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MAGNETIC DRUMS

A MAGNETIC DRUM

Just like overband separators, permanent magnetic – or electromagnetic – drums are self-cleaning iron removers installed outside a conveyor system. 

The use of magnetic drums is recommended when customers need an accurate extraction of ferrous intrusions from process material in order to preserve other machineries (eg. shredders/blades) within the waste plant. 

The drum structure and type of magnets varies according to the dimensions of the ferrous fractions to be recovered. 

A permanent magnet drum does not require an electric panel to function. Malaman C.T.C. supplies its permanent magnetic drums ready for installation and operation. On the contrary, an electromagnetic drum requires an electrical panel dimensioned according to the magnet’s winding circuit. 

Iron removers (eg. overbelt separators, manual overhead suspension magnets, magnetic drums, etc.) are used in the first stage of refining the process material such as glass, wood, plastic, post-combustion slag, USW, OFMSW, etc.  

COME SONO FATTI

A magnetic drum is made up of:

  • 1 static shaft with brakes;
  • 1 rotating half-shaft that transmits motion to the cylindrical shell;
  • 2 side flanges;
  • Adjustable internal magnetic circuit (either permanent or electric) fixed onto the static shaft;
  • 1 non-magnetic cylindrical shell with welded transversal cleats. 

 

tamburi magnetici
tamburi magnetici

MAGNETIC DRUMS: FURTHER DETAILS 

For magnetic drums up to Ø 600mm, the gearmotor is directly mounted onto the rotating half-shaft.

For larger magnetic drums, instead, a transmission chain is used to transfer motion from the motor shaft to the rotating half-shaft. 

 

HOW DOES A MAGNETIC DRUM WORK

In a magnetic drum, the motor shaft transfer motions to the rotating half-shaft which is fixed to one of the two flanges constituting a single body with the other flange and rotating cylindrical shell. 

The internal magnetic circuit is oriented so as to hold the ferrous material onto the cylindrical shell. This shell is equipped with transversal cleats welded onto its surface which help carrying the Fe intrusions away from the magnetic field and then release them into bins for collections. 

Malaman C.T.C. suggests two different installation options:

  • Free fall (or traversing): the bulk of the waste material onto the conveyor belt falls directly onto the rotating shell of the drum. Here the magnetic intrusions are attracted to the surface of the drum, then transported backwards and discharged. The inert material, instead, follows the laws of gravity and falls down. 
  • Extracting: the drum is installed diagonally above the conveyor belt, near the point of discharge. The separator attracts the ferromagnetic intrusions and then releases them on the opposite side. 

MAGNETIC DRUMS: TYPES, MODELS AND DIMENSIONS

The magnetic field of a magnetic drum can be:

  1. Permanent (MDR) – generated by Ferrite or Neodymium magnets – or electromagnetic (EMDR);
  2. Generated by cores around which the conductors (mainly copper and aluminum) are wound.

If necessary, the permanent and electromagnetic nature of the inductor field can be mixed together.

The differences between the two types of magnetic field can be summed up as follows:

  1. The electromagnetic system requires electrical energy (an electrical panel) in order to generate the magnetic field;
  2. The depth of field of an electromagnetic drum is much greater compared to a permanent magnetic one;
  3. The permanent magnetic drum is more consistent in its performances. An electromagnetic drum requires greater electrical absorption when starting up, greater inductivity in the initial phase and has a power loss when it reaches full capacity (for further information, ask for a technical note);
  4. Huge difference in price – the permanent magnetic drum is by far the cheapest solution.

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