Full definition
Screw conveyors are a type of mechanical device used for the continuous transport of materials, typically granular, powdery, or semi-liquid substances. They consist of a rotating helicoid, also known as an Archimedean screw, which is housed in a U-trough or a closed tube. The screw's rotation moves the materials along the length of the conveyor, making it efficient for handling bulk materials in various industries. The design allows for capacities ranging from 1 to 500 m³/h, depending on the size and design of the screw conveyor. Standard lengths can reach up to 40 meters, and for longer runs, multiple units can be installed in series to maintain efficiency and control over the material flow.
The fully enclosed nature of screw conveyors helps in controlling dust and preventing spillage, which is crucial in maintaining a clean and safe working environment. This feature makes them particularly suitable for transporting materials such as flour, cement, and sludge. However, while screw conveyors are versatile, they are not recommended for very abrasive materials due to the accelerated wear on the helix, which can lead to increased maintenance costs and downtime. Furthermore, materials that are susceptible to degradation under mechanical shear pressure may also be poorly suited for this type of conveyor.
The Conveying Equipment Manufacturers Association (CEMA) has established standards for screw conveyors, specifically CEMA 350, which provides guidelines for the design, application, and performance of these devices. These standards help engineers ensure that the screw conveyors are designed appropriately for the intended materials and operational conditions, maximizing efficiency and longevity. Proper selection and design are critical to avoid common pitfalls associated with the misapplication of screw conveyors, such as the selection of inappropriate materials or inadequate sizing of the conveyor for the intended capacity and length.