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April 2007

Equipment Spotlight

Magnets

—View a list of manufacturers at the bottom of the page

­Magnetic separation may not be new to recycling, but the technology has recently hit heights that have transformed the business and dramatically escalated the value of recycled products, according Keith Rhodes president of the Michigan-based Magnetic Products, Inc. Today magnetic separation makes a compelling dollar argument for both steel and aluminum chip handling.

One major automotive customer of Rhodes used to pay hauling and dumping fees to get rid of rejected engine materials. Thanks to improved magnetic separation, the automotive maker now extracts “nearly pure aluminum that goes from the reject engine magnetic separation processing system directly to the aluminum kiln to be re-melted to produce new engines reducing their material costs,” Rhodes said. The steel chips, free of aluminum contamination, are sold to scrap processors, turning an expense into a profit.

Innovations are also seen in rubber tire recycling. Recycled tires used to be so low quality that shreds of steel belting wire would become embedded in rubber for playground surfaces. When children fell on, there was a risk of getting poked with the wire. Improved separators now pull those wire shards from the rubber, Rhodes said.

Credit the proliferation of permanent rare earth separators with these improvements. Rhodes believes rare earth separators have the greatest potential for tackling the tricky task of separating weakly magnetic and fine materials from non-ferrous materials in high volume processing.

Because the magnet equipment industry is unregulated, Rhodes advises consumers to have some knowledge of the vendor’s construction standards. “It critically important that the buyer understand the basics of how the magnetic separator is built,” he stated. Understanding the magnet’s basic construction, especially the magnet circuit, design and materials of equipment construction, and the magnet material grade equips buyers with the know-how to make a smart vendor selection, he added.

Magnetic Products’ Eddy Current system is offered with a standard, “soft-start,” digital PLC. Additionally, the Suspended Belt Magnets at MPI are offered in both 2-pole/1-face high magnetic gradient and 1-pole/1-face low magnetic gradient designs, Rhodes said. The gradient determines the speed that the metal is attracted to the magnet as it is extracted from the product being recycled. Rhodes noted that the Drum Separators and Magnet Head Pulleys at Magnetic Products, Inc are available in axial, radial or salient magnetic circuit designs. The magnetic circuit selected is key in determining the strength and pull of the magnetic separator and will vary depending on the application, he added.

Plastic recycling has also been making waves because of a rise in the price of crude oil and because Hurricane Katrina devastated many Gulf Coast plastics manufacturers, says Michael Wilks, marketing manager of the Kansas-based Bunting Magnetics Co. “It caused a shortage that encouraged plastic product manufacturers to both recycle their own waste and to purchase more recycled material from other sources,” he said.

Bunting Magnetics manufactures products to remove ferrous materials from plastic. Its FF Drawer Filter now uses a Rare Earth magnet 5 to 10 times more powerful than the ceramic magnet, Wilks added. The magnetic charge of the FF Drawer Filter can withstand the intense temperature at the throat of the machine — usually anywhere from 200 to 250 degrees Fahrenheit. While many standard Rare Earth magnets lose their magnetic pull at about 180 degrees, those used in this technology are good for 300 degrees, he said.

When recycling plastic with grinder and shredder feed conveyors, suspended magnets may not be enough. “When you recycle plastic you send it through a grinder or shredder and if there is metal left in it, it can damage the equipment,” Wilks said. The metal can plug the injection-molding machine, requiring the operator to shut down the equipment, wait several hours for it to cool, clean it and then reheat, losing a whole day. Metal in plastics can also damage extrusion machines by scaring the extruder screw, costing thousands of dollars for repair.

Wilks suggests Bunting’s Grinder/Shedder Feed Conveyor because it includes suspended magnets to extract ferrous metals, and an optional metal detector to locate brass, copper and non-ferrous metals.

There is a drawback. The magnet can remove the metal without damaging the plastic, but the metal detector will only sense the non-ferrous metal. This means the processor will have to put a reject mechanism in the conveyor to cause the metal to be removed and some good plastic will be lost with the rejected metal, Wilks explained.

He advised operators to use a magnet in front of the material so that it can extract the ferrous materials, causing fewer reject cycles by the metal detector and saving more of the good plastic.

Bunting Magnetics also created a custom-built magnetic drum with cooling fans inside. The drums’ interior magnets are designed to work in very high temperatures, but without the fans they could lose some of their charge, Wilks noted.

Wilks noted that ceramic magnets are still the most popular for recycling, and work best for large-plate magnets to pick up items like hammer heads or screws. But smaller metal fines or very large items require a Rare Earth Magnet, which gives a five-fold increase in power. He said consumers should expect to pay three to five times more for a Rare Earth magnet.

Hal Pfingsten, president of the Oregon-based Magnetic Specialties Inc., said that single-unit magnet plates are catching on because of their user-friendliness. His company’s product – called the Side-Tilt magnet – is a plate overhead magnet that hangs over a conveyor belt without a detached self-cleaning apparatus. The self-cleaning mechanism is built into the frame and the magnet can be tilted and lowered with a wench. Pfingsten emphasized the easiness of the Side-Tilt magnet, “It is one unit and can be installed over a conveyor as one unit.”

Other innovations are near or already here. Al Gedgaudas, product manager of recycling equipment at Pennsylvania-based Eriez Magnetics, said his company’s new Metal Sorter for non-ferrous metals is pushing the envelope. “It does not require air…but instead uses motorized fingers,” he said. “Sensors under the belt detect the metal and motorized paddles kick it out. It can also be set to remove stainless steel.” Gedgaudas said the product, with slated April introduction, is set to be priced lower than many others on the market.


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