Titel_SS06

industries including the aerospace industry, the nuclear industry, the electronics industry and
the manufacturing industries.

In FMEA the engineering system or activity is broken down into components and sub-
systems, which are considered and assessed individually for the purpose of identifying the:

 Sub-systems and components, which are necessary for the system or activity to fulfil its
function.

 Failure modes for the identified sub-systems and components.

 Possible causes of failures for the identified failure modes.

 Relevant measures for predicting, detecting and correcting failures of the identified failure
modes.

 Effect of the identified failure modes for the identified sub-systems and components on
other sub-systems and components as well as the system.

The FMEA is an inductive approach as it starts from the failure events and attempts to
identify the causes. Furthermore as it considers one sub-system or component at the time the
FMEA approach may fail to identify combinations of failures of components and sub-systems,
which could be more critical than the individual sub-systems and components seen isolated.
The FMEA approach has proven to be a useful tool for the identification of potential hazards
through a large number of practical applications.

Failure Modes Effect and Criticality Analysis - FMECA

The FMECA is merely an extension of the FMEA where in addition to the FMEA also the
consequences of the failure events corresponding to the different failure modes are assessed.
Both the probability of failure and the consequences of failure are assessed subjectively for
the identified failure events and the considered failure modes for all identified sub-systems
and components. On this basis FMECA tables are produced whereby the severity of failure,
for the different sub-systems and components, may be documented see Table 4.1:

Probability

Consequences Very low Low Medium High

Minor

Significant X

Critical

Catastrophic

Table 4.1: FMECA table for a considered component and failure mode.

The results of the FMECA facilitate a ranking of the different modes of failure for the
constituents of the considered system but it should be emphasised that the result is not of an
absolute character.