Gas Line Safety

Reversing Time for Early Detection

Researchers at Carnegie Mellon are working to improve the safety of natural gas lines. Motivated by several high-profile accidents caused by cracks in buried pipelines, Carnegie Mellon engineers are looking for solutions to detect cracks early — and at a lower cost to inspectors.

The most common way to inspect gas piping is to excavate a section of it and attach a large metal ring filled with sensors. This ring uses ultrasonic waves to listen for cracks. But the method is expensive and time consuming.

"Unfortunately, these rings have a large power requirement, typically operating in hundreds of volts," said Carnegie Mellon's Nicholas O'Donoughue, a Ph.D. candidate in electrical and computer engineering. "Our approach is aimed at reducing the power requirements down to the 1-10 volt level so that it becomes feasible to leave the ring there. That way, you don't have to dig up the pipe whenever you want to test it."

The result? Lower operating cost and the ability to test the pipe much more often.

"Exactly how often will depend on how we provide the power, for example batteries or solar, and what kind of lifespan is desired for the piping," he said.

The team is led by Electrical and Computer Engineering Professor José M F Moura and Civil and Environmental Engineering Professor James Garrett. What is unique in their design is the application of time reversal.

"Often people are intrigued by time reversal. It is not as if we have the power to reverse time, and with it, aging, and return to those great moments of the past," Moura explained.

"Time reversal is a signal processing technique that has been under some study for almost 20 years now in both ultrasonic and electromagnetic applications," he said. "It is simple to understand — it is like when you record music or a video and then you replay it, but this time in reverse, you see the last scene first and you go backwards to the beginning. And with that, you have a simple method that can focus signals on targets of interest, say defects on a pipe."

If successful, the team's approach would provide an embedded solution, which only requires one excavation for each section of monitored pipe to install the sensors, instead of repeated excavations for each test.

"The utility companies benefit most visibly, from reduced cost and greater knowledge of the condition of their infrastructure, but everyone who is served by these pipelines or who has a pipeline running near their home benefits from increased safety."

Over the last 10 years, Pennsylvania has had 12 fatalities, 55 injuries, and $70M in property damage from pipe failures. Nationwide and state-specific accident statistics can be found online by visiting the Pipeline and Hazardous Materials Safety Administration website.

"According to that site, Pennsylvania has 60,000 miles of pipeline — 2,500 for hazardous liquids, the rest for natural gas," O'Donoughue said. "Corrosion accounts for roughly half of the failures; the other half are caused by damage to the pipe — people digging without checking for buried pipes."

Moura was recently named a recipient of The Philip L. Dowd Fellowship Award. The Dowd Fellowship is awarded to a faculty member in engineering to recognize educational contributions and to encourage the undertaking of an educational project, such as textbook writing, educational technology development, laboratory experience improvement, educational software or course and curriculum development.

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