RPNs and Related Metrics

XFMEA and RCM++ make it easy to calculate and display a variety of metrics based on the Severity, Occurrence and Detection ratings that have been assigned for effects and causes in the FMEA:

• Risk Priority Number (RPN) is the product of severity x occurrence x detection.
• SxO is the product of severity x occurrence.
• SOD and SD combine the ratings into a 3 or 2 digit number. For example, if the severity is 7, the occurrence is 5 and the detection is 6, then SOD = 756 and SD = 76. When the issues are sorted in descending order, they will be prioritized first by severity, then by occurrence and then by detection.
• Quantitative Consequence Priority Number (QCPN) is based on quantitative values associated with each rating in the severity, occurrence and detection rating scales. If you use actual dollar amounts for severity, the QCPN metric will reflect the total expected cost for each issue.

The severity and occurrence scales can also be applied to items in the system hierarchy to provide a quick estimate of the "Item Risk."

The following topics discuss how to:

• Configure a project to use RPNs and related metrics
• Display RPNs and related metrics in the FMEA, queries, reports and plots
• Use more complex Risk Ranking logic for priority highlights and the risk matrix
• Calculate and display the Item Risk in the system hierarchy
• Use the Risk Matrix for either failure causes or items
• Use the Quantitative Consequence Priority Number (QCPN)