Infrared Thermography
What is Thermography?
Types, principles, working, advantages & limitations.
Thermography (passive) is a thermal imaging method when the operator or engineer is obtaining an image of the heat distribution over the surface of an object. The usual method is to use a special camera made of several infrared sensors (an infrared sensitive detector) and a lens which transmits infrared radiation.
Thermographic cameras usually detect radiation in the long-infrared range of the (roughly 9,000–14,000 nanometers or 9–14 μm) and produce images of that radiation, called thermograms. Since infrared radiation is emitted by all objects with a temperature above absolute zero 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 us to see variations in temperature.
As a result, thermography is particularly adopted to the NDT (Non-Destructive Testing) industry to conduct investigations with.
An infrared survey consists of many images of the exterior of a building, using a camera that can take images in the infrared spectrum. These images represent the temperature of the surface of the building. Anomalies in the exterior temperature of the building are noteworthy. Anomalies, like small leaks related to aging weather-stripping or caulking between stone panels, will show up as localized inconsistencies in an infrared survey. This method is frequently used in a Reliability Engineering World.
Infrared surveys generally are best performed in the evenings, but surveys conducted both evening and mornings are even better so that a comparison between heat transfer into the building (sunrise), and heat transfer out of the building (sunset), can be made. The time of year and outside temperatures affect the results of infrared surveys, as well as whether the building is climate controlled or not.
The images below stands for an example of a rooftop QC survey. The first image shows proper water/moisture sealing installation, while the second image indicates moisture affected hot spots. Warmer area(s) typically are a sign of retained moisture.
Advantages:
Trapped Water imagery
Building efficiency evaluations
Verifications, mechanical rotating parts or sealings
