Resource Drain

April 2, 2018

About the author: Luis Mijares is water services development manager for ADS Environmental Services, a Div. of ADS LLC. Mijares can be reached at [email protected] or 256.430.6494.

Utility and distribution managers: Do you feel like you are getting squeezed in the middle of the cost-reduction-and-improved-results vise? You are not alone. Most utilities face increasing pressures in this tough economic environment to maintain or improve their service levels while reducing operating costs.

Reducing water loss is a key area of focus for utilities. Now, more than ever, accounting for all treated water put into a distribution system is critical, particularly in areas where access to water sources is becoming increasingly difficult. There are parts of the country, like the South, that are in severe drought conditions. Limited source water availability is putting pressures on utilities for improved water loss control. Adding to this pressure, managers also are faced with the loss of older, experienced personnel through retirement.

Leak detection, once known as more of an art than a science, is suffering from this drain on experienced resources—and all while the need for leak detection is increasing. The loss of experienced personnel has put some leak detection programs on the back burner or is causing them to be outsourced because of the lack of available trained personnel.

Technology Evolution

Fortunately, some manufacturers of leak detection and correlation equipment have realized the need to simplify the user interface of their products so that “part-time” and newly anointed leak detection specialists can be productive as they ramp up on the training curve. The advent of better, smaller, more powerful and power-efficient microprocessors and signal processing components has allowed for equipment that is easier to use and better at finding leaks than equipment manufactured three to five or more years ago.

Look at how far electronics have evolved in the last few years in general. iPhones were introduced in 2007 and iPads in 2010, and these amazingly powerful devices are affordable and can run for days without recharging. The same is true for the components that power leak sounders and correlators. Modern leak detection and correlation devices not only offer better, more efficient and more affordable technology, but they are easier to use and are designed for personnel that are not devoted to the job full time or have little previous experience using them. These devices have evolved the way of digital cameras. Today one can buy a digital camera at a reasonable price, take it out of the box, give it a charge and start taking good pictures. As time goes by and the user gets more familiar with the camera, he or she can take it off the automatic setting and start taking even better pictures with a few minor settings adjustments.

Two of the water-loss control products offered by ADS LLC provide this same train-as-you-go experience: the Mikron and the Eureka 2R. They offer technological advances with reduced skill level requirements and complete a leak detection toolkit, with a sounder, correlator and ground microphone.

Acoustic Probes

The Mikron Alpha is a leak sounder with an amplified acoustic probe. There is a highly sensitive transducer (vibration microphone) that is connected to a hand-held rechargeable amplifier. The probe “listens” for noise that is being transmitted down the pipe by the energy of water leaking or leaving the pipe. The amplifier then takes this noise and filters it to ferret out the useful pieces of information and relays the result to the user in an easy-to-understand manner via both headphones and a visual display. These units have simple selectable filters that allow the circuitry to listen only for noise in the frequency range related to the subject pipe and to eliminate ambient noises outside of that range. This range corresponds to the expected frequency of a leak noise on a pipe of a certain material and diameter.

Most new leak detection equipment users do not have the experience to distinguish the level and pitch of the audible noise as a potential leak source, so some devices on the market have a visual display that gives a digital numerical value for the strength of the minimum noise level, or constant noise, created by the leak. At the push of a button, the measured value is stored for reference as the operator moves to the next listening site to see if the noise is getting stronger or weaker in order to determine the approximate location of the noise source. Once the operator determines a source of constant noise in the suspect frequency range, a correlator can be deployed to find the exact location of the noise for repair.

Acoustic Leak Correlators

Acoustic leak correlators are also listening devices that work like the acoustic probe described above. Correlators have two or more acoustic transducers that are connected to the hand-held processor via radio transmitters. The transducers are deployed on fixtures connected to the pipe (e.g., hydrants, valves, service connections, etc.). They usually contain a magnetic pickup so that they can be attached to the metal fixtures on the surface. The signals from the transducers are relayed to the correlator electronics via the radios.

By answering a few simple questions on pipe material, diameter and length between the transducers, the correlator finds the location of the noise source. The pipe material and diameter set the internal noise filters for the correct frequency range to look in on the expected velocity of sound through the pipe wall.

The length of the survey is used to match or correlate the two noise signals from the time shift of the noise signature.

Here again some manufacturers have taken the complexity out of the process so that operators with very little training can pick up a correlator and use it with minimal training. The Eureka 2R has two listening stations (blue and red) that are deployed to bracket the potential leak noise found previously by the acoustic probe. When the transducers are plugged into the radios, the radios turn on automatically. There is only one user-selectable setting (via a button on the radio) that is required: the high/low power output for the radios. If the radios are less than 60 ft apart, a user selects the low output; otherwise, the high setting should be used.

As the transducers are deployed, the operator measures the distance between them (following the path of the underground pipe) using a measuring wheel. When the hand-held unit is powered up, it begins correlating. If a peak indicating a noise source develops on the display, then the user can choose the “Pipe Details” button. This will prompt the user to enter the survey length and select the pipe material and diameter from drop-down menus. The unit then correlates with the data supplied.

The correlator will listen for a few minutes to determine where the noise source is located. It will then display the noise source on the LCD screen as a peak and show the operator how many feet away it is located from the blue and red listening stations. The operator then can measure the distance to the potential leak noise source and check again for services that may be active or a partially open valve in the line that could be creating the noise. If none of these are present, then a final check should be made using a ground microphone.

This check is to verify the potential noise source before digging and to get closer to the source in order to minimize the size of the repair hole. The Mikron Gamma ground microphone uses the same hand-held amplifier as the Alpha, with a different listening transducer that is optimized for ground use and shielded from wind and traffic noise.

With Challenge Comes Opportunity

The good news in this challenging economic environment is that the technology now exists to utilize current personnel and, with minimal investment in hardware, develop them to be functional leak detection personnel to help lower costs and recover lost water.

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About the Author

Luis Mijares