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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 ...
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. When statistical independence is not satisfied, specific formalisms and solution tools such as dynamic RBD have to be considered. [4]
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.
A fault tree diagram. Fault trees are a logical inverse of success trees, and may be obtained by applying de Morgan's theorem to success trees (which are directly related to reliability block diagrams). FTA may be qualitative or quantitative. When failure and event probabilities are unknown, qualitative fault trees may be analyzed for minimal ...
A design failure modes and effects analysis, DFMEA, is a structured qualitative analysis of a system, subsystem, device design to identify potential failure modes and their effects on correct operation. The concept and practice of performing a DFMEA, has been around in some form since the 1960s.
This might include, for example: Standardized mission profile with specific fixed duration mission phases; Sources for failure rate and failure mode data; Fault detection coverage that system built-in test will realize; Whether the analysis will be functional or piece-part; Criteria to be considered (mission abort, safety, maintenance, etc.)
The last 160 pages give an example of the process in action. Some of the methods covered: Functional Hazard Assessment (FHA) Preliminary System Safety Assessment (PSSA) System Safety Assessment (SSA) Fault Tree Analysis (FTA) Failure Mode and Effects Analysis (FMEA) Failure Modes and Effects Summary (FMES) Common Cause Analysis (CCA ...
Layers of protection analysis (LOPA) is a technique for evaluating the hazards, risks and layers of protection associated with a system, such as a chemical process plant. . In terms of complexity and rigour LOPA lies between qualitative techniques such as hazard and operability studies (HAZOP) and quantitative techniques such as fault trees and event trees.