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| FMEA
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| Introduction |
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Failure mode and effect analysis (FMEA) is a preventative method used to identify potential ways in which a product or process might not meet expectations. FMEA also aims to determine the effects of potential failures on the performance of the product/service or system. The process of ranking failure modes and causes may also be used to indicate where engineering effort should be concentrated to reduce failure occurrence. Classifying the results of an FMEA in order of seriousness determines how critical the potential problems are.
According to Muhleman et al (1988), the primary objective of an FMEA is to determine the features of a service or product design and production/operations, which are critical to the various modes of failure. FMEA is most suitably applied at the design stage of a product or service to identify and eliminate failure causes. The technique draws all essential experience and information from design, marketing, production, purchasing and distribution to pinpoint the critical nature of potential problems and suggest action, which will assist in their prevention.
According to Muhleman et al (1988) the core elements of FMEA are:
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| Element |
Failure mode
The anticipated conditions of operation are used as the background to study the most probable failure mode, location and mechanism of the product/system and its components.
Failure effect
The potential failures are studied to determine their probable effects on the whole product/service and the effects of the various components on each other.
Failure criticality
The potential failures in the various parts of the product or service system are examined to determine the severity of each failure effect in terms of lowering performance, safety hazard, total loss of function etc.
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| Important steps in an FMEA analysis |
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The steps which should be considered when analysing FMEA include;
Identify the components of the product or system.
Identify all possible failure modes of each component.
Detail all the effects that each potential failure mode would have on the overall
function of the product or system.
Identify all possible causes of each failure mode.
Assign numerical values to the failure modes on a scale of 1 to 10, (where 1 is low and 10 is high) for;
P = the probability of each failure mode occurring (1=low, 10=high).
S = seriousness or criticality of the failure.
D = difficulty of detecting the failure before the product is used by the
consumer.
These values may be represented in the form of a ratings table i.e.
Calculate the Criticality index, C { C = SxPxD } for each failure mode. This indicates the relative priority of each mode in the failure prevention activities and outline the corrective/preventative action required.
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| Further features of FMEA |
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It may be observed that the FMEA technique is similar to QFD in that FMEA is also based on the completion of charts or matrices to identify problems and suggest relevant remedies. As QFD and FMEA charts must continuously be developed and updated, they are known as “live documents”. The major benefits of FMEA include the identification of weak points in the component or process under investigation and documentation of expert knowledge including:
Recording component functions.
Outlining production processes.
Collecting knowledge on failurs.
Carrying out the FMEA requires the co-operation of an inter-disciplinary team, due to the inter-departmental nature of the problems being examined. This process enhances the development of teamwork and employee involvement in an organisation, in keeping with the concepts of World Class Manufacturing.
The economic viability of the analysis must also be considered. The upkeep of FMEA requires a lot of clerical work and so it may be necessary to develop computer programs for the production and presentation of FMEA documents.
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