Checking the Health of Your Pipes -What You Need to Know
Every four years, the American Society of Civil Engineers (ASCE) issues a Report Card for America’s Infrastructure, which depicts the condition and performance of American infrastructure in the familiar form of a school report card. For the first time this century, the overall cumulative grade from the 2021 report was out of the D range and scored a C-. While an optimist can see this as an improvement, we still have a long way to go.
Asset management remains one of the most critical tasks as cited by ASCE’s Report Card as it aims to prioritize limited funding that falls well short of what is needed to maintain our infrastructure.
Sectors like water and wastewater have staggering maintenance deficits, so until funding meets the needs of the demand, activities like asset management and condition assessment are paramount to help bridge the gap.
One of the most neglected areas of focus is the elaborate networks of underground piping and appurtenances that make up our water distribution and wastewater collection systems. These pipelines are essential to our everyday lives and while avoiding catastrophic failure is the goal to maintain a minimum level of service, it is wishful thinking without a holistic approach to determining the health of your system.
Think of a pipeline health check compared to your personal wellness exams. If we do it on a regular, routine basis, then we maximize our chances of avoiding catastrophic failure. Most people pay attention to their visible ailments, but what about the out-of-sight, out-of-mind problems that progressively deteriorate over time? Much like a doctor who follows a checklist of the most known causes of death, an effective pipeline health check hinges on understanding how a system operates and the potential modes of failure. Obviously, different types of pipelines will fail in different ways. Let’s consider sanitary sewer force mains for the purposes of this pipeline health check.
Based on a survey of Water Environment Research Foundation (WERF) and the National Association of Clean Water Agencies (NACWA) utility subscribers, nearly 50 percent of force main failures are due to corrosion, either internal or external. An additional 25 percent of failures are attributed to surge pressure and joint leakage. This means more than 70 percent of force main failures are preventable with a comprehensive management program.
An effective pipeline health management protocol is based on a prescriptive, phased approach to condition assessment. This is accomplished with a thorough review of the pipeline’s history, operating parameters, and in-situ conditions. Identifying known failures, such as overflows, leaks, or breaks and maintenance history learned through staff interviews is an important first step.
Once this information is gathered and analyzed, field reconnaissance is a necessary second step to verify pipeline conditions and look for obvious signs of degradation. Conducting this preliminary pipeline alignment walk will save time and cost by identifying conditions that may be impacting the integrity of a pipeline — issues causing pipe leakage, failure, or interruption of service — prior to selecting a technology for internal or more invasive inspections. Once the pipe walk has been completed, it’s time to start planning for the application of field operational verification tools, such as high-frequency transient pressure monitoring and C-factor testing. These tools provide insight into the actual operational functionality and hydraulic efficiency of the force main.
As corrosion is the leading cause of failure of force mains, it is most often the highest priority symptom to identify, both internally and externally. A “typical” corrosion evaluation includes a comprehensive evaluation of a pipeline to determine how corrosive the environment is, and what corrosion control methods can be selected, designed and implemented. The next step in the pipeline health check process is to conduct an initial soil and groundwater analysis along the pipeline that provides information to determine if external conditions are impacting the life of the pipeline. By analyzing these factors, appropriate additional assessment technologies, internally and externally, can then be determined.
Condition assessment technologies play a crucial role in your pipeline health check and should be considered only after all steps in the pre-screening process and external corrosion evaluation have been completed. In many cases, a good initial screening tool is a free-flowing sphere (Pipers, Nautilus, SmartBall, Navigator, or equivalent) for internal gas pockets, pressure measurement, debris and blockage locating, mapping, and metallic profile changes. This type of technology is considered “noninvasive” meaning that it is performed while the pipeline is in service, although it might require a tap or support from operations for insertion or extraction of the tool, depending on the pipeline configuration.
More invasive advanced tools using electromagnetic or ultrasonic sensors will yield high-resolution results but come at a higher cost. These types of technologies can be used both internally and externally, but each comes with their own unique challenges for implementation. For external assessment, using broadband electromagnetics (BEM) or ultrasonic bracelets, the pipeline must be exposed, and more exposure yields better results from a statistical sampling standpoint. For internal assessment, a pigging station or large valves or similar access points might be required to introduce the tool into the system. Both internal and external technologies should be considered if the force main operation affords it. For example, if the pipeline has no redundancy and cannot be taken out of operation, then perhaps only external technologies and “noninvasive” internal technologies can be deployed. Deployment of different technologies comes at a cost and the selection of a particular technology should be weighed against the value of actionable information gained from the inspection. There is no “one size fits all” when it comes to sewer force main assessment but by understanding the capabilities of innovative sensors and technologies in the market, engineers and owners can ensure the longevity and reliability of sewer force mains.
Once you have conducted your first pipeline health check, it will serve as your baseline for comparison over time. Long-term inspection data allows owners and engineers to determine the remaining useful life (RUL) and forecast issues before they happen. Successive pipeline health checks allow you to identify any sudden changes in condition and pinpoint locations most at risk of failure. A baseline inspection also ensures that funds are not being “wasted” on rehabilitating pipes that are considered healthy, maintaining your system health with the most efficient use of limited budgets.
