One of the problems facing both the designer and the user of magnetic separators is the evaluation of the body forces acting on particles in the magnetic field of the separator. Perhaps the most elegant method of evaluating the body force associated with a drum-type magnetic separator. Once the coefficients of the series are known, it is then possible to calculate the values of the radial and angular components of the field intensities and their derivatives so that the body force.

Fr can be computed by the well-known equation:

Where X’ is the magnetic moment per unit applied field and v is the volume of the particle.

For example, one inch from the drum and at the edge of one magnet shown in Figure 1,

Hr = 677.34 gauss
Hθ = 1085.70 gauss
∂Hr/∂r = 126.33 gauss/cm
∂Hθ/∂r: = 164.66 gauss/cm

In the next attempt a magnetically soft piece of ingot iron was attached to a brass rod and the rod was connected through a Honeywell Model UL4 load cell to a solid-state unbonded strain gage transducer.

In many cases it would be convenient to connect the amplifier output to one side of an X-Y recorder. If an X-Y recorder is used, one axis can be driven from a potentiometer to indicate the position of the force measuring instrument. The other axis of the recorder can be used to indicate the force acting on the soft iron.

This system worked quite satisfactorily. The only problems encountered (other than the usual nonsense associated with the electronic equipment) were the remnant magnetism and hysteresis shown by the iron sphere. These problems were solved by replacing the sphere with a cylinder of magnetic ingot iron.

From the standpoint of the errors involved, if the load cell is tilted, the true magnetic radial force must be corrected for the change in gravitational force acting on the cell. The writers are presently redesigning the cell so that this correction will not be necessary.