Simulation and calculation of reliability performance and maintenance costs

This paper provides a short description of an extensive method for simulation and calculation of reliability, availability and maintenance costs of a product (system, function, equipment, mechanism, part, etc). The key elements are the following. (a) A quite general stochastic logic generalizes the usual FTA concept. A failure of the TOP-entity (product in use) is the logical-stochastic short-time consequence of changes in the state of the basic entities. (b) A simple model for deterministic relations between the TOP and the basic entities is introduced. This leads to the existence of two additional intermediate "wait states". (c) The long-time statistical behavior of each basic entity is modeled with the repair time distribution and a generalized non-homogenous Poisson failure process. (About 20 models to fit different kind of data are available.) (d) A stochastic simulation along the time axis produces a logbook of all events in chronological order. The effect of age and corrective maintenance (CM) on reliability is also taken into account. (e) Many examples exist for how the detailed data in the logbook can be used for calculation of figures, graphs, tables, etc. (f) Our method contains a model for the effect of changes of scheduled preventative maintenance (PM) procedures on failure tendency, but this paper considers PM only concerning cost and staff assessment.