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A team of researchers at UBC Okanagan are investigating a new method to monitor underground gas pipelines with high-tech ultrasonic sensors that can make it easier to find weaknesses, discrepancies and a diversion in residential natural gas lines.
While research has been done for diagnosis methods for steel pipes such as radiography, ultrasonic testing, visual inspection and ground penetrating radar, Abdullah Zayat, a master of applied science student, says little has been done on the high-density polyethylene (HDPE) pipe.
The HDPE pipe is commonly used and carries natural gas to homes.
“Early detection of structural degradation is essential to maintaining safety and integrity,” Zayat explains. “It lowers the risk of catastrophic failure.”
Zayat and his supervisor Dr. Anas Chaaban, who is an assistant professor of electrical engineering, tested a technique that allows for the inspection of HDPE pipes with ultrasonic sensors, which transmit ultrasound signals through the pipe.
The new monitoring method limits the likelihood of gas diversions, where gas is siphoned to an unmetered location for unmeasured consumption.
Dr. Chaaban says tampering with the pipe poses many risks because it is unrecorded, violates pipeline quality standards and can lead to potential leaks and possibly explosions.
“This can pose a significant risk to public safety, property and the environment in the vicinity of the altered gas line,” he explains. “Such diversions have been discovered in the past through word of mouth, leaks or unexpected encounters with an unrecorded natural gas pipe in a construction site.”
Previous research has studied the inspection of metallic structures using ultrasonic-guided waves (UGWs), but this type of testing has not been done for non-metallic structures such as HDPE pipelines.
The research team says it is challenging to inspect underground pipes given their concealed nature. Existing solutions include ground penetrating radar and endoscope cameras, but both are invasive and expose inspectors to potential risks.
Zayat says that having a non-invasive method using ultrasonic sensors enables the inspection of buried, insulated and underwater pipelines. It also provides a larger range of inspection than traditional ultrasonic testing because it uses the structure of the pipe itself as a waveguide.
“UGW sensing is getting a lot of attention from the industry because of its long-range inspection capabilities from a single test location,” he explains. “They can inspect more than 100 metres of pipeline from a single location."
With this type of detection system, the sensors clamp onto the exposed portion of the pipe and connect to the section of pipe that emerges above the ground where it connects to the metre.
The technology is still in the early stages, but Dr. Chaaban says the majority of the research has involved the development and assessment of a deep-learning algorithm for detecting diversion in pipes.
Results suggest that the method has 90% accuracy when one receiving sensor is used, and nearly 97% accuracy when two are used.
Dr. Chaaban adds: “By combining classical signal processing with machine learning, we can more efficiently and accurately determine if there is an issue.”
The research was funded in part by FortisBC and Mitacs, and it appears in the latest edition of Sensors.
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