The work we do as thermographers has immense value; I don’t mean to imply that the world would stop turning without us, but thermographers do a great deal to have it turn more smoothly and efficiently! The disastrous situation in Japan reminds us of how vulnerable the complex systems and machines we have grown to rely on really are. Of course, some calamities, like those resulting from the huge earthquake and associated tsunami, cannot be avoided. Thermal imaging, however, has helped to prevent many failures in our infrastructures and reduce the damage caused by many others.
The workhorse application of thermography is still the inspection of electrical systems. If the thermographer is skilled, such problems (which occur frequently) are fairly easy to locate. A full analysis of the root cause and an accurate understanding of the failure cycle are often more complex—even for those with a sound foundation of understanding of the parameters involved. For example, abnormal heating leads to failures. Sometimes these are merely an inconvenience, but often they are much more costly and occasionally catastrophic.
Once a problem is located, too often people simply ask “How hot is it?”—failing to realize that not only are the issues almost never that simple, but also that the measured radiometric temperatures are typically less accurate than the ±2% the imager is capable of delivering. The old bugaboos of emissivity and background temperature raise havoc for even the best of industrial thermographers. And, of course, we are often not looking directly at the surface being heated by electrical resistance; that is typically a subsurface phenomenon that is warmer, often much warmer, than the surface we observe through our imaging system.
A great deal about both the temperature and the severity of damage depends on the present load on the system. With light loads, a problem may be missed because the surface temperatures are below the threshold of detection. The question “Will loads increase?” is a much more useful question to consider because an increased load will result in more heat-related damage.
The greatest value of thermal imaging is simply to help us find these problems! Whether a faulty connection is barely warm compared to other phases, or is literally smoking hot, knowing it is there is fundamental. Other tests, measurements and analysis can then help us understand the next appropriate steps.
An excellent discussion of a fairly complex electrical problem recently took place on the Snell message-board/forum, IRTalk. It clearly drove home many of these important issues. The thermographer who posted the image managed to locate the hotspot, but then turned to others, both in his company and on the message-board, for help in understanding the root cause.
Finding experts who truly understand both the value of thermography as well as the very real limitations within which we work are not easy to come by. On top of that, thermographers who are capable of seeing all the elements of the larger analysis of a finding are even more crucial to this field. Many so-called “experts” will either jump to conclusions, or dismiss a finding as “not that bad.” Thermographers need to build their own support network and then educate the non-thermographers they work with. Only with that kind of support can their findings actually make the difference we all know they can—improving reliability and safety while reducing operating costs.
John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner