ABSTRACT
In case of determining the PFD only the dangerous failures (λDU and λDD) have to be considered.
– All failure rates are assumed to be constant. – Considering multi-channel structures it is assumed,
that there is a certain proportion (β) of failures, affecting all components/channels at the same time, thus in case of occurrence of this failure redundancy is invalid. These are so called common cause failures (CCF) which are quantified by means of the β-factor.
