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Mode and Effect Analysis (FMEA)
During the last decades, many FMEA types
have been established by
different sectors of industry. Some of them even have their own
specific name, for example:
FMEDA: D = Detectability
Design-FMEA, Process FMEA, Software
FMEA and so on (they simply
nature of the subject under consideration.
HAZOP: Hazard and Operability Analysis
HACCP: Hazard Analysis and Critical Control Point
The underlying principle is always
the same, and can be described as follows:
The way how potential failure modes
are identified as well as all
downstream FMEA steps depend on FMEA type and FMEA goal, and can
therefore be very different.
The following two examples may
outline the range of what is practically
encountered in the FMEA world:
the topic(s) / item(s) to be analysed (e.g. process, machine,
cold chain, etc.)
Identify potential failure modes.
- It is important not focusing
those failures that have already occurred, but rather on those which
are imaginable to occur.
While the first example is focused on
improvement, the second example
is a standard procedure in reliability and safety analysis.
Depending on the FMEA type, one or
more of the following topics will be
- A (moderated) group of 5 to 10
persons. The boundaries are
wide and there are almost no limits. Every idea is
appreciated as long as there is a relationship with the FMEA goal.
Unexpected or surprising thoughts should be even more appreciated. Such
FMEAs are rather rare, and the goal is often radical improvement of a
product or a process, rather than continual
- A single person performing a so
called piece part FMEA. Piece part
FMEAs work according to established procedures. Results are often
foreseeable and almost never surprising. The main goal is to calculate
and document failure rates of failure modes, and finally the
probabilities of undesired end effects.
The process of many FMEA types are
live processes, and therefore the
FMEA documents are live documents. This means that they are updated and
reviewed either on a regular basis, or on demand. Those FMEAs focused
on improvement are typical
live FMEAs: After each improvement/mitigation action, a re-assessment
is made until the results are conceived acceptable.
The basic toolset for FMEA is the
FMEA table, also called FMEA
worksheet. Specific column headers of the FMEA worksheet and its
tabular structure define FMEA type and FMEA methodology. In turn,
type of industry and applied FMEA standard can be easily concluded from
the column headers and the tabular structure of the FMEA worksheet.
The reader may now expect a list of
established FMEA standards; instead, by
describing just three FMEA types of only two FMEA standards
(Mil-STD-1629 and IEC 60812), the following paragraphs aim to outline
the entire FMEA spectrum.
On the next page, the "father" of all
today's FMEA Standards,
the so called "task 101" of Mil-Std-1629, also called "piece part FMEA"
will be described.
Mil-Std-1629 (Failure Mode and
Effect Analysis) has been developed by
the US department of defense as a requirement for army material
- Identify the potential causes of the failure modes
- Goal: Mitigation of failure causes
- Identify the consequences (effects) of the failure modes (on
local component level, and/or assembly level, and/or system level)
- Goal: Mitigation of failure effects
- Qualitative classification of failure mode probabilities (e.g. on
a scale from 1 to 10)
- Quantitative calculation of failure mode probabilities (e.g. in
units of failures per million hours)
- Qualitative or quantitative assessment of failure severities
- Qualitative or quantitative assessment of failure detection
- Identify and authorize corrective actions
- Due dates and responsibilities