Using water hammer to enhance the detection of stiffness changes on an out-of-round pipe with distributed optical-fibre sensing

Over the last few decades, distributed optical fibre sensor (DOFS) has been introduced to monitor the structural health of water pipelines. Most of the previous studies show that DOFS is very effective as a static measurement and monitoring platform. However, there is still a lack of research being done using DOFS to monitor the dynamic response of the pipeline. This paper will first demonstrate the dynamic capability of optical frequency domain reflectometry-based DOFS on a pipe. To be specific, the primary monitoring work is conducted on an out-of-round plastic pipe subjected to water hammer. It is important to monitor the dynamic response of the pipe as it is well known that water hammer can occur in any pressurised pipeline system due to changes in the operating conditions. The ability to detect local stiffness irregularity on the noncircular pipe subjected to water hammer is also demonstrated. The result shows that the presence of the local stiffness change is accentuated when the pipe is subjected to water hammer. The dynamic capability of DOFS facilitates the application of water hammer as a stimulus and hence shows the potential to enhance pipeline health monitoring.