You Can Block a Magnetic Field

8th of 10 Magnetic Separation Myths

A common question asked by users of Magnets and Magnetic Separators is whether a Magnetic Field can be blocked in the same way that lead blocks radiation.  This can be an important issue when considering the location of a Magnetic Separator and whether it is near instrumentation, control panels, or is in an area freely accessible by employees.

The simple answer is that it is not possible to totally ‘block’ a magnetic field.  The essence of a magnet, as determined by nature, is that magnetic field lines must terminate on the opposite pole and, therefore, there is no way to stop them.

tube-cartridge-magnets-bunting-magnetics-4

However, often it is necessary to protect equipment from magnetic fields and this is achieved by re-routing the magnetic field.  This is otherwise known as ‘Magnetic Shielding’ and is achieved by casing the equipment requiring protection inside a structure that is made from or comprises of a material that has a very high magnetic permeability such as steel.  The magnetic field then flows along such that material, channeling the lines of magnetic field away from the components that require protecting, such as delicate electronics.

Not being able to completely block a Magnetic Field also causes difficulties for transporting Magnetic Separators and Magnetic Assemblies.  Many overseas customers ask if a particular Magnetic Separator can be transported by air.  Due to the inherent safety risk, there are strict regulations on how magnetically charged equipment and components can be transported due to concerns about interference with aircraft instrumentation.  Although such interference is extremely unlikely (due to most magnets having very shallow fields that do not even extend out of their packaging) there are guidelines that state:

  • Where possible the magnets are positioned with the north pole next to another’s south pole;
  • Thin sheets of steel are packed around the magnets in order to shunt the magnetic field and restrict it from penetrating outside of the box.  .

These guidelines are often possible to follow for small Magnets and Magnetic Separators, however transporting larger Magnetic Separators can very difficult and, if possible at all, exceptionally expensive.bunting-vulcanis-1139-2

This technique of channeling magnetic fields is actually used when designing Magnetic Separators such as the Overband Cross Belt Magnet, where magnetised blocks inside a stainless steel case have a thick steel backbar welded on one side to force the magnetic field to project away and in one direction.  This is a positive way of channeling the magnetic field to achieve the specific objective of picking up steel and magnetically susceptible materials.

For further information on Magnetic Fields and Magnetic Separators, please contact us on:

Phone: +44 (0) 1442 875081
Email: sales@buntingeurope.com
Via the website

Other Magnetic Myths reviewed in this series include:

  1. Should You Always Use the Strongest Magnet?
  2. All Rare Earth Magnets are not the Same;
  3. The Highest Gauss Magnet is not always the Best;
  4. Stainless Steel Isn’t Magnetic, or is it?;
  5. Do Magnets Lose Strength Over Time?
  6. Is a Magnetic Field Uniform Across the Surface of a Tube Magnet?
  7. We Guarantee 100% Metal Separation

3 thoughts on “You Can Block a Magnetic Field

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