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Selecting Between Deep Field Passive Shunting And Shallow Field Active Shunting Lifting Magnets

Hand Injuries

Many Australian companies have a strong focus on reducing hand and wrist injuries. They may be interested in an Active Shunting Magnet due to it’s more gentle actuation. Deep Field Magnets can be quite forceful when being turned on and off, particularly when it is operating too far from its maximum magnetic saturation thickness. For example, a 3-tonne Passive Shunting Lifting Magnet is not rated for use below 30mm and is a happier operation in the 50mm-80mm range.

The other reason Active Shunting Magnets are good at preventing hand injuries is to have no residual magnetism. This eliminates the requirement to remove swarf and grit from the bottom of the magnets between lifts thus reducing the risk of laceration type hand injuries.

Do you intend to lift material less than 10mm thick?

If so, be aware that many Passive Shunting Magnets are not rated for it. The two main reasons are that you have to apply so much force to the handle that the magnet can be damaged and once the magnet is actuated, so much of the flux is wasted below the sheet metal.

De-stacking

If you’re using the magnet to lift sheet or plate off a stack, you’re most likely better off with a Shallow Field to reduce the chance of picking up multiple pieces.

Preventing damage to Materials

Does the material have to be handled carefully to reduce the risk of scratching it? If so an Active Shunting Magnet with zero Residual Magnetism is the way to go. See our video on Residual Magnetism for more detail on this.

Handling billet or very thick steel 40-80 mm plus

A Passive Shunting Magnet is usually a good choice and really come into their own here. Just ensure that the magnet has a two-action control that prevents accidental discharge as per the Australian standard. We see many for sale in Australia that doesn’t.

We are not playing favourites here, we highly recommend our Passive Shunting Prolift range, they are robust and dependable. We also really like the Active Shunting Magswitch products for their technology and all the solutions they offer.

At MSA we want to see the right magnets used for the job, safely and at the best price whether it’s a Prolift or Magswitch MLAY.

Contact MSA today for advice on selecting the right Lifting Magnet for your application.

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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