Spiral classifier, working with ore mills to form close circulation in the concentrating plant, whose classification process depends on the sedimentation velocity of the particles. Its external appearance is a rectangular oblique chute, whose bottom is semi-circular; the inclination angle of the bottom of the chute is from 120 to 18.50.There is 1 or 2 vertical axles installed in the chute, spiral blades are installed along the axle one after another. With the help of the drive motor on the top, the whole machine can drive the screw shafts to rotate. If there are two spiral axles in the chute, all of the spiral blades rotate outwards when the machine is viewed from the top. The slurry, fed from the flank of the chute, form classification of sedimentation at the bottom of the chute. Coarse particles dip into the bottom of the chute, and then they will be pushed to the top by the spiral and discharged. During the transportation process, the coarse particles dehydrate themselves. The fine particles, which do not have enough time to dip into the bottom of the chute, are carried by the ore pulp flow through the surface and discharged from the overflow weir. There is lifting equipment on the upper beam of the frame, which is used to adjust the distance between the spiral blades and the chute bottom and raise the spiral axle when the machine stops working, in case that the ores deposit and bury the spiral blades to damage the axles and blades when the machine starts working again.

According to the height of the surface of the liquid classification, the machines can be pided into high weir type and immersed weir type. The overflow weir of the high weir type spiral classifier;is higher than the center of the spiral axle at the bottom and lower than the top of the spiral blades. As the surface of the liquid classification is not very long, the liquid surface can feel the mixing of the spiral blades, and then this kind of machine can be used for the classification of coarse particles, whose classification granule is more than 0.15MM. The whole spiral blades of the immersed weir type are immersed in the flooding level, the area of the classification is large and stable, which is suitable for the classification of the fine particles, the classification granule of which is less than 0.15MM. It has high productivity. Besides, there is one kind of low weir type of spiral classifier, whose surface of the liquid classification is lower than the spiral bearing. The area of the liquid surface is small，but the machine can mix strongly. It is mainly used in the washing of the ores with mud.