"ELEKTROMAG" Lifting Magnets are the result of many years of experience and latest calculating methods on a scientific basis. All magnetic, mechanical and electrical components have been ideally matched to ensure maximum efficiency, economy and safety in service.

Type LMBN Rectangular Magnets are particularly suited for handling metal sheets.

The magnet body is constructed from high permeability steel and features, together with the cover-plate of non-magnetic wear-resistant steel, outstanding strength and robustness.

The exciter coil, wound with aluminium conductor using high-grade insulating materials, is secured in the housing with a special resin compound of excellent heat conductivity.

For connection of the supply line cable, each standard magnet is equipped with a watertight terminal box divided into one coil connection chamber and one cable connecting chamber.

The standard chain suspension consists of two single fall chains, each with a suspension ring. On request a two- fall suspension with common ring can be supplied at extra cost.

Larger magnets, starting with type LMBN 30/80, can be equipped with two-fall or four-fall suspensions at extra cost.

For conveying metal sheets, lifting Magnets offer substantial advantages over mechanical handling aids including :

• easy picking up and setting down of load.
• labour saving; the crane driver is not delayed, by manual load slinging.
• fast material handling
• gentle handling of sheets(no damaging of edges, no deformations).
• maximum utilization of storage space,
• Simplified sorting of sheets.

1. Permissible relative duty cycle is 50% / 10 minutes.
2. Tear-off forces listed are approximate values. They relate to a massive, thick plate(slab) at an air gap of b/300 or b/100 (b=magnet width). Values apply to warmed-up service condition reached after five hours of continuous operation with a duty cycle of 50%/10 min. Rated power input for cold magnets listed in column 2 governs selection of suitable electrical accessories. 1 daN = 0.981 Kg).
3. Values listed are the maximum load carrying capacity of two vertically loaded chains, allowing for a fourfold safety. (The magnet weight has not been taken into account).
4. Magnets for difficult operating conditions or hot material are available. For these technical data and dimensions will vary insignificantly.

The wide carefully graduated range of size offers a suitable magnet installation for every lifting application. The smaller sizes, Type : LMBN 20, designed for picking up single sheets within a specified range of thickness.

The wider magnets can lift several stacked sheets, their number depending on model size, sheet size and gauge. By fitting suitable control gear, sheets can then be discharged singly or in a stack.>

Tear-off force of each magnet as a function of material thickness 'S' and air gap is calculated as follows: Where the load covers the entire pole face, multiply the figure found on the appropriate diagram for the given size with the factor found in column 5 of table.

Where the load does not have a level but a stepped surface. e.g. stepped, capacity may be approximately determined as follows:

Divide the load into several sections at right angles to the magnet length, then calculate lifting capacity for each section, taking into account the air gap for each (inclined faces should be treated as horizontal sections with correspondingly larger air gap). Add the capacities for all sections to obtain estimated total capacity.

A magnet of type LMBN 40/125 is to lift a 30 mm thick steel plate of 1000 X 1000 mm whose upper surface is fitted with ten 20 mm wide and 3 mm thick ribs running parallel to one edge. The magnet is placed across these ribs, and the pole face is now in contact with ten sections each 20 mm wide, the remainder of the plate, i.e.ten sections each of 80 cm wide, is 3 mm away from the magnet. Look up diagram for LMBN 40 fixing an air gap of 0.5 mm for parts in direct contact with pole face to allow for possible contamination and unevenness and an air gap of 3.5 mm for all other sections. Tear-off force is then calculated as follows.

10 x 2 x 160 = 3200 daN
10 x 8 x 120 = 9600 daN
total = 12800 daN

In the interest of safety, weight of load should not exceed half the magnet tear-off force as listed in the diagrams (see example 2)

For safe and reliable transport of flexible loads such as sheets, correct mounting of magnets to suit the load handled is essential. The following rules should be observed. Do not suspend magnets in a rigid arrangement but allow them to tilt slightly around their length axis so that pole faces can follow the slope of a sagging sheet. For this reason Type : LMBN is designed for only two suspension points on top of the magnet. Magnets should be placed as symmetrically as possible to the center of gravity of the load.

Maximum sheet length across the magnet = 2 x X2 and in longitudinal direction to the magnet = 1 + 2 x X3
Note : X3 = X2

maximum sheet length across the magnets = 2 x X2 + Z x X1
( Z = number of magnets less 1 )
and along the magnets = 1 + 2 x X3
Note : X3 <= X2 and X3 <="0.408" x X1

Minimum bending stress is achieved at X2 = 0.408 x X1 and X = ( X total ) / ( Z + 0.816 )

Calculation example :

Dimensions of sheet : 12 m x 5.5 m thickness 25 mm,
weigh : 12950 Kg. Air gap between level sheet and magnet is assumed to be 2 mm.
Factor of safety 2 : 1

The number of magnets is governed by sheet thickness, whereas the size of the magnets is governed by the weight of the sheet.

1. X MAXIMUM ACCORDING TO ILLUSTRATION 5

   X1 max = 8 m
   X2 max = X3 = 3.3 m
   Since these dimensions must not be exceeded, at least two magnets are required.

2. LIFTING FORCE F REQUIRED OF EACH MAGNET

   Frequ. = ( Sheet weight(kg) x safety x 0.981 ) / number of magnets
   = ( 12950 x 2 x 0.981 ) / 2
   = 12700 daN

3. SELECTION OF MAGNETS
   (see characteristics and table)
   smallest magnet with f = 92 daN/cm and factor 139 cm is LMBN 30/140
   F available = f x factor = 92 x139 = 12790 daN approx.
4. OPTIMUM DISTANCE BETWEEN MAGNETS
   X1 = (X total) / ( z + 0.816 )
   = 12 / ( 1 + 0.816 )
   = 6.61 m

Electrical accessories required with the Lifting Magnet :
( available from ELEKTROMAG)

1. Transformer Rectifier or D.C.Generator
2. Contactor Panel.
3. Cable Reeling Drum.
4. Master Controller.