Rank failure modes by RPN.
Use it before launching or changing a process. Score each failure mode for severity, occurrence and detection, and it ranks them by risk priority number so you know what to fix first.
Paste eight columns from Excel. 10 is worst for severity and occurrence. For detection, 10 means the failure is hardest to detect.
RPN = severity × occurrence × detection, from 1 to 1,000. Work the highest RPN first, and treat any severity of 9 or 10 as a priority whatever the RPN.
Failure Mode and Effects Analysis (FMEA) identifies how a process or product could fail, how bad that would be, and what controls are in place.
A missing O-ring in a valve assembly has severity 8 (leak at customer), occurrence 4 and detection 6 (visual check only): RPN 192. Adding a fixture that will not close without the O-ring drops detection to 2 and the RPN to 64.
Risk Priority Number, the product of severity, occurrence and detection ratings. It ranks risks from 1 to 1,000.
PFMEA looks at how a manufacturing or service process can fail. DFMEA looks at how a product design can fail.
The AIAG-VDA FMEA handbook introduced Action Priority (high, medium, low) as an alternative to RPN. Many companies still use RPN for simple FMEAs.