Gravity-fall metal separators are typically installed in vertical pipes where powder falls freely. The material passes through a detection coil in a steady stream, and when a ferrous or non-ferrous metal contaminant is detected, a flap or discharge valve diverts a small portion of material containing the contaminant. Unlike conveyor-belt systems, they do not depend on a spread layer of product, making them suitable for free-flowing bulk materials such as flour, starch, additives and plastic granules.
When selecting a unit, first confirm material characteristics: particle size, bulk density, moisture content and flowability all affect falling speed and detection stability. Sticky or caking powders may need vibration feeding or anti-blocking features. Sensitivity and rejection method should also match, since too large a reject volume wastes product while too small a volume risks missing contaminants. Contact materials, sealing rating and ease of cleaning matter for food and pharmaceutical lines.
Installation and maintenance also affect performance. The unit should sit close to downstream packing or storage to limit recontamination after rejection, and the pipe should stay vertical with no sharp bends to keep flow stable. A regular verification schedule using test pieces helps confirm detection and rejection are reliable, and sensitivity trends should be logged. For plants running multiple products, discuss parameter adaptation with the supplier so the unit keeps stable detection when products are switched.