Method for preventing vibration of a calender and a calender with an arrangement for preventing vibration

The present invention relates to a method for preventing vibration of a calender comprising at least one fly roll (15) and a calender roll stack with at least three calender rolls (12, 13, 14) forming at least two calendering nips (N), in which method position (P) of the at least one fly roll (15) is adjusted relative to the calender roll stack to prevent fiber web induced nip vibration, or barring. The position (P) of the at least one fly roll (15) is calculated based on frequency of nip vibration, length (L) of travel distance of a fiber web (W) from one calendering nip (N) to the next calendering nip (N) and running speed of the calender (10). The position (P) of the at least one fly roll (15) is defined by a control device (20) automatically on basis of measurements of vibration and/or noise and/or fiber web caliber to prevent the nip vibration, or barring, and the position of the at least one fly roll (15) is defined in 0,5 s - 5 min. The invention also relates to a calender with an arrangement for preventing vibration, which calender comprises a calender roll stack with at least three calender rolls (12, 13, 14) forming at least two calendering nips (N) and at least one fly roll (15) position-adjustable relative to the calender roll stack to prevent fiber web induced nip vibration, or barring. The arrangement for preventing vibration comprises a sensor (21) for measuring vibration in the calender (10) and/or a sensor (24) for measuring noise at the calender (10) and/or a measurement device (23) for measuring caliber of the fiber web (W) and a control device (20) that based on the measurement information calculates the position (P) for the at least one fly roll (15) to prevent the barring and the position (P) of the at least one fly roll (15) is defined in 0,5 s - 5 min by the control de-vice.