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How Well Do You Know Lifting Magnets?

Ever heard of Residual Magnetism? What is it, and how does it affect your Lifting Magnets?

Residual Magnetism occurs when a magnet fails to turn completely off. The magnetic flux is a result of 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.

These next 3 magnets are a good example of Residual Magnetism found in lifting magnets and why magnets with no Residual Magnetism are the safest option:

Extreme Residual Magnetism

  • The 1st magnet has quite extreme Residual Magnetism, which 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 score the magnet. This can significantly de-rate the magnets SWL (Safe Working Load) and the magnet could fail a pull test
  • High risks of hand injuries if the operator uses their hands to separate the magnet from the load
  • The material being handled will also be damaged by any debris stuck to the magnet

 

 

Low Residual Magnetism

  • This magnet is a good quality Passive Shunting magnet. It has a small amount of Residual Magnetism, although not enough to risk hand injuries
  • Will still require regular inspection for debris, however, you can expect it to collect much less than the first magnet

 

 

No Residual Magnetism

  • The 3rd magnet uses Active Shunting Technology which allows it to be turned 100% of the way off
  • 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. We ensure the highest industry safety standard of our industrial Lifting Magnets while making sure they are easy to use!

Click here to watch the video now! Need a better understanding? Contact our magnet experts today.

Are you aware there are deep field and shallow field Lifting Magnets available?

Deep field (Passive Shunting) Lifting Magnets have been used for many decades in Australia. In the last ten years shallow field (Active Shunting) Lifting Magnets have been gaining in Popularity.

To understand why we need to look at the differences and what that means in the workplace.

Deep field magnets are generally durable robust pieces of equipment, but many people are not aware that they will only lift their advertised capacity at the depth of their magnetic field.

This depth varies between sizes. An average PML 500kg magnet has a 40mm deep field. This means it is only rated to lift 500kg if the material you are handling is 40mm thick. If the material is 20mm thick this 500kg magnet is rated to lift 350kg.  A 1-tonne deep field magnet typically has a 60mm deep field, so on 20mm material thickness, it is rated to lift 350kg which is the same as a PML 500kg magnet.

A shallow field magnet rated to lift 400kg has a 12.7mm deep field so it can lift 400kg of 12.7mm material. When you are handling 20mm plate it is still rated to lift 400kg.

Interestingly, most deep field magnets are not rated to lift material less than 10mm thick while many shallow field magnets are rated on material as thin as 0.5mm thick.

So, what that means in the workplace when you are using deep field magnets, is there is more potential to mismatch the magnet to the load.

A mismatch like using a 1-tonne PML with a 60mm field to lift 15mm plate will result in the lever being very hard to actuate and very hard to turn off. The lever will be very forceful on release resulting in a risk of wrist injuries.

Furthermore, a calculation is required by the operator to ensure the magnet is rated to lift the material at the given thickness.

Using a shallow field magnet on material from 0.5mm to 25mm thick will ensure that the levers actuate in a gentle manner, reducing potential wrist injuries while reducing the risk of operator error due to misunderstanding their magnets capacity on various thickness’s.

At MSA we supply both types and are looking forward to offering advice on which type suits your requirements.

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