Water is our most precious resource, and utilities can’t take chances when it comes to the supply of water to our communities. Understanding the condition of water pipelines is integral to supplying safe drinking water for communities, we look at technology that allows for thorough condition assessment without supply interruption.
To optimise infrastructure management and ensure the reliability of its water supply network, a leading water utility in Australia initiated a comprehensive pipeline rehabilitation and replacement project on what it described as one of the most critical assets in the entire water network.
This approach, while straightforward, often leads to unnecessary expenditures and disruptions, as entire pipeline segments are replaced regardless of their actual condition. To address these inefficiencies, the utility decided to adopt an innovative condition assessment program that allowed for a much more targeted and strategic approach to pipeline replacement and rehabilitation, potentially saving tens of millions of dollars annually.
As part of the targeted condition assessment of this section of water pipeline, Detection Services was commissioned to conduct p-CAT™ testing and provide detailed findings regarding the pipeline’s condition. The primary objectives of the assessment were to evaluate the pipeline’s condition and identify features and anomalies such as blockages, air pockets, and wall thickness deterioration.
The pipeline in question, constructed in two stages in 1982 and 1983, spans approximately 6.5km. Stage one was
completed in 1982 while stage two was completed in 1983. The pipeline is predominantly composed of OD965 mild steel cement lined (MSCL) pipes, with several short sections of DN960 MSCL replacements.
“It is one of the most critical assets in the water network,” said a Project Engineer from the utility.
“There were question marks over the condition of this pipeline based on its history, as well as another pipe close by.”
Given its critical role in the water network, there were significant concerns regarding the pipeline’s construction and materials. Notably, the pipeline had been stored dockside for an extended period before installation, raising questions about its integrity. Furthermore, there was minimal failure history, primarily relating to fittings and rubber ring joints, which compounded the concerns about the pipeline’s overall condition.
Based on historical information and the potential risks associated with the pipeline, the initial plan was to replace the entire section, with an estimated cost of between $30 and $40 million. This plan was included in the capital forecast, reflecting the utility’s commitment to ensuring the reliability of its infrastructure.
However, the utility recognised there was a need for a better understanding of the business risks associated with potential pipeline failures, which prompted the utility to seek alternative solutions through Detection Services.
Testing and findings
Detection Services undertook p-CAT™ testing on the pipeline, which uses two main techniques for interpreting the transient pressure wave tests results:
Sub-section partitioned wave speed analysis for assessment of the level of deterioration of the pipe wall in a sub-section
Signal analysis for detection of known features and significant anomalies such as air pockets and blockages
The following condition was identified during the p-CAT™ analysis:
- 12.5 per cent of the total pipeline length has a remaining wall thickness of 74 to 76 per cent
- 23.4 per cent of the total pipeline length has a remaining wall thickness of between 77 to 79 per cent
- The rest of the pipeline (59.9 per cent of the total length) has a remaining wall thickness of 80 to 89 per cent
The following known features and anomalies, and their resulting recommended actions were also identified during the signal analysis:
- Two high priority anomalies representing the presence of large pockets of permanently entrained air
- Three medium priority anomalies:
- An open off-take (OT4) which was presumed closed
- And a pocket of permanently entrained air at an air valve (AV5.1)
- Seven low priority anomalies representing the following known features:
- A large open off-take
- Four replacement sections of pipe
- The branches on two sealed off-takes
The condition assessment conducted by Detection Services provided invaluable insights, ultimately deferring the planned capital project.
This proactive approach allowed the utility to implement a more strategic condition assessment program, leveraging innovative technologies and methodologies to maintain and enhance their water network more efficiently.
“The cost replacing the pipeline was estimated at 30 to 40 million dollars and it was in the capital program,” said the utility Project Engineer.
“We had every intention to go ahead with that.”
This highlights the level of detail p-CAT™ testing can provide on critical infrastructure; and underscores the importance of targeted infrastructure management in modern utility operations. Importantly, the detailed information was acquired without taking the asset out of service and without carrying out any invasive techniques.
Featured image: Understanding the condition of water pipelines is integral to supplying safe drinking water for communities. Image: Image: Greg Brave/Shutterstock.com.
