Physical Welding Factors for Reclassified Welding Positions in Shipbuilding Assembly Process Based on Muscle Activity Measured by Surface Electromyography

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.