Thermal imaging is the process of recording pictures of the patterns or variations of heat radiated from a surface of a device or other object (machine face or component, wall, roof, street, electrical component, etc). Thermal imagers do not see through things as shown on the telly, they only “see” the heat radiation resulting from variations of temperature on the surface. It is up to the thermographer to understand the underlying device or component construction, the affect on heat transfer and the resulting surface heat or thermal patterns in order to properly interpret the image.
The graphic below gives an idea what is going on physically:
Infrared Imaging with associated image confirming techniques has been documented repeatedly to be the fastest and most cost effective methodology for the assessment of roof or electrical system overall condition for targeted and timely repairs . It is also a major tool in the location and assessment of interior moisture or water leakage as well as energy loss through air leakage or poor insulation.
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For roof inspections we use a number of techniques and instrumentation both intrusive and non-intrusive to verify or confirm the thermal imaging. Intrusive testing includes both core removal and examination as well as the insertion of moisture meter probes sensitive to electrical conduction in water. Non-intrusive testing includes both capacitive and nuclear gauge moisture metering. Similar intrusive and non-intrusive techniques may used inside the building for moisture inspections
Crew size depends primarily on safety requirements and secondarily on the complexity or demands of the task. For roof work at night, a minimum of two are required for safety, roof marking and data recording. For electrical work, an additional person is required to open the panels and provide fault severity information for the installation. For energy and interior moisture work, generally a single person, the thermographer, is sufficient.
With the exception of roof work, our infrared inspections are performed during the day. Roof inspections are routinely performed at night and during the day in order to observe the roof as it cools and/or as it warms (it is a “transition game”). The length of time for any job depends on several factors including job complexity and distance from home base in Raleigh. Infrared roof inspections are highly weather dependent as we require dry surfaces in addition to solar heating for surface warming and clear night skies for membrane cooling.
Time investment for roof work varies with the roof size, number of sections, roof equipment density, age and construction type. For electrical jobs, the time factors include the number of devices or panels to be opened as well as the arc-flash hazard. For moisture and energy work, the size of the building or the extent of the moisture intrusion are major factors.
Firm quotations are provided on request and after we gain a good understanding of the factors that will affect the site inspection, report write-up and post-report consulting time required. We will also provide verbal ball-park pricing prior to written quotations as necessary.
Radiation is one of the three methods of heat transfer as seen in the graphic below. In the business of thermography, we need to be aware of all three as they affect the images that we interpret.
Thermal or heat energy is conveyed from a point of higher to relatively lower energy level in three different but partially related ways:
Thermal Imagers are sensitive to the RADIATION from a surface that is proportional to the energy of the surface or the temperature of that surface. A thermal imager display may show a warmer device or area as lighter in color or a different color than an area that is cooler.
Infrared radiation is part of the electromagnetic spectrum as shown in the graphic below:
The frequency of occurrence or distance between waves (wavelength) of thermal energy radiation occurs below that of visible light and is therefore invisible to the human eye. The band of frequencies or wavelengths in which thermal energy radiation occurs is called infrared as can be seen in the vivid illustration above that contains the entire electromagnetic spectrum (infrared = below visible red). The Thermal Imager is designed to “see” thermal energy radiation in the infrared region of the electromagnetic spectrum.