· By , R&D and Sales Director, Lenoir-MEC

Removing metals from a material flow: magnetic separator or metal detector?

In brief

  • To remove metals from a material flow, depending on the product, you combine a magnetic separator (drum, head pulley, overband, grate) for ferrous metals, an eddy current separator for non-ferrous metals and a metal detector for protection.
  • On a belt conveyor: overband magnet above the belt, magnetic head pulley at the conveyor head, magnetic drum at the conveyor discharge or under a hopper.
  • In free fall, for powders and granules smaller than 5 mm: grate magnet separator.

Solutions by location

Above a conveyor: overband magnet

The overband magnet is suspended above the belt; it attracts ferrous metals from the flow and continuously discharges them via its own belt into a separate receptacle. It is available with permanent magnets (OVAP) or as an electromagnetic version (OV). Without a self-cleaning system, the APRF fixed permanent sorting magnet and the RD fixed sorting electromagnet perform the same function above a conveyor.

At the conveyor head: magnetic head pulley

The PAP(N) magnetic head pulley replaces the head drum. Its 360° neodymium magnets hold ferromagnetic particles against the belt, carry them underneath the pulley, out of the main discharge zone, and then release them into a collection chute. It is installed in the head position with a minimum drop height of 300 mm.

At the conveyor discharge or under a hopper: magnetic drum

The flow comes into contact with the rotating drum: ferromagnetic materials adhere to its surface and are extracted at the rear, while non-ferrous materials fall by gravity. The TAP(N) magnetic drum extracts items from 1 to 500 mm, 24/7 with no power consumption; the STM magnetic drum separator is available in ferrite (large particles) or neodymium (fine particles).

In free fall: grate magnet

The flow passes through a grate of neodymium magnetic bars; ferromagnetic materials remain captured on the bars, while the cleaned material continues to the outlet. Suitable for particle sizes below 5 mm (flour, sugar, cereals, spices, chemical and pharmaceutical powders), it integrates into hoppers, silos, dosing systems and packaging lines: SGCM grate with manual cleaning for processes with regular stops, SGCP grate for a continuous 24/7 line.

For non-ferrous metals: eddy currents

Aluminium, copper and brass are not attracted by a magnet. An eddy current separator (ED-X, PELICAN) ejects them from the flow after the ferrous metals have been removed. See our guide eddy current separator.

For detection and protection: metal detector

The DDMC frame metal detector creates a uniform electromagnetic field; a metal object passing through it disturbs the field, which triggers an alarm or a reject system. It complements an overband magnet to protect equipment.

Steps to choose

  1. Identify the metals to remove: ferrous (magnetic separator), non-ferrous (eddy currents) or any metal to be detected (metal detector).
  2. Determine how the product is conveyed: belt conveyor, hopper or free fall.
  3. Take the particle size into account: grate magnet for fine products below 5 mm; drum, head pulley or overband magnet for coarser bulk materials.
  4. Choose the location: above the belt (overband magnet), at the conveyor head (head pulley), at the conveyor discharge or under a hopper (drum), in a free-fall duct (grate).
  5. Sequence the equipment: remove ferrous metals first, then non-ferrous metals, and add a metal detector to protect machinery.

Further reading

Guide choosing an overband magnet. Sectors: recycling, mining and quarrying, food processing, chemicals, plastics and wood, glass and ceramics.

Frequently asked questions

How do you remove ferrous metals from a powder?

In free fall, a grate magnet separator retains ferromagnetic materials on its neodymium bars; it is suitable for particle sizes below 5 mm.

What is the difference between a magnetic head pulley and an overband magnet?

The magnetic head pulley replaces the head drum at the conveyor head and captures ferrous metals through the belt; the overband magnet is suspended above the belt and discharges ferrous metals via its own belt.

Does a magnet remove aluminium?

No: aluminium, copper and brass are not magnetic. They are removed with an eddy current separator, installed after the ferrous metals have been removed.

Need help equipping your line?

Describe your product, its particle size, how it is conveyed and the metals to be removed: our engineering department will propose the right solution. Request a quote