Screw conveyor is suitable for transporting all kinds of powder granular materials and small block, such as coal, gravel, lump coal and sand, cement, cereal, etc, but not suitable for conveying easy-deteriorated, stickiness, and easy-forming materials.Therefore it is always used in cement plant, chemical plant, chemical plant, factory, mine, mill, paper mill, fiber nylon factory, feed, water conservancy and etc.