Half Magnetic Drum have a 180 degree stationary magnet system within a revolving stainless steel cover and  axis of rotation. The magnet system is constructed using fully stabilised strontium ferrite permanent magnets or rare earth magnet.The rotating cover attract the ferrous contaminants and rotates them out of the material flow.After leaving the terminated magnetic field all separated particles fall off the system.Non-ferrous materials pass the roller unaffected.