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The Efficiency of a Shaftless Screw Conveyor in Bulk Solids Transport


In the transport of bulk materials, the design and configuration of the mechanical conveyor is crucial for the efficiency and economy of the process. One of the most interesting pieces of equipment in this area is the shaftless screw conveyors, also known as Archimedes’ screws without a shaft. Although commonly used in sludge transport, their application goes beyond this. In this article, we will explore when and why a shaftless screw conveyor should be used to transport bulk solids.

What is a Shaftless Screw Conveyor?

A shaftless screw conveyor is a type of conveyor that, unlike traditional screw conveyors, does not have a central shaft. It consists of a helix that rotates within a tube or trough, moving material along the conveyor.

Technical Advantages of a Shaftless Screw Conveyor
  1. Lower Risk of Clogging: With no central shaft, there is less risk of material getting stuck or accumulating around the shaft, which is especially useful for sticky or wet materials.
  2. Better Handling of Viscous Materials: Shaftless screw conveyors are ideal for moving materials with high viscosity, as the lack of a central shaft allows for a more uniform and continuous flow of material.
  3. Easy Cleaning and Maintenance: The absence of a central shaft facilitates cleaning and reduces maintenance time, which is crucial in industries where hygiene is paramount.
  4. Prevention of Contamination: The purity of the product being transported is important in many applications, for example, chemical and food industries. Shaftless screw conveyors minimize areas where the product could accumulate and become contaminated, maintaining its quality.

Practical Applications: What Materials Need to Be Transported by a Shaftless Screw Conveyor?

Shaftless screw conveyors are particularly effective for transporting:

  1. Sludges and Slurries: In wastewater treatment, sludges can be difficult to handle due to their consistency. Shaftless screw conveyors allow for efficient transport without the risk of clogging. For example, in sewage treatment plants (STP).
  2. Food Materials: In the food industry, products such as doughs or wet ingredients can be efficiently transported, taking advantage of the ease of cleaning of these systems. For example, a common use of these type of conveyors is in meat processing facilities for the treatment of offal or in fish farms. Another very common use is in the transport of by-products from canning companies, fish markets, and other fisheries for reuse.
  3. Chemicals and Pharmaceuticals: Sticky or pasty substances common in these industries benefit from the smooth and continuous transport offered by shaftless screw conveyors.

A specific example of a chemical that requires the use of a shaftless screw conveyor is lactose powder in the pharmaceutical industry. Lactose is a common excipient in the formulation of tablets and capsules. Its handling requires special care to maintain its quality and purity. The shaftless screw conveyor is ideal for this purpose, as it minimizes the exposure of the powder to potentially contaminating surfaces and ensures a constant, smooth flow, avoiding material degradation. Additionally, the ease of cleaning of these systems helps to maintain the high standards of hygiene required in pharmaceutical production.

Another example of transportation using a shaftless screw conveyor.

Another example is the transport of calcium hydroxide, also known as slaked lime or calcium hydroxide. This material is a chemical compound widely used in various industries, including water treatment, construction, and the chemical industry. Handling calcium hydroxide presents specific challenges that make shaftless screw conveyors particularly suited for this task. The main challenge is the tendency of this hydroxide to compact and form lumps, so the absence of a core allows the material to flow more freely, preventing clog formation. Also, calcium hydroxide is abrasive, so the absence of the core reduces wear-prone components.


In summary, shaftless screw conveyors stand out for their effectiveness in transporting bulk solids across multiple industries, offering significant advantages such as reduced clogging, ease of cleaning, and optimized handling of viscous materials. This type of conveyors improves operational efficiency, prevents contamination, and maintains the quality of transported products. Their application in sectors such as water treatment, food, chemical, and pharmaceutical industries underscores their value for versatility and superior performance in handling difficult materials, consolidating them as a key solution for cleaner, safer, and more efficient transport processes.

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