Home        About          Contact
1



Preventive Replacement Policy
One of a number of different types of asset replacement policies.

Replacement of an asset before Functional Failure ("F") occurs but after Potential Failure ("P") has been detected. It is the equivalent of an optimal interval.


Attributes
Listed below are some of the key attributes of a preventive replacement policy:


Candidate Assets
Listed below are the types of assets and their attributes that are best suited to this type of approach:
  • Bounded assets - Assets that are considered bounded assets and subject to statutory maintenance requirements.
  • Assets subject to fatigue failure - Assets with a Fatigue Failure Pattern
  • Assets subject to wear-out failure - Assets with a Wear-out Failure Pattern
  • Assets subject to Break-in Failure - Assets with an Initial-Break-in Failure Pattern.
  • Critical assets - Assets for which the financial, business or service level consequences of failure are sufficiently severe to justify proactive inspection and rehabilitation. Critical assets require more detailed attention with lower thresholds for action than non-critical assets.
  • Assets that are amenable to Time-Based Maintenance
  • Maintenance worthy items
  • Assets with a high utilization index - Asset utilization index
  • Medium-life and long-life assets. Long life assets. has a life of greater than 30-years.
  • Assets with a wide dispersion pattern - The probability distribution on the survivor curve has a wide dispersion so there is little predictability with respect to the critical year. 
  • Assets that suffer covert failure - Covert failure and concealed conditions require proactive steps to reveal condition. 
  • Assets with a left-modal curve - A left modal curve. 

Types and Variations 
There are essentially three types of preventive replacement policies, which can be summarized as follows:

Evaluation
Some of the merits of the preventive replacement approach are summarized below:
  • Economies - The owners extract the fullest possible life out of the asset and avoid any opportunity cost of replacing the asset early (ie., "reaching life")
  • Optimization - The owners enjoy the benefits of an optimal interval.
  • Damage Mitigation - Mitigation of potential collateral damage.
  • Cost Efficiencies - Reduced costs due to formal tendering process well in advance of functional failure.
  • Reduced Risk - This approach can potentially lower risk to the building owners and other stakeholders.
  • It lowers the stochastic load and improves the owners ability to anticipate and plan for future cots.
Some of the limitations and consequences of the preventive replacement approach are outlined below:
  • Stochastic assets require art as mush as science - This approach is particularly challenging because it is difficult to predict the exact point of functional failure of an asset 
  • Random Failure Patterns - Some assets have random failure patterns that cannot be easily anticipated. 
  • Sophistication - This approach requires a highly sophisticated asset management team.
  • Capital Intensive - The diagnostic technologies required by preventive replacement are capital intensive and the training of staff is also expensive.
  • Onerous Requirements - It requires a sophisticated asset management program which is both labour intensive and capital intensive.
  • Detailed Recordkeeping - This approach relies on detailed recordkeeping of operating histories.
  • Procurement - Some assets have long lead times to procurement of replacement parts so waiting until the last minute may be false economy.
  • Predictability - It is difficult to anticipate assets that are stochastic in nature.
  • Persuasion - It may be difficult to persuade the owners on the merits of proactive replacement.


Management
Listed below are some of the concepts to incorporate some of the principles of preventive 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.


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.


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).


1  Roof renewal project
1  1
Fig.  Examples of different types of asset replacement projects - roof replacement, repiping, pool basin refinishing and sealant renewal.



Beyond economic repair (BER) represented conceptually on the P-F curve
Fig. The zone of BER represented conceptually on the P-F curve, typically in the months or years preceding functional failure ("F") of the asset.


See also:
Compare with:


(c) Copyright Asset Insights, 2000-2013, All Rights Reserved - "Insight, foresight and oversight of assets" Google