Full Description

In the absence of historical failure data, physical probabilistic models based on fracturemechanics are under development to estimate failure rates in buried PVC and PEpipelines. A model for PVC pipes has been completed and uses linear elastic fracturemechanics (LEFM) to predict time to failure. Although LEFM is valid for PVC pipes,the development of a large craze zone during PE pipe fracture necessitates the use ofelastic plastic fracture mechanics (EPFM) theory. An EPFM-based model for PE pipesis under development and some preliminary results are presented. In both models,inherent defect size in the pipe wall is represented as a stochastic variable, based onmicroscopic examination of field failures in PVC pipes. In the absence of sufficientdefect size data, the variation in defect size in PE pipes is assumed to follow that forPVC pipes. Monte Carlo simulation is then used to estimate the probability of fracturefailure for a pipe with a defect in its wall. The resulting physical probabilistic failuremodels show good agreement with actual PVC pipe failure data recorded by United Kingdom waterutilities. While agreement is also encouraging for PE pipes, values of operatingpressures used in the model are significantly higher than those expected in service.Future development of the model is proposed to include the effect of excessive externalloads on PE pipe failure rates. Includes 18 references, tables, figures.

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Edition: Vol. - No. Published: 09/01/2005 Number of Pages: 11File Size: 1 file , 380 KB