Sensor tackles turbine turmoil

Poorly maintained gas turbines can leave companies with repair bills of up to $4 million if they break down. New sensors from Radatec aim to slash costs incurred by these broken-down behemoths.

Maintaining large rotating equipment isn’t easy or cheap. Take gas turbines used in power plants: Inspecting one of these behemoths for possible wear and tear costs about $500,000 in parts and labour. If companies skip on periodic check-ups, they risk breakdowns averaging $4 million per incident.

Yet Atlanta-based Radatec believes it is about to transform condition monitoring with a new breed of non-contact displacement sensor.

Scheduled for commercial release later this summer, Radatec’s sensors provide real-time information about critical mechanical components in areas that were previously off limits.

“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.”

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 up to 2,500 degrees Fahrenheit. They also remain unaffected by contaminants such as oil, dust and carbon deposits and are immune to electromagnetic interference.

These characteristics allow Radatec’s sensors to operate in harsh environments. “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.”

Smaller and cheaper

Billington and Geisheimer launched Radatec in the autumn of 2001, licensing technology they helped develop as researchers at Georgia Tech’s Manufacturing Research Centre and the Georgia Tech Research Institute. Since then, the company has filed several patents of its own and in 2002, Radatec was admitted to ATDC, Georgia Tech’s incubator for fast-growing technology companies.

Because initial sensors were built for high-end military aircraft, Radatec used expensive components in the 24.1 GHz band. Yet last summer the company set out to build a more affordable system for commercial users.

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 is said to have exceeded expectations, reducing both size and cost of sensors more than 100 times.

“Even though we’re using less expensive components, performance remains the same,” says Dave Burgess, Radatec’s director of business development, noting that the sensors are accurate up to .0005 (half of one-thousandth of an inch). “We’ve also reduced assembly costs 10 times by migrating to an electronic-circuit board product.”

The 5.8 GHz band is also said to significantly reduce weight, a bonus for aerospace applications. Although Radatec originally intended to maintain separate platforms, it will now use the 5.8 GHz band for both military and commercial products.

“It’s interesting that we’re applying cutting-edge telecom technology to machinery that fundamentally hasn’t changed in a hundred years,” Billington observes. “Most of our suppliers are surprised why we want these parts because they were never intended for displacement sensing.”

Fine-tuning for launch

The global market for condition-monitoring equipment and services totalled more than $1 billion in 2002 with vibration-monitoring equipment comprising $491.7 million. Within that sector, Radatec is targeting power generation and industrial rotating equipment.

Currently the company is streamlining its new prototype for production, shrinking size even further and improving signals.

Other refinements include a standard data bus, which will allow Radatec’s sensors to plug into other factory systems. Radatec is also adding logic that will trigger sensors to begin saving data when certain alarm levels are tripped, for example, if temperature or speed of machinery is too high; and self-calibration using an advanced radar vector tracking system. This “teaching” algorithm will increase accuracy by eliminating the effects of objects near the sensors.

Beta testing began earlier this year with several industry partners. One customer is monitoring a hydroelectric generator at a Georgia dam. Another partner is including the sensors in an online monitoring system for DC motors found on diesel-electric locomotives.

The goal of beta testing is demonstrate accuracy and reliability while documenting Radatec’s ability to reduce maintenance costs, increase productivity and improve safety.

“One of our challenges is getting industry to recognise just how revolutionary these sensors are,” Burgess observes. “People understand condition monitoring, but they’ve never been able to do it in the areas we can now.”