Underwater Pelletizing System
The USEON underwater pelletizing system is engineered for elastomers, high-viscosity melts, micro-pelleting and high-throughput compounding. Melt distribution, die-face thermal management and automated drying are integrated into one system, supplied with a complete production line or as a standalone unit.
Diverter valve, pelletizer, water circulation and centrifugal dryer
- Pellet diameter, depending on the material
- 0.8–4.0mm
- Output, UWP300 to UWP4000
- 50–8,000kg/h
- Surface moisture targeted after the dryer, most standard polymers
- < 0.1%
When to choose underwater pelletizing
Each pelletizing method has preferred applications. Selection typically depends on material rheology, target pellet size and line layout.
- Pellet meets water
- Yes
- Pellet shape
- Near-spherical
- Typical materials
- Soft and sticky elastomers, micro-pellets, XLPE, high throughput
Underwater
Automated start-up, 0.8–4.0 mm
Automated startup sequences and reduced manual dependency. Highly uniform near-spherical pellets. Soft elastomers, high viscosity, micro-pellets.
Water ring
Semi-automatic, 2.5–4.0 mm
Standard polyolefins (PE / PP). Lens-shaped pellets.
Water RingStrand
Operator monitoring, 2.0–4.0 mm
Rigid engineering plastics and reinforced compounds. Cylindrical pellets.
Water Cooling StrandApplications and engineering practice
POE, TPU, EPDM, SAN
For lower hardness (Shore A 40 range) or elevated feeding temperatures (around 80 °C), instant water quenching inhibits pellet deformation and agglomeration. Also TPE, TPV, EVA, SBS, SIS and hot melt adhesives.
Pellets of 1.0 mm and below
Micro-pellets and oligomers place stringent demands on die-face pressure balance and cutter stability. Lines delivered for 0.8 mm spherical PS pellets; also PE, PA and functional masterbatch.
XLPE, MAH grafting, reinforced
The enclosed process manages dust generation and strand breakage. Wear-resistant configurations for XLPE cable compounds, 80% CaCO₃ high-filler and glass fibre reinforced PA.
PLA, PBAT, PS / PET foaming
Enclosed water loops and precise thermal logic minimize thermal degradation. Temperature control within ±1 °C in selected configurations. Also starch-based alloys.
High-throughput lines
Automated PP / EPS industrial recycling lines with throughputs reaching 3,000 kg/h. The system architecture has the engineering foundation to scale up to 35–50 t/h.
Related projects
ProjectTPU / rubber lumps1,000 kg/h ProjectPS micro-pellets30 kg/h ProjectPeroxide XLPE for 35 kV cable1,500 kg/h ProjectGraphite EPS1,500 kg/h ProjectPP recycling, India1,500 kg/h
The system
Overview
Diverter, die plate, cutting chamber, drive
Knives cut the melt at the die face under water, and the water carries the pellets to the dryer.
- Multi-zone thermal management and a rapid-start diverter valve keep the die face in thermal balance during startup
- One button start / stop
- Standalone units are matched to the flange interface, throughput and floor layout of an existing extruder
Diverter
Sends the melt to the discharge position or to the working position.
- Discharge position
- Working position
- Hydraulic driving
Pelletizer
With the hydraulic station, the knife pressure is set on the touch screen and the system regrinds the knives automatically by the set time and pressure.
- Die plate heatingelectrical heater or oil
- Two types of knifebevel and vertical, by material
- Knife pressuremanual or hydraulic
- Online polish for the knives
- Knife length indication
Module 3
Dewatering and water circulation
- Water tank with heater, water level control and temperature control
- Filter with rotating belt and servo motor, which discharges the powder automatically
- Dewatering system with an extra fan for removing moisture
- Cooling pipe with water flow control, indicated on the touch screen
- Heat exchanger that is easy to clean
- A pneumatic valve controls the outside cooling water flow, interlocked with the water temperature in the tank
- 01FeedingVolumetric or loss-in-weight
- 02ExtruderTwin, triple, tandem or single screw
- 03Melt filtrationScreen changer, melt pump
- 04PelletizingSix methods
- 05Dewatering and classifyingDryer, vibrating classifier
- 06Conveying and storageBlower, silo
- 07PackingBags or jumbo bags
Control system: one recipe and one start and stop sequence for all stationsControl system
Specification of the underwater pelletizer
UWP sizes for compounding lines; UPD sizes for petrochemical-scale lines.
| Model | Diverter | Hole No. | Knife No. | Knife moving | Water system | Output |
|---|---|---|---|---|---|---|
| UWP300 | D30 | 8–10 | 4–6 | Manually | W300 | 50–300kg/h |
| UWP500 | D40 | 20–30 | 6–8 | Manually | W500 | 200–700kg/h |
| UWP1000 | D50 | 40–80 | 8–12 | Hydraulic | W1000 | 2 t/h |
| UWP2000 | D60 | 100–160 | 10–16 | Hydraulic | W2000 | 2–6 t/h |
| UWP4000 | D60 | 100–160 | 12–18 | Hydraulic | W2000 | 3–8 t/h |
| UPD250 | D70 | 700–1000 | 16–22 | Hydraulic | PCW250 | 10–20 t/h |
| UPD300 | D120 | 1000–2000 | 16–24 | Hydraulic | PCW300 | 20–35 t/h |
| UPD400 | D160 | 2000–3000 | 20–40 | Hydraulic | PCW400 | 35–50 t/h |
Pellet diameter 0.8–4.0 mm, depending on the material.
UWP500
Micro-pellets
SAT110FAQ
When should I choose underwater pelletizing instead of strand pelletizing?
Underwater pelletizing is a strong option for production lines requiring high automation and reduced manual intervention. It is particularly suitable for soft, sticky, or heat-sensitive materials, or when producing micro-pellets.
How do you prevent "die freezing" during startup?
We utilize multi-zone thermal management combined with a rapid-start diverter valve. This helps maintain sufficient thermal balance at the die face even when melt flow velocity is low during startup, reducing the risk of local cooling.
What residual moisture level can I expect?
Our systems include high-efficiency centrifugal dryers. For most standard polymers, final surface moisture is typically targeted below 0.1% by weight—meeting typical packaging and conveying requirements. Exact performance depends on material characteristics and throughput; specific values are available upon material specification.
Can your system be integrated into an existing extrusion line?
Yes. USEON provides both full turn-key extrusion lines and standalone underwater pelletizing units. Our modular systems can be customized to match your existing extruder’s flange interface, throughput requirements, and floor layout.
How do you handle wear resistance for abrasive materials like glass fiber?
For high-filler or reinforced applications, we provide die plates with specialized alloy coatings and carbide blades. Combined with hydraulic compensation, the system fine-tunes blade pressure to balance cutting quality with tool longevity.
What information do you need to recommend a suitable model?
To provide an accurate proposal, we typically require: material type/formulation, Melt Flow Rate (MFR/MFI), target throughput, required pellet size, and facility utility conditions.
Do you offer lab-scale equipment for R&D?
Yes. We offer the Lab35 lab-scale extrusion system with a matching modular underwater pelletizing system. This configuration is well suited for material development in universities, research institutes, and corporate R&D centers.
Get a quote
Send the material, its melt flow rate, the throughput and the pellet size. We recommend the model and the die, knife and water configuration.
- 01Material type and formulation, MFR / MFI
- 02Target throughput and required pellet size
- 03Model, complete line or standalone unit, quotation
Souder Chen
Head of Compounding Division
With USEON since 2008. Twin screw compounding, devolatilization and recycling lines.