Edward John

Research Project: Understanding how the deterioration of cast iron pipes evolves into leakage

Summary: Using destructive testing, this project aims to advance the water industry’s understanding of how leaks form in grey cast iron water pipes and improve our ability to predict leakage onset.

Detailed Description: In 2017 approximately 22% of all drinking water put into UK water distribution pipes was lost to leakage. High levels of leakage put pressure on our water supplies and reduce the efficiency of the water supply system. To ensure that the UK’s water supplies are resilient against a 0.5% annual probability drought, the water industry has committed to halving leakage by 2050, compared to 2017-18 levels. One aspect of reducing leakage is understanding of how leaks occur in the first place and modelling this process. Grey cast iron (GCI) water pipes are brittle and vulnerable to pitting corrosion. As a result, it is very likely that cracking of the pipe material is a key leak initiation mechanism for GCI pipes. Buried water pipes experience cyclic loading from variable water pressures, passing road vehicles, temperature fluctuations, and soil moisture response. These loads create multiaxial, time-variable stress profiles within the pipe walls. To understand how these stresses lead to the formation of leaking cracks, lab-based experiments are needed so the process can be controlled and observed in a way that is not possible in the field. This project will develop an experiment that can accelerate the fatigue cracking process so that large volumes of cycles-to-leakage data can be gathered. This data will be used to validate a fatigue criterion which, coupled with existing models for the other major leak initiation mechanisms, will enable the stress cycles to leakage for a given GCI water pipe to be calculated. This tool will mean that water pipes can be targeted for replacement shortly before they are predicted to begin leaking. This type of proactive maintenance should reduce the number of new leaks that form, helping the water industry to meet its commitment of halving leakage by 2050. The project is sponsored by UK Water Industry Research (UKWIR) and hosted by the University of Sheffield. Supervisors of this project are Luca Susmel, Joby Boxall, Richard Collins, and Elisabeth Bowman from the University of Sheffield, and Dennis Dellow from UKWIR.

Published Articles

John, E., Boxall, J., Collins, R., Bowman, E., Susmel, L. (2024) 'Multiaxial fatigue of water pipe grey cast iron', International Journal of Fatigue, 178, 108002, https://doi.org/10.1016/j.ijfatigue.2023.108002

Conference Presentations

John, E., Boxall, J.B., Collins, R., Bowman, E., Dellow, D., Sumel, L. (2023) ‘Impact of experimentally determined grey cast iron pipe fatigue strength variation on years-to-leakage predictions’ 19th International Computing and Control for the Water Industry Conference (CCWI) 4-7 September 2023, Leicester (UK)

John, E., Boxall, J.B., Collins, R., Bowman, E., Sumel, L. (2022) ‘Investigating an alternative to exhumed grey cast iron water pipes for small-scale fatigue tests’ 2nd International Joint Conference on Water Distribution Systems Analysis & Computing and Control in the Water Industry (WDSA/CCWI) 18-22 July 2022, Valencia (Spain), https://doi.org/10.4995/wdsa-ccwi2022.2022.14005

Poster Presentations

John, E., Boxall, J.B., Collins, R., Bowman, E. and Sumel, L. (2023) ‘Plain and notch fatigue strength of water pipe grey cast iron' 7th International Conference on Engineering Structural Integrity Assessment and 2023 International Symposium on Structural Integrity (ESIA17–ISSI2023)  23–25 May 2023, Manchester (UK)