Definition
Fault Tree Analysis builds a top-down logic diagram starting from a specific undesired top event (such as a system failure or safety incident) and maps every combination of contributing basic events, connected through and/or logic gates, that could lead to it. It is suited to failures with multiple, potentially combined contributing factors, unlike the linear chain of the 5 Whys.
Key facts
- Top-down: starts from a specific undesired event and works backward through logic gates to contributing causes.
- Uses AND/OR logic to show whether multiple factors must combine, or any one alone is sufficient, to cause the top event.
- Suited to complex or safety-critical failures with multiple potential contributing paths, unlike the single-chain 5 Whys.
- Can support quantitative analysis if basic-event probabilities are known, estimating the top event's overall probability.
What does Fault Tree Analysis reveal about failures?
Fault Tree Analysis starts by defining the specific top event to be analyzed, then works backward, identifying the immediate contributing events and connecting them through AND gates (all must occur) or OR gates (any one is sufficient), continuing down to basic, no-further-breakdown events.
How do teams use Fault Tree Analysis in failure analysis?
The 5 Whys follows a single linear chain of causation, suited to straightforward problems. Fault Tree Analysis instead maps a branching structure of multiple possible contributing paths and their logical combinations, suited to complex or safety-critical failures. Root cause analysis is the broader discipline both techniques serve.
FAQ
Frequently asked questions
How are combinations of causes represented in a fault tree?
Fault Tree Analysis represents them as a top-down logic diagram, connecting contributing events to a specific top event through AND/OR gates that show whether multiple factors must combine or any single one is sufficient to cause it.
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