FAILURE MODE AND EFFECTS ANALYSIS

'Failure Mode and Effects Analysis (FMEA)' is a risk assessment technique for systematically identifying potential failures in a system or a process. It is widely used in the manufacturing industries in various phases of the product life cycle. ''Failure modes'' means the ways, or modes, in which something might fail. Failures are any errors or defects, especially ones that affect the customer, and can be potential or actual. ''Effects analysis'' refers to studying the consequences of those failures.
In FMEA, Failures are prioritized according to how serious their consequences are, how frequently they occur and how easily they can be detected. An FMEA also documents current knowledge and actions about the risks of failures, for use in continuous improvement. FMEA is used during the design stage with an aim to avoid future failures. Later it’s used for process control, before and during ongoing operation of the process. Ideally, FMEA begins during the earliest conceptual stages of design and continues throughout the life of the product or service.
The purpose of the FMEA is to take actions to eliminate or reduce failures, starting with the highest-priority ones. It may be used to evaluate risk management priorities for mitigating known threat-vulnerabilities. FMEA helps select remedial actions that reduce cumulative impacts of life-cycle consequences (risks) from a systems failure (fault).
It is used in many formal quality systems such as QS-9000 or ISO/TS 16949. The basic process is to take a description of the parts of a system, and list the consequences if each part fails. In most formal systems, the consequences are then evaluated by three criteria and associated risk indices:

★ Severity (S),

★ Likelihood of occurrence (O), and (Note: This is also often known as probability (P))

★ Inability of controls to detect it (D)
An FMEA simple scheme would be to have three indices ranging from 1 (lowest risk) to 10 (highest risk). The overall risk of each failure would then be called ''Risk Priority Number (RPN)'' and the product of Severity (S), Occurrence (O), and Detection (D) rankings: RPN = S × O × D. The RPN (ranging from 1 to 1000) is used to prioritize all potential failures to decide upon actions leading to reduce the risk, usually by reducing likelihood of occurrence and improving controls for detecting the failure.

Contents

Disadvantages

History

See also

References

Disadvantages

If used as a top-down tool, FMEA may only identify major failure modes in a system. Fault tree analysis (FTA) is better suited for "top-down" analysis. When used as a "bottom-up" tool FMEA can augment or complement FTA and identify many more causes and failure modes resulting in top-level symtoms. It is not able to discover complex failure modes involving multiple failures within a subsystem, or to report expected failure intervals of particular failure modes up to the upper level subsystem or system.[citation needed]

History

The FMEA process was originally developed by the US military in 1949 to classify failures "according to their impact on mission success and personnel/equipment safety". FMEA has since been used on the 1960s Apollo space missions. In the 1980s it was used by the Ford Motor Company to reduce risks after one model of car, the Pinto, suffered a design flaw that failed to prevent the fuel tank from rupturing in a crash, leading to the possibility of the vehicle catching on fire.^[1]

See also

★ Causal layered analysis

★ Futures techniques

★ Failure mode

★ Failure rate

★ FMECA

★ Process decision program chart

★ Reliability engineering

★ Risk assessment

★ Safety engineering

★ Six sigma

★ DRBFM

★ Microsoft Excel 2000 FMEA Worksheet template: http://en.wikipedia.org/wiki/Image:FMEA_Worksheet.xls

References

1. Quality Associate Institute's History of FMEA


★ http://www.asq.org/learn-about-quality/process-analysis-tools/overview/fmea.html