Rigorous functional model for mine production equipment maintenance and reliability

Reliability of mine production equipment is strategic to long-term objectives of profit maximization and cost minimization. For maximum equipment availability and utilization, a balance must be struck between production and preventive maintenance schedules. In practice, however, the drive to achieve production targets is sometimes given a higher priority leading to equipment breakdown and lower availabilities. Further, the use of production equipment after its economic life results in excessive breakdown maintenance costs which significantly reduce the profit margin of the operation. In this paper, the authors develop a rigorous functional economic model to examine the productivity and economics of production equipment in an open pit mining operation based on failure probability and the timing of scheduled maintenance, rebuild and replacement. The productivity function is derived from production parameters, operating and system efficiency, and operating schedules, The failure probability profiles with built-in preventive maintenance schedules are developed from the expected failure and repair intensities for various operating conditions. The productivity model under each failure probability profile is simulated in each economic phase. Analysis of the results shows that equipment rebuild must be incorporated in a comprehensive maintenance program to achieve higher availabilities and production and lower production cost, With rebuild, repair and replacement, availability and annual production are 30 and 40 percent higher, respectively, and unit cost is 96 percent lower. The probability of achieving a net gain of $20 million with rebuild and a net loss of $7 million without rebuild is 100 percent in each case.