A cement screw conveyor must refill the weighing hopper within the batching cycle without unstable flow, motor overload or unnecessary powder retention. Selecting only a tube diameter and overall length is not enough. The supplier needs the material, required mass flow and the actual geometry between the silo outlet and scale inlet.
Start from the batching cycle
Calculate how many kilograms of cement or fly ash the largest recipe requires per batch and how much time is available for powder feeding. The conveyor must deliver that mass within the available window while leaving time for fine feeding and weighing stabilization. The target is controlled flow, not simply the highest possible speed.
Measure center distance and elevation
Provide the horizontal distance, vertical rise and flange positions. These dimensions establish the center-to-center length and installation angle. Capacity normally falls as a conveyor becomes longer or steeper because material movement and internal resistance change. A nominal capacity quoted for a short, shallow installation should not be copied to a long elevated route.
Powders do not behave identically
Cement, fly ash and other mineral powders have different bulk density, aeration and flow characteristics. Silo pressure, bridging at the outlet and an inconsistent inlet feed can make the conveyor appear undersized. Identify the material and storage arrangement before selecting the screw, motor and inlet.
Plan supports and maintenance
- Confirm support points so the tube remains aligned under operating load.
- Leave access to the motor, reducer, inlet, outlet and clean-out points.
- Check flexible connections so scale accuracy is not affected by mechanical force.
- Provide space to remove the screw or service wear components.
- Confirm rotation protection, guards and electrical interlocks for the final site.
Inputs required for quotation
- Powder type and required kilograms per batch.
- Maximum powder-feeding time in the batching cycle.
- Horizontal distance, vertical rise and center-to-center length.
- Inlet and outlet flange dimensions and preferred installation angle.
- Voltage, frequency, support locations and available maintenance space.
Worked feeding-time example
Suppose the largest recipe needs 400 kg of cement and the control sequence allows 30 seconds for coarse feeding before fine feeding and stabilization. The average coarse-feed requirement is 48 tonnes per hour: 400 kg divided by 30 seconds, multiplied by 3,600 seconds. This calculation does not mean that a conveyor advertised at 48 t/h is automatically sufficient. Inclination, length, material aeration, inlet filling and the fine-feed strategy reduce the usable rate. It establishes the minimum engineering question the supplier must check against the actual layout.
Separate coarse and fine feeding
Fast powder delivery shortens the cycle, but stopping a full conveyor instantly can overshoot the target weight. A control sequence may change from coarse feed to fine feed before the scale reaches its setpoint and compensate for material still falling after the screw stops. Ask how the frequency converter, gate or control logic handles this transition. Stable weighing is more valuable than a high empty-running capacity figure.
Diagnose the system before increasing diameter
- Check whether the silo outlet is bridging or the aeration system is inconsistent.
- Confirm the screw rotates in the correct direction and receives the specified voltage.
- Inspect internal buildup, worn flights, damaged hanger components and misalignment.
- Verify that flexible scale connections are not transmitting force to the weigh hopper.
- Compare motor current when empty and loaded before concluding that the tube is undersized.
Common quotation errors
Overall tube length is not a substitute for center distance, and horizontal distance alone does not define the installation angle. Another common error is ordering one conveyor for several powders without checking cross-contamination and control requirements. Each silo normally needs a defined route to the appropriate scale. The quotation should state material, geometry, expected capacity basis, motor and reducer, inlet and outlet, supports, seals, voltage and included electrical protection.
Acceptance and maintenance checks
Commission the conveyor empty before introducing powder, then record loaded current, vibration, noise and actual feed time. Confirm that emergency stops and mixer-plant interlocks stop powder flow safely. After the first operating period, recheck supports and fasteners because settlement or structural movement can affect alignment. Maintenance access should allow inspection without dismantling unrelated plant equipment.
Review the LSY cement screw conveyor range together with the cement silo selection page and a complete stationary batching plant configuration. Send a dimensioned sketch through the quotation page; a site sketch is more useful than requesting a conveyor by diameter alone.