5.6 Failure Mode Effects And Criticality Analysis

Failure Mode Effects and Criticality Analysis (FMECA) is one of the effective reliability analysis methods. In this analysis, various failure modes of the individual component/subsystems are considered and their effect on the overall system performance. FMECA could be described as organization of knowledge about potential failures. This task is a design aid for assurance purposes. The analysis is often called bottom-up approach in contrast to the top-down approach of FTA. The results of FMECA serves as the main input to define Built in Tests (BIT) that can automatically detect and isolate system failures as they occur and increase system availability. FMECA also serves as a dictionary of failure modes for safety and logistics analysis. The use of FMECA is generally limited by the time and resources available and the capability to derive a sufficiently detailed database at the time of the analysis (for example, accurate system definition, the components present in the systern/subsystem, up-to-date drawings, failure rate and hazard rate and so on).

FMECA is helpful in studying the different modes of failure for a component and its effect on the overall system performance. The analysis comprises two parts namely quantitative and qualitative. The acronym FMECA can be split into two FMEA and CA:

• Failure Mode Effects Analysis (FMEA)

• Criticality Analysis (CA)

FMEA is a qualitative analysis of the failure modes whereas CA is a quantitative analysis. In criticality analysis each failure mode is quantified by assigning a criticality number which is a...