The largest electro overband magnet ever built at the Bunting manufacturing plant in Redditch, UK is destined for installation in a gold mine in Northern Finland.
Over a 12-month operating period, the overband magnet will lift and separate damaging tramp metal from approximately 2.7 Mt of conveyed ore, protecting crushers, screens and other up-stream process plant.
The electro overband magnet uses high-strength magnetic forces to lift and then automatically discard tramp ferrous metal present in conveyed ore.
In operation, the large electro overband magnet is suspended in a crossbelt orientation across the non-magnetic head pulley of a conveyor transporting mined ore.
Any tramp ferrous metal entering the deep and strong magnetic field is attracted to the face of the electro magnet and lifted up and onto the surface of a continuously-moving self-cleaning rubber belt.
Reinforced and heavy-duty rubber wipers on the belt catch the captured metal, transferring it to the side and away from the conveyed ore. As the wipers move the ferrous metal out of the overband magnet’s magnetic field, it drops under gravity into a collection area.
This latest electro overband magnet is part of a major plant expansion and upgrade at the Kittila Gold Mine in Northern Finland.
Bunting engineers worked closely with the mine operator to design a bespoke system for the difficult application. Design considerations included the width of the conveyor, the volume of conveyed ore, and the size and shape of the tramp ferrous metal.
The Bunting design team calculated the minimum magnetic field and force density for optimum separation using an in-house developed Electro Overband Magnet Selection Programme. These criteria provided the basis for the design of the electromagnetic coil by the Bunting-Redditch engineering team.
The final design is a model 205 OCW50 Crossbelt Electro Overband Magnet. The 17 kW electromagnetic coil, generating the strong magnetic field, is cooled using recirculated oil. Efficient cooling of the electromagnet is critical as the magnetic force decreases proportionally to the rising temperature of the coil.
The Overband Magnet is 4.2m long, 3m wide and 2.2m high, weighing just over 13t.
“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.”