In recent years, commodity prices have swiftly decreased, narrowing the profit margin for many mining operations and forcing them to find effective cost management strategies to respond to low prices. Given that equipment is one of the most significant assets of a mining company, efficient equipment utilization has strong potential to reduce costs. This paper focuses on the relationship between the number of available drilling machines based on reliability analysis and the number of holes to be created on a bench of an open pit mining operation. Since equipment availability is random in nature, a range of holes to be drilled corresponding to a specified probability level was determined. To assess the performance of the proposed approach, a case study was carried out using two stochastic modeling techniques. Evolutions of reliabilities of 10 rotary drilling machines over a specific time were simulated by Markov chain Monte Carlo and mean reverting processes, using historical data. Multiple simulations were then used for risk quantification. Results show that the proposed approach can be used as a tool to assist production scheduling and assess the associated risk.
To gain a competitive edge within the international and competitive setting of coal markets, coal producers must find new ways of reducing costs. Increasing bench drilling efficiency and performance in open-cast coal mines has the potential to generate savings. Specifically, monitoring, analyzing, and optimizing the drilling operation can reduce drilling costs. For example, determining the optimal drill bit replacement time will help to achieve the desirable penetration rate. This paper presents a life data analysis of drill bits to fit a statistical distribution using failure records. These results are then used to formulate a cost minimization problem to estimate the drill bit replacement time using the evolutionary algorithm. The effect of cost on the uncertainty associated with replacement time is assessed through Monte-Carlo simulation. The relationship between the total expected replacement cost and replacement time is also presented. A case study shows that the proposed approach can be used to assist with designing a drill bit replacement schedule and minimize costs in open-cast coal mines. Keywords Cost minimization Á Drilling operation Á Optimum replacement time Á Evolutionary algorithm Á Sensitivity analysis Á Monte Carlo simulation List of symbols a Scale parameter (Weibull distribution) b Shape parameter (Weibull distribution) C f Cost of failure replacement C p Cost of predicted replacement C t Total cost of expected replacement C tu Total cost of expected replacement per unit time EA Evolutionary algorithm MTTF Mean time to failure MWD Measurement while drilling N Natural numbers ROP Rate of penetration R tu Probability of a predicted replacement S p Mean of the unshaded area t e Expected length of a bit usage t f Failure time t p Predicted length of a bit usage
Since 2012, low commodity prices have forced many mining companies to suspend or cease operations. To remain in business, some mine managers are exploring strategies to reduce operational costs. Given its importance as a cost element, increasing bench drilling efficiency and performance in open-pit mines has the potential to generate considerable savings. Efficiency and performance gains can be realized by monitoring the drilling operation, analyzing monitoring data with statistical tools and optimizing operational variables. Finding the best configuration of controllable drilling parameters would help to increase penetration rate and optimize drill bit replacement time so that fewer drill bits are consumed. In this paper, the optimal replacement time of a tricone drill bit is formulated as a cost minimization problem and solved by a genetic algorithm (GA). To demonstrate the proposed approach, the effects of controllable variables on drilling performance are experimentally quantified by statistical methods and used for optimization. Results show that the proposed approach can be used to determine the optimal replacement time for drill bits in open-pit mines.
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