Condition Assessment Using Transient Waves

Heightened Visibility:

Condition Assessment Using Transient Waves Gives Added Value to Pipeline Asset Management

By Andrew Farr

The report card on America’s infrastructure is out and the grades are not good.

In March, the American Society of Civil Engineers (ASCE) released its 2017 Report Card for America’s Infrastructure, giving a cumulative D+ grade to U.S. infrastructure. As expected, the condition of the nation’s water and sewer systems showed little improvement over ASCE’s previous report card in 2013, this time giving a D to drinking water and a D+ to wastewater.

For water and wastewater utilities, obtaining accurate information about your system allows for better decision making. Based on findings in the report card, this is one area that underground infrastructure in the United States can benefit greatly from in the near future. According to the report card, both the drinking water and wastewater sectors need $150 billion between now and 2025. With only $45 billion likely being available in that time, the report card suggests a $105 billion investment shortfall in just the next eight years.

Considering the urgency of these challenges, utilities will continue to stretch the resources they have in order to maximize efficiencies. One of the first steps for utilities to manage their underground assets is to have a proactive pipeline condition assessment program, which can help utilities prioritize pipeline rehabilitation and replacement. The end result is the realization of savings in money, time and disruption to customers.

A technology that has been established in Australia for more than a decade, which recently became available in the United States, is gaining traction as an effective method of testing long stretches of water and wastewater mains. It involves no disruption to service and delivers high-resolution, accurate pipeline condition assessment data.

Several pilot projects are currently underway employing Hydromax USA’s Pipeline Condition Assessment Technology (p-CAT). The p-CAT was introduced to the U.S. market last year when Hydromax entered into an exclusive licensing agreement to deliver the pipeline inspection services to the water and sewer industries in the United States and Canada. It was developed after more than 17 years of research by the University of Adelaide in Australia and has been commercialized and used throughout Australia, New Zealand by Detection Services, a pipeline condition assessment services company. The system has now been used on more than 500 miles of pipeline in Australia, New Zealand and Pacific markets for the past decade before Hydromax worked to bring the technology to the U.S. market in 2016.

Pressure Wave

As the pressure wave travels through the pipe, it creates reflections which are then analyzed to 30-ft visibility to measure the sizes and locations of pipeline defects.

How It Works

The p-CAT is a pipe screening tool that can quickly test miles of pipeline to identify small, localized hot spots. The technology uses a unique patented technique of inverse transient analysis to measure and determine the internal and external condition of pipelines, as opposed to acoustic technology that measures the time delay of the sound between two sensors.

The p-CAT is implemented by introducing a controlled transient pressure wave, typically between 3 and 5 psi, into the pipeline by a transient generating station. Sensors are spaced about a half-mile (or more) on both sides of the generating station, resulting in tests that can be conducted in lengths from one to many miles long depending on pipe conditions. As the pressure wave travels through the pipe, it creates reflections which are then analyzed to 30-ft visibility to measure the remaining wall thickness, sizes and locations of pipeline defects including corrosion and cement mortar lining spalling, material changes, leak locations, air pockets, the sealing status of valves and cross connections.

As the pressure wave travels through the pipe, it creates reflections which are then analyzed to 30-ft visibility to measure the sizes and locations of pipeline defects.

The system allows for about one to four miles of pipe to be tested in a day. One of the primary benefits to the p-CAT is that it is a non-invasive, non-destructive system that can be implemented without taking the line out of service. Paul Schumi, business development manager at Hydromax USA, says another advantage is that it also leverages existing infrastructure to complete the test.

“Not only are you getting a substantially more granular look at the pipe, but when you deploy p-CAT, because your sensor spacing is about a mile in length, oftentimes you can use existing appurtenances, such as hydrants or air valves,” says Schumi. “You often don’t have to modify the structure in any way. It’s truly non-invasive because of the length that we can achieve.”

p-CAT can be used on all metallic pipe, all non-reinforced concrete pipe and asbestos cement pipe for both water and sewer systems. It has not yet been trialed on reinforced concrete pipe because those pipe materials are not used in Australia. However, those trials are currently in the works by Hydromax in the United States.

p-CAT can be also used on force mains assuming pressure conditions are appropriate. Because it’s a pressure-based tool, it requires system pressures to be above 30 psi. While this is not a problem for water systems, it does require sewer system curves to support the pressure requirements over the full length of the pipe. To help achieve this in some cases, a utility may elect to charge the main in order to generate the required pressure for the test. “It’s the only non-invasive technology that can test a force main under pressure and deliver high resolution condition data without taking the line out of service,” says Schumi.

In the Field

Hydromax is trialing the p-CAT in multiple pilot projects in the United States. Projects are underway with the City of Columbus, Ohio, the Florida Keys and City of Jacksonville, Fla., which are using the p-CAT to reassess the condition of their pipelines, serving as an introduction for the p-CAT to the U.S. market.

In the Florida Keys, the Florida Keys Aqueduct Authority is driving condition assessment on a large water transmission main that transports water 120 miles from the water plant southwest to Key West. The authority, which has already done some condition assessment work with other technologies, will reassess sections of the pipeline using p-CAT in the coming months.

“We’re looking at one section of pipe on Grassy Key that has failed multiple times – twice in the last year – and we want to use [p-CAT] to see if we can come up with a repair plan,” says Walt Schwarz, regional technology lead for condition assessment and rehabilitation services for CH2M, which is serving as a consultant for the Florida Keys Aqueduct Authority condition assessment program.

Schwarz says the utility finds value in proactive condition assessment, particularly when it comes to having options regarding pipe rehabilitation and replacement, noting the p-CAT’s apparent accuracy for providing that insight.

“We don’t want to replace 400 ft of pipe if there’s only 40 ft that’s bad,” he says. “The predictive resolution of p-CAT is [better]. Replacing 40 ft of pipe is a doable thing without creating a multi-million-dollar project.”

Schwarz also says an advantage to p-CAT is prioritizing repair, especially when it is discovered that replacement may not be necessary. “It means we can go right to repair,” he continues. “Without taking the pipe out of service, we can do something we never could before. These technologies are growing all the time and this is a missing link.”

Pipe Condition

By locating the exact points at which the deterioration occurs, replacement and reparations of pipelines can be limited to only those sections in need of attention.

Analysis & Accuracy

According to Shane Majetich, manager of national water distribution services for Hydromax, the primary benefit of the p-CAT is visibility. He reiterates Schwarz’s view that the technology has its benefits when compared to acoustic technology, for example. “What you achieve with transient waves is about 15 times greater visibility to the pipe infrastructure than you can through acoustic methods,” he says.

He also adds that p-CAT data separates information it collects about pipe materials and diameter changes so that it doesn’t skew results about pipe integrity.

“If you don’t know a [pipe] material has changed along the pipe length, with pressure technology, it can actually identify those changes as part of the readings because of the reflections,” Majetich says. “If you have a length of PVC repair mid-test, we can identify that it exists and isolate it out from the test results. Same with diameter changes. The unknowns are actually identified in the field through the pressure test results, so it allows for a substantial increase in accuracy.”

Ultimately, p-CAT provides accuracy. One of the reasons it is unique is because condition assessment technology often averages test results over a length of pipe, which doesn’t necessarily pin down the specific location of a high priority area.

“Averaging technology averages out severe, singular points of failure, masking those into a single measurement of percentage of degradation for that test length of pipe,” Majetich says. “The p-CAT is able to identify those singular points of failure along the pipe.”

The Potential

Majetich says granular visibility at a low cost is one of the big takeaways he sees with p-CAT and that the system ultimately allows the technology to be more closely linked to decision making ability.

“The p-CAT, to me, fits a very strong middle-of-the-road solution in that – at a similar economic cost to the utility as acoustic solutions – you can gain substantially more granular visibility and lower your footprint for future activities, such as repair or rehabilitation solutions or moving to invasive [condition assessment] solutions to find out more,” he says.

Majetich also adds that different condition assessment technology coming into the market is beneficial in different ways and that competition is valuable to the end-user. Although options exist for utilities to implement technology based on their individual challenges, it’s always dependent on what’s financially feasible.

“At the end of the day, the primary resource is the financial one that every utility is struggling to manage, and that dictates a lot of what the utility can do in terms of asset management strategies,” he says, adding that the p-CAT simply offers another tool for the toolbox for condition assessment that offers accuracy and an alternative to invasive options.

“It’s really all about balancing their needs with a budget-friendly solution,” he says. “The data itself – degradation, material changes, pipe diameter changes, air pockets, enclosed valves – all of that data can drive different types of decisions for the utility once they have it at their fingertips. The more tools the industry brings to bear, the more tools clients have to investigate their system.”

Andrew Farr is the associate editor of Water Finance & Management.

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