July/August 1997
So you’re in the market for a new lifting magnet or grapple? This primer examines the factors to consider to ensure you buy the one that best meets the needs of your operation.
By Kristina Rundquist
Kristina Rundquist is an associate editor of Scrap.
Lifting magnets and grapples. They’re two of the workhorses of the scrap recycling industry. Processors, in fact, would be hard-pressed to move, load, or unload scrap, or feed material into processing equipment without them. For that reason, there’s hardly a scrap facility that doesn’t have at least one or the other—although typically facilities have both. And that adds up to a lot of magnets and grapples being bought and used industry-wide each year.
So let’s assume you’re in the market for a new magnet or grapple. What factors should you consider to ensure that you select the best one for your needs? This overview offers guidance to help you make the right decision.
The Magnetic Field
The first decision you have to make, of course, is whether you need a magnet, a grapple, or both.
If you process nonferrous scrap exclusively, for instance, a magnet wouldn’t be of much use. A grapple would be the answer to your material handling needs. But assuming your operation handles a mix of nonferrous and ferrous scrap, or ferrous scrap exclusively, then a magnet becomes a viable option. At this point, the challenge is to decide whether a magnet can effectively and efficiently handle your materials.
While electro-lifting magnets can handle most types of ferrous scrap, they’re particularly good at picking up small, loose scrap such as shredded ferrous, material cut to short lengths such as 18-inch foundry-grade scrap, and material stacked in short piles.
Magnets are also helpful in serving as last-minute classifiers in that they pick up ferrous material and leave nonferrous items and other potential contaminants on the ground. “Sometimes you get nonferrous materials mixed in, and a grapple will grab everything while a magnet will leave the nonferrous behind,” notes one magnet maker.
Depending on their configuration, magnets can also get into the corners and along the edges of railcars and trailers, picking up small bits of scrap that other unloading equipment might miss. They can also sweep the ground around a scrap pile or railcar, thus improving plant housekeeping and preventing injuries and flat tires.
Having decided that a magnet is what you need, there are several key factors to consider, including:
Price. A magnet’s price is largely based on its size—expressed in terms of its diameter in inches—and the quality of its components. While most manufacturers try to stay within the same price range, there are differences. Some produce both a low- and high-end product, with the less expensive magnets not necessarily being lighter, but simply possessing fewer options.
In the end, most manufacturers and scrap managers agree: You get what you pay for. And that, according to one magnet producer, is about $12,000 for a 55-inch magnet—reportedly the most common size—with prices ranging up to $75,000 for larger ones.
The good news is that when properly used and maintained, a magnet can last anywhere from five to 25 years, depending on hours of use. “It’s not a perishable item that you throw out after a year,” affirms one manufacturer.
While price may be the deciding factor for some processors, others assert that factors such as the magnet’s physical characteristics and operational capabilities come first. “We look at function,” says one scrap processor. “We look at what it will do and whether it will suit us. If it can do what it has to, it’s worth the money no matter how much it is.”
Size and Lift Capability. In general, the larger a magnet’s diameter, the heavier it will be, and the more it will lift. But recyclers can’t simply choose the largest, most powerful magnet on the market. Their choice is limited by the size of the crane that will operate the magnet, as well as the power available from the crane’s generator. No matter how big a magnet you want, if your crane can’t lift or power it, end of story.
The goal in this regard is to maximize the crane’s, as well as the magnet’s, capabilities. As one manufacturer confirms, “Once you’ve determined the crane’s load limit, you look at the magnet weight, plus what it will be lifting, and from there you determine what size is proper.”
A word of caution is in order here. While most scrap operators know the weight limit of their machinery, cranes have been known to tip over. As a result, rather than tempting fate by using the largest possible magnet, it’s prudent to “always go with the smaller magnet,” advises one producer. Although some strength is sacrificed by using a smaller magnet, recyclers can “pick up performance through speed,” says another manufacturer, concluding, “They may need a lighter magnet, but it will move more material.”
Selecting the right magnet size also depends, to a large extent, simply on how much you plan to operate the magnet. Will you, for example, use it to load railcars for eight hours a day, or 16 hours a day? Also, how much material do you need to move and how fast? As one magnet expert observes, “There’s no sense in buying a 72-inch magnet that can load 40,000 pounds in two minutes if all you have to do is unload two railcars a day.”
Shape. While magnets come in a variety of shapes—including square, rectangular, oval, and round—scrap processors have always seemed to gravitate to the round configuration. This preference is due, in part, to their belief that a circular magnetic field delivers optimal lift. Another reason is that the rounded edges of round magnets are less apt to damage railcars, trailers, and other equipment than, say, the more pointy corners of square or rectangular magnets. Another reason processors prefer round magnets is simply habit. “We get locked into doing things the same way,” a recycler states.
Some of the other magnet configurations, however, are becoming a more common sight in some on-site scrap operations at steel mills, in which square or rectangular magnets often fit the scrap loading and unloading bill better than round magnets.
Construction. Another issue to consider is whether a magnet has a fabricated or cast case. Those taking the cast side argue that a single-pour shell increases a magnet’s durability. Asserts one manufacturer, “We’re talking about increasing its life by years because in casting you can dictate the type of material that’s being poured. With fabricated cases, you can’t control quality as well.”
On the other side are those who favor fabricated cases, with one magnet maker saying, “Cast cases tend to crack in certain areas, which means that fabricated plates—because of stress points—come out ahead.” Of note, he adds, the bottom plate of fabricated cases is welded twice—once from the bottom and once from the top before the coil is loaded—which adds to their strength and durability. Also, fabricated cases can be made relatively easily and quickly in virtually any size, while custom-sized cast cases usually require new patterns to be made, which can add time and cost to the manufacturing process, says a magnet expert.
Whatever the pros and cons, however, cast cases are the most common type for lifting magnets used in scrap handling operations, though one manufacturer says fabricated cases are gaining ground.
On the issue of durability, while scrap processors could purchase less rugged magnets, most prefer to go the route of the heavy-duty, deep-field magnet. “Heavy-duty magnets have a thicker bottom plate and stronger casing,” notes a scrap processor. “They’re just ready to take abuse.
In our business, too, the material is piled up and you’re basically moving it between trucks and piles. You want to make sure that every time you turn the magnet on it counts.”
It’s also helpful to know a few facts about the magnet’s internal coil, namely whether it’s copper or aluminum. Most likely it’ll be aluminum, considering that 95 percent of new magnet coils used in the scrap industry today are aluminum. As one magnet maker explains, “Copper is a better conductor, but it’s much heavier and costs quite a bit more. Customers are looking for less weight but similar performance, so we’ve turned to aluminum.”
Duty Cycle. Selecting the right magnet also depends on knowing its duty cycle—that is, the percentage of time a magnet is on vs. the time it’s off. A 50-percent duty cycle, for instance, means the magnet should be on the same amount of time it’s off in any given lifting cycle. If it operates for one minute, then it should be on 30 seconds and off 30 seconds.
Different styles of magnets have different duty cycles, just as different cranes—such as hydraulic excavators vs. lattice-boom cable cranes—place different duty- cycle demands on magnets. Notably, hydraulic excavators are much quicker, which means the duty cycle rises accordingly. “Hydraulic cranes are forcing us to make duty cycles higher,” notes a magnet manufacturer. “Thirty years ago, it was normal to have a 50-percent duty cycle, but today that number is up to 75 percent.”
Aside from matching the duty-cycle to the equipment, there’s also the consideration that magnets that run warm are less efficient. “Most magnets drop production in the afternoon,” says a magnet producer, “so you want one that runs cool so you’ll get a similar performance all day long.”
And last but certainly not least there’s this issue:
Service. When it comes to customer and product service issues, most manufacturers offer a one-year warranty and a crew of sales and service reps. One magnet manufacturer also notes that it offers magnet awareness seminars as well as magnet maintenance training courses for its customers.
Aside from a warranty, the most important service a magnet producer can offer is time, say several scrap executives. “You want to make sure you deal with a company that will listen,” asserts one processor. “With any equipment you buy, you need a company you can relate to. Will they support you, or will you be out there on your own?”
What’s Your Tine?
And then there are grapples, which are particularly effective “in situations where you’ve got high production and you want to move a lot of material quickly, especially when you’re feeding a shredder,” says a grapple maker. “They’re designed to handle materials that are awkward in form that typically, when you’re using a magnet, won’t give you a full payload.”
Grapples are often used, for example, to pick up No. 1 and No. 2 scrap, feed car hulks into a shredder, and grab thin or sheet metal that lacks the bulk needed for effective and efficient magnet use.
As for which type of grapple to buy, that depends on the intended use, states one grapple expert, who notes, “The selection should be 100-percent application-driven. It depends on whether you’re feeding a shear, a shredder, or a baler, although you can get one that will be versatile enough for all three applications.”
Still grappling with the issue? Weighing the following factors can make the choice a little easier.
Price. As with magnets, grapples are available in a variety of price ranges, with a less expensive model costing about $14,000 and a “Cadillac” version anywhere up to $23,000. Of course, any special features in the grapple will boost its cost, with one such feature being its rotation. Does it come equipped, for example, with hydraulic rotation where an operator can mechanically turn the grapple into the best position for lifting material? If so, be prepared to pay more. Then there are grapples with knock-around rotation, which means they rotate in whichever direction they’re knocked. And then there are grapples that don’t rotate at all.
Size and Lift Capability. Grapples are described in terms of how much material they can grab, usually expressed in cubic yards. The most popular models are those with 3/4-, 1-, or 11/2- cubic-yard capacity. As with magnets, however, processors must buy a grapple whose size doesn’t exceed the weight limits of the crane holding it. “You don’t have much choice,” notes a grapple expert. “You end up with whatever the manufacturer suggests.”
This weight issue has prompted grapple manufacturers to pursue the “ultimate goal” of building a grapple “with the lightest weight and the largest capacity,” says one producer. “You don’t want to be moving the weight of the grapple. You’d rather be moving scrap.”
Style. Grapples are generally divided into two varieties: orange peel and contractor’s. The former have tines that open and close like fingers or, as the name suggests, the sections of an orange peel. The latter have two facing jaws that open and close like a clamshell, with short tines that overlap like interlocking fingers.
According to one grapple maker, 80 percent of scrap companies use orange-peel grapples “because they’re more conducive to the material they handle and they enclose the material from four sides, whereas contractor’s grapples only enclose material on two sides.”
Another reported benefit of orange-peel grapples is they “hang straight down, which enables the operator to rotate them and get them into different positions, while contractor’s grapples are fixed and can only work on material that’s parallel or perpendicular with the boom,” maintains another grapple expert.
Whether buying an orange-peel or contractor’s grapple, you have to decide what kind of tine configuration you want. When it comes to orange-peel models, customers tend to prefer four tines. But, as one grapple producer points out, “If you handle relatively small pieces of material, you may have to work with five because they offer better closure and will penetrate a pile of small matter better.”
Orange-peel tines also come in full or semi configurations. What’s the difference? When full-blade tines are in a closed position, the grapple completely encloses the material, whereas with semi-tines there are open spaces. “The scrap industry standard is the four-tine, semi-blade configuration,” states a manufacturer, adding that “the only purpose for a fully enclosed grapple is in a yard where you’re handling foundry punchings.”
Contractor’s grapples also come in a variety of tine configurations, most notably two tines into three, three into four, or four into five.
Service. A well-maintained grapple can last six years or more when operated 10 hours a day, five days a week, say grapple manufacturers.
Warranties that cover material and workmanship are generally six months across the board. But with competition rising among grapple makers, some say the quality of service could become one of the top criteria in deciding which grapple to choose. “It’s getting fiercely competitive,” agrees one grapple manufacturer. “If I were in the market for a grapple today, one of my priorities would be to look at how a company follows through with its product.”
The Best of Both Worlds?
If you still can’t decide between a magnet and grapple, why not go with both? Combination magnet-grapples are available, giving processors the advantages of both in one attachment.
Some recyclers who have purchased such combination attachments say they now can’t imagine running their operations without them.
Others, however, just see the magnet as taking up valuable grapple lifting space. If they want to use a magnet, they assert, then they’ll switch attachments or bring in another crane. “We don’t believe in the concept of a magnet in a grapple,” says one grapple manufacturer. “The reason people buy separate attachments is because the magnet takes up space in the grapple and reduces the amount you can lift in one load. The other reason is that it adds weight to the crane.”
One recycler, a believer in the magnet-grapple, counters, “We don’t believe we lose capacity. The product is designed to pick up material with the magnet underneath. You flip on the magnet, close the grapple on the scrap, and you can pick up as much of a load as you would with a 66-inch magnet.”
As a specialized attachment, the magnet-grapple lacks the widespread use of separate magnets and grapples, though some manufacturers say it could find broader appeal in the future. Currently, the combination unit is available with a 3/4-, 11/4-, or 13/4- cubic-yard capacity.
As for price, a combination magnet-grapple costs about the same as if you purchased a magnet and grapple individually.
* * *
Whether you’re in the market for a magnet, a grapple, or a little of both, scrap operations managers and equipment manufacturers recommend buying from a company that has a solid reputation for making quality products.
Of course, many processors have certain favorite manufacturers with whom they’ve dealt for years. “We tend to build up confidence over the years and go back to the same companies,” says one recycler. And as another adds, “No matter what the equipment or the application, we always go back to the company we’re comfortable with.”
And that’s fine. The important point is to not let familiarity breed complacency. Your ultimate goal when you’re out there seeking to purchase a new magnet or grapple is to go with the manufacturer and the attachment that offers the best fit for your operation’s needs. •
So you’re in the market for a new lifting magnet or grapple? This primer examines the factors to consider to ensure you buy the one that best meets the needs of your operation.