form of asset
replacement policy that may fall
into the preventive
replacement class but only if the inspection takes places
Failure ("F") has occurred.
is replaced only if it fails to meet the standards established by a Facility
Condition Assessment (FCA).
Listed below are some of
the key attributes of the Inspection Replacement Policy (IRP):
In order for IRP to succeed as a proactive approach,
it requires some of the following:
Maintenance - IRP is founded on the principles of condition-based
maintenance (CbM) which is not driven by rigid time
Strategies - IRP carries out inspections on variable intervals
depending on the age and exposure conditions of the asset.
should be based on a complete operating history
of measured condition
observations to identify trends and patterns in the data.
Maintenance - The method relies upon predictive maintenance
(PdM) technologies and continuous monitoring / commissioning
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.
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
Conditions - The inspections will sometimes need to reveal
- Effective Age
- Determination of the effective
age of the asset relative to its chronological age.
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
this approach is best suited to assets that have the
Listed below are some examples of an effective IRP
approach to asset management:
- Asset that can be inspected, preferably
through visual observations or limited destructive testing.
replaced our roof after the condition assessment identified blisters in
the membrane, which were prevalent throughout and systemic.
deferred the replacement of our roof after the inspection found that
problems were localized to one area and could be addressed with
Some of the merits of this approach are summarized below:
Some of the limitations of this approach are listed
- Empirical Data
- The status of some systems and assets
can sometimes only be determined only by physical inspection.
Program Coordination - The inspections can form part of
the condition-based maintenance program.
Mitigation - Mitigation of potential collateral damage
Efficiencies - Reduced costs due to formal tendering
process well in advance of functional failure.
- 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 inspection may damage the asset
and weaken it state.
- This approach relies on detailed recordkeeping.
- It requires the owners to be proactive to see the return
on investment of period inspections of the assets.
- 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
Intensive - Requires capital-intensive diagnostic
- Difficult to persuade owners on the
merits of proactive early replacement.
below are some of the concepts to incorporate some of the principles of
inspection-based replacement into the overall asset replacement
Fig. The two
classes of replacement strategies and summary explanation of the five
alternative replacement strategies.
Fig. Network of
different asset replacement strategies.
Fig. Inspections underway to determine replacement requirements for an
interval inspections mapped onto the P-F curve to illustrate
frequency of inspections as an asset ages and approaches functional
replacement mapped onto the P-F curve to illustrate the relationship
with functional failure (F). Inspection replacement occurs as
result of an assessment performed prior to Functional Failure ("F").
Examples of different types of asset replacement projects.