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Computer Design and Evaluation Tool for Illuminating Underground Coal-Mining Equipment
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    Introduction Industrial safety professionals recognize that adequate illumination is essential to a safe and productive work environment. The need for effective, lighting in underground coal mines is even greater.1 Designing appropriate lighting systems for these mines is no easy [ ] task because of the unique environment and work procedures encountered in underground coal-mining operations. Miners must depend totally on artificial lighting systems to see. Moreover, the working face is a low-reflectivity and low-contrast environment and is continually advancing or retreating.2 Laboratory mock-ups have been a major part of the process lighting equipment manufacturers must under- go to design an underground machine-mounted lighting system. The mock-ups often have taken considerable time. Furthermore, modifications to a lighting system (using different luminaires with an existing configuration or changing a luminaire's location, orientation, etc.) could require more time with additional mock-ups and laboratory measurements. Understanding the need to improve this situation, the US Bureau of Mines has developed an alternate method for facilitating lighting system mock-ups. A PC-Program (CAP),* with the latest software technology enables users to design, alter, and evaluate under- ground machine-mounted illumination systems. Lux levels and distance are measured as the luminaire is moved incrementally through angular traverses about horizontal and vertical axes. The measurements and angles subsequently are entered into the model. From this input data, three-dimensional isolux or isofootcandle profiles are constructed for luminaires that can be placed at various locations and orientations on a mining machine. As an example, Figure 1 shows a computer display of 21.5 Ix or 2.00 fc profiles for luminaires mounted on a simulated mine-shuttle car. Using this information, the model allows the user to determine the lux level at different locations in space about the shuttle car. How the model calculates illumination During initial development of the CAP model, the isolux profile of the luminaire was determined using the inverse square law (ISL) .3 The method of gathering data comprised recording a single measurement of distance at 21.5 ± 1.21x (2.00 ±11 fc) for angular traverses following 0.09 rad (5 degree) increments. This data was then used to find the illumination in space for any other distance at a given azimuth and elevation using the ISL. Limitations, however, exist with this method.4 The main one is that the ISL assumes a luminaire is a single point source of light, so long as the distance is greater than five times the 1al;gest dimension of the luminous area of the luminaire.5 Also, by using a single measurement to calculate the illumination for a given luminaire in the CAP model a large error could result from an inaccurate measurement.

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