Spiral classifiers can be divided into single-spiral and double-spiral classifiers based on the number of spiral shafts. Based on the overflow weir height, they can be divided into high weir spiral classifiers and submerged spiral classifiers. The slurry from the grinding mill is fed into the trough through the feed inlet located in the middle of the settling zone. The trough is inclined, and below it is the classification and settling area. The spiral rotates slowly, stirring the slurry, causing fine particles to remain suspended and flow over the overflow weir, while coarse particles settle at the bottom and are transported to the discharge outlet as returned sand by the spiral. The position of the overflow weir is higher than the center of the bearing at the lower end of the spiral shaft but lower than the upper edge of the spiral at the overflow end.