CRITICALITY | Introduction | Types | Qualitative Analysis | Quantitative Analysis

CRITICALITY is a measure of the frequency of occurrence of an effect.

– May be based on qualitative judgement or

– May be based on failure rate data (most common)

01-static criticality experiment facility-uranium enriched solution

Qualitative analysis:

–Used when specific part or item failure rates are not available.

Quantitative analysis:

–Used when sufficient failure rate data is available to calculate criticality numbers.

01-qualitative vs quantitative analysis-part-item failure rates-calculate criticality number

Qualitative Approach:

  • Because failure rate data is not available, failure mode ratios and failure mode probability are not used.
  • The probability of occurrence of each failure is grouped into discrete levels that establish the qualitative failure probability level for each entry based on the judgment of the analyst.
  • The failure mode probability levels of occurrence are:

–Level A – Frequent

–Level B – Reasonably Probable

–Level C – Occasional

–Level D – Remote

–Level E – Extremely Unlikely

Quantitative Approach

Read More Info Regarding This Post :   Terms in Engineering Measurements

Failure Mode Criticality (CM) is the portion of the criticality number for an item, due to one of its failure modes, which results in a particular severity classification (e.g. results in an end effect with severity I, II, etc…).

  • Category I – Catastrophic: A failure which may cause death or weapon system loss (i.e., aircraft, tank, missile, ship, etc…)
  • Category II – Critical: A failure which may cause severe injury, major property damage, or major system damage which will result in mission loss.
  • Category III – Marginal: A failure which may cause minor injury, minor property damage, or minor system damage which will result in delay or loss of availability or mission degradation.
  • Category IV – Minor: A failure not serious enough to cause injury, property damage or system damage, but which will result in unscheduled maintenance or repair.
Read More Info Regarding This Post :   Errors | Errors in Measurement | Absolute Error | Relative Error | Causes Of Calibration

The quantitative approach uses the following formula for Failure Mode Criticality:

Cm = βαλpt

Where

Cm = Failure Mode Criticality

β = Conditional probability of occurrence of next higher failure effect

α = Failure mode ratio

λp = Part failure rate

T = Duration of applicable mission phase

01-criticality analysis-example-Plutonium criticality cell pit removal

Sending
User Review
( votes)

Leave a Reply

Your email address will not be published. Required fields are marked *