1、 Operating standards: Ensure mixing quality and equipment lifespan

1. Feeding sequence and proportion control
   • Correct orderFirst, add starch raw materials (such as sweet potato starch and potato starch), then slowly pour in warm water (the water temperature needs to be adjusted according to the type of starch, such as sweet potato starch requiring 60-70 ℃ warm water), and finally add additives (such as alum and salt).
   • riskIf water is added first and then starch is added, it can easily lead to starch clumping; Additives that come into direct contact with high-temperature components may fail.
   • caseDue to an incorrect feeding sequence in a certain noodle factory, starch clumped in the mixer, blocking the discharge port. The repair took 4 hours.
2. Mixing time and speed setting
   • time control：
     • Pre mixing stage (low speed): 2-3 minutes to allow initial mixing of starch and water, avoiding dust flying.
     • Formal mixing stage (high speed): 8-15 minutes (adjusted according to the amount of starch), ensuring that the starch is fully gelatinized (gelatinization temperature needs to reach 75-85 ℃).
   • speed matching：
     • When stirring dry powder, the speed should be ≤ 100rpm to prevent dust diffusion;
     • During the gelatinization stage, the rotational speed is increased to 200-300rpm to enhance shear force and promote the fragmentation and recombination of starch molecules.
   • riskInsufficient mixing can lead to uneven starch gelatinization and easy breakage of vermicelli; Excessive stirring may damage the starch structure and reduce the toughness of the vermicelli.
3. Temperature monitoring and regulation
   • key points：
     • Temperature sensors should be installed on the inner wall of the mixing tank to monitor the gelatinization temperature in real-time;
     • If the temperature is too low (<70 ℃), steam heating or electric heating devices need to be turned on; If the temperature is too high (>90 ℃), it is necessary to start the cooling water circulation to cool down.
   • riskOut of control temperature may cause starch to become burnt (producing harmful substances such as acrylamide) or insufficiently gelatinized (causing the noodles to become brittle).

2、 Safety protection: prevent mechanical injuries and electrical accidents

1. Inspection of protective devices
   • Daily inspection items：
     • Is the locking device of the mixer cover sensitive (such as hydraulic lock, mechanical buckle) to prevent accidental opening of the cover during operation;
     • Is the protective cover of the transmission shaft intact to prevent personnel from coming into contact with rotating parts;
     • Can the emergency stop button (E-Stop) be triggered normally (the equipment should stop within 3 seconds after being pressed).
   • riskFailure of protective devices may cause operators to be caught in the mixing blade, resulting in limb injuries.
2. Electrical safety regulations
   • grounding protection：
     • The equipment casing must be reliably grounded (grounding resistance ≤ 4 Ω), and tested with a multimeter before use;
     • The power cord should use rubber cables that are resistant to high temperatures and oil stains (such as YC type) to avoid aging and damage.
   • earth leakage protection：
     • The distribution box needs to be equipped with a leakage protector (operating current ≤ 30mA, operating time ≤ 0.1s), and the sensitivity should be tested once a month.
   • riskElectrical faults may cause electric shock or fire (such as electrostatic discharge of starch dust).
3. Dust prevention and control measures
   • explosion-proof design：
     • The mixer must comply with ATEX explosion-proof standards (such as Ex d IIB T4), use non sparking motors and anti-static materials;
     • The feeding port needs to be equipped with a negative pressure suction device (air volume ≥ 500m ³/h) to control the dust concentration below 25% of the lower explosive limit (LEL).
   • riskThe explosion limit of starch dust is 45-200g/m ³, which may cause an explosion when exposed to open flames or high temperature surfaces.

3、 Cleaning and maintenance: avoid cross contamination and equipment jamming

1. Daily cleaning process
   • step：
     1. Immediately rinse the inner wall of the mixing tank with a high-pressure water gun (pressure ≤ 0.5MPa) after shutdown to remove residual starch paste;
     2. Use a soft bristled brush to clean the clumps in the gaps of the mixing blade (avoid scratching the surface with a metal brush);
     3. Wipe the control panel and sensors with 75% alcohol to prevent bacterial growth.
   • riskStarch residue can easily breed mold (such as aflatoxin), affecting the safety of vermicelli food.
2. Lubrication and maintenance cycle
   • Transmission components：
     • Replace the gearbox lubricating oil (such as Mobil SHC 634) every 500 hours and clean the oil filter;
     • Add lithium based grease (such as NLGI No.2) to the stirring shaft bearings every 200 hours to prevent wear.
   • Seal inspection：
     • Check the shaft seal (such as mechanical seal or skeleton oil seal) for leaks every quarter, and replace the seal if there is a leak.
   • riskInsufficient lubrication may cause overheating and jamming of transmission components, and even lead to fires.
3. Calibration of key components
   • Mixing blade balance calibration：
     • Every six months, use a dynamic balance meter to check the mixing blade (allowable unbalance ≤ 0.5g · m), and adjust the counterweight if it exceeds the tolerance;
     • Unbalanced operation can lead to increased equipment vibration and shortened bearing life.
   • sensor calibration：
     • Calibrate the temperature sensor annually with a standard thermometer (such as a platinum resistance thermometer, with an accuracy of ± 0.1 ℃), and the error should be ≤ ± 1 ℃.
   • riskSensor deviation may lead to uncontrolled gelatinization temperature, affecting the quality of vermicelli.

4、 Fault handling: rapid response and preventive maintenance

1. Common faults and solutions

   Fault phenomenon	Possible reasons	Processing Steps
   The stirring blade does not rotate	Motor overload, drive belt breakage	Check the motor current (1.1-1.5 times the rated current is overload), replace the drive belt (the model needs to be matched)
   large temperature fluctuations	Heating tube aging, temperature controller malfunction	Use a multimeter to check the resistance of the heating tube (e.g. 3kW heating tube resistance is about 16 Ω), replace the temperature controller (PID parameters need to be recalibrated)
   出料口堵塞	Excessive starch gelatinization and stuck discharge valve	Reduce the mixing temperature/time, disassemble the discharge valve for cleaning (hot water soaking can be used to soften clumps)
   Abnormal vibration of equipment	Unbalanced mixing blade and loose foundation	Re calibrate the dynamic balance of the mixing blade and tighten the foundation bolts (torque must meet the requirements of the equipment manual)

2. Preventive Maintenance Plan

   • Monthly maintenanceCheck the tension of the drive belt (measured with a tension meter, allowable deviation ± 5%), clean the dust on the motor cooling fan;
   • Quarterly maintenanceReplace the filter element of the reducer respirator (to prevent moisture from entering), check the insulation resistance of the electrical circuit (≥ 1M Ω);
   • annual maintenanceOverhaul the mixer (disassemble and clean all components, replace vulnerable parts such as seals and bearings).
   • riskLack of preventive maintenance may lead to sudden failures, resulting in production line downtime losses (such as daily downtime losses reaching tens of thousands of yuan).