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

Choosing an overband magnet: permanent magnet or electromagnet

Permanent magnet or electromagnetic overband magnet?

In brief

  • An overband magnet is a magnetic separator suspended above a conveyor: it continuously extracts ferrous metals from the material flow and discharges them via its own belt.
  • The permanent magnet overband (OVAP) generates its field without consuming electricity for the magnet; the electromagnetic overband (OV) requires a continuous power supply but delivers greater separation power.
  • The choice depends on the conveyor width, the weight the structure can support (1.4 t for an OVAP, up to 13 t for an OV), the available energy and the type of installation (fixed or mobile).

Permanent magnet or electromagnet: what changes

Both technologies perform the same task: extracting ferromagnetic contaminants from the product. They differ in the way the magnetic field is created and in the constraints they impose on the installation.

Permanent magnet overband (OVAP)

  • Magnetic field generated by ferrite or neodymium permanent magnets, 24/7, with no variation and no power supply to the magnet (only the belt drive motor consumes power).
  • Integrated self-cleaning system: captured ferrous metals are discharged without human intervention.
  • Working height up to 400 mm (generally between 200 and 400 mm depending on the model and the product layer), conveyor speed from 0.5 to 3 m/s.
  • Cross-belt or in-line mounting (over the discharge point), virtually maintenance-free.
  • Fixed lines: aggregate quarries, mines, inert waste recycling, food processing, sawmills.

Electromagnetic overband (OV)

  • Magnetic field generated by an electrically powered electromagnet: greater separation power, for demanding installations.
  • Integrated conveyor belt that automatically discharges ferrous metals to a collection area, 24/7 operation.
  • Drive unit with 2-year warranty, through-shaft geared motor with anti-rotation device, double-drilled mounting lugs.
  • SRF sorting plants, mining and quarrying, cement plants, industrial waste and municipal solid waste recycling, wood and food processing.

Permanent magnet overband for mobile plant (OVAPEM)

On a mobile crusher or shredder (quarries, demolition sites, forestry operations), the OVAPEM applies the OVAP principle (permanent magnets, continuous discharge) in a robust, lightweight design adapted to the size of the machine.

Selection steps

  1. Check the conveyor width: it determines the compatible models.
  2. Check the supportable weight: the steel structure must bear the load of the separator, from 1.4 t for an OVAP up to 13 t for the largest OV.
  3. Assess the available energy: the OVAP operates autonomously with no power supply to the magnet; the OV requires a continuous electrical supply in return for more powerful separation.
  4. Distinguish between fixed and mobile installation: OVAP or OV on a fixed line, OVAPEM on mobile plant.
  5. Choose the mounting: in-line (over the discharge point) for flows with a strong material trajectory, cross-belt for standard conveyors.
  6. Set the working height: according to the power of the model and the thickness of the product layer.

Equipment mentioned in this guide

Sectors concerned: recycling, mining and quarrying, chemicals, plastics and wood, food processing. Further reading: overband magnet, which magnetic separator should you choose? and periodic inspection by magnetic audit.

Frequently asked questions

What is the difference between a permanent magnet overband and an electromagnetic overband?

The permanent magnet overband (OVAP) creates its magnetic field with ferrite or neodymium magnets, with no power supply to the magnet. The electromagnetic overband (OV) uses a continuously powered electromagnet, which delivers greater separation power.

At what height should an overband magnet be installed?

For a permanent magnet overband, the height generally ranges from 200 to 400 mm above the conveyor, depending on the power of the model and the thickness of the product layer.

Which overband magnet for a mobile crusher?

The OVAPEM, a permanent magnet overband for mobile plant, is designed to be installed on mobile crushers and shredders; it adapts to different machine sizes.

Need help choosing your overband magnet?

Tell us the width and speed of your conveyor, the material conveyed and the metals to be removed: our engineering department will recommend the right overband magnet. Request a quote