Operation and precautions of underwater pelletizing system

Underwater pelletizing system is the most widely used particle granulation system at present. It is mainly composed of drive valve, die head, pelletizer head, water circulation system and pipe fittings, dehydration and drying system, vibration filtration system and control system.

When uniform high-temperature molten materials enter the die head flow channel from the end of upstream equipment (reactor, screw extruder, mixing equipment, etc.), the materials are cut into droplets at high temperature. The cutter blade rotates at high speed, and the material enters the treated water when it just leaves the die hole. Droplets solidify and form particles close to spheres. This granulation method of “hot cutting before water cooling” determines that it can well adapt to the granulation of materials with poor melt strength, high viscosity and high heat sensitivity.

Underwater pelletizer is mainly used for filling, mixing, processing, adding of rubber and engineering resin, vinyl chloride, polypropylene and super absorbent resin; It can be used for degradation masterbatch, polyamide, polyurethane and polycondensation reactive extrusion.

How to operate the underwater pelletizer is a problem that many users are concerned about. The following are the operation sequence of the underwater pelletizer and the problems that may be faced.

Startup sequence:

1. Warm up: turn on the power supply, set the temperature of the pelletizer die head and the start-up valve according to the process requirements, and set the temperature of each section of the extruder at the same time;
2. Connect and open the air source, and adjust the working air pressure range;
3. After the temperature reaches the set value, continue to keep it warm for 15~30 minutes;
4. Open the extruder to discharge when the startup valve is closed, check whether the discharge is qualified, and adjust the extrusion process to be qualified;
5. Turn the manual and automatic transfer button to the manual position, turn on the hydraulic pump, and then turn on the start valve discharge state to make the die mouth full, and then close the start valve to clean up the water chamber and die mouth materials;
6. After cleaning the die mouth, push up the pelletizer and lock the connection with clamp;
7. Turn the manual and automatic transfer button to the automatic position, and press the pelletizer ON button on the screen. Other devices of the underwater pelletizer will start automatically;
8. Adjust various process parameters on the touch screen to make the discharged products meet the expected requirements and enter normal production.

Shutdown sequence:

1. LDPE washing machine for extruder, including washing underwater pelletizer, and closing the extruder after extruding;
2. When the pelletizer is shut down, the equipment will automatically interlock and shut down other systems;
3. Clean the residue on the die head and dredge all die holes;
4. Clean the interior of the centrifugal dehydrator;
5. Turn off the compressed air source;
6. Turn off the power supply of the control cabinet;
7. Site clearing

Points for attention:

1. The pelletizer and die head shall be separated during preheating;
2. According to the production requirements, the water quality in the water tank shall be checked regularly to ensure that it is clean.