Concurrent Importance and Sensitivity Analysis Applied to Multiple Fault Trees

Complex industrial systems may present different potentially dangerous failure states (Top-events). The analysis of system failure states via Fault-tree technique allows determining the failure frequency of potential accidents and the importance measures of components' failure modes. The combination of Importance and Sensitivity Analysis (ISA) constitutes a very powerful tool to improve the design of critical systems or to prove that the design satisfies safety requirements. The present reports describes a novel approach to implement Importance and Sensitivity analysis applied to Fault-trees, which consists of the concurrent analysis of all relevant system's Fault-trees to identify the weakest parts of the system which require further design improvement. This approach aims at overcoming the limitations of the current methods in application for ISA in which Top-events are sequentially analysed. In addition the proposed method extends the ISA application also to 'over-reliable' system functions (if any) on which the reliability/maintainability characteristics of the involved components can be relaxed with consequent cost saving. The result is a uniformly protected system satisfying the predefined design goals.JRC.G.7-Traceability and vulnerability assessmen