Suspended belt magnets are large permanent or electro-magnetic separators that typically hang above belt conveyors or vibrating pan feeders in either an in-line or crossbelt position to recover ferrous metals from the material burden as it passes under the magnet. They are used in many industries to remove tramp iron or large pieces of ferrous metal from the material burden, protecting crushers and other processing equipment from damage. For the recycling industry, their task is to reclaim large amounts of ferrous material to be sold as a commodity.

Typical applications in recycling include removing sheet ferrous from automobile shredder fluff; ferrous cans from commingled household recyclables and municipal solid waste (MSW) at material recovery facilities (MRFs); iron from foundry sand; metals from construction and demolition (C&D) debris; and ferrous metals from boiler bottom ash.

Suspended box magnets for recycling are self-cleaning units consisting of the box magnet, a frame, pulleys, a motor drive, and a belt with cleats around the magnet to discharge the recovered ferrous material – hence the term "belt magnet." As the ferrous metal is attracted to the magnet, the cleats on the magnet’s belt move the iron out of the magnetic field where it is discharged (often over a splitter or divider) into chutes, roll-off bins, or take-away belt conveyors. Most belt magnets have a hemispherical shaped magnetic field, stronger in the center and weaker at the edges, which is ideal for trough belt conveyors and aids in discharging the collected ferrous material.

The box of the magnet can either have a permanent or electromagnetic element inside. Permanent magnets are built in various sizes good for suspension heights or magnet gaps of 4 inches to 14 inches, while electros are built in various sizes good for magnet gaps of 4 inches all the way up to 30 inches. Electromagnets are often preferred since they typically provide more magnet per dollar, especially at magnet gaps of more than 8 inches. The electros can also be turned off when the plant is not running or to free ferrous material if a jam occurs, making them safer in these situations.

Belt magnets provide a reasonably clean ferrous sort since they attract the steel or steel tin through gravity, allowing paper, trash or non-magnetics to fall free in the process. Magnetic pulleys, by comparison, will discharge any trash caught between the ferrous material and the pulley magnet.

The maintenance item on belt magnets is the belt and self-cleaning system. Can lids; sharp ferrous metal; large, heavy pieces; and long angle, pipe or bars can cut, abrade, puncture, or rip the magnet’s self-cleaning belt. But measures can be taken to prolong the belt service life. Thicker belts (but not too thick or they can overload the bearings), urethane belts or urethane centerlane belts, and armor clad belts (belts with stainless steel slats and cleats bolted to the belt face) can help lengthen service life.

Since the iron gathers around the core area when it gets to the belt, only the center one-third to one-half of the belt needs to be protected. If wires and can lids are commonly processed, it may be a good idea to use molded or vulcanized rubber rather than stainless steel cleats, so that wire and lids are less likely to catch under the slats or cleats.

Also, having more belt cleats (i.e., cleats on 18-inch centers) reduces belt wear. Having fewer belt cleats (i.e., cleats on 36-inch centers) provide a cleaner ferrous sort, since the ferrous material tumbles in the magnetic field, allowing some trash to fall out before the cleat pushes the steel into the discharge zone.

Many recycling applications use picking belts operating at 40 to 60 feet per minute (FPM). In these applications, it is useful to have a cross-belt magnet installed between the belt conveyor idlers discharging ferrous material perpendicular to the conveyor belt travel. If the magnet is located over the discharge area, or "in-line", and the conveyor speed is less than 300 FPM, a non-magnetic (typically stainless steel) head pulley must be used because a steel pulley will be magnetized, lowering ferrous recovery.

In general, magnetic steel components such as chutes, framing, idlers, and pulleys should not be used within two to three feet of the magnet’s face and 1/2 to 1 foot of the magnet sides and top. Instead, non-magnetic manganese or stainless steel can be used in these areas.

Some belt magnets use multiple magnets inside the self-cleaning belt. The additional magnets clean the ferrous material by agitating or flipping it and shaking out trash. The additional magnets can also be designed to extend the ferrous discharge point, conveying ferrous material beyond adjacent equipment.

When magnets are mentioned in the context of scrap recycling, the first image that usually comes to mind is a large lifting magnet attached to a crane, moving heavy piles of ferrous scrap. Over the years, lifting magnets have matured from heavy cast, copper wound units to lightweight, aluminum cast and fabricated units to meet the criteria of handling specific types of scrap.

The lifting magnet must be married to the cranes on which they are mounted and with the payloads they can carry. They all should be, and in most cases are, ruggedly built to withstand the physical abuse that is a normal part of their operation.

Particular attention should be paid to magnet external design, such as its case, bottom plate, lugs, chain sling and outlet box with appropriate lead wires and connectors. A typical cross-section is noted in Figure 1.

Internally, consideration should be given to the coil construction, the insulation used and the type of potting compound used to lock the coil in position. The coils of these magnets are normally wound for a 75 percent duty cycle, which means the unit will be on for three minutes out of four.

At the start of an operational day, a lifting magnet will provide the maximum lift, but after six to eight hours of operation, it will lift less. The reason is that as the coil heats, the resistance increases, providing less current and thereby reducing the magnet’s effectiveness. The magnet designer must take this into consideration, to minimize the drop.

Controllers for these magnets must be capable of handling the counter EMF voltage developed when switching to the D.C. side of the power source without damaging the coils, so select these carefully. Power take-off generators are now hydraulically driven, providing a compatible package for the hydraulically operated cranes.

Lifting magnets are electric tools that, like other tools, require periodic maintenance to keep them in first class operating condition and to minimize costly repairs. Unfortunately, magnets are often looked upon as massive, indestructible objects and only receive attention when a problem occurs. Magnet operational problems are generally expensive, both in direct repair costs and in downtime. A regular planned maintenance program can keep problems, and their costs, to a minimum.

A regular inspection program will identify small problems and allow them to be corrected before they become big problems, allow you to plan major repair work so that it fits into your production schedule, and let you know which of your operating personnel may require additional training.

A planned maintenance program is not expensive. Regular inspections take only a short time. The program will pay for itself the first time a minor problem is detected and corrected before a major repair becomes necessary.

Once you have committed to begin a maintenance program, some preliminary steps should be taken. Make one person responsible for managing the program. Your maintenance supervisor, yard foreman or other qualified individual should be assigned the task of overseeing the program, making sure that inspections are done properly and regularly and that necessary corrective actions are taken.

Do an inventory of your lifting magnets. Identify each by size, manufacturer, model number, serial number and date purchased. Assign your own number to your magnets. This will make future identification easier. A good way to do this is to weld the assigned number on the top of the magnet case. Gather product and maintenance information for each of your magnets. Keep the collected information in a file that is easily accessed.

Order at least a minimal quantity of parts for routine repairs. These parts should include lead sets, connectors, terminal box parts, chain pins and center pole bolts. If you have a number of identical magnets, you may wish to stock items such as center pole shoes, chains and other major items. Having these parts on hand will allow your personnel to make minor repairs quickly, saving you downtime.

Be sure that your maintenance personnel have the necessary tools to inspect your magnets and perform minor repairs. These tools should include ordinarily available hand tools like wrenches, sockets and screwdrivers. Also necessary to a maintenance program are a good quality volt-ohm meter for measuring could resistance and an insulation tester (megger) for testing coil insulation.

Organize a formal training session. Maintenance personnel, magnet operators and appropriate supervisory personnel should be included in the session. The agenda should include the "whys" and "hows" of your proper magnetic maintenance and operation.

Prepare a magnet maintenance log sheet for each of your magnets. Have your inspector perform a thorough initial inspection following the procedures below. Make necessary repairs immediately.

Remember: do not perform electrical tests on an energized magnet. To avoid accidentally energizing the magnet during the testing procedure, the magnet loads should be disconnected from the power cables prior to testing. Personnel should never stand or move under a lifting magnet for any reason or extend any portion of their bodies under a suspended or partially lifted magnet. To perform an inspection, the magnet should be placed on solid supports. Turn magnets upside down or tilt away from the inspector and solidly support to inspect the lower portions of the magnet.

The mood was upbeat at the Nonferrous Committee meeting during the annual spring convention of the Bureau of International Recycling, Brussels, held in Istanbul, Turkey, May 26 through 28. Reporting on markets in Asia and the Pacific Rim, John Crabb of Simsmetal Ltd., North Sydney, Australia, said that in the world of nonferrous metals trading, the last year was the very eventful.

"Despite some dramatic price fluctuations on terminal markets, we have seen growth in physical demand for many of the base metals driven by continued strong economic growth in the United States, along with China and other major Asian economies," said Crabb.

On the copper side, the long-awaited increase in supply has yet to materialize and the relatively strong world consumption, led by the U.S., has easily absorbed all available material, he said. But despite good demand, the threat of increased copper production continued to overhang some markets.

"Asian demand for copper scrap has been, and continues to be, strong," said Crabb. "Demand from China has been consistent this year and pricing has generally been competitive. Similarly, there have also been good demand and prices for brass grades in this country. But there is weaker import demand for higher grades of copper and brass in Japan and Korea due to currency realignments."

Aluminum prices have risen recently, even as LME stocks have increased, and demand appears to have improved as U.S. economy continues to prosper. Alcan estimates that worldwide demand for aluminum grew at a 10 percent annual rate in the first quarter of the year.

"Demand for aluminum has been and continues to be strong throughout the Asia Pacific region," said Crabb. "Demand for extrusion scrap into South China has been decreasing as the supply of competitive Russian ingot is now readily available in large quantities. Secondary smelter capacity is being increased in South China, Malaysia and Thailand."

There is substantial economic activity in India, according to Ashwini Singhal of Singhal Commodities, Bombay, India, as a number of economic reforms have been implemented, including removal of restrictions on overseas investments and the rationalizing of import duties. There are also more privately-owned ventures than there were in the past.

Copper in India is experiencing a huge demand/supply gap, said Singhal. But significant new capacity is being added, so by 2005 the situation will likely reverse and there will be more exports of copper from India as opposed to imports. There will also be more zinc production. Currently, the country is producing surplus aluminum.

On the downside, says Singhal, although industry leaders in India are fully aware that recycling scrap metal is economically advisable, the country is experiencing some problems due to Basel Convention restrictions.

The Middle East nonferrous market is also benefiting from the generally healthy world economic picture, according to Salam Sharif of Sharif Metals Ltd., Sharjah, United Arab Emirates. Gulf countries and Egypt are making rapid strides towards development, he said. A construction boom is boosting these economies and is supporting the metals market.

"The prospects for 1997 appear relatively positive for the nonferrous metals market," said Sharif. "The metals should be well positioned to benefit from a combination of higher economic-led demand growth, and a renewed surge of investment funds entering the sector."

In the U.S., the nickel/stainless steel scrap market reflects a very healthy stainless steel production level, according to Barry Hunter, senior vice president of Keywell L.L.C., Baltimore. Total U.S. production of stainless grades in 1996, including 400 series, was approximately 2.1 million tons, he said. These figures are expected to increase between 3.5 percent and 6 percent in 1997.

"How much scrap is there to assist that production level?’ asked Hunter. "Using a conservative yearly export figure of 250,000 tons, I calculate a total of approximately 800,000 tons of processed austenitic scrap potentially available to U.S. producers. We are unlikely to go beyond that unless the U.S. scrap price is competitive to imported scrap."

There could be potential late this year for a market correction in the form of destocking, and profits are poor, he said.

If the status quo remains, according to Hunter, there could be an inventory build up of finished product, which would tend to increase discounts and profitability and would eventually reduce production. "However, should European and Asian economies improve, I feel potential consumption in the states could support a 6 percent increase in production, thereby maintaining high scrap utilization, and hopefully decent business," he said.

REPORT FORECASTS PLASTICS GROWTH

Business Communications Co. Inc., Norwalk, Conn., has published RP-216R, Plastics Recycling, a report that forecasts an average annual growth rate (AAGR) of 13.9 percent for the United States plastics recycling market.

The BCC data show that the biggest application for flexible packaging is in bags and liners made of polyolefin. The flexible recycling market will grow from a 1995 market of 175 million pounds to 470 million pounds in 2000, reaching an AAGR of 21.8 percent.

BCC notes that the foam packaging – mainly polystyrene – recycling market is projected to grow from 65 million pounds in 1995 to 275 million pounds by 2000, achieving a 33.4 percent AAGR.

Recycling of high density polyethylene (HDPE) and polyethylene terephthalate (PET) containers, with the most volume, will likely reach 2,194 million pounds in 2000, an AAGR of 11.2 percent.

FIRE DETROYS CANADIAN CAR PARTS RECYCLER

A major fire at a plastic car parts recycling plant in Hamilton, Ontario, on the evening of July 10, destroyed Plastimet Inc. No one was injured, and the cause of the fire is unknown. The company recycled polyvinyl chloride and polyurethane. Plastimet had moved into the 83,000-square-foot building just last fall, and was actively working to correct various fire code violations.

Plastimet’s owner, David Lieberman, says he intends to rebuild the facility as soon as possible, and has already begun searching for a new location.

MERGERS TAKE HOLD FOR PAPER COMPANIES

Faced with an overcapacity of finished product and difficult pricing over the past several quarters, a number of large and mid-sized paper companies have been involved in acquisitions. Following on the heels of the Abitibi-Price/Stone-Consolidated acquisition earlier this year creating the largest newsprint producer in the world, Fort Howard and James River announced plans to combine their paper operations, predominantly tissue making capabilities. The new company will be called Fort James. The transaction is valued at around $3.4 billion.

Smaller operations have followed this move. Rock-Tenn, having recently completed the acquisition of Waldorf Corp., recently announced plans to merge with Rite Paper, a manufacturer of laminated recycled paperboard products used mostly by the furniture industry. Also, Greif Bros. has recent;y announced plans to acquire Independent Container, Louisville, Ky., a corrugated container company. The company has plants in Louisville, Ferdinanc, Ind., and Erlanger, Ky.

CITY CARTON PURCHASES DURBIN PAPER STOCK

City Carton Company, Inc., Iowa City, Iowa, has purchased the operations and assets of Waste Management Inc.’s, Midwest Division of Durbin Paper Stock, Rock Island, Ill.

City Carton is a full service recycling company that has served the Quad Cities area since 1967. It provides collection, processing and marketing services for all grades of paper stock and select grades of plastics, glass and metal to commercial, industrial and municipal customers in Iowa, Illinois and the Midwest.

City Carton owns and operates six processing plants, along with a fiber fuel division, a document destruction company and a refuse and recycling equipment company.

SCRAP TIRE FACILITY RECEIVES PERMIT

The California Integrated Waste Management Board, Sacramento, has approved a major scrap tire facility permit for a site in northern Merced County.

The company receiving the permit, Golden By-Products Inc., plans to process nearly 4 million scrap tires annually by its fifth year of operation. The permit currently allows the owners of the five-acre site near Ballico to store up to 85,000 scrap tires and process them into fuel for several energy-producing facilities in the San Joaquin Valley.

Upon arrival at the facility, the tires will be shredded and chipped. They will then be stored on site before being processed or shipped to other facilities authorized by the Waste Board.