Working principle of screw conveyor

Screw conveyor, also commonly known as auger, works by pushing materials through rotating spiral blades to achieve conveying. In this process, the material does not rotate with the spiral blades, but moves by its own weight and the friction resistance of the screw conveyor casing. The surface shape of the spiral blade varies depending on the conveyed material. Common ones include solid surface shape, belt surface shape and blade surface shape. In addition, the screw shaft of the screw conveyor is equipped with a thrust bearing at the end of the material movement direction to withstand the axial reaction force of the material. When the machine length is longer, an intermediate hanging bearing will be added to enhance stability. Screw conveyors are widely used in many fields such as minerals, feed, grain and oil, and construction. They are often used to convey chemical and building materials such as high-temperature powders or solid particles, and are usually made of refined steel.
The working principle of the screw conveyor is mainly divided into three categories: pushing method, centrifugal induction method and gravity sliding method. The pushing method uses spiral blades to transport materials and is often used for unloading at the bottom of the silo. At this time, the material fills the spiral and is subjected to a large static pressure. The centrifugal induction method is suitable for vertical or steeply inclined screw conveyors. Under high-speed rotation, the centrifugal force on loose materials is much greater than other external forces. The gravity sliding down method is suitable for low-speed screw conveyors. Under the action of gravity, the material slides down along the spiral surface, resulting in axial displacement.
Although the sliding down method has a small conveying capacity, its advantage is that the material is in a loose and free rolling state, and is less squeezed. It is particularly suitable for materials that are easy to agglomerate and abrasive. When a standard screw is used, the sliding down speed is faster, and it has a certain adaptability to inclined conveying. The inclination angle is usually controlled within 20°.
Next, let’s discuss the maintenance of the screw conveyor.
The screw conveyor is mainly composed of a screw shell, a drive part and a bracket, so maintenance needs to be carried out in parts. The shell part generally does not require special maintenance unless the material is acid-base corrosive and needs to be cleaned when it is shut down. The drive part is the core of the conveyor and the oil needs to be replaced strictly and regularly. The spiral body part needs to pay attention to the spiral blade, which is a vulnerable part, and the degree of wear depends on the abrasiveness of the material. When the gap between the blade and the shell is too large or deformed, it will affect the conveying capacity and needs to be replaced in time. In addition, it is necessary to regularly check the lubrication of the transmission shaft and the connecting shaft, as well as the tightness and rust of the inlet and outlet.