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Inspection Replacement Policy
A form of asset replacement policy that may fall into the preventive replacement class but only if the inspection takes places before Functional Failure ("F") has occurred.

An asset is replaced only if it fails to meet the standards established by a Facility Condition Assessment (FCA).



Attributes
Listed below are some of the key attributes of the Inspection Replacement Policy (IRP):
  • Condition-Based Maintenance - IRP is founded on the principles of condition-based maintenance (CbM) which is not driven by rigid time schedules and 
  • Exposure-Based Strategies - IRP carries out inspections on variable intervals depending on the age and exposure conditions of the asset.
  • Operating Histories - IRP should be based on a complete operating history of measured condition observations to identify trends and patterns in the data.
  • Predictive Maintenance - The method relies upon predictive maintenance (PdM) technologies and continuous monitoring / commissioning approaches.
  • Systemic Failure - The approach seeks out systemic problems to determine replacement cycles whereas localized problems are dealt with on an ongoing basis to preserve the life of the asset.
  • Deterioration Models - Requires an understanding of deterioration models and late-life metrics of different assets. 
  • Leading Indicators - The approach relies upon suitably qualified persons to identify leading indicators of failure. 
  • Concealed Conditions - The inspections will sometimes need to reveal concealed conditions.
  • Effective Age - Determination of the effective age of the asset relative to its chronological age.
In order for IRP to succeed as a proactive approach, it requires some of the following:


Variations
Listed below are some of the key variants of the Inspection-Based Replacement Policy: There are some subtle, but important, distinctions between JIT, CbR and IbR.


Candidate Assets and Examples
Generally, this approach is best suited to assets that have the following attributes:
  • Asset that can be inspected, preferably through visual observations or limited destructive testing.
Listed below are some examples of an effective IRP approach to asset management:
  • We replaced our roof after the condition assessment identified blisters in the membrane, which were prevalent throughout and systemic.
  • We deferred the replacement of our roof after the inspection found that problems were localized to one area and could be addressed with localized repair

Evaluation:
Some of the merits of this approach are summarized below:
  • Empirical Data - The status of some systems and assets can sometimes only be determined only by physical inspection.
  • Maintenance Program Coordination - The inspections can form part of the condition-based maintenance program.
  • Damage Mitigation - Mitigation of potential collateral damage
  • Cost Efficiencies - Reduced costs due to formal tendering process well in advance of functional failure.
Some of the limitations of this approach are listed below:
  • Expensive - Inspection can be time consuming and costly when these are carried out over the life of the asset and at greater frequency during the later life of the asset. 
  • Invasive - Invasive inspection may damage the asset and weaken it state.
  • Recordkeeping - This approach relies on detailed recordkeeping.
  • Proactive - It requires the owners to be proactive  to see the return on investment of period inspections of the assets. 
  • Sophisticated - Requires the asset management team to be able to anticipate functional failure and to time the inspections at appropriate intervals as functional failure advances during the latter stages in the life of an asset. 
  • Capital Intensive - Requires capital-intensive diagnostic technologies.
  • Difficult to persuade owners on the merits of proactive early replacement.


Management
Listed below are some of the concepts to incorporate some of the principles of inspection-based replacement into the overall asset replacement strategy.
The two classes of replacement strategies and summary explanation of the five alternative replacement strategies.
Fig. The two classes of replacement strategies and summary explanation of the five alternative replacement strategies.


Network diagram of alternative asset replacement strategies.

Fig. Network of different asset replacement strategies.


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Fig. Inspections underway to determine replacement requirements for an asset.


Variable interval events mapped onto the P-F curve to illustrate the relationship between time and condition.
Fig. Variable interval inspections mapped onto the P-F curve to illustrate the frequency of inspections as an asset ages and approaches functional failure.


Preventive replacement mapped onto the P-F curve to illustrate the relationship with functional failure (F)
Fig. Preventive replacement mapped onto the P-F curve to illustrate the relationship with functional failure (F). Inspection replacement occurs as a result of an assessment performed prior to Functional Failure ("F").


1  Roof renewal project
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Fig.  Examples of different types of asset replacement projects.

See also:
Compare with:


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