Magnetic separators, both permanent and electronic, are an immensely popular method within the waste management and recycling industries to separate ferrous materials from other the processed materials. Magnets are used in conjunction with shredders, grinders and crushers for recycling such products as municipal solid waste, asphalt, compost, plastics, tires/rubber and concrete.
What to look for
When shopping for magnets, the first question to ask is, “Do I need a permanent or electro magnet”? While there are many differences, the primary benefits of permanent magnets are strength, ease of maintenance, durability, longevity, plus lower operating and acquisition costs. Permanent magnets are equivalent to or better than electros in performance and operational costs for nearly all applications. The only reason to go with an electro magnet is generally when needing to separate very small ferrous objects with little surface area (e. g., a one-inch ball bearing) or when the burden is extreme (in the 16-inch or higher range) or when the magnet is to be suspended at a working gap of 18 or more inches, or when the separated ferrous objects are in excess of 60 lbs, with a deep burden. In these extreme applications, an electro magnet is preferable.
Regarding maintenance, permanent magnets require no maintenance and last a lifetime. (A permanent magnet will lose 0.01 per cent of its effective strength every 100 years.) Electros must be checked at regular intervals to be sure coils are immersed in oil, otherwise the user can expect costly repair bills, often in excess of 30 to 40 per cent of the original magnet cost. Electro magnets carry warranties on their coils that range from one to 10 years, but never a lifetime. Other than puncturing or dropping a permanent magnet, there is virtually no way to damage the units. With electros, the same puncturing or dropping has a much more serious consequence, due to potential leaking and coil damage.
Operational costs for a permanent magnet are zero. Once mounted and suspended, permanent magnets simply do their job. Electros, naturally, consume electricity and cost more to mount in their supporting structure due to weight. Electro magnets tend to be 40 to 150 per cent more expensive than permanent ones.
Finally, make sure your magnet is properly sized and not just what a supplier gives you who can only offer one of two sizes.
For more information on permanent magnets, visit the website of Shields Company Magnetics Inc. www.shieldscompany.com