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Thermographic Inspection

Thermography is used to detect thermal defects and air leakage in buildings. It also measures surface temperatures by using infrared video and still cameras. These tools see light that is in the heat spectrum. Images on the video or film record the temperature variations of the building's skin, ranging from white for warm regions to black for cooler areas. The resulting images help the auditor determine whether insulation is needed. They also serve as a quality control tool to ensure that insulation has been installed correctly.

Infrared imaging (thermography) is a non-contact optical method where an accurate two- dimensional mapping of steady or transient thermal effects is constructed from the measurement of infrared energy emitted by the target. Recent advances in infrared technology, specifically development of high-density imaging sensors have opened a new level of applications unreachable prior to the availability of this technology. Real-time infrared image acquisition and processing allows implementation of advanced thermographic test methods. One of the methods selected for the coating inspection is an active or transient thermography. This method is dissimilar to the conventional thermographic methods in the utilization of time-dependent heating (or cooling) of the target.

Depending on the type of defect and thermal characteristics of a target, an external heating or cooling is applied in the form of the short energy pulses. This energy pulses can be generated by using quartz lamps or hot-air heating. Thermal perturbation is then followed by a differential time-resolved infrared image analysis. Coating defects such as blistering and sub-surface corrosion spots, can be detected in infrared images as a result of the differences in the thermal diffusivity of the defective and non-defective areas. Often a fraction of a degree is adequate for reliable detection and identification of the thermal signature of the defect. The same technique can potentially be used for rapid assessment of the variations in the coating thickness. (reference)

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