Jonathan Schulberg from Eriez shares insights on why suspended electromagnets are a popular choice for protecting against tramp metal.
In quarrying, tramp metal such as steel fragments, bucket teeth, and fixings pose a constant, costly risk. They can stop crushers or screens, damage equipment, and cause maintenance issues.
Suspended electromagnets are one of the most widely used and effective solutions for tramp iron removal in conveyor systems. Installed above belt conveyors, these heavy‑duty magnets are designed to operate continuously, extracting ferrous contamination before it reaches crushers, mills and transfer points.
“Modern suspended electromagnets are built for harsh quarry environments. Their robust construction withstands vibration, abrasive dust, and temperature fluctuations during continuous operation. Designed for uptime, they suit modern aggregates plants where downtime is costly,” Eriez business development manager for heavy industry in the Asia Pacific region Jonathan Schulberg said.
“Design features such as oil expansion tanks help prevent condensation inside the magnet body and protect against thermal hot spots, extending coil life and overall reliability. “Force‑cooled designs and rectangular core configurations are used where belts are wider, burdens are deeper, or belt speeds are higher, conditions that are increasingly common as operations push for greater productivity.”
Suspended electromagnets are available in both manual‑clean and self‑clean configurations, with selection driven largely by contamination levels and site access.
Manual‑clean units are typically used where tramp iron is limited and predictable. These magnets are periodically de‑energised to release accumulated ferrous material once they are moved clear of the belt.
“The approach is simple and effective, with infrequent cleaning intervals and straightforward access,” Schulberg said.
Self‑clean magnets are designed for higher‑risk environments. Using an integrated belt system, they provide continuous, automatic removal of tramp metal without interrupting production.
“This makes them particularly suitable for primary crushers, high‑tonnage transfer points and installations where routine manual cleaning would be impractical,” Schulberg said.
Making the difference
Performance is heavily influenced by how and where a suspended electromagnet is installed. Two configurations dominate in quarrying applications: in‑line and cross‑belt.
In‑line installations position the magnet over the material trajectory as it discharges from the conveyor head pulley.
“This is generally regarded as the most efficient arrangement. As material leaves the belt, it spreads and slows, making ferrous contaminants easier to extract,” Schulberg said.
“Momentum carries iron toward the magnetic field, improving separation efficiency. Non‑magnetic head pulleys are essential in this configuration to prevent disruption of the magnetic field.”
Cross‑belt installations place the magnet at right angles above the moving bed of material. While effective, they typically require a stronger magnetic field and are less tolerant of high belt speeds or deep burdens, particularly where smaller ferrous pieces must be removed.
Schulberg said there are many factors to consider when purchasing a suspended electromagnet.
“Choosing the correct suspended electromagnet requires a detailed assessment of both material and conveyor characteristics. Lump size, bulk density, moisture content and tonnage all influence the strength of the magnetic field required,” Schulberg said.
“Conveyor parameters, including belt width, speed, inclination, idler configuration and head pulley diameter, are equally critical. As belt speeds increase or burdens deepen, a greater magnetic force is needed to pull ferrous material through the conveyed product.
“Ambient temperature, power availability, and the equipment being protected also factor into the final selection.”
Understanding performance
Not all tramp metal is equally easy to remove. Larger items, such as rail spikes or bucket teeth, are typically captured more easily than smaller fragments buried under heavy overburden. Flat or elongated steel pieces respond better to magnetic attraction than spherical or compact shapes, which present minimal surface area.
“Magnetic field strength is greatest at the centre of the magnet and decreases toward the edges, making alignment and suspension height critical. To maintain efficiency and prevent unwanted magnetic interaction, non‑magnetic idlers are recommended directly beneath the magnet installation,” Schulberg said.
While the primary role of suspended electromagnets is to protect plant, their impact goes beyond asset preservation. Removing sharp or heavy metal reduces the likelihood of belt damage, fires and secondary failures, improving overall site safety.
Optional features such as guarding, dust covers and monitoring devices further support safe, compliant operation, particularly in demanding environments.
“As quarrying operations continue to scale up, suspended electromagnets remain a practical and proven safeguard, quietly removing risk before it becomes downtime.
When correctly specified and installed, they deliver exactly what producers need, especially when it comes to uninterrupted production and peace of mind.” •
For more information, visit eriez.com
