Eriez global service director Richard Murray discusses best practice tips for maintaining suspended electromagnets.
In quarry operations, protecting downstream equipment from tramp metal is essential to maintaining productivity and avoiding costly interruptions. Suspended electromagnets play a critical role in this process, but like any equipment operating in harsh, high-throughput environments, their performance depends on consistent maintenance.
Routine inspection and preventive care can significantly reduce downtime, extend equipment life, and ensure reliable separation performance across crushing and conveying circuits. Suspended electromagnets (SE magnets), available in both self-cleaning and manual-clean designs, are built for long service life, often 20 years or more.
Achieving that lifespan depends on incorporating regular maintenance into standard plant operating procedures.
Manual-clean suspended electromagnets
Maintenance requirements for manual-clean units are relatively simple but still require consistency.
Operators should inspect the magnet at least once per shift, or daily, to monitor tramp iron accumulation. Cleaning frequency will vary depending on the volume of tramp metal, but excessive build-up should be avoided as it reduces magnetic effectiveness.
Eriez SE magnets include an expansion tank to protect against the ingress of contaminants into the coil area.
The expansion tank relief must be regularly inspected as an improperly functioning valve can cause damage to the system, which can lead to a leak forming and potential loss of oil.
Material build-up on top of the magnet should be regularly monitored and addressed. In quarry environments, fine dust such as limestone can settle on the magnet housing and act as an insulating layer preventing heat dissipation through the surface of the enclosure. This can lead to increased internal operating temperatures resulting in damage to the coil, reduced magnetic efficiency and diminished performance over time.
In quarry environments, fine dust such as limestone can settle on the magnet housing and act as an insulating layer. This can lead to increased operating temperatures and reduced magnetic efficiency over time.
Regular cleaning, at least monthly, helps maintain optimal operating conditions.
Self-cleaning suspended electromagnets
Self-cleaning systems introduce additional components, which require more detailed inspection and maintenance. Daily inspection of the rubber discharge belt is essential.
The belt plays a key role in removing tramp metal from the magnetic field, and any damage can quickly impact performance. Safety procedures must always be followed, and equipment should be isolated before inspection.
Belt life typically ranges from six to 12 months, although this can vary depending on the size and shape of tramp material. A single large piece of metal can cause significant damage. Even so, replacing a belt is far less costly than the potential damage to crushers, conveyors, or other downstream equipment that can result if tramp metal is not removed. The belt should remain running while the magnet is energised, as this helps dissipate heat and supports the magnet’s overall performance.
Given the variability in wear, it is advisable to keep a spare belt and repair kit on site.
Monthly checks of belt tension are also important. Excessive tension can lead to premature wear of belts, bearings, and shafts, while insufficient tension can cause sagging and interference with the conveyed material.
As a general guide, allow approximately 25-50mm of sag at the ends of the magnet, with up to 76mm at the centre if it does not interfere with material flow.
Bearing lubrication should follow a regular schedule aligned with other plant equipment. A lithium-based National Lubricating Grease Institute No. 2 grease is typically recommended.
In dusty environments, such as quarries and cement plants, proper lubrication is critical to preventing premature bearing failure and more extensive mechanical damage.
After around 250 hours of operation, pulley hub fasteners should be checked and tightened to the specified torque.
Annual inspection of transformer oil levels is also required. Oil should be topped up as needed, and any loss investigated to identify potential leaks.
For best performance, oil should be replaced every five years, with interim filtration to maintain dielectric strength. Maintaining oil quality supports consistent magnetic output and reliability. •
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