Modelling repairable system reliability with explanatory variables and repair and maintenance actions

A closer look has been taken into repair and maintenance actions (RMAs) that affect systems in an industrial environment. It has been discussed that the classical definition of ‘repair’ is complex. Virtually every RMA affects the system in some way. To model repairable systems, a concept is needed that reflects the state of the system incorporating the scale of RMAs. A few concepts and their possible incorporations are proposed. The repair and maintenance indicator type ‘a’ (RMIa) is introduced as the weighted accumulated operating time of all or the most important parts of the system. The indicator type ‘b’ (RMIb) is introduced as a state of a system depending on its age and RMA history. The indicator type ‘c’ is introduced to reflect the degree of repair of an RMA. These indicators can be useful for the modelling and comparison of repairable systems. Several methods to incorporate repair and maintenance indicators into intensity process models for repairable system reliability are discussed. The indicators may be used as covariates in a proportional intensity model (PIM), or as reduction factors in a virtual age process model.