Title: Bayesian networks and probability boxes to model uncertainty in unavailability assessment

Authors: Walid Mechri; Wassim Snene; Kamel Ben Othman

Addresses: Research Laboratory LARA Automatic, National Engineering School of Tunis, University of Tunis El Manar, LR-11-ES18, Le Belvédère 1002 Tunis, Tunisia ' Research Laboratory ATSI, National Engineering School of Monastir, University of Monastir, 2 Rue Ibn El Jazzar, 5019 Monastir, Tunisia ' Research Laboratory ATSI, National Engineering School of Monastir, University of Monastir, 2 Rue Ibn El Jazzar, 5019 Monastir, Tunisia

Abstract: In this paper the problem of uncertainty in assessing unavailability of Safety Instrumented Systems (SIS) is treated. The characteristic parameters of the SIS including Common Cause Failure (CCF) factors are replaced by probability densities families (p-boxes) allowing reliability experts to express their uncertainty on the statement of values probabilities. We show how the imprecision is modelled and propagated in a Bayesian networks which induces uncertainty about the failure probability on demand of the SIS and its Safety Integrity Level (SIL). We will demonstrate how the uncertainty in the values of some characteristic parameters causes significant variations in the level risk.

Keywords: safety systems; probability of failure on demand; uncertainty; Bayesian networks; common cause failure; p-boxes.

DOI: 10.1504/IJRS.2018.094940

International Journal of Reliability and Safety, 2018 Vol.12 No.3, pp.261 - 278

Accepted: 01 Jun 2018
Published online: 24 Sep 2018 *

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