Introduction

In industries such as grain processing, chemical raw materials, building materials production, and food manufacturing, the selection of bulk material conveying equipment directly affects production efficiency, material quality, and operating costs. Screw Conveyors, as traditional conveying equipment, were once widely used due to their simple structure and low cost. However, with the increasing requirements of the industry for material integrity, layout flexibility and environmental protection, Tubular Drag Conveyors have gradually become the preferred choice for high-end bulk material conveying.

Fundamental Working Principles: How They Differ

The performance differences between the two types of conveyors stem from their completely different conveying logics, which also determine their core distinctions in applicable scenarios.

Screw conveyor

The core working component of a screw conveyor is the rotating screw blade. When the motor drives the blade to rotate, friction is generated between the blade and the material, and at the same time, the blade exerts an axial thrust on the material (similar to a shearing effect), pushing the material forward along the conveying pipe. This conveying method essentially achieves displacement by squeezing the material with external force. There is continuous friction and squeezing between the material and the blades and pipe walls.

Tubular chain conveyor

The tubular chain conveyor uses a closed pipeline as the conveying channel, and inside it is driven by chains or steel wire ropes to move several discs. The materials are confined in a closed space between adjacent discs and move synchronously with the discs, achieving volumetric conveying. Throughout the entire process, the material remains relatively stationary between the disc compartments, without any additional squeezing or shearing force, and only moves along with the conveying chain.

Advantage 1: Material Integrity

Avoid material breakage

When a screw conveyor is in operation, there is a fixed gap between the high-speed rotating blades and the pipe wall. Materials are prone to being squeezed and sheared by the blades in the gap, resulting in particle breakage. Especially for brittle materials such as coffee beans, nuts and plastic particles, the breakage rate is often high, which not only increases material loss but may also affect the subsequent processing effect.

The tubular chain conveyor completely avoids this problem: the material is enclosed between the discs and moves synchronously with them. There is no shearing force or squeezing force throughout the process. The material remains relatively stationary, and the crushing rate can be reduced to an extremely low level, which can retain the original form of the material to the greatest extent.

Prevent material stratification

In many production scenarios, it is necessary to convey multi-component mixtures (such as granules + powders, mixtures of materials with different particle sizes). The centrifugal force generated by the rotation of the screw conveyor will cause materials with different densities and particle sizes to stratify - materials with higher density and coarser particle sizes move outward, while those with lower density and finer particle sizes gather in the center, resulting in an imbalance in the material formula ratio and affecting the final product quality.

The volumetric conveying mode of the tubular chain conveyor enables the material to move synchronously as a whole, and each component always maintains its original mixing ratio, fundamentally eliminating the phenomenon of material stratification. It is particularly suitable for industries with extremely high requirements for formula accuracy, such as pharmaceuticals, food, and compound fertilizers.

Advantage 2: 3D Flexible Layout vs. Linear Constraints

Screw conveyor

The structural characteristics of screw conveyors determine that they can usually only achieve linear transportation. If complex route transportation such as horizontal to vertical and multiple curves is required, it must be achieved by connecting multiple devices. This not only increases the cost of equipment procurement, but also reduces the conveying efficiency due to problems such as material residue at the lap joint and transportation loss, while occupying more workshop space.

Tubular chain conveyor

The tubular chain conveyor relies on the flexible transmission of chains and discs. A single device can easily achieve 3D conveying layouts in horizontal, vertical, inclined and multi-curve directions without the need for multiple devices to be connected. Whether it is transported from the ground to the high-level silo or bypassed the existing equipment, columns and other obstacles in the workshop, it can be flexibly adapted, significantly improving the utilization rate of workshop space, while reducing the loss and failure points in the material transfer process.

Advantage 3: Total Dust Containment & Hygiene

Fully sealed structure

Screw conveyors are mostly semi-open or sectioned sealed structures. During the material transportation process, dust leakage is prone to occur, which not only pollutes the workshop environment but also may cause safety hazards such as dust explosions (for flammable and explosive materials like flour and coal powder).

The tubular chain conveyor adopts a natural fully sealed pipeline design. Materials are transported throughout the process in a sealed space without any dust leakage. It not only meets the environmental protection zero-emission requirements but also ensures the safety of the workshop operation environment. It is suitable for the transportation scenarios of special materials such as flammable, explosive, toxic and harmful materials.

Easy-to-clean design

The bottom of the screw blades and the gap between the blades and the pipe wall of the screw conveyor are prone to form "dead corners", making it difficult to thoroughly clean the material residue. Cross-contamination is very likely to occur when changing materials, and it is especially not suitable for industries with strict hygiene requirements such as food and pharmaceuticals.

The discs of the tubular chain conveyor can form a self-cleaning effect on the inner wall of the pipeline during their movement, reducing material residue. It simultaneously supports CIP (In-line Cleaning) systems and wet cleaning solutions, enabling thorough cleaning without disassembling the equipment, significantly reducing cleaning costs and time, and eliminating cross-contamination from the source.

Advantage 4: Energy Efficiency & Operational Costs

Energy consumption advantage

The "push and squeeze" conveying of the screw conveyor needs to overcome the friction between the material and the blades and pipe walls as well as the internal shearing force of the material. The energy consumption increases significantly with the increase of the conveying distance. The "drag-and-pull" conveying of the tubular chain conveyor only needs to overcome the slight friction between the material and the inner wall of the pipe, and the discs move synchronously with the material without any additional energy loss. In long-distance (over 10 meters) conveying scenarios, the motor energy consumption is usually 20% to 40% lower than that of the screw conveyor.

Low maintenance + low loss

The blades of the screw conveyor are prone to wear due to friction and compression, and need to be replaced regularly. The maintenance frequency is high and the cost is also high. At the same time, the loss caused by material crushing and stratification also increases the production cost. The disc and chain of the tubular chain conveyor have a low degree of wear, a longer maintenance cycle, and an extremely low material loss rate. Long-term operation can significantly reduce maintenance costs and material loss costs, offering better economic performance throughout its entire life cycle.

Conclusion

Based on the above technical comparison, screw conveyors are more suitable for scenarios where the quality requirements for materials are low, the conveying routes are simple, and the budget is limited (such as the conveying of coarse bulk materials like construction sand and gravel and ordinary fertilizers). The tubular chain conveyor, with its advantages of good material protection, flexible layout, environmental hygiene and high energy efficiency, is more suitable for industries such as food, pharmaceuticals, fine chemicals and new energy, which have strict requirements for material quality, environmental protection and efficiency.