According to the height of the surface of the liquid classification, the machines can be divided 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.

Advantages are simple structure, reliable working condition and convenient operation.

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