HDPE Water Supply Pipe Production Problems Analysis and Solutions

Date:2022-12-22 Author:hcscrew

The high density polyethylene HDPE water supply pipe is a popular plastic pipe product. PE80 and PE100 are the main raw materials used in HDPE pipe production. It’s inevitable that HDPE (PE80, PE100) water supply pipes will have problems and defects due to raw material selection, formulation, technology, equipment, and moulds. Some problems with pipe extrusion aren’t related to the screw and barrel. HUACHEN Screw has compiled a list of common HDPE pipe extrusion production problems in order to help producers fix them. It’s based on years of experience maintaining HDPE pipe extruders. Let’s start with the factors affecting extrusion and develop a solution process that makes sense.

HDPE pipe extrusion quality problem analysis and solution

1. HDPE pipe surfaces are rough

Causes: 1. Too much moisture in the material; 2. Low material temperature; 3. an unclean die or mould; 4. Extrusion speed is too fast.

Solution: 1. Increase the dryer temperature to dry the material; 2. Adjust the process temperature; 3. Clean the die; 4. Adjust the extrusion speed.

2. HDPE pipe surface has shiny patches

Cause: 1. High die temperature; 2. Insufficient cooling

Solution: 1. Lower the die temperature; 2. Increase the cooling.

3. A regular pattern on the HDPE pipe’s surface

Causes: 1. Adhesion between the material and the sizing sleeve.

Solution: Increase the amount of water curtain at the inlet of the sizing sleeve.

4. HDPE pipe has an uneven surface

Cause: 1. There are pulsations in the flow of HDPE material; 2. Traction speed is unstable.

Solution: 1. adjust the extrusion screw speed; 2. Fix the traction speed controller.

5. Pipes with uneven wall thickness

Causes: 1. The die and mandrel aren’t aligned; 2. Uneven temperature around the die; 3. Traction deviating from the extruder axis.

Solution: 1. Align the die with the mandrel; 2. Check and repair the electric heating ring. 3. Adjust the position of the tractor.

6. HDPE pipe is not round

Causes: 1. low vacuum level; 2. too fast extrusion speed; 3. insufficient cooling before traction; 4. high water levels in the cooling water tank.

Solution: 1. adjust the vacuum level; 2. Modify the extrusion and traction speed; 3. modify the cooling water and temperature; 4. lower the water level in the cooling water tank.

7. There is an axial variation in pipe diameter

Causes: 1. Extrusion that’s unstable; 2. The traction is unstable.

Solution: 1. Adjust the extrusion speed; 2. Adjust the haul-off speed or clamping force.

8. The pipe has impurities

Causes: 1. Broken filter; 2. The plastic is degrading; 3. Poor quality filler or colouring masterbatch.

Solution: 1. Replace the filter; 2. The process temperature needs to be adjusted; 3. Replace the filler or colouring masterbatch.

9. The HDPE pipe gets bent

Cause: 1. Pipe wall thickness is uneven; 2. The pipes aren’t cooling evenly; 3. The pipe was not cooled enough.

Solution: 1. adjust the wall thickness of the pipe. 2. Fine-tune the cooling water nozzle. 3. Lower the extrusion speed or adjust the cooling water volume and temperature.

10. Material appears combined

Causes: 1. There’s not enough length on the die; 2. Melting temperature is too low; 3. It’s not the right structure for the extruder head.

Solution: 1. Increase the length of the die; 2. Turn up the process temperature; 3. Pick a good head structure.

11. HDPE Pipe surface ripples

Causes: 1. Cooling isn’t good enough; 2. The sealing ring is too small, causing vibrations.

Solution: Increase the sizing sleeve’s water intake, or increase the distance between the mouth mould and the sizing sleeve. If the vacuum groove seal ring is small, replace it or reduce the first section vacuum groove vacuum, and raise the second section vacuum groove vacuum.

12. Pipe surface pockmarks (mainly on the inner wall)

Reason: 1. HDPE raw material has impurities; 2. The inner wall between the mouth mould and the core mould isn’t clean; 3. There’s too much heat in the area, which ages stuff.

Solution: 1. Make sure the raw material is high-quality; 2. Cleaning up or transitioning for a while; 3. Make sure the temperature sensor is working.

13. Craters on the HDPE pipe surface

Causes: 1. Tide of raw materials; 2. There’s an uneven amount of water in the sizing set.

Solution: 1. Make sure the raw material is dry; 2. Replace the sizing sleeves or adjust the water volume.

14. HDPE pipe surface bright spots

Reason: Too little water in the sizing sleeve.

Solution: Fill the sizing sleeve with more water or replace it with a bigger one.

15. Pipe inner and outer wall axial roughness

Reason: High water content of raw materials.

Solution: Dry the raw material.

16. HDPE pipe surface is not bright

Reason: The melt temperature isn’t right or the raw material isn’t good.

Solution: Adjust the melt temperature or replace the raw material.

17. HDPE pipe surface scratches

Reason: Sand and stones are attached to the sizing sleeve, support plate, or sealing ring.

Solution: Clean the sizing sleeve, support plate, or sealing ring.

18. Pipe outer surface with water lines

Cause: The sizing sleeve is partially blocked by the water eye, causing excessive water volume.

Solution: Clean up the sizing sleeve.

19. Pipe with grooves on the inner wall (mostly in thick solid wall HDPE pipe)

Cause: Too thick walls make the melt hard to cool, resulting in grooves on the inner wall.

Solution: Cool the mouth and core moulds with a central cooling system.

20. Pipe with uneven wall thickness

Causes: 1. There are loose bolts in the mouth or core mould, or the gap between the moulds isn’t adjusted correctly; 2. An uneven temperature in the mouth or core of the mould results in inconsistent material flow; 3. The sizing sleeve isn’t aligned with the mouth mould, the spiral diverter shuttle or screen is blocked.

Solution: 1. Tighten the bolts or adjust the gap between the mouth moulds; 2. Make sure the heating ring and temperature sensor are working; 3. Center the diverter shuttle or screen with the sizing sleeve and mouth mould.

21. Pipe with low break elongation

Reason: 1. Raw HDPE material does not plasticize well; 2. orientation increases, and cleanliness increases.

Solution: 1. Boost the plasticizing effect by adjusting the process temperature; 2. Make the mouth mold and sizing sleeve farther apart.

22. Pipe has a big ellipticity

Cause: The gravity effect

Solution: Get a correction device.

Summary

In order to improve the quality of high-density polyethylene pipe (PE80, PE100), the requirements and use of products must be strictly adhered to, the choice of raw and auxiliary materials is determined by the selection of suitable molding equipment, and the control process must be effective and accurate in a timely manner to eliminate temporary defects.

About the screw barrel Factory: HUACHEN

HUACHEN Screw has been a leading HDPE screw barrel manufacturer in Zhoushan Jintang since 1993. As one of the leading companies in designing and processing twin screw barrels, high speed extruder screw barrel, HUACHEN Screw can provide its customers with a wide range of services, including drawing rebuilding, design, modification, and customized screw barrels. Our company has also successfully exported and supplied screw barrels to customers worldwide.

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