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The main component of the spiral classifier is a semi-circular water tank, a screw device consisting of a shaft and a blade, supporting the upper and lower bearing portions of the screw shaft, the transmission of the screw shaft and the lifting mechanism (Figs. 1, 2). The specifications are indicated by the diameter of the spiral.
   figure 1  figure 2
The spiral classifier can be divided into single helix and double helix classifier according to the number of screw axes. According to the height of the weir, it can be divided into three types: high-grade, low-lying and sunken.
The overflow weir position of the sorghum spiral classifier is higher than the center of the bearing at the lower end of the screw shaft, but lower than the upper edge of the spiral of the overflow end. It has a certain settlement area, which is suitable for coarse particle classification, and can obtain overflow particle size larger than 100 mesh.
The overflow weir of the low-end spiral classifier is lower than the center of the overflow end bearing, so the area of ​​the settling zone is small and the overflow production capacity is low. It is usually not used for grading operations and is used to rinse mineral sand for de-sludge.
The entire spiral of the overflow end of the sunken spiral classifier is submerged under the liquid level in the settling zone. The settling zone has a large area and depth. It is suitable for fine particle classification and can obtain an overflow particle size of less than 100 mesh.
The working principle of the spiral classifier: the finely ground slurry is fed into the water tank from the feeding port located in the middle of the subsidence zone. The lower end of the inclined installation tank is the graded sedimentation zone of the slurry, and the spiral rotates at a low speed to agitate the slurry to suspend the light and fine particles. To the top, it flows to the overflow side and overflows, and proceeds to the next process. The coarse and heavy particles settle to the bottom of the tank, and are transported by the screw to the discharge port for discharge. Usually, the spiral classifier and the mill form a closed circuit, and the coarse sand is returned to the mill for re-grinding.