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What Causes Equipment Accidents?

In reviewing the NIOSH website (National Institute for Occupational Safety and Health) I ran accross this interesting summary of study NIOSH performed a few years back.

One study by the former U.S. Bureau of Mines (now NIOSH) found that equipment was involved, to some degree, in one-half of the underground mine accidents analyzed. (1) Equipment was considered a primary causal factor in almost 11% of the cases and a secondary causal factor in another 10% of the cases. Equipment was implicated for:

  • Poor original design or redesign
  • Control-display layout
  • Inadequate ingress/egress design
  • Exposed wiring and hot surfaces
  • Exposed sharp surfaces or pinch points
  • Restricted Visibility
  • The equipment involved ran the gamut of underground mining machinery: roof bolters, continuous miners, belt conveyors, scoops, shuttle cars, locomotives, and utility vehicles. Significantly, the people involved in the study believed that in 38% of the cases modification of the equipment would reduce the probability or severity of the accident or injury.

    The U.S. Bureau of Mines also looked at studies on how engineers really design. (2) These studies showed that engineers almost immediately start to design equipment with little consideration about how the equipment is to be used by the operator, the sequence of use, or which functions are most important or most frequently used. The engineers relied overwhelmingly on designs used before, which prevented them from using novel designs. Furthermore, there was reluctance to modify their initial designs, except in minor respects, even when new information was made available to them. For example, halfway through one design process, plans were changed so that rather than four people to operate a console, there would be only two. Nevertheless, the engineers made only miner changes to the placement of displays and controls, with no important revision to the design.

    One overall conclusion of the studies was that no matter how much expertise the engineers had or the type of design problem being considered, the typical engineer does not consider human factors when designing. This failure occurs because all too often engineers do not recognize that the system consists of human beings, machines, and the environment that must work together to achieve a goal that could not be accomplished by these components independently.

    There are human capabilities and limitations that must be addressed when designing equipment. For instance, when dealing with operator visibility, the designer must consider the illumination required to do the job, adaptation to changes in illumination levels, color detection, field of vision, visual acuity and detection of movement. For hearing, being able to tell what direction the sound is coming from and to distinguish between the tone and intensity of sounds is important. Other factors that must be considered when designing equipment are memory, decision-making, focusing attention, reaction time, movement time, movement accuracy, anthropometrics, range of movement, strength, and endurance.

    References
    Sanders, M. S., and B. E. Shaw. Research To Determine the Contribution of System Factors in the Occurrence of Underground Injury Accidents (contract J0348042, Essex Corp.). USBM OFR 26-89, 1988, 165 pp.; NTIS 89-219638/AS.

    Sanders, M. S., and J. M. Peay. Human Factors in Mining. USBM IC 9182, 1988, 153 pp.

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