This PhD research has developed new measurement strategies and analysis techniques to enable hydraulic transient-based condition assessment of targeted pipe sections in complex pipe systems. The conventional practice of hydraulic transient-based pipeline condition assessment involves analysis of signals from a single pressure sensor located at each measurement site. Although multiple measurement sites can be used, they are typically far apart from each other since the access points (e.g. air valves or fire hydrants) are usually sparsely located. The pressure measurement obtained from a single sensor is a superposition of reflections coming from both upstream and downstream of the sensor. This superposition makes the measured wave reflections often too complex to analyse, especially in complex pipe systems where multiple features (e.g. deteriorated sections, branches and cross-connections, and other unknown features) often exist in the pipe section of interest. The research presented in this thesis has proposed a dual-sensor measurement strategy that uses two closely placed pressure sensors at a measurement site, and has developed a wave separation algorithm that enables the extraction of the two directional pressure waves travelling upstream and downstream. The wave separation can significantly simplify the signal to be analysed, and the unprecedented directional information enables advanced condition assessment techniques to be developed. Numerical and experimental verification has been conducted, with an application to pipe wall condition assessment. In the experimental verification, conventional flush-mounted pressure transducers have been used by connecting through closely located tapping points on the pipe wall. In addition, a customised in-pipe fibre optic pressure sensor array has been developed and tested in the laboratory, as a step towards real-world implementation. The sensor array cable can be inserted into a pipe through a single access point, avoiding the use of multiple tapping points. Complexities introduced by the in-pipe cable have been investigated, and accordingly, adjustments to the wave separation and wall condition assessment techniques have been made. The wave separation technique has been further developed by using a two-source-four-sensor transient testing configuration to enable the virtual isolation of a targeted pipe section in complex systems. Two dual-sensor units (i.e. two pairs of pressure sensors) are used to bracket the targeted pipe section, with the two sensors in each pair being located in close proximity. Two transient pressure wave generators are used, which bracket the four sensors and the “virtually” isolated pipe section. This measurement strategy enables the extraction of the transfer matrix of the “virtually” isolated pipe section, which is a full representation of the characteristics of this section independent from any complexities outside the section bounded by the sensors. A novel leak detection technique has been developed based on the analysis of the extracted transfer matrix, and has been validated by numerical simulation. The technique determines the leak location and impedance (related to the leak size), and it is applicable to the detection of multiple leaks.Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental & Mining Engineering, 201
