Cement production, concrete batching and dry-powder handling use screw conveyors to transfer cementitious powders, fly ash and mineral fillers between storage, weighing and mixing stages. The flight is the mechanical surface that acts on the material. Its geometry influences transport, mixing, resistance and wear, but does not by itself determine the powder’s intrinsic flowability.
The VOGO cement screw conveyor range is selected for the material and duty. Solid, ribbon, paddle and cut-flight arrangements serve different purposes; they are not interchangeable remedies for every powder problem. Confirm which geometry is offered in the actual proposal and drawings rather than assuming every specialist option is a standard catalogue feature.
The standard solution: solid flights
A solid flight provides a continuous helical surface around a centre pipe or shaft. It is a common starting point for ordinary powder conveying, with pitch selected for the inlet condition, inclination and material. “Solid” describes the surface, while “standard pitch” describes pitch relative to diameter; the terms are not synonyms. KWS’s flight guide distinguishes these geometries.
For horizontal or mildly inclined cement transfer, a solid flight may be appropriate once flow and load are checked. A screw directly beneath a continuously flooded silo outlet is a feeder duty, even if it looks like a conveyor. Stable discharge requires the inlet, hopper and control method to work together; the continuous helix alone does not guarantee constant flow or accurate weighing.
A continuous surface provides conveying area, but actual volume per revolution depends on fill, slip and geometry. Fine or aerated powder can flush when air and inlet conditions are poorly controlled; it is not correct to say a solid flight inherently causes fluidization. Evaluate venting, pressure differences and feeder geometry before replacing the flight type.
In a conventional shafted conveyor, the flight should operate with its specified clearance rather than continuously rubbing the housing. Abrasion by material is different from metal-to-metal contact caused by misalignment, deflection or lost clearance. Hard-facing, thicker flights or suitable alloys may extend wear life for abrasive fillers, but do not fix a rubbing shaft. Check balance, clearances and repair compatibility when specifying wear protection.
Ribbon flights for sticky or viscous material
A ribbon is a helical strip supported from the centre pipe by legs or posts. The characteristic opening is between the ribbon’s inner edge and the pipe, not simply a gap between successive turns. KWS’s ribbon explanation identifies buildup at the flight-to-pipe junction in sticky material as the problem this arrangement addresses.
Removing that continuous junction can reduce accumulation for a suitable viscous or adhesive product. It does not guarantee freedom from buildup at the trough wall, eliminate hopper bridging or prevent aeration. Do not select a ribbon merely because a powder is fine, fluidized or prone to flushing. Material co-rotation, slugging and gas-induced fluidization are different phenomena and should not be treated as interchangeable names for one fault.
The open geometry can change conveying capacity, backmixing and torque. Compare the proposed design using representative material rather than applying a universal capacity reduction or claiming that a ribbon always gives steadier discharge. Cleaning, support-leg strength and replacement access also matter. In mortar or asphalt-filler service, justify the ribbon by observed adhesion or a defined mixing task, not by a generic promise of deaeration.
Paddle and cut flights for process duties
Paddles can be fitted between continuous flights or arranged as separate blades around the shaft. Their angle, spacing and speed change both axial movement and mixing. Kase’s flight descriptions distinguish paddles added for relatively gentle mixing from other interrupted geometries. KWS also identifies paddle-only and cut-and-folded arrangements for stronger agitation.
Consequently, paddle equipment is not automatically low-impact or suitable for fragile material. For mineral fillers or additives, define blend uniformity, residence time and acceptable attrition, then test them. Mixing action does not guarantee that particles of different size or density will remain unsegregated at discharge or during later transfer.
Cut flights have notches in the outer edge that promote agitation. Cut-and-folded flights additionally lift and redistribute material. They may loosen some soft agglomerates, but are not certified crushers or a guarantee of uniform dosing. Their effect on net transport and power must be included in selection; they are usually process options rather than the default for high-throughput cement transfer.
Cooling or heating also needs a heat-transfer path and a thermal calculation. Agitating powder with paddles alone does not provide a specified cooling capacity. Agree whether the equipment is a transporter, mixer or thermal processor before comparing flight alternatives.
Engineering considerations for selection
Record bulk density and its variation, moisture, particle and lump size, cohesion, abrasiveness, normal and peak throughput, and whether the inlet is control-fed or flooded. Identify the actual problem: shaft buildup, unstable feed, wear, mixing or inclined fallback. A change of flight should address an observed cause.
For abrasive material, consider wear-resistant construction and an appropriate speed. Increasing speed to compensate for poor selection may increase wear, power and damage to the product. Centreline length and inclination affect capacity and deflection. Reduced pitch or another housing may help an inclined application, but the combination needs calculation and testing rather than a blanket rule.
Check flight diameter, thickness, shaft size, housing clearance and drive torque together. Include startup, retained material, thermal movement and credible blockage cases. Hanger and end bearings must suit the support span and load arrangement; excessive deflection can cause contact with the tube. The wear-inspection guide helps distinguish abrasion from rubbing and mechanical damage.
Use catalogue capacities only as selection references. Confirm the actual capacity and power for the material, fill, speed, inclination and operating conditions. For feeder geometry and metering, see the feeder-versus-conveyor guide. Agree an acceptance test that checks the process result as well as current, temperature, leakage and mechanical clearances.
Conclusion
Select a solid flight for a verified conveying duty, a ribbon where its open centre addresses a material problem, and paddles or interrupted flights where a defined process task justifies them. None is a universal cure for flushing, packing or segregation. Match geometry, speed, wear protection and support to the actual service and verify the result.
VOGO configures the tubular body, drive and service arrangements for the project. Review the cement screw conveyor product information or datasheet, and send the material properties, inlet condition, layout and intended flight function for confirmation.
