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Analysis and Treatment of Common Malfunction of Granulator

In this paper, based on the theoretical knowledge of the production process of plastic granulation and the management experience of more than ten years of actual production operation, this paper analyzes and judges the common causes of the failure in the operation of the unit, and makes the corresponding solutions and treatment methods so as to ensure the long and stable operation of the unit.
The cause of the failure: in the waste plastic granulator, the rubbing clutch of the waste plastic granulator is removed in operation, and the reasons for the interlocking of the unit can be divided into four categories:
Main motor system fault: 1, the main motor torque is too high or too low; 2, the main motor speed is too low; 3, the main motor bearing temperature is too high; 4, the main motor winding temperature is too high; 5, the main motor water cooled cooler outlet temperature is too high; 6, the main motor bearing lubricating oil pump outlet flow is too low; 7, main motor bearings lubricating oil pump out of the main motor bearing The mouth pressure is too low; 8, the main motor water cooled cooler water leakage is too high.
Transmission system failure: 1, gear box shift lever position deviation; 2, friction clutch instrument wind pressure is too high; 3, friction clutch speed difference is too large; 4, gear box lubrication oil pump outlet pressure is too low; 5, gear box lubricating oil pump outlet oil temperature is too high; 6, friction clutch internal fault and so on.
The malfunction of the screw process section of the plastic granulator: 1, high melt pressure before and after the throttle valve; 2, high melt pressure of the head of the machine; 3, excessive melt pressure difference before and after the net exchanger; 4, the turning failure of the driving valve, etc.
Water-ring cutting system fault: 1, the temperature of the particle motor winding is too high; 2, the speed of the granulator is too low; 3, the torque of the granulator is too high; 4, the granular water bypass automatically switches the fault; 5, the pressure of granular water is too high or too low; 6, the flow of granular water is too low; 7,The clamping bolt of the granulator is not tight; 8, the pelleting chamber water valve is not closed; 9, the hydraulic clamping pressure of the granulator is too low; 10, the grain cutting motor fault; 11, the hydraulic cutter’s axial feed pressure is too low, and so on.
Among the reasons mentioned above, there are more frequent occurrence of the main motor in the main motor system: the main motor torque is too high or too low, the friction clutch failure of the transmission system, the high melt pressure of the screw process section of the plastic granulator and the failure of the water ring granulator system. The following common causes of failure will be analyzed in detail, and the corresponding solutions are given.


Common fault causes analysis and solutions:

High torque of main motor

Reason analysis: oil lubrication system failure, the main motor output shaft and the gear box exit shaft is bad, the motor and clutch vibration and other causes will damage the main motor bearing, resulting in high torque. In addition, excessive feed load or poor material fusion will result in excessive torque of the main motor.
The solution measures: check and clean the lubricating oil system regularly, measure the main motor bearing with the vibration measuring instrument and the infrared thermometer, and form the trend chart. If the trend value is exceeded, it is determined whether the main motor’s idle current value or power value exceeds the specified value to determine whether the bearing should be replaced. Regularly check the alignment between the main motor output shaft and the gearbox input shaft. After the first drive or replace the bearing, it must check the situation after three months running. Carry out electrical test to determine the cause of the rotor imbalance; test the vibration speed of the clutch; if it exceeds the specified value, the dynamic balance should be re adjusted. Regular inspection of the heating and cooling system of the cylinder ensures that the material is heated evenly and fully melted. If the power curve of the main motor and the pressure curve of the melt increase instantaneously at the moment of the extrusion machine, the feeding amount of the feeding system is too large at the moment, and the feed amount should be reduced.

Low torque of main motor

Cause analysis: feeding system failure makes the twin screw idling will cause the main motor torque is too low.
Solution: check whether there is any fault in the additive system or main material cutting system, and clean up the plugging point.

Friction clutch failure

Reason analysis: the main motor’s instantaneous starting voltage is too low, the friction disc, the friction plate overheated, the friction disc and the friction plate aging, the low air pressure of the friction disc can cause the clutch to disconnect.
The solution: when the main motor starts, the power peak should be avoided and the feed load should be reduced. The shortest interval time for restarting is 30 minutes. When the main motor is started over two times during the summer, the interval time or the cooling of the fan should be prolonged. The friction plate and the friction plate should be replaced if the wear is heavy or the surface is “vitrified” if the wear is heavy or the surface is “vitrified”. Confirm whether the air pressure value can make the friction disc fit with the friction piece.

High melt pressure

The reason is that the number of filter mesh is high, the melting index of polypropylene powder is low and the feed quantity is large. The melting of the material is not thorough at the low temperature of the barrel, and the low opening rate of the template makes the extrusion of the head of the machine lead to high melt pressure.
The solution: when producing low melting index products, the low visual filter should be used to increase the opening of the throttle valve to reduce the back pressure; to replace the filter net in time, to monitor the quality of all kinds of additives and to the ash content in the polypropylene powder. Reduce the load of feed. Without affecting the quality of extruded products, the temperature of each segment can be increased, the melt temperature of polypropylene will be increased, and the material fluidity will be increased. After the press is stopped, the temperature of the head is raised and the temperature is maintained for a period of time.

Water ring particle system failure

The cause analysis: the cutting tool wear is too much or the cutting edge is damaged, the particle water flow is too low, the vibration of the granulator is too large, the cutting knife and the template are not tight, and the high temperature of the particles can cause the underwater cutting system to stop.
Solution: after parking, visually check if the cutting edge is excessive or damaged, if necessary, replace the cutter. Check and confirm the leakage of granular water, whether the filter and cooler are blocked, if the plug should be cleaned manually; check the pressure of the inlet and exit of the particle pump is normal, if it is not normal, the valve of the particle pump and the line of the pump pipe should be overhauled. During operation, check whether there is a clearance between the contact between the four wheels and the guide rail of the pellet car. Control the volatiles in polypropylene powder and eliminate vibration of cutter and cutter shaft when flowing through the template hole. To reduce the temperature of hot oil at the template, check the temperature distribution of the cylinder and the template, the flow, pressure and temperature of the cooling water of the cylinder are normal, and the feed quantity should be quickly raised to the set load of the extruder after the cutting machine is on the head of the machine.

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