Fault Tree Analysis for System Safety

Fault tree analysis (FTA) is a deductive analysis technique that focuses a particular undesirable event and is used to determine the root causes contributing to then occurrence of the undesirable event. Construction and analysis of fault trees involves nine steps. This fault tree construction process is replicated from the top level, through all the intermediate levels, until the analyst reaches the basic causes associated with the undesirable event. After the fault tree is constructed, it must be solved. A major product of FTA is the determination of cut sets. For the cut set method of probability calculation, once the minimal cut sets are obtained, if desired, the analyst can perform quantitative analysis of the fault tree by evaluating probabilities. The quantitative evaluations are most easily performed in a sequential manner by first determining the component failure probabilities, then determining the minimal cut set probabilities, and finally determining the probability of the top event.