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About the Tree module

Benefits of the Tree module, the Fault Tree analysis tool


and ergonomic


Efficient and accurate
calculations (ALBIZIA)


Complies with 
IEC 61508 and IEC 61511

  • With the intuitive graphical interface of GRIF Tree module - Fault Tree Analysis software, it’s easy to create fault trees and enter gates (AND, OR, K/N, NOT, XOR, NAND, NOR, IF, THEN, ELSE) according to the logic of the system being studied, as well as more than 20 probability distributions: Exponential, Weibull, Gamma Lambda Mu, Exponential Periodically Tested, Weibull Periodically Tested, and so on.
  • If a probability distribution is unavailable, you can provide your own probability distribution using either a value table or a Markov graph. Once the tree has been created, Common Cause Failures can easily be identified using different CCF models (Beta Factor, MGL, Shock models).
  • With the “Attribute” feature (system with custom properties), you can add any information you wish to each object of the document, either to provide a more precise description or for traceability purposes.


The ALBIZIA engine, developed by TotalEnergies, produces a wide range of results for analytical calculations:

  • Unavailability: Q(t), U(t) or PFD(t), Availability: A(t), Reliability: R(t), Unreliability: F(t);
  • Frequency: W(t), UFI(t) or PFH(t); and Failure rate: λeq(t), λv(t) or CFI(t);
  • Usual mean values: MTTF, MTBF, MUT, MDT, number of failures;
  • Minimal cut sets (probability and frequency of cut sets);
  • Reliability allocation;
  • Many importance factors (Birnbaum MIF, Critical CIF, Vesely, DIF, etc.) that help users identify and correct system weaknesses.

Calculating the time spent in the SIL zones: in addition to the calculations defined above, ALBIZIA is the only engine that can calculate how long the PFD(t), PFH(t) or EqLambda(t) of a system spends in the various intervals during its operational life.

The figure below shows a mean availability of 8.44E-3, which corresponds to SIL2. However, it also indicates the percentage of time the system spent in each SIL over its 30 years’ operation. In this case, it spent 39.77% of the time in SIL1.


User-friendly design:

  • Groups/sub-trees are easy to create and with the automatic layout feature, users can effortlessly organize their tree simply by pressing the F7 key.
  • With the sub-tree templates, it’s easy to build trees for systems that use known equipment.
  • In addition to the editing window for each object, GRIF produces data tables that make it easier to control the quality of input data and modify information (find/replace, suffixes, prefixes).
  • • GRIF features plug-ins for entering input data, either based on internal feedback from the field, standards or commercial sources. Having accurate input data saves time for users.

Propagation of uncertainty: To simulate real-life conditions as closely as possible, parameter-related uncertainties can be factored in. For example, you can specify whether a failure rate follows a Uniform, Normal or Log-Normal distribution. A Monte-Carlo simulation is performed in addition to the BDD calculation to obtain mean values. Finally, a quantile calculation is performed to provide a confidence interval for each result. It can be an interval of 60, 70, 80, 85, 90, 95 or 99% (centered or not).

N.B. it is a requirement with the IEC standard 61511. 


  • Option to automate calculations (batch runs) and draw variations for sensitivity analysis.
  • Results are stored in the document and can be exported in a variety of formats (csv, XML, Excel, etc.).
  • Results can be viewed as line graphs, pie charts or histograms.
  • Printing in PDF vector format produces high-quality images and the files are small enough to be sent by email, even if the document contains hundreds of pages.
  • External files (PDF certificates, system images, etc.) can be added to the document and incorporated into the full report.
  • Interaction with the operating system: option to copy/paste either to or from word processing software, spreadsheets, or presentation tools.
Sectors of activity: aeronautics, aerospace, energies, defense, telecoms, transportation, health, universities and research

GRIF is designed for any field of activity

Whether for an oil platform, aircraft, train or water supply system, GRIF evaluates the reliability and availability of any system using a range of computational techniques. The GRIF software suite offers a wide variety of calculation methods so that users can select the most appropriate (analytical, simulation, etc.), according to the system being modeled.

Need more information? 

The Tree module is part of the Boolean package of the GRIF Software suite 

About GRIF