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
Sponsor: ORNL State
Partnerships Program