Wefapress® plastic diffuser blocks made from high-performance PE-UHMW ensure good fiber separation, uniform sheet formation and long service life in paper machines.
Diffuser blocks are key components in paper machines forming sections, particularly in the areas of fiber separation and fiber distribution in the headboxes. Their role is to generate microturbulence in order to avoid fiber lumps, to separate each single fiber and to evenly distribute the fiber suspension on the complete paper machine width. This ensures consistent and controlled dewatering. Any irregularities in distribution can lead to product defects such as basis weight variations, edge tears, or inconsistent moisture content.
Material selection and production
Modern diffuser blocks are often made from highly wear-resistant plastics. One example is ultra-high-molecular-weight polyethylene (PE-UHMW), as used by Wefapress.
Key characteristics of such materials:
- No water absorption: This results in good dimensional stability without material swelling.
- Best surface finishing: Avoids fiber sticking and agglomeration.
- Homogeneous production without recyclate: The virgin material ensures purity, consistent mechanical properties, and minimizes internal flaws.
- Stress-free inner structure: Achieved, for example, through pressing or sintering processes, which is crucial to prevent warping or cracking under load or temperature fluctuations. Wefapress offers lengths up to 10 m without weld seams.
- Additives such as lubricants or fillers: These enhance wear resistance, improve resistance to abrasive particles, high temperature and chemicals.
Design and construction
A diffuser block must be precisely adapted to the specific machine and process setup:
- Shape and surface: The design of flow channels, surface roughness, and contours are essential to prevent dead zones or jet flows that could cause material losses or uneven sheet formation.
- Dimensional accuracy and tolerances: These ensure uniform gap widths and controlled flow rates.
- Mechanical strength: The block must withstand pressure, vibrations and temperature variations.
- Chemical resistance: In the wet end of paper machines, various chemicals and pH fluctuations are present. The material must remain stable over the long term.
Advantages over traditional material (metal)
| Advantage | Description |
| Corrosion resistance | Plastic does not rust and is less sensitive in humid environments. |
| Lightweight / lower density | Reduced mass simplifies handling and can decrease cleaning or movement energy. |
| Wear resistance / longer service life | Specialized plastics with additives provide high resistance to abrasion, chemicals and high temperature. |
| Production flexibility | Complex shapes, profiles, and custom dimensions are easier and faster to produce than with metal; modifications are less costly. |
| Reduced operating and maintenance costs | Lower wear, easy cleaning, and less downtime help reduce overall costs. |
Challenges and design recommendations
- Abrasive fiber particles: Fibers, mineral fines, or fillers can be abrasive, making a hard, wear-resistant surface essential.
- Deformation / warping: Caused by temperature changes, mechanical loads, or weight – high-quality, stress-free production (without weld seams) is crucial.
- Installation and replacement: Diffuser blocks should be designed for easy mounting and disassembly, ideally in modular form so that only sections need replacement.
Practical Example: Wefapress®
Wefapress offers diffuser blocks that meet all these requirements. Their products are made from PE-UHMW, without recyclates; manufactured under stress-free conditions via pressing or sintering; and enhanced with additives to maximize wear and chemical resistance. Visit: Wefapress.com
Contact: Lena de Beukelaar-Wilting – Marketing T +49 2564 9329 16 E: debeukelaar@wefapress.com – https://wefapress.com
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