Benefits of Twin-Screw Extruders for Pipe Production

Twin-screw extruders, also known as double screw extruders, are a core technology for processing certain polymers in pipe production. While single screw extruders are common for granular PO, double screw extruders are particularly well-suited for PVC, especially in dry blend form.

Key Advantages

The primary benefit of double screw extruders stems from their transport mechanism. Unlike single screws that rely on friction with the barrel, intermeshing double screws transport material in C-ring shaped chambers, providing a positive displacement independent of barrel friction. This results in a much higher pump efficiency compared to single screw extruders. This forced transport is particularly beneficial for dry blend PVC, which has more wall slip than PO. Using dry blend on single extruders is difficult due to friction dependence, whereas double screws handle it effectively.

Double screw extruders, especially those with self-wiping flights, offer process advantages for PVC. The self-wiping action reduces the need for high levels of heat stabilizer by minimizing material hang-up and degradation, contributing to cost savings. They provide a narrow spread in residence time, contributing to consistent processing. While single screw extruders may require a granulation step for PVC to improve reliability, double screw extruders process dry blend directly, saving this cost. Furthermore, modern twin-screw designs can require lower specific energy (Wh/kg) compared to older systems, and their increased output potential often allows replacing two older single lines with one modern twin-screw line. They also offer flexibility in design parameters like pitch and gaps to handle various dry blend types. The ability to incorporate features like early venting is also a significant advantage.

Technical Specifications (General Comparisons)

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