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Consequences of Residual Magnetism in Lifting Magnets

Posted on Aug 10, 2017

lifting magnet with load underneath

Armstrong Magnetics’ permanent lifting magnets are designed and manufactured with minimum to no residual magnetism in lifting magnets at their OFF position. It is an important property that buyers need to consider when selecting lifting magnets. In this blog, we shall discuss what cause residual magnetism and what are the consequences.

Typically, a soft steel with low carbon has less residue and a tool steel with high carbon ends up with high residue. Every brand lifting magnet has its own unique internal engineering design with different positions, sizes, and amounts of Neodymium magnets.

When residual magnetism exists at the OFF positions, surrounding debris/chips/particles can easily attract to the lifting magnet pole faces. With hard particles attached to the bottom, the device can be easily damaged with small scratches and dents resulting air gaps. As mentioned in many of our other blog posts, air gap is detrimental to a magnetic lifter’s maximum rated lifting capacity. With small dents on the magnet faces, the air gap will build up and become permanent until the pole face is processed through machine grind. To avoid early wear and reduced life due to residual magnetism, operators must examine the lifter before each usage, wipe clean both the magnet pole faces and the contacting area of the loads, and store the product in a clean isolated area.

One frequent complaint we hear about other brands is that the magnetic flux gets locked at the ON position and cannot be returned to the other direction. The reason for this issue is likely being low cost of construction with air spacing in the main body structure, allowing exterior particles to enter and damage the inside bearing at faster rate than normal wear rate. One may attempt to disassemble, wipe the unit clean, demagnetize any ferromagnetic parts and then reassemble. But this is only temporary solution and can be quite time consuming.

Armstrong’s NL-B series lifting magnets are designed to have a completely enclosed main body and a clean break of magnetic flux at the OFF position. We ensure the highest industry safety standard for our industrial lifting magnets while making sure they are easy to use.