Fault Tree Analysis


Fault tree diagrams represent the logical relationship between sub-system and component failures and how they combine to cause system failures.

Fault Tree+ has the ability to cover the hazard and safety aspects, historical data analysis, state dependency of the components through the inclusion of Fault Tree, Event Tree, Weibull analysis, and Markov analysis.

Key Features

Isograph has built its reputation on the efficiency, accuracy, stability and ruggedness of its Fault Tree+ product.

The Reliability Workbench Fault Tree+ (and FMECA) modules have been tested and certified by SGS-TÜV as suitable for safety analyses according to ISO 26262.

  • Range of event failure and repair models
  • Failure models range from fixed rates, dormant, sequential, standby, time at risk, binomial, Poisson and initiator failure models.
  • Basic events may be linked to Markov models created in the Markov analysis module.
  • CCF analysis using the beta factor, MGL, alpha factor or beta BFR methods.
  • Initiator-enabler analysis for sequence dependent analyses.
  • Sensitivity analysis allowing the automatic variation of event failure and repair data between specified limits.
  • Time dependent analysis providing intermediate values for time dependent system parameters.
  • Fault tree house event analysis. Full minimal cut set analysis (including success states if required)
  • Post-processing facilities for accurate upper bound calculations. Importance analysis.
  • Risk measures provided for event tree consequences.
  • Uncertainty analyses allowing confidence levels to be determined from event failure and repair data uncertainties.


  • Fault Tree+ Module able to build the large fault trees close to real world scenario.
  • Fault tree module is associated with event tree, Markov analysis, Weibull analysis in order to evaluate the hazardous events in every respect.
  • It provides CCF analysis, importance analysis, and uncertainty analysis and sensitivity analysis facilities.
  • It uses efficient minimal cut set generation algorithms to analyze large and complex fault and event trees.
  • NOT logic may be included in the fault and event trees at any level and event success states retained in the analysis results as an option.
  • The comprehensive reporting facilities are also included, allowing the user to report on their results using sophisticated text, graph and diagram reports.