Phosphor Thermometry Diagnoses Feverish Boiler Tubes 

Boiler tubes in steam power plants operate under extreme temperatures and pressures that can cause them to fail, endangering lives and disrupting operations. Researchers at ORNL and Tennessee Technological University (TTU) have developed a way to measure boiler tube temperatures during operation to spot problems before they become critical. 

The technique, phosphor thermometry, involves coating a surface with a temperature-sensitive phosphor, using a light source (such as a laser) to cause the phosphor to fluoresce, and then determining the surface temperature by analyzing the fluorescence. (ORNL developed this technique for the steel industry and received an R&D 100 award for the technology, along with its industrial partner National Steel.)

A “hot spot” on a boiler tube surface indicates impaired steam flow through the tube. A damaged tube deteriorates rapidly. If a leak develops, the resulting steam jet may cut other nearby tubes, starting a cascade that will knock the boiler offline and risk injury or death to workers. Accurate thermometry can signal that a tube needs repair before it fails.

TTU developed an optical probe to be installed in an access port in a furnace to monitor the temperature of a phosphor-coated surface. Next, an application system was needed to coat a boiler tube during operation. ORNL developed a promising coating mixture (a magnesium-based phosphor, mixed with binders) and sprayer (a modified Walther Pilot spray gun). In tests at TTU, the system successfully applied a strong, uniform coating to a tube operating at more than 1000°F. With successful coating application demonstrated, the phosphor thermometry system is ready for field testing. 

ORNL and TTU are contacting organizations that might be interested in testing the system.  The capability to accurately measure and adjust boiler tube surface temperatures in operation would increase plant efficiency and availability, saving millions of dollars and improving energy efficiency.

Contact: Steve Allison