Leak Detection – The Right Tools for the Job

“Heat Pops Pipes Nationwide — Brace for Higher Bills” warns a mid-August front-page headline on CNN.com.

The report reveals that this summer’s record heat wave has also been causing a record-breaking number of utility-crippling water pipeline leaks and breaks across the United States. Water utilities in California, Kansas, Oklahoma, Texas, Indiana, Kentucky and New York, have been plagued by hundreds of pipeline breaks, interrupting water service to thousands of customers and drawing media attention to the large number of pipeline leaks in a time of severe drought.

However, water pipeline leak detection and condition assessment experts say that blame lays with the unusually high temperatures drying and moving the soil around the aging water pipes for the unusual increase in breaks — not with the utilities.

“A severe drought can be damaging to water pipelines in the same way that a severe freeze can be,” says Cliff Jones, vice president of business development with Wachs Water Services. Jones says soil surrounding buried water pipelines dries and shrinks in the summer or freezes and expands in the winter, causing the pipes to move and spring leaks at pipe joints. If the pipe is older or in a delicate condition, increased water usage in the summer can add additional pressure, making them even more susceptible to leaks or failures.

An Oklahoma water utility reported 685 water main breaks since the month of July, almost four times the normal amount. With field crews working around-the-clock to find leaks and replace pipes, some utilities are finding it difficult to perform planned asset renewal projects.

“Utilities constantly reacting to pipeline leaks and breaks are realizing that they really need to be pursuing a preventative and proactive program of leak detection and condition assessment,” says Jones. “Proactive detection means using the right tool at the right time, rather than relying on a single-solution approach — and in most situations the first leak detection tool we deploy are the good old correlators.”

Good Old Correlators

“Correlators are the absolute best way to get a quick snapshot of the condition of your pipes and discover where your ‘problem pipes’ are located,” says Henry Scott, a leak noise correlation expert with Wachs Water Services. Used in conjunction with specialized listening devices placed upstream and downstream from a suspected leak, correlators measure the time delay of a leak noise arriving at either noise-logger location, then calculate the difference in sound arrival times to pinpoint the precise noise location.

Scott says the most cost-effective method for performing “broad-brush” leak assessment of large areas of pipeline is to first deploy listening equipment to targeted sections of pipeline, document everywhere that leak noises are detected, then go back and correlate only those pipeline sections exhibiting leak noises to pinpoint the location where the sound of the leaks are being generated. With the hundreds of pipeline leaks generated by the hot summer weather across the country, correlator-equipped leak detection crews have been in high demand.

We’ve doubled the amount of our leak detection work we did last year,” says Scott. “In the Northeast alone, we have done detection surveys of several hundred miles of pipeline for utilities in New Hampshire, Massachusetts and Virginia. In one instance, we discovered a leak for about every six to eight miles of pipeline we surveyed — and this leak ratio can significantly increase in a drought or following rapid freeze-thaw conditions.”

Correlators are considered the best “bang-for-the-buck” leak detection solution, but their effectiveness can suffer when dealing with PVC pipe, multiple-leak situations and when assessing large-diameter mains. “No single tool by itself is going to get the job done,” says Scott. “When solving tough problems or working with big pipes, we bring in our heavy artillery: the in-line leak detection systems that enable us to actually view what’s going on inside the pipe in real-time.”

Find a Leak and Visually Confirm the Source

In-line leak detection tools equipped with ultra sophisticated listening devices and CCTV cameras travel inside a water pipeline, accurately detecting and locating all leaks and providing the operator with a comprehensive picture of the pipe’s interior condition — without taking the pipeline out of service. Purpose-built for visually inspecting pipe interior surfaces, in-line condition assessment tools enable utilities to pinpoint hard-to-find leaks, spot severe corrosion and potential points of failure, observe dynamic pipe operating conditions and characteristics, and verify the internal condition of joints, liners, valves, and other pipeline assets. Though correlators and other passive leak detection systems are effective in common situations, advanced in-line leak detection tools help utilities confirm those leaks before embarking on costly excavations of buried pipeline assets or roadway surfaces.

“There have been many documented examples of utilities using passive leak detection systems excavating down to repair pipes that actually have no leaks,” says Jones, who says digging dry holes is far more costly and time-consuming than deploying today’s next-generation in-line inspection tools. Wachs Water Services deploys two types of in-line inspection tools combining leak detection and video inspection capabilities, both designed for direct insertion into different sizes and types of in-service pipelines, and both capable of operating under a wide variety of flow conditions.

For example, the Investigator is designed to inspect pipes sized 3 to 12 in. can be launched into a water main through fire hydrants, pressure fittings, air valves, gate valves, and flow meter fittings and is capable of traveling up to 300 ft in either direction from the insertion point, depending pipeline tuberculation and number of bends in the pipe. The LDS1000 is designed for inspecting large-diameter transmission mains and combines ultra-high response hydrophone sensors with CCTV technology into a single, small sensor head that can be deployed more than 3,000 ft.

Valve Operability Is the Key to Program Efficiency

When utilities deploy in-line inspection tools to verify leaks and assess the condition of their pipes, they also get valuable opportunity to check the operational condition of an even more critical water distribution asset — their valve control points. “Ideally, a broken pipe can be shut down by closing just two or three nearby valves, but too often we see water distribution systems with so many broken or inoperable valves that as many as 13 valves must be closed before crews can fix a broken pipe in an emergency,” says Jones. “Utilities can achieve a high degree of valve operability through proactive pipe and valve condition assessment, avoiding problems that might otherwise deprive people of water during a drought.”

There is no such thing as a “zero-leak” system, warns Jones, also stressing that “finding the leaks is one thing — but the important thing is fixing them.”

Combating water loss has become a top priority for all water utilities today, but their other top priority is controlling infrastructure repair costs. Advanced leak detection and asset condition assessment technologies are helping utilities renew their aging infrastructure by enabling them to cost-effectively determine the condition of their aging water transmission systems and save money by selectively rehabilitating only those pipe sections with compromised structural or mechanical integrity.

“Utilities need to know what they have in the ground, they need to know exactly where their vital assets are located, and they need to know what works and what doesn’t,” says Jones. “A proactive system assessment enables doing proactive repairs and rehabilitation, and significantly minimizes the impact of pipeline leaks — especially important in times of water scarcity.”

David Stewart Jones is a freelance writer and researcher, based in Toronto, Canada.

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