Application Review – Small Tramp Ferrous from Recycled Gypsum

By Paul Fears | 23 November 2021

The extensive range of magnetic separators means that there are often several options for any one application.  However, the final selection is dependent on a number of variables including the available space, separation objective, and the critical nature of the separation.  This particular project required the improved separation of tramp iron from conveyed recycled gypsum.

Recycled Gypsum
Recycled Gypsum

Existing Magnetic Separation

The recycled gypsum processing line already had a Permanent Overband Magnet (model 14PCB9), which successfully removed larger tramp ferrous metal when suspended with a 350mm operating gap. However, additional removal of smaller ferrous metal would improve the product quality and protect processing plant.

Small tramp ferrous from recycled gypsum
Transport conveyor for the recycled gypsum

Tom Higginbottom, Bunting’s regional sales engineer, visited the plant to consider all options.  With restricted space, Tom quickly discounted the option of a high-intensity Drum Magnet option, prior to the screen.

Magnetic Separator Options

The site review identified three potential solutions:

Plate Magnet

A high-strength rare-earth Plate Magnet positioned either over the conveyor or under the trajectory of the recycled gypsum as it cascades off the end of the conveyor.  The suspended Plate Magnet would sit very close to the burden and attract ferrous contamination up onto the magnet face.  However, the Plate Magnet positioned under the trajectory of gypsum would enable a better separation.  Both options required manual cleaning, which was an issue due to restricted accessibility;

Rare Earth Pulley Magnet

A Rare Earth Pulley Magnet would replace the existing non-magnetic head pulley of the inclined conveyor.  The strong, high-intensity magnetic field attracts ferrous contamination down through the burden to the surface of the belt.  The movement of the belt then carries the captured ferrous metal out of the gypsum, depositing into a separate collection area.  This automatic cleaning option would enable the best level of separation;

ElectroMax Overband Magnet

An electromagnetic Overband Magnet produces a stronger field than a permanent design and, therefore, enhances the separation of tramp metal.  However, standard Electro Overband Magnets are significantly larger and heavier than permanent designs.  The ElectroMax Overband Magnet is a compact and lightweight version, often used in locations of restricted space.  At an operating gap of 350mm, the ElectroMax model EMAX140 produces 220% more magnetic separating power than the existing permanent model.  This enhanced magnetic force enables the separation of smaller tramp ferrous metal.  The ElectroMax is also self-cleaning, depositing separated tramp ferrous into a collection area away from the conveyed product.

Bunting Metal Separation Equipment
ElectroMax Overband Magnet

Final Solution

After careful consideration, the gypsum processor selected the ElectroMax Overband Magnet.  There were inherent difficulties in installing the Pulley Magnet, and necessity of regular manual cleaning ruled out the Plate Magnet.  The ElectroMax installation replaced the permanent model with only limited structural modifications.

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