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Top Wire Formers


The Walmsleys Top Wire Former is an extremely versatile unit that can be retro-fitted to almost any Fourdrinier. It significantly increases the water handling capacity of the forming section, allowing higher production rates or lower headbox consistency. The additional water removed is taken from the top half of the sheet, where it is normally harder to drain. This brings the additional benefit of improving structural two-sidedness, by balancing the water removal pattern. Formation is dramatically improved by the action of the blades, and tensile strength, smoothness, porosity, and many other sheet properties are also enhanced. The top wire former can be applied across the basis weight range, from newsprint and graphics grades to heavyweight packaging boards.

  • Complete Sections, Upgrades and Enhancements
  • CIVB Units, Under Wire Boxes, Opposed Blade Units
  • Provides additional dewatering capacity on a fourdrinier table
  • Provides controllable upwards vs. downwards drainage
  • Provides additional dewatering capacity on a fourdrinier table
  • Provides controllable upwards vs. downwards drainage

With a single wire Fourdrinier water is removed in one direction only. With a Fourdrinier and Top Wire Unit water is removed both upwards and downwards. Fines are now removed equally from top and bottom sides, these fines are re-circulated by the white water loop. Hence fines content remains the same, but the fines become more evenly distributed through the sheet, top sides becomes slightly leaner in fines, bottom side becomes heavier in fines. The result is a sheet with an even fines distribution.

The Walmsleys Top Wire Unit can remove up to 40% of the water content of the sheet, this allows the evensidedness to be controlled. Two-sidedness can also be influenced by pressing & calendering, such operations cannot correct for the structural differences created by the former.

The physical position of the top wire unit has a large influence on the dewatering balance of the former, Close to the Headbox - Upward and Close to the Couch - Downward. This is simply caused by the amount of water available to be removed; for sidedness, an optimum position exists.