Automatic Transportation Equipment: Screw Conveyor

Screw conveyor introduction

The screw conveyor is a kind of machine which uses the motor to drive the screw rotation and move the material to realize the purpose of conveying. It can be horizontal, inclined, or vertical transport, with the advantages of simple structure, small cross-sectional area, good sealing, easy operation, easy maintenance, and easy to close transportation advantages. In the form of transport, the screw conveyor is divided into two types: the shaft screw conveyor and the shaft-less screw conveyor. Its shape can also be divided into a U-shaped screw conveyor and a tubular screw conveyor. The shaft screw conveyor is suitable for non-viscous dry powder materials and small particle materials (such as cement, fly ash, lime, grain, etc.). In contrast, the shaftless screw conveyor is suitable for conveying viscous and easily wound materials. (e.g., sludge, biomass, garbage, etc.)

Screw conveyor working principle

When the screw axis rotates, the material can only move forward along the conveyor’s trough bottom under the push of the blades due to the gravity of the material and the friction generated between the material and the trough wall. It is as if the nut, which cannot be rotated, were shifted along a rotating screw. The transport of materials in the intermediate bearing depends on the thrust of advancing materials behind. Therefore, the transport of materials in the conveyor is a complete slip movement. In order to make the screw shaft in a more favorable tensile state, the driving device and the unloading port are generally placed on the same end of the conveyor, and the feeding port is placed as far as possible near the tail of the other end. The force that the rotating spiral blade moves the material so that the material does not rotate with the spiral conveyor blade is the weight of the material and the friction resistance of the spiral conveyor casing to the material. There are solid surface, belt surface, and blade surface according to different conveying materials. The screw shaft of the screw conveyor has a thrust bearing at the end of the material movement’s direction to give axial counterforce to the screw along with the material. Intermediate suspension bearings should be added when the machine is too long.

Screw conveyor application

Screw conveyor is widely used in the grain industry, building materials industry, chemical industry, machinery manufacturing, transportation, and other departments of the national economy. Screw conveyor is mainly used to transport all kinds of powdery, granular, small materials. The bulk materials are grains, beans, flour, and other food products, cement, clay, sand, and other building materials, salt, alkali, chemical fertilizer, and other chemicals, as well as coal, coke, ore, and other bulk goods.

Screw conveyor is not suitable for conveying easy metamorphism, large viscosity, lumpiness, and easy to caking materials. In addition to conveying bulk materials, the screw conveyor can also be used to transport various finished items. The screw conveyor can complete mixing, stirring, cooling, and other operations while conveying materials. In the port, the screw conveyor is mainly used for unloading trucks and ships as well as horizontal and vertical conveying of bulk materials in the warehouse. It has been used successfully in domestic ports for many years to unload the material layer by layer from the two sides of the carriage by the horizontal screw shaft in direct contact with the material. The screw ship unloader, which is composed of a flat screw conveyor, vertical screw conveyor, and relative screw reclaimer, has become a kind of advanced continuous ship unloader and has been widely used in bulk cargo terminals home and abroad.

The screw conveyor is also a practical machine to accompany decanter centrifuges in the waste treatment, chemical, and oil & gas systems.