Inspection Technology

The Role of Non-Destructive Testing in Identifying Loss of Preload in Pipelines
Wednesday, August 16, 2023

The Role of Non-Destructive Testing in Identifying Loss of Preload in Pipelines

The Role of Non-Destructive Testing in Identifying Loss of Preload in PCCP-lines

Pipelines serve as lifelines for countless industries, enabling the transportation of vital resources across vast distances. Maintaining the safety and integrity of these pipelines is of the utmost importance. One significant threat that can compromise the integrity of Pre-Stressed Concrete Cylinder Pipes, in particular, is the loss of preload, which refers to the reduction of pressure containing capability of the pipe.

To detect this potential hazard before it leads to catastrophic failures, PICA Corp. employs advanced non-destructive testing (NDT) methods. Below, we will explore the crucial role of NDT in identifying loss of preload in PCCP water mains and the significance it holds for safeguarding infrastructure and the environment. Continue reading to learn more. 

Understanding Loss of Preload

Loss of preload occurs when the tension (or preload) in Pre-Stressed Concrete Cylinder Pipes (PCCP) diminishes over time. This typically occurs due to several factors, including hydrogen embrittlement cracking or corrosion of the re-enforcing wires of PCCP lines. When the preload of pre-stress wires of PCCP lines decreases, the pipeline is at high risk of failure.

Challenges in Identifying Loss of Preload

Detecting loss of preload in pipelines poses significant challenges for municipalities and other industries. Typically, PCCP pipelines run underground or underwater, making non-destructive visual inspections almost impossible. Moreover, traditional maintenance methods that involve disassembling the pipelines for inspection are impractical and can disrupt operations, thereby incurring high costs. Fortunately, PICA has several non-destructive pipeline inspection solutions to detect this condition in PCCP pipes! 

The NDT Solution

PICA’s SeeSnake RAFT (Restricted Access Flexible Tool) and SeeSnake EMIT (Electro-Magnetic Inspection Tool) play a crucial role in identifying loss of preload in pipelines, particularly in C-301 PCCP and C-303 bar-wrapped pipes. Both of these innovative tools are designed to conduct non-destructive inspections of water mains, allowing for the detection of potential issues which may lead to a loss of preload in these pipelines. Details on these NDT pipeline inspection tools are as follows:

The SeeSnake RAFT: 

PICA’s SeeSnake RAFT tool, with its collapsible design, can be efficiently inserted into pipes through small access manways. By traversing approximately 2 km (1.4 miles) of 36” to 60” diameter pipes daily, this tool provides accurate and detailed information regarding the pipeline condition. This enables PICA’s technicians to identify any signs of weakening or loss of preload in the pipelines’ pre-stress wires, which could result from factors such as hydrogen embrittlement damage, localized corrosion, or other structural defects.

The SeeSnake EMIT:

Similarly, PICA’s SeeSnake EMIT is a self-contained NDT pipeline inspection tool designed explicitly for large internally lined pipes between 60” and 108” in diameter. By employing electro-magnetic inspection capabilities, this tool excels in detecting the loss of preload in C-301 E pipes resulting from broken or damaged wires that compromise local cylinder compression. In addition, the SeeSnake EMIT can identify a range of PCCP defects, including broken wires and corroded cylinders, which can contribute to the loss of preload.

Since both of these innovative tools are self-contained and non-destructive testing solutions, PICA’s technicians enable pipeline operators and owners to proactively identify and address potential issues related to loss of preload without disrupting their operations or causing unnecessary damage. By utilizing the collapsible design of these tools, PICA’s highly trained technicians can easily enter limited access locations, enabling our team to perform comprehensive inspections and detect critical flaws that could lead to the loss of preload in PCCP pipelines. 

PICA Corp.: Your Source for NDT Pipeline Inspections

Non-destructive testing has revolutionized how we inspect and maintain pipelines, providing municipalities and industries with a proactive approach to identifying loss of preload and other threats to infrastructure integrity.

For over three decades, the experts at PICA Corp. have been deploying advanced NDT pipeline inspection techniques to ensure the early detection of potential hazards, reducing the risk of costly failures and environmental damage and ensuring the continued safe transport of potable water, wastewater, raw water, slurry, and more. 

Contact PICA today to learn more about our NDT pipeline inspection services!


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