Application of the cause-consequence diagram method to static systems

In the last 30 years various mathematical models have been used to identify the effect of component failures on the performance of a system. The most frequently used technique for system reliability assessment is Fault Tree Analysis (FTA) and a large proportion of its popularity can be attributed to the fact that it provides a very good documentation of the way that the system failure logic was developed. Exact quantification of the fault tree, however, can be problematic for very large systems and in such situations approximations can be used. Alternatively an exact result can be obtained via the conversion of the fault tree into a binary decision diagram. The binary decision diagram, however, loses all failure logic documentation during the conversion process. This paper outlines the use of the Cause-Consequence Diagram method as a tool for system risk and reliability analysis. As with the fault tree analysis method, the Cause-Consequence Diagram documents the failure logic of the system. In addition to this the Cause-Consequence Diagram produces the exact failure probability in a very efficient calculation procedure. The Cause-Consequence Diagram technique has been applied to a static system and shown to yield the same result as those produced by the solution of the equivalent fault tree and binary decision diagram. On the basis of this, general rules have been devised for the correct construction of the Cause-Consequence Diagram given a static system. The use of the cause-consequence method in this manner has significant implications in terms of efficiency of the reliability analysis and can be shown to have benefits for static systems.