ALLIANCE, OH – Lifting magnets are important revenue generators in most scrap metal yards. Suspended from the business end of primary material handlers, the magnets are a critical link in the productivity of processing and shipping operations. But, according to one industry expert, few recyclers are actually getting their money’s worth from their magnet investment!
Paul Predagovic is the Director of Engineering and Production at Winkle Industries, a leading producer of lifting magnets for both recycling and steel mill applications. “Magnets are one of the most poorly understood pieces of material handling equipment,” he claims. “They can be incredibly reliable and potentially last for many, many years of service. Instead, we find that working magnets chronically underperform and are often a costly maintenance item in the yard.
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Remanufacturing and recertifying magnets is a major line of business at Winkle, based in Alliance, Ohio. The Winkle plant would see less rebuild work, Predagovic says, if yard owners and machine operators had a better understanding of how to care for their magnets.
His most important words of advice for reducing maintenance costs?
“Just cool it!” Predagovic explains that heat is the number one factor in premature magnet failure. “Heat, moisture, electrical system faults and simple abuse can all compromise magnet performance. But heat is by far the most important.”
Richard “Dick” Ptak, P.E., Manager of Magnetics Engineering, frequently goes on the road with the Winkle sales team to help educate customers on their magnets. Their mission is to introduce operating and maintenance practices that will help them get longer, better performance from lifting magnets.
The first place that they look for heat-related magnet problems is in the magnet’s duty cycle. “The length of time that the magnet is powered up during the lifting cycle is critical. Think of it this way: an average toaster produces 800 watts of heat during its work cycle. A typical 66″ to 68″ magnet produces nearly 20,000 watts! That’s a lot of heat and, unlike the toaster, magnet casings aren’t vented.”
Winkle recommends that operators stay well within the manufacturer’s recommended duty cycle rating, which should be identified on the magnet’s nameplate data tag. Operators often power up the magnet too early in the lift cycle, allowing too much time for it to get hot.
“A hot magnet, running around 270o F, loses up to 25% of its lifting capacity. Waiting till 2 or 3 seconds before the magnet reaches the pile will help to keep the heat down and actually increase the amount of material it picks up,” Ptak suggests. “If you set the magnet right down on the pile and let it crush out some of the air gaps in the pile before you actuate it, you can improve the lift per cycle even more.”
External sources of heat can be another factor in magnet performance, including the temperature of ambient air and of the material being lifted. There is little you can do to control these temperatures, Winkle admits, but it’s for this reason that the company recommends purchasing magnets designed for hot surface work.
Over-powering the magnet is one common cause of excessive magnet heat that can be prevented. “Magnets are supposed to run at 230 volts DC,” says Ptak. “Exceeding the voltage even a bit makes a big difference to the amperage running through the coils and the amount heat it generates. Just 20 volts over can produce thousands of watts of damaging heat.”
“Buddy Up” for performance
Paul Bean, Regional Sales Manager at Winkle Industries, says that magnet owners can introduce various practices to prevent magnet failures. Simply training operators to be more aware of the magnet’s duty cycles can be a big step. “We have a number of clients who now operate their magnets on the ‘buddy system” he claims. “Anytime a magnet gets too hot to touch, it comes out of service and a “buddy” magnet replaces it. Within 48 hours, the hot magnet has cooled down and it becomes the new ‘buddy’ – that way, neither magnet is ever overstressed.”
Bean advocates a consistent inspection schedule to take the heat off magnet integrity in several ways. Inspections can reveal insulation shorts in the coil that result in hot spots, along with moisture or carbon traces in the coil that can ground the magnet and cause premature heating. Inspecting for these faults can also identify problems that allow moisture to compromise the magnet through cracks in the case, welds or bottom plate, through damaged leads or terminal boxes or through sheared-off center-pole bolts. Routine system checks look for malfunctions in the magnet controller, such as bad leads or worn contacts, that undermine the proper flow of electrical power.
“To outsiders, a lifting magnet just looks like a big slab of iron on a chain,” he admits. “It’s hard to see the sophisticated physics going on inside it. But to get your value out of a magnet, you have to recognize it a valuable piece of equipment and treat it with that kind of respect.”
The President of Winkle Industries, Joe Schatz, sees growing interest from customers in magnet maintenance and inspection programs offered by the company. “Improper magnet use leaves a lot of money on the table for recyclers. Abuse and heat not only wear out the magnet faster, they can undercut your entire material handling capacity for a long time before the magnet finally fails. That means your crane is underperforming, and whatever it’s feeding is under capacity, too. Better magnet habits can really pay off!”
Check list for magnet performance
About Winkle Industries Winkle Industries is a worldwide leader in engineered solutions for users of mill-duty material handling equipment. Winkle’s ISO 9001:2008 facilities provide end-to-end design, manufacture and support for above-the-hook and below-the-hook lifting devices, electrical and mechanical crane products, on-the-ground material handling equipment, engineering services, aftermarket services, machining and fabrication. Winkle’s experience and resources are “raising customer expectations” on a wide range of needs, from innovative product design to customer process improvement. For information, contact Mark Volansky, Director of Sales |
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