Fault Tree Analysis
A fault tree analysis (FTA) is a systematic, deductive methodology for defining a single, specific undesirable event and determining all possible reasons that lead to the event. The undesired event is the top even in the fault tree diagram and generally represents a safety-related failure. However, any event can be analyzed with a fault tree. Fault tree analysis focuses on a subset of all possible system failures. Contrast with the FMEA, which analyzes all possible failure modes regardless of severity.
When properly applied, a FTA is extremely useful during the initial product design phases as an evaluation tool for driving preliminary design modifications. After product release, the FTA can be used as a troubleshooting tool. Through an FTA, a product can be evaluated from both a reliability and a fault probability perspective. From a reliability perspective, the FTA can estimate whether or not a product will meet performance reliability requirements. Using probabilistic evaluation, the FTA emphasis shifts in the likelihood of the occurrence of the undesired event.
The results of a FTA may be expressed qualitatively (minimum cut-sets, qualitative importance measures, and common cause potentials) or quantitatively (numeric probabilities of events, quantitative importance measures, and sensitivity evaluations).
- Functional analysis of highly complex systems.
- Allows observation of combined effects of simultaneous, non-critical events on top event.
- Deductive analysis.
- Graphical analysis.
- Can consider human error as a cause of the top event.
- Can consider software failures as causes of the top event.
- Can be either qualitative or quantitative.
- Evaluation of safety requirements.
- Evaluation of system reliability.
- Evaluation of human interfaces.
- Evaluation of software interfaces.
- Identification of potential design defects and safety hazards.
- Evaluation of potential corrective actions.
- Simplifying maintenance and troubleshooting.
- Logical elimination of causes for an observed failure.