Valmet Corporation

Valmet Paper Machinery Inc.

Markku Ellila

Pekka Koivukunnas

Harri Kuosa

Harri Mustonen

Mikko Tani

Jouni Koskimies

Jussi Tuomela

A method for controlling transverse profiles of a web in a web-manufacturing machine, such as a board or paper machine, and/or being treated in a finishing machine. At least one of a transverse caliper, grammage and moisture profiles of the web is measured either directly or indirectly. Actuators acting upon these profiles are regulated by measurement signals. In order to optimize the quality of the web to be produced, the reel formation, and the runnability of the machine, the transverse tension profile of the web to be manufactured and/or treated is measured. Based on the measurement of the transverse tension profile, set profiles are formed which control the actuator(s) of the profile regulation.

System for overall control of different transverse profiles in a paper

In the inventive method and apparatus for calendering a surface of a paper or board web, a temperature difference is created between the web surfaces so that the surface to be calendered is cooler than the opposite surface. In addition, moisture within the web is transferred using the so-called heat pipe effect toward the cooler surface while substantially preventing evaporation of moisture from the web so as to create a predetermined moisture profile transversely through the web and decrease the glass transition temperature of the web at the relatively cooler surface to be calendered. Finally, the web having the predetermined moisture profile is advanced into the calendering nip so that the relatively cooler and moister surface of the web is pressed against the heated roll of the nip to thereby calender that web surface.

Method and apparatus for calendering a paper or board web

A paper web is passed through a calendering nip that is formed between a roll which has been provided with a soft face and a heatable hard roll. The heatable roll is heated so as to plasticize the surface layer of the paper web that is placed at the side of the heatable roll, preferably so that the temperature of the surface layer in the calendering nip exceeds the glass-transition temperatures of the polymers contained in the paper. Before entering into the calendering nip, the paper web is moistened, so as to lower the glass-transition temperatures of the polymers contained in the paper, and pre-heated. The pre-heating of the paper web is carried out by bringing the paper web into contact with the heatable roll before the web enters the calendering nip and by, before the calendering nip, feeding steam or water onto the face of the paper web that is placed at the side of the heatable roll so as to improve the transfer of heat from the hot roll to the paper web.

Method in calendering of a paper web and a calendar that makes use of

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Helsinki, Finland

Markku Ellila