Glossary · Risk estimation methods
Fault Tree Analysis (FTA)
Also known as: FTA
German: Fehlerbaumanalyse (FTA)
In reliability and safety engineering, Fault Tree Analysis (FTA) is a deductive method that analyzes combinations of causes leading to a defined top event. It represents these combinations with logic gates such as AND and OR and can be evaluated qualitatively or quantitatively.
- Machine safety
- Risk assessment
In one sentence
Fault Tree Analysis (FTA) works top-down from an undesired event to the combinations of failures and errors that can cause it, including common causes.
Example
An FTA for “robot moves while a person is in the cell” traces the top event to combinations such as a failed door switch and a defeated interlock, or a software fault and a failed safe torque off.
How it applies
- Risk analysis: Choose a clear top event, usually a hazardous event, and decompose it into intermediate and basic events. Minimal cut sets show the smallest combinations that cause the top event.
- Functional safety: FTA shows whether redundancy really removes single points of failure and reveals shared causes that defeat it. With failure data, it can support probability estimates for a safety function.
- Integrated systems: FTA handles combinations of hardware faults, software faults, human errors and external conditions, which makes it useful at the interfaces of integrated lines.
- Technical documentation: Document the top event, assumptions, boundaries and data sources. Link basic events to the components and to the FMEA where they are analyzed.
FTA vs. FMEA
FTA starts with one undesired outcome and asks what can cause it. FMEA starts with each component and asks what its failure can cause. FTA handles combinations of events better; FMEA gives broader coverage of single failures.