Transient failure behaviour of repairable systems

Theoretical models are presented to study the transient failure behaviour of repairable systems under four different maintenance strategies: breakdown maintenance, minimal repair, block replacement, and age replacement. The main feature of the approach is that the usual steady-state assumption-which is deemed to be unrealistic for technical installations-is avoided. Specific attention is given to the number of (planned and unplanned) repairs and replacements that occur during a specified period of time. The study described in this paper has been performed as part of a project on maintenance manning assessment in the oil industry. The results obtained are of direct use for the analysis of maintenance workload, the centre of attention in the project.