The Effect of Rigid Container Shape on Maximum Acceptable Weight of Lift

Abstract

In the chemical, pharmaceutical, and paint manufacturing industries raw and finished materials are frequently shipped in cylindrical rigid containers instead of boxes. Psychophysical manual materials handling lifting capacity studies to date have not considered whether rigid container shape has an effect on maximum acceptable weight of lift. Two psychophysical studies were designed and conducted in order to answer this question. During the first experiment ten subjects lifted boxes with three different heights, at three different frequencies, and through three different lift ranges in order to establish a data base in which to compare the results of the second experiment. During the second experiment the same group of subjects lifted cylinders with three different heights at the same frequencies of lift and through the same lift ranges as the first experiment. The subjects adjusted the weight of the box until they felt they could safely lift that weight for eight hours. This weight was the maximum acceptable weight of lift (MAWL). The experimental design for both experiments was a 3 factor randomized complete block design with blocking on subjects. The dependent variables were oxygen consumption (VO2), MAWL, and Borg's rating of perceived exertion. The results indicated that when one designs a lifting task for a rigid container the shape of the rigid container, whether a cylinder or a box, does not need to be taken into account and that current psychophysical lifting capacity prediction models can be used to design cylinder lifting tasks.