Over the last few years magnetic lifters have grown in popularity, especially in the recycling, metalworking, mining, construction and demolition industries. Today, magnetic lifters prove the most convenient tool for moving substantial, ferrous loads. This is mainly due to the strength they offer, meaning no additional manpower is required. With a simple flip of a switch, the smallest of boxes can easily move tons of weight.
How do they work?
Most magnetic lifters consist of a slightly different design; however, the general concept remains the same. Each magnetic lifter contains a metal cylinder which houses neodymium magnets. These cylinders are also wrapped in an electric coil. When in operation, the coil is charged with a burst of electricity which produces an attractive field.
The magnetic field generated by the coil realigns the atoms in the metal cylinder. However, before operation, the atoms in the cylinder are randomly arranged. Once produced, the electrical current creates a uniformly aligned domain in the metal, which in turn amplifies the attractive field. It is the tightness of the coil and the material used in the metal cylinder, that are primarily responsible for the device’s working power. Therefore, by scaling both of these up, industrial lighting magnets are able to produce their impressive grabbing ability.
Basically, as more electrical power is added to the device, its attractive force increases. However, once the atoms in the metal are completely aligned, increasing the electrical current won’t increase the attractive force. Therefore, most magnetic lifters are designed so that it is impossible to power the device beyond saturation.
When turned off these magnets face back into the lifter, while the cylinder and lifter absorb much of the magnetic field. Moreover, when the lifter is turned on, the cylinder is turned upside down using a handle. This exposes the magnets to the area underneath the lifter, allowing them to attract heavy objects.
Powerful magnetic lifters can carry all sorts of ferromagnetic materials, including:
- Heavy metal sheets
In some cases, magnetic lifters even have a small groove cut underneath to help grab onto metal pipes. Once the load is in place, the lifter can be turned off which ends the connection between the magnetic lifter and the load.
Factors influencing lifting capacity
There are a few factors that influence the magnets lifting capacity, including:
- Surface condition: Magnetic force can pass easily through iron, but not air. Therefore, anything that creates an air gap between the magnet and the lifted object will have a negative impact on the magnets lifting capacity. This includes dirt, moisture, paper, paint or rust.
- Material being lifted: The harder a type of steel is, the poorer the lifting capacity.
- Thickness of the load: It is only when the load is significantly thick, that the magnets full force will then be utilised.
- Temperature: The higher the temperature the lower lifting capacity.
When working with magnetic lifters, the safety practices are the same as those when working with regular magnets. However, since working with loads in the air, everyone in the vicinity should wear hard hats. It goes without saying that those with pacemakers or defibrillators must keep away, while others must keep their hands away from the lifter when it’s on.
Other general safety procedures include:
- Ensure all instructions have been read and understood before operating the magnetic lifter
- Know the magnet capacity for the material thickness being lifted
- Remove magnet from service if capacity or safety-first tags are missing
- Exercise caution when handling iron or steel materials near magnets
- Workers should never stand below a lifting magnet
As mentioned, magnetic lifters use powerful neodymium magnets. However, neodymium magnets are vulnerable to damage from heat, thus magnetic lifters must be situated in temperature-controlled environment. As a rule of thumb, the number to keep in mind is 80°C. At this temperature, neodymium magnets will begin to decline in strength, meaning if exposed to this temperature long enough they’ll permanently lose their magnetism.
Additionally, it is important that magnetic lifters and the materials they lift are kept clear of any debris. When in use, the significant amount of force pulls the lifter and the ferromagnetic material together. Therefore, anything in between may potentially be crushed, cut into the lifter, or burst and kick out into the open, creating a safety hazard.
If taking note of the stats on each lifter, there are three important numbers to look out for:
- The rated capacity: This is the maximum working weight for non-cylindrical objects, such as sheets of metal.
- The cylindrical capacity: This is the maximum working weight for cylindrical objects, like pipes.
- The max tear-off strength: This refers to the total weight required to pull an attached item away from the lifter.
For more information on magnetic lifters contact:
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