Email question received;

I have some chimney stacks to inspect with thermography. Both stations are thermal coal. One station has two stacks that were built-in 1976-1980. The two stacks are 177 metres high. The other station has one stack and was built-in 1992/93 and is 250 metres high. I have been asked to identify areas of temperature difference on the exterior of the stacks. What problems can I expect to encounter?

 

Answer;

They are more than likely brick or concrete chimney stacks in an old coal station. This is a relatively easy application, as the emissivity will be high. You need to watch for solar loading/ strong sunshine, this may mask problems. You are best doing this at night, or early morning when the sun effect is minimised. Also avoid inspecting if it has rained in the previous 10-12 hours, as evaporative cooling could be a problem.

Viewing angle may be an issue for you too. At very sharp angles the emissivity will drop substantially and the chimney will become much more reflective. Avoid standing too close and image all the way around the stack.

Other than that it should be no problem.

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