Hotspot detection in pressboard manufacturing applications

In the building industry, there is a product used that is commonly referred to as pressboard, also known as chipboard. Sheets of pressboard are typically 1,2 m x 2,4 m in size and are used in the construction of walls, sub-floors and rooftops, as well as underneath real wood veneers for low cost furniture manufacturing. To make this board, the mill chips up logs and all the scraps that are left from making lumber and other wood products. The chips are literally glued together and formed into sheets, which can have different thicknesses, depending on use. To bond the material together, the board is pressed between two heated rollers. The boards are then heated to between 100°C and 200°C.

One problem that can develop with this process is that some of the chips can protrude up through the surface of the board and get so hot that they begin to burn. The hotspot can be as small as 7,5 mm in diameter on boards that are moving about 120 m/min. Spots can be on both the top and bottom of the board. If this is not detected, the board with the burning spot can be placed on a stack with others and moved into storage. This can lead to a fire and even total destruction of the warehouse – all from one single board with a burning spot that was undetected prior to storage.

To detect these burning chips, two ThermoView TV40 thermal cameras can be installed, one to monitor the top surface and a second camera for monitoring the bottom of the board. An area of interest (AOI) is set up to monitor the entire width of the board. When a camera sees a hotspot of 120ºC or greater, an alarm is triggered so the board can be moved off to the side for cooling. After cooling, the board is returned to the stack for storage.

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