Melt pumps and screen changers are used in plastic pipe extrusion

Melt pumps and screen changers are two critical components in plastic pipe extrusion production lines, playing a key role in enhancing production efficiency, product quality, and the stability of equipment operation. The following is a detailed introduction to their application and functions in plastic pipe extrusion production lines:

Function of the melt pump:

Stabilizing pressure and flow: The melt pump is located between the extruder and the die. Through its precise gear transmission mechanism, it provides stable and continuous material feeding. This helps eliminate pressure and flow fluctuations caused by variations in screw speed or material viscosity during the extrusion process, ensuring uniformity in pipe dimensions.

Increasing Extrusion Output: By establishing stable backpressure, the melt pump makes the material inside the extruder more compact, reducing material return and leakage, thereby enhancing the extruder's plasticizing and extrusion capacity and increasing output.

Reduced energy consumption: By optimizing the extrusion process and minimizing unnecessary energy loss, the melt pump helps reduce overall energy consumption of the production line.

Improved product quality: Stable melt conveyance reduces stress marks and surface defects on the inner walls of the pipes, enhancing their mechanical properties and surface quality.

Function of the screen changer:

Filtering impurities: Plastic melt may contain unmelted particles, gels, metal debris, and other impurities. The screen changer effectively intercepts these impurities through its internal filter mesh, preventing them from entering the mold and avoiding surface defects or internal flaws in the pipe.

Non-stop screen changing: Advanced screen changer designs allow for filter screen replacement without stopping the production line. This significantly reduces production downtime, improves production efficiency, and avoids material waste and equipment wear caused by shutdowns.

Equipment protection: By filtering out large particles, the screen changer protects downstream equipment (such as melt pumps and molds) from wear and blockages, extending equipment lifespan.

Improved product consistency: Consistent filtration ensures uniform quality across each batch of extruded tubes, meeting customer demands for high-quality products.

Synergistic operation in plastic pipe extrusion production lines:

Melt pumps and screen changers are typically used in series, with the screen changer positioned between the extruder and the melt pump. This configuration enables:

The screen changer first filters the melt from the extruder to remove impurities, ensuring the purity of the material entering the melt pump. The melt pump then stably delivers the filtered melt to the mold, ensuring uniform extrusion of the pipe.

Application example:

When producing high-density polyethylene (HDPE) pipes, impurities such as catalyst residues and low-molecular-weight polymers in the raw material may affect the pipe's pressure resistance and surface quality. By installing a screen changer, these impurities can be effectively filtered out, and combined with the stable delivery of the melt pump, the produced HDPE pipes exhibit excellent mechanical properties and a smooth surface.

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