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Fault Tree Analysis

Fault tree analysis techniques were first developed in the early 1960’s. Since this time they have been readily adopted by a wide range of engineering disciplines as one of the primary methods of performing reliability and safety analysis.

Fault trees graphically represent the interaction of failures and other events within a system. Basic events at the bottom of the fault tree are linked via logic symbols (known as gates) to one or more TOP events. These TOP events represent identified hazards or system failure modes for which predicted reliability or availability data is required. Typical TOP events might be:

• Total loss of production
• Safety system unavailable
• Explosion
• Loss of mission
• Toxic emission

Basic events at the bottom of the fault tree generally represent component and human faults for which statistical failure and repair data is available. Typical basic events are:

• Pump failure
• Temperature controller failure
• Switch fails closed
• Operator does not respond

Fault trees may be used to analyse large and complex systems. They are particularly adept at representing and analysing redundancy arrangements. In addition common cause events are easily handled.