Do Magnets Get Weaker Over Time?

“When will my Magnetic Separator start losing its magnetic strength?” It is a very common question, and for good reason.  Under normal operating conditions, a magnetic separator will not lose any magnetic strength.  However, there are circumstances in which other factors can come into play, and these may have a negative impact on the strength of your magnet.  A few of these circumstances are:

1. The use of bonded Rare Earth Magnets. These are lower in cost to manufacture and therefore cheaper to purchase.  They are supplied by many companies, stating that the magnets are ‘Rare Earth’.  However, as the magnet is only bonded (i.e. bonded together using a resin) it is not as strong or stable as being sintered.  Ceramic Rare Earth Magnets, that have been produced using heat, are more stable and are what Bunting and other reputable magnetic separator suppliers use in their magnetic separators.  Bonded Magnets, however, do have their uses and remain an ideal for other applications.
2. Physical damage. If a Magnetic Separator is dropped or hit, then this can result in the magnets inside breaking and this will affect the magnetic power.  Such damage often occurs when a Magnetic Separator is being cleaned.  Unknowingly, the Magnetic Separator is returned to the process line with the operator totally unaware that the magnetic separation capabilities have been seriously compromised.  Regular checks on the magnetic strength of the Magnetic Separators is recommended as part of an annual review and audit.
3. Exposure to heat. When Rare Earth Magnets are exposed to heat over 80°C, there is a reduction in the magnetic strength.  When the temperature reduces, the magnetic field can recover.  However, if the temperature is very high then the magnetic strength will never recover back to the original state.  Typically Magnetic Separators are exposed to high temperatures if a process line is being cleaned using steam.  There are special Rare Earth Magnetic materials that are specially produced for high temperature applications, with Samarium-Cobalt being used in extreme circumstances.

Understanding the ability of a Magnetic Separator to retain its magnetic strength will keep you on the right track during the equipment purchasing and maintenance processes. 

For more information please contact us at:

Phone: 1-800-835-2526

Email: bmc@buntingmagnetics.com