When sourcing a gravity-fed metal detector, you must prioritize detection sensitivity for both ferrous and non-ferrous metals, including 316 stainless steel. Look for systems featuring Digital Signal Processing (DSP) to minimize 'product effect' caused by moisture or salt. Ensure the aperture size matches your pipe diameter to maintain flow rate, and verify the reject mechanism speed (e.g., cowbell or diverter valves) to ensure contaminated material is isolated without stopping the entire production line.