Managing availability improvement efforts with importance measures and optimization

The effective performance of repairable systems is critical to the success of all organizations, and availability measures are one of the two most common sets of measures used in evaluating the performance of such equipment. When availability performance is inadequate, engineers need a methodology for prioritizing availability improvement efforts. These efforts could include actions that reduce the occurrence of system failures, improve the execution of equipment maintenance, and/or add redundancy to the system. We define a set of availability importance measures and apply these measures to a general class of two-state repairable systems. Analysis of these measures for five examples yields insight into the prioritization of availability improvement efforts. In general, we show that focusing on reducing the occurrence of system failures provides greater benefit than increasing the speed of equipment repair. Then, we formulate a set of three optimization models that capture the trade-offs between improving availability performance and the investments required to achieve this improvement. Two of these models address the allocation of funds for availability improvement efforts, and the third model addresses the incorporation of availability performance considerations in the system design phase.