Failure Modes and Effects Analysis (FMEA)

Failure modes and effects analysis (FMEA) is a tool used for identifying all possible failures in a
* design,
* manufacturing or assembly process,
* product or
* service.
It follows a step-by-step approach to detect possible failure modes and based on its priority, corrective actions are applied.

“Failure modes” denotes the ways in which something might fail. Any potential or actual errors or defects that can affect the customer are termed failures. The consequences of those failures are studied and described under “Effects analysis”.

Once the failures are identified they are prioritized according to the seriousness of their consequences are, their frequency and the ease of their detection. The FMEA aims to take actions to eliminate or reduce failures, based on their priority.

The steps involved in the FMEA process are:
1. The scope of the FMEA is identified. The scope can be a design, process or service.
2. Identify key functions of the scope.
3. List potential failure modes of each of the function. (How can this function go wrong)
4. Identify the effects for each failure mode. (How will this failure affect the manufacturer, customer..)
5. Rate the severity(S) of each effect on a scale of 1 to 10, 10 being most severe.
6. Identify the causes of all the failure modes. (Why does the function go wrong)
7. Rate the causes for each failure mode in terms of occurrence (O), 10 denoting the most frequent cause.
8. Identify the controls in the scope to detect the cause.
9. Rate the controls on the basis of detectability (D), 10 denoting extremely weak or no control.
10 Calculate Risk Priority Number (RPN). This is done by multiplying the ranks of severity, occurrence and detection (S*O*D). If, we had a severity of 10 (very severe), occurrence of 10 (happens all the time), and detection of 10 (cannot detect it) our RPN is 1000. This is a serious issue with great priority.
11. Identify the most critical issues by sorting the RPNs.
12. Assign corrective actions and deadlines.
13. Perform corrective actions and re-score the S, O and D numbers as applicable and calculate new RPNs.

A sample FMEA template can be seen in the figure above. It is a template specific for process FMEA as seen in http://lssacademy.com/2007/06/28/10-steps-to-creating-a-fmea