Metal detectors, as taught in tertiary institutions, may still be over emphasized in the HACCP doctrine in a manner which overshadows the relative importance of Ultra High Intensity Rare Earth Magnet capabilities in metal fragment extraction. This is specially so since the availability of RE80™ / RE80™HT magnetics which can present 10-12,000 gauss to the product at critical locations.
Of course only a metal detector will reliably indicate the presence of stainless steel or brass bolts, stainless steel nuts and washers, copper wire and aluminium foil – this is where the metal detector really works well.
Although theoretical indications on 1mm spheres of iron can be achieved in ideal circumstances, it should be remembered that 316 stainless steel is a different story. The shape of the stainless steel piece can make it difficult to detect at certain orientations. In practice, this can sometimes mean detection of only 3mm or larger particle size. This can mean fine wires or other dangerous smaller fragments remain in the outgoing products.
Stainless steel fragments and wires of 3mm size and under are usually work hardened. This means such fragments can be extracted magnetically along with other contaminants such as magnetic stone.
Many respected organisations now share the view that it is of first importance that Ultra High Intensity Magnets should be installed upstream of high sensitivity metal detectors and X-ray units. Both are equally important.
Without efficient magnets much fine ferrous metal and fine magnetic fragments will be getting past even the most sensitive metal detectors. Without efficient magnets, larger pieces will be detected by the Metal Detectors but excessive product rejection can occur where the detector is properly calibrated. The causes of rejection in these circumstances are often difficult to locate in bags or bins of bulk product. Consequently it is much better to pull ferrous and other magnetics out first with efficient RE80™ or RE80™HT magnets conforming to HACCP International Food Safety Standard 0909MAGSEP 1-2010. Small fragments can cause product recall.
It is accepted that metal detectors work much more efficiently in both wet and dry product when fine magnetics have been scalped out at a moderate but adequate distance upstream of the detector. When such installations have been implemented customers have reported that their metal detectors now hardly ever register a detection!
Meanwhile, technology advances on both fronts…Click here for more information about MAGNATTACK™ GlobalClick here for related articles and news on magnetic separation
Sign up for Screening & Separation E-Updates
Recent Screening and Separation e-newsletters
Read our last “Screening and Separation” e-newsletter campaigns here: