Importance Measures in Reliability Engineering: An Introductory Overview

In many industries, system reliability needs assuring at the design stage and improving at the operation stage. To these aims, many methods have been developed. One of these is reliability importance measures. This chapter provides an introduction to several important measures that can be useful for analysis of the reliability and the operation of systems. Established importance measures reflect aspects of the relation between component failure and the functioning of the system. They are typically suggested as simple management tools, for example to rank the criticality of components at specific moments of the system operation. While they are attractive due to their simplicity, there are risks when aiming to communicate complex situations through a single number. A few recent developments are also mentioned, in particular the inclusion of costs of system operation in importance measures and the move away from importance of individual components to groups of components of the same type, which may simplify system management for large systems with relatively few types of components.