Home/Machines/Pelletizing systems/Water-Ring Strand Pelletizing (PET)

Pelletizing · Water-Ring Strand Pelletizing (PET)

Water-Ring Strand Pelletizing (PET): How Kerke Builds It

A flowing water ring or trough locks strand temperature for PET, PA and other high-temperature polymers — uniform cylinders with low dust and intrinsic viscosity preserved for bottle-grade PET.

Updated 11 November 2026

Scope PET · PA · high-temperature polymers

Output 300–2,000 kg/h

Pellet Cylinder, low dust

Water-Ring Strand Pelletizing (PET) — workshop photo 1, Kerke workshop, Nanjing

Water-Ring Strand Pelletizing (PET) — workshop photo 2, Kerke workshop, Nanjing

Water-Ring Strand Pelletizing (PET) — workshop photo 3, Kerke workshop, Nanjing

Water-Ring Strand Pelletizing (PET) — workshop photo 4, Kerke workshop, Nanjing

Water-Ring Strand Pelletizing (PET) — workshop photo 5, Kerke workshop, Nanjing

Water-Ring Strand Pelletizing (PET) — workshop photo 6, Kerke workshop, Nanjing

Quick answer

Water-ring strand pelletizing cools PET and PA strands in a temperature-controlled water ring or trough before dry cutting. The point is IV control: bottle-grade PET loses intrinsic viscosity if strands cool too slowly or sit in hot water. Flowing, thermostatted water plus immediate drying keeps IV loss inside the specification.

300–2,000 kg/hcapacity range

ΔIV ≤ 0.02typical IV loss

30 ± 3 °Cwater control band

≤0.1%pellet moisture

Workshop photos — shot on our own lines in Nanjing, not stock images.

How the water-ring strand pelletizing (pet) line works

Strands leave a PET-optimised die with a strand count matched to the output.
A thermostatted water ring/trough with strong flow quenches the strands within seconds.
Water temperature is held in a narrow band — usually 28–33 °C for bottle-grade PET.
Air knife and vacuum wiper strip surface water before the cutter.
Pellets are screened, and optionally crystallized and dried downstream to target moisture.

Where this method wins

This is the PET specialist: bottle flake and sheet-grade pelletizing where intrinsic viscosity must survive the pelletizing step, PA compounding at high output, and any high-temperature polymer where slow air cooling would leave strands semi-molten at the cutter. Where pellets must be perfectly round instead, that is underwater pelletizing — different machine.

Reference data

**Table 1.** Water-Ring Strand Pelletizing (PET) — reference selection data.
Item	Value
Best for	PET bottle flake/sheet, PA, high-temperature polymers
Output range	300–2,000 kg/h
Pellet shape	Cylinder, low dust, IV-critical
Watch out	Water temperature control, IV loss on start-up

Reference output measured on the stated material family; subject to a material trial. Die hole count sets the capacity ceiling — check the die, not the label.

Selection notes from our floor

The two numbers that decide PET quality are water temperature and residence time. We commission the ring at 30 °C with flow tuned so strands are below 60 °C before the cutter. On start-up, dump the first strands — the IV loss is concentrated in the transition material.

FAQ

How much IV is lost in pelletizing?

On a tuned line, 0.01–0.02 dL/g from pelletizing alone. The bigger losses happen upstream in devolatilization if vacuum or residence time is wrong — that is where we look first.

Can this line take bottle flake with labels?

Flake should be pre-washed. Label fragments blind the die and break strands; the strand line tolerates far less contamination than a hot-face pelletizer.

Water ring or underwater for PET?

Strand for sheet and bottle grades where cylinder pellets are accepted and IV matters most; underwater when the customer needs round, dust-free pellets for spinning or foaming grades.

Where these numbers come from

Output ranges, pellet shapes and watch-outs come from Kerke commissioning records and the pelletizing systems parameter table. 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 11 November 2026.

Not sure which pelletizing method fits your material?

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

Get a quote Send material for trial

Water-Ring Strand Pelletizing (PET) — the short version

For PET and other IV-sensitive polyesters, the water-ring line cuts strands hot against a rotating ring and quenches them in seconds, holding intrinsic-viscosity loss to a minimum without a separate crystallizer step.