Paper Machine Composite Roll Covers

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6.2.4.3.3 Composite Roll Covers Two basic composite designs for the functional layer of roll covers are used in the paper industry: Composite covers with a fiber reinforced functional layer and com¬posite covers with a cast functional layer (resin covers). 6.2.4.3.3.1 Fiber Reinforced Functional Layer Composite covers with fiber reinforcement in the functional layers are mainly [...]

Paper Machine Polyurethane Roll Covers

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6.2.4.3.2 Polyurethane Roll Covers Polyurethane roll covers were introduced to the paper industry at the end of the 1980s. The outstanding mechanical and dynamical properties make polyurethane the most suitable material for soft elastomeric covers in press positions. Depend¬ing on paper quality and press design, high open surfaces up to 45 % with grooves, blind [...]

Paper Machine Rubber Roll Covers

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6.2.4.3.1 Rubber Roll Covers Rubber roll covers are the covers with the longest tradition. The hardness ranges from very soft elastomeric covers to hard rubber. Both natural rubber and synthetic rubber polymers are used. Typical rubber formulations consist of approximately 8 to 15 ingredients, such as polymers, fillers, processing materials, tackifiers, anti¬degradant components, colorants, activators [...]

Rolls in Paper and Board Machines : Nip Design in Calenders

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6.2.4.2.5 Nip Design in Calenders The functions of covers or coatings in soft nip calenders are twofold. The hard heated roll in the calender is either a chilled iron roll with a hard wear-resistant surface, or it is coated for even more improved wear resistance. The surface of the hard roll needs to be extremely [...]

Paper Machine Rolls: Nip Design in Coating and Sizing

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6.2.4.2.4 Nip Design in Coating and Sizing For coating, sizing or pigmenting in film transfer presses the primary purpose of the cover is both to provide a soft nip and to transfer the applied liquid film uniformly to the paper web. Abrasion resistance is important for keeping the nip geometry constant, as the film thickness [...]

Paper Machine Roll Application and Function

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6.2.4.2 Application and Function 6.2.4.2.1 Corrosion and Wear Protection Covers for paper, wire or felt guide rolls have to protect the metallic roll body against corrosion or wear. In general, these covers are plain and relatively hard materials are used. In drive roll applications the cover has to transfer the torque to the driven wire [...]

Paper Machine Roll Control And Design , Roll Covers

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6.2.3.2.5 Controls Complicated calculations are needed to define the optimum oil pressure in the different zones in order to give the best approximation to the desired CD line load profiles. These have to take into account all elastic bending characteristics not only of the deflection control roll itself but also the whole roll system involved. [...]

Multi-zone Rolls : Nipco Roll

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6.2.3.2 Multi-zone Rolls 6.2.3.2.1 Nipco Roll The Nipco roll (Fig. 6.5) was introduced in 1971 by Escher Wyss. It not only com¬pensates for deflection but also allows one to control the line load in the press nip locally. Here the shell is supported by a number of hydrostatic pistons, which are grouped in at least [...]

Swimming Roll

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6.2.3.1.1 Swimming Roll The swimming roll (Fig. 6.4) was introduced into the paper industry in 1960 by Küsters (Germany). In principle the shell rotates around a fixed axial beam with bearings at each end. A pressurized oil chamber is placed between the shell and the beam which is sealed along the axis against the rest [...]

Dandy Roll , Deflection Control Rolls

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.2.2.4 Dandy Roll These rolls are driven and are used in fourdrinier wire sections, the aim being to improve formation and surface smoothness or to generate watermarks. Dandy rolls are wire covered rolls with a very open structure behind the wire, either built up of rings and bars or of a honeycomb design. They are [...]