In North America, the material and size of pipes that make up water and sewer networks range widely. Because these pipeline systems are so complex, it requires a strategic approach based on risk and real data for effective long-term management.
Historically, however, it has been challenging to gather real data that can shape defensive capital decisions for an entire system. The assessment of metallic pipelines — which make up most water and pressurized sewer networks — differs from prestressed concrete cylinder pipes (PCCP), both in terms of failure modes and in the fact that metallic pipe materials are featured in both transmission and distribution networks.
While PCCP assessment and management have been successfully used by utilities for years, effective assessment solutions for ferrous pipe have only recently been commercialized.
In 2011, Pure Technologies began an initiative to help close the gap in metallic pipe assessment technologies, and focus attention on gathering honest feedback from proactive utilities on what solutions are needed to effectively manage metallic pipe.
Seven years later, Pure Technologies reports that notable progress has been made with the development and advancement of assessment technologies for metallic pipeline networks.
Proactive utilities have been involved in the metallic pipe initiative, and instrumental in the development of new inspection tools for metallic pipe, both by providing feedback that helps guide research and development, and by providing opportunities that allow solution testing in live operating conditions. As a result of these efforts, there has been significant improvements to the technologies available to utilities for assessing the condition of metallic pipelines in both transmission and distribution networks.
For large-diameter transmission mains, there is a well-developed business case for assessing these mains as they approach the end of their useful life. These pipelines typically carry a high replacement cost and are higher risk — due primarily to their size and criticality — making it important for utilities to fully understand the condition of the asset.
Armed with real condition data, utilities can make a defensible renewal or replacement decision about the pipeline. Based on well over 14,000 miles of data, Pure Technologies has found that only a small percentage of pipes are in need of immediate renewal.
In distribution networks, however, the case for condition assessment is more challenging as smaller pipelines can sometimes be replaced cost-effectively. Despite this, the process for making a replacement decision should be based, whenever possible, on risk and real data.
With the EPA suggesting that between 70 and 90 percent of pipes being replaced have remaining useful life, the case is even stronger for collecting condition data to drive the decision making to help utilities spend their replacement dollars more efficiently and avoid replacing pipe with remaining useful life.
In some instances with smaller diameter pipes, it is often cost-efficient to use inline tools to gather detailed screening data on a pipe-by-pipe basis to determine if replacement is necessary.
While there is no silver bullet technology for assessing metallic pipelines, Pure has developed a flexible, risk-based approach to help utilities better understand their infrastructure, gather actionable data and prioritize both short and long-term management efforts.
Over the past few years, Pure has worked along proactive utilities to develop its data-driven Assess and Address® approach, which focuses on four main areas:
Through the implementation of programs across North America, Pure has found that the majority of pipelines 16 inches and above can be cost-effectively managed for between 5 and 15 percent of the replacement cost.
The first step of any pipeline management program is understanding the system-wide risk along with the benefits and limitations of assessment solutions. This allows for the development of a defensible management strategy that can be implemented to maintain and extend the life of the assets.
Many technologies now exist to provide a snapshot of a pipeline condition at various levels of confidence. It is therefore prudent for utilities to approach technology selection and subsequent analysis based on the risk of each pipeline.
A more thorough risk assessment involves estimating the Consequence of Failure (CoF) and the Likelihood of Failure (Lof) of each pipeline based on internal knowledge, operational history and pipeline characteristics. This initial risk assessment determines which areas of the system require further assessment to acquire real condition data and provides the utility with the necessary information to make an informed technology selection.
By using risk to guide management strategies, owners can ensure they are implementing the right approach, at the right time, with the lowest financial impact. The goal of a management program should always be o focus resources on managing the asset while safely getting the most service life out of the pipeline.
Reducing CoF comes down to improving emergency events through field operations efficiency. Studies have shown that the time to shut down a pipeline had more impact on the consequence of failure than the diameter of the pipeline.
Utilities can reduce CoF — and in turn risk — by gaining a better control on their system, which can be achieved two ways:
For example, if a pipe fails and utility operations staff are unable to locate valves — or the valves are inoperable when they are located — it will take longer to isolate a pipe failure. This will result in greater damage, more water loss and longer outages and repair times as a result of the failure. Implementing a proactive program for control assets that focus on providing better data for field staff reduces CoF by decreasing emergency response time.
Many factors influence the likelihood that a pipeline will fail. Metallic pipelines, specifically, have a variety of failure modes and require a wide array of technologies to accurately assess their condition. Until recently, technologies for metallic pipe assessment have been unavailable or limited in their viability.
As a result, lower risk metallic mains have historically been prioritized for replacement using age, material and break history, while higher risk mains have sometimes been assessed with test pits along the length of the pipeline. After test pitting, statistical methods are used to extrapolate the condition of the test pit locations along the entire pipe length.
Through the development of metallic assessment solutions, condition data shows that pipe distress is often random and localized, meaning that an area of distress identified during the test pit method may inaccurately identify the entire pipeline as distressed, conversely, identify the entire length of pipeline as in good condition.
The development of reliable inline condition assessment tools provides owners with pipe-by-pipe data that gives a more complete picture of the actual condition of the pipeline. This allows for a more targeted management of small sections of pipe instead of generalizing the condition of an entire pipe length. It also allows for the collection of real data to drive pipeline renewal, which allows for more defensible capital decision making.