Failure Mode and Effects Analysis

How to Use an FMEA

Jun 4, 2009 Martin Bell

Failure Mode and Effects Analysis is a widely used process to anticipate problems, rank them, and take action to prevent, or at least mitigate the effects of the worst.

Failure Mode and Effects Analysis (FMEA) is used widely in industries all over the world. It is particularly useful in a manufacturing environment. Standard practices or new and untried processes are assessed to anticipate what might go wrong, with a view to preventing and mitigating those that are most harmful.

History of FMEA

FMEA was first used by the US Military in the late 1940's, and was adapted by NASA for the Apollo space missions. The standard template form used by many companies for FMEA was first used by Ford Motor Company in the 1970's.

Failure Mode and Effects Analysis Procedure

Potential problems ("Failure Modes") are generated by all of those present, who meet together and "brainstorm" ideas on how a component (or process) can go wrong. The key points for the success of this stage is that participants turn up to the meeting well prepared, and that all ideas are recorded, without discussion. Each failure mode is then assessed for Severity, Occurrence, and Detection on a scale of typically one to ten.

FMEA: Severity

For each failure mode, a rank is given between 1 and 10. There are no absolute measures, and the numbers will mean different things in different industries. For example, in customer service, 1 might represent an informal complaint from a customer, and 10 could represent a loss of business. For NASA, 1 could mean slight sound problems, and 10 could mean a catastrophic failure.

Failure Mode and Effects Analysis: Occurrence

This number indicates how likely it is that the failure mode will happen. As for Severity, there is no absolute value, and what really matters is that there is consistency in scoring each failure mode. The least likely failure modes are represented by 1, and the extremely likely events are scored as a 10.

FMEA: Detection

This number is a measure of how likely it is that the failure mode can be found quickly. The highest score of 10 is set aside for failure modes that will not be found quickly, if at all, before they cause problems.

Failure Mode and Effects Aanalysis: Risk Priority Number

The Severity, Occurrence, and Detection numbers for each failure mode are multiplied together to generate a summary number called a Risk Priority Number, or RPN. The larger the RPN is, then the more urgent it is to eliminate or mitigate the failure mode. Each organisation usually has a threshold RPN, and any failure mode with an RPN above that threshold is assigned a person or team to work on it.

FMEA: Actions

The columns after the RPN number on the FMEA are used to define what needs to be done, who needs to do it, and when. The document is then used to drive the actions that reduce the impact of potential problems. An estimate is also made of the new Severity, Occurrence, and Detection numbers, when the actions are completed, and the new RPN is also calculated.

Failure Mode and Effects Analysis Summary

Failure Mode and Effects Analysis is a useful tool to highlight what problems might happen and what the effects of the problems are. The most serious problems are highlighted, and actions assigned to eliminate and mitigate their effects. The process has been used by the US Military, NASA, and a large and growing number of manufacturing and service companies.

The copyright of the article Failure Mode and Effects Analysis in Business Management is owned by Martin Bell. Permission to republish Failure Mode and Effects Analysis in print or online must be granted by the author in writing.

NASA Used FMEA To Plan The Lunar Landings

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