Criticality Analysis

Written by Nicholas Kamuda
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Criticality analysis is central to many forms of modern maintenance engineering. Its use in modern maintenance was promulgated by the U.S. military in 1949 in the report Procedures for Performing a Failure Mode, Effects, and Criticality Analysis. Since then, it has been developed by businesses and large-scale operations, and is used in maintenance strategies such as RCM, RCA, and others.

The basic idea behind criticality analysis is to rank the importance of failure modes and frequency for physical assets such as machinery and equipment. The actual importance of the analysis, however, may be dependent on how the failure modes are ranked. In the military report, the ranking was assigned to failure modes on the basis of their effect on other personnel and equipment.

Criticality Analysis in RCM

The idea of ranking the importance of failure modes on how they affect the larger system of assets is central to business applications of criticality analysis. Under RCM practices, criticality is assigned through FMEAs (Failure Mode & Effects Analyses) based on the consequences of the failure, not the failure itself. For example, the consequence of a failure that will in turn cause other failures is more important than a failure that will simply slow production.

Though this may seem like a simple idea, it is the heart of a rigorous practice involving what may seem like large amounts of time and resources. Simple preventive or corrective maintenance is not enough to cope with the increasing complexity of physical assets, however. In the long run, stronger, more modern maintenance strategies can keep all aspects of business up to or exceeding expectations, not only the mechanical processes.

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