Reliability of sequential systems using the cause-consequence diagram method

In many industrial systems, where safety is of the utmost importance, it is necessary that expedient tools for accident analysis are available and employed at the design stage. Such tools must be able to handle large systems in a systematic way and display the factors that are of vital importance for the functionality of the system. The technique of fault tree analysis is commonly used to assess the failure probability of such systems. The fault tree represents the failure logic of the system in an inverted tree structure and has the advantage that it provides very good documentation of the way the failure logic was developed. Conventional fault tree quantification requires a number of assumptions regarding the system. One of these is that the basic events in the tree occur independently. This condition is not satisfied when sequential failures are encountered. Employing alternative methods, such as Markov methods, can result in the loss of the documentation that represents the failure logic of the system.