New Finding in Cast Iron Pipe Wall Defects Using Free Swimming Ultrasonic Thickness Testing Technology

In March 2022, an inspection of a 1950s 20-in. cast iron main was completed using ultrasonic thickness testing technology. In June 2023, a pipe segment on the inspected portion of the 1950s cast iron main catastrophically failed. No wall loss was identified in the first analysis of the failed pipe segment. A re-analysis of the data from the March 2022 inspection indicated that approximately 15 atypical signals were present on the failed pipe segment. Further investigations of the failed pipe segment revealed suspected graphitic corrosion present at each of the atypical signals that were available for closer inspection. Re-analysis of the entire pipeline showed an increase from 13.5% to 40% of pipe segments with wall loss or suspected graphitic corrosion. This paper will discuss the failure, the re-analysis, and investigations on the cast iron main, focusing on the atypical signals and WaterOne’s steps taken to manage the pipeline.