FMEA (Failure Mode and Effects Analysis) and FMECA (Failure Modes, Effects and Criticality Analysis) are methodologies used to identify potential failures, assess risk, and prioritize corrective actions. They involve identifying items, functions, failures, effects, causes, controls, and recommended actions. Risk is evaluated using Risk Priority Numbers for FMEA or a Criticality Analysis for FMECA. The results are used to improve design, increase reliability, and reduce costs.

1. FMEA and FMECA Failure Mode and Effects Analysis (FMEA) and Failure Modes, Effects and Criticality Analysis (FMECA) are methodologies designed to identify potential failure modes for a product or process, to assess the risk associated with those failure modes, to rank the issues in terms of importance and to identify and carry out corrective actions to address the most serious concerns. source : http:// www.weibull.com / basics / fmea.htm

2. FMEA / FMECA Overview Basic information: Item(s) Function(s) Failure(s) Effect(s) of Failure Cause(s) of Failure Current Control(s) Recommended Action(s) Plus other relevant details Methods to assess risk: Risk Priority Numbers (RPNs) Criticality Analysis (FMEA with Criticality Analysis = FMECA)

3. Published Standards and Guidelines Some examples: SAE J1739 AIAG FMEA-3 MIL-STD-1629A DNV-RP-A203

4. Figure 1: Process FMEA (PFMEA) in the Automotive Industry Action Group (AIAG) FMEA-3 format.

5. Basic Analysis Procedure for FMEA or FMECA Basic steps include: Assemble the team. Establish the ground rules. Gather and review relevant information. Identify the item(s) or process(es) to be analyzed. Identify the function(s), failure(s), effect(s), cause(s) and control(s) for each item or process to be analyzed. Evaluate the risk associated with the issues identified by the analysis. Prioritize and assign corrective actions. Perform corrective actions and re-evaluate risk. Distribute, review and update the analysis, as appropriate.

6. Risk Evaluation Methods Two most common methods are: Risk Priority Numbers (RPNs), which is associated with FMEA Criticality Analysis, which is associated with FMECA Quantitative Qualitative Severity Occurrences Risk

7. Risk Priority Numbers The analysis team must: Rate the severity of each effect of failure. Rate the likelihood of occurrence for each cause of failure. Rate the likelihood of prior detection for each cause of failure (i.e. the likelihood of detecting the problem before it reaches the end user or customer). Calculate the RPN by obtaining the product of the three ratings: RPN = Severity x Occurrence x Detection

8. Criticality Analysis: Quantitative The analysis team must: Define the reliability/unreliability for each item, at a given operating time. Identify the portion of the item’s unreliability that can be attributed to each potential failure mode. Rate the probability of loss (or severity) that will result from each failure mode that may occur. Calculate the criticality for each potential failure mode by obtaining the product of the three factors: Mode Criticality = Item Unreliability x Mode Ratio of Unreliability x Probability of Loss Calculate the criticality for each item by obtaining the sum of the criticalities for each failure mode that has been identified for the item. Item Criticality = SUM of Mode Criticalities

9. Criticality Analysis: Qualitative The analysis team must: Rate the severity of the potential effects of failure. Rate the likelihood of occurrence for each potential failure mode. Compare failure modes via a Criticality Matrix , which identifies severity on the horizontal axis and occurrence on the vertical axis.

10. Applications Used to: Establish and optimize maintenance and control plans Establish knowledge base of failure mode and corrective action information Comply with safety and quality requirements (ISO 9001 etc.)

11. Benefits Contribute to: Improved design Higher reliability. Better quality Increased safety Enhanced customer satisfaction Reduced costs

12. Summary System Sub-system Item/component Funtion Failure Effect Cause Action

13. Summary FMEA System Sub-system Item/component Funtion Failure Effect Severity Cause Occurrence/detection Action

14. Summary FMECA Quantitative System Sub-system Item/component Reliability Funtion Failure Criticality Analysis Factors Effect Cause Action