Fault Tree Analysis
Fault tree analysis is a deductive method that starts with an unwanted event and maps the combinations of equipment, process, control, or human failures that could cause it.
What this term means in maintenance
Fault tree analysis is a deductive method that starts with an unwanted event and maps the combinations of equipment, process, control, or human failures that could cause it.
How fault tree analysis works
The analysis begins with a top event such as “cooling system unavailable.” The team works downward to identify the events that could produce it.
Logical gates show how causes combine:
- OR gate: any listed input event can cause the result
- AND gate: multiple input events must occur together
Practical example
A pumping system may be unavailable because the duty pump fails and the standby pump also fails to start. The standby may fail because of no power, a control fault, a closed valve, or mechanical seizure.
When to use fault tree analysis
Fault tree analysis is useful for:
- Complex systems
- Critical equipment failures
- Safety or environmental events
- Multiple protection layers
- Situations where several independent conditions may combine
Relationship to root cause analysis
Fault tree analysis can support root cause analysis by showing several possible cause paths rather than forcing the investigation into one linear chain.
Common mistake
The tree should be based on the real equipment design, control logic, operating state, and evidence. A visually complex diagram is not automatically a useful investigation.
Related concepts
Related maintenance terms
Keep exploring connected CMMS, reliability, and maintenance planning terms.
Root Cause Analysis
Root cause analysis is a structured investigation used to identify the underlying conditions that allowed a failure or problem to occur and determine actions that reduce recurrence.
Failure Mode and Effects Analysis
Failure Mode and Effects Analysis, or FMEA, is a structured method for identifying how an asset or process may fail, the effects of each failure, existing controls, and actions needed to reduce risk.
5 Whys Analysis
The 5 Whys is a simple root cause analysis technique that repeatedly asks why a problem occurred until the team reaches an evidence-supported and actionable underlying cause.
Glossary FAQs
- What is the top event in a fault tree?
The top event is the unwanted system condition or failure being analyzed.
- What is the difference between an AND gate and an OR gate?
An AND gate requires multiple input events together. An OR gate means any listed input event can produce the result.
- Is fault tree analysis only used for safety engineering?
No. It can also support maintenance, reliability, production, quality, and process investigations.