Whether sourced as virgin wood from log stock or from recycled wood (e.g. pallets), shredded wood will contain both ferrous and non-ferrous metals. This is in a variety of forms from nails, aluminium hinges, and even bullets.
After a primary stage of shredding, most of such metal contamination is liberated to such a degree that it can be separated. Some metal will be free, whilst other metal may still be embedded in the wood. Before the shredded wood enters the next stage of shredding, such metal contamination is removed.
Ferrous and non-ferrous metal is separated using a combination of Magnetic Separators, Eddy Current Separators, and Metal Detectors.
- Permanent Overband Magnets and Electro Overband Magnets – these magnetic separators sit over conveyors and lift larger ferrous metal contamination out of the conveyed shredded wood. Multi-pole designs reduce the risk of belt piercing from sharp pointed objects such as nails;
- Drum Magnets and Pulley Magnets – separation performance improves as the ferrous metal gets close to the magnetic field. The Permanent or Electro Drum Magnet or the Pulley Magnet provides enhanced ferrous metal separation, especially of smaller tramp ferrous metal. Due to the abrasive nature of metals such as nails, Drum Magnets are commonly supplied with manganese steel wear wraps;
- Eddy Current Separators physically and continuously ejects non-ferrous metals (eg. aluminium door handles and hinges) out of the flow of the shredded wood;
- Metal Detectors, mounted under and over conveyors, provide a final check prior to entering a shredder, at the stage immediately being board pressing, and to check the final finished board, usually prior to cutting;