Isolation failure rate (FR) is the number of occurrences of a failure mode over some time period that can be attributed to a specific part. The units are usually the number of detectable failures per either million hours (FPMH) or billion hours (FITs). The range is from 0 to 100. Isolation FR is calculated for parts and assemblies. You can insert Isolation Failure Rate in the FMEA Tree Items table. If this field is blank, a value of 100% is assumed.

The equation for calculating isolation FR is a summation across all modes of: