Lifting attachments: The coil carriers2 January 2024
Not all loads are best lifted by hooks. There are almost as many below-the-hook lifting attachments as there are types of load. Indeed, as Julian Champkin discovers, there are dozens of ways just to lift a coil of wire...
Loads come in almost infinite variety. So do the devices for lifting them. Even for a single product, the number and designs of below-the-hook lifting attachments can be huge. An entire magazine would hardly scratch the surface; a single article would be even more incomplete. To demonstrate which, we shall restrict ourselves in this single article to attachments for lifting just one single type of load: coils of metal. And, as you will see, we can find getting on for a dozen different attachments designed especially for lifting that single type of load.
Metal coils, of steel or aluminium, as wire or as narrow strips of metal, are ubiquitous in foundries, factories and transport yards, and lifting them is a very common need. Many different below-the-hook devices are available to do so. Their shape – round, with a hole in the middle – offers several obvious possibilities. Their weight, however, is generally of the order of tonnes, so manhandling is not an option.
Simplest in concept, and perhaps the only means available to, say, a transport contractor that only very occasionally carries such loads, is a chain through the hole, attached at each end to the hook of the lifting device. It works, but the disadvantages are obvious. The chain may abrade the steel wire and damage it, or at least any coating it may have; a rigger has to fit the chain and attach it to the hook, which is a potentially dangerous operation, and if the coil is lying flat on the ground, passing the chain underneath it will be either difficult or impossible.
Synthetic webbing as a rigging device would avoid the abrasion risk, but would still leave the other disadvantages. We begin to see the need for specialist devices.
Of which there are many. The C-hook is perhaps the simplest and the most ubiquitous. The lifting point is at the top of the C; the bottom of the C is flat, to go through the hole in the coil. They are available from many manufacturers, in various sizes and capacities. Caldwell, for example, offers its heavy-duty model 82, of 10-ton capacity. Like most, it is counterbalanced so that it hangs level when empty as well as when under load. The horizontal, lower edge – the ‘saddle’ – on which the inner radius of the coil sits is curved, so that no sharp edges will damage the coil; the two inside corners are cut away in three-quarter circles, again so that they do not contact the edge of the coil. It is available with optional padding to still further reduce the risk of damaging the coil, and it can handle a wide range of coil widths. Other Caldwell models can handle up to 50 tons.
For smaller, lightweight coils it has its model 80H Dixon coil hook, which has a pivoting wedge at the lower end of the ‘C’. This allows coils that are stacked horizontally to be upended to the vertical: the wedge catches on the inside of the coil and pivots when the lift is started, keeping the coil in place as it tilts upright without falling off the hook. The weight of the coil holds the pivoting wedge in the vertical position during further lifting, so the wedge then acts as a retainer. Capacities are up to 3.5 tons.
If your coils are stacked horizontally and you want to lift them in that orientation Caldwell has eye coil lifters in various sizes. These have two L-shaped legs that go into the centre hole and then move apart until the coil is supported from both sides underneath. Its 83EW – extended width – model handles coils with internal diameters of 16-24in. They automatically adjust to the diameter being lifted. Capacities are from 0.5 to 7.5 tons.
There are also telescoping coil grabs, and parallel-linkage coil grabs. Bradley Lifting, of York, Pennsylvania, make both types, as well as C-hooks and many other designs. The company was founded in 1972 as a small business in his basement by Harvey Bradley, an engineer experienced in the design and maintenance of mill-duty overhead cranes and below-the-hook pieces. It is now rather larger and is part of Xtek Inc. of Ohio.
“Each device has a unique set of advantages,” says the company. “C-hooks require no external power to operate, and work perfectly where high count handling of coils is required and where clearance is available for inserting and removing the coils for the hook. Telescoping coil grabs offer an advantage in safety by providing engagement on both sides of the coil, and take less room to operate. They are ideal in automated systems, coil storage areas, or in situations where space is at a premium.”
The idea of them is simple. Lugs project downwards from a horizontal telescoping bar. When the bar telescopes inwards, the lugs move towards each other until they fit into the central hole in the coil, one each side of it.
“Motorised telescoping coil lifters are the preferred solution when handling coils where the axis is horizontal,” says Bradley. The telescoping legs offer the ability to handle a wide range of coil diameters and widths, while still maintaining a low headroom profile.
Motorised rotation about the vertical axis, hold-down arms for un-banded coils, and digital weighing systems can be added, as can other features.
Another design is the parallel linkage coil lifter. This grabs the coil in the same way, on lugs that move from each side of the coil into the central hole, but the lugs, instead of telescoping, are mounted on vertical arms that swing in and out from the top-bar.
“They have the advantage of consistent width outside of the coil, and are best in tight clearance situations, or where there is an extreme range of coil widths to be handled,” says Bradley. “But this type of grab requires more headroom to operate. Telescoping lifters require less headroom to operate, and in most cases, offer the same width advantages as a parallel linkage lifter.” However, when an extreme range of coil widths are present, the parallel linkage can limit the minimum width of the grab.
Also in Pennsylvania, US, Drafto has been manufacturing various types of coil lifters for over 20 years, including C-hooks and grab lifters. (The name, by the way, comes from ‘drafting table’, the product they originally made back in the 1930s.) They are below-the-hook specialists, aiming for minimal downtime and production tools that give easy and headache-free maintenance.
Its coil lifting devices include rack and pinion lifters (‘coil grabs’), parallelogram (‘scissors type’) lifters, vertical ‘eye to the sky’ lifters and C-hooks. Coil edge protection features include a patented rolling belt, saddle trip switches, edge limit switches, ID photo sensors and indicating lights. Its coil grabs are also available with integral weighing systems, which can optimise yields and reduce handling time: weighing objects as they are being moved eliminates unnecessary operations. Performance and durability of a belowthe- hook weighing device are unmatched by other types of scales, says Drafto: objects cannot be dropped onto a crane scale, nor do they collect dirt and debris in the way a floor or pit scale can. The single point loading guarantees accuracy and repeatability, and the initial cost is usually much less than similar capacity stationary scales.
Spanish below-the-hook specialist Airpes is part of the Crosby Group. It too offers specialised attachments for coil lifting. In particular, it offers tongs specially designed for automated lifting systems.
It points out that the percentage of new crane installations that require automation is growing, but also growing is the demand for retrofits and requests for cranes to be able to be easily converted for more automation in the future. The firm designed its automation-ready lifting tong to be a standard product that meets most of the needs of any automated crane.
They are typically used to lift 25-60-ton coils but can be adapted to suit end users’ requirements. They are compatible with any crane in the steel and aluminium sectors and can be installed as a retrofit or part of a new build.
In semi-automatic applications, some of the lifting tong features assist the operator but allow more manual control. Using it in a fully automatic mode can be useful in demanding environments – such as steel mills – in repeating the lifting process without manual input.
In those contexts the tongs act in concert with the crane’s system to position the crane within millimetres of the load, engage the tong to the load, and carry it to a destination that can vary with the work to be performed on the coil, the type of steel, and the size.
The automation-ready lifting tong can be adapted to a rigid mast crane, a wire rope hoist, or an existing crane, in various capacities and duty cycles. A specific hook and lower block package can be retrofitted to the existing crane or built new.
It can land a coil not just at a fixed point, such as a storage rack or a de-coiler, but also on a truck or railcar. Airpes describes this last as a “big deal”, on the grounds that trucks and railcars have different configurations, wheelbases and deck heights, and are positioned differently every time. The tong can account for all those differences and still land the coil perfectly. The software always calculates the optimal path.
Previously, says Airpes, there was no steel coil tong formally designed for automation applications – most were modified after delivery by the next person in the value chain. The result was that the crane builder has to agree with the automation integrator on a custom package for the end-user, which was a time-consuming process, not repeatable for other applications, and involving much re-engineering and modification. Airpes, collaborating with partners as Janus Automation, says it has come up with a product that short-circuits this process.
Steel coils are, of course, ferromagnetic, which means they can be lifted by magnets.
The strength of a magnetic hold depends very greatly on the area of contact between the load and the magnet. Coillifting electromagnets, therefore, have their lifting surfaces shaped or adjustable to fit the load. Italian magnet specialists Gi-da has its ERBI 57.220-SP-HT, which can lift wire coils that are stacked either vertically or horizontally – the application it shows is of an excavator-type machine unloading 3.0t coils from a flat-bed truck. The magnet has a 360° rotating suspension, powered by the hydraulics of the excavator – it therefore allows loading of coils in parallel rows on a wagon or truck without having to move the loader.
It can handle vertical coils up to 2,400mm long, with outside diameter up to 1,200mm and weighing up to 3t. It can handle two coils at once, provided they are well aligned and with an overall length not exceeding 2,400mm. The magnet takes 10.5kW of power.
It can also handle so-called ‘Jumbo’ coils, which are compactly rolled and therefore of high density. Lifting them with their axes pointing vertically, it is rated for diameters up to 1,300mm and weights up to 5t. They can be used on materials with temperatures up to 300°c.
They are claimed to be faster and more practical than any mechanical clamp. The Gi-da ERBI 57.220-SP-HT is used, says the company, with excellent results at a well-known steel plant in the province of Udine in Italy to load wire coils on rail cars. The tool has made it possible to reduce the loading time of each wagon by 40%.
Germany company Dimet also makes specialised electromagnets for coils. Its EMGB series, for lifting by the flank of the coil – that is, with the coil axis horizontal – has a special welded housing developed for use in difficult operating environments and has reinforced shielding of the terminal boxes for shock protection. It also has a large heat transfer surface (when current is flowing in an electromagnet, heat is, of course, produced, and this has to be dissipated to the surroundings). The EMGB can handle loads that are hot as well: a heat-insulating seal makes it possible to lift loads that are up to 650°c.
Its EMGR series is for lifting by the facing surface – i.e. the flat face – of the coil. It has similar heat and shock protections, making it also suitable for use in metallurgical and metal processing plants. The heaviest-duty member of the series, the 250/A, can lift coils of up to 42t.
The obvious conclusion is that if you have a metal coil to lift, you are spoiled for choice in attachments to lift it with. The same is true of metal plates, steel beams, concrete pipes, cardboard boxes, wooden panels, or almost anything else you care to mention. The choice is yours.