In aggregate-handling and quarry operations, protecting conveyor systems from tramp metal is essential. A stray bolt, excavator tooth fragment, or steel plate can cause expensive equipment damage, unplanned downtime, and contamination issues.
That protection starts with selecting the correct overband magnet for your conveyor system. However, not all overband magnets operate the same way.
Bunting supplies both electro overband magnets and permanent overband magnets for aggregate conveyors, quarry operations, recycling systems, and bulk material handling applications.
This guide explains the differences between electro and permanent overband magnets, compares performance characteristics, and helps aggregate operators determine which technology is best suited to their conveyor system.
Contents
Overband magnets are installed above conveyors to automatically remove tramp ferrous metal contamination from conveyed material.
Both electro and permanent overband magnets perform the same basic function, but they generate magnetic fields differently and are optimized for different operating conditions.
An oil cooled electro overband magnet installed in a gold mine in Finland
Electro overband magnets use an energized electromagnetic coil to generate a magnetic field capable of attracting and removing ferrous contamination from conveyed material.
Bunting’s electro range includes:
Electro overbands are particularly effective where:
Because the magnetic field is electrically generated, electro overbands can be switched on or off and optimized for specific operating conditions.
A permanent overband magnet installed inline to a conveyor
Permanent overband magnets use permanent magnetic blocks, typically ferrite or rare earth magnets, to generate a constant magnetic field without requiring electrical power.
Because there is no energized coil, permanent overband magnets:
Permanent overbands are commonly used where:
| Feature | Electro Overband | Permanent Overband |
| Power Requirement | Requires electrical power and cooling in some applications | No power required for magnetic field |
| Magnetic Field Adjustability | Magnetic field can be controlled or switched off | Magnetic field remains fixed |
| Deep Burden Performance | Excellent for deep burden and high suspension height | Performance decreases as burden depth increases |
| Maintenance | Requires maintenance of coils and cooling systems | Minimal maintenance requirements |
| Operating Costs | Higher operating cost due to power usage | Lower operating cost |
| Typical Applications | Primary crushers, high-duty quarry conveyors | Mobile plant, moderate-duty conveyors |
Choosing between electro and permanent overband magnets depends on several operational factors, including:
Each overband technology performs best under different operating conditions.
Permanent overband magnets are often the best solution when:
Common applications include:
Permanent overbands are valued for simplicity, low maintenance, and continuous operation.
Electro overband magnets are typically preferred when:
Electro overbands are commonly used on:
Where crusher damage risk is extremely high, electro overbands often provide the strongest protection.
As a general guideline:
Ultimately, the correct overband magnet depends on the operating conditions and risk profile of the conveyor system.
Electro overband magnets generate a magnetic field using an energized coil, while permanent overband magnets use permanent magnetic blocks that do not require electrical power.
Electro overband magnets are typically best for primary quarry conveyors with deep burden and high tramp metal risk, while permanent overbands are often suitable for smaller or moderate-duty conveyors.
No. Permanent overband magnets do not require electrical power to generate the magnetic field, although the self-cleaning belt may still require a motor.
Electro overbands generally provide deeper magnetic field penetration and are better suited for high suspension heights and deep burden applications.
Permanent overband magnets typically require less maintenance because they do not contain energized coils or cooling systems.
Overband magnets are widely used in aggregate processing, quarrying, mining, recycling, waste processing, and bulk material handling operations.
Selecting the correct overband magnet is an important decision for aggregate and quarry operations.
Permanent overband magnets provide simple, low-maintenance operation for moderate-duty applications, while electro overband magnets deliver the high-performance magnetic protection required for demanding conveyor systems.
Bunting’s engineering team can help evaluate your conveyor system, burden depth, suspension height, and tramp metal risk to recommend the most effective overband magnet solution.
If you need help selecting the correct electro or permanent overband magnet for your application, contact Bunting’s magnetic separation specialists.