When a manufacturer claims that they have the “strongest magnet tube on the market” what exactly are they saying? It simply boils down to their magnet having the highest holding force or highest Gauss level at the surface of the magnet. This may not always be the right solution for your application- let’s explore why….
What Does it Mean to Have the “Strongest Magnet”?
At it’s core, a magnet’s job is to capture and retain unwanted metals from your product stream. What differentiates one magnetic tube from another? The answer is variations inside assembly such as raw material strength, protective coatings, wall thickness, size of the magnet material and size of pole pieces. These internal variations effect the circuit characteristics outside of the magnet, in what we refer to as the working area, which is where the product is moving through the magnetic field.
Manufacturers have kept the conversation about magnetic tubes performance on the surface, or in the working area, which is where we conduct our testing with either pull or gauss testing. Let’s take a deeper dive behind the stainless to understand how these variations can effect overall magnet performance.
What You Need to Know About MGOe
Neodymium rare earth magnets are made of a mixture containing Neodymium, Iron, Boron, Cobalt and varying levels of Dysprosium and Praseodymium. The exact amounts of these ingredients determines the Maximum Energy Product, or MGOe. 52 MGOe is currently the highest energy product readily available for commercial use.
The most important thing to understand is that the MGOe of any grade magnet material is finite and only has that maximum energy available. Because creating 52 MGOe material is an exact scientific recipe, it doesn’t matter which magnet supplier you purchase from, their 52 MGOe will have the same maximum energy as any other manufacturers 52 MGOe material.
Just because a manufacturer uses 52 MGOe material does not mean that they have the most powerful magnetic circuit. Other factors covered below can also influence the overall performance of the magnetic circuit. Let’s explore these other factors…
Reducing Tube Wall Thickness
Besides using stronger magnet material, another way to increase performance on the surface of the magnet is by reducing the air gap. The air gap is the amount of space, in this case stainless steel, between the magnetic pole pieces inside the magnet and the working area on the surface of the magnet. The closer the pole piece is to the working area of the magnet, the higher the measure of gauss or pull value will be on the surface of the magnet.
Reducing this air gap to achieve higher performance values by manufacturers can be accomplished by using thinner walled tubing. This reduces the thickness of the magnets protective cover. As you decrease the thickness of the protective cover, you also decrease the protection that layer provides.
Often you will see dents and wear on magnets from manufacturers who use thinner tubes to lay claim to “the strongest magnet on the market.” Sometimes you may observe that your Magnet Audit reports reflect your magnet pull is actually getting stronger. Do not be fooled into thinking that this is a good thing; this is a sure sign that abrasion from your product flow is wearing through the thin wall of the magnet tube and will soon need to be replaced.
Uncoated Magnet Slugs
If you have ever held a rare earth magnet in your hand (be careful!), it likely looked very shiny, as if it was chrome plated. This is because most magnet material manufacturers coat the raw magnet material in a nickel coating to protect the magnet from oxidation.
While this coating protects the magnet, when installed into an assembly such as a magnetic tube, it also increases the air gap. Another way manufacturers reduce the air gap is by using uncoated Neodymium magnet material. Neodymium is one of the more reactive rare earth elements and is very sensitive to oxidation. A one centimeter sample of Neodymium will completely oxidize within a year if left exposed in ordinary air.
The oxidization process is very similar to rusting, the structure of the magnet changes permanently resulting in a progressive loss of magnetic performance and the magnet breaks down into a powder state. Using uncoated magnet slugs can be especially detrimental in applications where wet product are being filtered. Moisture penetrates the tube and an uncoated magnet slug will begin to swell as oxidization is accelerated. Eventually this leads to loss of magnetism and a potential to blow out the tube.
The MPI Difference
At MPI we are passionate about providing you the correct solution suited to your application. We offer several models of magnetic tubes because there are many factors to consider when installing a magnet into a production line. Many times, a one-size-fits-all or “strongest magnetic tube” solution is not the right solution for everyone. For this reason, MPI offers several solutions so customers can choose the right balance of performance, cost and durability for your application.
An MPI trained magnet professional will help you select the right magnet for your application. It is critical to consult a magnet professional before installing a thin-wall magnet into any application.
To bridge the gap between performance and durability MPI has developed the new Hi-G Magnetic Tube. MPI’s Hi-G Tube provides comparable pull values to any competitive “strongest on the market” non thin walled tubes, without compromising the durability and longevity of your magnetic separator. We want to offer you the RIGHT magnet; for performance without compromise contact MPI today.