Bunting built a 13-ton OCW50 Electro Overband Magnet to protect a gold mine in northern Finland. Suspended above the ore conveyor, it removes damaging tramp metal from up to 2.7 million metric tons of ore per year, helping protect crushers, screens, and other processing equipment.
Electro Overband Magnet
The Electro Overband Magnet uses a high-strength magnetic field to lift and automatically discharge tramp ferrous metal from conveyed ore. In operation, the magnet is suspended in a crossbelt orientation above the conveyor’s nonmagnetic head pulley. Tramp metal is attracted to the electromagnet and lifted onto a continuously moving, self-cleaning rubber belt. Reinforced rubber wipers carry the metal out of the magnetic field, allowing it to drop into a collection area.
- Technical product information: Electro Overband Magnets
This Electro Overband Magnet is part of a major expansion and upgrade at the Kittila Gold Mine in northern Finland. Bunting engineers worked with the mine operator to design a custom magnet for the application. Key design factors included conveyor width, ore volume, and the size and shape of the tramp metal. Using these inputs, the design team calculated the minimum magnetic field and force density required for optimal separation with its in-house Electro Overband Magnet Selection Program. The results defined the electromagnetic coil design.
The final design is a model 205 OCW50 Crossbelt Electro Overband Magnet. Its 17 kW electromagnetic coil is cooled with recirculated oil because magnetic force decreases as coil temperature rises. The magnet measures 4.2 m long by 3 m wide by 2.2 m high, weighs just over 13 metric tons, and was built at Bunting’s magnetic separator manufacturing facility in Redditch, UK.
The magnet is positioned in a crossbelt orientation over the nonmagnetic head pulley of a 1,600 mm-wide conveyor inclined at 12° and traveling at 0.75 m/s. Ore particles range from 70 to 400 mm, and the conveyor handles 450 to 765 metric tons per hour, or approximately 2.7 million metric tons per year.
The tramp iron includes steel rebar measuring 2,400 x 20 mm in diameter, cable bolts measuring 600 x 15 mm in diameter, steel mesh, and broken drill bits. With a maximum working gap of 600 mm, the magnet can lift and separate tramp metal through an ore burden up to 500 mm deep. This requires a deep, strong magnetic field and sufficient force density.
“Large mining projects, such as this, often require bespoke solutions,”
explained Adrian Coleman, the General Manager of Bunting’s Redditch
facility. “Over 40 years we have gained
considerable experience in designing and building large Electro Overband
Magnets. However, this was the largest
we have ever manufactured at Redditch, presenting many challenges, which were
overcome. And the design and
manufacturing process all took place during the COVID-19 crisis.”
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Bunting-Redditch has decades of experience designing and building large Electro Overband Magnets for mining applications. This project combined the engineering and production teams’ expertise to manufacture the largest unit built at the Redditch facility.
For additional information about Electro Overband Magnets and custom designs, contact Bunting:
Email Gordon on: GKerr@BuntingMagnetics.com
Telephone: +44 (0) 1527 65858
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