Modeling and analyzing the effects of periodic inspection on the performance of safety-critical systems

This paper presents a method for incorporating into Markov models of safety-critical systems, periodic inspections and repairs which occur deterministically in time. Both perfect and imperfect inspections and repairs can be modeled. Based on this new modeling technique, closed-form solutions are derived for a variety of important performance indexes including MTTF, MTTFD, MTTFs, average availability, and average probability of failing dangerously. The solutions are applied to an example system to illustrate how the method can be used to study the effects on performance of: a) choices of the time-length between periodic inspections and repairs, and, b) improvements in inspection and repair techniques.