Table 3 Ranking criteria of the detectability

1 ~ 2

The failure can be determined by phenomenon or visual inspection

3 ~ 4

The operator can simply judge the failure mode

5 ~ 6

Engineers can mostly detect failure modes with the help of professional tools

7 ~ 8

A variety of methods and tools are needed to detect the failure mode

9 ~ 10

Known detection methods are insufficient to detect the failure mode