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Classification of Screw Conveyors

Oct. 21, 2020

Screw conveyor, commonly known as auger, is a widely used conveying equipment in the mineral, feed, grain and oil, and construction industries. It is used to convey high temperature powder or solid particles and other chemical and building materials products.

The screw conveyor uses the rotating screw blades to push the material for conveying by the screw conveyor. The force that the material does not rotate with the screw conveyor blades is the material's own weight and the frictional resistance of the screw conveyor casing to the material. The spiral blades welded on the rotating shaft of the screw conveyor have solid surface, belt surface, blade surface and other types according to the different materials to be conveyed. The screw shaft of the screw conveyor has a thrust bearing at the end of the material movement direction to give the axial reaction force of the screw with the material. When the length of the machine is long, an intermediate suspension bearing should be added.

2: Classification of screw conveyors

The screw conveyor is divided into two types: horizontal screw conveyor and vertical screw conveyor.

Screw conveyors can be divided into horizontal screw conveyors, vertical screw conveyors, bendable screw conveyors, and spiral tube (roller conveyor) conveyors according to the characteristics and structure of the conveyed materials.

(1) Vertical screw conveyor

The speed of the spiral body of the vertical screw conveyor is higher than that of the ordinary screw conveyor. The added material generates friction with the casing under the action of centrifugal force, which prevents the material from rotating with the screw blades and overcomes the material drop The gravity, so as to realize the vertical transportation of materials. The machine has a small conveying volume, a small conveying height, a high speed, and a large energy consumption. It is especially suitable for conveying powdery and granular materials with good fluidity, mainly used for lifting materials, and the lifting height is generally not more than 8 meters.

(2) Horizontal screw conveyor

When the material is added to the fixed tank, due to the gravity of the material and the friction between the material and the tank, the material accumulated in the lower part of the tank does not rotate with the spiral body, but only moves forward under the push of the rotating spiral blade, like The non-rotating nut moves in translation along the rotating screw to achieve the purpose of conveying materials. The machine is convenient for loading and unloading at multiple points, and can complete mixing, stirring or cooling functions at the same time during the conveying process. Sensitive to overload, easy to block; material is broken and lost, the structure of the horizontal screw conveyor is simple, easy to install, maintain and troubleshoot. It is suitable for horizontal or slightly inclined (below 20º) continuous and uniform conveying of loose materials. The working environment temperature is -20—+40℃, and the conveying material temperature is -20—+80℃. Its speed is lower than that of a vertical conveyor, and it is mainly used for conveying materials horizontally or at a small angle. The conveying distance is generally not more than 70 meters.

Screw Conveyor

Screw Conveyor

(3) Spiral tube (roller conveyor) conveyor

Spiral conveyor machine is a cylindrical casing welded with continuous spiral blades, and the casing rotates with the spiral blades. Due to the centrifugal force and friction, the added material rotates and is lifted by the shell together, and then slides down the spiral surface under the gravity of the material, so that the material rotates with the spiral tube to realize the forward movement of the material, as if not rotating The screw moves in translation along the rotating nut to achieve the purpose of conveying materials.

The machine has low energy consumption and low maintenance costs; when feeding at the end, it can meet the requirements of uneven feeding, and can complete various process requirements such as conveying, stirring and mixing at the same time. When the material enters too much, it will not cause jamming; it is convenient for more Point loading and unloading can transport materials with higher temperature. It is suitable for horizontal conveying of high-temperature materials; it has good adaptability to materials with high temperature, uneven feeding, anti-fragmentation requirements, anti-pollution requirements, and processes that require multiple points of loading and unloading. Practice has proved that it is effective in conveying materials such as cement clinker, dry limestone, phosphate rock, ilmenite powder, coal and slag.

The particle size of the material added from the end feed port should not be greater than 1/4 of the spiral diameter; the particle size of the material fed from the middle feed port should not be greater than 30 mm. To ensure that the cylinder does not deform, the feeding temperature must be controlled below 300°C. The machine wears extremely severe blades and troughs when conveying abrasive materials. The screw conveyor designed this time is mainly used for conveying silicon powder, which is very abrasive, so it is not suitable to use the screw conveyor.

(4) Flexible screw conveyor

The spiral mandrel of the machine is flexible, so the transmission line can be arranged according to the space curve according to the needs. According to the different length ratios of the horizontal and vertical (large inclination) sections in the layout, the working principle is designed according to the ordinary screw conveyor or the vertical screw conveyor. It is used in the occasions where the conveying line needs to be arranged randomly according to the space curve to avoid material reloading; when too much material or hard material enters the casing, the spiral body will float freely without jamming; the noise is low. Mainly used to complete the horizontal and vertical transportation of materials at the same time. In vertical conveying, the speed is generally required to be higher than 1000r/min.