I. General Provisions

1. These specifications apply to the operation and management of double-scale packaging machines (including electronic dual-scale automatic packaging scales) in fertilizer production workshops, covering the entire process of pre-production preparation, production operation, and maintenance.
2. Operators must pass training before taking up their posts. Before operation, they shall become familiar with the equipment structure and the contents of these specifications. Controllers and sensors are precision instruments and should avoid vibration and collision during transportation and use. It is strictly prohibited to operate them exposed to direct sunlight, near heat sources, in humid conditions, in poorly ventilated areas, or in strong magnetic fields. Drinking alcohol within eight hours before the shift and during the shift is strictly prohibited. Labor protection articles must be worn as required.
3. The double-scale packaging machine mainly consists of two independent weighing systems (including load cells and weighing hoppers), feeding devices (dual vibration feeding or dual screw/gravity feeding), bag clamping device, pneumatic system (including cylinders and solenoid valves), weighing display controller (indicator), PLC electrical control system, bag sewing and conveying equipment (optional), and frame. Through the dual-scale structure working alternately or cooperatively, continuous and efficient quantitative packaging is achieved. The dual-scale structure has alternating weighing capability and realizes continuous operation through two independent weighing systems. Material enters the weighing hopper from the storage silo through the vibration or screw feeding device (the weighing hopper is mounted on the sensor assembly). When the material reaches the preset weight, feeding stops, the bottom door of the weighing hopper opens, the material falls into the packaging bag, and after sealing by the bag sewing machine, it is sent out by the conveyor belt, thereby realizing automatic, continuous, and precise quantitative packaging.

II. Pre-Production Preparation Stage

2.1 Pre-Startup Inspection

1. Equipment integrity inspection: Check whether all parts are installed securely and whether fasteners are loose or fallen off. Check whether the scale body, conveyor belt, bag clamping device, and other parts are normal and undamaged. Check whether there is residual material in the weighing hopper; clean it promptly if present. Before restarting equipment that has been out of service for a long time (over 30 days), test the motor insulation with a megohmmeter.
2. Pneumatic system inspection: Start the control pressure reducing valve and adjust it to 0.5–0.6 MPa to ensure the working pressure of the actuators (cylinders). Check whether there is air leakage in the air circuit and whether the air pipes are damaged. Check whether the lubricating oil in the lubricator is sufficient; drain the sewage in the water separator filter completely.
3. Weighing system inspection: Check whether the appearance of the load cells is intact and whether the connecting cables are damaged, pulled, or loose. Check whether the terminals are tight, free of looseness and corrosion. Load cells must not be subjected to impact or overload. Check whether there is foreign matter contact between the limit device and the sensor.
4. Bag clamping device inspection: According to the size of the bag opening, adjust the bag clamping device screw rod, adjusting bolts, limit screws, and other parts, and adjust the positions of the left and right bag spreading rods to appropriate positions. Incorrect bag spreading rod positions will affect the bag clamping effect and deform the bag spreading rods. Check whether the bag clamping cylinder operates normally.
5. Electrical inspection: Power connections should be firm and reliable, insulation should be good, and grounding should be correct. The protective grounding and signal grounding of the electrical control system must be properly connected to the corresponding terminals; otherwise, weighing errors may occur and even the electrical control system may be damaged. The working voltage and frequency must meet the controller’s technical requirements. Do not share switches or circuit breakers with other equipment.
6. Parameter verification: Confirm whether parameters such as target weight, coarse feed value, fine feed value, and in-flight material value are set in accordance with the current material and packaging specifications.
7. No-load trial run: After confirming the hopper is empty, connect power and preheat for more than 15 minutes before operation. The main display weight should be 0; otherwise, manually unload and clear it to ensure accurate system zero. During the no-load trial run, check whether the action sequence of each cylinder is correct and whether there is jamming. Feed material only after confirming everything is correct.

2.2 Material Preparation

1. Confirm that the material to be packaged contains no hard foreign matter such as iron blocks, stones, or broken packaging, so as to avoid damaging the feeding device or affecting weighing accuracy. The material particle size is recommended to be ≤5 mm (powder materials require anti-blocking devices).
2. Check whether the material in the silo is sufficient to avoid insufficient or interrupted feeding.
3. According to the material flowability, bulk density, and required weighing, adjust the opening degree of the discharge gate to prevent the material flow from being too large during feeding, which would affect weighing accuracy.

III. During Production Operation

3.1 Startup Sequence

1. Turn on the power switch and check whether the power supply meets the rated value. Preheat the electrical control system for more than 15 minutes.
2. Open the air source valve and confirm that the compressed air pressure is 0.5–0.6 MPa.
3. Start the control system and set packaging parameters (target weight, fast feed amount, medium feed amount, slow feed amount, etc.) on the touch screen or indicator.
4. Turn the “Manual/Auto” switch to the “Manual” position and manually check whether each actuator operates normally. After confirming correctness, turn it to the “Auto” position and start the equipment.
5. After the bag clamping device automatically clamps the bag, the system automatically performs tare (taking the packaging bag weight as tare), and then enters the automatic feeding cycle.

3.2 Operation Monitoring

1. Weighing accuracy monitoring:
   • Closely observe whether the weighing display value is stable and whether there is abnormal fluctuation. If the packaging weight deviation is too large, stop immediately and inspect.
   • The in-flight material value (drop) is initially set to 0.5 kg. The system automatically corrects it each time during actual weighing to ensure weighing accuracy. After changing material or packaging specifications, the drop setting value must be reconfirmed.
   • The target weight error should be controlled within ±0.2% (for example, for 50 kg packaging, error ≤100 g).
2. Feeding process monitoring:
   • Set fast, medium, and slow three-stage feeding speeds according to material characteristics and packaging speed. The coarse feed amount is generally set to 90% of the required weighing. Increasing the coarse feed value can shorten feeding time, but if too large, it will affect feeding stability and thus affect the weighing accuracy of the whole machine.
   • Check whether the feeding device operates normally, without jamming or blockage.
   • If one feed already exceeds the weighing range, it indicates that the material flow is too large, and the opening degree of the dividing hopper gate should be adjusted.
3. Bag clamping and discharging monitoring:
   • Check whether the bag clamping device is clamped tightly to avoid material leaking from the bag opening.
   • In dual-scale interlock mode, scales A and B discharge alternately. It is necessary to confirm that the quantitative completion sequence of the two scales is normal and without conflict. If one scale is discharging, the other scale, even if its quantitative measurement is complete, must wait until the bag clamping signal is valid before discharging.
   • After discharging is completed, the conveyor belt promptly sends the material bag out.
4. Operation status monitoring:
   • Frequently check the coordination of cylinder actions, whether there is air leakage, and whether there is damage.
   • Pay attention to the temperature of the motor, cylinders, and other parts. If abnormal temperature rise occurs, stop immediately and inspect.
   • If abnormal noise, vibration, or other abnormal conditions are found, stop immediately and inspect.
5. Safety discipline:
   • When the equipment is running, no person is allowed to stand within the movement range of the left and right bag spreading rods to avoid accidental injury.
   • Parameter setting of the electrical control system is not allowed during equipment operation; otherwise, the entire work process will be disrupted.
   • Guards for transmission parts must always remain installed.
   • When replacing air pipe connection points, close the air source first.

3.3 Shutdown Operation

1. Normal shutdown: Confirm that the target bag count has been completed; the system automatically stops feeding.
   • After the current packaging cycle is completed, turn the “Manual/Auto” switch to the “Manual” position.
   • Turn off the control system power.
   • Close the air source valve.
   • Cut off the main power of the control cabinet and hang a “Stopped / Do Not Operate” warning sign.
2. Emergency shutdown (abnormal shutdown):
   • Immediately press the emergency stop button or cut off power to perform emergency shutdown.
   • Handling after emergency shutdown: The cause of the fault must be identified and eliminated before restarting according to the startup sequence. It is strictly prohibited to force startup before the fault is eliminated. At the same time, the emergency shutdown time, cause, and handling process should be recorded in detail in the Equipment Operation Record.
3. Post-shutdown on-site handling (mandatory):
   • Clean accumulated material on the weighing hopper, sensors, and other parts. Use a brush or compressed air for cleaning. It is strictly prohibited to wash with water.
   • Clean dust and residual material on the equipment surface.
   • Drain the sewage in the water separator filter completely.
   • Check the tightening condition of sensors, cylinders, motors, and other parts.
4. Shift-change shutdown requirements:
   • Before handover, the equipment must be stopped and cleaned, and the Equipment Operation Record and Shift Handover Record must be truthfully filled in, noting the equipment operation status during the shift (packaging quantity, weighing accuracy, abnormalities, and countermeasures).
   • Before startup, incoming shift personnel must re-confirm the equipment status against the inspection requirements in the “Pre-Production Preparation Stage.”

IV. Maintenance and Care

4.1 Daily Maintenance (Each Shift)

1. Cleaning: Use a brush or compressed air to clean accumulated material on the weighing hopper, sensors, conveyor belt, and other parts; clean the equipment surface.
2. Pneumatic system: Check the oil level of the lubricator and add lubricating oil as specified; drain the sewage in the water separator filter completely.
3. Weighing system: Check whether there is dust or foreign matter on sensors and junction boxes; confirm that the zero display is normal.
4. Bag clamping device: Check whether the bag clamping mechanism operates normally and whether there is looseness.
5. Inspection record: Record operating status, packaging quantity, accuracy deviation, etc.

4.2 Regular Maintenance

1. Lubrication maintenance cycle:
   • Regularly lubricate support rollers, thrust rollers, and transmission gears.
   • The injected lubricating oil must be clean, and seals must be good.
   • Note: For detailed lubrication guidance, see the equipment lubrication nameplate.
2. Weighing system maintenance:
   • Load cells must be calibrated every 6 months. Replace them when the error is >0.3%. Use standard weights to verify the accuracy of the weighing module.
   • Regularly check whether sensor connectors, junction boxes, level gauges, and electrical components used for control are damaged.
   • Check whether the gap between the limit device and the sensor is reasonable to avoid contact affecting accuracy.
3. Electrical system maintenance:
   • Do not open the control cabinet door arbitrarily to prevent dust from entering and affecting the normal operation of electrical components.
   • Check motor insulation performance every six months; inspect circuits to eliminate leakage and short-circuit hazards.
   • Check whether each terminal is loose.
4. Pneumatic system maintenance:
   • Regularly check the coordination of pneumatic components, whether there is air leakage, and whether there is damage.
   • Check the wear condition of cylinder piston seals and replace them when necessary.
   • Check whether solenoid valves operate normally.
5. Wearing parts inspection and replacement:
   • Sensors: calibrate every 6 months; replace when error exceeds the standard.
   • Establish spare parts inventory for seals, filter screens, etc., and replace them in time.
   • Replace the conveyor belt every 1–2 years according to wear condition.

4.3 Long-Term Shutdown Maintenance

When the equipment is out of service for more than 30 days, the following maintenance must be carried out:

• Thoroughly clean accumulated material on all parts of the machine using a brush or compressed air.
• Apply anti-rust oil to exposed parts of carbon steel components.
• Add lubricating oil to moving parts.
• Lock moving parts.
• Cover with plastic film to prevent dust and moisture.

Before restarting, test the motor insulation with a megohmmeter, trial run according to the no-load trial run requirements, recalibrate the weighing system with standard weights, and feed production only after confirming normal operation.

4.4 Fault Handling Principles

1. If weighing error exceeds the standard, abnormal noise, vibration, etc. are found, stop immediately; restart only after the cause is identified and the fault is eliminated.
2. It is strictly prohibited to run equipment with faults, and strictly prohibited to perform maintenance or cleaning while the equipment is running.
3. When repairing the weighing system or pneumatic components, cut off power, close the air source, and hang a “Do Not Close Switch” warning sign.

V. Common Faults and Remedies