Criticality Analysis
The MIL-STD-1629A document explained two types of criticality analyses: quantitative and qualitative. In order to utilize the quantitative criticality analysis method, the analysis team must follow:
- Define the reliability/unreliability for each item, at a specified operating time,
- recognize the portion of the item's unreliability that can be attributed to each potential failure mode,
- Rate the probability of loss (or severity) that shall result from each failure mode that might occur, and
- Compute the criticality for each potential failure mode by attaining the product of the three factors:
Mode Criticality = Item Unreliability × Mode Ratio of Unreliability × Probability of Loss
- Estimate the criticality for each item by attaining the sum of the criticalities for each failure mode that has been recognized for the item.
Item Criticality = SUM of Mode Criticalities
In order to use the qualitative criticality analysis method to appraise risk & prioritise corrective actions, the analysis team must follow:
- Rate the severity of potential effects of failure,
- Rate the likelihood of occurrence for each potential failure mode, and
- Compare failure modes by means of a Criticality Matrix that identifies severity on the horizontal axis & occurrence on the vertical axis.
Critical Characteristics
A failure mode which might conceivably result in personal injury, loss of life or violate a government (that means, automobile emission norms) mandate is considered critical.
Such a failure mode shall be assigned a severity level value(s) of 6 or more irrespective of the level of occurrence or detection.
Significant Characteristics
A failure mode which is not deemed to be critical but needs stringent procedure control (that means, SPC, 100% inspection, etc.) to make sure product quality is considered significant.Such a failure mode will be assigned a severity level value(s) of 6 or more irrespective of the level of occurrence or detection.