Screw Conveyor for Steel Silo

Screw conveyor, also commonly named as screw dragon in China, is a kind of continuous conveying equipment, mainly used for conveying powdery, granular and small material. It has the advantages of simple structure, small cross-sectional area, good sealing performance, intermediate multi-point of loading and unloading, safe and convenient operation, and low manufacturing cost. Because of these, it is widely used in many industries. The technology of spiral undercut type of steel silo is patented in Germany. It has good air tightness, wide application, short construction period, small investment and quick returns, small occupied area, light weight, high strength, long service life and so on. So in the industries of grain, oil, food, brewing, fodder, chemistry, building materials, electric power, environmental protection, sewage treatment and ports and other fields, it has been widely used.

Improvements of Screw Conveyor for Steel Silo

Silo Clearance

The bottom of steel silo has a variety of forms: full steel hopper, big cement hopper, and small hopper with inner-silo filling slope. For these types of silo bottom, because the angles of the filling slope and hopper are greater than the repose angle of the material, the material can rely on self-flow clearance. But when the steel silo is with larger diameter, The heights of hopper and filling slope would be larger, so construction cost will also increase, resulting that storage capacity will be affected. This will not be economic. Under this situation, people are prone to choose flat bottom of silo with screw clearance machine.

Screw cleaning machine is mainly composed of screw blade, screw shaft, screw hanging, baffles and transmission device. Screw cleaning machine is without the casing of traditional screw conveyor and both ends of supporting bearings. One end of screw shaft is fixed on transmission device that is installed on the center of steel silo, the other end is non-fixed. Screw blade is welded on screw shaft. Baffles are fixed on screw shaft through screw hanging. Under the functions of transmission device, screw shaft and screw blade will not only make axial movement, but also make circular movement as the center of transmission device located the center of silo along the silo because of its horizontal circular movement. This makes that the cleaning machine can achieve a clearing works of piled material at the late clearance process inside steel silo.

In the unloading process in a silo, most of the material will rely on gravity and have the self-flow from the main outlet in the middle of steel silo at first. When the first step is finished, the auxiliary unloading outlet will be opened to make some parts of the material piled in the screw cleaning machine naturally flow out. After reducing the load of screw clearing machine, the machine will start to clean the piled material. There is also another situation that the screw cleaning machine directly starts screw unloading system without the self-flow process of the material. Under this situation, screw cleaning machine needs to be with relatively larger power and special structure equipment.

Quadruple Screw Conveyor

Some materials, for example, soybean cake, etc., have poor mobility, so they are easy to form the material arching. If the electric gate is set and linked with unloading equipment as the traditional method, opening the electric gate, bean cake materials will not flow out from the steel silo smoothly due to the arching, which will affect normal unloading process. The outlet diameter hopper of steel silo increases from 400mm to 800mm, the electric gate changes into quadruple screw conveyor with four screw blades and screw shafts which shares a set of casing and transmission device. The screw blade can easily damage the material arching and push the material out of the silo to ensure the production needs.

Unloading Screw Device

Unloading screw device is not traditional conveyor, but it uses the screw principle. The loading principle for traditional silo is to make material freely fall to the bottom of the silo. In this process, the material has obtained great speed with a lot of energy due to gravity. In the collision with the silo bottom, the material will be easily broken and damaged. This may change the material properties. For material that has strict requirements, this is not applicable. In order to change this situation, the screw loading device of steel silo is designed out. It includes the upper bracket and down bracket respectively horizontally set in the silo roof and bottom. Conveying plate is spirally arranged on the support shaft as the order of up to down. The central position of conveying plate forms shallow groove. The outside edge of conveying plate is with the baffle. The device is simple in structure, which can effectively avoid the damage of brittle material. In this case, the material enters the silo and falls down on screw conveying plate connected to the loading inlet. The material will spirally flow along the conveying plate downwards and slide to the bottom of the silo, which can slow the falling speed of material and prevent being broken.

It has been proved by practice that the improvements of the steel silo has achieved good effects.