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

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

PFMEA

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

FMEA-MSR

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