Event tree

The event tree analysis (English Event Tree Analysis ) is an inductive method, to determine what the possible consequences of an error occurring. It is a kind of system analysis and described as a quality method in DIN 25419.

Method

In the event tree analysis is an event that can occur in a system, in the event tree as the start event (initial event) considered and investigated its potential impact on the overall system. In the event tree then the effects of the start event to the system are displayed ( the reactions of the system components to the event ) in the form of branches (function or failure) graphically ( binary tree ).

The event tree is usually drawn from left to right, each with branches for two alternatives. An upper branch for the successful conduct of the event and a lower branch for its failure. The individual paths from the start event to a defined final state represent the possible accident sequences

Each branch is associated with a certain failure probability of error. If there are no error probabilities for the empirical values ​​, these values ​​are calculated using the fault tree analysis.

By multiplying the probabilities of the start event and those of the branches that lie on the path, man gets the chance of this specific accident sequence.

The probability of an accident of the system is obtained - if there are no dependencies between the components of different paths exist - then by adding all the path - probability, which lead to an accident ( see example in ).

In the Probabilistic Safety Analysis ( PSA), the event tree analysis is used in conjunction with the fault tree analysis method (see Methods for description in PSA).

Disadvantages

As the number of branches doubled with each step, very large trees can arise in complex systems. The creation and analysis of such large trees is then only with the help of computer programs (see PSA).

Use

The event tree analysis can be used at the earliest useful if the system requirements are known. It is used mainly in Probabilistic Safety Assessments PSA.