FMEA – Probability of Occurrence

Probability of Failure Occurrence

The definition varies for different types of FMEA analysis. Therefore, you need to specify the type of the analytical process (for individual failures or for properties).

The overview below is based on standards for the automotive industry. Before use, ensure it is relevant for your case!

DFMEA

1. Level 1: Any design failure removed by standard QA procedures
2. Level 2: Developed according to known standards and tested
3. Level 3: Only minor design changes, in accordance with development standards
4. Level 4: Minor operational cycle changes, errors detected by preventive measures
5. Level 5: Design change, development uses known technologies and materials
6. Level 6: Lifecycle changes that may bring unexpected problems
7. Level 7: New design solution where preventive measures may not reveal issues
8. Level 8: First use of innovations where known preventive measures do not uncover issues
9. Level 9: New technologies and processes with no experience in the team or company
10. Level 10: New technologies/processes with no general experience

PFMEA

1. Level 1: Risk eliminated by QA, defects eliminated by physical protection
2. Level 2: ≤ 0.001 out of thousand (6σ) failures, highly effective control using proven techniques
3. Level 3: 0.01 out of thousand failures, highly effective control using proven techniques
4. Level 4: Low occurrence; technical or behavioral controls that effectively detect defects
5. Level 5: Medium occurrence; technical or behavioral controls that effectively detect defects
6. Level 6: High frequency of occurrence; technical or behavioral controls partially preventing defects
7. Level 7: Greater frequency of occurrence; technical or behavioral controls partially preventing defects
8. Level 8: High frequency of occurrence; behavioral controls with low certainty of preventing defects
9. Level 9: Very high frequency of occurrence; behavioral controls with low certainty of preventing defects
10. Level 10: Extremely high frequency; control is not possible or defect prevention is unachievable

FMEA-MSR

1. Level 1: Failure cannot occur during its lifetime. Justification is documented
2. Level 2: Assumed but not proven that the product will not fail during operation, or the product will not reach operational status
3. Level 3: Isolated failure cases may occur; assumption of at least 1 occurrence
4. Level 4: Assumed at least 10 occurrences
5. Level 5: Occasionally fails during its lifetime
6. Level 6: Fails relatively more often
7. Level 7: Commonly fails
8. Level 8: Frequently fails during its lifetime
9. Level 9: Likely to fail
10. Level 10: Unknown how often failure occurs, or it is unacceptably frequent during operation

Useful Links

• Detection Rating according to FMEA
• Severity Rating according to FMEA
• About FMEA in general