Design and fabrication of a screw conveyor – Mechanical project
Grain transportation from one location to another is exigent. Several disadvantages are associated with grain transportation, especially manual loading into trailers and silos. The need for a grain handling equipment became pertinent; hence, this study designed and fabricated a simple and medium size auger aimed at upward conveyance of grains into a silo.
The conveyor was fabricated from local materials considering the physical properties of the selected grains, the techno-economic properties of the machine. The conveyor is powered by an electric motor through a V belt connection.
Tests were run on the conveyor using common granular materials like maize, sorghum and gari at 13% moisture content.
Grain handling equipment is mostly used to transport grains from one location to another. The four types most commonly used for industrial and farm applications are belt, bucket, pneumatic and screw conveyors. Conveyors play an important role in the handling of agricultural materials. The high productive capacity of modern farms has created a real need for handling agricultural products in a rapid and efficient manner. The pitchfork and shovel are being replaced by power conveying equipment.
Proper selection of power conveying equipment makes it possible to integrate component parts into a smooth, efficient and functional materials handling system. There are several methods used to convey agricultural materials. The selection of conveying method greatly depends upon the nature of application and on the type of material to be conveyed. Agricultural materials may be granular,powder, fibrous, or a combination of these.
A screw conveyor consists of a circular or U-shaped tube which a helix rotates. Grain is pushed along the bottom of the tube by the helix; thus the tube does not fill completely. Screw conveyors are widely used for transporting and/or elevating particulates at controlled and steady rates. They are used in many bulk materials handling applications ranging from agriculture (i.e. conveying grain from storage bins to transport vehicles, mixing grain in storage, and moving grain in a bin to a central unloading point), chemicals, pigments, and food
processing. They are very effective conveying devices for free flowing or relatively free flowing bulk solids, giving good throughput control and providing environmentally clean solutions to process handling problems because of
their simple structure, high efficiency, low cost and maintenance requirement. They are not practical for high capacity or long transport distances due to high power requirements.
Factors considered in the design of this machine were cost, availability of the materials, rigidity and vibration stability, durability and strength of the metallic material selected to ensure corrosion and wear resistance, portability of the machine and the techno-economic status of the intended users. Also, the necessary properties of agricultural materials considered were: the physical and
thermal properties of the grains to be conveyed.
Principle of operation
Due to economic consideration, the machine was designed to load a trailer/silo with average size of 2.68 m3 within 15 minutes with the help of an operator. The granular materials to be conveyed are fed into the hopper at the lower end (when at an inclined position), the materials are then moved through the driven transmission via an electric motor positioned at the feeding end by the rotational effect of the auger and discharge the materials at the upper end through the outlet port. An adequate clearance between the auger blade and the housing
(Barrel) was considered in the design to avoid clogging and breakage of grain kernels. A V-belt and pulley was designed for the transmission components to ensure appropriate operational speed of conveyance. For effective operation, the materials to be conveyed are expected to be at safe moisture level to prevent clogging which usually hinder the performance of the transmission unit and the electric motor.
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