Shredding light on the mine site
Proper design of haul road lighting systems is essential to the efficient and safe operation of an open cut mine . At a surface mine covering many square kilometres of land ; where work is carried out round the clock ; systematic arti cial lighting is necessary in order to provide a safe and efficient working environment . Haul roads within the pit are one of the most critical areas for lighting at an open cut mine . One of the most important issues is that haul road lighting installations are not permanent due to regular advancement of the working face . Another major problem is dark surroundings and low surface re ectance . Due to these reasons it is very difficult to maintain lighting standards speci ed by various regulatory bodies . A good lighting system is one which can distribute an appropriate amount of light evenly with uniformity values from 0.25 to 0.40 and with a colour rendering index of at least 60 . Good lighting will use energy efficient lamps in suitable luminaries . Mine safety guidelines suggest a minimum horizontal illuminance level of 0.5 lux in haul roads however in reality uniformity ratio is also essential in the design of illumination systems for uniform distribution of light and to provide sufficient illumination for visual tasks . In these conditions , the use of compact uorescent lamps ( CFL ) with a stand-alone lighting system is perfectly acceptable . Standalone photovoltaic lighting systems provide exibility for changing the location of poles according to changes to surface mine haul roads . However CFL ' s electrical requirements are not easily met by hard-switched inverters due to higher switching losses at higher frequencies . �e difficulty in meeting the complex electrical requirements , such as preheat and ignition voltage of CFL , results in lower efficiency . In order to make a successful photovoltaic lighting system , the rst step is to select a well-suited high-frequency inverter and a series interrupting type charge controller for producing good light while maintaining reliability .
PRINCIPLES OF HAUL ROAD LIGHTING MOUNTING HEIGHT Luminaire mounting height depends on the lighting arrangement and effective road width . �e effective width is the horizontal distance between the luminaire and the far curb . To achieve a good distribution of light across the roadway , mounting height in general is kept equal to the road width or around it .
SPACING Luminaire or pole spacing for a given lighting arrangement and luminaire light distribution is dependent on the mounting height and the longitudinal uniformity planned for the installation . �e greater the mounting height , the larger can be the spacing for a given longitudinal uniformity . Longitudinal uniformity is the ratio of minimum to maximum illuminance along a line parallel to the road axis through the observer ' s position . However , in practice , excellent illumination is considered to be
Page38 | Jan - Feb 2016
| FMDZ