What is Failure mode, effects and criticality analysis (FMECA)

Failure mode, effects and criticality analysis (FMECA) is an extension of failure mode and effects analysis (FMEA).

FMEA is a bottom-up, inductive analytical method which may be performed at either the functional or piece-part level. FMECA extends FMEA by including a criticality analysis, which is used to chart the probability of failure modes against the severity of their consequences. The result highlights failure modes with relatively high probability and severity of consequences, allowing remedial effort to be directed where it will produce the greatest value. FMECA tends to be preferred over FMEA in space and North Atlantic Treaty Organization (NATO) military applications, while various forms of FMEA predominate in other industries.

FMECA analysis procedure

The FMECA analysis procedure typically consists of the following logical steps:

Define the system
Define ground rules and assumptions in order to help drive the design
Construct system block diagrams
Identify failure modes (piece-part level or functional)
Analyze failure effects/causes
Feed results back into design process
Classify the failure effects by severity
Perform criticality calculations
Rank failure mode criticality
Determine critical items
Feed results back into design process
Identify the means of failure detection, isolation and compensation
Perform maintainability analysis
Document the analysis, summarize uncorrectable design areas, identify special controls necessary to reduce failure risk
Make recommendations
Follow up on corrective action implementation/effectiveness

Failure effects analysis

Failure effects are determined and entered for each row of the FMECA matrix, considering the criteria identified in the ground rules. Effects are separately described for the local, next higher, and end (system) levels. System level effects may include:

System failure
Degraded operation
System status failure
No immediate effect

The failure effect categories used at various hierarchical levels are tailored by the analyst using engineering judgment.

FMECA report

A FMECA report consists of system description, ground rules and assumptions, conclusions and recommendations, corrective actions to be tracked, and the attached FMECA matrix which may be in spreadsheet, worksheet, or database form.