Evaluation of lifting tasks frequently performed during fire brick manufacturing processes using NIOSH lifting equations

A fire brick manufacturing company with a high prevalence of low back injuries was selected for analysis of lifting tasks using the 1991 revised NIOSH lifting equations. We analyzed several manufacturing processes: forming, heating and packing processes involving frequent lifting and lowering in asymmetric postures. A questionnaire survey showed that weight of the load significantly influenced the incidence of back injuries and that workers who reported to have experienced back injuries were older than those who did not experience them. Composite Lifting Indices (CLI) based on the 1991 revised NIOSH lifting equations were calculated for 14 tasks of the forming process and five tasks of the heating/packing processes. Calculated CLIs for the tasks ranged from 0.86 to 8.8 (average 2.73) in the forming process and from 3.7 to 18.9 (average 11.12) in the heating/packing processes. The majority of the lifting tasks in this company exceeded the recommended weight limit (RWL). The results suggest that the tasks should be redesigned ergonomically to eliminate the risk factors that may cause low back injuries. Most of the jobs under study could be redesigned to lessen the biomechanical stress simply by making horizontal locations closer to a worker or by reducing the asymmetric angles. Relevance to industry During fire brick manufacturing processes, asymmetric lifting activities are frequently performed in Korea. It is crucial and beneficial to both management and labor to evaluate such tasks ergonomically based on the 1991 revised NOISH lifting equations for identifying risk factors that may cause musculoskeletal disorders. (C) 2000 Elsevier Science B.V. All rights reserved.