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Failure Replacement (Policy)

One of several types of asset replacement policies.

Replacement of an asset after it has reached Functional Failure ("F") or is in the process of undergoing functional failure, rather than replacement before failure has occurred. The latter is referred to as Preventive Replacement. 


Attributes
Listed below are some of the key attributes of the failure replacement approach:

  • Leading Indicators - Telltale signs (leading indicators) of pending failure are ignored.
  • Reactive Funding - These projects are typically funded by reactive funding.
  • Beyond Economic Repair - The asset is allowed to deteriorate (either consciously or unintentionally) until it is irrepairable and must be replaced.
  • Lag Times - Management of the renewal project occurs during the lag time period after failure has occurred.

Causes
Listed below are some of the primary causes of a failure replacement scenario:
It is important to establish whether the owners have enough information to make a truly informed decision.



Classification
There are two general types of failure replacement, depending on the owners' prior knowledge and conscious decisions regarding the risks and effect of failure:



Candidate Assets
Listed below are the types of assets and their attributes that are best suited to this type of approach:
  • No repair is feasible.
  • Short Life Asset - Sometimes short life assets.
  • Disposable Assets - Assets with disposable parts.
  • Low-Materiality Assets - Small assets without signficant financial value - low capitalization assets
  • Non-Critical Assets - Assets that are not critical or inconsequential
  • Durable Assets - Assets that are not subject to wear or assets that are unlikely to fail - robustness
  • Redundant Assets - Redundant assets - redundancy
  • Assets that exhibit Random Failure Patterns - Some assets have random failure patterns that cannot be easily anticipated. These assets are stochastic in nature in that their behaviour is non-deterministic, sporadic and random.
  • Assets with a low utilization index - Asset utilization index.
  • Non-Maintainable Assets - Some assets are unmaintainable or can be allowed to run to failure with minimal risk to the owner.
  • Discretionary Maintenance - Assets that are not subject to statutory maintenance requirements.
  • Assets that are subject to graceful degradation - Assets that exhibit characteristics of fault-tolerant degradation - ie., graceful degradation. A measure of the degree of fault tolerance (robustness) of a system. The property that enables a system or asset to continue operating properly in the event of the failure of some of its components.
  • Assets that suffer overt failure
  • Assets with a narrow dispersion pattern - The probability distribution on the survivor curve has a narrow dispersion and therefore there is some predictability in the critical year.
  • Assets with a negative aging profile - negative aging  
  • Assets with a right-modal curve -
These assets are not amenable to traditional Time-Based Maintenance (TbM) strategies and require a fundamentally different set of principles, tool and techniques in order to derive deterioration models and make reasonable predictions.


Evaluation
Some of the merits of the failure replacement approach are summarized below:
  • Lower Short-term Cost - Reduced inspection and monitoring costs over the life of the asset.
Some of the limitations and consequences of a failure replacement approach are summarized below:
  • Cost Inefficiencies- Higher costs due to the absence of a tendering process or an accelerated process due to the reactive nature of the work.
  • Lower Mitigation -
  • Greater Contingency Costs - Resultant and collateral damage (such as water leaking from a roof causing deterioration of interior paintwork and furnishings).
  • Higher Risk - Increased risk to the building and occupants and stakeholders.
  • Increased Soft Costs - Additional costs (such as an emergency costs fire watch that must be conducted while the fire system is down and new parts are being ordered).
  • Increased Nuisance - Increased nuisance and disruption.
  • Potential Emergency Costs - Shortened procurement time eliminates opportunities for competitive tendering to secure the best pricing. The owner ends up paying a premium for rushed services.


Management Principles 
Failure replacement does have a legitimate role to play in a replacement strategy. The challenge is to find the right balance.

Listed below are some of the concepts to incorporate some of the principles of failure replacement into the overall 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.


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Fig. Blistering in a polyurethane roof assembly.


Asset replacement policies must align to asset risk profiles in order to achieve optimization and satisfy ISO 55001 requirements
Fig.  Asset replacement policies must align to asset risk profiles in order to achieve optimization and satisfy ISO 55001 requirements.


A balanced asset replacement mix helps the organization to achieve optimization in conformity with ISO 55001 principles
Fig. A balanced asset replacement mix helps the organization to achieve optimization in conformity with ISO 55001 principles.



Network diagram of alternative asset replacement strategies.
Fig. Network diagram of different asset replacement policies organized into the two broad classes of failure replacement and preventive replacement.


Illustration of a deterioration model for a roof system.
Fig. Illustration of a deterioration model for a roof system with distress metrics at different life stages.


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Fig. Failure replacement policies highlighted in yellow on a network diagram of alternative replacement strategies.


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Fig. Collateral water damage is an examples of one of the circumstance associated with failure replacement.


Network diagram of different asset replacement policies organized into the two broad classes of failure replacement and preventive replacement.
Fig. Network diagram of different asset replacement policies organized into the two broad classes of failure replacement and preventive replacement.


The relationship between the P-F Interval and different replacement strategies.
Fig. The relationship between the P-F Interval and different asset replacement strategies, particularly in relation to Functional Failure ("F").


See also:
Compare with:


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