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Deterioration Model
A model to describe the process and mechanisms by which assets deteriorate and pass through different stages of failure, including:
Deterioration is described using probabilistic models and using curves to graphically represent the model.


Elements of the Model
Listed below are the key components of the deterioration model:
  • The anticipated rate of deterioration of the asset.
  • The path of deterioration (curve shape)
  • The milestone, or points or stages, along the deterioration path.
  • The thresholds that define the beginning and end of each stage.
  • The different levels of risk exposure at stages along the deterioration path
  • The actions to take at different points and during sequential stages along the deterioration path to optimize stewardship efforts.
  • The curves to illustrate the model and equations to compute the model.
The model is intended to help ascertain the probability of failure (PoF) of an asset during any particular calendar year.

    Types of Deterioration Models
    Listed below are the primary models used in asset management which can be organized into two broad groups:


          Group A: Statistical Deterioration Models
           Group B: Engineering Deterioration Models

    Class A: Performance/Degradation Curves
    Listed below are some of the elements of performance/ degradation curves.
    The six patterns form a deterioration model that includes the following insight from the study:
    Further information on each of the above noted patterns can be found on their respective pages in this asset management glossary.


    Class B: Survivor Curves
    Listed below are some of the different classes of probability distribution curves to make asset management forecasts. One of four broad classes of Iowa Curves, as follows:
    Further information on each of the above noted survivor curves can be found on their respective pages in this asset management glossary.


    Class C: Composite Curves
    Listed below are nine classes of composite curves that
    model the relationship between survivor curves and degradation curves to forecast the useful service lives of different classes of assets.
    The model was developed by David Albrice and Matthew Branch (2014) and published in the following paper: An Asset Deterioration Model


    Variables with the Deterioration Models
    Listed below are some of the key variables that are addressed in different types of deterioration models.
    The whole life of assets can be divided into life stages
    Fig. The whole life of assets can be divided into life stages - early life, mid-life and late-life.


    Decisions should consider the whole life of assets, including the I-P interval and the P-F interva
    Fig. Decisions should consider the whole life of assets, including the I-P interval and the P-F interval.



    Comparison of two common types of deterioration models: performance curves and survivor curves
    Fig. Comparison of two common types of deterioration models: performance curves and survivor curves.


    P-F interval illustrated with asphalt paving
    Fig. The P-F interval illustrated with asphalt paving along the curve.


    risk spectrum extending along the P-F interval
    Fig. The risk spectrum extending along the P-F interval.


    Comparison of negative and positive skewness on a probability distribution.
    Fig. Comparison of positive skewness ("blue" curve) and negative skewness ("green" curve) on a probability distribution.



    Our cartoon character ("I. Care") is debating whether we can reach life or extend life of assets
    Fig. Our cartoon character ("I. Care") is debating whether we can only "reach" life or, in some cases, "extend" the service life of assets.



    P-F Interval
    Fig. The P-F interval is one of the different types of deterioration models to guide facility managers and operators.


    Illustration of a deterioration model for a roof system.
    Fig. Illustration of a deterioration model for a roof system.


    The impact of maintenance on service life of an asset
    Fig. The impact of maintenance on the service life of assets.


    Ferrography as one of the predictive maintenance (pdM) technologies along the P-F Curve in relation to Potential Failure (P) and Functional Failure (F)
    Fig. Predictive maintenance (PdM) technologies along the P-F Curve in relation to Potential Failure (P) and Functional Failure (F).


    Major maintenance tasks plotted on an asset deterioration model.
    Fig. Major maintenance tasks plotted on an asset deterioration model.

    Read Articles:
    See also:

    I. Care is trying to use a crystal ball to make forecasts about the deterioration of his assets
    Fig. I. Care is trying to use a crystal ball to make forecasts about the deterioration of his assets.

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