Content

• What is Infrared Thermography Testing?
• Variants in Thermography
• Benefits of Infrared Thermography Testing
• Applications of Infrared Thermography Testing
• Conclusion

What is Infrared Thermography Testing?

Thermography is the process of using an infrared camera to look for abnormally hot or cold areas on a component operating under normal conditions. It is a viable non-destructive evaluation technique for the characterization of corrosion in metallic materials and is the simplest of all thermal inspection techniques.

There are several applications of Infrared thermography. Thermography is useful for the detection of corrosion/erosion damage in plants operating at elevated temperatures. In addition, it can be used to check for fouling or internal plugging of piping systems and to check the quality of refractory linings. It can also be used for leak detection, composition changes and disbonds in laminates.  Using thermography, the temperature of objects can be made visible. It is a rapid, noncontact, wide area inspection technique that is easy to interpret and that is not significantly sensitive to material curvature. Thermography is a technique that can be applied to most areas of plants, but which is particularly suited to plants operating at elevated temperatures. However, it is a surface technique, and it cannot be used to look through thick layers of lagging for defects in the underlying structure.

In Medical Science, Thermography is a test that uses an infrared camera to detect heat patterns and blood flow in body tissues.  Digital infrared thermal imaging (DITI) is the type of thermography that’s used to diagnose breast cancer. DITI reveals temperature differences on the surface of the breasts to diagnose breast cancer.  The idea behind this test is that, as cancer cells multiply, they need more oxygen-rich blood to grow. When blood flow to the tumor increases, the temperature around it rises.  One advantage is that thermography doesn’t give off radiation like mammography, which uses low-dose X-rays to take pictures from inside the breasts.  Thermography is usually referred to as infrared thermography or thermal imaging. 

Variants in Thermography

• Passive: The features of interest are naturally at a higher or lower temperature than the background. It has many applications such as surveillance of people and medical diagnosis.
• Active: An energy source is required to produce a thermal contrast between the feature of interest and the background. The active approach is necessary in many cases given that the inspected parts are usually in equilibrium with the surroundings.

What are the benefits of Infrared Thermography Testing

The main benefit of infrared thermography testing over the destructive testing techniques is that large areas can be scanned fast and with no need to be destroyed during testing. This results in major savings in time, people, work and machinery.

In addition, there are other benefits of infrared thermography over the other non-destructive techniques. The infrared thermographic device is risk-free, as it does not emit any radiation; it only records the infrared radiation emitted from the material that is under assessment. Moreover, infrared thermography is an area investigating technique, whereas most of the other non-destructive methods are either point or line testing methods. Furthermore, infrared thermographic testing may be performed during both day - and night - time hours.

Another benefit of infrared thermography is that it is also used in Condition Monitoring. Infrared Thermography in Condition Monitoring helps in the easy detection of - heat-related problems, thermal anomalies, mechanical issues, and much more.

Thermography, due to the fact that it uses infrared technology it is not possible to penetrate in extended depths. That of course is one of the main limitations of the technique. Finally, environmental conditions also play an important role on outdoor infrared thermographic surveys utilising the passive approach (i.e. cloud cover, solar radiation, wind speed).

Thermography inspections utilize the surface temperature distribution of an object. If the surface temperature is uniform, with no temperature variations, there is no indication of a problem. As a result, for some applications it has limitations.

Some key highlights or benefits of using infrared thermography testing-

• Inspection can take place during production.
• Inspection is quick and does not require physical contact.
• Results are recorded digitally.
• Costs are relatively low

Applications of infrared thermography testing

The infrared technology offers fast measuring and precise temperature measurement that is crucial for the research and testing applications in the industrial and academic laboratory. Researchers have reportedly used infrared camera, infrared thermometers, and multi-color pyrometer to capture the temperature of individual particles in coal combustion reactor in an attempt to understand the transient phenomena behind combusting coal particles to practically design a new low-emission burner technology. These infrared technologies can capture the transient changes that occur in milliseconds which is unable to be measured with conventional thermocouples. In industrial environments, it is a qualified and approved sensor technology to measure, monitor and control process temperature.

1. Injection Moulding: Temperature determines the quality of the finished products in injection moulding or 3D-printing applications. Getting the temperature correct is crucial to ensure that the manufactured products are free of defects. This particularly holds true for manufacturing of automotive products where tiny dents or defects are not tolerated. The thermal imager has been used in an online system to measure the surface temperature distribution of the products. It can be integrated with PLC system to automatically reject the assemblies if the measured temperature is not within the standardized range.
2. Manufacturing: In the manufacturing industry, temperature is one of the parameters that greatly affects the quality of the manufactured products. For example, the quality of the finished glass products highly depends on the temperature of the molten glass. A special thermal imager for glass temperature monitoring has been developed for this measurement purpose. In the metals industry, monitoring the temperature of the molten metals is essential to correctly maintain the process temperature during casting. This requires a special infrared sensor that offers the suitable spectral range and fast response.
3. Condition Monitoring: Thermal imaging camera is one of the most sought-after technology as a preventive maintenance tool in industrial process applications. It can be used for condition monitoring applications to detect hot spots on the crucial process equipment such as pumps. Hot spots generally indicate problems in the machinery which could be caused by loose screws, wear of bearings or overheating. Early detection of problems allows the repair and maintenance of equipment before a catastrophic failure occurs which may save the company lives and money

Conclusion

Infrared thermography is a fast, clean and safe technology that is used in a wide variety of applications.  The principles and essential theoretical background in temperature measurement and non-destructive testing have been reviewed. This background information is provided to help the dissemination of these technologies and to assist beginners in a better understanding of the subject. Moreover, recent work on these topics has been reviewed and discussed.

Infrared thermography has experienced a great evolution in a relatively short time. Important improvements were achieved in different fields. However, there is a variety of limitations that need to be taken into account. Infrared thermography is highly dependent on the sensor selection and the experimental setup. It may be affected by the instrument and by the environment. These problems can be minimized, but only with adequate setup and testing procedures, which mostly depend on the operator's skill.