Design Principles of Screw Conveyor


1. Design reference of screw conveyor
When it is confirmed to use screw conveyor for bulk material transportation, the problem is how to design conveyor system economically and reasonably. All the equipment requirements should be taken into consideration before design, which are design reference. Conveyor design references include material property, conveying capacity, conveying distance and working & environmental conditions.
1) Material property includes material bulk density, particle size, maximum lumpiness (whether the material lump size is uniform and is screened out), material moisture, abrasiveness, cohesiveness, wear coefficient and etc.
Material particle size and mass content will affect the diameter of screw blades. If the material contains more rigid particles, in order to avoid the phenomenon of material blockage, the clearance between screw blade and U type screw conveyor trough should be equal to the maximum size of mass particle.
2) Conveying capacity
The conveyor capacity can be directly determined if the material flow is uniform. Otherwise, it should not to increase the design capacity to meet the maximum conveying capacity of uneven material flow. The best solution is to install a feeding hopper to solve the problem of uniform material flow.
3) The dimensions of screw conveyor include maximum length, inclination angle, lifting height and connection size, etc.
4) Working and environmental conditions
a. Environmental conditions: outdoors or indoors, ambient temperature, environmental protection requirements, etc.
b. Working conditions: mobile or fixed, feeding and discharging methods, etc.
2. System design of screw conveyor
The following points should be taken into consideration for the design of screw conveyor system.
1) Reasonable loading method, including the requirements of feeding and discharging devices.
2) Conveyor mutual relations in transmission line. The start-up sequence is started from material receiving conveyor. Shut-down sequence is started from material feeding conveyor.
3) If above requirements of start-up & shut-down sequence can't be met, surge bin can be added between conveyors to improve adaptive capacity and operation rate of the system.
4) Environmental protection requirements. Sealing type conveying or necessary dust-cleaning apparatus should be used for large dust transportation.
5) The supply availability of the standardization & universalization of components and quick-wear parts.
6) Long-distance and large capacity screw conveyors are preferred to use. The arrangement form of screw conveyor is generally series connection. When one conveyor malfunctions, the whole transmission line will stop conveying work, which will reduce equipment operation rate. In order to improve operating efficiency, multiple short-distance conveyors can be replaced by one long-distance conveyor.
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