Leak-before-break in cast iron mains: a failure analysis of a catastrophic pipe burst on Harris Street, Sydney

This article analyses the failure of a 500 mm-diameter cast iron (CI) water pipe that catastrophically fractured in Sydney in 2013. According to metallurgical analysis and finite element simulation, a longitudinal pre-existing crack initiated from the adjacent bell-joint and eventually propagated to a critical length in the pipe barrel over a certain period. There was evidence of leakage prior to the burst incident but information was inconclusive whether it was exactly from this pipe. Fatigue caused by cyclic internal pressure was considered as the predominant factor in leading to crack growth. A numerical model was developed to describe crack growth behaviour using Paris' law, and metallurgical analysis and mechanical tests were conducted to support this investigation. Based on the field evidence and simulation results, the leak-before-break approach might be applicable in CI pipes to avoid severe consequences of trunk main bursts.