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Acoustic Signal Processing for Pipe Condition Assessment (WaterRF Report 4360)
Paulson, P., R. Mascarenhas, G. Bell, AND B. Clark. Acoustic Signal Processing for Pipe Condition Assessment (WaterRF Report 4360). Water Research Foundation, Denver, CO, 2014.
For prestressed concrete cylinder pipe (PCCP) owners, this research is retrospectively and immediately applicable to acoustic fiber optic (AFO) monitored water and wastewater pipes. As an optimal result, PCCP owners would extend and improve the service life and operating performance of their critical pipeline assets, ultimately saving significant funds that would otherwise be used in a capital replacement program.
Unique to prestressed concrete cylinder pipe (PCCP), individual wire breaks create an excitation in the pipe wall that may vary in response to the remaining compression of the pipe core. This project was designed to improve acoustic signal processing for pipe condition assessment in an experimental environment, which includes burial, pressurization, and subsequent intentional damage to the pre-stressing wires in three specimens of prestressed concrete cylinder pipe (PCCP). The project steps included: 1) A literature search for relevant past investigations and data mining and processing methodologies 2) A series of tests, mostly on a buried PCCP pipe, to collect controlled acoustic data as the pipe’s pre-stressing compressive load was removed 3) Evaluation of data collected using advanced and emerging data mining and processing methodologies 4) Application of data mining techniques to Pure Technologies’ acoustic fiber optic (AFO) wire break database to identify pipes at varying distress levels 5) Validation of results using data collected from pipes of participating utilities The experimental data were analyzed for average RMS power and peak frequency (HEMP) analysis. The average RMS power showed promise for correlating the signal amplitude with the number of broken wires. A second test setup examined the correlation of acoustic signal response and hoop stiffness of a ductile iron pipe (DIP). The results showed that areas of increased stiffness were discernible from other areas. The ability to successfully distinguish between areas of varying stiffness may be useful in identifying areas of uniform (i.e., general) metal loss in in-service pipe.