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Pelletizing Systems: 7 Methods Compared

Seven pelletizing methods, and the wrong one costs more than the extruder difference: PVC needs air, PET needs water on the strand, high filler needs a die face, TPE needs underwater. A reference pelletizing systems page from Kerke.

Updated 6 November 2026

Scope Water Ring · Strand · Underwater · Air-Cooled

Delivery 30–45 working days

Voltage built for destination

Pelletizing systems — workshop photo 1, Kerke workshop, Nanjing

Pelletizing systems — workshop photo 2, Kerke workshop, Nanjing

Pelletizing systems — workshop photo 3, Kerke workshop, Nanjing

Pelletizing systems — workshop photo 4, Kerke workshop, Nanjing

Pelletizing systems — workshop photo 5, Kerke workshop, Nanjing

Pelletizing systems — workshop photo 6, Kerke workshop, Nanjing

Running video — Pelletizing systems, Kerke workshop

Quick answer

Seven pelletizing methods cover every product we sell: water-cooled strand, air-cooled strand, water-ring strand, water ring hot die-face, air-cooled hot die-face, underwater hot die-face and spray drying. The choice follows the material — PVC and HFFR must be air-cooled, TPE and hot melt must be underwater, filler masterbatch is normally water ring.

7 methodscompared in one page

0.5–8 mmpellet size

up to 4,000 kg/hcapacity

Workshop photos and a running video — shot on our own lines, not stock images.

Parameter table

**Table 1.** Pelletizing systems — models and reference output.
Method	Best for	Output range	Watch out
Water-cooled strand	Filler/colour masterbatch, engineering plastics	100–2,000 kg/h	Floor space, strand breakage at high filler
Air-cooled strand	PLA, starch blends, moisture-sensitive polymers	100–800 kg/h	Slow cooling, longer line
Water ring strand	PET, PA, high-temperature polymers	300–2,000 kg/h	Water temperature control
Water ring hot die-face	Filler/black masterbatch, PE/PP	200–2,000 kg/h	Die hole blockage at high filler
Air-cooled hot die-face	PVC, HFFR/LSZH, XLPE, WPC	100–1,500 kg/h	Air flow uniformity, dust
Underwater hot die-face	TPE/TPU, hot melt, EPP, compounds needing round pellets	200–2,000 kg/h	Water temperature and flow; die freeze-off on start-up
Spray drying	PET with high water carry-over, sticky products	300–1,500 kg/h	Energy cost

Reference output measured on the stated material family; subject to a material trial. Motor and torque values are per machine, not per screw shaft.

The three rules we use

If water causes hydrolysis, cool with air. PVC, HFFR, XLPE and WPC all fall here. Water cooling gives black specks or voids.
If the pellet must be round and free-flowing, go underwater. TPE, TPU, hot melt and EPP block in a bag when strand-cut.
If the melt is highly filled, prefer hot die-face. Strands break at 85% CaCO₃; cutting at the die avoids the problem entirely.

Capacity is set by the die, not the cutter

Die hole count and diameter determine output per revolution. A pelletizer rated "2,000 kg/h" with a 40-hole die cannot deliver that on a 3 mm pellet — check the die, not the label.

What this machine is normally bought for

Filler Masterbatch Extruder Line

Filler masterbatch is sold by the tonne, so the line is judged on two numbers only: how much powder it can swallow, an…

85–90% CaCO₃ at 350–550 kg/h

PVC Compounding Line

PVC is heat-sensitive and water-sensitive at the same time, which rules out both long residence time and water contact…

Why Air-Cooling Hot-Face Cutting

TPE / TPU / TPR Elastomer Line

Elastomer compounding is dominated by oil: SEBS takes 100–300 phr, and injecting it all at once makes the screw slip i…

Hardness 30–90A

PET Bottle Flake Recycling & Pelletizing Line

PET is judged on one number after pelletizing: intrinsic viscosity. Water and heat destroy it, so drying, low-shear sc…

Keep the IV

FAQ

Which pelletizing method should I choose?

Follow the polymer first: water-cooled strand below 50% filler and for PET; water ring at 70–85% filler; air-cooled hot face for PVC, HFFR and WPC; underwater for TPE/TPU and EPP beads.

What is the difference between water ring and underwater?

Water ring cuts at the die face with water sprayed at an angle, so pellets are cooled in a ring of water and leave with 8–12% moisture. Underwater cuts in a full water chamber at higher pressure and gives rounder, denser pellets — necessary for elastomers and bead products.

Can I change method later?

The pelletizer is a module. If the die and the discharge are designed for it, a strand line can become a water-ring line in two days.

Where these numbers come from

Screw diameters, speeds, motor ratings, torque and reference output come from the Kerke parameter table and the product master data sheet, and are cross-checked against commissioning records. Where a catalogue value and a trial value disagree, the trial value is the one we quote.

Reviewed by the Kerke process team, Nanjing. Page updated 6 November 2026.

Need a capacity number for your material?

Send 25–50 kg — we return pellets, a video and a report with the parameters we used, in 3–7 days.

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Pelletizing systems — the short version

Note on pelletizing systems: what separates one machine from another is torque class, L/D and the wear package matched to your material, not the build standard. Shortlist from the tables, then confirm the choice on a trial with your own powder.