Systems Availability Modeling, Considering Complex and Imperfect Sparing

The importance of realistic systems availability (readiness) models for useful systems and cost effectiveness analysis and evaluation is discussed. A method is presented which considers: 1. Different types of imperfect failure detection. 2. Various replacement strategies, with imperfect replacements and limited spares. 3. Different types of scheduled inspections. 4. Non-instantaneous replacement rates and some types of non-instantaneous failure detection. By a careful consideration of the physics of the system and some redefinition, irreducible and ergodic transition matrices are derived from apparently nonirreducible system state transition matrices. This results in the development of a method that not only includes the non-ideal system constraints listed above, but gives additional system analysis capability. In many applications this modeling procedure may well supplant costly simulation studies and increase the knowledge about how the various system parameters interact. Optimization procedures can also be readily applied to the resulting steady-state availability models. This is followed by the addition of a section of comments which indicate some additional applications and some inherent advantages of the methods presented. Finally, a set of conclusions is presented.