Analysis and treatment of common faults of the hot

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Cause analysis and treatment of common faults of extrusion granulation unit (II)

cause analysis and solutions of common faults

1. High torque of main motor

cause analysis: oil lubrication system fault, poor alignment of main motor output shaft and gearbox inlet and outlet shaft, motor and clutch vibration and other reasons will damage the main motor bearings, resulting in high torque. In addition, excessive feeding load or poor material melting will also lead to excessive torque of the main motor

solution: regularly check and clean the lubricating oil system, measure the main motor bearings with vibration measuring instrument and infrared thermometer, and form a trend chart. If the trend value is exceeded, measure whether the idle current value or power value of the main motor exceeds the specified value, and judge whether the bearing should be replaced. Regularly check the alignment between the output shaft of the main motor and the input shaft of the gearbox. The alignment must be checked three months after the first start-up or bearing replacement. Conduct electrical test and inspection to determine the cause of rotor imbalance; Test the vibration speed of the clutch. If it exceeds the specified value, readjust the dynamic balance. Regularly inspect the high-end special-shaped electronic copper strip produced by the cylinder heating and cooling system to ensure that the material is heated evenly and fused fully. If the power curve of the main motor and the melt pressure curve increase instantaneously at the start of the extruder, it indicates that the feeding volume of the feeding system is too large instantaneously, and the feeding volume should be reduced

2. The torque of the main motor is too low

cause analysis: the failure of the feeding system will lead to the idling of the twin-screw, which will lead to the low torque of the main motor

solution: check and judge whether the additive system or the main material blanking system is faulty, and clean up the blocking points

3. Friction clutch failure

cause analysis: the instantaneous starting voltage of the main motor is too low, the friction disc and friction plate are overheated, the friction disc and friction plate are aging, and the air pressure of the friction disc is too low, which can lead to clutch disengagement

solution: when starting the main motor, avoid the peak power consumption, reduce the feeding load, and the restart interval is at least 30 minutes; In summer, when the main motor is started repeatedly for more than two times, the interval should be extended or the fan should be used to forcibly cool down. These materials can usually form some kinds of keys. Purge with instrument air and wipe the dust on the surface of the friction plate and friction disc with a rag. If the wear is heavy or the surface appears "vitrification", replace the friction plate and friction disc. Confirm whether the air pressure value can make the friction disc fit the friction plate

4. Cause analysis of high melt pressure

high filtration mesh, low melt index of polypropylene powder and large feeding volume, incomplete melting of materials due to low barrel temperature in each section, and blocked extrusion of head materials due to low template opening rate can lead to high melt pressure

solution: when producing low melt index products, low mesh filtration should be used, and the opening of throttle valve should be increased to reduce back pressure; Change the filter in time, monitor the quality of various additives and the ash content in polypropylene powder. Reduce the feeding load. Without affecting the quality of extruded products, increase the barrel temperature of each section, increase the melt temperature of polypropylene, and increase the fluidity of materials. After the extruder stops and establishes the index database car, the waste is mostly collected in the situation of supply and demand docking meeting. After a period of high head temperature and constant temperature, the formwork is thoroughly washed and cleaned

5. Failure of underwater pelletizing system

cause analysis: excessive wear of the cutter or damage to the blade edge, low particle water flow, excessive vibration of the pelletizer, loose fitting between the cutter and the template, large fluctuations in the melt index of the material, inconsistent discharge flow rate, excessive high particle water temperature can lead to the shutdown of the underwater pelletizing system, resulting in the chain shutdown of the whole unit

solution: after parking, visually check whether the cutting edge of the cutter is excessively worn or damaged. If so, replace all the cutters. Check and confirm whether the particulate water is leaking, and whether the filter and cooler of the particulate water tank are blocked. If blocked, manually clean it up; Check whether the inlet and outlet pressure of the particle water pump is normal. If not, overhaul the particle water pump and the valves on the pump pipeline. Check whether the alignment between the cutter shaft and the pelletizing motor is out of tolerance, whether the bearing components of the cutter shaft are damaged, and whether the dynamic balance of the cutter rotor is unbalanced. During operation, check whether there is clearance between the four moving wheels of the pelletizing car and the guide rail. Control the volatile in polypropylene powder and eliminate the vibration of the cutter and cutter shaft when flowing through the template hole. Reduce the hot oil temperature at the formwork, check the temperature distribution of the cylinder and formwork, and check whether the flow, pressure and temperature of the cylinder cooling water are normal; Confirm the time setting of "water, knife and material" arriving at the formwork to prevent the particle water from arriving at the formwork too early and blocking the formwork hole. After the cutter closes the head, the feeding amount should be quickly raised to the set load of the extruder

if the above fault cause points can be combined with the logical relationship of interlocking to compile a fault diagnosis software, it can provide quick and intuitive reference and help for the operation, maintenance and management of the unit

Author: Kuang hejiangbo, organic synthesis plant of Dalian Petrochemical Company

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