Risk Evaluation Methods
A typical FMEA incorporates some technique to evaluate the risk linked with the potential problems recognized through the analysis. There are two most common methods. These are risk priority numbers and criticality analysis and are described in the paragraphs to follow.
Risk Priority Numbers
This is a numerical & relative "measure of overall risk" equivalent to a particular failure mechanism and is calculated by multiplying the severity, occurrence & detection numbers. To utilize the Risk Priority Number (RPN) method to assess risk, the analysis team must be following:
- 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 (that means the likelihood of detecting the problem before it attain the end user or customer), and
- Calculate the RPN by attaining the product of the three ratings : RPN = Severity × Occurrence × Detection = SOD
The RPN can then be utilized to compare issues within the analysis and to prioritize problems for corrective action.