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How to choose the correct lifting magnet

Lifting Magnet

When choosing a lifting magnet, there are a few factors, but very important ones, that need to be taken into consideration to ensure effectiveness and safe workplace material handling practices.

Considering both the weight and the thickness of the material will help determine if an Active Shunting (Shallow Field) Lifting Magnet  or a Passive Shunting (Deep Field) Lifting Magnet is more suitable, as well as which size of these magnets is required for safe & effective lifting capabilities. It is important to also keep residual magnetism in mind when selecting your lifting magnet.

Let’s have a look at the two types of lifting magnets, and what the difference between them is:

Active Shunting / Shallow Field Lifting Magnets

Active Shunting or Shallow Field Lifting Magnets are rated to lift material as thin as 0.5mm and are best to use on materials that are less than 10mm thick as they have a smaller magnetic field. It is more ideal to use shallow field lifting magnets when lifting thinner steel materials from a stack, as it won’t lift the material underneath.

For example, 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 lifting a 20mm plate, it is still rated to lift 400kg.

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 thicknesses.

With no residual magnetism, the Shallow Field magnet makes it easy to eliminate the requirement to remove swarf and grit from the bottom of the magnet between lifts, reducing the risk of laceration-type hand injuries as well as damage to materials. Shallow Field magnets also carry more actuation, reducing risks of hand injuries for operators as less control on their part is needed.

Passive Shunting / Deep Field Lifting Magnets

Deep Field Magnets are designed for moving heavy steel sections, beams, and components. These magnets are generally durable and robust pieces of equipment, but will only lift their advertised capacity at the depth of their magnetic field. Therefore, calculation is required by the operator to ensure that the magnet is rated to lift the material at the given thickness.

The depth varies between sizes. For example a 500kg Deep Field Lifting 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 the 500kg magnet! This means that when you are using deep field magnets, there is more potential to mismatch the magnet to the load than there is with shallow field magnets.

A mismatch like using a 1-tonne deep field magnet with a 60mm field, to lift a 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, which can result in a wrist injury. Although Deep Field Magnets are suitable for picking up heavier materials, they are not suitable for materials that are less than 10mm thick due to this issue.

Overall, choosing the correct lifting magnet will depend on the application, the thickness, and the weight of the material handled. This diagram demonstrates the difference between the two types of lifting magnets:

Active & Passive Shunting Technology

 

Passive shunting Magnets achieve their full hold force between 30mm – 80mm thick while most Active Shunting Magnets are achieving their full hold force between 9mm and 20mm. This is the range of thicknesses that are most commonly handled.

This means is that at some thicknesses, an enormous Passive Shunting Magnet has less hold force than a small Active Shunting Magnet! This also shows that the bigger size lifting magnet isn’t necessarily always a better choice and would cost you more as well. This is why it’s important to learn about the difference between these two types of lifting magnets prior to the purchase.

Let’s look at how the two types of lifting magnets compare at the midrange thicknesses we commonly handle in Australia:

lifting magnet capabilities examples

 

At MSA Magnetics, we supply both types and are looking forward to offering advice on which type suits your requirements. Let’s have a look at the products we have to offer:

Magswitch MLAY Lifting Magnets & Magswitch CE Magnetic Lifters – Shallow Field Lifting Magnets

The Magswitch MLAY Lifting Magnets and the Magswitch CE Magnetic Lifters are both active shunting, or shallow field lifting magnets, designed for applications such as handling of grabs and chains when loading and unloading trucks and tables. Not only do these magnets substantially save time and allow for increase in production, they also greatly reduce WHS risks such as back injury caused by lifting heavy steel objects.

Magswitch MLAY Lifting Magnets include a lock on & off handle, which causes the magnet to completely turn on & off. They also have a superior hold on thin steel (7mm deep field) and the ability to lift large flat sheets, beams and pipes. The Magswitch MLAY is also a compact and lightweight design with easy actuation and great performance on air gaps such as rust and dirt. It has customisable pole shoes to fit almost any application, and the benefit of easy cleaning of debris. Explore the Magswitch MLAY Lifting Magnet range.

The Magswitch CE Magnetic Lifters are remote-controlled lifting magnets that are fail-safe and require no power once actuated. This lifting magnet range features automatic on/off actuation when operating in AUTO mode. It can also be operated utilising the on tool button or via wireless remote control (an optional extra).

The Magswitch CE Magnetic Lifters can be selectable between switching manually or automatic. A built-in security mechanism prevents demagnetisation when the load is suspended, therefore, unintentional release of the load is prevented. These lifting magnets can be used on flat and round materials, and the battery-operated lifter uses a magnetic pulse of less than one second to turn the magnet on or off. Battery power is not consumed during the lift, and they are independent of main power supply. The three applications include: Lifting, Auto ON & Auto OFF features. Explore the Magswitch CE Magnetic Lifters range.

MSA Pro-Lift Lifting Magnets – Deep Field Lifting Magnets

The MSA Pro-Lift Lifting Magnets are deep field (passive shunting) lifting magnets, designed for moving thick and heavy steel components. Pro-Lift Lifting Magnets allow operators to safely and easily lift steel material on and off trucks, cutting beds, guillotines, saws, etc, and substantially save time and allow for increase in production. They also greatly reduce WHS risks caused by lifting heavy steel objects.

The MSA Pro-Lift Lifting Magnets require no power for safe operation and feature two action controls with a spring-loaded catch, plus a lever button for compliance with AS4991-2004.

As mentioned above, it is crucial to consider the thickness of the material prior to lifting it, to ensure the magnet is capable of safely and effectively lift the load.

Residual Magnetism

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 will help explain why magnets with no residual magnetism are the safest option:

Extreme Residual Magnetism

This 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 magnet’s SWL (Safe Working Load) and the magnet could fail a pull test.

This magnet also has a high risk of causing 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.

residual magnetism

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. It will still require regular inspection for debris, however, you can expect it to collect much less than the first magnet.

pro-lift lifting magnet

No Residual Magnetism

This magnet uses Active Shunting Technology which allows it to be turned 100% of the way off. It is the safest type of lifting 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.

mlay lifting magnet

Contact our friendly team for expert guidance on selecting your next lifting magnet or for answers to any questions you may have on using lifting magnets.

MSA Magnetics – Your Source For Force

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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