Mining Project: Underground Coal, Metal, and Nonmetal Mine Illumination Systems for Improving Miner Visual Performance

Research Summary

This project reduced traumatic injuries of underground mine workers. The project improved mine illumination such that mine workers' visual performance improved and they can better recognize slip/trip/fall hazards and pinning/striking hazards from moving machinery.

Currently, the success in avoiding these hazards is very limited and problematic. According to Mine Safety and Health Administration (MSHA) data from 2008-2012,  slips, trips, and falls (STFs) are the second leading accident class (19.1%, n=1,820) of nonfatal lost-time injuries at underground mining work locations. For this period, STFs resulted in 108,587 total days lost from work. MSHA data from 2008 through 2012 indicated 27 occupational fatalities and 2,213 nonfatal lost-time injuries occurred in the underground coal mining industry that were described with accident types of struck against stationary or moving object, struck by rolling or powered moving object, or caught-in-under-between a moving and stationary object or several moving objects.

This research generated new knowledge in the field of mine illumination, specifically new knowledge in the emerging technology of solid-state lighting as applied to mine illumination. The long-term goal of the research was to reduce traumatic injuries for falls of ground, slips/trips/falls, and powered machinery incidents where poor illumination is a contributing factor. The maximum target reduction in traumatic injuries is 25%; the minimally effective reduction is estimated to be 10%. The project's research objectives were as follows:

• Determine if solid-state lighting can be used to enhance visual performance with respect to the recognition of the hazards associated with falls of ground.
• Determine if visual performance, with respect to slip/trip/fall hazard recognition, is a function of the illumination system's chromaticity (light color).
• Determine if visual performance, with respect to peripheral motion detection for the recognition of pinning/striking hazards, is a function of the illumination system's chromaticity.
• Determine if glare is a function of the illumination system's chromaticity.
• Determine if the unique capabilities of solid state lighting afford better lighting distributions to light hazardous areas that are inaccessible or impractical when using existing mine lighting systems.
• Determine if auxiliary lighting can improve the detection of machine movements that could pose pinning/striking hazards or improve the detection of floor hazards.

The project conducted an analytical (comparative) study using traditional illumination technology and full-spectrum light generated by new solid-state lighting (SSL) technology. The project determined the effectiveness and feasibility of using SSL to improve the visual performance of underground mine workers at the mine face. Visual performance was quantified by measuring the number of missed (unrecognized) objects and the elapsed time for object recognition. Qualitative data was recorded by using a questionnaire instrument for subject perceptions of glare and visual acuity.

The project results, with respect to the objectives, indicated that solid-state lighting can enhance visual performance for recognizing falls of ground hazards, and that light color is a significant factor for slip/trip/fall hazard recognition, peripheral motion detection, and that light color affects glare. Specifically a light color having more short wavelengths (i.e. cool white) improved visual performance and reduced disability glare. Secondly, solid state lighting enabled better lighting distributions such that slip/trip/fall and peripheral hazard  illumination increased when using a cap lamp thus resulting in visual performance improvements for detecting hazards. Practical and field-worthy cap lamps where developed for the lighting distribution research. These cap lamps were developed: the NIOSH models GEN4, GEN4E, GEN 5, and GEN 5E. Lastly, auxiliary solid-state lighting on a continuous mining machine enabled improvements in detecting slip/trip/fall and pinning/striking hazards. Overall, the results of this research have the potential to improve the safety of mine workers by reducing traumatic injuries for slips/trips/falls and pinning/striking incidents where poor illumination was a contributing factor. The research also generated new knowledge assisting MSHA in approval and certification of mine illumination systems that employ the emerging technology of solid-state lighting. This new knowledge also benefits designers, installers, and those maintaining mine illumination systems.