This article was published in Brandposten n°49.
ANDREAS GAGNAT BOE
andreas.boe@sintef.no@sintef.no
Infrared cameras detect energy in the form of infrared radiation from hot bodies and create a thermal image of the temperature differences. The technology is currently used for many different applications and has in recent years increasingly been used in fire prevention measures. Among other things, infrared cameras contribute to improving fire safety in tunnels, including the Mont Blanc tunnel and the Bjørvika tunnel in Oslo, in that they can detect a fire much earlier than ordinary surveillance cameras.
SINTEF NBL has an infrared camera of type FLIR GF-309. The camera measures temperatures from -40 °C til 1500 °C, it “sees” through smoke and flames and provides useful supplemental information in fire tests and to fire research. The infrared camera provides visualization of temperature distribution on the surface of a specimen, and thermal video sequences show the temperature distribution changes with time. The sensitive optics of FLIR GF-309 can detect temperature differences of less than 25mK.
Applications for the infrared camera in fire testing and fire research
Finding the “hot spots”
Our infrared camera can be used to visualize and detect so called “hot spots”, i.e. areas of a specimen that reaches substantially higher temperatures than the rest of the specimen, during exposure to a fire. Figure 1 is a good illustration of this. Here, the fire resistance of a non load-bearing wall with steel beams and to layers of ordinary plaster on each side is tested in a vertical furnace. The infrared image clearly shows areas where the surface of the wall has elevated temperatures.
The temperature of the “hot spots” can be extracted by analyzing the infrared pictures, either directly during the test or afterwards. This way it is possible to ensure that the hottest areas actually are the ones that are analysed, as opposed to using thermocouples, where the measuring points are predefined before the test. Detecting the local temperature growth is useful for anyone who
develops products and structures that are meant to resist fire. Areas that are particularly exposed to heat can be detected and thus improved in further product development. This is useful information for most product types, for example for passive fire protection, pipes, panels, fire doors, walls, windows, and especially for products with potential weaknesses such as joints and connections… Read more: click here (page 24)
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