Choosing a Screw Barrel for PVC Pipe Extrusion

PVC3 Oct 2026·6 min read

PVC degrades if you shear it too hard and it carries calcium carbonate that wears the bore. Getting both right on a PVC pipe line comes down to a few specific decisions before you buy.

Conical or parallel twin

PVC pipe is dominated by counter-rotating conical twins, typically 51/105 up to 110/220 for large diameter pipe. The taper gives a large feed area and a small discharge end, which suits a heat-sensitive material. Parallel twins appear more in compounding than in pipe.

Keep shear gentle

PVC needs a low compression ratio and a smooth, short compression zone. The screw should plasticate without hot spots: once the material starts to degrade locally, the whole pipe discolours and the problem looks like a formulation issue rather than a hardware one.

Specify the alloy for your filler loading

• Low CaCO3, virgin resin → nitrided screws with hardened flights are often enough
• Standard pipe formulations with filler → bimetallic bores, 2–3 mm alloy layer
• High filler or regrind, or foamed-core pipe → 3–5 mm layer and a hardened flight design

Venting and output

If you run regrind or recycled PVC, a vented barrel removes moisture and volatiles before the metering zone. Output targets should be quoted against your die; we size the metering depth to the head pressure you actually run, not to a catalogue figure.

What to send for a quotation

Machine model, screw diameter and conical size (for example 65/132), pipe range, filler percentage and whether you use regrind. A photo of the nameplate plus the old parts is enough if there is no drawing.

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