The ranking scales (for severity, occurrence, and detection) are mission critical for the success of an FMEA.
- They establish the basis for determining the risk of one failure mode and effect relative to another.
- The same ranking scales for FMEAs should be used consistently throughout your organization. This will make it possible to compare the RPNs from different FMEAs to one another.
Ranking scales need to be customized so that they are relevant to your organization.
- Your products and processes will be reflected in customized ranking scales.
- Not only are customized ranking scales easier for FMEA Team members to relate to and use, but they make the ranking and ultimately the RPN more meaningful.
- If your organization does both DFMEAs and PFMEAs, there should be a customized ranking scale for each type of FMEA.
The best way to customize a ranking scale is to start with a standard, generic scale and then modify it to be more meaningful to your organization.
- As you add examples specific to your organization, consider adding several columns with each column focused on a topic.
- One topic could provide descriptions of severity levels for operational failures, another column for customer satisfaction failures, and a third for environmental, health, and safety issues.