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Magnetic Separators for Construction & Demolition Recycling

The EPA estimates that 600 million tons of Construction and demolition waste were generated in the United States in 2018, which is more than twice the amount of generated municipal solid waste. Of this 600 million tons, much of it, including concrete, metals, and wood, can be reclaimed, processed and resold. This not only generates income for the recycler but lessens the environmental impact of disposal in landfills and the extracting of new materials. The recycled material is also more cost effective for use in new construction projects. This circular economy can benefit all participants, but only if processed and separated correctly and efficiently. Dings magnetic separation equipment helps accomplish this process.

Magnetic Separation for Construction & Demolition Recycling Facilities.

Overhead Self-Cleaning Electromagnets

Overhead self-cleaning electromagnetic separators are often used in construction & demolition recycling facilities with higher throughputs. The deep toroidal shape of the magnetic field produced by an electromagnet make it the separator of choice for pulling ferrous metal and stainless steel out of applications with heavier burden depths. This ensures that ferrous metals that may have been missed by permanent magnetic separators with shallower field depths are caught and removed for collection.

Dings electromagnets use our unique coil design of wound anodized aluminum strap where the anodized layer serves as the coil’s insulation. The anodized layer isn’t as susceptible to burning when not completely submerged in cooling oil as copper wire insulated with polymer or bare aluminum with Nomex® paper insulation that’s often used by others. This means the oil can be kept at a lower level, capable of being contained within the magnet itself. Our design eliminates the need for external oil expansion pipes or tanks that require maintenance. Dings stands behind our electromagnets with an industry best 20-year warranty on coil burnout. Up to four times longer than the others.

The self-cleaning electromagnet comes equipped with a multi-ply rubber belt with standard 1-inch vulcanized rubber cleats but is also available in a 3-inch cleated version for larger material. This belt travels across the face of the magnetic separator automatically discharging the ferrous metal it pulls from the recycling stream so it can be easily collected.  

Overhead self-cleaning electromagnets shown with standard and 3-inch cleat belts.

Magnetic Deep Draw Drum Separators

Heavy-duty magnetic drum separators, such as Dings Deep Draw Drums, are another popular option for the removal and collection of ferrous materials from construction & demolition recycling streams. The raw material is discharged from the conveyor onto a rotating stainless-steel drum with a fixed permanent magnet inside of it. The non-magnetic material follows a normal trajectory off the rotating drum while the internal magnet holds any ferrous material to the shell until it rotates past the magnetic area discharging it for collection. Much like overhead magnetic separators, Deep Draw Drums also allow for a heavy throughput.

Deep Draw Drum Magnetic Separators shown with and without frame and drive motor

The Dings Deep Draw Drum, using permanent magnets, is designed to operate at top efficiency at all times while maintaining a constant magnetic strength throughout the day. Deep draw drums are engineered with Dings’ unique DFC (Dings Flux Control) magnetic circuit that eliminates internal flux leakage between magnetic poles and improves the magnet’s performance by harnessing magnetic strength lost in other designs. This is accomplished by strategically placing blocking magnets between the poles of the magnetic structure where other designs have filler or empty space.

Magnetic drum feed arrangements
Magnetic drum feed arrangements

Magnetic Separation for Construction & Demolition Recycling Portable Plants.

Portable concrete recycling plant with Self-cleaning permanent magnetic separator
Portable concrete recycling plant with Self-cleaning permanent magnetic separator

Overhead Self-Cleaning Permanent Magnets

Overhead permanent magnetic separators always have a magnetic field operating at peak efficiency and don’t require an outside energy source to produce it. Permanent magnets are less expensive than their electromagnet counterparts and are more space efficient. Their smaller size makes them ideal for use in tight spaces. However, they have a shallower magnetic field than electromagnets which means they are at their best when used in applications with lighter burden depths and smaller belt widths. Dings Overhead Permanent Magnetic Separators also feature Dings DFC Circuit design for improved performance over other permanent magnets.

Self-cleaning permanent magnetic separator

Magnetic Head Pulleys

Magnetic pulleys are non-electric, self-cleaning magnetic separators that operate as head pulleys on conveyors to separate and collect ferrous and stainless steel from conveyed material. As the product is discharged from the conveyor, non-magnetic material follows its normal trajectory off the belt while ferrous clings to the magnetic head pulley until it is released under the conveyor as the ferrous metal leaves the pulley’s magnetic field.

Three Different Magnetic Head Pulleys
Three Different Magnetic Head Pulleys

Under certain situations, using a magnetic head pulley for your application can have advantages when compared to an overhead magnetic separator. An overhead magnetic separator has to pull ferrous material out of a burden through the air up to the suspended magnet. The suspension height puts a greater distance between the magnet’s face and the material to be separated necessitating the use of a larger magnet. A magnetic head pulley however, has the mechanical advantage of pulling ferrous material down to the belt at the magnet’s surface where its field strength is greatest. This may allow for higher belt speeds, resulting in increased production and productivity.

Diagram of Magnetic Pulley Field Depths
Diagram of Magnetic Pulley Field Depths

Magnetic head pulleys are best used in applications where the burden depth is shallow or in deeper depths when used in conjunction with an upstream crossbelt overhead magnet. This arrangement ensures that if a heavy burden depth causes ferrous metal to be missed by one magnet, it will be caught by the other. One magnetic separator working on the bottom of the load and the other at the top. Dings manufactures three different strength series to accommodate varying burden depths and throughput volumes, Dings standard, heavy-duty and DFC Ultra.

Separating Non-Ferrous from Construction & Demolition Waste.

The key component of the eddy current separator is the magnetic rotor, which has a series of permanent rare earth magnets mounted on a support plate attached to a shaft. The magnetic rotor is surrounded by a wear shell which supports the conveyor belt. This allows the rotor to spin independently and at a much higher speed than the wear shell and belt around it.

Dings 9500 model Eddy current separator

When a piece of non-ferrous metal (such as aluminum) passes over the separator, the magnets inside the rotor rotate past the aluminum at high speed. This forms eddy currents in the aluminum which, in turn, creates a magnetic field around the piece of aluminum. The polarity of that magnetic field is the same as the rotating magnet, causing the aluminum to be repelled away from the magnet. This repulsion makes the trajectory of the aluminum greater than that of the nonmetallic material, allowing the two material streams to be separated. An optional splitter is often used at this point to ensure that the that the two material streams are properly separated

Severe Duty Self-Cleaning Electromagnets for Concrete Recycling

Portable concrete recycling plant with Severe Duty Self-cleaning magnetic separator
Portable concrete recycling plant with Severe Duty Self-cleaning magnetic separator

Dings Severe Duty Electromagnets are specifically designed to withstand the harshest environments and toughest applications. The Severe Duty Model comes equipped with a Dings ‘Durabelt’ of stainless-steel pads and cleats. The Durabelt Prevents the underlying rubber belt from being pierced by sharp ferrous metal, such as rebar. Also included are a heavy-duty drive assembly, lagging on the drive pulley and reinforced suspension/mounting hardware. As with all Dings electromagnets, the severe duty model features our unique coil design and an industry leading 20-year warranty on coil burnout.

Severe Duty Self-Cleaning Electromagnetic Separator

Dings Company Magnetic Group Helps You Find the Right Magnetic Separation Solution for Your C&D Recycling Application

Dings Company Magnetic Group engineering and sales staff work together from our Milwaukee, WI factory to provide outstanding customer service from experts in magnetic separation. We listen to our customers to gain an understanding of their needs and apply our experience in their trade to provide magnetic separation equipment that is sized and positioned for the best possible performance in their specific application. Contact Us at or call us at (414)672-7830 for help finding the right magnetic separation solution for your recycling application.