Sieve plate type chute hydraulic classifier, also known as Denver hydraulic classifier, is a kind of equipment using sieve plate to generate settling interference conditions. The machine is a pyramid tank in appearance that is internally divided into 4-8 grading rooms by vertical separation plates with individual sectional area of 200mm×200mm. A sieve plate is equipped at some height from the room bottom.
The sieve plate is drilled with 36 to 72 sieve holes with respective diameter of 3-5mm. Pressure water is fed under the sieve plate and flows up through the sieve hole. There are ore grain groups suspending above the sieve plate that interfere settling and layering. Coarse particles are discharged out of the center hole on the sieve plate and their discharge amount is controlled by a cone plug. Pulp is fed from one side and enters each room in order so that water ascending velocity of each room decreases one by one and the products from coarse to fine are thus obtained. Whether water ascending velocity in the grading rooms is uniformly distributed has substantial effect on the result of grading. Narrowing sieve holes but increasing their number could improve the effect to some extent. However, uneven distribution of water velocity is inevitable and it is an important reason for the stirring efficiency of secondary backflow to be not high. Merits of sieve plate type hydraulic classifier is its simple construction and without need for power. Compared with mechanical stirring type hydraulic classifier, it has low height that facilitates configuration and could be made into different specifications of four rooms, six rooms and eight rooms according to different processing capacity of the grading factory. Such kind of classifier is mostly applied to small sized tungsten ore dressing plants in China.