Infrared technology is one of the most important tools that can be used in a successful predictive maintenance program. This technology is not just for finding abnormalities with electrical components and equipment based on elevated temperature; it can also find potential problems based on lower-than-normal temperatures.

The capabilities of an infrared imager are limited to the imagination of the thermographer. There are many potential problems that can be identified with infrared for which you may not be aware.

Locating material buildup in baghouse hoppers, coke gas lines and flue gas ducts are a few instances where you are not looking for the hottest temperature, but instead, the coolest. As long as there is a differential in temperature between the buildup of material and the gas passing through the equipment, you should be able to visually see the material through the lens of the infrared camera. If the differential in temperature is small, avoid sunny days when the selected equipment is located outdoors to avoid errors in the temperature readings from reflections and solar gain.

The example above is a baghouse in a steel mill. It is collecting the emissions from a ladle refining unit. There is a 20-degree Fahrenheit differential temperature between (Sp1) purple (the material buildup) and (Sp2) white (the gas stream).

The solid materials’ presence is quite noticeable as witnessed by the lower temperature in the bottom section.   

This example represents a large-diameter duct elbow transferring gas and metal particulates from an EAF furnace to a baghouse. There is a 30-degree Fahrenheit temperature difference between (Sp1) purple (the material buildup) and (Sp2) white (the gas stream), demonstrating considerable accumulation of debris in the duct.   

The two examples clearly show that solid material is present in both. This not only restricts the air flow through the equipment and can affect production, it also adds considerable weight to the structure that it may not be designed to withstand.

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