Six unavoidable faults and their solutions in concrete mixing plants

During the use of HZS90 and HZS120 concrete mixing plants, six types of errors often occur due to aging, wear and tear of parts, and environmental influences. So, how to handle the faults of concrete mixing plants? How to solve common faults? Please see the introduction below.

1. Inaccurate cement weighing

This fault manifests as the correct value being displayed after calibration with weights, but the number does not return to zero after unloading. After clearing, the number changes significantly when weights are loaded again, but the sensor resistance value is within the normal range, and there is no problem with the instrument.

Possible causes include: the angle iron of the transport fixed weighing frame is not removed; the pressure head and pressure plate are stuck; the weighing body interferes with the outside world; the three sensors are not matched; the material is overloaded during weighing.

Methods for handling concrete mixing plant faults are: If the angle iron of the transport fixed weighing frame is not removed, it should be removed in time; if the pressure head or pressure plate is stuck, it should be handled promptly to ensure it is smooth and without resistance; if the weighing body interferes with the outside world, it should be isolated in time; if the three sensors are not matched, sensors with consistent models should be replaced; if the material is overloaded, adjustments should be made.

2. Difficulty opening and closing the aggregate bin discharge gate when there is no material

This fault manifests as the cylinder moving slowly and weakly, but inspection shows no friction or jamming in the mechanical part of the discharge gate, and no air leakage in the solenoid valve or cylinder.

Possible causes include: Airway blockage, such as the air-water separator filter element of the three-in-one unit at the air source being too dirty, causing airway blockage, reducing the gas flow rate per unit time, and thus causing the cylinder to move slowly; the silencer is too dirty, reducing the pressure difference between the rod cavity and the non-rod cavity during cylinder movement, causing the cylinder to move slowly.

Methods for handling concrete mixing plant faults are: If the airway is blocked, the filter element should be cleaned or replaced in time; if the silencer is too dirty, the silencer should be cleaned in time.

3. No discharge from the discharge port

This fault manifests as no discharge from the outlet of the parent-child spiral conveyor when the contactor is engaged and the motor rotates clockwise. After a short time, the air switch trips; when the air switch is turned on and the motor is started again, it still trips. Observation shows no powder solidification.

Possible causes include: the main machine is reversed; the air switch is damaged; there may be poor contact in one phase of the main machine motor wiring.

Methods for handling concrete mixing plant faults are: If the main machine is reversed, simply adjust the position of any two wires of the main machine motor; if the air switch is damaged, it should be replaced; if there is poor contact in one phase of the main machine motor wiring, it should be checked and handled.

4. Mixer shaft "stalling"

This fault manifests as difficulty in rotating the mixing shaft, or even stopping, when the mixing host is mixing slurry.

Possible causes include: severe overload, material binding the shaft; secondary feeding due to human error; inaccurate weighing; large gap between the mixing blade or side blade and the inner wall of the tank, with foreign objects entering and getting stuck; low voltage; incorrect mixing parameter settings.

Methods for handling concrete mixing plant faults are: If there is a severe overload and the material binds the shaft, the mixing capacity should be adjusted, and the solidified slurry should be cleaned up in time; if secondary feeding is caused by human error, the excess material should be removed and operations should follow the process flow; if the weighing is inaccurate, the operator should recalibrate; if there are foreign objects stuck between the mixing blade or side blade and the inner wall of the tank, the gap between the blade and the liner should be adjusted to no more than 5 mm, and foreign objects should be cleaned up in time; if the voltage is too low, the circuit voltage should be rechecked; if the parameters are set incorrectly, the corresponding batching data should be carefully checked and corrected in time.

5. Main unit discharge gate cannot be opened

This fault manifests as the main unit discharge gate cannot be opened when the mixing plant is operating automatically, and the discharge indicator light does not light up after mixing is complete.

Possible causes include: foreign objects or accumulated material between the discharge gate and the sealing plate; insufficient pressure in the pneumatic system, internal leakage of the cylinder, or damage to the oil fogger; loose or poor connection between the solenoid valve and the relay, or damage to the relay; burnt solenoid valve coil or stuck valve core; damaged time relay, causing no normal input signal to the PLC.

Methods for handling concrete mixing plant faults are: If there are foreign objects or accumulated material between the discharge gate and the sealing plate, the foreign objects and accumulated material should be cleaned and the discharge gate should be flushed; if the pneumatic system pressure is insufficient, the cylinder has internal leakage, or the oil fogger is damaged, the oil fogger, joints, and cylinder should be checked for damage; if the connection between the solenoid valve and the relay is loose or poor, or the relay is damaged, the relay contact output and wiring should be checked, and replacement should be considered if necessary; if the solenoid valve coil is burnt or the valve core is stuck, the solenoid valve should be replaced; if the time relay is damaged, it should be replaced.

6. Conveyor belt deviation

This fault manifests in three situations: First, the conveyor belt deviates to the same side under both no-load and load conditions, that is, the center line of the conveyor belt deviates laterally, and the conveyor belt deviates to the side with less material; second, the conveyor belt deviates left and right without a fixed direction; third, the conveyor belt deviates in the middle of the entire conveyor belt conveyor.

Uneven foundation, material sticking to the flat rollers, imbalance between the trough rollers, and imbalance in the adjustment of the main and passive rollers can all cause conveyor belt deviation. If the conveyor belt deviates to the same side under both no-load and load conditions, it indicates that the tightness on both sides of the conveyor belt is different or the frame is uneven. In this case, the frame foundation should first be leveled, the material sticking to the flat rollers should be removed, and the adjusting screw or counterweight of the tensioning mechanism should be adjusted. If the conveyor belt deviates left and right without a fixed direction, it indicates that the conveyor belt is loose, and the tensioning mechanism should be adjusted. If the conveyor belt deviates in the middle of the conveyor, the position of the roller set can be adjusted for correction, as shown in Figure 1.

Adjustment method: If the conveyor belt deviates to one side, the roller set on that side should be moved laterally in the direction of conveyor belt movement, or the roller set on the other side can be moved backward (or the roller support on the other side can be appropriately raised). The method for adjusting the return roller set is the same as that for the carrying roller set. For conveyor systems with longer conveyor belts, adjusting the roller set is very effective.

Adjusting the idler roller is a crucial step in correcting conveyor belt misalignment. This roller must be installed vertically to the center line of the conveyor's material flow direction; otherwise, misalignment will inevitably occur. As shown in Figure 2, if the conveyor belt deviates to its right, the right-side bearing housing should be moved forward (or the left-side bearing housing moved backward); if the conveyor belt deviates to the left of the roller, the left-side bearing housing should be moved forward (or the right-side bearing housing moved backward).

If the conveyor belt is misaligned relative to the driven roller, the adjustment method is the opposite of that for the drive roller.