Coal, Gas

High-Temperature Sensor Could Lower Turbine Operating Costs

Issue 9 and Volume 108.

Maintaining gas turbines is difficult and expensive. Inspecting a central station gas turbine for possible wear and tear costs about $500,000 in parts and labor. If companies skip periodic checkups, they risk breakdowns averaging $4 million per incident.

A company formed by former Georgia Tech researchers has developed a new non-contact displacement sensor system that monitors rotating industrial equipment, including sections of gas turbine engines that reach 2,500 F. The company, Radatec, is producing sensors that provide real-time information about critical mechanical components in areas that were previously off limits due to their harsh environments.

“We take the guesswork out of maintenance,” says Scott Billington, Radatec’s president and co-founder. “Instead of having to shut down heavy equipment, Radatec’s sensors allow operators to virtually see inside complex machinery and predict when repairs are needed.

Radatec’s microwave-based vibration and displacement probe contains no active elements, enabling long-term operation in the harshest of industrial environments. Photo courtesy of Gary Meek, Georgia Tech.
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Based on microwave technology, Radatec’s sensors measure motion by sending a continuous microwave signal toward a vibrating or rotating object. This signal is reflected back to a radio receiver in the sensor. A patented algorithm then compares the transmitted signal with the received one, calculating a measure of displacement. In contrast to existing sensors that use capacitive, eddy current or laser technologies, Radatec’s sensors operate at temperatures up to 2,500 F, remain unaffected by contaminants such as oil, dust and carbon deposits, and are immune to electromagnetic interference

“Existing sensors work well in certain applications, but can’t be used in areas where it’s very hot, dirty or contaminated, ” says Jonathan Geisheimer, Radatec’s co-founder and vice president. “And because these regions are often the most stressed areas of machinery, it’s where major problems develop first.”

Because the first sensors were built for high-end military aircraft, Radatec used expensive components in the 24.1 GHz band. The company has since developed a more affordable system for commercial users. Winning a $100,000 Small Business Innovation Research grant from the National Science Foundation, Radatec began working with 5.8 GHz components ” parts found in consumer wireless networking applications. Completed in December, Radatec’s new 5.8 GHz platform has exceeded expectations, reducing both size and cost of sensors more than 100 times.

Dave Burgess, director of business development, notes the sensors are accurate up to 0.0005 of an inch. “We’ve also reduced assembly costs 10 times by migrating to an electronic-circuit board product.” He says one challenge is getting industry to recognize just how revolutionary the sensors are. “People understand condition monitoring, but they’ve never been able to do it in the areas we can now.”