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FMEA Risk Priority Ranking Reference
The following tables are used by permission in iGrafx for FMEA.
Occurrence Rankings
iGrafx uses the Automotive Industry Action Group (AIAG) Occurrence Rankings in the following table to calculate the possible failure rates in the FMEA, based on number of errors and number of samples. For example, if you set Sample to 20 and a cause has 1 error in the Cause and Effect window, the ranking is calculated to 7.
|
AIAG Occurrence Rankings for FMEA |
||
|---|---|---|
|
Probability of Failure |
Possible Failure Rates |
Ranking |
|
Very High: Failure is almost inevitable |
1 in 2 |
10 |
|
1 in 3 |
9 |
|
|
High: Repeated failures |
1 in 8 |
8 |
|
1 in 20 |
7 |
|
|
Moderate: Occasional failures |
1 in 80 |
6 |
|
1 in 400 |
5 |
|
|
1 in 2,000 |
4 |
|
|
Low: Relatively few failures |
1 in 15,000 |
3 |
|
1 in 150,000 |
2 |
|
|
Remote: Failure is unlikely |
1 in 1,500,000 |
1 |
Severity Rankings
Use the rankings in the following table to rate Severity in the FMEA. These numbers are entered manually.
|
AIAG Severity Rankings for FMEA |
||
|---|---|---|
|
Effect |
Severity of Effect |
Ranking |
|
Hazardous without warning |
When a failure mode affects safe device operation without warning |
10 |
|
Hazardous with warning |
With a failure mode affects safe device operation with warning |
9 |
|
Very high |
Device inoperable: Loss of primary function |
8 |
|
High |
Device operable: At a highly reduced level of performance |
7 |
|
Moderate |
Device operable: At a reduced level of performance |
6 |
|
Low |
Device operable: At a slightly reduced level of performance |
5 |
|
Very low |
Device operable: Defect noticed by most customers |
4 |
|
Minor |
Device operable: Defect noticed by average customer |
3 |
|
Very minor |
Device operable: Defect noticed by discriminating customers |
2 |
|
None |
Almost no effect |
1 |
Detection Rankings
Use the rankings in the following table to indicate Detection Rankings in the FMEA. These numbers are entered manually.
|
AIAG Detection Rankings for FMEA |
|
|---|---|
|
Detection Difficulty |
Ranking |
|
Can be detected as error occurs or immediately following error, no permanent damage |
1-2 |
|
Can be detected during assembly: Early or with high certainty |
3-4 |
|
Can be detected during assembly: Late or with low certainty |
5-6 |
|
Can be detected during service or routine maintenance |
7-8 |
|
Very unlikely to be detected during ownership |
9-10 |
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