EN
What are you looking for?
The handling of industrial bulk solids and the use of a "one-size-fits-all" method brings about failure of the machinery. The decision of choosing between a tubular screw conveyor and a shaftless screw conveyor is one of the most critical ones for an engineer to make during the facility design phase. The wrong selection results for Screw conveyors in constant clogging, degradation of the material, or even leaks that might endanger people or properties.
The standard screw conveyor is widely used in the processing of materials, but specialized designs are necessary in the cases where the materials are sticky, abrasive or where high-pressure containment is required. This guide lists the mechanical advantages, ideal use cases, and maintenance profiles of both conveyor designs to make sure that your workflow is uninterrupted.
A tubular screw conveyor is made of a central shaft, helical flighting, and is wrapped with a circular pipe or tube. The precision and containment of this design make it the industry standard.
Main Advantages:
Excellent Sealing: The tube that is fully enclosed is the best option when dealing with hazardous, dusty, or smelly materials. This design allows high-pressure sealing and, thus, ensures that no fine particulates escape, which is very important for complying with OSHA and local air quality standards.
Quick Operation: The circular pipe reduces the distance between the flighting and the wall. So, the rotational speed is increased to the point where material does not flow over the edges, which makes it very efficient for inclined conveying.
Long Lasting: The central shaft can withstand very high twisting forces and, therefore, the conveyors can be made longer with less number of supports.
Best For: Fine powders, minerals, cement, and chemical processing.
The shaftless screw conveyor eliminates the center shaft entirely. Instead, a heavy-duty, oversized spiral (often called a "ribbon") rotates on a low-friction, replaceable liner at the bottom of the trough.
Key Strengths:
Non-Clogging: The absence of a central shaft means there is no part for "stringy," "sticky," or "matted" materials to wrap around. This feature makes it the only solution for materials that generally cause "bridging" in conventional conveyors.
High Filling Rate: The conveyor's interior is not occupied by a central shaft, thus providing more internal volume. This results in a higher filling rate and the ability to transport bulky or irregular items.
Elimination of Hanger Bearings: A shaftless design does not need the intermediate hanger bearings that are usually the first point of failure in standard conveyors.
Best For: Wastewater sludge, municipal waste, food scraps, and entangled metal turnings.
The following table outlines the standard industrial boundaries for these systems. Note that these values are based on Senotay’s high-performance alloy builds and may vary based on specific material bulk densities (lb/ft3).
The Torque Factor
A shaftless screw conveyor relies solely on the structural strength of the spiral. While effective for heavy sludge, the "pulling" tension over very long distances can cause the spiral to stretch or deform. In contrast, a tubular screw conveyor uses its central shaft to maintain rigid structural integrity, making it the preferred choice for long-distance transport of dry solids.
Friction and Liners
Shaftless systems require high-molecular-weight (UHMW) or specialized ceramic liners. Because the spiral "rides" on this liner, it is a primary wear part. Tubular systems, however, generally feature a small clearance between the flighting and the tube, meaning there is no metal-on-liner friction during standard operation.
Incline Physics
Tubular systems are generally more efficient at angles over 25°. The enclosed pipe reduces "material fallback," whereas the open-center nature of a shaftless spiral allows more material to tumble backward as the incline increases.
Bearing Management
In a tubular screw conveyor, internal hanger bearings are the primary maintenance point. These must be lubricated and checked for wear regularly. By choosing a shaftless design, you eliminate hanger bearings entirely, significantly reducing the complexity of your maintenance schedule.
Liner Replacement vs. Shaft Alignment
The labor involved in a shaftless system usually centers on replacing the trough liner. In a tubular system, maintenance might involve re-aligning a bent central shaft or replacing worn flighting. For wet, corrosive materials (like sludge), the shaftless system usually wins on TCO because there are fewer metal components to corrode.
Tubular screw conveyors are frequently the preferred discharge method for an industrial dust collector. This integration ensures that fine particulates captured by the filters are moved directly to a waste bin or silo without escaping back into the factory atmosphere, maintaining the integrity of your air filtration cycle.
Senotay manages to speak the same language as mechanical engineering and operational reality. The conveying systems at our company meet the highest global standards so that your facility would not only be compliant but also effective:
ISO 9001:2015: Quality inspections of the highest degree are done on every tubular and shaftless system.
CE & ATEX Certification This is a must for dealing with combustible dust or hazardous chemical waste.
CEMA Compliance: Our calculations for torsional strength and volumetric efficiency meet the Conveyor Equipment Manufacturers Association standards.
The decision between tubular and shaftless technology is based completely on the "personality" of the material. A dry, dusty powder would need the confinement of a tube while a wet, stringy waste would be suited for a shaftless spiral.
Are you still in doubt when it comes to picking the right spiral for your sludge or powder? Do not let a system jam happen; instead, request a Material Flow Audit from Senotay so that our engineers can develop a custom conveying solution designed specifically for the dynamics of your material.