Probabilistic Life Assessment


Probabilistic Assessment - providing realistic estimates of component remaining life

In the increasingly cost-competitive market, accurate and timely information on equipment condition is vital for input into repair/replacement strategies and associated costs. This results in an increased need for more reliable and realistic life prediction methods, particularly for aged equipment/plant. 

Existing remaining life evaluation techniques and defect assessment procedures are deterministic, in that they require specific data input. In most practical situations, the key inputs to a deterministic life assessment are not single valued but distributed - through spatial changes (e.g. thickness, temperature, stress, etc) or temporal variability (e.g. operating conditions, ageing, etc) through the imprecision of measurements and scatter in the data (e.g. inspection, on-line monitoring data, materials data, etc.) 

To take into account these uncertainties/variations, the deterministic assessment is based on the “worst-case scenario” and conservative values/bounds for the inputs are used in the analysis. However, this generally provides an overly conservative and unrealistic result. 

One way to provide a more realistic estimate of the component remaining life is to use a Probabilistic Approach that enables statistical quantification of the variation in the key inputs in terms of a nominal value and the scatter or drift around this value.

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Comparison of the deterministic and probabilistic approaches to life assessment, showing that the probabilistic approach allows longer component operation