Overband Magnetic Separators
and Suspension Magnets


RANGE OF APPLICATION


In many branches of industry ELEKTROMAG Overband Magnetic Separators and Suspension Magnets have become indispensable for decades. They are used for removing magentics parts from non-magnetic material in order to protect crushers, mills, procescing plants etc. against too much wear and damage. They serve for cleaning non-magnetic bulk goods with iron contamination, for instance cleaning of foundry sand, fodder and the like. They are used for recovering magnetic material from ore, steel mill slag etc. Generally, overband magnetic separators and suspension magnets are installed above conveyor belts, vibratory feeders or chutes. They pick up ferrous metal parts from bulk goods. In most cases, the magnets can also be installed in an existing installation without much expense.

When using overband magnetic separators and suspension magnets, many factors must be considered for the various applications, and it is impossible to list them all in a brochure. Each application, each material and each kind of conveying involves different problems.

Owing to the shape ( demagnetization factor), long, barshaped and large iron parts can be better separated than short, cube-shaped bulbous and small iron parts.

The efficiency of the overband magnetic separator or suspension magnet depends on the pole size, pole distance field intensity in the conveyor burden, lines of the magnetic flux conveying speed and properties of the material to be separated.

Large burden depths, large lump sizes, sticky or humid material render the separation more difficult.


METHOD OF OPERATION


ELEKTROMAG Suspension magnets are used when only small contamination levels are encountered. The material accumulated on the pole face must be removed at regular intervals. When stopping the plant to the material and/or long and bulky pieces are contained in the conveyor burden. This material is attached by the magnet and is transported out of the magnetic field and ejected by the discharge belt running around the magnet.


DESIGN


ELEKTROMAG Suspension magnets consist of a magnet body and exciter coil. Cross sections, shape and size of the magnet body are specially designed for magnet coil and power input. Thus despite compact construction, low weight and low power input, high efficiency is reached.

The magnet body is a welded steel construction of high permeability. The standard exciter coil consists of an aluminium conductor and it is manufactured by using insulating material of class `H' and mounted into the magnet body. If specially requested we can also supply coils wound with copper conductor. The coil is covered by a non-magnetic plate.

Suspension lugs and one set of turn buckles and suspension rod with bull ring are normally supplied.

Electric connection is by a terminal box. The entrance for cable fixing is fitted with a suitable cable gland.

ELEKTROMAG Overband magnetic separators consist of suspension magnet, supporting structure for the discharge belt with drive drum, tail drum and 2 additional idlers where necessary. The drums, idlers are mounted on suitable self aligning bearings. A suitable geared-motor or motor coupled to gear box is used to drive the discharge belt.

The discharge belt is a rubber/canvas or rubber/nylon belt with several plies and cleats. For re-tightening the discharge belt, the fixed axle of the tail drum is fitted with a tensioning device.


SELECTION


For making out an offer, we need the answer to the following questions:

  1. Kind of material :
    • wet or dry
    • easy-flowing or tending to lump.
  2. Bulk weight in t/m3.
  3. Chemically aggressive or neutral.
  4. Lump size- if possible distribution.
  5. Throughput per hour in cbm or tons:
    • is feed continuous or in batches.
    • maximum and average burden depth measured on belt.
  6. Size of tramp iron to be separated :
    • dimensions and weight of largest pieces.
    • dimensions and weight of tramp iron presenting no threat to subsequent processing installations.
  7. Technical data of conveyor :
    • width
    • troughing angle.
    • inclination
    • speed.
  8. Purpose of separation:
    • protection of crushers, mills, machines and other parts.
    • cleaning foundry sand, fodder, wood chips etc. from contaminating iron parts.
    • recovery of ferrous material from slag, refuse etc.
  9. Available supply:
    • three phase current, voltage frequency, power.


MOUNTING


The suspension magnet can be suspended with height adjustment above the conveyor from a suitable supporting structure, by means or ropes, chains or fastening devices.

Suspension can be made over the conveyor or over the discharge end of the conveyor. The parts of the conveyor in the stated area of the magnetic field (idlers, belt head drums, troughs, sieves etc.) must be made of non-magnetic material.

Overband magnetic separators are either suspended across the conveyor or in line above the discharge end of the conveyor. Also here suspension should be adjustable in height by means of ropes, chains or fastening devices above the conveyor from a suitable supporting structure.

In the case of mounting in line above the discharge end of the conveyor , it should also be possible to adjust the suspension height and angle to the conveying direction. The figures above show where non-magnetic material must be used.

For instance, the head pulley of a conveyor belt, the spout of a feeder or a sieve, the plate dividing magnetic and non-magnetic material must be non-magnetic.

Mounting the overband magnetic separator in the line above the discharge end of the conveyor increases the efficiency of the magnet and facilitates the iron discharge because tramp iron leaps out toward magnet face as material looses and fans out. It is ideal where long pieces, rods, etc. are likely to be encounted as inline belt moves faster than main belt.


ELECTRICAL CONNECTION


D. C. supply is required of the coils. A suitable rectifier is necessary for each magnet. Switching ON/OFF is done on the three phase / A.C. side of the rectifier.

By this kind of connection no additional protective measures against voltage peaks are required which arise by the high inductivity of the magnet when switching off.

The rectifiers and the three phase current motors are dimensioned for 415V/50Hz. The units can also be supplied for other voltages and frequencies.


MAINTENANCE


Maintenance is confined to regular checks of oil level in the gear box, to checks of the discharge belt and to normal.


GENERAL REMARKS


ELEKTROMAG Overband magnetic separators and suspension magnets comply with the `Regulations for elektromagnetic equipment' VDE 0580. All technical data listed in this brochure apply to normal operating conditions. The magnets can be used in a temperature range between -20 degree Centigrade and + 40 degree Centigrade.

Where extraordinary operating conditions prevail - such as high ambient temperature (over 40 degree Centigrade) high air humidity, chemically aggressive atmosphere, severe dust pollution, handling of wet and sticky material, very large tramp iron, hot material, marked voltage fluctuation in the supply network, special magnets are required.

Many such special magnets are already in operation and are technical developed according to the requirement of our customers.

We reserve the right to carry out alterations in line with further technical development without prior notice.


COMBINATION UNITS


  • for extra protection from tramp iron.
  • for increased clearing.
  • for heavy duty separation applications.


SYSTEM 1:

ELEKTROMAG Suspended or overband magnetic separator for initial tramp iron removal followed by :

ELEKTROMAG Magnetic head pulley for removing remaining iron. This ensures double protection removing even very small particles.


SYSTEM 2:

ELEKTROMAG Suspended or overband magnet for removal of ferrous contamination followed by :

ELEKTROMAG-EAB Electronic metal detector with a highly sensitive search coil which can sound alarm and stop the conveyor when any non-ferrous contamination passes through the field of the search coil. Sensitivity of search coil can be easily adjusted so that it acts only for objects large enough to be damaging. This combination unit is particularly useful where damaging non-magnetic tramp metals (e.g. manganese steel, stainless steel, brass etc. ) are likely to be encountered in addition to tramp iron.


SYSTEM 3:

ELEKTROMAG -EAB Electronic metal detector followed by :

ELEKTROMAG Suspended or overband magnet running with a low basic excitation.

Particularly useful where burden depths and belt speeds are excessively high. When the search coil detects the presence of tramp iron the metal detector actuates a circuit that overexcites the magnet coil briefly thereby creating a powerful magnetic field to ensure tramp iron extraction. After extraction, the excitation automatically drops back to the original level which is sufficient to hold the attracted tramp iron.


Magnetic Separators/Lifting Magnets