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What Are Lifting Magnets?

Lifting magnets may be used with cranes.
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  • Written By: H. Bliss
  • Edited By: W. Everett
  • Last Modified Date: 30 July 2014
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A lifting magnet is an electromagnet designed to pick up or lift metal objects. These magnets vary widely in size and can be as small as a credit card or as large as a twin-sized bed. Usually, the larger lifting magnets are operated hung from a chain on a crane that is able to dangle the magnet into the location necessary to retrieve the desired object. This type of magnet can be used for a wide variety of purposes, including automobile junking, construction, and demolition and cleanup.

Many kinds of lifting magnets exist. The most common ones are designed to lift heavy metal objects weighing several tons. Others, sometimes called magnetic sweepers, help collect debris like nails, screws, and small metal shards from construction site rubble. Using a magnet to retrieve metal shards from a construction site can help prevent injury and damage to vehicle tires.

A lifting magnet can also be called a retrieving magnet. They are most beneficial in situations in which another method of moving the metal object would be difficult, dangerous, or expensive. These magnets can be dropped into obscure locations to collect metal objects and debris from otherwise difficult-to-reach places. These magnets are also used in underwater situations in which retrieval of metal is required. These underwater magnets can be used to retrieve metal from a damaged submerged vessel like a sunken ship or wrecked oil well.

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Larger, heavy-duty lifting magnets are often called scrap magnets. They can be used to lift large objects like scrapped vehicles. Specially designed scrap magnets have the ability to lift large coils of wire without risking the coil unwinding or telescoping. Telescoping is when the middle parts of the wire fall out of the center of the coil. When a wire coil telescopes, the heavy wire puts nearby people and objects at risk, and the wire is often difficult to re-coil after it telescopes.

If it is not used properly be trained individuals, a powerful lifting magnet can be dangerous. For safety, a high-powered lifting magnet is always placed on the intended lifting object before it is powered on. Placing the magnet on the correct object before powering it on reduces the chances of damaging other nearby objects with an out-of-control lifting magnet.

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David09
Post 7

@everetra - One of my first exposures to magnets, ironically, was not with simple magnets, but with battery powered motors used in electronics kits.

Believe it or not, the motors use magnets. The magnetic charge is used to rotate the motor around a pole and keep it spinning. Once the battery power is cut off, the magnetic field no longer exists and the motor stops spinning.

everetra
Post 6

@hamje32 - I think industrial magnets are great. There are many manufacturing situations where it becomes necessary to pick up magnetic debris, not just large materials, but fine metals that are difficult to see with the naked eye.

I’ve read that they use things like a magnetic separator to clean up these particles and separate them from the object. The magnetic separator sits on a conveyor belt while the object is passing through, and they can perform the same operation over and over on many products.

hamje32
Post 5

One of the first scientific experiments I did in school was to create a magnet. It’s quite easy, actually. You just take an iron nail, wrap it with some copper wire all around, and then connect it to one or more batteries. Instantly you create a magnetic field around the nail.

The orientation of the magnetic field depends on what direction you used to wrap the wire. Either way, you will create a simple magnetic force field if you will, and can begin lifting things like paper clips.

Obviously at this scale you’re not creating industrial magnets such as those described in the article, but the principle is the same.

JimmyT
Post 4

@jcraig - Another good use for neodymium magnets is remagnetizing other less powerful magnets. They can do that, since the pull is so strong. One the other end, though, they are pretty good at demagnetizing things like credit cards, so keep them away from your wallet.

I have never thought about using powerful magnets to pull up pieces of metal from below water. Would an electromagnet still work in a situation like that, or would the electric charge spread into the water and cause a problem? If that is the case, what type of magnets are used?

jcraig
Post 3

I don't know if anyone here has used neodymium magnets, but they are a very handy thing to have lying around the house. I use mine fairly often. They are a lot more powerful than fridge magnets and can pick up a lot heavier things.

I do a lot of DIY stuff, so I am constantly using my magnets to pick up nails and screws from hard to reach places. Like the article kind of mentions, having a good magnet is good if you spill any nails somewhere, because you can pick them all up a lot easier than crawling around on your hands and knees.

Another good trick if you ever drop something through a crack is to put one of the magnets on the end of some type of stick. Then you can just put it through the crack or whatever it is, and pick things up. I have had a couple of times where I dropped my keys unlocking the front door and dropped them through the boards in the porch. Having the magnet was a lot easier than crawling underneath to get them.

cardsfan27
Post 2

@mattheewc23 - Basically, what happens with an electromagnet that is different than a permanent magnet is that the metal is not magnetized to start with. For example, the big junk yard magnets are just big pieces of iron. Once the electric charge is put through them, though, all of of the atoms reorient themselves so that all of the poles are facing the same direction, which is basically the definition of a magnet.

Whenever the magnet comes in contact with the steel of a car or some other metal, the pull is so strong from the electromagnet that the electrons in the second material are changed, as well. In the end, you have one piece of metal with mostly north facing poles and the other with south poles, which equals an attraction.

If you have iron shavings, you can do the same type of experiment at home. You just put the shavings on a piece of conductive metal, like iron, and then connect some type of battery or electric charge to the metal, and all of the shavings with spin until they are all facing the same direction.

matthewc23
Post 1

The thing I never understood exactly is how an electromagnet works. Like the article mentions, that is how the big crane type magnets are able to pick up things that are very heavy, but I could never figure out how it does that. Is there some special type of metal that is used, and how does the electricity automatically turn a regular piece of metal into a magnet?

As far as using the magnet, is there a certain weight limit that the magnet can pick up? Is that something that is determined by the electric charge?

The other interesting thing the article mentioned was needing to have the magnet on top of the thing being lifted before it was turned on. That is something I had never really thought about before, but it makes a lot of sense. Even if you are picking up a nail or something with a magnet, it can start to come up before it comes in contact with the metal. I'm sure you could have some major problems if the same thing happened with a car.

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