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Failure mode and effect analysis (FMEA)
Qualitative hazard identification method based on the knowledge of each failure mode of the items of a plant.
FMEA is a technique, primarly qualitative although it can be quantified, by which the effect or consequences of individual component fault modes are systematically identified. It is an inductive technique which is based on the question "what happens if...?". The essential feature in any FMEA is the consideration of each major part/component of the system, how it becomes faulty (the fault mode), and what the effect of the fault mode on the system would be (the fault mode effect). Usually, the analysis is descriptive and is organised by creating a table or worksheet for the information. As such, FMEA clearly relates component fault modes, their causative factors and effects on the system, and presents them in an easily readable format.
FMEA is a "bottom-up" approach and considers consequences of component fault modes one at a time. As such, the method is tolerant of a slight amount of redundancy before becoming cumbersome to perform. Also, the results can be readily verified by another person familiar with the system.
The major disadvantages of the technique are the difficulty of dealing with redundancy and the incorporation of repair actions as well as the focus on single component failures.
An FMEA can be extended to perform what is called Failure Mode, Effects and Criticality Analysis (FMECA). In a FMECA, each fault mode identified is ranked according to the combined influence of its probability of occurence an the severity of its consequences.