Failure Monitoring and Asset Condition Assessment in Water Supply Systems

University dissertation from Department of Industrial Electrical Engineering and Automation, Lund Institute of Technology

Abstract: In this thesis, different aspects of failure management in urban water supply systems are discussed. As assets are getting older, the number of pipe failures is increasing and an efficient failure management strategy becomes important. Two types of failure management strategies can be applied: proactive asset condition assessment and reactive failure detection and location. Currently available condition assessment techniques cannot be extensively applied in water supply systems due to high cost and slow speed of inspection. Existing failure detection and location approaches do not allow for quick reaction to failures. Automatic failure monitoring and systematic asset condition assessment methods are presented in this thesis. Due to the different topology and hydraulic characteristics of the transmission (pipelines) and distribution (network) components of a water supply system, separate failure detection and location techniques are proposed. For both pipeline and network cases, two types of failures are considered - sudden pipe ruptures and breaks that develop over a longer period of time. For the pipeline case, a periodical leak diagnosis system based on transient response difference monitoring, is presented together with a burst monitoring, detection and location system, which is designed for rapid reaction to sudden pipeline ruptures. A single continuous pressure monitoring station is sufficient to detect and locate a failure along the whole length of a pipeline. For the network case, two continuous failure monitoring approaches are developed, which are based on steady-state (first method) and unsteady-state (second method) analysis. Continuous monitoring of the pressure is performed at a number of locations within the network. The optimal placement of pressure monitoring stations, limits of burst sizes that will be detected, uncertainty of the results and implementation aspects are discussed for both approaches. A transient-analysis-based low-cost, long-range nondestructive pipe condition assessment technique is presented that can be used as a proactive failure management tool and for rehabilitation planning in water transmission pipelines. A comparative evaluation of different pipeline sections can be made and critical sections with a high degree of deterioration can be identified. Finally, a transient-based methodology is presented, which is designed to test the seal quality of inline valves that are used to isolate pipe failures. The techniques presented in this thesis contribute to different points in the pipe asset management cycle and can improve reliability, availability, safety and efficiency of the urban water supply.