Hamid Jahanian

Hamid Jahanian, Annabelle McIver

Safety Instrumented Systems (SIS) protect major hazard facilities, e.g. power plants, against catastrophic accidents. An SIS consists of hardware components and a controller software -- the ``program''. Current safety analyses of SIS' include the construction of a fault tree, summarising potential faults of the components and how they can arise within an SIS. The exercise of identifying faults typically relies on the experience of the safety engineer. Unfortunately the program part is often too complicated to be analysed in such a ``by hand" manner and so the impact it has on the resulting safety analysis is not accurately captured. In this paper we demonstrate how a formal model for faults and failure modes can be used to analyse the impact of an SIS program. We outline the underlying concepts of \emph{Failure Mode Reasoning} and its application in safety analysis, and we illustrate the ideas on a practical example.

Hamid Jahanian, David Parker, Marc Zeller et al.

Failure Mode Reasoning (FMR) is a novel approach for analyzing failure in a Safety Instrumented System (SIS). The method uses an automatic analysis of an SIS program to calculate potential failures in parts of the SIS. In this paper we use a case study from the power industry to demonstrate how FMR can be utilized in conjunction with other model-based safety analysis methods, such as HiP-HOPS and CFT, in order to achieve a comprehensive safety analysis of SIS. In this case study, FMR covers the analysis of SIS inputs while HiP-HOPS/CFT models the faults of logic solver and final elements. The SIS program is analyzed by FMR and the results are exported to HiP-HOPS/CFT via automated interfaces. The final outcome is the collective list of SIS failure modes along with their reliability measures. We present and review the results from both qualitative and quantitative perspectives.