DUNNETT, S. and ANDREWS, J.D., 2003. Analysis of fault trees with secondary failures. IN: Proceedings of the 15th Advances in Reliability Technology Symposium (ARTS) , Loughborough, UK, 2003, pp. 159-178.
The Fault Tree methodology is appropriate when the component level failures (basic
events) occur independently. One situation where the conditions of independence are
not met occurs when secondary failure events appear in the fault tree structure.
Guidelines for fault tree construction, which have been utilised for many years,
encourage the inclusion of secondary failures along with primary failures and
command faults in the representation of the failure logic. The resulting fault tree is an
accurate representation of the logic but may produce inaccurate quantitative results
for the probability and frequency of system failure if methodologies are used which
reply on independence.
This paper illustrates how inaccurate these quantitative results can be. Alternative
approaches are developed by which fault trees of this type of structure can be