Magnetic Separators: Knowing the Ideal Magnet Material & Circuit for Your Application
The field of magnetics (no pun intended) is vast. Many would have you believe that “Neo” magnets are the end-all-be-all when it comes to separating ferrous material from non-ferrous material. And while they are the most powerful permanent magnet, they have their shortcomings that all of their power cannot overcome.
Did you know that a magnetic field can be too strong? “Neo” magnets, which is slang for Neodymium Iron Boron magnets, are in a family of magnets that are referred to as “permanent magnets.” All of the magnets in the permanent magnet family, all provide something that their siblings cannot.
chart of magnet types, divided into rare earth, alnico, and ceramic, then by grade.
Magnet classification chart
Selecting the right magnetic separator for your application will depend on several factors. Temperature, flow rate, flow characteristics, and process issues should all be considered during the decision-making process. Let’s explore these in more detail:
High temperatures can alter a magnet’s effectiveness. They start to lose strength at their maximum operating temperatures.
All magnets also have what is called a curie temperature. The curie temperature is the temperature at which a magnet completely loses all of its gauss. Gauss is the measurement by which a magnet’s strength is measured. Once a permanent magnet gets heated past its curie temperature, the magnets structure is altered and the magnet will lose it all of its strength as well as its ability to be re-magnetized.
Heating a magnet past its maximum operating temperature, but below its curie temperature, will cause the magnet to lose its strength over time. So, it’s important to design a filter within the magnet’s maximum temperature, or contaminants in your particle stream will pass right through the magnetic separator.
Flow Rate and Characteristics
The material moving past the magnet needs to be metered so that the magnetic field can capture any contaminants. How the material flows makes a difference, too. If a material clumps, for example, it may plug the separator’s opening, requiring the position of the magnetic rods to be adjusted to create more space for the product to flow freely.
The type of separator needed will depend on several process considerations. You’ll need to determine the level of product purity required.
Is the material coming to the separator evenly or in surges? Magnetic Separators: Knowing the Ideal Magnet Material & Circuit
Can the system be stopped to clean the magnet or will you need a self-cleaning magnet?
If the magnetic separator is manually cleaned, how will the magnetic separator element be handled? Are there any ferrous materials nearby that could pose a safety hazard? Magnetic Separators: Knowing the Ideal Magnet Material & Circuit
Powder Type and Consistency
Perhaps one of the most important considerations is the type and consistency of your powder. Some of the categories that deserve consideration are:
Dry and free-flowing powders
Dry powders with bridging characteristics
Moist or lumpy powders (i.e. flour or cornstarch)