Systematic Anticipation and Validation of Scenarios of Failure Propagation and Mitigation

Abstract. In this paper we present a new method for safety analysis of complex hierarchical designs. The method helps analysts to identify potential functional failures of the system at the application level and then to systematically determine the causes of those failures in progressively lower levels of the design. The method can ensure the consistency of the results from the safety studies of the system that are performed at various levels of the design decomposition. The method, though, cannot ensure that the assumptions about the behaviour of the system that underlie those studies are correct. Our second aim in this paper is, precisely, to show an approach to validating those assumptions using system modelling and simulation. Here, we present a tool that we have developed and which enables testing of anticipated scenarios of failure and recovery in PLC controlled processes. Finally, we discuss the application of our approach on a case study that we performed on a simulated emergency fuel supply system. We present fragments from the safety analyses that we have derived for this system and discuss some of the simulation experiments.