Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
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SEPTEMBER 2017 • E&MJ; 81 www.e-mj.com OPERATING STRATEGIES This improves the fl exibility in tim- ing designs enormously, according to the company, allowing for complex and effec- tive timing designs. Rock takes around 30 milliseconds to react to the energy of an explosion, de- pending on geology. This response time has led blasters to lengthen the timing delays in search of better results — and they have been rewarded. Blasting results have improved as the timing delays in- crease — delivering improvements in a number of areas including ore dilution control, through-seam blasting, under- ground blasting, trim blasting and drill pattern variation within a blast. The problem, however, is that the adoption of EDDs is not always followed by any innovation in blasting practice. "My experience is that when opera- tions convert from non-electric initiation systems to electronic detonators, there is a reluctance to give up the familiar 17 x 42 millisecond or 42 x 67 milli- second combinations, and miners im- pose these delay periods on EDDs," he said. "This restricts the benefi ts of elec- tronics to only the accuracy component and ignores the much more powerful fl exibility component." To achieve less ore dilution, for ex- ample, the advanced programming ca- pability of EDDs needs to be harnessed. For example, using BME's BlastMap III design software with AXXIS electronic detonators, a complex timing design can be transferred from a computer directly to the detonators. "The advantages with this type of tim- ing is that it provides strong visual cues for the loading teams," he said. "It also makes sure that displacement across ore and waste boundaries is limited, thus pre- venting dilution." Through-seam blasting is another valuable innovation, not yet used much in South Africa, but successfully employed in the U.S. and Australia. The principle is to separate the charge in the reef and the charge in the overlying waste with an aggregate "waste deck." The charges in the overlying waste are fi red fi rst, followed by the charges in the reef zone a few sec- onds later. This can only be achieved us- ing EDDs, as the fi ring of the top layer cuts off the downlines to the detonators in the layer below. "A time lag of a few seconds allows the waste to settle back on top of the reef, so that when the reef charges fi re, the overlying waste effectively blankets and confi nes the reef portion of the blast and thus prevents heave and dilution," Rorke said. Rorke urged mines to actively explore the power of EDDs to achieve timing de- signs and results that are simply not pos- sible with non-electric initiation systems. BME has operations in more than 23 countries including Australia, Singapore, Indonesia, Columbia and 14 countries in Africa. Follow These Tips For Lasting OTR Sidewall Repairs Monafl ex, which specializes in develop- ing systems for the repair and vulcani- zation of tire damage, emphasizes to its customers that correct sidewall main- tenance and repair is a crucial part of maximizing the lifespan of OTR tires and minimizing time lost due to unforeseen issues and failures. The sidewall is a vital component of the tire's construction, providing protec- tion to the casing and absorbing the im- pact from movement and the terrain. Physical sidewall injuries can be espe- cially common in rocky environments with cuts from sharp outcrops of rocks and loose rocky material left on the haul roads. According to the company, following these tips will help maximize the effi cacy of a tire repair operation and the life span of tires: Training is key – The art of OTR tire repair requires technicians to make multiple judgments about the viability of a repair scenario. Robust processes and regular training in both repair practices and the systems in use are absolutely essential ensuring best practice is adhered to. Look for suppliers who offer ongoing training and support. Always adhere to your patch manufac- turer guidelines – Refer to the charts and consider the entire patch product range. Some manufacturers offer differ- ent products for specifi c applications. Choose the product that is best suited to the job at hand. Factor in the tire's service context – Un- derstand how the tire will be used when back in service. Tires used, for example, in severe service applications may need to be treated in a special way. Get the basics right – For a successful heat cure, double check that one has the right pressure, temperature and establish the correct cure time. Always check the non-repairable area fi rst – When measuring a sidewall injury, check the non-repairable area fi rst, other- wise risk wasting time on the rest of the inspection if the damage is located here. Watch out for the second sidewall ply in many radial OTR tires – Note that this second ply is a ply and not a carcass cord. It is present through about half of the sidewall from the bead toe on the outside of the tire. This ply turn will need special treatment (depending on the nature of the sidewall damage). According to OTR tire repair specialist Monafl ex, correct infl ation and avoidance of overloading are the primary ways to avoid early onset sidewall damage.