Fault Tree Analysis (FTA)

Fault Tree Analysis is widely used for modeling and analyzing reliability of various systems. In critical application areas such as nuclear power plants, aerospace industry and military purposes FTA has been used for decades. Nowadays many kinds of devices and facilities contain more and more complex technology. Demand for good quality and minimizing risks concerning safety, environment and economy through the whole life cycle of a product sets high requirements for the methods used for controlling those aspects already in the design phase. FTA has shown its power in such use.

When constructed completely and correctly the fault tree is a model that can be used as a basis for qualitative and quantitative analysis. Qualitative analysis means finding the minimal cut sets for the so called top event. (A cut set is a combination of events that cause the top event to occur. A minimal cut set is a combination of events that looses its cut set property if any of its events is removed.)

Quantitative analysis reveals much more information of the system than just finding the minimal cut sets. By simulating the system (based on the fault tree logic and probabilities of the root causes) for say 50 years one gains a statistical failure history for that period of time. From this data it is possible to seek out some very valuable key values indicating for example the parts that could be improved most cost effectively to gain the best rise in overall system reliability.