Multi-zone Rolls : Nipco Roll

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 six or eight zones with two counteracting zones at the edges. All zones are pressurized separately in order to “design” the CD line load curve. The pistons are supported by a fixed beam which takes the press force and deflects. One special feature of the Nipco roll is the self-loading characteristic of the F-type. Self-loading means that no external loading devices are required to load the press nip. The movement for loading or opening the nip is performed by the before mentioned hydrostatic pistons. This movement is made possible by special bear¬ings which allow the shell to move in the nip direction only.

6.2.3.2.2 Hydrein Roll
Introduced by Kleinewefers in 1979, the roll principle is similar to the Nipco Roll with the special feature of having “double pistons” in a circumferential direction.

6.2.3.2.3 Hydro Vario Roll
This roll was introduced by Küsters in 1980. It consists of a shell, a fixed axial beam and in between these a pressurized oil chamber. For local line load control hollow pistons placed inside the oil chamber are tightly pressed to the shell to eliminate the oil pressure and thus reduce the press force at that position. In addition these pistons can be applied with a higher oil pressure than in the pressure chamber itself which increases the line load locally.

6.2.3.2.4 Nipcorect Roll
Voith introduced the Nipcorect roll in 1994. These fine control rolls have been developed to control the line load profile in a much finer pattern, e. g. with a roll having more than 30 and up to 60 zones. In order to make this fine control effec¬tive the rigidity of the shell has to be reduced dramatically, for instance by using very thin metal or nonmetal shells. Further examples of this kind of roll are the multi-HV-roll of Küsters and the Sym CD roll of Metso.