Experimental evaluation of bursting capacity of corroded grey cast iron water pipeline

Abstract

Cast iron was used in the water industry prior to 1970 and a large number of cast iron pipes still remain as trunk mains. These pipes have been subjected to different levels of corrosion and variety of loading conditions. This leads cast iron pipes to fail in the field without prior warning. Water utilities are seeking solutions to optimise cast iron pipe renewal and rehabilitation programs for critical water mains (diameter ≥ 300 mm). A new experimental set-up has been developed at Monash University in order to perform burst testing of large diameter cast iron pipes (diameter ≥ 300 mm). A section of cast iron pipe, extracted during maintenance in Sydney, was laser scanned to determine the remaining thickness of the pipe (minimum of 7–8 mm at the most critical patches). Although the pipe was pressurised to 3.6 MPa, catastrophic failure did not occur. Water leakage from the two critically corroded patches was observed at around 3.25–3.45 MPa internal pressure. Strain results on the outer pipe surface were greater than the strain measured during tensile testing of the same pipe material. A 3-D finite element model using the scanned pipe dimensions was able to predict the maximum pressure at pipe failure (~3.7 MPa) within the range of leaking water pressure level observed in the experiment.

Keywords:

• Cast iron
• water pipelines
• remaining life
• large diameter
• pipe failure
• corrosion
• bursting capacity

Acknowledgements

The authors would like to acknowledge the financial support provided by ACAPFP project funded by Sydney Water Corporation, Water Research Foundation of the USA, Melbourne Water, Water Corporation (WA), UK Water Industry Research Ltd, South Australia Water Corporation, South East Water, Hunter Water Corporation, Queensland Urban utilities and City West Water in this study.