5.7 Criticality Analysis Over Time

The condition of the assets will change over time affecting the probability of failure. Costs of repair may increase, the community may grow, new roads may be built, rehabilitation may be completed or similar factors may occur that cause the consequence of failure to change. Therefore, it is necessary to periodically review the criticality analysis and make adjustments to account for changes in the probability of failure and the consequence of failure.

The criticality analysis must be reviewed and updated periodically to ensure that the utility is spending its time and resources on the appropriate assets. This operational and managerial approach is the heart of Asset Management. Ways to implement this approach are discussed in the next chapter. The update must also incorporate replacement of assets. If an asset that was critical primarily due to its probability of failure is replaced with a new asset, the criticality number will go down since the probability of failure is much less. The update must also take into account any changes in redundancy - positive or negative. If a new asset was installed to create redundancy, the consequence ranking will go down. If a redundant asset has failed and has not been repaired or replaced, the redundancy has decreased and the consequence ranking of the asset may increase.

You do your interventions and your asset replacements based on your ability to live with the risk. --Ross Waugh, New Zealand

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