In aggregate‑handling and quarry operations, protecting your conveyor systems from tramp metal isn’t optional. Every day a stray bolt, excavator tooth fragment or plate steel can cause unplanned downtime, equipment damage and product contamination. That protection begins with the right overband magnet installation. But not all overbands are the same. At Bunting we supply two distinct technologies: electro overband magnets (air‑ or oil‑cooled) and permanent overband magnets (no coil, no power). This article will compare the two technologies, outline where each is optimal, and guide you through the decision criteria to ensure you choose the correct solution for your aggregate conveyor.
Electro overband magnets utilise a coil through which current flows, generating a magnetic field that attracts ferrous materials from the conveyed load.
At Bunting, our electro range includes the ACW and ElectroMax (air‑cooled) and OCW (oil‑cooled) models. These systems give you controllable magnetism (you can shut off the current, adjust cooling, service coils) and are ideal where deep burden, high tramp‑metal risk or high belt widths exist.
Permanent overband magnets use solid magnetic blocks (ferrite or rare‑earth) that maintain a constant magnetic field without power.
At Bunting we offer a line of permanent overband magnets for applications where power supply is limited, maintenance is minimal and burden is moderate. Because there is no coil heating or oil/air‑cooling system, they are inherently simpler and low‑maintenance.
|
Feature |
Electro Overband |
Permanent Magnet Overband |
|
Power requirement |
Requires electrical power (coil current) + cooling in some cases |
No power needed for magnetic field (only belt/discharge motor) |
|
Magnetic field adjustability |
Field can be turned off or tuned (coil current) |
Field is fixed, cannot be easily adjusted post‑installation |
|
Deep burden / high suspension height |
Better suited for deep burden (thick material) or high suspension height (magnet further from belt) |
Performance falls off with increased suspension height or thick burden, requiring very large magnet blocks |
|
Maintenance / Service |
More service elements (coil, cooling, possible oil/air systems) |
Very low maintenance – basically just belt/discharge and mechanical components |
|
Weight / structure / retrofit |
Can be heavier (especially oil‑cooled) but design optimised for deep duty |
For heavy duty the block size can be large and heavy |
|
Cost (capital & lifecycle) |
Often higher initial cost + operating cost (power + maintenance) |
Lower operating cost (no magnetic power) but may have limit in heavy duty applications |
|
Applications |
High risk tramp metal, crushers feed, wide belts, high burden depth |
Lower capacity conveyors, mobile screens, where minimal maintenance preferred |
When selecting between electro and permanent overbands for your aggregate conveyor consider these scenarios:
If multiple checklist items exceed moderate thresholds (wide belt, deep burden, high risk tramp metal), then lean to electro overband. If conditions are more moderate and maintenance/power are constraints, then permanent overband is likely best.
In the aggregate equipment world, selecting the right overband magnet is a strategic decision. At Bunting we recommend evaluating your specific site conditions and throughput demands rather than defaulting to one technology. Permanent overband magnets excel where simplicity and low maintenance are the priority. Electro overband magnets deliver the deep, reliable protection necessary for high duty, primary conveyors where the cost of downtime is very high.
If you’d like assistance in matching your conveyor to the correct Bunting model (either electro or permanent overband), our application engineering team is ready to help with model selection, load simulation and layout guidance.