If required, and cost, time and resources permit, the FMEA can be extended to
include a criticality analysis. In a criticality analysis, the reliability block
diagrams are analysed and each block assigned a failure rate, λ, in failures per
million hours. From this, a reliability figure for the overall system can be
determined, which will indicate how often the system will fail completely.
Adding to each block an inverse repair rate, TR, in hours-to-repair, which will
indicate how long it will take to recover the intact system after repair, can
further extend the analysis.