Sparing analysis-a multi-use planning tool

The applicability of the author's PC based sparing model to a typical supply system is shown with emphasis on the analysis as a tool for planning warranty costs, maintenance, the number of service personnel and level of training requirements, factory/repair facility workloads, and capital investment. This additional information is valuable in the R&M (reliability and maintainability) and logistics areas and is available early on in the development process. The model, which is based on a modified Poisson probability distribution, computes the number of initial spares required in inventory to assure at a preselected probability (confidence level) that a spare is available. It takes into account the number of units in service, failure rate for each replaceable unit, average turnaround time for repair or time to secure a replacement unit, confidence level selected for having a spare available, the support period, operational time, duty cycle, and whether units are screened before being returned for repair. The model is applicable to simple systems or to complex, multilevel systems and works equally well for repairable or discardable parts.<
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