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Understanding lifting magnets and residual magnetism

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article image Lifting magnets with no residual magnetism are the safest option.
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Residual magnetism in lifting magnets occurs when a magnet fails to turn completely off.

This magnetic flux results from a circuit being created between the rare earth magnets inside and the steel body of the magnet. The level of residual magnetism depends on the shunting technology and the overall design of the magnet.

So how does residual magnetism affect your lifting magnets? The following three examples show the effects of residual magnetism found in lifting magnets and prove why magnets with no residual magnetism are the safest option.

Extreme residual magnetism

  • Extreme residual magnetism will cause the magnet to collect ferrous particles and debris even after it has been turned off
  • Debris will likely cause an air gap on subsequent lifts and may permanently damage the magnet. This can significantly de-rate the magnet’s SWL (Safe Working Load) and the magnet could fail a pull test
  • High risk of hand injuries if the operator tries to manually separate the magnet from the load
  • The material being handled will also be damaged by any debris stuck to the magnet.

Low residual magnetism

  • A good quality passive shunting magnet has a small amount of residual magnetism, although not enough to risk hand injuries
  • The magnet will still require regular inspection for debris; however, you can expect it to collect much less debris than the first magnet.

No residual magnetism

  • This magnet uses active shunting technology, which allows it to be turned off completely
  • It is the safest type of magnet and is also unlikely to collect any ferrous debris after being turned off
  • In the event of damage to the working surface, replacement pole shoes can be fitted safely and easily using basic tools in your workshop.

MSA Pro-Lift and Magswitch lifting magnets are designed to have a clean break of magnetic flux at the OFF position.

MSA Magnetics ensures the highest industry safety standard as well as ease of use for their industrial lifting magnets.

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