Pipe system diagnosis and leak detection by unsteady-state tests. 1 Harmonic analysis

Since leak reduction actually corresponds to the acquirement ofnew water quality resources, development of leak detection methodologies is a non-trivial scientific and engineering issue for the water resources community. In this paper and in the companion paper it is shown that unsteady-state tests can be used to pipe diagnosis and leak detection. Specifically, in this part the governing equations for transient flow in pressurized pipes are solved directly in the frequency domain by means ofthe impulse response method. The analytical expression ofthe piezometric head spectrum at the downstream end section ofa single pipe system during transients is then derived. Within this approach it is shown that the piezometric head spectrum is the product oftwo terms: the former related only to the maneuver characteristics, the latter depending only on the characteristics ofthe system. In the case off ast linear closure maneuvers, the analytical expression ofboth terms is also given. The derived analytical solution ofthe pressure signal in the frequency domain, allow us to interpret the data acquired in a single pipe system to have information on its state. Experimental data are compared to the analytic solution.