Modelling and simulation of repairable mechanical systems reliability and availability

Abstract

Markov approach is applicable for reliability and availability modelling when time to failure and repair follow an exponential distribution. Since failure time of mechanical components follows Weibull distribution, Markov approach cannot be employed to these systems. In present work, Semi-Markov model, which is appropriate for repairable mechanical systems, is considered. In structural dependency, once a unit of a repairable system is failed due to one or more of its constituent components, the entire unit is taken for repair. Therefore, the repairs are considered at the unit level. This feature of structural dependency in the proposed approach addresses the problem of larger state space. The states at the unit level are derived from the component states to develop the system model. The solutions for reliability and availability are obtained using the Monte Carlo simulation. The suggested approach is realistic than the existing software's such as Rapid Algorithmic Prototyping Tool for Ordered Reasoning, Blocksim, etc., as failures and repairs are considered at different hierarchical levels. The recommended approach is illustrated for a centrifugal pumping system.