There are a number of advantages for thermography:
1. Monitoring Large Areas
Because thermography uses visual pictures, it is able to capture and compare temperatures over a large area.
2. Monitoring Moving Objects
The technique can also be used to catch moving tagets in real time.
3. Detection of Faults Before Failure
Thermography is able to detect deterioration of a component before it fails by picking up on higher temperature areas that are indicative of a problem.
4. Can be Conducted during Operation
Since thermography doesn’t require physical contact with a systems, inspections can be conducted under full operational conditions, resulting in no downtime and loss of production.
5. Ideal for Hard-to-Reach, Hazardous and Poorly Lit Areas
This non-destructive method can also be used to observe and measure inaccessible or hazardous areas, as well as being able to detect objects in dark areas.
6. Wide Variety of Applications
Thermography is usable for a wide range of applications, from monitoring pipes, shafts and other metal and plastic parts, through to military use and medical applications, such as in physiotherapy.
Despite the many advantages offered by thermography, there are still a few potential drawbacks:
1. Equipment can be Expensive
Although there are affordable options available, the highest quality cameras can be expensive. This is due to the cost of larger pixel arrays (1280 x 1024 as compared to between 40 x 40 and 160 x 120). Fewer pixels mean a reduced image quality, which can make it difficult to distinguish between targets in the same field of view. Less expensive cameras may also have a much lower refresh rate (5-15 Hz as compared to 180 Hz or more). Finally, there can be marked differences in irradiance measurements, with cheaper cameras not being able to effectively take account of emissivity, distance, ambient temperature and relative humidity, resulting in less accurate thermograms.
2. Difficulty of Interpretation
Items with erratic temperatures can be difficult to interpret, although this limitation is lessened with active thermal imaging.
3. Less Accurate than Contact Methods
Thermography is not as accurate as contact methods due to most cameras having a ±2% accuracy or worse in the measurement of temperature.
4. Limited Detection Capabilities
Thermographic methods and instruments are limited to directly detecting surface temperatures.
Thermographic inspection has an array of applications across industry, including engineering uses like plant condition monitoring, preventative or predictive maintenance and process monitoring. Thermography is a good method for maintaining electrical and mechanical systems, such as with the location of thermal leaks or the higher temperatures in overheated regions. It can also be used to inspect refractory lined structures and locate overheating joints and sections of power lines, which are a sign of impending failure.
Common engineering applications include:
Building Inspection
Thermography can be used to find faulty thermal insulation by locating heat leaks in order to improve the efficiency of heating and air conditioning units. An inspection of the building envelope can also find air leaks in window and doorframes. Thermography can also be used to find waterlogged sections of roofing where the membrane has admitted rainwater that then becomes trapped between the layers of the roof.
Plant Maintenance
Thermography can be used for plant maintenance procedures, collecting thermal images of relevant machine parts to detect potential faults for repair.
Electrical Wiring Maintenance
Electrical wiring uses physical connection between cables, connectors and mounting studs. High quality electrical connections involve low electrical resistance between the various parts. As the quality of a connection degrades, the amount of electrical power that dissipates increases, in a process called ohmic heating, which can be picked up as increased heat by a thermal imager.
Locating Energy Loss
Lost energy can be a drain on any facility, and thermal imaging can help eliminate this. For example, excessive steam consumption and defective steam traps that heat downstream condensate return piping can easily be located by an infrared imager. Thermography can also find other wasteful energy losses, such as defects in refractory blocks in kilns, boilers or furnaces.
Bridge and Paved Surface Inspection
Thermography can also be used to inspect concrete bridges and other paved surfaces, locating voids and delaminations between the layers of material. Any air or water in these interlaminar spaces affects thermal conductivity and can therefore be found with a thermal imager. This can even extend to finding hidden rust, cracking, blistering and other defects between paint layers.
Thermography has a wide range of applications across industry – from non-destructive testing to military night-fighting applications. As with many techniques, there are some drawbacks, but these are outweighed by the versatility and many advantages of this NDT method.