Powerful, durable, versatile. Permanent magnet lifting equipment are widely used and are a staple in a variety of industries. If you usually rely on the use of slings and chains-there is an easier more efficient way to get the job done! As long as the material is ferromagnetic, there are few limitations to the types of loads that can be lifted.
From flat sheets to long bars, I'm going to discuss the types of permanent magnets and electropermanent magnets in this guide and how they provide a cost-effective solution to all your lifting needs.
How They Work
We all know that opposite poles attract and same poles repel, within a permanent magnet there are 2 sets of magnets which are rotated to control the magnetic field. When the lifter is turned on, the field is directed into the load. When turned off, the field is directed internally away from the load meaning the magnetism has stopped. This manipulation of poles is simply hand controlled by the lever.
The beauty of permanent magnetism is that there is no danger of dropping the material if there is a power failure and can be used when electricity is not readily available. A permanent lifting magnet is made of ferromagnetic material that keeps a small part of its magnetism after it is turned off.
The second type of lifting magnet is electropermanent, a hybrid which has the advantage of the user being able to operate it from a safe distance in the case of a hazardous work area. Within it there is magnetic material enclosed by a coil instead of moving magnets. The polarity is controlled when a pulse of electricity is passed through the coil, turning the magnetism on or off- the degree of magnetism can also be controlled.
With electro-permanent magnets, electricity is used only for a few seconds to turn on and off its magnetic power. While in use, it keeps its lifting force even if there is a power failure thus consuming less energy than an electro lifting magnet while being safer.
The front runners in lifting magnets are created by Yale and Tecnomagnete, here are 3 models for differing uses.
The Yale TPM permanent lifting magnets are available from a capacity of 100kg right up to 1000 kg. When lifting both flat and round objects, it is ideal for easy, quick and economical transport of heavy objects.
They are typically used in workshops and warehouses for loading and unloading of machines as well as construction of jigs and fixtures.
They do not need electricity and will leave only minor residual magnetism after use.
Switching the magnet ON and OFF is made easy by turning the locking lever.
When activated, the hand lever will be safely locked to prevent unintended demagnetising.
Tecnomagnete Easylift Crane Magnet
Ideal for use in carpentry, Easylift is a light permanent electromagnet for the handling of thin sheets and can handle sheets of just 1.5mm thickness. Using a traditional method to lift such a thin sheet could lead to warping making the operation unstable and hazardous.
- It automatically clamps a single sheet from the stack, without the need for spacers
1 operator is able to quickly complete pickup, handling and release phases
They are permanent-electro and therefore insensitive to power outages; total safety for personnel and equipment
Maintenance free; no need for backup batteries. No moving parts, no wear
It does not leave any residual magnetism on the load.
Perfect for handling loads of any dimension and shape, the BatGrip magnet combines the power and convenience of a permanent-electro lifter with the practicality and flexibility of use of a manual lifter.
It comes with a remote control enabling operation at a safe distance of up to 30 meters.
Very little energy consumption with power for more than 500 operations between charges.
The load can be stacked, without the need for spacers, causing no damage.
Easy handling of the module and structure protection is allowed by the tubular bar that surrounds the module.
Dautanac system to prevent demagnetization during handling.
BatGrip can be easily hooked to fixed or mobile lifting plants, thereby ensuring the best ergonomics in the workplace and total safety for the operators and equipment.
Advantages & disadvantages
As opposed to electromagnets, permanent magnets have some advantages:
It doesn’t require electrical supply during the handling of the load.
No battery backup required.
Electropermanent magnets only use power for activation and deactivation, which last only a few seconds.
They are high energy magnets with a constant and high concentrated force on the load at indefinite period of time.
No moving parts – No wearing – No heat generation – No energy consumption.
They are durable and require very little maintenance.
They can be easily operated by hand
They cost the least out of all other types of lifting magnets.
However there are some disadvantages:
As the air gap between the permanent magnet and the load increases, the lifting capacity decreases.
The lifting capacity will also decrease if the thickness of the load is below the recommended thickness.
The larger the capacity of the lifting magnet, the harder it is to turn the handle to turn it on.
The permanent lifting magnet is hand-operated only and cannot be used from a distance, while the electropermanent magnet can be remotely operated.
Generally, lifting magnets are intended for lifting vertically as using them at an angle without the use of a special beam may result in slippage. The performance of permanent lifting magnets depends on a number of factors, to ensure optimal use, check the material being lifted for the following:
The composition of the material is ferromagnetic ie. steel, iron
No trace of dust, scraps, paint, oil, rust, on the surface
If it is long, more than 1 magnet may be needed
It is not flexible
It is above the recommended minimum thickness
The magnet has full contact with the surface ie. no gaps/holes
Generally, permanent lifting magnets create a high magnetic force which allows components to be clamped if there is an air gap. However, the air gap will reduce the magnetic performance as they provide a barrier between the contact surface.
Dust, dirt, oil, paint, and heavy mill scale are all causes of an air gap. Poorly machined surfaces also constitute an air gap.
If sheets thinner than the recommended minimum thickness are being lifted, the clamping force will be reduced significantly.
To get the most out of the lifting capacity, the magnet must have full contact with the load being lifted, if the contact surface has holes in or is uneven then the performance will be significantly affected. To establish correct lifting, a safe trial lift should be carried out if you have any possible issues like these.
Certain materials have different abilities to hold magnetism. For materials other than mild steel a reduction factor should be applied in order to calculate the effective clamping force.
Ferrous alloy steels 0.8
High carbon steels 0.7
Cast iron 0.55
Examples of reduced WLL:
Mild steel 500g
Cast iron 500kg x 0.55 = 275kgs
Harder types of steel reduce the lifting capacity. This table shows the lifting power of various materials:
For safety, permanent lifting magnets should have a tear off force of at least three times the working load limit. Under controlled conditions in a safe environment, tests can be carried out to ensure a load is being lifted correctly.
If you have concerns about the impact an air gap will make on the operation, a good way to test this is to place thin card between the lifting magnet and the load. If the load can be easily lifted then you can confidently carry out the task.
If you need to lift something flexible, more than one magnet suspended from a lifting beam may be needed to prevent it from peeling away from the magnet.
The main problem people have with magnets is when they are ill-informed, using a bigger magnet than needed can be riskier than expected. Luckily, with new permanent lifting magnets there are often safety mechanisms in place to carefully release or lock when operating.
It's easy to see how permanent lifting magnets can positively improve productivity and safety while decreasing the risk of damage to stock. They make work easier and more efficient by removing the need for blocking, slinging and placing mechanical grabs.So if you want to lift metal materials with no damage and little effort, there is a variety of options available in our store. Check out all our Lifting Equipment products here.