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| CSIRO | SOLVE | Issue 6 Feb 06 | |
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ARTICLE
PREDICTIVE MODELLING:
Probability and the Problem of Predicting Pipe Breakdown By Youna Angevin-Castro
Some smart laboratory work, dovetailed with forensic evidence from past structural failures in water mains, will give water authorities a better chance to predict potential failures in underground pipe networks. A handy crystal ball in the form of a new predictive modelling tool means authorities can better target their maintenance and act on potential problems before being hit with the cost and disruption of a burst water main. The predictive models have been developed by Dr Paul Davis of the Future Cities Research Theme of CSIRO Manufacturing and Infrastructure Technology, and are designed to estimate failures in underground pipes made from newer materials such PVC and polyethylene. The models were developed as part of two projects jointly funded by the American Water Association Research Foundation. “Older pipeline networks have the benefit of historical data, which allows utility companies to roughly forecast what is likely to happen over the next two years,” says Dr Davis. “However, failure rates in newer materials such as PVC and polyethylene are relatively low and they have not been in the ground long enough to have collected significant amounts of historical data to support accurate statistical predictions.” His research started in the laboratory, where a physical model was developed and tested under conditions replicating typical installations of underground pipes. Using short sections of pipe, the model showed high accuracy for predicting failure. However, there were shortcomings when applying the model in the field. Dr Davis says: “In the lab we developed a good understanding of material, degradation, crack growth and fracture aspects of the problem. However, we had a model that had been developed under well-defined conditions in the lab. If you try to take that across into the field, you have problems. If you have 100 kilometres of pipe, you can’t apply this kind of model unless you know the condition along the entire length of the pipe.” To overcome this, he developed a model that uses probability distributions, developed from anecdotal evidence from industry and ‘forensic’ investigation of failed pipes, to estimate the probable defect size along any given point on a pipe and the probable loading conditions the pipeline experiences. “The models preserve the details of physical degradation and failure mechanisms which occur in service, and can account for changes in operating loads and the surrounding soil environment. However, we can also extrapolate the models to estimate network-wide failure rates, which are more meaningful for utility asset managers.” With the cost of repairing and maintaining Australia’s existing water and wastewater infrastructure estimated to be more than $130 million every year, the economic value of being able to predict failures is significant. Insurance claims from local business and indirect costs associated with traffic disruption can add to the direct cost of pipe repair. And while water companies have embraced the model, it can also be adapted to suit other industries, such as the gas industry. Future projects for Dr Davis include investigating the continuing effects of climate and the soil environment on buried pipelines, following the recent award of an Australian Research Council grant in collaboration with Monash University. For further information contact: |
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