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COBEM 2019
25th International Congress of Mechanical Engineering
ON THE DIFFERENCE BETWEEN GROUND AND PIPE VIBRATION MEASUREMENTS OF LEAK NOISE FOR LEAK DETECTION PROBLEMS
Submission Author:
Fabricio Cesar Lobato de Almeida , SP
Co-Authors:
Fabricio Cesar Lobato de Almeida, Michael Brennan, Oscar Scussel
Presenter: Fabricio Cesar Lobato de Almeida
doi://10.26678/ABCM.COBEM2019.COB2019-1816
Abstract
Leak location in a buried water pipe can be carried out by measuring the vibration of the pipe or via the ground vibration above it. This is possible due to pipe-soil interaction and wave propagation caused by the excitation due to the leak. To measure the vibration due to a leak, sensors are placed on the ground and signals are then collected. However, for the vibration measurements in the pipe, the sensors can only be placed at available positions. The measured phase between these sensors can be used to locate the leak. For ground vibration measurements, however, two types of waves, shear and compressional waves, propagate into the soil. The interaction between these waves is observed as two different phase gradients in distinct frequency ranges due to the differences in the speeds of these waves. Moreover, the pipe vibration due to the leak, which is a fluid borne type wave, has a straight-line-like behaviour. Hence, this paper shows these differences by using actual leak data collected in a special test rig to simulate leak conditions. The coherence and, the modulus and phase of the Cross Spectral Density (CSD) are used to show how these measurements can differ from each other.
Keywords
Leak detection, Ground Vibration, Pipe Vibration, Vibro-acoustic Techniques
