Problems and Solutions When Starting a PE/PP Double Wall Corrugated Pipe Production Line

Starting equipment after installation or a long shutdown is one of the most important stages of production. This is especially true for a double wall corrugated pipe production line, because the quality of the finished pipe depends on several interconnected systems, including raw material feeding, extrusion, forming, vacuum calibration, cooling, pulling, and cutting.

A modern double wall corrugated pipe production line is usually equipped with one or two extruders, an extrusion die head, a corrugator, a vacuum system, a cooling system, a haul-off unit, and a cutting unit. If any of these components is improperly adjusted, problems such as unstable wall thickness, corrugation deformation, poor bonding between the inner and outer layers, or unstable production output may occur.

Below are the most common problems that may occur when starting a double wall corrugated pipe production line, together with practical solutions.

1. Why Can't the Extruder Reach Stable Production Output?

One of the most common problems when starting a PE/PP double wall corrugated pipe production line is unstable melt output. The output of the extruder may fluctuate, melt pressure may become unstable, and the pipe surface may become uneven.

Possible Causes

· Insufficient temperature in some zones of the extruder 

· Incorrect screw speed setting

· Unstable PE or PP raw material feeding

· Moisture or contamination in the raw material

· Incorrect extrusion die temperature

· Wear of the screw or barrel

Solution

Before starting the pipe production extruder, check all temperature zones and make sure that the actual temperatures correspond to the set values. Once the temperatures become stable, the raw material should be fed gradually.

It is not recommended to immediately set the screw to maximum speed. The extruder should initially operate at a low speed, after which the production output can be increased gradually.

2. Why Is the Outer Corrugation Deformed?

The outer wall is an important part of a double wall corrugated pipe. If the corrugation geometry is unstable, the finished pipe may fail to meet the required stiffness and dimensional specifications.

On a double wall corrugated pipe production line, this problem may be caused by incorrect synchronization between the extrusion system and the corrugator.

Main Causes

· Incorrect forming block speed

· Insufficient vacuum

· Incorrect melt temperature

· Insufficient cooling

· Incorrect position of the extrusion die head

· Mismatch between extruder speed and corrugator speed

Solutions

Check the vacuum system and make sure that the vacuum pressure remains stable. Then check the synchronization between the extruder, forming blocks, and haul-off unit.

If the melt temperature is too high, the corrugated wall may not retain its shape properly. If the temperature is too low, the material may not form correctly. Therefore, temperature adjustments should be made gradually.

3. Why Does the Smooth Inner Wall Have Uneven Areas?

One of the advantages of a double wall corrugated pipe production line is that it can produce pipes with a smooth inner surface and a corrugated outer wall.

If the inner surface has lines, uneven areas, or waviness, the internal flow channel of the extrusion die should be inspected.

Possible Causes

· Unstable melt feeding

· Incorrect die head temperature

· Contaminated filter

· Insufficient cooling

· Incorrect die head alignment

First, check the melt pressure and temperature profile of the extruder. The condition of the filter should also be checked, and the extrusion die should be cleaned if necessary.

4. Why Is the Bonding Between the Inner and Outer Walls Poor?

For PE/PP double wall corrugated pipes, reliable bonding between the inner and outer layers is extremely important.

If voids appear between the layers or the bonding strength is insufficient, the melt temperature and forming process should be checked.

Main Causes

· Insufficient material temperature

· Incorrect feeding ratio between the two layers

· Corrugator speed that is too high

· Incorrect extrusion die settings

· Insufficient forming pressure

In this situation, gradually increase the temperature of the relevant extruder zones, check the material feeding system, and ensure that the two extrusion flows are properly synchronized.

5. Why Is the Pipe Diameter Unstable?

Unstable pipe diameter is another common problem during the startup of a double wall corrugated pipe production line.

Main Causes

· Unstable extruder speed

· Incorrect vacuum setting

· Unstable haul-off speed

· Insufficient cooling

· Uneven raw material feeding

To solve this problem, check the relationship between extruder output, forming block speed, and haul-off speed.

These parameters must operate in synchronization to maintain stable pipe dimensions.

6. Why Does the PE/PP Pipe Surface Become Rough?

A rough pipe surface may occur when the temperature profile of the extruder is incorrect.

If the temperature is too low, the PE or PP material may not melt and mix completely, resulting in an uneven pipe surface.

However, an excessively high temperature is also undesirable because it may cause polymer degradation.

Therefore, when operating a double wall corrugated pipe extrusion line, a stable temperature profile should be maintained and operating parameters should be adjusted gradually.

7. Why Is Extruder Output Unstable?

If the output of the PE/PP pipe extruder fluctuates continuously, the raw material feeding system should be inspected.

Possible Causes

· Uneven pellet feeding

· Insufficient material in the hopper

· Unstable operation of the loader

· Incorrect screw speed

· Changes in bulk density of the raw material

For stable operation of the double wall corrugated pipe production line, it is recommended to maintain consistent raw material feeding and regularly inspect the automatic loading system.

8. Why Does the Pipe Stick to the Forming Blocks?

During the startup of a double wall corrugated pipe production line, material may sometimes stick to the forming blocks.

Possible Causes

· Melt temperature is too high

· Insufficient cooling

· Incorrect vacuum

· Contamination on the surface of the forming blocks

It is recommended to check the material temperature, cooling system, and vacuum system. The forming blocks should also be kept clean.

9. Why Does the Equipment Stop Frequently?

If the double wall corrugated pipe production line stops frequently during startup, both the electrical and mechanical systems should be inspected.

Particular attention should be paid to:

· Extruder motor

· Motor protection system

· Heating zones

· Temperature sensors

· Vacuum pump

· Water pump

· PLC control system

Alarm signals should not be ignored. Before restarting the equipment, the cause of the protection or alarm activation should be identified.

10. How Should the Production Line Be Properly Set Up Before Startup?

For stable operation of a double wall corrugated pipe production line, the following startup sequence is recommended:

Equipment Inspection → Raw Material Preparation → Preheating → Extruder Startup → Melt Stabilization → Forming Block Startup → Vacuum Forming → Cooling → Haul-Off → Cutting → Finished Pipe Inspection.

It is especially important not to increase the speed of the extruder too quickly. Once a stable melt is obtained, production output can be gradually increased to the required level.

Advantages of a Modern PE/PP Double Wall Corrugated Pipe Production Line

A modern double wall corrugated pipe production line offers several advantages:

· High production capacity

· Stable extrusion

· Precise temperature control

· Automatic operation

· Uniform wall thickness

· High ring stiffness

· Smooth inner surface

· Good corrosion resistance

· Long equipment service life

Such double wall corrugated pipe production lines are suitable for processing HDPE and PP and can be used to manufacture pipes with different diameters depending on the configuration of the equipment.

Conclusion

Proper startup of a PE/PP double wall corrugated pipe production line directly affects production stability and finished pipe quality. Most startup problems are related to incorrect settings of extruder temperature, screw speed, raw material feeding, vacuum, cooling, or synchronization of the forming equipment.

Before starting mass production, each component of the extrusion line should therefore be checked systematically, starting from the raw material feeding system and extruder, through the corrugator and cooling system, to the haul-off and cutting units.

A properly configured double wall corrugated pipe production line can consistently manufacture high-quality PE/PP pipes for drainage systems, sewage systems, cable protection, stormwater drainage, and other engineering applications.