VICKSBURG, Miss. - The sensor-transmitted sounds of leaking pipes are music to the ears of Research Environmental Engineers Dr. Victor Medina and Scott Waisner.
Medina and Waisner, with the U.S. Army Engineer Research and Development Center (ERDC) Environmental Laboratory (EL), are currently partnered with the Naval Facilities Engineering Command (NAVFAC) and the Battelle Memorial Institute, an Ohio non-profit research organization, to test acoustic leak detection systems for water supplies as part of a Department of Defense (DoD) Environmental Security Testing Certification Program (ESTCP) project.
The leader of EL’s Environmental Security Engineering Team (ESET), Medina said these studies are comparing two acoustic leak detection approaches for an analytical report.
“The report will be led by NAVFAC, but EL will participate in its preparation. This report will assist military installations in evaluating if these sensors would be useful in monitoring their pipe networks, cost estimates of implementation and estimated return on investment,” Medina said, emphasizing the advantages of detecting leaks early before major damage and expenses occur.
“In June, a test bed installation slightly longer than a football field was prepared in the Poor House area,” Waisner said, referring to the large field on the Vicksburg campus adjacent to Porter’s Chapel Road. The test bed was configured “with a combination of PVC and iron pipe with known leak points. This allows highly-controlled leaks for testing different acoustic configurations,” Waisner said.
Chris Griggs, ESET physical scientist, performs the field demonstration and joined Waisner in commending ERDC’s Directorate of Public Works (DPW) for its vital role in creating the test bed.
“The field demo would not have been successful without the outstanding support from Tony King and the DPW crew,” Griggs said. “Also, this project highlights ERDC’s property as a great asset. We are able to do a large-scale demo here at the installation with NAVFAC and Battelle coming to us. It is a major logistics and economic advantage to have this capability right here in our backyard.”
In addition to the test bed, a dozen sensors were deployed throughout ERDC’s campus to monitor the existing pipe network. These were selected to monitor about 60 percent of the pipe network, while providing a clear signal to the “alpha” collection point equipment mounted on the EL building’s roof.
“We mounted orifice plates, which are small plates with holes of known diameter drilled through them, in valves attached to the pipes,” Waisner said. “These valves are opened and closed manually by t-handle attachments. By opening and closing combinations of these valves, we can create multiple leak points with different leak rates.
“Sensors were mounted on fittings connected to the pipes, such as fire hydrants, valves and risers, and they detect and capture the vibrating sounds carried by the pipe walls. Every sound source has an acoustic signature, much like a musical score.
“Two sensors close enough to a leak will hear the same acoustic signature but at different times and amplitudes due to the speed at which that vibration travels through the pipe wall. By matching the acoustic signature, calculating the time difference in the signatures, and the length and type of pipes between the sensors, the software can actually calculate the location of the leak,” Waisner said.
The researchers tested systems from two different vendors that use the same basic technological principals but implement the technology in different ways. One system is geared primarily toward a deliberate hands-on evaluation of a water distribution network. “Basically, you pick the specific location in the distribution network that you want to evaluate, attach sensors, record the acoustics, and then move to another location,” Waisner said. “The data is downloaded to a computer and evaluated to detect leaks.”
The second system is geared toward continuous monitoring of a water distribution network with numerous sensors placed on the network. The sensors daily upload their data wirelessly via local repeaters and one or more alpha units. The alpha units then send the data to a central server via a standard commercial cellular network to the internet. The data is evaluated daily by the software, which can be accessed by a web interface. The software also sends automated alerts when a probable leak is detected.
Medina’s group is exploring other teamwork opportunities with NAVFAC, including an existing ESTCP effort focusing on waste-to-energy for forward operating bases.
Meanwhile, the sounds of water leaks can be monitored as intended, following early project challenges pointed out by Griggs.
“Despite an unexpected gas leak, water leak, and rain the first day, ERDC team members really pulled together to make this a success. This is a direct reflection on the great folks we have at ERDC.”