by Raphael Danjoux, PhD.
ITC France

What is a steam trap ? How does it work ? How does it fail ? All these subjects are thoroughly documented on the internet. Because it may affect the performance of a process if it fails, a steam traps are items that require regular inspections, and Infrared thermography is an excellent tool.

How do you use a thermography camera to detect a steam trap fault ?

According to A. Bandes and B. Garelick (in Inspect Steam Traps for Efficient System. Faulty or inoperative steam traps can cause losses of hundreds of thousands of dollars. Alan Bandes UE Systems, Inc., Elmsford, NY and Bruce Gorelick Enercbeck Systems, Charlotte, NC), proper thermal inspection relies on upstream/downstream temperature variations in a trap.

In other words, you need to store, and further analyze a sequence to get full data. Very few customers do that; at least in France; and most inspections rely on static analysis of a single thermogram. First of all, few cameras are equipped with such a feature (S60, S65 and others in option). Then, although sequences can be displayed in ThermaCAM Reporter 7.0, the software does not allow for time plotting. Reporter 2000 had a trending function that could do it on a series of single images but not on a sequence. Its best to use ThermaCAM Researcher!! Here's the basic methodology:

Place an analysis area on the output pipe of the trap.

Choose an analysis function, for instance a rectangle, and place it on the thermogram. We will record the average time vs. temperature data for this area. In the case of the steam trap, the initial signal is rather noisy, so a linear smoothing with a (5X1) operator gives a better result (this can be performed after the data is exported to Excel).

A graph of the smoothed data after exporting to Excel

For the duration of the acquisition the mean value is 120.26°C, the amplitude (peak to peak) however varies a bit. This latter may be due to all external factors including; condensate load, steam pressure variations, or probably the wind in our case. The period, however, looks rather stable: about 4.2 seconds. The fact that the trap is cycling provides good evidence that it is operating correctly.

A trap that is not cycling may have failed open, failed closed (in this case the temperatures may be significantly below saturated steam temperature at the outlet, or may be undersized for the condensate load (in this case the temperature upstream of the trap may have a lower than expected temperature). - Editor

A second sequence was grabbed with 4 steam traps in the field of view. Since there was no tripod used, a slight movement between each thermogram was noticeable. The complete results, however, are equivalent to those presented before, and only one thermogram is shown here.

       
A gang of steam traps.

Conclusion

Considering the steam pressure, the fluid temperature, the type of equipment (discharge volume & duration), the production settings, etc, it should be possible to define for each steam trap a standard set of working factors for a reference baseline. Then, monitoring would allow for tracing a trending curve. These are the basics for condition based maintenance and predictive maintenance.

You can find a detailed description of the steps used to capture and analyze these steam trap data for Researcher and many links to steam trap inspection information by clicking this link (pdf).

Straight from the World wide web, here is what's going on in the world of infrared thermography.

• BHSU prof receives grant to study Mars lava flows
  Black Hills Pioneer, SD - Jan 31, 2005
  ... Again, the researchers will conduct simulations with wax and look at active Hawaiian lava flows with a thermal infrared camera to get an idea of where lava is ...

• Learn how to cool off winter heating bills
  Boston Herald, MA - Jan 27, 2005
  ... leakage. He'll also demonstrate two diagnostic tools that pros use: the ``blower-door'' test and infrared-camera examinations. More ...

• New homes designed to save energy
  Billings Gazette, MT - Jan 23, 2005
  ... problem spots. To finish up, they looked throughout the house with an infrared camera for any leaks they may have missed. The house ...

• What to do after the deluge
  San Francisco Chronicle, CA - Jan 22, 2005
  ... That's the infrared camera, which fans of the CBS series "CSI" might remember lead character Gil Grissom pointing at a female character and, upon seeing her ...

• 'The Human Body' invites us to be amazed as never before by how ...
  Indianapolis Star, IN - Jan 20, 2005
  ... The body's joints behave like precision machines when computer graphics reveal how a boy's skeleton works as he bikes to school; thermal imaging shows the hot ...

• Tech Searches That Really Matter
  Wired News - Jan 19, 2005
  ... image on the device's display means. "A thermal imager is only as good as the operator," he said. Hagel said his team also utilized ...

• Carlos Antonio Rios / Chronicle
  Houston Chronicle, TX - Jan 18, 2005
  ... the millions of dollars companies spend monitoring each year and recent advances in leak-detection technology — including an infrared camera that can ...

• Huygens Landed in Mud
  Universe Today - Jan 18, 2005
  They reached this conclusion because the probe's downward-facing High Resolution Thermal Imager camera lens has accumulated material since Huygens landed. ...

• Anti-tank platoon hunts Iraqi insurgents
  Stars and Stripes, D.C. - Jan 18, 2005
  ... The thermal imaging system allows the unit’s gunners to see differences in temperatures between men, machinery and the environment, giving them an added edge ...

• HRH The Duke Of Edinburgh Opens Equine Surgical Suite
  Equine World UK, UK - Jan 17, 2005
  ... for clinical investigation. Techniques included are ultrasonography, endososcopy, electrocardiography and thermography. In support ...

• Developing a Refreshment Towel for Men
  The Cosmetic Site, IL - Jan 12, 2005
  ... little more challenging. We decided to test the use of thermography as a way of visualizing this benefit for consumers. Testing was ...

Here is a selection of recent new threads by IR Community members. Feel free to click the links, see how people have responded, and post your own response if you like.

• Veterinary Thermal Imaging Seminar - March 2005
  Join us at Vetel Diagnostics in San Luis Obispo, California for an informative 3 1/2 day seminar on Veterinary Thermal Imaging, March 10-13, 2005 at the Sands Motel and Conference Center. 1930 Monterey St. San Luis Obispo, CA. 93401, Contact Kelly Martin 800-458-8890
  Our lead speakers include Tracy Turner, DVM, and Jim Waldsmith, DVM.
  
  The tuition is $550.00 per participant and CE credits are offered. You can find a complete course outline at http://www.veteldiagnostics.com
  Please contact Kelly Martin at Vetel Diagnostics for any additional information you require;
  1-800-458-8890, 805-781-7691 or Veteldiagnostics@aol.com

• Mastitis and other bovine applications
  I have been asked to speak at an upcoming dairymans' workshop about the use of IRT for dairy operations. My primary focus will be electrical, pumping, etc., but I'd like to explore the veterinary applications as well. I have about a month to collect information and decide if I even want to cover it.
  
  In the meantime, the dairy advisor is trying to arrange for me to meet with a local vet who owns a couple of small dairies, and we hope to collect some data.
  
  He's got no experience with IRT though, and I'm no veterinarian. I did take the equine workshop at InfraMation 2004 -- but that doesn't qualify me to do this stuff as a pro, but I'm hoping that working with a vet, we can put together an application that may have some value.
  
  Any pointers to more information about the use of IRT with dairy herds would be appreciated.

• A Drywall Question??
  I have a question, If there is moisture under three layrers of drywall can a thermal camera see it.

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 a message board.

Brainteaser of the Month  [top]

Here is this month's brainteaser. Readers who email us the correct identification and explanation of the thermal pattern in the thermogram are entered into a drawing to win a prize 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.

I think this is the first time that NO ONE was able to guess the brainteaser! I'll let Andy Whitcher from Tecpinions Ltd. in the UK explain his thermogram:

"About every four years we shut down our fluid catalytic cracking unit for planned maintenance. Before we can enter the catalyst regenerator vessel for inspection we need to remove all of the remaining catalyst. The catalyst is very similar to fine sand but has a very high heat capacity so it remains hot for a long time. In the regenerator air is blown through the catalyst bed, fluidizing it and burning off the carbon which has been deposited on the surface of the catalyst particles during the cracking reactions of the hydrocarbon feed. The normal operating temperature in the regenerator is 760C (1400F). Most of the catalyst is removed as part of the shutdown procedure but there is always some left in the bottom which has to be removed with a vacuum truck via water coolers. The attached images show the catalyst left in the bottom of the regenerator. As it is sucked out by the vacuum truck the cool surface layer slides down towards the hose nozzle exposing the hot catalyst just beneath the surface. The images were taken six days after the unit had been shut down and the maximum temperature was still around 240C. The large object in the top part of the image is one of the air arms which blows air through the catalyst bed. Three of the air nozzles can be seen at the left hand end of the image.

The most amazing thing about this shot was that the plant had been shut down and purged with cold air for 48 hours and then the vessel had been opened for 24 hours before the image was taken but the catalyst was still at over 200 deg C! The whole vessel is inspected from the man way before an entry permit is issued to make sure there is no catalyst sitting on top of the internal structure. Nobody wants hot catalyst raining down on them. It's another good example of thermography improving worker safety."

Since we have no correct guessers, Andy gets two ITC low emissivity traveling coffee mugs and a big thanks.

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