Improving productivity by measuring web tension profiles

Production without runnability disturbances is the goal of every papermaker and printer, but in practice achieving this goal still lies far in the future. One of the biggest reasons for this is the unstable web tension profile in the cross direction on the paper machine, which may cause wrinkles and web breaks. Metso, has now developed 'IQTension' for reliable monitoring of the web tension profile, and VTT Information Technology has developed new data management and modelling technology for improving runnability. This paper presents the measuring system and shows that the web tension profile is a relevant indicator of paper web runnability. The paper machine tension profile formation mechanism has been studied by mathematical and physical modelling. It is proposed that the open draws in the dryer section cause the convex shape of the tension profile, and possible ways of controlling paper machine tension profiles are discussed.