Common Problems and Solutions for Concrete Mixers

Common problems and solutions for concrete mixers are as follows:

Stirring system malfunction

• Insufficient stirring power or overloaded operation
  • Reason : Overloading with a single batch, excessive clearance between the agitator blades and lining plates, loose drive belts, and inadequate motor cooling.
  • Resolve : Adjust the weighing system to ensure accurate ingredient dosing; inspect and adjust the clearance between the blades and liner plates to 3–8 mm; regulate the tension of the drive belt; and enhance the motor's cooling conditions.
• Abnormal vibration and noise in the mixing system
  • Reason : Foreign objects inside the mixing drum, deformation or wear of the mixing blades, bearing wear, loose bolts in the gearbox or coupling, and fatigue damage to structural components.
  • Resolve : Shut down the machine to remove foreign objects; inspect, repair, or replace the blades; replace the bearings; tighten the bolts; and repair or replace any damaged structural components.
• The mixing unit automatically shuts down or frequently restarts itself.
  • Reason : The safety shutdown switch has been activated, the power supply voltage is unstable, or there is a fault in the circuit or control system.
  • Resolve : Inspect and tighten the safety maintenance switch; check voltage stability; troubleshoot the circuit and control system, and eliminate false tripping of the overload protector.

Electrical system malfunction

• The motor fails to start or stops immediately after starting.
  • Reason : Phase failure of the power supply, short circuits in wiring, burnt-out or shorted motor windings, incorrect wiring in the control circuit, poor contact at relay or contactor contacts, and malfunctioning overload protection devices.
  • Resolve : Inspect and repair the power lines; test the motor windings, and either repair or replace the motor; check the control circuit wiring, and fix or replace relays and contactors; eliminate the cause of overload, then reset or replace the thermal relay.
• Electromagnetic valve and cylinder are operating abnormally.
  • Reason : The solenoid valve coil is burnt out or internally blocked, there’s air leakage in the air circuit or insufficient compressed air power, the test control signal is abnormal, and the limit switch is malfunctioning.
  • Resolve : Test the solenoid valve coil resistance, replace or clean the valve core; inspect the air circuit for sealing and verify the compressed air source pressure, repairing any air leaks; check the control relay output; examine the proximity switches and limit switches, replacing them if necessary.

Air circuit system failure

• The air compressor is operating unstably.
  • Reason : Check valve failure, piston ring damage, intake valve flap issues, clogged air filter, or problems with the power connection or electrical control system.
  • Resolve : Replace the check valve, piston rings, and intake valve reeds; clean or replace the air filter element; inspect the power wiring and control panel, and check the oil level and oil quality.
• Cylinder action is slow or fails to operate fully.
  • Reason : Insufficient air pressure, air compressor malfunction, air line leakage, improper adjustment of the pressure-reducing valve, inadequate capacity of the air receiver tank, wear of internal seals within the cylinder, failure of solenoid or pneumatic valves in the control air circuit, excessively rapid exhaust speed, and clogged silencer.
  • Resolve : Inspect the air compressor and related pipelines, adjust the air pressure, and repair or replace any leaking components; disassemble the cylinder and replace the seals; check the solenoid valves or pneumatic valves in the control air circuit, and clean the silencer.

Waterway and admixture system failure

• The water supply system experiences insufficient or unstable water delivery.
  • Reason : Pump motor failure, impeller wear or blockage, leaks or obstructions in water piping, malfunctioning water tank level gauges or sensors, or issues with the inlet valve or flow control valve.
  • Resolve : Repair or replace the pump motor; clean or replace the impeller; inspect and clear the water supply pipes; calibrate the level gauge or sensor, and check the inlet valve and flow control valve.
• Large measurement errors or inability to add liquid admixtures smoothly
  • Reason : Metering pump failure, malfunction of the metering system controller, insufficient admixture material, or pipeline blockage.
  • Resolve : Inspect the metering pump, repairing or replacing worn components; check the metering system controller to ensure proper parameter settings and accurate sensor signals; replenish the additive materials and clean or replace any clogged pipeline fittings.

Material handling system failure

• Aggregates conveyor belt deviation
  • Reason : The roller installation is misaligned or unevenly worn, the belt tension is insufficient, and there’s an issue with the belt quality.
  • Resolve : Adjust the position of the idlers and replace those that are severely worn; adjust the tensioning device; ensure materials are evenly distributed across the belt, and replace the belt if necessary.
• Powder feed rate slows down or stops feeding.
  • Reason : The discharge port of the powder tank is blocked, or the valve is malfunctioning; material arching occurs inside the powder tank; material clumps form at the inlet of the screw conveyor; and the pneumatic conveying fan responsible for powder transport has failed.
  • Resolve : Clear foreign objects from the feed inlet and replace the valve; break up material bridging inside the powder tank; remove accumulated material at the inlet of the screw conveyor; inspect the powder conveying blower, and check or replace its components.