Five Magnetic Separator Myths, Part Four: Do Magnets Lose Strength Over Time?

One of our most frequently received questions is, “When will a magnet begin to lose its magnetic strength?” There’s good news: under perfect operating conditions, a magnetic separator will only lose a non-noticeable amount. However, outside factors can influence a magnetic separator’s strength over time and result in loss of strength. There are three main factors that typically lead to loss of strength.

The first factor that can result in a magnetic separator losing strength over time is the type of magnets used. Bunting and other reputable magnetic separator suppliers use ceramic rare earth magnets, produced using heat, because they are far more stable than bonded magnets. Bonded magnets are ideal for many other applications, but are not ideal for use in magnetic separators. Certain companies choose to use bonded rare earth magnets in magnetic separators because bonded magnets are cheaper to manufacture and, as a result, cheaper to purchase. However, because this type of magnet is only bonded together using a resin, it is not as stable or strong long term when compared to sintered ceramic rare earth magnets.

The second factor that can result in a magnetic separator losing strength over time is physical damage. If a magnetic separator is hit or dropped, the magnets inside can break, leading to the magnetic power being affected. Often, this damage occurs when a magnetic separator is being cleaned or undergoing other maintenance. Then, the operator returns the magnetic separator to the process line, totally unaware that its magnetic separation capabilities have been severely compromised. To avoid this problem, it is recommended that magnetic separators undergo an annual review and audit to assess their strength and identify any problems.

Physical abuse can occur from product as well. If you have a product that is corrosive, coarse, abrasive, or even granular it will slowly deal damage to your magnets. This may not be noticeable from month to month, but over the course of several years it is definitely something you will begin to notice.

The third factor that can result in a magnetic separator losing strength over time is exposure to heat. Typically, rare earth magnets are only rated to perform at temperatures up to 80°C. When a magnet is exposed to higher temperatures than its maximum operating temperature, it will experience a reduction in magnetic strength. If the temperature does not exceed a certain point, the magnetic field can recover and return to its original strength. However, if the temperature reaches too high of a point, the magnetic strength will never return to its original state. In extreme situations, the magnet can be completely demagnetized, although this is rare. The most common situation that leads to magnetic separators being exposed to high heat is during cleaning processes that utilize extremely hot water or steam cleaning. To avoid this problem, customers must select magnets specifically rated for high temperature applications, such as high temperature neodymium magnets.

If a magnetic separator is properly maintained, it should not lose magnetic strength over time.

For assistance in selecting the best magnetic separator for your application, contact us today. We can answer any questions you may have and provide personalized guidance in regards to your unique process.