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A fault tree diagram. Fault tree analysis (FTA) is a type of failure analysis in which an undesired state of a system is examined. This analysis method is mainly used in safety engineering and reliability engineering to understand how systems can fail, to identify the best ways to reduce risk and to determine (or get a feeling for) event rates of a safety accident or a particular system level ...
Build the event tree diagram; Obtain event failure probabilities: If the failure probability can not be obtained use fault tree analysis to calculate it. Identify the outcome risk: Calculate the overall probability of the event paths and determine the risk. Evaluate the outcome risk: Evaluate the risk of each path and determine its acceptability.
An RBD may be converted to a success tree or a fault tree depending on how the RBD is defined. A success tree may then be converted to a fault tree or vice versa by applying de Morgan's theorem . To evaluate an RBD, closed form solutions are available when blocks or components have statistical independence .
The exact calculation may not be easy in all cases, such as those where multiple scenarios (with multiple events) are possible and detectability / dormancy plays a crucial role (as for redundant systems). In that case fault tree analysis and/or event trees may be needed to determine exact probability and risk levels.
Reliability block diagrams or fault trees are usually constructed at the same time. These diagrams are used to trace information flow at different levels of system hierarchy, identify critical paths and interfaces, and identify the higher level effects of lower level failures.
[5] [8] The more complex risk analysis tools of fault tree analysis, event tree analysis use the same principle: Things go wrong, there is a reason for that and a result too, with the result generating the adverse consequences. The bow-tie diagram introduces the concept of a central energy-based event (the "bow tie knot") in which the damaging ...
An event tree may start from a specific initiator such as loss of critical supply, [6] or component failure. [7]Some industries use both fault trees and event trees. Software has been created for fault tree analysis and event tree analysis and is licensed for use at the world's nuclear power plants for Probabilistic Safety As
The PSSA may contain qualitative FTA, which can be used to identify systems requiring redundancy so that catastrophic events do not result from a single failure (or dual failure where one is latent). A fault tree is prepared for each SFHA hazard rated hazardous or catastrophic. Fault trees may be performed for major hazards if warranted.