Advice from the Industry
If you run plate yard moves or feed a burn table all day, you live with two competing pressures: move faster and never drop a thing. Most near-misses trace back to the same gap. The job was planned for a perfect plate, then the crew met real steel with rust, paint, burrs, and flex. The fix is not a bigger magnet or a louder warning. It is choosing the right magnet type, sizing for the steel you actually have, and enforcing clean, boring habits that deliver safe lifts every time.
We build lifting magnets, so our stake is obvious. We still say this up front: a magnet only earns its keep when the plan and the habits around it are solid.
What a Plate Lifting Magnet Really Does
A plate lifting magnet is a below-the-hook tool that grips ferromagnetic material with magnetic force so a hoist can lift, travel, and set the load. Two things make modern permanent systems different from a basic electromagnet or a pair of slings. First, there is no bite into the material, so finished surfaces are unharmed, and one person can rig quickly. Second, in permanent systems, the hold does not depend on live power. Once the magnet is “on,” the flux flows through the plate, and the load stays attached without any continuous current.
That last point is the reason many facilities standardize on permanent technology for critical lifts. If a breaker trips, the lights go out, or a cable gets snagged, the magnet does not let go, even when power is lost.
How the Field is Switched
Under the cover, you are routing magnetic flux. In the “off” state, the field is contained inside the magnet by an internal keeper. Switching “on” sends flux into the workpiece so the plate becomes part of the magnetic circuit. Switching “off” returns flux to the keeper only after the load is down and the rig is slack.
- Manual permanent versions use a lever that rotates internal elements. Suitable for reachable work and repetitive picks. Most include a safety latch that blocks “off” unless the rig is slack, and a V-slot so you can seat on rounds as well as flats.
- Electrically controlled permanent (often called electro-permanent) versions use a short electrical pulse to switch. There is no holding current. This enables remote control, partial magnetization for shedding from stacks, and a fail-safe posture in any power loss. You will see two common pole styles: rectangular for plate and shapes, and bipolar with custom shoes for rounds, angles, and structurals.
- Multi-magnet plate systems spread several permanent magnets across a lifting beam. This is how you keep a long or thin plate from sagging and “peeling.” Well-designed systems add row selectivity and status lights so the operator sees a positive attach before a hoist ever leaves the deck.
Why Crews Pick Magnets Over Slings, Clamps, or Pure Electromagnets
Magnets cut setup time and reduce touches. Operators can pick and set without hunting for the right choker length or fighting with a heavy screw clamp. Permanent and electro-permanent designs use power only for switching, not holding, which reduces energy use and eliminates “drop on power loss” as a failure mode. Remote switching helps keep people clear of the fall zone. And because contact is broad and flat, you avoid bite marks on finished surfaces and can place the load precisely without re-rigging.
That said, magnets are not magic. They reward clean faces, honest contact, and attention to the details below.
What Really Changes Lifting Capacity
It’s one thing to know how plate lifting magnets work, but another to know how much they’ll actually hold once they’re on the steel. The number stamped on the nameplate looks reassuring, but it only reflects perfect lab conditions. Out on the floor, plates are rarely that clean or that uniform, and every imperfection changes the real capacity of your lift. That’s why understanding the factors below is critical for planning safe, reliable moves.
- Air gap: Rust, paint, mill scale, dirt, oil, burrs, torch scars, heavy roughness, and even a slight bow create non-magnetic separation. That separation is an air gap, and it quickly loses holding power. Before the lift, wipe the pole faces and the plate’s contact zone. Knock down raised burrs at the pick spot. Align the magnet so the full face bears. If you can slip a thin feeler under a corner, you are inviting peel.
- Material thickness: Thin plate cannot carry full flux. Below a stated minimum thickness, the magnet will not achieve its rating, and trying to “solve” thin stock by grabbing two sheets at once is unsafe. If your work is thin or long, use a beam with multiple magnets and closer spacing so the plate stays nearly flat during travel.
- Material composition: Not all steel responds the same. Compared to mild steel, higher-carbon and low-alloy steels reduce holding. Cast iron is often about half as effective. Stainless grades that are not ferromagnetic are out altogether. Know what you are lifting and derate accordingly.
- Shape and flexibility: Rounds and pipes give you two line contacts, not a full area. Use the V-slot so you can see those two lines seat cleanly, and start from a lower capacity percentage than you would use on flats. Long, thin plate sags between pick points. That sag starts a peel that grows as you move. Spread the load with more magnets and shorter spans. A single oversized magnet is rarely the right answer for flexible stock.
- Temperature: Heat lowers both the workpiece response and the magnet’s strength. Stay within the stated limits for your model. Hot jobs need a plan, and sometimes a different tool.
A quick way to ground the plan is to take the nameplate number and multiply it by the reduction factors for thickness, surface, composition, shape, and temperature. Write the resulting “usable” number on the traveler and size your move under that value. It takes an extra minute and prevents the ten minutes of arguing that follow a slip.
Choosing the Right Fit for Your Floor
If the operator can safely reach the handle and the work is predictable, a manual permanent unit is durable and straightforward. If the work is varied, access is tight, or you want the operator well clear during attach and release, an electro-permanent unit with remote control is the better choice. For a long or thin plate, plan on a lifting beam with multiple magnets and enough spacing to keep the sheet nearly flat. For pipe and rounds, use bipolar poles or V-slots and start from a lower expected capacity.
We also advise setting up a maintenance routine that preserves the capacity you paid for. Keep pole faces clean and flat. If dings or wear reduce the honest contact area, pull the unit, regrind in one plane, and breakaway-test before returning it to service. Check fasteners, handles, and latches on a schedule. Store magnets clean and dry, ideally on a keeper, so faces stay protected.
Make Every Lift Count
Safe, efficient plate handling comes from matching the magnet to the job, derating for real steel, and enforcing clean, repeatable habits. Choose manual, electro permanent, or a multi magnet beam based on access, shape, and flex, then account for thickness, surface, alloy, geometry, and temperature before you pick. Keep faces clean and flat, seat for full contact, control peel with smart spacing, and keep people out of the fall zone with trial lifts and taglines. Make it real today: pick one lift, write the usable capacity on the traveler, clean and seat the poles, space magnets to keep the sheet flat, and do a trial pick before travel. If you want a second set of eyes, send the job details, and we will review your plan or beam layout with you. Zero drops start here.
Zero drops start with Permadur.