Wall-Crawling Robots Something out of Science Fiction

Innovative robotic technology is aiding TVA's generation outage inspections in new ways, generating accurate readings while saving the company time and money.

JUNE 8, 2020 — Cumberland Fossil Plant System Engineer Matt Beaty needed better information about the condition of the plant’s Unit 2 boiler in advance of the upcoming outage, and he needed it fast — so he turned to robotics.

When he’d first heard of the technology, he was skeptical. “To have a robot crawl on the walls and do accurate readings? Seemed like something out of science fiction,” he said.

man working on sytem

Using their strong magnetic bodies, the robots crawl up the 190-foot-tall walls across eight boiler tubes with three different beam angles reading simultaneously — a total of 7 million readings of raw data. In 16 to 18 hours, a robot can determine the thickness of an entire sidewall, which reduces the inspection time.

“This type of inspection gave us a better picture in less time and at less cost than our traditional way of doing it,” said Steve Standefer, project manager, Generation Projects.

Typically, this kind of inspection is required during a long-term outage using the scaffold infrastructure and a team of boilermakers to manually check the wall for fireside corrosion in a grid-like pattern. It can take up to two weeks and results in only 1,500 readings.

“The upcoming fall outage is a tight window, which is why we inspected during an out-of-cycle outage to get quick results without impacting the outage schedule,” Beaty said. “It provided better data to order the right amount of replacement panels. And at $20,000 each — they aren’t cheap.”

The robotic inspection saved up to $500,000 in contract labor and material costs. It also identified areas of erosion that couldn’t be seen with the naked eye. In one instance, an area worn smooth could have resulted in a boiler tube leak impacting generation as early as this summer.

“TVA has a clear work scope for the fall outage,” Standefer said. “It was also a non-destructive examination. Normally, our boilermakers have to grind down the panel surface to do an accurate reading of wall thickness.”

This work will prepare the boiler for a thermal coating spray during the fall outage, which will make it more corrosion-resistant. This will prevent the need to conduct costly repairs in the future.

“This is the first time we’ve used this technology. It gives us a better picture of the health of our boilers and limits the risk of injuries, since it’s less hands-on,” Standefer said. “There may be more opportunities to use this technology in the future to inspect tanks and bunkers remotely without costly and time-consuming scaffolding.”