New Developments of the Digraph-Based Techniques for Fault-Tree Synthesis

By making use of steady-state analysis of the fault propagation behaviors in process systems, improvements of the digraph-based techniques for faultrtree synthesis have been achieved. In particular, generalized sub-tree structures have been developed for variables associated with nodes on feedforward and feedback loops and a preliminary loop-searching computer algorithm has been worked out. These techniques are integrated in a fault-tree construction procedure which is also presented in this paper. This revised procedure has been implemented in a number of application examples. The results show that the proposed approach is not only feasible but also capable of identifying correct causes of the top event which are missing in the fault trees obtained by the conventional operators.