Thermography

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. INTRODUCTION

1.1. About the Thermography
Thermal or infrared energy is an energy, not visible because its wavelength is too long for the sensors in our eyes to detect. It is the part of the electromagnetic spectrum that we perceive as heat. Unlike visible light, in the infrared spectrum, everything with a temperature above absolute zero emits infrared electromagnetic energy. Even cold objects such as ice cubes, emit infrared radiation. The higher the temperature of the object, the greater the infrared radiation emitted. The Infrared camera allows us to see what our eyes cannot.
All objects, cold or hot, radiate heat in the form of infrared energy. As an object increases in temperature, it radiates more energy, and the wavelength gets shorter. Infrared radiation, visible light and ultraviolet light are all forms of energy in the electromagnetic spectrum. The only difference is their wavelength or frequency.



2.1.1. What is Thermography?
Infrared Thermography is the technique that uses an infrared imaging and measurement camera to "see" and "measure" invisible infrared energy being emitted from an object.


Thermography is a non-contact, non-destructive test method that utilizes a thermal imager to detect, display and record thermal patterns and temperatures across the surface of an object. Infrared thermography may be applied to any situation where knowledge of thermal profiles and temperatures will provide meaningful data about a system, object or process.

2.1.2. What principle used in Thermography?
Since infrared radiation is emitted by all objects based on their temperatures, according to the black body radiation law, thermography makes it possible to "see" one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature; therefore thermography allows one to see variations in temperature. Radiation also originates from the surroundings and is reflected in the object, and the radiation from the object and the reflected radiation will also be influenced by the absorption of the atmosphere.

If the temperature an object gets hot enough however, above 525°C the energy from that object will radiate energy in the visible spectrum and we will see it. This is when we see an object like the burner on an electric stove “glowing” red. In fact any time an object will emit or reflect energy in the same frequency of our eyes we will see it.



Where Thermography is used?
Thermal imaging photography finds many uses. For example, firefighters use it to see through smoke, find persons, and localize hotspots of fires. With thermal imaging, power line maintenance technicians locate overheating joints and parts, a telltale sign of their failure, to eliminate potential hazards. Where thermal insulation becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating air-conditioning. Thermal imaging cameras are also installed in some luxury cars to aid the driver. Some physiological activities, particularly responses, in human beings and other warm-blooded animals can also be monitored with thermographic imaging. Cooled infrared cameras can also be found at most major astronomy research telescopes.



Benefit of Thermography?
Thermography is a non-contact, non-destructive test method. It is capable of catching moving targets in real time. It finds defects in shafts and other metal parts. It is used to take measurement in areas inaccessible or hazardous for other methods. It find deteriorating components prior to failure. It helps compare temperatures over a large area. When compared with other classical nondestructive testing techniques such as ultrasonic testing or radiographic testing, thermographic inspection is safe, nonintrusive and noncontact, allowing the detection of relatively shallow subsurface defects under large surfaces and in a fast manner.



THERMOGRAPHIC TECHNIQUE
The basic principle of thermography is that all types of surfaces will emit some degree of heat. The thermographic equipment will detect heat which differs from the temperatures in the surrounding area of a surface. These higher temperatures might be an indication of a potential malfunction of the scanned object i.e. faults in electrical circuitry or overheating of bearings in mechanical equipment, i.e. pumps, motors, compressors, etc. Thermographic imaging can detect insufficiently insulated hot spots in engine rooms, which create a large fire risk.