Citation

Mital A, Motorwala A. Int. J. Ind. Ergonomics 1995; 15(4): 285-296.

Copyright

(Copyright © 1995, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Twenty males and 20 females participated in a study undertaken to provide an ergonomic basis for deciding between the conventional steel access cover (less expensive and heavier, and therefore undesirable) and a new composite access cover (relatively more expensive but lighter, and therefore more desirable). The results indicated that the conventional steel cover (weighing 80.35 kg and 91.44 cm in diameter) is too heavy for safe manual handling. The steel cover weight not only exceeded the average individual psychophysical lifting capacity of males and females (33.83 kg and 29.56 kg, respectively), it exceeded the average psychophysical lifting capacity of two-member male and female teams as well (76.04 kg and 67.08 kg, respectively). The spinal compression, if lifting the steel access cover was permitted, would have been approximately 13210 N for individual lifting and 6190 N for team lifting. Only 4 males were able to lift the composite access covers (weighing 38.13 kg and 91.44 cm in diameter) straight up using built-in handles, individually. The average spinal compressive force generated in this case (5849 N) also exceeded the spinal column strength of most males and females. Lifting the composite cover by a two-person team was found to be much safer (average spinal compression for team lifting the composite cover = 2501 N) and is a viable solution. The factor of safety for team lifting the composite access cover is at least 36% for females and 56% for males. Removing the composite cover individually using a rod type handle (unseating the cover by first rotating it and then pulling it for removal) resulted in somewhat greater physical stress (21.33 kg vertical force and 2898 N spinal compressive force) than lifting it by a team but, on the average, provided a factor of safety of at least 49% for males and 26% for females. Removing the composite access cover with the aid of the rod handle was also perceived to be "light" (average RPE value of 10.25 for males and 10.00 for females).