Headbox sheets and wedges for tissue machines
Valmet Headbox Sheets and wedges for improved control of headbox flow turbulence
Headbox sheets used in the headbox are vital for producing a uniform jet flow from the headbox slice to the forming section. The sheets significantly impact end-product quality features such as formation, CD basis weight profiles, thickness and sheet edges, all of which affect the overall paper machine productivity.
Improved sheet formation
More uniform caliper
Enhanced edge properties
More uniform CD basis weight
OEM expertise
Valmet Headbox Sheets incorporate technological know-how based on over 40 years of OEM experience in providing this product. Headbox flow sheets are among the most important headbox components used to produce a uniform flow of stock from the slice opening to the forming section. Flow sheets are offered for all Valmet and its’ predecessors (Beloit, Tampella, MHI, GLV, PMP) headbox types from conventional Fourdrinier and top wire designs to twin wire gap formers.
Comprehensive product portfolio for your specific needs
Headbox Sheet PC
The most commonly used sheet material is Valmet Headbox Sheet PC (polycarbonate), also known as Lexan.
- PC withstands high operating temperatures (up to 135°C, 275°F)
- Not resistant to alkalis or solvents
- Expected lifetime 6-12 months
- Easily adaptable to any headbox design
Headbox Sheet CF
Valmet Headbox Sheet CF provides long useful sheet life from 3 to 5 years.
Carbon fiber sheets are made in one piece: hinge and sheet are combined to each other without glued joints.
- Excellent wear resistance. Life expectancy 3 - 5 years
- Good chemical resistance. No need to remove from the headbox for boil-out.
- No thermal distortion or expansion
- Great lateral stiffness results in easier removal and installation in and out of the headbox
- Unlimited shelf life - no degradation during storage
Headbox Sheet PVC
Valmet Headbox Sheet PVC provides good chemical resistance for lower temperature applications.
- Made of polyvinyl chloride (PVC)
- Good chemical resistance (withstands alkalis, but not dissolvents)
- Maximum operating temperature 50°C, 122°F
- Expected lifetime 12-18 months
Headbox Sheet PVC-C
Valmet Headbox Sheet PVC-C offers good chemical resistance combined with good thermal resistance.
- Made of improved polyvinyl chloride
- Better thermal resistance compared to standard PVC: max operating temperature 75°C
- Good chemical resistance (withstands alkalis, but not dissolvents)
- Expected lifetime 12-24 months
Headbox Wedge CF
Valmet Headbox Wedge CF is especially designed for Valmet OptiFlo.
Valmet Headbox Wedge CF is made of carbon fiber. The expected lifetime of wedges is over 5 years.
Wedges help to maintain optimal disturbance-free fluidization in the slice channel. Their main function is not to produce turbulence at the tip as in the case of conventional headbox sheets. The tip of wedges does not need to be located near the slice opening.
No tricky fine tuning of wedges is required. Only one wedge length and one tip shape are needed due to optimized wedge hydraulics.
Benefits
- Improved control over the scale and intensity of headbox flow turbulence
- Better headbox hydraulic performance
- No need to remove wedges from the headbox during cleaning
- Excellent wear and temperature resistance
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