Better productivity by measuring web tension profile

The stability of a paper web as its runs in the paper machine and in the printing press determines the productivity of the whole chain - from headbox to printed product. Runnability management is becoming still more important when machine widths and production speeds are increasing year by year. One of the critical parameters is the web tension. An uneven tension profile causes slackness in the web, wrinkling and web breaks leading to poor runnability. Metso has now, as a result of an extensive developing work, IQTension for reliable monitoring of web tension profile. The system has been adapted in numerous cases of paper manufacturing processes. VTT Information Technology has been developing a new kind of data management and modelling technology for improving runnability and carried out several research projects thus showing the importance of the even tension profile. This paper presents the measuring system and proves web tension profile as a relevant indicator of paper machine runnability. Consequences of unstable tension have been seen in paper machines but also printing press runnability is strongly affected by tension characteristics. Practical cases are outlined for describing experiences in controlling web tension in paper making and its effect on machine performance. Thus, better capacity utilisation and overall productivity has been achieved. In all, more effective production means savings in raw materials, energy and the environment.