The main working mode of the PVC granulator is wet granulation. A certain amount of water or steam is used to make the basic fertilizer fully react chemically after being humidified in the cylinder. Under certain liquid phase conditions, the rotating motion of the cylinder is used to make the material particles produce extrusion force and agglomerate into balls.

Main features

The main advantage is that steam is used for heating and humidification, which increases the temperature of the granulation material itself, reduces the granulation moisture, reduces the load of the dryer, and improves the work efficiency. The granulation ball rate of the rotary drum granulator can reach 70%, and the equipment is simple to operate, has great working flexibility, and is easy to maintain. The equipment is lined with ultra-high molecular weight polyethylene (UHMW-PE), which eliminates the phenomenon of material sticking to the wall, reduces the labor intensity of workers, and greatly extends the service life of the equipment.

Product Introduction

200L high mixer-----500 type screw feeder-----twin screw metering feeder¡ª¡ªGLS-65 twin screw¡ª¡ªconnector¡ª¡ª¡ÓGLD-150 single screw extruder¡ª¡ªintegrated hydraulic plate type automatic screen changer¡ª¡ªair-cooled die face hot cutting granulation auxiliary machine¡ª¡ªfirst stage cyclone separator¡ª¡ªair-cooled vibrating screen (2.5m)----- Two-stage cyclone separator ---¡ª¡ªOne set of wind-blown silo;

Technical parameters

Output ¡Ü200-600Kg/h

One-time feeding amount.¡Ü120Kg/h

Total volume/effective volume.300L/150L

Spindle speed.380/735r.pm

Speed regulation mode.Variation

Heating mode.Self-friction

Material heating/hot mixing time is about 110¡æ/10min at room temperature

Discharge mode.Pneumatic

Discharge compressed air pressure.0.39~0.49MPa

Electric motor AC motor

Inner barrel material: stainless steel

Cover material: cast aluminum Z102

Discharge port material: cast aluminum Z102

Mixer material: stainless steel

Screw feeder: 500 screw feeder; hopper is made of stainless steel;

Upper stage

Reduction box

1) Reduction and torque distribution parts are integrated into one, with a compact structure;

2) Needle roller bearings, radial bearings of the bearing reduction torque distribution system;

3) Gears are made of high-quality alloy materials, and the precision is manufactured according to ISO1328-1995 cylindrical gear precision. All gears are carburized and quenched hardened tooth surfaces. Special gear grinding software is used to trim the gear profile to ensure gear strength, uniform tooth load, high strength, low noise and low vibration.

Screw

1) The screw has a building block structure;

2) The material of the mandrel is 40CrNiMoA, and the threaded element and the mandrel are involutely connected; high strength, large load bearing, and easy disassembly and assembly;

3) The material of the threaded element is high-quality high-speed tool steel W6MO5CR4V2, and it is heat treated by high-temperature vacuum quenching;

4) Overall hardness: HRC60-64;

5) The screw head and the cap are connected by reverse thread to ensure a tight connection.

Barrel

1) Material: 45# steel as base, high-quality double alloy bushing for inner hole;

2) The first section of the barrel is the feeding barrel, the sixth section is the natural exhaust barrel, the ninth section is the vacuum barrel, and the rest are closed barrels;

3) The barrel is cooled by soft water;

4) The barrels are connected by hexagonal high-strength bolts;

5) Heating section: the feeding zone is not heated, and the others are heated by high-quality cast aluminum heaters.

Lower stage machine

Reduction box: Adopt ZLYJ series high-precision hardened gear transmission device with thrust seat designed for single-screw rubber and plastic extruder. The design adopts various technical specifications stipulated in JB/T8853-2001 "Cylindrical Gear Reducer". The output shaft adopts high-strength 42CrMo, and other gears and shaft parts adopt high-strength 20CrMnTi materials; the gears are processed by carburizing, quenching and grinding, and the gears have high precision and hardness; the gear precision is GB10095-88, 6 level, the tooth surface hardness is HRC-54~62, and the thrust bearing is configured at the front end of the hollow output shaft to withstand the axial thrust of the screw when working. The whole machine has a small size, high load capacity, stable transmission, low noise and high efficiency. When the oil level is lower than the oil mark position, please add medium-load industrial gear oil L-CKC220 or L-CKC320 (the oil needs to be purchased by the customer).

Screw

1) The material is 38CrMoALA nitriding treatment, nitriding HV950-1050, depth 0.6-0.75mm, brittleness is not greater than Class II, and the surface of the screw is hard chrome plated;

2) The core of the screw is cooled by water

Barrel

1) The material is 38CrMoALA nitriding treatment, nitriding HV950-1050, depth 0.6-0.75mm, brittleness is not greater than Class II;

2) The barrel is cooled by water;

3) The barrel is grooved, copper pipes are coiled, and cooling water is passed;

4) A protective cover is added to the barrel, made of stainless steel;

5) Heating section: high-quality cast aluminum heater

6) The die head is heated by a mold temperature controller

4. Hot cutting auxiliary machine:

1) Air-cooled die surface hot cutting granulator: 4-level motor, one set of hot cutting knives, one motor coupling, hot cutting uses 4 blades for pelletizing

2) Speed control: frequency conversion speed regulation;

3) Pelletizing hood: blow-by type, stainless steel; one piece; push-pull structure; with brake device; there is enough space to separate the hot cutting hood from the die head; easy to operate; the blow-by type hot cutting hood is integrated with the bed

4) First-stage cyclone separator: ¦Õ800mm, stainless steel; one piece; connected with ¦Õ160mm stainless steel pipe;

5) Second-stage cyclone separator: ¦Õ800mm, stainless steel; one piece; connected with ¦Õ130mm stainless steel 6) Extended vibrating screen: one set, L=2.5m, motor: vibration-specific motor; vibration amount can be adjusted: motor power two sets; vibrating screen mesh uses three layers to separate materials; large hole diameter ¦Õ8mm, small hole diameter ¦Õ2.5mm, stainless steel, 7) Wind-blown silo: one set, 1m3 silo, stainless steel; connected with ¦Õ130mm stainless steel pipe; PVC cable material is a general term for cable materials made of polyvinyl chloride (PVC). As a traditional cable material, it still occupies the most important market share in the current Chinese market. Because its processing is relatively simple compared to other cable materials, and the amount used is relatively large.

Production process:

Raw materials are added with various additives in a certain proportion and in the order of process.-----200L high mixer-----500 type screw feeder-----twin screw metering feeder-----65 twin screw----connector----¡Ó-150 single screw extruder----integrated hydraulic plate type automatic screen changer----air-cooled die surface hot cutting granulation auxiliary machine----first-stage cyclone separator----air-cooled vibrating screen (2.5m)----second-stage cyclone separator------a set of wind-blown silos

Formula of PVC cable material

Formula of 70H-PVC cable material such as PVC type III 75PHR--Active calcium carbonate 35PHR---DOP (plasticizer) 25PHR---Epoxidized soybean oil soybean oil 3PHR --Chlorinated paraffin 20PHR--Stabilizer 2.8PHR--Stearic acid 0.6PHR --CPE 9PHR --- Paraffin wax 1PHR

(1) Preparation: Sieve the stabilizer, filler and colorant with a 80-mesh screen respectively, and add the plasticizer to soak them respectively, then grind them with a three-roll grinder or a colloid mill. Weigh them for use. After the plasticizer is mixed evenly, preheat it to 90¡æ for use;

(2) High-speed mixer: Add PVC resin, then add plasticizer and stir for a while. After the resin has basically absorbed the plasticizer, add stabilizer, and use friction heat to raise the material temperature to about 90¡æ. Then add filler and colorant. When the material temperature rises to 110¡æ, unload the material into the cooling mixer to cool it down. When it reaches below 45~50¡æ, discharge the material.

(3) Stable setting of PVC granulator:

1) Upper twin screw temperature setting: between 140 and 160 degrees; the temperature setting varies according to the material;

2) Lower single screw stable setting: between 125 and 145 degrees; the temperature setting varies according to the material;

3) After the actual temperature reaches the set temperature, keep warm for 40 minutes before starting production. This ensures that there is material left over from the previous day in the equipment, so that the material left over from the previous day can be softened, so as not to damage the equipment.

(4) Production:

1) After the high-mix PVC material is put into the hopper of the screw feeder, the powdered material is put into the upper parallel twin screw extruder through the screw feeder

2) The upper parallel twin screw extruder mixes the material evenly, and completes plasticization and mixing at a temperature of 140-160¡æ, and fully disperses it evenly. The final extruded mixture becomes a melt (temperature at 130-140¡æ), which falls directly into the large-diameter lower-stage single-screw extruder.

3) The lower-stage single-screw extruder extrudes the 120¡æ melt under low speed, high pressure and cooling conditions to complete extrusion granulation. The temperature has dropped to 120-140¡æ during extrusion. Only then can the air-cooled die surface hot granulation be completed, and it is guaranteed that the particles will not stick during the granulation process.

4) The particles cut off by the air-cooled die surface are cooled by the secondary air-cooled cyclone separator, and the particle temperature drops to 35-40¡æ. Then, they pass through the air-cooled extended vibrating screen to reduce the particle temperature to room temperature so that they can be sent to the finished product silo for packaging.

Scope of use

Cable material processing and granulation PVC processing and granulation PVC cable material processing and granulation

Precautions

1. The main motor and the oil pump motor are electrically interlocked, that is, the main motor cannot be started if the oil pump motor is not started; the oil pump motor cannot be stopped if the main motor is not stopped.

2. The main motor and the feeding motor are electrically interlocked, that is, the feeding motor cannot be started if the main motor is not started; the main motor cannot be stopped if the feeding motor and the main motor are not stopped.

3. The main motor control cabinet has overcurrent protection. In addition, it also has a mechanical protection device, which is generally a nylon shear pin type safety coupling. When the design torque is exceeded, the shear pin is cut off and the transmission box stops working.

4. When the head pressure exceeds the set alarm value, the material pressure alarm signal light is on and the machine stops automatically.

5. It is strictly forbidden to bring any metal debris into the raw materials produced by the user.

6. When the machine is running, it is strictly forbidden to use metal objects to clean the material at the opening of the cylinder.

7. Installation and disassembly of pressure sensors and material temperature thermocouples. When there is material in the head, it must be heated and the material can be installed and disassembled only after it is softened.

8. For the circulating water of the cylinder cooling system, please use softened water or distilled water.

9. The screw is only allowed to start at a low speed (¡Ü20r/min), and the idling time shall not exceed 2 minutes. After feeding, wait for the material to be discharged from the die hole of the die head before gradually increasing the speed.

Fault handling

Basic introduction

The extrusion granulation unit integrates mechanical, electrical and instrumentation, and has a high level of automation control. Therefore, in actual operation, there will be many difficult-to-diagnose faults, resulting in too long processing time, which will affect the normal operation of the entire polypropylene unit and greatly reduce the economic benefits of production. Combining the theoretical knowledge of the extrusion granulation production process and more than ten years of management experience in actual production operation, the author analyzed and judged the common causes of failures in the operation of the unit, and formulated corresponding solutions and treatment methods to ensure its long-term stable operation.

ZSK250 extrusion granulation unit in Dalian Petrochemical's 70,000 tons/year polypropylene unit

Cause of failure

In the extrusion granulation unit, the reasons that lead to the disengagement of the friction clutch and the interlocking shutdown of the unit during operation can be divided into four categories:

Main motor system failure

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 inlet and outlet temperatures of the main motor water-cooled cooler are too high;

6. The outlet flow of the main motor bearing lubricating oil pump is too low;

7. The outlet pressure of the main motor bearing lubricating oil pump is too low;

8. The water leakage of the main motor water-cooled cooler is too high, etc.

Transmission system failure

1. Gearbox shift lever position deviation;

2. The instrument air pressure of the friction clutch is too high;

3. The speed difference of the friction clutch is too large;

4. The outlet pressure of the gearbox lubricating oil pump is too low;

5. The outlet oil temperature of the gearbox lubricating oil pump is too high;

6. Internal failure of the friction clutch, etc.

Failure of the screw process section of the extrusion granulator

1. The melt pressure before and after the throttle valve is too high;

2. The melt pressure of the die head is too high;

3. The melt pressure difference before and after the screen changer is too large;

4. The start valve rotation failure, etc.

Underwater pelletizing system failure

1. The temperature of the pelletizing motor winding is too high;

2. The speed of the pelletizer is too low;

3. The torque of the pelletizer is too high;

4. The automatic switching failure of the pellet water bypass;

5. The pellet water pressure is too high or too low;

6. The pellet water flow is too low;

7. The clamping bolts of the pelletizer are not tightened;

8. The bypass water valve of the pelletizing chamber is not closed;

9. The hydraulic clamping pressure of the pelletizer is too low;

10. The pelletizing motor is faulty;

11. The axial feed pressure of the hydraulic cutter is too low, etc.

Among the above fault causes, the most frequent ones are: the main motor torque of the main motor system is too high or too low; the friction clutch failure of the transmission system; the high melt pressure of the screw process section system of the extrusion pelletizer; and the underwater pelletizer system failure. The following will analyze these common causes of failure in detail and give corresponding solutions.

Main motor torque is too high

Cause analysis:

Oil lubrication system failure, poor alignment between the main motor output shaft and the gearbox inlet and outlet shaft, motor and clutch vibration and other reasons will damage the main motor bearings, resulting in excessive torque. In addition, excessive feeding load or poor material melting will also cause the main motor torque to be too high.

Solution:

Regularly check and clean the lubricating oil system, measure the main motor bearings with a vibration meter and an infrared thermometer and form a trend chart. If the trend value is exceeded, determine whether the main motor idling 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. The alignment must be checked after the first start-up or after the bearing is replaced for three months. Perform electrical tests to determine the cause of rotor imbalance; perform vibration speed tests on the clutch. If it exceeds the specified value, the dynamic balance should be readjusted. Regularly check the barrel heating and cooling system to ensure that the material is heated evenly and melted fully. If the main motor power curve and melt pressure curve increase instantly when the extruder is started, it means that the feeding amount of the feeding system is too large instantly, and the feeding amount should be reduced.

The main motor torque is too low

Cause analysis:

The failure of the feeding system causes the twin screws to run idle, which will cause the main motor torque to be too low.

Solution:

Check and determine whether there is a fault in the additive system or the main material feeding system, and clean up the blockage point.

Friction clutch failure

Cause analysis:

The main motor instantaneous starting voltage is too low, the friction disc and friction plate are overheated, the friction disc and friction plate are aged, and the air pressure of the friction disc is too low, which can cause the clutch to disengage.

Solutions:

When starting the main motor, avoid peak power consumption, reduce the feeding load, and restart the interval for at least 30 minutes; in summer, when the main motor is started more than twice, the interval should be extended or a fan should be used to force cooling. Use instrument wind to blow 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", the friction plate and friction plate should be replaced. Confirm whether the air pressure value can make the friction plate fit the friction plate.

High melt pressure

Cause analysis:

The filter mesh is high, the polypropylene powder has a low melting index and a large feeding amount, the temperature of each section of the barrel is low so that the material is not completely melted, and the low opening rate of the template makes the extrusion of the head material blocked. These reasons can all lead to excessive melt pressure.

Solutions:

When producing low melt index products, use low mesh filters and increase the throttle valve opening to reduce back pressure; replace filters in a timely manner, monitor the quality of various additives and the ash content in polypropylene powder. Reduce the feed load. Under the condition of not affecting the quality of extruded products, increase the temperature of each section of the barrel to increase the temperature of the polypropylene melt and increase the fluidity of the material. After the extruder stops, increase the temperature of the die head and keep it constant for a period of time, then thoroughly rinse and clean the template.

Underwater pelletizing system failure

Cause analysis:

Excessive wear of the cutter or damage to the cutter edge, too low pellet water flow, excessive vibration of the pelletizer, loose fit between the cutter and the template, large fluctuations in the material melt index causing inconsistent discharge flow rates, and too high pellet water temperature can all cause the underwater pelletizing system to stop, resulting in the interlocking stop of the entire unit.

Solution:

After stopping, visually check whether the cutter edge is excessively worn or damaged. If so, all cutters should be replaced. Check and confirm whether the pellet water is leaking internally, whether the pellet water tank filter and cooler are blocked, and if blocked, they should be cleaned manually; check whether the inlet and outlet pressures of the pellet water pump are normal. If not, the pellet water pump and the valves on the pump pipeline should be repaired. Check whether the alignment between the cutter shaft and the pelletizing motor is out of tolerance, whether the bearing assembly of the cutter shaft is damaged, and whether the dynamic balance of the cutter rotor is unbalanced. During operation, check whether there is a gap between the four moving wheels of the pelletizer trolley and the guide rail. Control the volatile matter in the polypropylene powder and eliminate the vibration of the cutter and the cutter shaft when flowing through the template hole. Lower the hot oil temperature at the template, check the temperature distribution of the cylinder and the template, and whether the flow, pressure and temperature of the cylinder cooling water are normal; confirm the time setting of "water, knife, material" to reach the template to prevent the granular water from reaching the template too early and freezing the template holes. After the pelletizer closes the head, the feed amount should be quickly increased to the set load of the extruder.

If the above fault causes and the logical relationship of the interlocking can be combined and compiled into fault diagnosis software, it can provide quick and intuitive reference and help for the operation, maintenance and management of the unit.

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