- Quality Tools
This standard addresses two approaches to FTA. One is a qualitative approach, where the probability of events and their contributing factors, - input events - or their frequency of occurrence is not addressed. This approach is a detailed analysis of events/faults and is known as a qualitative or traditional FTA. It is largely used in nuclear industry applications and many other instances where the potential causes or faults are sought out, without interest in their likelihood of occurrence. At times, some events in the traditional FTA are investigated quantitatively, but these calculations are disassociated with any overall reliability concepts, in which case, no attempt to calculate overall reliability using FTA is made.
The second approach, adopted by many industries, is largely quantitative, where a detailed FTA models an entire product, process or system, and the vast majority of the basic events, whether faults or events, has a probability of occurrence determined by analysis or test. In this case, the final result is the probability of occurrence of a top event representing reliability or probability of fault or a failure.