Coal Age

SEP 2018

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36 September 2018 operating ideas LED Light Reduces Roof Bolter Lighting Glare by john j. sammarco Fortunately, there is an overall trend of in- creasing mineworker safety in the United States. One example is the rate per 200,000 hours worked of coal mining nonfatal lost- time injuries was 2.57 during 2009 and it reduced to 1.99 during 2015 (MSHA, 2015). Nevertheless, the need to improve mine- worker safety continues. With this goal in mind, National Insti- tute for Occupational Safety and Health (NIOSH) researchers are specifically focus- ing on lighting to improve the safety of roof bolter operators. Roof bolting is critical to se- cure the overlying roof strata. Unfortunately, there are also inherent hazards associated with roof bolting. During 2004 to 2013, there were 16 fatalities and 3,411 nonfatal lost- time injuries, accounting for 64.7% of inju- ries at underground coal mines (Sammarco et al., 2016). Put simply, roof bolter operators need to readily see the surrounding hazards so they can avoid them and work safely. Pro- viding effective lighting for these operators is a major challenge given that underground mines are one of the most difficult environ- ments to illuminate (Rea 2000). Historically, lighting roof bolters has been challenging given the machine's size, limited space for mounting lighting, and the possibility of ex- cessive glare due to the worker's close prox- imity to the machine lighting. Newer roof bolting machines employ a walk-thru design that enables the operator to walk back and forth through the center of the roof bolter to retrieve materials need- ed for roof bolting, and the design enables them to operate the machine from within the interior space (Figure 1). This newer de- sign improves worker safety by reducing ex- posure to hazards that result in miners being struck by the machine or pinned between the rib and the roof bolting machine; how- ever, tripping hazards are still present. The lighting of the interior work areas is critical. Anecdotal reports suggest that glare is a frequent complaint among roof bolter operators, and glare decreases the ability of the worker to see hazards. There are two types of glare: discomfort glare (annoying or painful sensation) and disability glare (impaired or reduced visibility). The issues with glare are not surprising given that the lighting fixture is often very close to min- ers working on and around roof bolters (Figure 1), and because many of the cur- rent lighting fixtures distribute light in all directions, resulting in some of the light shining into the mineworker's eyes. To address these challenges, NIOSH researchers developed the Saturn light, with the main objective of improving the ability of miners to see tripping hazards associated with the walk-thru roof bolter while not creating a glare hazard. A sec- ondary objective was to reduce the size of the light fixture to enable more flexibility for mounting on roof bolters — thus, new mounting locations could potentially pro- vide better illumination of hazards. The Saturn Light The Saturn light (Figure 2) uses an ar- ray of 12 cool white, downward-facing, light-emitting diodes (LEDs) with a sec- ondary optic to provide a highly direc- tional, uniform light distribution similar to roadway illumination from streetlights. The downward-facing orientation, in conjunction with the secondary optics, enables direct illumination of the surface where tripping hazards are located and re- duces the glare that "stray light" can cause. The Saturn light takes up only one-third of the volume compared to existing roof Figure 1—The walk-thru roof bolter design enables workers to operate the roof bolter within the machine's interior, thus reducing exposure to pinning hazards between the machine and rib. Photo by J.H. Fletcher & Co. Figure 2—The small size of the Saturn light enables greater flexibility in machine-mounting locations. Photo by NIOSH.

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