|1. Technology of
|3. Chosing the
right metal detector
Metal detectors are totally different than simple magnets. They are not going to trap metals but will detect metal presence in a product stream and possibly reject it making them very useful metal separators for process industries handling bulk solids. This page is essentially focused on gravity fall - free fall metal detectors.
When metal is passing through the metal detector, it will change the magnetic field that is applied by the metal detector. This disruption will allow the detection of the presence of metal.
Metal detectors can be equipped with a rejection. It takes most often the shape of a flap that is opened as soon as the metal detector spots the presence of metal in the product flow. It is the principle used by safeline metal detectors for example.
Each time a diversion occurs, some product is lost, it is important not to have false detection otherwise a lot of losses will be generated.
The following parameters must be taken into account when chosing a metal detector : the product throughput to handle, the location of the metal detector and the sensitivity targetted
Table 1 : Metal Detector design criteria
|Design parameter||Consideration to keep in mind|
|Detection limit||Metal Detector Diameters
|Minimum powder speed||Distance powder point of chute - entry of metal detector|
|Powder max throughput||Ensure that the powder flow is roughly dosed
Metal detector Diameter
|Performance check||Access to Metal Detector entry - introduction of test balls / rods|
|Position in the process||The majority of metal detector are used in gravity fall application but some manufacturers can propose metal detectors designed for pneumatic conveying line for instance|
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