Failure Mode and Effects Analysis (FMEA)

A Failure Modes and Effects Analysis (FMEA) tabulates failure modes of equipment and their effects on a system or plant. The failure mode describes how equipment fails (open, closed, on, off, leaks, etc.). The effect of the failure mode is determined by the system’s response to the equipment failure. An FMEA identifies single failure modes that either directly result in or contribute significantly to an incident. Human operator errors are usually not examined directly in an FMEA; however, the effects of inadequate design, improper installation, lack of maintenance, or improper operation are usually manifested as an equipment failure mode. Failure Modes and Effects Analysis evaluates how equipment can fail (or be improperly operated) and the effects these failures can have on a process. These failure descriptions provide analysts with a basis for determining where changes can be made to improve a system design.
Reference: CCPS: guidelines for hazard evaluation procedures, third edition
Qualitative hazard identification method based on the knowledge of each failure mode of the items of a plant.
Reference: Geoff Wells, 1996, HAZARD Identification and risk assessment.
FMEA is a technique, primarily 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 organized 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 occurrence and the severity of its consequences.
Reference: IEC 60300-3-9
Technical Tools/Hazards Identification/Scenario-Based Hazard Evaluation Procedures