Cool running: the key to long magnet life lies in preventing overheating.
Paul Predagovic is the director of engineering and production at Winkle Industries, a producer of lifting magnets for 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 costly from a maintenance standpoint."
Alliance, Ohio-based Winkle Industries is a full-service manufacturer specializing in engineered components for industrial lifting and material handling equipment.
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.
Predagovic's most important words of advice for reducing maintenance costs? "Just cool it." He says heat is the number one factor in premature magnet failure.
Richard "Dick" Ptak, P.E., Winkle manager of magnetics engineering, frequently assists the Winkle sales team in educating customers on the proper use and care of their magnets. Their mission is to introduce operating and maintenance practices that will help ensure longer, better performance from lifting magnets.
KEEPING YOUR COOL. The first point of reference in identifying heat-related magnet problems is the magnet's duty cycle. "The length of time that the magnet is powered up during the lifting cycle is critical," Ptak says.
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 a magnet too early in the lift cycle, allowing it to get hot.
"A hot magnet, running around 270 degrees Fahrenheit, loses up to 25 percent of its lifting capacity," Ptak says. "Waiting two or three seconds to energize before the magnet reaches the material to be lifted will help to keep the heat down and actually increase the amount of material it picks up. If you set the magnet down on the material and let it crush out some of the air gaps before you actuate it, you can improve productivity," he suggests.
External sources of heat can also affect magnet performance. Little can be done to control these temperatures, Winkle admits, but it's for this reason that the company recommends purchasing magnets designed for hot surface work and proper duty cycles.
Over-powering the magnet is a common cause of excessive heat that can be prevented.
THE BUDDY SYSTEM, Paul Bean, Winkle regional sales manager, says magnet owners can introduce various practices to prevent magnet failures. "We have a number of clients who now operate their magnets on the 'buddy system'," Bean says. "Anytime a magnet gets too hot, 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 says proper inspection programs can reveal the breakdown of insulating materials in the coil that can result in hot spots and moisture or carbon traces in the coil that can cause excessive heating and electrical grounds to the magnet. Inspection programs can also identify mechanical problems that allow moisture to compromise the magnet. Routine system checks also aid in detecting malfunctions in the magnet controller, such as insufficient contractors, resistors and lead wire that undermine proper electrical flow.
Winkle President Joe Schatz says, "Heat and improper use will not only result in premature wear, it will also undercut the productivity of the material handling capacity for an extended period of time before the magnet finally fails. That means your crane is underperforming, and whatever it's feeding is under capacity as well."
Visit www.RecyclingToday.com for a checklist on operating a lifting magnet.
The author submitted this story on behalf of Winkle Industries of Alliance, Ohio.