly man-hours. Currently, major shipyards calculate welding man-hours by reflecting the welding factor, which is defined as the working time consumed in the welding process. A set of welding factors is known to be based on the accumulated experience in shipyards, whereas the verification or derivation process for these factors is not disclosed or available. This study proposed a method for quantitatively calculating work difficulty for welding positions based on the working posture in a process where the posture acts as an important variable. Standard welding positions reflecting the actual welding work at shipyards were established. A physiological assessment method was used to propose the physical welding factor by analyzing the measured muscle activity. The validity of the proposed method was verified by comparing the results of a musculoskeletal simulation package and shipyard welding factors. The proposed method can be readily applied to other fields in which workers’ physical activities are involved.
Highlights
Ergonomic analysis, widely applied in physical therapy and sports training, provides a tool that achieves optimal performance while reducing the risk of human error or injury [1].Recently, ergonomic analysis has been required in various industrial fields, and in particular, the design of a more efficient and safe working environment has been emphasized from the workers’ perspective.Several studies have shown that the introduction of ergonomics improves working conditions and reduces the number of work-related musculoskeletal disorders, which increases work productivity and reduces related costs [2,3,4]
The left figure represents the amount of muscle activity of the erector spinae (ES) and splenius capitis (SpL) for each welding position, and the right figure compares the degree of contribution to the three working positions, considering αp,m
Three different factors were used to compare the degree of influence of the welding task: the welding factor used in Shipyard A, the result of the work attitude analysis by the musculoskeletal simulation package Anybody Modeling System® (AMS), and the physical welding factor proposed in this study
Summary
Widely applied in physical therapy and sports training, provides a tool that achieves optimal performance while reducing the risk of human error or injury [1]. There are cases where it is difficult to introduce automatic control owing to the nature of the processes For this manual work, it is necessary to consider the physical workload resulting from working posture. Manual welding requires different types of working postures depending on the assembly tasks, which results in a difference in the man-hours of each block assembly. This study proposed a method of quantitatively deriving a physical welding factor based on the workload evaluation, aiming at the manual welding position in the shipbuilding block assembly process. The numerical factor derived in this study explains the difficulty of a welding work, based on the reasonable assumption that the physical workload caused by the working posture has a decisive effect on the man-hour calculation system, similar to the role of welding factors. The obtained results are compared with those of the simulation analysis using a musculoskeletal system and welding factors of a shipyard to prove the usability of the proposed method
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