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Part Four
Improvement
Figure 19.7 Procedure for failure mode and effect analysis (FMEA)
Based on a quantitative evaluation of these three questions, a risk priority number (RPN)
is calculated for each potential cause of failure. Corrective actions, aimed at preventing
failure, are then applied to those causes whose RPN indicates that they warrant priority, see
Figure 19.7.
Worked example
Part of an FMEA exercise at a transportation company has identified three failure modes
associated with the failure of ‘goods arriving damaged’ at the point of delivery:
Goods not secured (failure mode 1)
Goods incorrectly secured (failure mode 2)
Goods incorrectly loaded (failure mode 3).
The improvement group which is investigating the failures allocates scores for the probability
of the failure mode occurring, the severity of each failure mode, and the likelihood
that they will be detected using the rating scales shown in Table 19.2, as follows:
Probability of occurrence
Failure mode 1 5
Failure mode 2 8
Failure mode 3 7
Severity of failure
Failure mode 1 6
Failure mode 2 4
Failure mode 3 4
Probability of detection
Failure mode 1 2
Failure mode 2 6
Failure mode 3 7
The RPN of each failure mode is calculated:
Failure mode 1 (goods not secured) 5 × 6 × 2 = 60
Failure mode 2 (goods incorrectly secured) 8 × 4 × 5 = 160
Failure mode 3 (goods incorrectly loaded) 7 × 4 × 7 = 196
Priority is therefore given to failure mode 3 (goods incorrectly loaded) when attempting
to eliminate the failure.