Müller, J. R.; Ständer, T.; Schnieder, E.:
Improving System Safety Modelling in Accordance to IEC 61508 by using Monte Carlo Simulations.
Proceedings of the 2nd IFAC Workshop on Dependable Control of Discrete Systems (DCDS), S. 219-223, Bari, Italy, June 2009.
Abstract: According to IEC 61508 the assessment of the Safety Integrity Level for a safety related
system requires the calculation of the probability of failure on demand (PFD). Part 6 of IEC 61508
provides formulas for redundant and homogeneous systems. In contrast to this, industrial systems are
often designed heterogeneously, in order to reduce to probability of common cause failures. The paper
therefore provides a comparative examination of an analytical calculation, Markov- and Petri netsimulation
at a running example of a heterogeneous 1 out of 2 (1oo2)-structure. The comparison of the
derivative of the corresponding analytical formula and the model based approaches underline the need of
dependability engineers for more user-friendly, graphical and intuitive support.