A Static Analysis of Dynamic Fault Trees with Priority-AND Gates

A PAND gate is a special AND gate of Dynamic Fault Trees (DFTs) where the input events must occur in a specific order for the occurrence of its output event. We present a transformation from a PAND gate to an AND gate with some dependent conditioning events, called CAND gate, provided that the dynamic behavior of the system can be modeled by a (semi-)Markov process. With the transformation, a DFT with only static Boolean logic gates and PAND gates can be transformed into a static fault tree, which opens up the way to employ efficient combinatorial analysis for the DFT. In addition, the PAND gate cannot model the priority relations between the events whose occurrences are not necessary for the output event. The inability has not been addressed before and it can be overcome by the proposed CAND gate.