Pivoted Weigh Screw for Alumina Dosing
ModQuip designed, manufactured and supplied a purpose-built Pivot Weigh Screw system for accurate gravimetric dosing of alumina at a major new processing facility in Gladstone, Queensland.
Problem
A Queensland-based bulk materials handling and processing solutions provider required a reliable weighing and feeding solution for an alumina processing application in Gladstone.
The system required accurate dosing of alumina within the green fields process equipment. The Pivot Weigh Screw was required to be installed downstream of the alumina silo agitator, live bottom bin feeder and screw conveyor, it weighs and delivers into an inclined screw conveyor feeding a bucket elevator.
The application required a design throughput of 30 t/hr, with accurate gravimetric measurement and controlled feeding of alumina before the material entered the plant’s mixing tanks.
ModQuip Solution
ModQuip engineered, manufactured and supplied a complete Pivot Weigh Screw package designed specifically for the application.
The supplied system incorporated:
- Pivoted weigh screw conveyor
- Load cell weighing system
- Integrated control cabinet
- Custom structural support frame
Detailed engineering calculations and screw conveyor sizing assessments were undertaken to establish the required operating parameters.
The final design incorporated a 2,490 mm inlet-to-outlet centreline length, a 20:1 gearbox ratio and a 4 kW, 3-phase, 4-pole motor.
The system was designed to convey 28 m³/hr, equivalent to approximately 31.5 t/hr based on the specified alumina bulk density of 1.125 t/m³. The screw operated at 70 RPM with a 40% fill capacity.
The operating speed was selected to support the requirements of gravimetric weighing. Slower screw speeds help maintain a stable and consistent material bed depth within the conveyor, supporting accurate weight measurement and controlled material flow.
For the product-contact components, stainless steel construction was specified to meet the application’s product purity requirements. The structural support frame was manufactured from mild steel with a powder-coated finish and remained isolated from direct product contact.
The integrated load cell weighing system allows the Pivot Weigh Screw to continuously measure the material being conveyed, providing controlled and consistent gravimetric feeding.
Outcome
The completed Pivot Weigh Screw package provided a purpose-designed weighing and feeding solution capable of meeting the required 30 t/hr alumina throughput.
The calculated conveying capacity of approximately 31.5 t/hr provided capacity above the required design throughput, while the 70 RPM operating speed was selected to support stable material flow and gravimetric measurement.
The stainless-steel product-contact construction addressed the application’s purity requirements, while the custom support frame provided the structural arrangement required for integration into the existing process.
Following design approval and sign-off, manufacturing commenced in late January 2026. Factory acceptance testing and delivery to Queensland were successfully completed in mid-June 2026.
