Stray Contamination Detection in Refractory Brick

I would suggest at the point where the raw materials are mixed or even before,they could be passed over a magnetic seperator or run through a hammer mill or a vibration table with smaller mesh screens to filter out debris.

Do you have any idea where the contaminants come from. Is it possible that they might not be from the raw materials, but from normal wear and tear on the machinery? What size are the bits of metal that end up in the bricks?

How many defects/1000? a conveyor mounted metal detector from Mettler Toledo [ Safeline ], can be tuned to detect different metals & kick off the bad ones. the way these things work, is the smaller the detector window the more accurate. the question then becomes, can you get results without having to run them single file through the window & raising the breakage rate. A camera operated sorter could be also be used.

Infrared cameras/linescanners can also be used to detect some contaminants and with software, trigger a mechanical dump gate, etc. This works for granular materials where the contaminant's heat storage capacity (usually proportional to density) is significantly different from the product's heat storage capacity. The point of inspection/rejection would need to have particles spread thin. Either rapid heating or cooling will reveal the contaminants to the infrared camera. Sometimes an infrared linescanner rather than camera is better because it has a wide field of view and software is already available that can trigger the mechanical rejection device. This would need to be done before pressing the bricks so that granular material could be spread thin enough to "see" one side of all particles. Obviously, magnetic separation is best if contaminants are magnetic, but this is a workable alternative. Best to find the source and eliminate it! B.W. West, P.E.