Designing lanterns for the efficient lighting of mine roadways - An experimental approach
The file is a zipped PDF document.No person can properly work without sufficient lighting and this is especially so in mines where conditions are difficult. Artificial lighting is very important for the night shift to provide a safe and efficient working environment. Haul roads within the pit are one of the critical areas in surface mines where lighting installations are not permanent due to regular advancement of the working face. The illumination design should fulfil the minimum lighting standards (illuminance level and uniformity) specified by various regulatory bodies. This is possible with the scientific designing of a lighting system. An unplanned illumination system may not provide satisfactory illumination. It may also incur high costs. In general, the practice in India is to use a single-sided haul road lighting arrangement with the mounting height of light sources varying from 8 m to 12 m. In most of the mechanized mines, high-intensity discharge (HID) lamps, like high-pressure sodium vapour (HPSV) and high-pressure mercury vapour (HPMV) lamps, are used for illumination, whereas in small, semi-mechanized mines, fluorescent tube lights (FTL) with HID lamps at junctions are preferred. The foremost important aspect of the lighting design is to provide sufficient illuminance to visually complete the task. During an illumination survey of a large mechanized mine, it was found that the illumination level varied and was not uniform throughout the length of the haul road. The light level at some patches was below the minimum light level standard.This paper deals with the critical analysis of a haul road 590 m in length. The illumination survey results show that the light level is high at one side of the road instead of at the centre. There were also different combinations of lamps, with the angles of the light arms varying from 35º to 70º. It was also found that these combinations were selected without any specific reason. To analyze the influence of design parameters on the distribution of light, an experiment was conducted with a fabricated telescopic light pole. The height of the pole was 6 m, with a telescopic range between 3 m and 6 m. The angle of the light arm can be varied from 0º to 90º vertically.For plotting the isolux contours of a fixed installation, the ground was divided into grids of 2 m by 2 m, covering an area of 14 m by 24 m. The illuminance level was measured at each grid point using a digital luxmeter. The analysis was done by plotting isolux contours for fixed installations and drawing graphs for various combinations of luminaries, reflectors, light arm angles and height of lanterns by plotting the horizontal angle of the light arm along the abscissa and contour area along ordinate.The results of the study show that the optimum range of the light arm angle for the side reflector is 20º to 30º, whereas for the pot reflector, the angle is higher, i.e. 30º to 45º. The isolux contours indicate that the pot reflector with a combination of tubular bulbs produces a wide distribution of light and contributes towards a reduction of luminaries when installed in longer roads. The elliptical and tubular bulb with the side reflectors favour the area lighting.The outcome of the study reveals that the design parameters of the lantern are mainly dependent on the type of luminaries. The combination of sources and reflectors and the area under the illuminance increases with the height of the lantern and the angle of the light arm from the horizontal.
Illumination, Lamp, Roadways, Lantern, Contour