Intelligent Listening

ADS Environmental Services leak-detection technologies help water-utility professionals pinpoint trouble and make repairs efficiently

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Leak-detection technology continues to be refined. Various technologies have been used in equipment to detect leaks, each with strengths and weaknesses.

 

ADS Environmental Services, a division of ADS LLC, based in Huntsville, Ala., sells a series of high-technology leak-detection products that rely on acoustic-listening technology. The equipment is manufactured by Primayer Ltd., based in the United Kingdom. ADS is an IDEX Water & Wastewater Business, based in Northbrook, Ill.

 

A team from ADS and Primayer demonstrated two systems in a residential neighborhood in Chicago on Dec. 3, 2009:

• Mikron acoustic probe units, used to detect and pinpoint leak locations by listening in real time.

• The Eureka Digital system, used to monitor leaks in real time or to log leak activity at designated times to be analyzed later.

 

Conducting the demonstration were Steve France, global sales director with Primayer Ltd.; William Doyle III, water loss control client services; Terry Keeling, field technician; and Steve Huggins, Midwest project manager, all of ADS Environmental Services.

 

Walk-around

The Mikron locating system can use either of two listening devices. The Gamma ground microphone unit is a cylinder about the size of a large coffee can that can be attached to a wand for easy operation. The Alpha handheld listening device, about the size of a coffee cup, also has a detachable wand, as well as a magnet on its face (the surface that receives sound) that can adhere to any iron or steel water main fixture, such as a fire hydrant.

 

The Mikron system comes with a handheld amplifier and display unit for operating the system and interpreting the findings. It has a simple control panel consisting of a small LCD screen and five control buttons to activate the system, set playback volume, and set parameters for leak detection. A high-impact carrying case is included.

 

The Eureka Digital locating system consists of two wireless digital transmitter devices, one red and one blue for easy distinction, each equipped with a sound sensor or accelerometer. The devices are used to triangulate a leak location by correlating the differences in leak noise transmitted to two different locations.

 

A separate receiver module can also use a third sensor device for greater precision. Headphones and a carrying case and battery charger are included. Users can choose one of two tablet computers for data analysis, or install software (included with the package) on their own laptop computer.

 

Operation

France joined three ADS representatives at the intersection of North Hoyne Avenue and West Iowa Street in Chicago, a residential neighborhood about 3.5 miles west of Lake Michigan.

The target leak was one ADS had detected previously as part of an ongoing project with the city. Keeling opened a manhole in the center of the intersection. Inside, water could be seen bubbling back from the water pipes, but the exact source of the leak was not visible.

 

“Leak detection is equated to a formula with about four unknowns,” France says. “You’re never quite sure what’s in the ground, where there have been repairs to the pipes, or whether the mapping has been updated after repairs — all things that can affect where that leak position is. So you need this logical process to try and eliminate the unknowns.”

 

Doyle began by demonstrating the Mikron system. He attached the smaller Alpha unit to a nearby hydrant, and the magnet on the unit’s base connected to the iron hydrant with a sharp click. He then plugged the unit into the control panel, turning on the top button to activate the headset circuit. Using the bottom button on the panel, he selected an appropriate sound filter for the pipe composition, in this case, a range of 75 to 750 Hz for cast iron.

 

“When water comes out of a pipe, there’s an energy transfer, and what you’re looking for is that energy transfer,” France explained. “You’re listening for the sound traveling down the outside of the pipe.” The leak made a noise in the headset like the sound of a shower heard one room away from a bathroom. The unit converted the sound to an index number.

 

The index number does not measure a particular sound unit (such as decibels), but simply reflects the relative sound intensity on a scale from zero to 99. The index is useful as an operator moves in the vicinity of a leak, such as along a pipeline, because it reports whether the noise of interest is getting louder or softer.

 

Doyle switched to the larger Gamma ground microphone, which he attached to a wand handle, then walked in the street, following the approximate path of the pipeline. The panel’s LCD screen displayed three boxes in a horizontal row, the right-hand one larger than the other two. The larger box displayed a series of increasing numbers: the index number for the level of the sound.

Doyle pressed the panel’s center button, and the index number at that moment was captured and displayed as a constant in the center box on the screen. Then, as he proceeded further, the real-time number continued to rise, while the center, unchanging number allowed him a quick comparison with the previous reading. By walking the path of the pipeline and observing the rising and then falling index number, Doyle approximated the location of the leak.

 

The team then demonstrated the Eureka Digital correlation system. France explained that correlation systems help pinpoint leaks by comparing the differences in the sounds the leak makes when heard from two or more points.

 

“If the leak is in the middle, the noise will reach both sensors at the same time,” France said. “But if it’s closer to one unit, it will reach that unit first and the second unit later. We’re looking for that time delay. Then, if we know exactly what that pipe length is, we can determine where the leak is.”

 

Some correlation systems are used in real-time listening, and others can be set to record the sound remotely for later analysis. The Eureka Digital system can be used in either situation.

 

Doyle and Keeling set out two sensors/transmitters, one on the same nearby hydrant and the other on a hydrant about 300 feet away. When the system was turned on, the transmitters collected sounds that radiated through the pipe system and transmitted the data via radio signals back to a receiver connected to a laptop computer equipped with the appropriate software.

 

On the computer, the software displayed a series of screens. Two small displays on the right showed the signal from the blue and red transmitters. A large horizontal screen that dominated the display showed a series of spikes along a horizontal graph. Within a few minutes the spikes coalesced and peaked at a single area of the graph. The resulting information allowed Doyle to establish the likely location of the leak along the pipeline.

 

France explained that correlation systems take brief samples of sound, compare their signatures, and then make calculations accordingly. Typically, the spot identified through correlation is considered a “point of interest,” rather than a confirmed leak. Then a ground microphone like the Mikron Gamma can be used to help confirm the location: The user walks with the device over the pipeline area where the point of interest has been identified.

 

Observer suggestions

Each of the units demonstrated quickly and clearly conveyed the expected information about water loss in a fashion that would be readily interpreted. The Mikron system’s simple controls suggested it would be easy to learn to use, although experience would be required to make the most accurate interpretation of findings. The Eureka Digital display was clear and easy to decipher. All the equipment appeared convenient for even a single operator to place and use.

 

Besides these two items, the team demonstrated two more Primayer systems that ADS is marketing. The Eureka 2R is a real-time correlation system that uses its own control panel to report findings. The Enigma is a recording correlation system with three to eight detection units that are synchronized, put out in secure locations such as in manholes surrounding a suspected leak, and timed to collect data at the most desirable time, such as at night, when traffic noise is less likely to confound the findings. The Enigma is used with software installed on a laptop computer to analyze the information.

 

Manufacturer comments

France pointed out that effective leak detection with any equipment benefits from training and experience, as well as time in the data-collection procedure. For instance, ordinary use of water services in a residential neighborhood — morning showers, dinner-time dishwashing, and so on — can get confused with leak-generated noise.

 

That makes it especially helpful to use logging-correlation equipment, which can be set to record data at times when there is no traffic and little other activity.

 

“The big thing is using the right tool for the right job,” said France. “A lot of that comes down to the right tool for the right operator, because there are people who are new to leak detection, and there are people who are very experienced. A small town that has 10 or 20 leaks a year will go with something quite simple. If they only have a few miles of pipe, they might use only one ground microphone. A big city like Chicago needs more sophisticated tools.”

 

France noted that the Mikron units have two key features that enhance their effectiveness. “First, the sensor is decoupled from the outside world as much as possible,” he said. “The biggest enemy of a ground microphone is wind noise — it masks the leak noise.” The Mikron units’ sensors are mounted on a rubber boot that helps isolate them from such noise.

 

Second, the circuitry is engineered to minimize electronic noise, which is like the hiss one hears when turning up a stereo system with no sound coming from it. “That hiss can also mask leak noise,” France said.



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