• Ozone counters carbon storage and other stories
  Environmental News Network, CA - Oct 29, 2003
  ... For the first time, researchers have used a combination of ocean circulation models, thermal imaging and airborne searches to help locate harmful floating ...

• Nation gearing up for new SARS season / Early detection, ...
  Daily Yomiuri, Japan - Oct 26, 2003
  ... observed. Japan has installed thermography machines at all major international airports to detect people with high fevers. Under ...

• Alien vs. Predator Plot Summary
  FilmForce - Oct 22, 2003
  ... Fast-forward to the present day. Charles Weyland, the billionaire industrialist, has discovered the Antarctic temple using thermal imaging satellites. ...

• Breast Imaging An Early Road To Cancer Recovery
  WBBM, IL - Oct 20, 2003
  ... can get a 95% pick-up rate if you do both a mammogram and thermal imaging ... Thermography is FDA approved, costs about $145, and insurance doesn't usually cover it ...

• Landslide Warnings For Lakeside Residents
  Xtra News, New Zealand - Oct 16, 2003
  ... Taupo District Council management services manager Peter Martyn says the threat is being monitored and infra-red thermal imaging will be used to survey the ...

• Ferndale company works to avoid NASA disasters
  Detroit News, MI - Oct 11, 2003
  ... Infrared thermography, as it's known, "is not your garden-variety testing system," said Shepard, the company's founder and president. ...

• Ferries face £ 2000 fines for carrying ' illegal immigrants '
  4ni.co.uk, UK - Oct 6, 2003
  ... New detection technology such as heartbeat detectors, thermal imaging and gamma scanners in France has contributed to 4,000 would-be illegal immigrants from ...

In the last two months we have completely overhauled the Infrared Training Center website. We have a new design, improved user interface, new features, and it runs much faster. Among the new features are a thermal image gallery and redesigned message boards.

Below you will find a selection the new topics started by visitors to the message board in October. Feel free to click the links, see how people have responded, and post your own response.

• Water damage restoration
  My company specializes in structural drying and dehumidification. I am interested to learn how IR technology might be helpful in moisture inspection within a structure. If you have experience in using IR to inspect for water or moisture in a building, I would like to hear from you.

• IR Contracting
  I'm looking into starting my own IR contracting business. Can anyone offer any information about how to market this type of work? There aren't any thermography companies within a 150 mile radius of where I live. Information regarding typical fees in any of residential, commercial, or industrial fields is appreciated. Also, I'd like to find out what type of problems people have had starting this type of business. Your hindsight could be very helpful to me.

• Thermographer business insurance
  I agree that this question is not specific to thermography as an application, but I need some experienced individual thermographers to offer their knowledge. I am an individual, self-employed, not connected with a company. I have been running into a brick wall regarding general liability coverage. there doesn't seem to be any companies willing to cover IR work. I am not rendering opinions, only "taking pictures" and the underwriters either don't understand what I do or it seems to be unprofitable to insure a "commercial photographer"; any suggestions as to a source ?

And of course if YOU have a question or want to start a discussion on a topic, we would love to hear from you. Just post a new thread on the message board.

By Leonard A. Phillips
Senior Writer for Infrared Applications, FLIR Systems

As many of you know, this conference, the 4th annual event of its kind, was held in Las Vegas, Nevada from October 13-16th. The event exceeded all expectations, breaking all attendance records and already seeding next year’s conference with over 100 pre-registrants!

“I agree! The conference was a great success.”
– Delegate MIKE RALPH, Excelon Nuclear--LaSalle Nuclear Station

“It was a pleasure speaking and writing the article. We will be interested in next years as well.”
– Presenter EDWARD FRONAPFEL, Professional Investigative Engineers

“It was such a great conference for us that we plan to be there next year for sure.”
– Presenter Mark Goodman, UE Systems

“I would like to participate in next year’s conference and have already preregistered. Thank you very much and best regards to the InfraMation team!”
– Presenter RAFAEL ROYO, Universidad Politécnica de Valencia

“The 2003 conference was my first thermographers conference and what a great way to start. The papers presented were excellent, the clinics were even better, the food was almost too good, and I had the opportunity to meet and talk with many people that have an excellent knowledge and skill in thermography. Our program will become much better for having attended. Please convey my regards to all those involved with the conference. I cannot express how grateful I am. I will find a way to be with you next year.”
– Delegate GLEN WARNIK, Utah State University, Facilities

Clearly, InfraMation has grown into a “must-attend” event . In fact fully ONE-THIRD of this year’s delegates have ALREADY signed up for InfraMation 2004! What makes this conference so different? 

High Temperature Heat Exchanger Alloy Emissivity Evaluation [top]

by Kirk Williams
University of North Dakota Energy & Environmental Research Center

The Energy & Environmental Research Center (EERC) identified an opportunity to utilize an unprotected alloy-based high-temperature heat exchanger (HTHX) that could reduce the size requirements for this component and significantly lower the overall cost of the system. The EERC is involved in the experimental development of an advanced coal-based power system that involves a pilot scale; high-temperature heat exchanger fabricated from oxide dispersion strengthened (ODS) alloys. The two alloys are MA754, a nickel–chrome alloy, and MA956, an iron–chrome–aluminum alloy. When subjected to oxidizing conditions, the MA754 forms a greenish-black chromium oxide layer and the MA956 forms a light-grey aluminum oxide layer. Each alloy has its own characteristic ambient emissivity value that proves to be different at very high temperatures.

The advanced HTHX design can be an integral part of an indirectly fired combined-cycle (IFCC) power plant and is currently being carefully tested in a coal-fired slagging furnace system (SFS) at the EERC. The HTHX is composed of three vertically oriented 6-foot-long by 2½-inch diameter tubes of ODS alloys which were originally protected from the products of combustion by ceramic panels.

In subsequent tests, the bare alloy tubes were exposed directly to the products of combustion in the SFS, which significantly increased heat exchange coefficients. The bare-tube HTHX is typically operated with inlet process air temperatures at 1000°-1020°F and alloy tube surface temperatures are 1380°-2010°F. The low end of the alloy tube surface temperature range represents the backside of the tubes at the process air inlet, with the high end of the range representing the front side of the tubes at the center of the HTHX. A schematic of the system is shown in Figure 1. The SFS is designed for a maximum furnace exit temperature of 2900°F but is typically run at 2800°F to maintain desired slag flow while extending the furnace lifetime.

Figure 1. Schematic of the EERC high-temperature slagging furnace system (click for larger image).

EXPERIMENTAL PROCEDURES

Recent developments in a joining design and assembly technique were used to replace the center tube of the all-MA754 HTHX, with a tube designed and fabricated entirely from MA956 alloy. The modified HTHX is shown in Figure 2 as a visible light image taken at ambient temperature before the test. Note the lack of an oxide coating on the center MA956 alloy tube as compared to the outer MA754 alloy tubes. In visible light, the difference in the appearance of the tubes is due to the oxide layer. The MA956 is an aluminum oxide forming alloy and does not yet have the familiar, light aluminum colored outer layer. The INCONEL 625 thermocouple-mounting pad on this tube can be used as a visual reference in the thermal image.

Figure 2. Visible light image of the alloy heat exchanger tubes. The middle tube is MA956 and the outer two are MA754 ODS alloy. Note the thermocouple pad and thermocouple wire on the middle tube. Also note the differences in oxidation layers on the tube surfaces that suggest emissivity differences will be likely (click for larger image).

The images used for this report represent a small part of a single test from a multi-year DOE project. These images show the pilot-scale SFS operating at 2800°F using natural gas-fire. The focus of this project was to accurately determine the surface temperature of MA754 and MA956 ODS alloy tubes during operation in a SFS while being internally cooled by the low-pressure air to just below their melting temperature. For metals, sustained high temperature exposure close to their melting point can be very damaging. Add the corrosive properties of flowing slag and the structural properties of the metal quickly diminish. The ODS alloys are designed to retain most of their mechanical properties at high temperatures and provide an oxide layer that can increase their resistance to coal-slag corrosion at the same time. However, it is this oxide layer in combination with the basic emissivity variation of the alloy that causes difficulties in obtaining accurate surface temperatures while in the operating environment. It has been determined that accurate surface temperatures of the tubes are needed to minimize the alloy corrosion due to flowing slag. The outer most surface of the tubes must be controlled such that this temperature is just below the melting point of the flowing slag. This temperature has been experimentally determined to be 2000°F. This means to maintain structural integrity of the HTHX array and still keep a high efficiency heat exchange process, the tube surfaces must not exceed 2000°F.

RESULTS AND DISCUSSION

Figure 3 is a false-color thermal image taken at the same maximum gas-fire temperature by a ThermaCAM SC 1000 with a 16 degree lens and 3.9 µm flame suppression filter. In this thermogram, the basic thermal differences between the alloys and the refractory are clearly represented. The emissivity differences between the alloy tubes can be noted by the brighter contrast of the center tube compared to the outer two tubes. The use of the iron-bow color palette is to enhance fine detail.

Figure 3. Thermogram of the alloys at maximum gas-fire temperature (click image for larger picture)

The complexity of determining accurate tube surface temperatures is significant. In this image, the target tube is in the middle, flanked on either side by alloys of different emissivities. The overall inside diameter of the combustion chamber is 6 feet and lined with high emissivity alumina refractory. The upper, natural gas-fired swirl burner directs the flame toward the center of the chamber, which is in front of the HTHX array. During operation, installation of a 6-inch diameter ¼-inch thick sapphire crystal view port permits the alloy tubes to be directly viewed and photographed.

To determine the alloy surface temperature, multiple direct and indirect temperature sources must be known. Although the combustion chamber is a dynamic environment, the temperature is fairly uniform. The tubes uniformly reflect the  apparent temperature radiation that is emitted from the flame and the surrounding heated refractory toward the IR detector. This reflected IR radiation must pass through the heated sapphire view port that further restricts radiation transmission due to the slight thermal opacity of the crystal. Temperature of the optics, both external (the view port) and internal (the camera lens) must be accounted for since this can be considered additional source for thermal radiation (although very small in this case, it still must be considered important).

SUMMARY AND CONCLUSIONS

Emissivity values of the alloy itself change with different surface finishes and different temperatures. To account for all material and surface finish differences is challenging at best, so multiple applications of thermocouples were used on the middle tube as a method of referencing the actual temperature of that tube close to where the targeted spot temperature was taken. Each tube has its own thermocouple array that was used to correlate the actual temperature to the appropriate thermogram during the recording sequence. The final surface temperatures for the two outer MA754 alloy tubes of 1988°F and 1981°F compared to the middle MA956 tube at 1985°F, were determined by continuously adjusting the emissivity values of the alloys (0.95 for MA754 at 2000°F and 0.77 for the MA956 at 2000°F) and reflected apparent temperatures (approximated at 2600°- 2800°F), within known (reasonable) parameters, to match the actual recorded thermocouple temperatures (1985°F) as closely as possible. All well-known or previously documented parameters such as optics temperature (sapphire 250°F, camera lens 110°F), and transmissivity (83%), target distance to lens (2 m), and ambient air temperature (100°F) remained fixed during the post-imaging analysis. It should be noted; the SFS is a thermally dynamic environment. Obtaining an accurate, reproducible alloy surface temperature that coincides with the mechanically bonded thermocouple that is in intimate contact with the surface at all times remains a challenge.

Editor's note: Kirk receives an InfraMation Executive Attaché for his article contribution. Thanks Kirk.

Brainteaser of the Month  [top]

Here is this month's brainteaser. First reader to email me with the correct explanation of the thermogram receives a gift from ITC. Please put "Brainteaser" as the subject of the message.

Click here to email your guess

Do you have an interesting image that you think would stump other thermographers? If so please email me your image (preferably in native .img, .jpg, .tif, .tgw, or .tmw format) with an accompanying visible photo and explanation. If your image is used, you receive a gift as well.

Our winner for last month's Brainteaser is Brian Fortney from Manitoba Hydro in Canada. Most of the guesses were of the moon behind a tree. But some of you caught my clue "a honey of a Brainteaser" and guessed correctly that it is a hornet's nest in a tree, but Brian sent me the first correct guess.

Brian receives our special low emissivity traveling coffee mug for his guess. Thanks to Ron Lucier for the image.

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