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.
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.
The most commonly used sheet material is Valmet Headbox Sheet PC (polycarbonate), also known as Lexan.
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.
Valmet Headbox Sheet PVC provides good chemical resistance for lower temperature applications.
Valmet Headbox Sheet PVC-C offers good chemical resistance combined with good thermal resistance.
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.