Understanding Screw Feeders
Screw feeders are used to accurately meter bulk materials. Usually employed at the start of an industrial process, their design allows for control over feed rate and capacity. Screw feeders come in a wide range of configurations to suit the requirements of various material handling applications
The Basics of Designing a Screw Feeder
A screw feeder’s most basic design features a screw conveyor that is fed by another conveyor, and the amount of discharged material is directly proportional to the amount of material introduced at the inlet. The inlet is always flood loaded and is typically mounted directly to some form of storage device such as a bin, silo, or hopper.
To ensure efficient and even cycling, many factors must be considered when designing a screw feeder. During each revolution, bulk materials are supposed to move from one flight to the next, moving towards the discharge. If a screw feeder is improperly designed, it can cause issues such as stagnant material that affect the overall efficiency of the system. For even flow of bulk materials, it is crucial that each flight increases in available volume as the screw progresses towards the discharge.
Other important design considerations include:
- Flow characteristics of the metered material
- Density of the material at all phases of handling
- Minimum and maximum feed rate or capacity
- Size of screw feeder inlet opening
- Height of material within the storage device
The Three Basic Types of Screw Feeders
There are three basic types of screw feeders, each of which is ideal for different material handling applications. These designs include:
- Variable or stepped pitch. Variable or stepped pitch screw feeders feature a design where the size of each flight becomes increasingly longer as you progress toward the discharge. As the flights move through the inlet section, the rear-most flights will continue to pick up additional materials as they make their way forward.
- Tapered outside diameter. With this design, the outside diameter of the screw is tapered from the rear of the inlet to the shroud, allowing the screw feeder to accommodate larger volumes of bulk material.
- Mass flow. This design combines the variable pitch and tapered outside diameter design. It consists of a tapered cone at one end with short flights, and as it progresses towards the discharge, it shifts into variable pitch.
Reinke & Schomann: Craftsmanship in Screw Feeders Since 1929
Reinke and Schomann has been a family-owned business since its founding in 1929. For generations, we have specialized in the manufacture of custom-built feeder screw systems. We are able to design and build screw feeders of all types and sizes to match your exact specifications, and we handle the process in-house from start to finish.
Please contact us today to speak with one of our design professionals and begin creating your custom screw feeder system today.
