Failure Modes and Effects Analysis (Failure Modes, Effects and Criticality Analysis)

A failure modes and effects analysis (FMEA) is a forward logic (bottom-up), tabular technique that explores the ways or modes in which each system can fail and assesses the consequences of each of these failures [1]. In its practical application, its use is often guided by top-down 'screening' (as described in the 'Procedures' section) to establish the limit of the analytical resolution. A failure modes, effects, and criticality analysis (FMECA) also addresses the criticality or risk of individual failures. Countermeasrures can be defined for each failure mode, and consequent reductions in risk can be evaluated. FMEA and FMECA are useful tools for cost and benefit studies, to implement effective risk mitigation and countermeasures, and as precursors to a fault tree analysis (see Lesson VI).

Contemporary analysts are coming to recognize FMEA (and FMECA) as the technique of choice to identify potential single-point failures within a system. Applying FMEA to complex systems having redundancy-rich architecture fails to identify or evaluate probability or penalty for system 'crashes'. It cannot be relied on, therefore, to produce meaningful results in cost-benefit studies. Logic tree methods (fault tree analysis, event tree analysis, and cause consequence analysis) are now viewed as generally more useful for this purpose.