Step 7 Review Criticality and Present Failure Risk (Civil)

When both the Consequence and Probability/Likelihood of Failure has been determined for the Component-DM, you can review the Criticality.

Methodology

Criticality and Failure Risk for Age-Related Failures

The Criticality is the base risk of the Component or asset for Age-Related failures and it is a combination of the consequence of failure and the susceptibility to aging. This base risk is time independent, as the consequence and susceptibility normally remain constant over the lifetime of an asset. When determining the criticality, it is assumed that the asset will not be inspected nor maintained anymore, as of the last inspection date.

However, the likelihood of failure increases over time for AR DMs since the damage progresses and hence the probability that failure occurs increases. For this reason, Remnant Life (RL) (Step 6) and the Confidence thereof (Step 8) must also be considered.Likelihood of failure increases over time for Age-Related DMs. A matrix (see below) has been developed to express this time-dependency. This matrix can be used to facilitate a likelihood estimation (lowest likelihood rating = A). From this, the Risk for Age-Related failures can be calculated (and compared / combined with Non-Age-Related failures).Likelihood Matrix - to calculate Risk Likelihood class for AR FMs.

Failure Risk for Non-Age-Related Failures

Failure risk is a combination of consequence of failure and likelihood of failure.

In assessing the probability to failure, the entire failure scenario shall be taken into account and not only a portion of it.

The risk matrix distinguishes four risk levels. R1 denotes Low, R2 denotes Medium, R3 denotes High and R4 denotes Very High. Management should decide for each asset whether the risk is as low as practicable (ALARP).

In cases where a combination exists between Age-Related and incident related failure the resultant probability will be characterized as a Non-Age-Related failure (see example in Appendix B.8). It is these assets, depending on the failure consequence, for which a PM task will result in a reduction in the risk of failure. In other cases of Non-Age-Related failure, a risk that is ALARP will result in a managed run-to-failure approach, while one that is not ALARP will result in an administrative or redesign project that reduces the likelihood or severity of the failure scenario or removes the risk altogether.

Software

Review Criticality and Failure Risk for Age-Related Failures

To review Criticality and Failure Risk for Age-Related Failures:

• Select the Component – AR DM combination that you want to review.
• Select the Criticality Assessment tab to review the Criticality rating.

Select the Criticality Assessment tab to review Criticality for AR DMs. 

• Select the Risk tab to review the associated Risk rating (w-IMS automatically calculates the Likelihood for this matrix from the RL).

Review Failure Risk for Non-Age-Related Failures

To review Failure Risk for Non-Age-Related Failures:

• Select the Component – NAR DM combination that you want to review.
• Select the Risk tab to review the Risk rating.

Select the Risk tab to review the Risk.