Services & Maintenance: Infrared Technology For Safety And Operations
By L. Terry Clausing, P.E.
Published in the February 2007 issue of Today’s Facility Manager
Today’s facility managers are constantly faced with a barrage of maintenance based problems and an even greater barrage of people trying to sell them things to make their jobs easier. Despite the hype surrounding some more dubious products, infrared cameras are extremely helpful for general maintenance tasks. Their greatest benefit is for troubleshooting problems—particularly those that are difficult to isolate and analyze.
It is extremely important for facility managers to understand several key elements in order to receive the greatest benefit from infrared cameras and the people who know how to operate them accurately. The equipment—whether a digital multimeter (DMM) or an infrared camera—is merely a tool. In hands that are not properly trained and skilled, this equipment is of little value to anyone. But in the skilled hands of someone who is trained and qualified, an infrared camera is an absolutely indispensable tool for the facility manager.
Using Infrared Cameras
Most facility managers have seen infrared cameras, whether they know it or not. For instance, the annual inspection (yes, annual,according to NFPA standard practice 70B) of an electrical power distribution system is typically conducted with an infrared camera.These inspections are conducted by companies that specialize in examining electrical gear and have certified Level I or Level IIthermographers on staff.
The American Society for Nondestructive Testing (ASNT) publishes recommended practices for personnel certification for thermographers. A Level I thermographer has completed at least 32 hours of classroom training and at least 210 hours of thermography experience under the direction of a Level II thermographer. A level II thermographer has completed an additional 32 hours of classroom instruction and at least 1,260 hours of work experience.
Why Training Is Necessary
Nearly every facility manager has purchased one of those simple and inexpensive infrared thermometers. Most members of the maintenance staff have one somewhere in their toolbox. Unfortunately, one of the first things most learn about these inexpensive devices is that they generally indicate when something is hot but seldom read the correct temperature.
In fact, neither infrared temperature sensors nor infrared cameras read temperature; they actually read radiance. Infrared thermometers, like infrared cameras, read the accurate temperature when the device observes a black body—an object with an emissivity rating of 1.
According to the downloadable online glossary of terms,“Infrared emissivity (or emittance) is a measure of the ability of a surface to shed some of its heat (in the form of infrared radiation) away from the surface. High infrared emissivity helps keep surfaces cool. Metallic surfaces have a low infrared emissivity.”
Temperatures for metal surfaces are especially difficult to measure, because their emissivity is often very low. Often, a shiny steel surface that is actually 200 degrees F will appear to be only 98 degrees F when analyzed by an infrared instrument.
This kind of misunderstanding may lead untrained users to think infrared devices are flawed or that the technology just doesn’t work very well. But in trained hands, infrared technology works exceptionally well. The difference is in the knowledge of the person using it.
Valuable Infrared Applications
While facility managers are inherently familiar with the importance of the electrical power distribution inspections, most are less familiar with the details associated with the specific task. Despite general safety rules, it is essential to remove all kinds of protective panel covers during an electric power distribution inspection.
Trained professionals will know that infrared cameras cannot see through the covers, whether the panels are metal or some other substance—even an opaque one. While these covers shield the most critical connections, they make it difficult to inspect those same connections.
Many facilities use overhead buss with buss plugs that feed powerto critical equipment. Although it is essential to open electricalpanels during inspections because infrared can not see through themetal, it is economically impractical to open each buss plug for adirect infrared inspection. Instead, the prevalent practice is for atrained thermographer to inspect this equipment from the ground.
Inspecting buss plugs requires a higher level of training, because subtle hot spots on the exterior surface of a buss plug are serious indications of internal problems. Opening the buss plug may reveal a condition far more critical.
Another area where facility managers often have serious problems, and where infrared cameras can play a valuable role, is locating leaksand water laden insulation in roofing systems.
During daylight hours, the roof absorbs thermal radiation from the sun. At dusk, the roof then begins to cool. The insulation in the roof also heats up during daylight hours, but when the sun goes down and the roof begins to cool, the areas with wet insulation cool more slowly than the dry areas.
Consequently, facility managers can use an infrared camera toobserve and differentiate the wet areas from the dry areas. In a thermal image of the roof, the dry areas would be indicated by blue coloration (cool and dry) while the wet areas show up as yellowish red (warm and damp).
Like electrical inspections, infrared roofing inspections require knowledge and training. Infrared cameras do not see moisture; they only see the thermal pattern that usually results from the presence of moisture.
When examining roofs, it is essential for professionals to have an intimate understanding of the roofing construction materials in orderto interpret the infrared image properly. Furthermore, all infrared findings should be verified with core samples or other tests tovalidate the results. [Read “Shelter From The Storm” by Jillian Ruffino online for more information on related roofing matters.]
Facility professionals who need to know more about infrared inspections of electrical equipment and building roofs can tap resources provided by ASTM International. This organization (originally known as the American Society for Testing and Materials) publishes several standards that clearly explain how these kinds of inspections should be properly conducted.
One such document, ASTM E1934, offers guidance on inspecting electrical and mechanical equipment. Another example, ASTM C1153, provides an excellent standard practice for inspecting roofs. Both of these standards provide valuable resources to help ensure that infrared inspection work is done properly.
Infrared cameras can be successfully used to locate missing insulation in building walls and even freezer walls. Motors and gearboxes can be monitored to locate failing equipment prior to failure. And infrared cameras can even be used to screen people for fever in the event of a pandemic. Obviously, the potential for this technology is tremendous and can be a valuable asset for knowledgeable facility professionals.
Clausing is president of Drysdale & Associates, Inc and TrendFormers Infrared Inspections of Cincinnati, OH.