Isograph Home | FaultTree+ | Download Our Software | Contact Us

Fault Tree Analysis Diagram

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.


Isograph's FaultTree+ computer program allows you to perform fault tree analysis in an integrated environment. The program also provides event tree and Markov analysis capabilities. For more information on FaultTree+ visit our web site at


Useful Links

Contact Us

USA and Canada

Tel: 801 610 0041
Fax: 801 610 0050

Rest of the World

Sales: +44 1925 43 7001
Support: +44 1925 43 7002
Fax: +44 1925 437010