Experience in operating and managing a mixing plant

1. Pre-shift Inspection

1.1 Before starting each shift, the operator should check the following: mixer reducer oil level, discharge gate hydraulic pump oil level, mixer shaft oil level (should be more than 1/2), whether the lubricant level is sufficient, whether the pressure is normal, whether there are any breaks or detachments in the oil pipes and joints, and lubricate the belt conveyor, screw conveyor, etc. Add lubricating grease as needed.

1.2 Check if there are any metal objects inside the mixer, and check if the bolts fixing the blades and liners are loose.

1.3 Turn on the main power switch → Turn on the control power switch → Turn on the purification power switch → Turn on the PLC power switch. Turn on the industrial control power switch → Start the monitoring program, and check if there are any abnormalities in the monitoring box indicator lights (oil level, oil temperature, lubricating sleeve motor operating status).

1.4 Start the mixer and belt conveyor without load for 10 minutes for warming up and check if the operation is normal, if there are any unusual noises, and if the conveyor belt is deviated or broken (if any abnormality is found, immediately notify the maintenance crew to troubleshoot).

1.5 Start the air compressor, check if the operation is normal, if there are any air leaks in the air circuit, and the air pressure should be maintained at 0.55~0.7Mpa, and the concrete arch air pressure should be 0.02Mpa.

1.6 Check the water supply system and liquid admixture system for normal operation, unobstructed pipelines, and no leaks. Ensure sufficient water and liquid admixture in the tanks.

1.7 Check if the discharge gates, solenoid valves, and cylinders are operating normally, and if the limit switches and signal lines are working properly.

1.8 Use manual mode to jog the screw conveyor and check if the operation is normal. Add lubricating grease.

1.9 It is strictly forbidden to start under load or stop midway. In case of power failure or other accidents that cause the machine to stop, first turn off the main power supply, immediately open the discharge gate of the mixer, and drain and remove the material in the drum to prevent coagulation accidents. When restarting, follow step "1" again.

1.10 The main unit should be flushed with water every 3 hours, with a maximum interval of 4 hours. Use the water pump to pump water into the main unit, stir for about 3 minutes, drain the rinse water, and then continue production.

1.11 When continuously producing high-grade concrete (C40 and above), in addition to flushing with the main unit, a high-pressure water gun must be used for auxiliary flushing.

1.12 After the main unit has been running for more than 12 hours, but no more than 24 hours, it must be shut down for thorough cleaning of the inside of the main unit and the material gate shaft by auxiliary workers.

1.13 Keep records of the cleaning and flushing for reference.

1.14 If the machine is stopped during operation and needs to be restarted, the belt conveyor must be run without load for 2-3 minutes before feeding materials. Starting and feeding materials simultaneously is strictly prohibited to prevent impact overload and damage to the conveyor belt.

2. Post-shift Maintenance and Inspection

2.1 Turn off the main power switch, lock the electrical control cabinet door (assign a dedicated person to watch), clean the inside walls of the mixer, the mixing device, the area around the discharge gate, and other areas of residual materials, and check the connecting bolts of the mixing impeller, liner, and other mixing devices.

2.2 Clean the admixture metering hopper and sweep the aggregate hopper and powder metering hopper discharge gates.

2.3 Clean the exterior of the main unit and the discharge hopper.

2.4 Drain the accumulated water from the air compressor storage tank (drain the air from the air compressor and tank in winter).

2.5 Start the powder silo dust collector and shake off the powder adhering to the filter.

2.6 In winter, the liquid in the water pipes and admixture pipelines must be drained.

2.7 Add lubricating grease to all lubrication points.

2.8 After shutdown, the control system power and main power must be turned off.

2.9 Auxiliary workers must complete the cleaning of the inside of the main unit and the material gate shaft within about 1 hour after the main unit is shut down, but no more than 2 hours.

2.10 Auxiliary workers must clean the main unit carefully and thoroughly, leaving no dead corners, especially the discharge gate and shaft of the main unit. Prevent the slurry from solidifying and drying, which may obstruct the gate switch and damage the gate, shaft, and bearings.

2.11 When cleaning, auxiliary workers are strictly prohibited from using pneumatic hammers to strike the liner, mixing arm, and mixing blades to prevent damage due to improper operation.

2.12 When cleaning the pit soil and leaked materials, auxiliary workers should not load too much soil and leaked materials onto the conveyor belt at one time, no more than 200kg, and transport them in batches to prevent overload startup from damaging the drum motor and conveyor belt.

2.13 After the auxiliary workers complete the cleaning of the main unit, they should immediately notify the maintenance worker for inspection and acceptance. If the inspection fails, the cleaning must be redone, and no excuses are accepted.

3. Weekly Inspection and Maintenance (performed by maintenance personnel)

3.1 Turn off the main power supply and assign a dedicated person to watch. Check and remove any remaining concrete residue and dirt inside and outside the mixer (performed by the operator).

3.2 Check all tightening bolts of the mixing knives and blades for looseness, and check the clearance between the mixing knives, blades, and liner (2mm). If the clearance is greater than 4mm, adjustment is required.

3.3 Check and add reducer, discharge gate oil pump, mixer shaft oil level. The oil level in the sight glass should be more than 1/2. Add lubricating grease to all parts.

3.4 Inspect the pneumatic system, including the air compressor oil, safety valve, and pressure gauge. Drain accumulated water from the air-water separator. The pneumatic system should be free of any air or oil leaks.

3.5 Inspect and adjust the connecting bolts and supports of the belt conveyor. Check if the cleaner is working properly and if the belt has any serpentine or deviation.

3.6 Check the water lines and additive pipelines for leaks. Verify that the motor and pump are operating normally.

3.7 Check the operating condition of the screw conveyor and add gear oil and grease.

3.8 Check if the electromagnetic valve, cylinder, and discharge gate of the aggregate batching scale are working properly. Add grease.

3.9 Maintenance workers should actively cooperate with auxiliary workers in the cleaning of the main machine.

3.10 After receiving the cleaning work inspection and acceptance notice from the auxiliary worker, the maintenance worker should immediately inspect and accept the machine, and should not make excuses to refuse.

3.11 Inspection and acceptance must be thorough and leave no dead corners. If the acceptance is not qualified, the auxiliary worker or the mixing plant manager should be informed of the unqualified parts and existing problems. After re-cleaning, the inspection and acceptance should be carried out again.

3.12 During inspection and acceptance, the maintenance worker should carefully check for cracks in the lining plates and damage or looseness in the blades and arms. Sign and confirm on the record sheet for future reference.

4. Monthly Inspection and Maintenance Items (Maintenance Worker Execution)

4.1 Check the operating condition of each screw conveyor, add gear oil and grease, and observe if there is any loosening or leakage of ash at the connecting parts.

4.2 Inspect the belt conveyor system, adjust the belt tension, check for oil leaks in the rollers, and replenish lubricating oil.

4.3 Check and tighten all bolts, check if the supports and guide wheels are operating normally, and check if the chute and cleaner are in the correct position, and if the belt has any serpentine or deviation.

4.4 Inspect and maintain the air compressor, clean the air filter, check for air leaks in the lubricating oil and pneumatic pipelines, check if the pressure relief valve is working properly, and check if the discharge gate switch is flexible. Add grease.

4.5 Inspect and maintain the water pump, additive pump, and motor, and check the pipelines for leaks.

4.6 Inspect and maintain the discharge gates, electromagnetic valves, cylinders, ensuring they are flexible and operating normally. Check if all travel switches and signal lines are working properly.

4.7 Inspect and maintain the mixer.

4.7.1 Check and measure the wear of the lining plates (replace if greater than 3mm).

4.7.2 Check and measure the wear of the mixing blades and arms (replace if exceeding 50% of the original size).

4.7.3 Check if the locking screws of the discharge gate shaft and bearing seat are loose.

4.7.4 Check if the motor seat locking screws are loose.

4.7.5 Check if other fastening screws are loose.

4.7.6 Inspect and maintain the valve switches of the liquid batching scale in the hopper on the main machine, and check if the sensors are working properly.

4.7.7 Inspect and maintain the main machine water pump, motor, cylinder, and pneumatic valve.

4.7.8 Check and add lubricating oil and grease to all parts.

5. Safety Precautions

5.1 When repairing the mixing plant, the main power must be cut off, the electrical control cabinet door must be locked, and the key must be kept by the electrician. Power on/off must be operated by the electrician.

5.2 When starting the belt conveyor, mixing host, and other motors, it is necessary to observe whether there are people or other debris on the motor to prevent injury or equipment damage during startup.

5.3 During cleaning, do not use water to wash motors, electrical switches, electromagnetic valves, and other electrical equipment to prevent electric shock and damage to electrical equipment.

5.4 Personnel are strictly prohibited from entering the discharge area when the mixer is operating.

5.5 Unauthorized personnel are prohibited from entering the control room, and smoking and activities unrelated to operation are prohibited. If there is no operator in the control room, the power must be cut off before leaving, and the doors and windows must be locked.