ETree Module

For evaluating risks using Event trees

ETree is used to model a safety system (set of safety barriers) as an event tree. It produces simple models suited to all domains (aeronautics, automobile, rail, oil & gas, etc.) and is an easy way to obtain risk matrices. The ETree module uses ALBIZIA, the BDD (Binary Decision Diagram) computation engine developed by TotalEnergies. ALBIZIA offers the advantage of running accurate analytical computations and providing extensive information on the system under study.

Modeling and computations

Users can easily create event trees via an intuitive graphical interface in which barriers can be added after an initiating event (gas leak, supply loss, overflow, etc.). Each scenario (called a sequence) is therefore defined by a succession of barrier failures and successes. Each sequence has a consequence chosen in a list created by the user. A risk is defined for each consequence, and can then be positioned on the X-axis in the risk matrix. Then the software calculates the frequency of the consequence and assigns it to the Y-axis.

The frequency of initiating events and probability of failure of safety barriers can either be constant, follow a probability law (Exponential, Weibull, Periodic-Test….) or be defined by another type of model: fault tree, reliability block diagram or safety instrumented loops via the Boolean module.

Event Tree example

Specificities and strengths

Multiple risks :


Several risk matrices – human, financial or environmental for example – can be defined. For each one, the user can determine criticality levels: moderate, serious, major, etc.

A risk is entered in each matrix for each consequence in order to effectively indicate that a consequence is catastrophic in human terms but moderate in financial terms, or vice-versa

  • Templates: Do you regularly carry out studies using the same safety barriers? With GRIF ETree you can construct templates with a certain number of pre-configured barriers and risk matrices. If you want to create a new event tree, all you have to do is open the template and enter the parameters/coefficients.

Calculating the frequency of each consequence over time

Risk matrices display an average frequency. But when the initiating event or the barriers are no longer constant laws, it is sometimes necessary to display the frequency variation of a sequence (scenario) or of a consequence over time.

Data exploitation and results

  • Synthesis of input data in the form of tables that makes it easier to control the quality of an entry.
  • Possibility of automating calculations (batch run).
  • Results stored in the same document and exportable in different formats (csv, XML, Excel, etc.).
  • Visualization of results as curves, pie charts or histograms.
  • Vector printing of graphic elements and curves in PDF format which maintains optimum quality, even in A3 or A2 format.
  • Interaction with the operating system: option to copy/paste curves or results to word processing software, spreadsheets or presentation tools.
  • Possible connection to MySQL, Access and Excel databases to import the values to be used for the settings

Boolean package

The ETree module is part of the GRIF-Workshop Boolean package. All the Event-Trees made with this module can be used in Bool module which gathers all functionalities of Boolean modules. It is possible, in the same document, to make calculations using Event Trees (ETree), Fault Trees (Tree), Reliability Block Diagrams (BFiab) and Safety Instrumented Systems (SIL) together

GRaphical Interface for reliability Forecasting