Working principle: Bucket rotate around the underwater dredging wheel, scooping up the solid in the riverbed, then trommel 

classifier, with single layer or double layer screens, will separate the gravels, clay balls, water plants with need sand. 

The discharge system could be divided into single-discharge, multi-conveyor belts and chute.

Advantages:

1. Widely used in most terrains.

2. Low exploitation.

3. Easy operation which needs few staff.

http://www.yldredge.com