What are the different types of screw conveyors?
Thursday July-17 2025 08:50:06
The function of screw conveyors is to achieve axial displacement of bulk materials in a specific space through rotating spiral blades. This type of equipment has many specific types, covering various structural forms such as shaft and shaftless, horizontal and inclined, tubular and U-shaped trough, etc., to adapt to different material characteristics and conveying environments. In terms of material handling capacity, screw conveyors can cope with material conveying needs ranging from tens of kilograms per hour to hundreds of tons per hour. Its single-machine conveying distance is usually between several meters and tens of meters. The common single-machine horizontal conveying distance can reach 30 meters, and the vertical lifting height can reach 20 meters.
What are the types of screw conveyors?
Screw conveyors are a common material conveying equipment. Its core mechanism is to push the material axially in a closed trough or pipe through a rotating spiral blade. This equipment is used in many industrial fields because of its relatively simple structure, easy sealing and ability to achieve multiple conveying angles. According to its structural characteristics, functional design and specific application scenarios, screw conveyors can be divided into many types.
Screw conveyors with shaft
Structural characteristics: The existence of the central shaft provides stable support for the spiral blades, making the rigidity of the entire spiral body better. The spiral blades are usually continuous solid blades, but in some specific applications, belt, paddle or variable pitch blades may also be used. The bearing supports are located at both ends of the spiral shaft, and sometimes intermediate bearings are also set in longer conveyors.
Working principle: When the drive device drives the spiral shaft to rotate, the spiral blades generate thrust on the material in the trough body, prompting the material to move along the spiral shaft. Under the action of the rotating blades, the material is affected by its own gravity, friction with the trough wall, and friction with the spiral surface, thereby realizing axial conveying.
Applicable materials: This type of conveyor is suitable for conveying powdery, granular and small block bulk materials with good fluidity, non-sticky, not easy to entangle and not high abrasiveness. Common materials include cement, fly ash, grains, sand, small granular plastics, flour, etc. Due to the existence of the central shaft, for fibrous, easy to entangle or viscous materials, the material may be wrapped around the shaft or blocked.
Advantages: mature structure, relatively moderate manufacturing cost, easy maintenance, and controllable sealing. It has high reliability when conveying non-sticky materials.
Limitations: Not suitable for conveying sticky, easy-to-wind, bulky or high-water-content materials, the center shaft may hinder the flow of materials or cause blockage. The presence of the intermediate bearing may also become an obstacle or wear point for the flow of materials.
Shaftless screw conveyors
Structural characteristics: There is no center shaft, and the spiral blades (usually thick and tough materials such as high-strength steel or special alloy steel) slide or roll directly on the inner wall of the U-shaped trough. In order to reduce wear, the inner wall of the U-shaped trough is usually paved with wear-resistant liners such as ultra-high molecular weight polyethylene or high-chromium cast iron. The two ends of the spiral blade are connected to the driving end and the non-driving end through a special structure.
Working principle: The drive device drives the spiral blade to rotate, and the blade directly pushes the material forward in the trough. Since there is no obstruction of the center shaft, the material can flow more freely in the trough.
Applicable materials: This type of conveyor shows advantages in handling materials that are difficult for traditional shafted screw conveyors to deal with. It is particularly suitable for conveying materials with strong viscosity, high moisture content, easy to entangle (such as fibers, cloth strips, plastic bags), easy to agglomerate or blocky. Typical applications include kitchen garbage, urban sludge, livestock and poultry manure, filter cakes, food waste, dregs, etc.
Advantages: It significantly solves the problem of material entanglement and blockage, and reduces the workload of clearing and maintenance. The conveying channel is spacious and has good adaptability to large pieces of materials. The noise during operation is relatively low.
Limitations: Due to the lack of central shaft support, the spiral blade may be at risk of deflection in some cases, especially in situations where the conveying distance is long or the material density is high. The manufacturing cost may be higher than that of shaft screw conveyors of the same specifications.
U-shaped trough screw conveyors
Structural characteristics: There is usually a removable cover above the trough body for easy inspection, cleaning and maintenance. The trough body material is mostly carbon steel or stainless steel.
Advantages: Simple structure, relatively low manufacturing cost, easy to install and maintain, and easy to observe the material status.
Applicable materials: Widely used for conveying various powdery, granular and small bulk materials, especially for occasions that do not require strict sealing or require frequent cleaning.
Limitations: The sealing performance is not as good as the tube type, and it may cause environmental pollution when conveying materials that generate a lot of dust. It is not suitable for conveying toxic, harmful or highly volatile materials.
Tubular screw conveyors
Structural characteristics: The shell is a circular tube, usually welded by steel pipes or stainless steel pipes. The material is fed from one end and is pushed by the spiral in the pipe to the other end for discharge.
Advantages: It has excellent sealing performance and can effectively prevent dust leakage and external pollution from entering. It is especially suitable for occasions with high requirements for environmental cleanliness or conveying toxic, harmful and volatile materials. At the same time, the tubular structure also has good strength and rigidity.
Applicable materials: Widely used in food, fine chemical and other industries to convey various powdery and granular materials, such as flour, starch, pharmaceutical raw materials, plastic particles, activated carbon, etc.
Limitations: Due to the complete closure, maintenance and cleaning are not as convenient as U-shaped troughs, and the handling is also more complicated when the material is blocked.
Screw conveyors are an important material transfer tool, and their diverse types can meet the different requirements for material transportation in industrial production. Whether it is a shaft design for conventional powder and granular materials, or a shaftless structure for viscous or easily entangled materials; whether it is horizontal short-distance transportation, or inclined or even vertical height difference transfer; or whether it is a U-shaped trough or a fully enclosed tube structure according to the characteristics of the material, each type corresponds to specific operating conditions and material handling solutions.
