In the field of the materials recycling, such as wood, plastic, glass, metals and non-ferrous, etc., in the plants for recovery of waste and scrap, as in the MSW selection plants and WEEE, in those of inert crushing or minerals grinding, the overbelt separators (SM) find a large use for the extraction and recovery of ferromagnetic intrusions, present in the inert process material.

Principle of operation:
These machines, defined as overbelt (or overband), are essentially constituted by a magnet, around which a belt (called extractor belt) rotates. The magnet attracts the ferrous material that is transported by the belt in an appropriate discharge zone.
Based on the requirements of the separation process, they can be installed transversely or longitudinally at a certain height over the material flow.
The machine will therefore be suspended above the material to be separated, so that it is possible to adjust both the distance between the magnet and the conveyor belt, both the inclination of the separator.

The SM separators are distinguished by the type of permanent magnets used:

• Ferrite: very widespread magnet, is able to withstand high temperatures (up to 300°C) and generates a deep magnetic field.
• Rare earths (Nd Fe Bo): with high magnetic induction and very high coercive force, it is for these reasons most appropriate for the separation of small dimensions materials or materials incorporated into the inert material (eg. wired glass).

In many areas and working conditions, the permanent magnetic separator is more convenient for the following benefits reported:

• High power savings, because the permanent magnet does not require energy;
• Magnetic performance constant over time, even in continuous use, since there is no Joule effect and no heating is caused.