Dealing adequately with technical uncertainties

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FMEA and FMECA with examples
  FMEA, Introduction
  Example 1: Mil-STD-1629 Piece Part FMEA
  Example 2: Mil-STD-1629 Criticality Analysis
  Example 3: Automotive FMEA
  General concerns with FMEA

FMEA means Failure Mode and Effect Analysis, whereas FMECA means Failure Mode and Effect Criticality Analysis, which is just a specific FMEA type.
During the last decades, many FMEA types have been established by different sectors of industry. Some of them even have their own specific names.

FMEDA: D = Detectability
Design-FMEA, Process FMEA
HAZOP: Hazard and Operability Analysis
HACCP: Hazard Analysis and Critical Control Point

Despite the variety of FMEA types, the underlying principle is always the same, and can be described as follows:

- Define the topic(s) / item(s) to be analysed (e.g. process, machine, cold chain, etc.)
- Identify potential failure modes. It is important not focusing on those failures that have already happened, but rather on those which are imaginable to happen.

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:

1. A (moderated) group of 5 to 10 persons. The boundaries are wide and there are only weak limits regarding thoughts. Every idea is appreciated as long as there is a relationship with the FMEA goal. Unexpected or surprising thoughts are even more appreciated. Goals of such FMEAs are very often rather radical solutions than continual improvement with small steps.

2. 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 the failure rates of the failure modes of the FMEA item.

While the first example is focused on improvement, the second example is rather used in reliability and safety analyses.
Depending on the FMEA type, one or more of the following topics will be addressed in the FMEA:

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 on a regular basis. 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 both 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 expect here a list of established FMEA standards; however, this is exactly what will not happen, because the core principles of all these FMEA standards are almost the same. By describing just three FMEA types of only two FMEA standards (Mil-STD-1629 and IEC 60812), the following three paragraphs will address all basic FMEA principles.

In practice there are also definitions like "Process FMEA", Design FMEA", " Software FMEA" and so on. These definitions however have no direct relationship with FMEA types, instead they only describe the nature of the topic subject to FMEA.

The following page shows the "father" of all today's FMEA Standards, the so called "task 101" of Mil-Std-1629, also called "component FMEA".
Mil-Std-1629 (Failure Mode and Effect Analysis) has been developed by US department of defense as a requirement for army material suppliers.


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