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ACOUSTIC LOCATION OF LEAKS IN PRESSURIZED UNDERGROUND PETROLEUM PIPELINES
Citation:
Eckert, E. AND J. Maresca, Jr. ACOUSTIC LOCATION OF LEAKS IN PRESSURIZED UNDERGROUND PETROLEUM PIPELINES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-92/143.
Description:
Experiments were conducted at the UST Test Apparatus Pipeline in which three acoustic sensors separated by a maximum distance of 38 m (125-ft) were used to monitor signals produced by 3.0-, 1.5-, and 1.0-gal/h leaks in the wall of a 2-in.-diameter pressurized petroleum pipeline. he range of line pressures and hole diameters used in the experiments were 10 60 20 psi, and 0.4 to 0.7 mm, respectively. pplication of a leak location algorithm based upon the technique of coherence function analysis resulted in mean differences between predicted and actual leak locations of approximately 10 cm. he standard deviations of the location estimates were approximately 30 cm. his is a significant improvement (i.e., smaller leaks over longer distances) over the cross-correlation-based techniques, which are currently being used. pectra computed from leak-on and leak-off times series indicate that the majority of acoustic energy received in the far-field of the leak is concentrated in a frequency band from 1 to 4 kHz. he strength of the signal within this band was found to proportional to the leak flow rate and line pressure. nergy propagation from leak to sensor was observed via three types of wave motion: ongitudinal waves in the product, and longitudinal and transverse waves in the steel. he similarity between the measured wave speed and the nominal speed of sound in gasoline suggests that longitudinal waves in the product dominate the spectrum of received acoustic energy. he effects of multiple-mode wave propagation and the reflection of acoustic signals within the pipeline were observed as non-random fluctuations in the measured phase difference between sensor pairs. dditional experiments with maller holes and higher pressures (20 to 50 psi) are required to determine the smallest leaks that can be located over distances of several hundred feet. he current experiments indicate that improved phase-unwrapping algorithms and/or lower noise instrumentation are required to optimize system performance. his report was submitted in fulfillment of Contract No. 68-03-3409 by Vista Research, Inc., under the sponsorship of the U.S. Environmental Protection Agency. his report covers a period from 23 January 1991 to 31 October 1991, and work was completed as of 30 September 1991.