Page 528 - Corrosion Engineering Principles and Practice

494 C h a p t e r 1 2 C o r r o s i o n a s a R i s k 495

The method brings the focus of an analysis on consequences and
additional safeguards to mitigate the effects of the failure. It is a common
practice for individuals familiar with system functionality to perform
FMEA, but teams of experts can produce greater insight into the
mechanisms and wider range consequences. The analysis uses a form
that begins with a systematic list of all components in the system:

• Component name
• Function of component
• Possible failure modes
• Causes of failure
• How failures are detected
• Effects of failure on primary system function
• Effects of failure on other components
• Necessary preventative/repair action
• Rating of failure frequency
• Rating of severity (i.e., consequence) of failure
Failures are rated as critical if they have high frequency or severity
ratings. In these cases, special protection measures may be considered.
The strengths of FMECA are [10]

• It is widely used and well understood.
• It can be performed by a single analyst.
• It is systematic and comprehensive, and identifies hazards.
• It identifies safety-critical equipment where a single failure
would be critical for the system.
FMECA weaknesses are

• Its benefit depends on the experience of the analyst.
• It requires a hierarchical system drawing as the basis for the
analysis, which the analyst usually has to develop before
proceeding with the analysis.
• It is optimized for mechanical and electrical equipment, and
does not apply to procedures or process equipment.
• It copes with multiple failures and human errors with
difficulty.
• It does not produce a simple list of failure cases.

Most accidents have a significant human contribution, and
FMECA is not well suited to identifying these. As FMECA can be
conducted at various levels, it is important to decide before starting