Rapid response non-destructive inspection robot for condition assessment of critical water mains

© 2018 Australasian Robotics and Automation Association. All rights reserved. This paper presents a robotic system that is able to rapidly assess the wall thickness of a cement lined cast iron (CI) water main pipe during the short time interval between a pipe failure and its repair. Wall thickness measurement through a cement lining of unknown depth is achieved using a sensor based on the pulsed eddy current (PEC) technique. Sensor geometry is selected such that remaining wall thickness' up to 20mm can be reliably measured. A six arm mechanism incorporating inbuilt compliance allows contact between the sensors and cement lining to be maintained even when the cement lining thickness is non-uniform; which is typically the case with in-situ lined pipes. A cart capable of navigating debris and steps transports the sensing mechanism through the pipe and also ensures it is positioned concentrically within a range of pipe sizes. Descriptions of the sensing strategy, sensor mechanism, driving cart and the robot control system are presented together with results from actual in-field pipe deployments to demonstrate effectiveness of the developed system