A high frequency current is induced in the surface when the billet or bar runs through a circular coil connected to a HF generator. The induced current heats the skin of the surface. Defects open to the surface forces the current to go beneath the defects and extend the length of the induced current path. A local rise in temperature Δt corresponds to the length of the detour. The Δt is therefore also equal to the depth of the defect. Highly sensitive infrared scanners record an image of the surface temperature. The temperature image is analyzed by signal processors detecting, measuring and comparing the local Δt with the selectable and variable depth thresholds. Defects deeper than the depth threshold are marked true to position by paint guns.
The IR scanner is the most important component in Therm-O-Matic®.
The line scanner is specially developed with functions only required for this application. The components are according to military specfications with high reliability. More than 100 units of the IR-scanner have been built. Some of them have been running continuously for more than 25 years, and still operates with the same performance today. We are very proud of the track record of our scanner.