Grate Magnets

How Do Grate Magnets Work?

The MPI grate magnet is one of the most versatile magnetic separators for installation options. They can be compact and integrated into existing equipment such as hoppers, chutes, bag dump stations or bins. Regardless of the installation location for magnetic grate separators, the principle on how they work remain the same.

The product stream flows through typically a single row of 1” diameter magnetic tubes, located on 2” centers, allowing 1” of space between each tube. The tubes are held in place with a stainless steel support frame of varying designs as required by the application. As tramp metal contaminants are captured, they move to the underside of the magnetic tubes, eliminating tramp metal “wash-off.” Captured ferrous metal is held on the magnetic tube until it is removed from the product flow and manually cleaned off by hand or with an MPI hand cleaning tool.

Options such as a frame at the end of the tubes make the magnetic grids easier to clean, while options such as diverters, make it a more efficient magnetic separator, but more difficult to clean.

• Magnet Type:
  • Grate magnet (GM Series)
• Shape: Standard shapes for grate magnets are listed below. Custom shapes are available to fit any application.
  • Round
  • Square
  • Rectangle
• Sizes: Sizes range from 4″ to 48″+ depending on configuration.
• Material Construction:
  • 304 Stainless Steel (standard)
  • 316 Stainless Steel
• Frame Design: The frame that holds the magnetic tubes together is manufactured from stainless steel and welded to the tubes. Several different frame options are available for cleanability, sanitary and economical considerations.
  • Welded inside frame 2″ tall x 0.105″ thick
  • Welded end of tubes 2″ tall x 0.105″ thick (not available for round grate magnets)
  • Bolt on end of tubes 2″ tall x 0.187″ thick (not available for round grate magnets)
  • Food grade sanitary frame at end of tubes 2″ tall x 0.187″ thick
• Diverters:  Diverters can help increase the tramp metal retention efficiency of the grate magnet but can obstruct product flow and make the magnetic separator more difficult to clean. MPI offers several different options for different material characteristics.
  • Not included (standard)
  • D2 – 90° bend to assure maximum product contact onto magnetic tube. Designed for fine, free-flowing products.
  • D3 – 60° bend to help product contact magnetic tube. Designed for medium size product streams.
  • D4 – 0.375″ diameter round bar helps product contact magnetic tube while providing minimal product flow deflection. Designed for course, granular product streams.

• Magnetic Tubes: Different performance models of magnetic tubes are available to match the applications tramp metal requirements. Reference MPI Magnetic Tubes for specific performance information on each option.
  • Ceramic
  • REN Rare Earth Neodymium
  • Hi-G high-performance Rare Earth Neodymium
  • TW Thin Wall high-performance Rare Earth Neodymium
• Magnetic Material Temperature: Magnet material has a maximum operating temperature depending on the grade. MPI supplies the strongest grade available for the stated maximum temperature. Magnet material should be specified to be safely over the applications maximum operating temperature. Reference MPI Magnetic Tubes for specific performance information on each option.
  • 400°F (204°C) @ 3.5 MGOe (ceramic)
  • 176°F (80°C) @ 52-55 MGOe (rare earth)
  • 248°F (120°C) @ 48 MGOe (rare earth)
  • 356°F (180°C) @ 38 MGOe (rare earth)
  • 662°F (350°C) @ 30 MGOe (rare earth)
• Tube Spacing:  Magnetic grates are designed to perform at highest performance when manufactured with 2″ horizontal centers between the tubes. This spacing can be expanded if required for product flowability at the compromise of tramp metal retention efficiency.
  • 2” horizontal spacing (standard)
  • 3” (approx.) horizontal for increased flowability
• Tube Coatings: Standard stainless steel tubes are excellent for most applications. Synergistic coating is available for applications where abrasive or adhesive products are being processed to increase abrasion resistance and cleanability.
  • Stainless steel with no coating (standard)
  • Synergistic Coating [reference Synergistic Coating Datasheet requires bolt-on or outside frame design]
• USDA/3-A Magnet Certification (USDA AMS NSF / ANSI / 3-A14159-1 2002):  Certifies grate magnet to USDA standards for cleanability, corrosion resistance and durability.
  • Not included (standard) 
  • Included
• Weight:  MPI recommends all grate magnets that are handled by personnel weigh under 50 lbs. each. Larger grates can be split into multiple smaller sizes to accommodate recommended handling weight. The weight of the grate magnet specific for your size will be shown on the quote.