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Electro Drum Magnets

The design of Bunting’s range of Electro Drums is the result of several decades of working closely with users and is widely recognised as world-leading.  Electro Drum Magnets are heavy-duty magnetic separators used in automobile frag plants, steel slag operations, household refuse facilities, and incineration plants.  They are designed to separate and recover larger-sized ferrous metals.  There are two models of Electro Drum Magnet to suit specific separation requirements:

  • FED (Frag Electro Drum): for maximum purity of recovered ferrous metals;
  • SED (Slag Electro Drum): for maximum recovery of ferrous metals;

 

 

Description

The Electro Drum Magnet has stationary electromagnetic coils positioned inside a non-magnetic, commonly manganese steel shell, fitted with welded stainless-steel wiper bars.  The shell rotates around the stationary electromagnetic coil at a speed determined by the volume of processed material.

The electromagnetic coil, computer designed for maximum energy and induction efficiency, consists of a mild steel core wound with either Nomex covered aluminium wire (insulation is above class ‘H’) or anodised aluminium foil.  The magnet system remains stationary within the rotating covers.  To suit specific separation objectives, Bunting has two different designs of Electro Drum Magnet:

  • Frag Electro Drum (FED) – Uses an alternate pole coil design to continuously remove ferrous metals from a product stream in applications such as municipal refuse and automobile fragmentiser plants, whilst maximising ferrous purity;
  • Slag Electro Drum (SED): Uses a radial pole coil design to maximise the separation of ferrous metals by holding the metal firmly to the drum shell through the entire 180-degree cycle;

Operation

Electro Drum Magnets are designed to operate in difficult and heavy-duty applications where the ferrous metal is large and angular.  The size and weight of the ferrous metal means that a very strong and deep magnetic field is required, which is generated with electromagnetic coils.

In operation, material is fed onto the drum at one of three different points depending on process configuration.  The three different feeding arrangements are as follows;

  • The material is fed onto the top of the Electro Drum. Magnetic material is attracted and held to the drum shell before being discharged beneath the drum;
  • The material is fed onto to the centre of the Electro Drum. Attracted magnetic material is discharged opposite to the in feed;
  • The material is fed beneath the Electro Drum. Magnetic material is captured and held to the drum shell and then carried up and discharged over the top of the Scrap Drum;

In all three configurations, non-magnetic materials will free-fall forward following their normal trajectory.

Models

There are two models of Electro Drum Magnet to suit specific applications:

Model FED (Frag Electro Drum)

The FED design features a single main coil stretching the full width of the drum producing an alternating polarity along with a single auxiliary coil.  This design is typically used where magnetic materials may be entrapped or buried beneath non-metallic materials. The FED Frag Drums are designed to allow extracted magnetic materials to roll over the face of the drum to release any non-metallic materials that may be caught between the ferrous material and the magnet.

drum magnets ‌

The asymmetric bipolar coils consist of a main coil which concentrates maximum flux at the point of extraction, whilst a secondary coil ensures that the ferrous material is carried around the drum to the point of discharge.

The magnetic field alternates to ‘flip’ the magnetic material as it travels around the drum. This removes stray non-magnetic particles from the product stream producing a cleaner magnetic product.

The coils are ducted between the core and the coil, and between the coils themselves, maximising the heat dissipation of the coil, and giving a higher efficiency magnet.  This cooling system also minimises the gradient from any surface, therefore significantly reducing hot spot temperatures.

Key design features:

  • The axial pole design gives continuous high field strength at the separation zone. The effective magnet width is maximised thus ensuring even cover wear and minimum burden depth of material;
  • The high-intensity primary coil concentrates maximum flux at the point of extraction whilst the lower intensity secondary coil ensures that ferrous material is transported to the point of discharge;
  • Ducted coils give an improved cooling, this results in a low winding temperature allowing higher intensity and a longer coil life;
  • Wear covers 8mm thick minimum in manganese steel incorporate bolted joints for ease of cover replacement;

 

Model SED (Slag Electro Drum)

The SED Slag Drum Magnet features two or more symmetrical coils (depending upon width) producing a continual radial pole.

The magnet system, specially designed by computer to maximise efficiency, is made up of a mild steel core wound with anodised aluminium foil. The magnet system remains stationary within the rotating covers.  The 2, 3 or 4 coil, continuous pole design, consists of coils which concentrate maximum flux at the point of extraction, while an extension pole ensures that magnetic material is carried around the drum to the point of discharge.  The poles are arranged radially over the width of the drum. This ensures maximum entrapment of metals giving the highest level of separation.

Electro Drum Models & Sizes

Additional features:

  • Main shell cover: Fabricated from 8mm thick wear resistant manganese steel, which is fully welded to the end flanges, to form a robust construction
  • Wear cover: Constructed from 8mm thick wear resistant manganese steel.  Wiper bars are fitted across the whole width of the shell and at regular intervals around the circumference of the Drum shell.  The wear cover has bolted joints for ease of replacement;
  • End flanges: Low carbon steel end flanges are fitted with an inspection cover in one end, to allow visual inspection of the coil and windings;
  • Bearings: Cooper split flange bearings are used, for ease of maintenance;
  • Fixed bearings: Pedestal bearings with locking rings are used to clamp the magnet system in the working position;
  • Adjustment: The position of the magnet system within the Drum is adjustable using an adjuster arm, fitted with a cone locking ring and turnbuckle. The position of the magnet is adjustable.  The magnet position, and thus the discharge of ferrous metals, is set in accordance with the customer’s discharge chutes, ensuring maximum separation efficiency;
  • Drive: A BS pitched Simplex platewheel is bolted to a robust drive ring;
  • Power supply: 380/415v, 3ph, 50Hz
  • Finish: All steel will have one coat primer and two coats of RAL 5019 high performance alkyd enamel.

Transformer Rectifier

The Transformer Rectifier provides power to the magnet at the correct Amps, depending on magnet design, ambient temperature and input voltage.

Additional features

  • Tank: Fully welded steel enclosure to IP 65, with bolted lid for access to oil and components.  Oil level gauge fitted to front of tank and drain plug provided for oil change.
  • Terminals: Incoming AC and outgoing DC terminals are located in the terminal chamber on the front of the tank. Taps are located inside chamber to change outgoing DC voltage by 5%
  • Transformer: Double wound transformer to BS EN 60076.
  • Rectifier: Silicon diode, full wave bridge connected rectifier, stack mounted on an aluminium heat sink to BS 4417 ABCD
  • Protection: Diode protection with fast acting semi-conductor fuses. Surge suppression fitted to protect diodes against surges from magnet coil upon switch off.
  • Finish: All steel will have one coat primer and two coats of RAL 5019 high performance alkyd enamel

Optional extras

  • Starter box with start/stop button, current sensing relay to detect magnet low power, overloads and lockable isolator. Terminals are provided for remote access
  • 150mm high spillage rings are fitted to the end flanges to prevent side spillage. These rings are fabricated in sections to allow easy replacement if damaged
  • Drum can be mounted onto base frame and supplied complete with geared motor, chain drive and guard.
  • A split platewheel can be provided for easy replacement, reducing downtime.
  • The Platewheel may be ANSI if required

Applications

Electro Drum Magnets are used widely in the recycling industry, especially in difficult and arduous environments including:

  • Automobile and vehicle fragmentation plants;
  • Household Waste Incineration plants;
  • Household Refuse Recycling Operations;
  • Steelworks recovering steel from slag;

Note:  All stated capacities are for indication purposes only.  Specific capacities are subject to confirmation once an application has been reviewed or after laboratory tests.

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