Coal Age

SEP 2018

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September 2018 37 operating ideas continued bolter lights that use compact fluorescent lamp (CFL) technology. The Saturn light operates on 120 VAC and consumes about 12 watts of power compared to about 25 watts for a traditional roof bolter light. The Saturn has a useful lifespan of about 30,000 hours in contrast to about 8,000 hours from traditional CFL roof bolter lighting. The longevity of the Saturn also reduces the likelihood of maintenance-related injuries and reduces maintenance costs. To demonstrate the dramatic difference that the Saturn light provides, Figure 3 de- picts a comparison between the existing roof bolter lighting and a single Saturn light mounted on the rear and front of a walk-thru roof bolter. The existing roof bolter lighting uses CFLs with amber globes resulting in the yellowish-orange light seen on the left-side photos of Figure 3. The intent of the amber globes is to reduce glare. The Saturn emits a more natural white light and therefore does not rely on amber globes to reduce glare. Scientific Study To test the effectiveness of the Saturn, NIOSH conducted a scientific study on the detection of trip hazards and glare using the traditional roof bolter lighting and the Saturn light mounted on a walk-thru roof bolter. Thirty people participated in the study, with 10 people in each of the three age groups: young 18-25 years old; middle 40-50 years old; oldest > 50 years old. Age is an important factor because visual abil- ities generally decrease as age increases, and because the median age of a U.S. min- er is about 45 years. (NMA, 2016). Testing involved two phases, with Phase 1 and 2 testing locations depicted in Figure 4. Researchers selected the Phase 1 location because a lighting survey indi- cated that the end of the roof bolter walk- way had the lowest levels of illumination. Mineworkers travel through the walkway to carry materials to the front of the ma- chine. Researchers selected the Phase 2 location because it is where the miners conduct the drilling and bolting tasks. Trip hazard detection was tested using an electromechanical apparatus, designed by NIOSH researchers, that randomly pre- sented one of six dark-gray, tubular trip ob- jects 25.4 mm long with an outer diameter of 3.3 cm and an inner diameter of 2.2 cm. Trip hazard detection was quantified by the reaction time for the participant to see a trip object and by the number of times a partic- ipant did not see (missed) a trip object. Researchers also evaluated glare at the Phase 1 and 2 locations. Disability glare was evaluated using the Mars Letter Con- trast Sensitivity Test (Perceptrix, 2018). This standard test uses a chart of letters of decreasing contrast to assess contrast sensitivity. As disability glare increases, the ability to see low contrast letters decreases. The well-established De Boer 9-level rating scale was used as a qualitative method for determining discomfort glare. The rating scale ranges from one (unbearable glare) to nine (just noticeable glare). The value of five is assigned to "just acceptable glare." Results The study results indicated major im- provements in detecting trip hazards (Ta- ble 1) and significant reductions of dis- comfort glare when using the Saturn light at its full intensity (Sammarco et al., 2018). There were also drastic differences in the ability of people to see the trip hazards for the Phase 1 location, as quantified by trip object miss rates that were 41.7% when using the traditional light, compared to only 0.3% with the Saturn light. These miss rates are of critical importance because workers cannot avoid a trip hazard if they do not see it. Table 1 also lists the average detection time for the Saturn and traditional light- ing. There was a 48.1% and 10.2% reduc- tion in the average trip object detection time, respectively, for Phase 1 and 2 loca- tions with the Saturn light as compared to the traditional light. Note that the Phase 1 results are more dramatic than the Phase 2 results because the trip object illuminations were very different between the two phases. The Saturn light provided much greater illu- mination of the trip objects by a factor of 17.5 for Phase 1, thus enabling a dramatic reduction in average miss rate and detec- tion time, while the Saturn increased the illumination by a factor of 2.3 for Phase 2, resulting in a more modest reduction in average miss rate and detection time. Figure 3—The existing illumination provided by traditional lighting for a roof bolter (left). The improved illumination provided by the NIOSH-developed Saturn light (right). Photos by J.H. Fletcher & Co. Figure 4—Plan view of a walk-thru roof bolter and Phase 1 and Phase 2 testing locations. The circles indicate the locations of the participants, and the ovals indicate the field of view of the participants. Table 1—The average miss rate and detection time for trip-object detection.

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