Reliability-Based Service Life Prediction of Corrosion-Affected Cast Iron Pipes Considering Multifailure Modes

Abstract

Cast iron pipes were widely used in water distribution networks before the 196s and the majority of them have become aged and deteriorated with corrosion, which has been identified as one of the most common mechanisms of pipe failures. To have an optimum strategy for repair and/or replacement in the management of pipe assets, accurate prediction of the service life of the pipes is essential. This paper attempts to propose a method for reliability analysis and service life prediction for corrosion-affected pipes. Both loss of strength and fracture toughness of the pipe are considered in assessing pipe failures using a system reliability method. A sensitivity analysis is also carried out to identify those factors that affect the pipe behavior and failure the most. It is found in the paper that the probability of pipe failure is considerably greater when multifailure modes are considered as a system than when each failure mode is considered individually. It is also found that the likelihood of pipe failure due to loss of toughness is more than three times higher than that due to loss of strength. The paper concludes that multifailure modes should be considered in predicting pipe service life using a system reliability method as proposed here. The proposed method can improve the ability of the water industry in predicting and preventing catastrophic failures of the water pipes.