Understanding Infrared Thermography Reading 3

Steam traps are special valves that automatically cycle open and closed to
remove condensate from sections of steam process lines. If the
thermographer has prior knowledge of their normal operation, steam traps
can usually be observed thermographically to determine if they are operating
properly. Without this prior knowledge, using infrared thermography for steam
trap diagnostics may be confusing and misleading. In the image sequence
shown in Figure 5.7, the various operating conditions of the valve (top) result
in clearly detectable thermal pattern changes. The thermal appearance of the
steam trap (bottom) remains essentially the same in all three images
Blockage of any fluid transfer line can be simple to detect thermographically if
the fluid temperature is sufficiently hotter or cooter than ambient. If not, there
are more sophisticated approaches that have had documented success. For
example, the injection of uniform transient heat will often result in transient
temperature differentials at the blockage site because of the difference in
thermal capacity between the fluid (in liquid form) and the solid blockage.
Heat injection techniques are discussed in greater detail in subsequent
sections.
Charlie Chong/ Fion Zhang