Quick Troubleshooting Tutorial: Aggregate Blockage and Weighing Fluctuations in Concrete Mixing Plant Aggregate Mixers
The PLD series aggregate mixer is the core weighing and feeding component of all HZS stationary concrete batching plants and YHZS mobile concrete batching plants. In daily construction, two of the most common faults severely limit continuous production: aggregate bridging and material blockage in the hopper, and unstable weighing readings on the control panel.
Blockage leads to uneven aggregate proportions, while fluctuating weighing readings result in significant batching deviations. Both faults directly lead to the production of substandard concrete, causing line shutdowns, delaying project progress, and increasing spare parts replacement costs. Many operators spend hours blindly searching for faults without standardized inspection logic. This article provides a complete quick maintenance procedure, root cause analysis, and long-term prevention plan for these two typical faults.
- The aggregate fails to fall automatically, and an empty bin weighing signal continuously appears after opening the discharge gate;
- Intermittent feeding causes some material to flow out, resulting in a large weighing error in a single bin;
- The discharge gate cannot be fully opened or closed, and gravel jams the gate plate, hindering its movement.
- Wet mortar and viscous aggregate form material bridging within the bin; high humidity in rainy and tropical regions exacerbates material adhesion to the bin walls.
- Large stones, broken steel bars, and construction debris fall into the bin, jamming the discharge gate gaps.
- Thick layers of solidified mortar residue accumulate on the inner wall of the hopper, reducing the effective discharge channel.
- The bin vibrator is damaged or has insufficient vibration force, and there is no auxiliary material breaking device to eliminate material bridging.
- Low air pressure in the pneumatic system causes the solenoid valve to jam, resulting in incomplete gate opening.
- Cover the gravel pile with waterproof tarpaulin to reduce moisture absorption;
- Clean the hopper walls of any residue before each shift starts;
- Check the vibrator and air pressure system daily;
- In long-term high-humidity construction sites, install a smooth, non-stick lining plate on the inner wall of the hopper.
- When the hopper is empty, the weighing value fluctuates randomly, and the zero point cannot remain stable;
- During feeding, the value fluctuates violently, and the weight difference exceeds the standard ±2% tolerance;
- After feeding stops, the reading cannot be quickly locked, and continuous fluctuations affect the automatic batching program.
Mechanical Interference Factors
- During vibration, the weighing hopper comes into contact with the fixed frame, conveyor trough, or limit baffle, generating external forces that interfere with the weighing sensor. Loose weighing bracket support bolts and worn rollers cause the hopper to wobble during feeding.
- Residual aggregate buildup at the bottom of the hopper creates a continuous static load, distorting the weighing baseline.
Electrical and Signal Interference Factors
- Aging load cell cables, water ingress into the junction box, and loose terminal connections cause signal interruptions and fluctuations.
- The power cords of the large motor, inverter, and weighing signal line are tangled, causing strong electromagnetic interference to the sensor signal.
- Unstable input voltage, lack of a voltage regulator, and voltage fluctuations interfere with the weighing instrument data.
- Excessive impact from falling aggregate on the load cell damages the internal strain gauge, leading to unstable signal output.
Control Parameter Setting Issues
- The weighing instrument's filter coefficient is set too low, failing to suppress high-frequency vibration jump signals.
- An unreasonable material drop compensation value and delayed unloading gate closure cause continuous material impact on the weighing hopper.
- Perform a complete weighing calibration every two weeks; perform a zero-point reset before each shift change;
- Clean residual aggregate from the weighing hopper daily to prevent dead weight accumulation;
- Check the weighing sensor wiring and junction box sealing weekly, especially in rainy coastal areas;
- Reserve an independent power circuit for the weighing control cabinet to avoid sharing power with the mixer and conveyor motors.
In construction sites with high temperatures, heavy rainfall, and desert conditions, aggregate blockage and fluctuating weighing numbers often occur simultaneously, creating a vicious cycle:
Blockage leads to intermittent feeding, causing repeated impact vibrations to the weighing hopper → triggering weighing signal fluctuations → the system misjudges the weight and repeatedly opens and closes the hopper → material accumulation and worsening blockage.
Suggested priority handling logic:
- First, eliminate aggregate blockage to ensure smooth and uniform feeding;
- Eliminate mechanical collision interference from the weighing hopper;
- Inspect and repair the sensor signal circuit;
- Recalibrate the weighing system and optimize PLC batching parameters.
- HZS Type Fixed Mixing Plant (Long Belt Feeder): Equipped with a high-power hopper vibrator and increased weighing hopper buffer baffles to reduce the impact of materials on the weighing sensor.
- YHZS Type Mobile Compact Mixing Plant: Reinforced weighing support anti-loosening structure; regularly inspect sensor cables damaged by frequent vibrations during relocation.
- Space-Constrained Horizontal Cement Silo Projects: Use sealed waterproof junction boxes to adapt to humid outdoor environments.
Aggregate blockage and weighing code skipping are the most common low-cost failures of PLD mixers, which can be completely avoided through standardized daily inspections and timely maintenance. Blindly restarting the equipment without targeted troubleshooting will only prolong downtime and accelerate the wear of gate valve cylinders, weighing sensors, and vibrators.