The water pipeline infrastructure in North America was built over a period of several decades. As such, it is not expected to fail all at once. However, as the years go by, municipal leaders are increasingly engaged in deliberations concerning its sustainability.
The goal is to establish a manageable program, in terms of affordability and ease of implementation, to aid in the renewal of water and wastewater systems ? a condition assessment program. Since the pipeline investment price tag is already estimated at half a trillion dollars in the United States over the next 20 years, it is critical to maximize the impact of each dollar spent and replace only what is necessary before failure. The results from a condition assessment program will offer the ability to stretch the massive infrastructure investment over a longer period, buying valuable time to effectively fund the mega project.
?Utilities typically have an annual budget line item for repairs and rehabilitation. The challenge is that this funding alone will be inadequate to deal with the issue as a whole.? A new approach needs to be adopted,? said Gregory Baird, Chief Financial Officer of Aurora Water in Colorado. ?Knowing the actual condition of an existing pipeline asset creates a low-cost, win-win scenario for utilities.?
An increasing number of utilities are turning to companies such as the Pressure Pipe Inspection Company (PPIC) to conduct condition assessments of existing prestressed concrete cylinder pipe (PCCP) transmission mains prior to repairing or replacing them. ?Just because a water pipeline asset has reached its operating life on paper, doesn?t mean that it automatically needs to be replaced,? said Dr. Brian Mergelas, President and CEO, PPIC. ?Our 14 years of inspection experience have shown a critical statistic that all municipal utilities should know about: on average only 4 percent of PCCP pipes had high levels of distress, which means that 96 percent are still in working condition.?
Armed with this information, it becomes much easier for utilities to extend the life of underground assets by prioritizing repair and replacement programs based on actual asset condition. This it is the cornerstone for bridging the gap between pipeline investment and risk reduction. ?
Condition Assessment Technology
Remote Field Transformer Coupling (RFTC) technology has become the standard for assessing the condition of large diameter PCCP pipe. The technology provides pipeline owners with information on the location and number of wire breaks within individual lengths of pipe, identifying structurally weak areas.
RFTC technology functions much in the same way as a radio transmitter and receiver. The transmitter produces an electromagnetic field. The prestressing wires in the pipe amplify the signal that is recorded by the receiver. If there are broken wires, the signal is distorted. A measurement of the distortion quantifies the number of broken wires and pipe integrity can be calculated.
?If a pipe that still has some useful life is replaced, money has been wasted. If a pipe is replaced too late and fails, then the emergency repair cost may actually be double. The true need is to find the sweet spot where the capital investment actually reduces the risk and limited capital is allocated efficiently,? Baird said.
Knowing the number and location of distressed wires within a line and what actions to take based on this information can offer a significant capital savings for utilities.
When officials at the City of El Paso, Texas, were concerned about the condition of a 24-inch water main which experienced a rupture, they turned to RFTC technology from PPIC. The inspection found the main to be in good condition. As a result, the utility simply replaced the section of damaged pipe and avoided replacing the entire line, an estimated cost savings of more than $3 million. The cost of the condition assessment was approximately 2.5 percent of the realized savings.
Depending on the needs of the inspection, several different configurations of RFTC technology are available, including robotic and manned systems. Anywhere from 1 to 10 miles of pipe can be inspected per day, depending on the RFTC tool configuration. Transmission mains typically need to be depressurized and either partially or fully dewatered.
Manned and robotic RFTC tools have been used in hundreds of inspections throughout the world with great? success. The tools are ideal for emergency inspections once a failure has occurred or for inspecting short to medium distances. The challenges were that many utilities found it difficult to dewater their lines due to cost or permits and that critical feeder lines often had no redundancy, which meant that the lines count not be taken out of service.
To overcome these challenges, PPIC developed a free-swimming RFTC tool called PipeDiver. The tool was designed to work within operating water mains with a diameter of 24 inches or greater.
The tool can be inserted into a live pipeline via a hot tap connection and insertion sleeve, an existing access or a submerged tank. Once inside the line, it will travel with the flow of the water until it reaches a predetermined extraction point. Tool movement and distance-traveled are tracked from above-ground check points.
Added Benefits
Having overcome previous key barriers of large-diameter water main inspections, PipeDiver offers several unique benefits:
??? ?Lower overall inspection cost ? The major hard costs of dewatering and multiple line modifications to add inspection access points have been eliminated.? The soft cost of community PR must also be taken into account as there is no service interruption and fewer crews working neighborhood streets. ?
??? ?Longer inspection distances ? In the Western portion of the country, long distance transmission mains can now be inspected more often with much greater ease. In the Eastern portion, the tool provides a method for a proactive system-wide assessment approach. In either scenario, the linear foot cost of inspection will be dramatically lower.
??? ?Inspection of non-redundant lines ? Traditionally these lines have been very challenging to inspect as service could not be interrupted long enough to allow for a manned or robotic inspection. PipeDiver can be used to develop a predictable and repeatable inspection program as the line remains in service, helping to ensure the uptime of these critical lines. The risks associated with recharging a critical line are also eliminated.
??? ?Simplified re-inspection process ? Once hot taps are installed, the line can easily be re-inspected at any point in time; there is no need to wait for scheduled maintenance outages. By having multiple points of data over time from a single line, it becomes easier to recognize and track subtle baseline changes that can be acted upon through a predictable rehabilitation program.
?The tool?s benefits are music to the ears of a utility,? says Brian Mergelas, PPIC president and CEO. ?If they are facing a $10 million replacement cost for a section of pipeline, PPIC can do the condition assessment and enable the selected repair of the damaged pipe section for typically 10-12 percent of that replacement cost.?
Working with the Data
Upon completion of an inspection, the data is immediately downloaded and its integrity is validated. On-site analysis is also possible; however the typical PPIC process involves off-site analysis by two highly trained electromagnetic experts (primary analysis and secondary verification). The inspection data is correlated to the pipeline drawings and special attention is paid to any areas that display distress. The distress signals are matched to an extensive signal library to help ensure the highest degree of report accuracy. ?
End users receive a detailed report summarizing the condition of the pipeline ? which pipes have wire distress, the location of the distress and an estimate of how many wires are affected. A detailed pipeline asset list is also provided, which presents the condition of each individual pipe inspected. This list is often of high value to the pipeline operator as any variations from the drawings, such as the number of pipes, type of pipe and location, can be identified.
Once the pipeline owner has the inspection report, there are typically four paths of action which can be taken:
- No immediate action ? If the inspection data shows minimal distress, then additional action may not be required in the near future. However, based on the importance of the line, a plan should be set for re-inspection, as actual distress levels found by individual pipe length can change over time.
- Internal engineering ? If a budget is in place, and only a small number of pipe segments need immediate attention, then an internal repair or replacement strategy may be adequate. However, if there a higher percentage of pipes need attention, simply replacing or repairing pipe segments based on a minimum threshold of wire breaks may not be the most economic approach to truly reduce risk.
- External failure risk analysis services ? When working with a limited budget and a high number of distressed pipes, the services of a specialty engineering company with extensive risk analysis experience, such as Simpson Gumpertz & Heger (SGH), may offer the best value. Based on proven models and real-life situations, a priority list for repair and replacement can be developed based on the location and configuration of the distress, operating conditions and pipe class.
- Strategic monitoring ? Once baseline inspection data has been established, strategic monitoring devices, such as acoustic emissions testing, can be used to evaluate if there is any ongoing distress within a higher risk portion of the pipeline. These devices are simple to install and can be used for short or medium term monitoring.
Based on the inspection data from the RFTC report, these common paths will help pipeline operators to avoid replacing pipes that still have a useful life while allowing for critical budget dollars to be extended by finding and focusing on higher distressed areas of the line.
Project Examples
Halifax Water, the municipal water utility for the Halifax Regional Municipality in Nova Scotia, provides utility services to about 325,000 residents. When a section of a 30-inch diameter PCCP pipeline was identified by the utility as being high-risk due to its age and proximity to a major highway and residential area, the utility turned to RFTC technology. It would have been difficult to remove the line from service, so Halifax Water selected PipeDiver to conduct the inspection without dewatering or service shutdown.
A total of 97 pipe lengths were inspected, and analysis of the data obtained during the inspection determined that only 11 pipes displayed evidence of distress. The majority of pipes within the line were proven to be in good condition and did not require immediate replacement. ?
More recently, a similar inspection was performed in Dallas County Park Cities Municipal Utility District (DCPCMUD) in Texas. Established in 1938, DCPCMUD is located near Dallas Love Field Airport and serves the Town of Highland Park and the City of University Park. These two communities are completely surrounded by the City of Dallas and combined have a population of approximately 33,000.
The district operates a 36-inch PCCP line stretching almost 4 miles that has been in service since 1948. The line is a critical asset for DCPCMUD as it is the only water transmission line for the surrounding communities.
The district turned to PipeDiver as the line could not be removed from service. The free-swimming tool traveled under major roadways, through several 45 and 90 degree bends and ultimately inspected nearly 1,100 pipe segments prior to being removed from the line. Data analysis showed a very low distress rate and the findings were used to help value the asset for an upcoming bond issue. ?
An inspection of note occurred late last year when PipeDiver set a new distance record of over 22 miles during the inspection of a 99-inch diameter PCCP water transmission main in central Mexico. This milestone inspection represented the longest distance travelled by an RFTC based system while the water main remained in service.
What the Future Holds
PipeDiver was designed as a platform technology, meaning that the intention was to develop a tool that could carry multiple sensors and tools capable of providing a variety of information about the condition of a pipeline.? The current capability is the RFTC technology that can be used for PCCP pipelines.? PPIC actively pursues partnerships with government agencies, utilities, technology companies and universities to develop new tool attachments for the platform. Several additional features are currently in various phases of development. These include:
- Sensors to establish the wall thickness and remaining life of metallic pipelines.
- Video and photo capability from multiple angles. (This could be used to determine the condition of inner mortar coatings of lined steel pipe.)
- Detection of voids on the outside of pipelines to help reduce the risk of sinkholes.
- Leak detection modules to help reduce water loss and meet sustainability objectives.
Conclusion
There is no doubt that the challenges presented by aging water and wastewater pipelines will only increase with time. Using traditional methods of simply repairing or replacing pipelines based on their design life will not be sufficient to get ahead of the problem. Condition assessment technologies have been in use for well over a decade and are proven for a variety of applications.? New advances, such as PipeDiver, are removing traditional barriers to inspection while simplifying the process and reducing overall project costs. By understanding the true condition of their pipeline assets, utilities can better prioritize repair and replacement projects and maximize the impact of each budget dollar.
Mike Stadnyckyj is the Director of Strategic Marketing for PPIC and has over a decade of experience in the water industry. Specializing in product commercialization and management, Stadnyckyj has worked with a variety of advanced technologies for desalination, filtration, water reuse, supply security and distribution. For more information, contact mike.stadnyckyj@ppic.com.
