Risk-Based Condition Assessment

WaterWater utilities across the United States face a major funding gap related to buried pipeline infrastructure. The U.S. Environmental Protection Agency (EPA) estimates the difference between what is needed for infrastructure renewal and what utilities can afford to spend is between $200 billion and $1 trillion over the next 25 years. An increased number of pipeline failures that disrupt everyday life and are expensive to mitigate is adding additional scrutiny despite the fact that many utilities do not have sufficient funding to implement traditional pipeline management strategies to renew or replace their aging infrastructure.???????

This new reality has forced utilities to squeeze more remaining life out of existing assets, creating more demand for condition assessment programs and proactive management of pipelines. Historically, there have been a few specialized firms that respond to high profile failures; however, the recognition of the value and implementation of condition assessment programs by many utilities has made pipeline management a significant industry. This has resulted in many utilities successfully managing risk and extending the life of assets for a fraction of the cost of a replacement program.?

According to a study by Pure Technologies, large diameter pressure pipe can be inspected, repaired and managed for roughly 4 percent of the capital replacement cost. Pure has found that pipeline distress is typically not systematic across the entire length of a pipeline, but is usually related to localized problems due to design, manufacturing, installation, environmental, operational or maintenance factors. Proactively locating and repairing specific pipe sections with distress is proving to be a cost-effective method of addressing the infrastructure gap associated with buried pipelines.??????

As utilities move toward condition assessment programs that focus on entire transmission or distribution systems, it is clear that there is no single condition assessment strategy that works for all pipelines. Several variables affect which strategies and technologies should be used to assess a given pipeline, including likelihood of failure, consequence of failure, pipe material, and available budget.

Proactive utilities have realized that when implementing condition assessment for a system of pipelines, a risk-based approach should be used to ensure resources are invested in an intelligent manner that maximizes the benefit of a program.

Defining Risk and Pipeline Priorities

A basic approach can be used to define risk even in complex systems; simply, risk is a product of consequence of failure and likelihood of failure (COF x LOF). Consequence of failure refers to the damage a failure would cause based factors like its location, the amount of users it supplies and its size and operating pressure. Likelihood of failure refers to the probability of a failure occurring based on factors such as age, pipe material, soil conditions, operating pressure and failure history, among others. This equation can account for many of the complex nuances of a pipeline system and provide a scientifically defensible approach for a program?s viability and usefulness.???????

Once risk is defined, the pipeline inventory can be prioritized which helps in the selection of condition assessment approaches and technologies. In general, high-risk pipelines typically warrant a detailed assessment while low risk pipelines can use lower resolution alternatives.???????

When defining risk, a utility can take either a qualitative or quantitative approach. Qualitative approaches can be as simple as an internal meeting at the utility where each pipeline is listed and given a priority. In these cases, pipelines that managers consider to have the highest consequence of failure are prioritized with the highest risk, followed by medium and lower consequence pipelines. For example, it is obvious that a large diameter PCCP transmission main in a city center has a high consequence of failure; a utility manager does not need to complete a detailed analysis to determine this.????????

Detailed analytical risk analysis involves establishing a scoring system that quantifies COF and LOF variables. Some variables will require subjectivity to provide a score, but in the end a defensible, objective approach to pipeline risk and priorities is established. After an initial COF and LOF are determined for each pipeline, the risk can changed based on external factors. For example, if the COF or LOF becomes higher, than the risk becomes greater. One example of this could be a pipeline that is initially identified with a low COF, but becomes more critical when the area surrounding the pipeline is developed.

Using Risk to Select Condition Assessment Techniques??????

When selecting condition assessment techniques, qualifications and technical judgment should be used in lieu of price. High resolution comes with a higher cost, but saving money on a low resolution condition assessment is not a responsible alternative. For example, the savings gained by selecting a low resolution technology for a large-diameter, high-risk asset are often miniscule in comparison to the repair and capital programming decisions that result from the condition assessment data. If the data is inconclusive or in error, a utility may unnecessarily invest millions in a capital program that was not required, easily eliminating the savings achieved by selecting a less expensive solution.

This recently became evident on a 20-in. steel transmission main where a low resolution technology was used to perform condition assessment.? The utility opted for a low resolution technology that produced data that erroneously recommended replacement of portions of the pipeline.? Fortunately, prior to replacing the pipeline, the utility implemented a higher resolution technology which identified a few locations of deterioration along the pipeline, but did not recommend replacement. This allowed the utility to realize major capital savings be selectively rehabilitating the 20-in. main.???????

Additionally, the cost of a failure should be considered when selecting a lower-cost assessment for a critical pipeline. The average cost of a pipe failure is between $500,000 and $1.5 million; money saved on lower-resolution assessment can easily be negated by the cost of mitigating a failure and the resulting reputational damage.???????

One method of selecting a technology is to compare certainty to risk. When dealing with a high-risk asset, it is important that the solution allows the utility manager to be confident in the results.???????

Determining the appropriate technology resolution for critical pipelines is a lot like handling a significant health concern. For example, if a person gets chest pain when they exercise ? a serious problem ? there are different levels of medical certainty they can attain. Going online to search medical journals or websites and completing a self-diagnosis is a free option, but it provides little certainty. Another option is visiting a general practitioner. He will be able to decide whether something is wrong, but won?t be able to diagnose it specifically and will recommend further investigation. To be confident in the results, the person would need to visit a heart specialist and complete specific tests. While each of these options gets more detailed and costly, the risk of leaving a heart problem untreated outweighs the cost of a detailed evaluation from a specialist.??????

Utility managers should treat their critical large diameter pipeline assets like they would a serious health concern, as the risk of uncertainty far outweighs the cost of being sure. Although a high resolution condition assessment that produces confident results is necessary for critical pipelines, medium and low resolutions can be very effective on medium and low risk assets.???????

These methods are more cost-effective, and when used on lower-risk pipelines can produce adequate condition information to make responsible decisions, including the decision to re-inspect with a higher resolution tool if needed. Low resolution assessments include traditional engineering studies and data analysis, but can also include test pitting at specific locations. They provide excellent preliminary detail for high risk pipelines and can be used to make rehabilitation decisions on low risk assets.

Medium resolution condition assessment technologies provide an excellent survey compared to traditional low resolution methods, particularly on metallic pipelines. Historically, metallic mains have been assessed through test locations along the length of a pipeline. However, data shows that pipe distress is localized, meaning that an area of distress identified using historical methods may inaccurately identify and entire pipeline as distressed, or conversely inaccurately identify the same length of pipeline as in good condition.

Despite only identifying broad areas of distress, medium resolution technologies provide condition data for an entire pipeline length, which eliminates the inaccurate averaging of localized pipe condition data across an entire length. This provides a higher level of certainty when identifying specific areas of distress along a pipeline.

The challenge for most utilities is completing any level of condition assessment within a tight capital budget. However, by completing a thorough risk-based prioritization, utilities can select the most appropriate inspection solution and allocate their funds responsibly. This approach allows utilities to maximize their budget and extend the useful life of assets in a scientifically defensible program that ensures long term sustainability.

Mike Higgins is a vice president for Pure Technologies in Columbia, Md. He is responsible for engineering services for the Americas and has been involved with hundreds of miles of pressure pipe condition assessment and management projects throughout his career.?

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