Handling of a heavy load by magnet.

Why magnetism to handle a steel load?

Handling a heavy load involves risks, regardless of the lifting means used. Some means are visually more reassuring, but are not necessarily more secure. A sling or a chain is visualized and reassuring, unlike a magnet which holds a load by magic... or almost! In reality, nothing magic but a proven physical principle.

What advantages do magnets have?

Putting a magnet on a load and lifting it instantly allows a considerable gain in productivity. If your activity consists of repetitive loading and unloading, your capacity will be increased in beautiful proportions.

Wear is slow. A sling can break down quickly and sometimes instantly if it gets snagged in a rack or a sharp corner. It is therefore crucial to notice it as soon as possible and change it. A breakup would be catastrophic.

The electromagnet is for its part located on top of the load, and in the vast majority of cases it has dimensions that are smaller than the load. Since it is set back, the electromagnet therefore has little chance of snagging. Even if its carcass hits a stanchion, the electromagnet has an immensely high resistance to shocks. Its mechanically welded steel body several centimeters thick is almost unbreakable.

An electromagnet is nearly indestructible. So indestructible?

The most common wear comes from the friction of its contact surface with the sheet or the slab. Several tens of thousands of cycles are necessary for the abrasion of the steel/steel contact to plane the North and South poles. However, this is a point to be checked very regularly because the surface condition can create irregularities and therefore an air gap. These spaces between the magnet and the load interfere with the passage of the magnetic field and the induction is therefore weaker. This is often negligible but over the years, we can lose 10 to 30% of the maximum force of attraction.

In case of wear, is the crane operator safe?

The bottom surface condition should be monitored every week, at worst every month. If the lower surfaces are rounded, dug, planed down to the wear bead, return the electromagnet to its manufacturer. He will carry out an expertise and control of the CMU. While waiting for this technical revision, be aware that an electromagnet is calculated and tested so that its maximum lifting force, called tearing force, is at least equal to twice your WLL. In other words, if your sheet weighs 3000 kg, the electromagnet is designed to carry at least 6000 kg. This is reassuring information because the safety factor includes surface defects and the air gap due to normal wear. This should in no way diminish the vigilance of the user and the maintenance department as to the condition of the device.

The crane operator is safe, as long as he respects two basic rules: use an electromagnet checked at least once a year by an organization or a manufacturer, and never be near the load.

This is also a huge advantage of the electromagnet: no need to approach to slip a sling or hooks. The operator remains several meters away and activates the buttons of his radio control from a secure location.

But what is the principle of an electromagnet?

The principle is easy to understand. Defining and realizing a quality electromagnet is more complicated.

The principle is as follows: A coil made of copper or aluminum, which is slipped into a permeable steel carcass. A resin is cast to maintain the coil in the frame but also to dissipate the heat created by the winding in operation. The voltage is therefore sent to this coil, whose many turns and the section of its conductor are calculated for the best possible performance while avoiding overheating. We want to create an electromagnet, not a resistance heater...

Which magnetic technologies to lift and move a steel mass?

Electro magnet:

Other technologies: Permanent magnets and Electro-permanent

What capacities for the electromagnet? Mini and Maxi

Can the load drop?

Types of metals

Principle of an electromagnet / AT coil / permeable circuit / Current density / Heating

Influence of load temperature on magnetism.

The risks associated with magnetic fields / induction / human health