The importance of handling heavy metal plate safely

A spreader beam is used when lifting large objects such as plate. The way the multiple magnets are spread over the length of the beam allows a balanced, safe lift.

Moving plate to and from cutting tables with slings and chains is something that’s easily taken for granted—which is usually when an injury occurs. A slip of the plate as it’s bundled or a chain breaking can seriously injure any nearby worker.

That’s of special concern to today’s metal fabricators. First, the Occupational Safety and Health Administration is becoming more stringent when looking for these types of potential hazards. Second, most metal fabricating companies looking for workers without much success want to keep existing employees safe and productive. Safety has definitely emerged as a driving force in investigating and investing in material handling technology that minimizes the risk of injury to shop floor employees.

As a result, the focus has shifted toward magnetics as a tool to move large and awkward plate and similar workpieces in metal fabricating environments. Magnets are extremely predictable, particularly when the magnetic transport devices have been specifically designed for the job. They also allow the operator safe, hands-off operation during material handling, as these magnetic tools can be operated remotely.

Magnetic Discussion

Even though physics governs the performance of magnets, some in the industry view their use in material handling technology as a sort of black magic. That’s simply not the case because magnets perform as they should. There’s no magic involved.

Magnets produce magnetic fields and attract ferrous substances. The magnet’s lines of force exit the magnet from its north pole and enter through its south pole. (That’s why if you take a sewing needle, magnetize it by running it down the magnet 30 to 40 times, and place the needle on a leaf in stagnant water, the magnetized needle will align itself with the earth’s magnetic field, pointing north to south.)

When it comes to material handling, the focus is on three types of magnets: permanent magnets, electromagnets, and electropermanent magnets. Permanent magnets create their own magnetic field all the time. Electromagnets are made of coils of wire through which electricity is sent to create magnetic fields. Electropermanent magnets are a type of permanent magnet in which the external magnetic field can be switched on or off by a pulse of electric current; these types of magnets maintain their magnetic fields even when electric power is lost. In most industrial settings, electromagnets are used in material handling applications.

But what happens if there is a power loss? Do these magnetic material handling systems just drop their loads when this occurs? That’s not the case because a vast majority of these magnetic material handling systems are sold with battery backups. When power loss occurs, the batteries engage, maintaining the magnetic fields that keep the plate or workpiece attached to the magnet. With annual checks of the battery systems, a metal fabricator doesn’t have to worry about failures in its magnetic transporting devices.

Metal fabricators that have no experience with magnetic material handling systems also might be surprised at their effectiveness in picking up perforated and uneven surfaces. As long as the magnet can positively hold at least some portion of the surface of the ferrous material, the magnet can hold that plate or workpiece securely.

For those working with nonferrous materials, such as aluminum, and some nonmagnetic steel alloys, such as stainless steel varieties, a metal fabricator can use spreader beams that have magnets and slings and chains or vacuum cups. The material handler doesn’t have to swap out the entire spreader bar if jobs transition from ferrous to nonferrous material, saving valuable production time.

Operator Learning Curve

Getting the material handler or the cutting table operator familiar with the controls of a magnetic material handling system doesn’t take a lot of time. Controls are designed to be intuitive, with some systems providing the user a control with icons that visually replicate the magnet setup in the material handling tooling. The user then can activate the magnets needed for the job.

Oftentimes magnetic lifting devices are designed specifically for heavy-duty fabrication jobs.

That doesn’t mean that the user is totally without responsibility when it comes to these devices. The material handler needs to ensure that the surface is relatively clean for an unobstructed contact between the magnet and the metal being handled. For instance, if the material is stored outside during the winter, the material handler should ensure no ice has built up on the metal surface.

Also, the magnet needs to be placed as close as possible to the center of the load. This allows the magnet to maximize its connection to the metal.

Additional responsibilities for the material handler or machine operator involve some basic maintenance tasks. Prior to a shift, someone needs to inspect the magnets to make sure they haven’t been damaged in any way, as this can affect lifting capacity. A magnet’s lifting capacity can be affected by such damage. Magnets should be tested every month to ensure they are operating within the proper performance standards, both mechanically and electrically. If any have fallen outside of acceptable ranges, they should be removed from operation and repaired.

If Considering a Magnetic Material Handling System …

Any metal fabricator considering upgrading to magnets for material handling purposes needs to answer the following questions:

• How much crane capacity is available? The magnets are going to add weight to any lifting scenario, and that needs to be taken into account when trying to calculate if magnets can be used in a certain application. For example, if a company has a 5-ton crane and it wants to pick up 3-in.-thick, 40-ft.-long plate, the weight of the plate and the magnetic tooling is too much for the crane.
• What is being handled? While it might be plate, the company also might want to look at coil handling; tooling can be tailored for each application. Material delivery to the cutting table is one thing, but do plasma-cut parts and the skeleton need to be moved in one action as well? Every scenario comes with its own setup challenges and budgets.
• How thick is the material, and how many sheets need to be picked up at once? If a magnetic material handling system is going to move multiple layers of plate or very thick plate, the end user needs to specify a powerful enough magnet that will provide the right magnetic field penetration to pick up the load. In the case of multiple sheets, a fanning device might be needed to separate unwanted sheets from the lift of multiple plates, say removing the bottom three plates from a pickup stack of six.

These questions are just a sampling of the thorough investigation that is required to engineer the right magnetic material handling system for a metal fabrication application. Every application is unique, and the magnetic material handling devices should reflect that.

These systems do cost more than slings and chains, but the return on investment is typically measured in months, as delivering and removing plate from the cutting table is done much more efficiently. They also are going to reduce the risk of injuries to shop floor personnel, which might be the most underrated reasons for making this type of an investment.

Using blasts of air, a fanning device separates unwanted sheets when a magnet lifts multiple plates.