Probabilities of Failure for ORDM
The probability of failure of an asset is generally related to the condition or performance of the asset with the key modes of failure being:
- Capacity failure
- Performance failure (maintenance related)
- Structural integrity (catastrophic failure) or condition failure.
To enable accurate estimates to be made of the current probability of failure each of these modes of failure needs to be considered.
The greatest risk cost for most service authorities will relate to structural integrity or physical asset failure, and in this case the probability will be directly related to the physical condition of the asset and its subsequent structural integrity.
In general the following can be used to assist in predicting the probability of failure:
- Historical data
- Records from other authorities, manufacturers and other sources
- Conditioning monitoring programs
- Predictive modeling
- Weibull failure distribution analysis.
There are many methods that can be used to help predict or determine the probability of failure and the major techniques that can be used are:
A detailed electronic inventory system greatly assists asset managers to model the effective life of assets based on:
- Their own experience
- Their experience with similar assets in other positions
- The experience of other authorities
- The experience and knowledge of the manufacturer of the asset.
The keeping of detailed fault records related to assets and by completing fault analysis to determine the reason for failures, and monitoring the effectiveness of actions taken to eliminate these failures.
There is no action that asset owners can take that would result in l00% accuracy of prediction of asset failures. However an electronic inventory system that lists the best available estimate of effective life of assets indicates those critical assets approaching the end of effective life.
The process therefore becomes:
- Record the asset construction date
- Give each asset the best effective life estimate available
- Check the actual condition of those assets starting with the most critical working through to those less critical.
This approach can be justification for the organization undertaking some condition monitoring activities that assist them in determining its actual effective life.