What is a screw feeder?
A screw feeder is a mechanical device used in various bulk material handling applications and is designed to accurately meter or feed dry bulk solids from one system to another at controlled feed rates. Screw feeders and screw conveyors are very similar in their structural configuration and yet distinct. The speed of the dry solids flowing from upstream devices (storage silos, hoppers) is adjustable with screw feeders. In other words, the volumetric flow rate of dry bulk materials discharged from the feeders can be controlled. On the other hand, unlike screw feeders, main purpose of screw conveyors is conveying the material instead of adjusting the flow rate.
Screw feeders operating principle and design
The operating principle of a screw feeder to transport dry bulk solids is based on Archimedes screw principle, which speaks of positive displacement of a fluid (bulk materials in our case) from a source to a discharge location. The feeder is typically mounted at the bottom of upstream devices and functions as a modulating conveyor. During operation, dry bulk materials are supplied to the equipment through the inlet and fill up to 100% capacity. The screw rotates within the trough and transports the dry material along the longitudinal direction of the trough to the outlet by a process of positive displacement. The screw rotation is achieved with the help of a drive unit (servo motor). The feeder can be configured at a horizontal or an inclined position. The amount of transported bulk materials is precisely calculated and modulated by altering the speed at which the screw rotates in volumetric screw feeders.
Screw feeders are typically designed to accurately meter or feed dry bulk materials within a process line. They can process dry bulk products with great accuracy at varied operational feed rates. The screw is enclosed in a tubular or U-shaped volume housing having an inlet and outlet port, respectively. Some critical parameters to consider during design include diameter, pitch, torque etc. Polimak’s screw feeders come in various lengths, sizes, configurations and materials of construction. Our feeder models include tubular screw feeders, U-type screw feeders, microdosing screw feeders, and custom-designed screw feeders. Various factors to consider during screw feeder design are:
- Screw feeder’s overall length.
- Feeder’s inlet dimensions.
- Maximum and minimum capacity.
- Flow characteristics of dry bulk solids being handled.
- Bulk material feeding rate.
Bulk materials handled by screw feeders
Polimak designs and produces screw feeders for the aforementioned industries for various industrial applications. Some of the industrial processes in which these feeders are utilised are; dosing, mixing and batching. These mechanical devices are used to handle bulk materials like rice, sugar, wheat, corn, salt, spices, coffee grains, plastic pellets, cement, coal, glass powder, sawdust, and many other bulk materials. We render an excellent variation of dry bulk solids handling equipment for our clients. Polimak aims at designing and producing cutting-edge equipment with high-quality performance during operations.