Parallel Counter-Rotating Twins
Twin parallel screw and barrel assemblies for compounding, recycling, PVC foam and technical extrusion applications.
PENA® parallel twin-screw assemblies combine outstanding dimensional stability with highly efficient mixing performance. They are manufactured according to the required L/D ratio and feeding, venting and discharge configuration, with nitrided or bimetallic solutions selected according to wear and corrosion requirements.
Parallel Twin Barrels
Manufacturing & Configurations
- Typical lengths range from 16 L/D on older machines to 36 L/D on modern extrusion systems.
- Venting sections are commonly incorporated, with feeding integrated into the barrel or mounted as a separate flanged unit.
- Two construction options are available:
- A) One-piece nitrided barrel.
- B) Nitrided outer body with replaceable inner liner.
Technical Specifications
- Construction A (one-piece): 1.8550 steel, nitrided to approximately 70 HRC with an effective nitrided layer of around 0.5 mm.
- Construction B: Nitrided 1.8550 outer body combined with a bimetallic inner liner manufactured from centrifugally cast tubes.
- Bimetallic liner technology available up to 4,500 mm in length with guaranteed dimensional accuracy.
Bimetallic Barrel Alloys
NITRIDED
67/70 HRC- Abrasion MEDIUM
- Corrosion LOW
A cost-effective solution for applications with moderate wear and limited chemical aggressiveness.
PENA 40
Fe/Cr · 64-69 HRC- Abrasion VERY HIGH+
- Corrosion MEDIUM
Engineered for maximum resistance to abrasive wear, ideal for highly filled compounds and mineral-loaded formulations.
PENA 51
Ni/Co · 51-54 HRC- Abrasion MEDIUM
- Corrosion MAXIMUM++
Specifically developed for fluoropolymers and highly corrosive compounds, providing outstanding protection against aggressive chemical attack.
PENA 68
Ni/Cr/WC · 56-60 HRC- Abrasion HIGH
- Corrosion VERY HIGH+
An advanced balance of abrasion resistance and corrosion protection, recommended for demanding technical applications.
PENA 80
Ni/Cr/WC . Carburo 2160 HV / Matriz 900 HV- Abrasion MAXIMUM++
- Corrosion MAXIMUM++
Our highest-performance alloy, designed to withstand extreme abrasion and corrosion in the most demanding processing conditions.
Technical Advantages Barrels
- For Construction B, refurbishment costs are significantly reduced by reusing the outer body.
- Internal alloy selection can be optimised according to polymer type, mineral fillers, corrosion level and operating temperature.
- The nitrided outer body prevents seizure during future liner replacement operations.
Limits & Capabilities
- Maximum one-piece bimetallic barrel length: 4,500 mm.
- Maximum one-piece nitrided barrel length: 6,000 mm.
Parallel Twin Screws
Typical Materials
- Nitriding steels: 1.8509 (41CrAlMo7), 1.8550 (34CrAlNi7), 1.8519 (31CrMoV9) and 1.8515 (31CrMo12).
- Quenched and tempered alloy steels with tensile strength of approximately 850–950 N/mm².
Technical Specifications
- Following machining and polishing, screws are nitrided to a surface hardness approaching 70 HRC, with an effective nitrided layer of approximately 0.5 mm.
- Typical lengths range from 24 to 36 L/D, although older systems may operate at 16 L/D.
- For severe applications or when paired with bimetallic barrels, welded flight protection is applied. Optional chrome plating is available on the discharge section for specific applications.
Bimetallic Screws Alloys
NITRIDED
67/70 HRC- Abrasion MEDIUM
- Corrosion LOW
An economical solution for standard applications with low wear requirements.
PENA 160
Ni–Cr · >1100 HV- Abrasion VERY HIGH+
- Corrosion MEDIUM
High hardness combined with excellent thermal stability and chemical resistance.
PENA 172
Aleación refinada · 58–60 HRC- Abrasion HIGH
- Corrosion VERY HIGH+
Excellent adhesion and oxidation resistance, ideal for humid and corrosive operating environments.
PENA 175
PTA con WC · >62 HRC- Abrasion MAXIMUM++
- Corrosion MAXIMUM++
Maximum protection against severe abrasion, mineral fillers and extreme wear conditions.
Technical Advantages Screws
- Extended service life through the application of welded protection only where wear occurs, typically on the flights.
- Coating selection matched to the barrel wear system, whether nitrided or bimetallic.
- Complete repair, refurbishment and rebuilding services available in-house.
