METHOD FOR CONTROLLING THE PRESSURE LEVEL OF VACUUM OF A SUCTION ROLL OR ROLLS IN A PAPER/BOARDMAKING MACHINE

摘要

The invention relates to a method of controlling the vacuum level in a suction roll/rolls in a paper/board machine, in which a web (W) is passed from a wet wire (H0) over a pick-up roll (11) to a press section (100). In the method, the web (W) is conveyed forwards through nips (N1, N2) between press rolls in the press section and further to a dryer section (200). In the method a pick-up roll (11) is used which can be raised and lowered and which is a suction roll, the roll shell of which has been perforated and which comprises an inside suction box (40), by means of which a suction zone (D1) is formed, whereby, when the pick-roll (11) is moved into contact with the web transferred on the wet wire (H0) into a pulper, the web (W) is transferred by means of the vacuum adherence produced by the pick-up roll (11) to the press section (100) into connection with a felt (H1). In the method, the vacuum produced in the suction zone (D1) of the pick-up roll (11) is controlled by adjusting the speed of rotation of a vacuum pump (10a1), the speed of rotation of which can be controlled and which produces the vacuum. In the method, the speed of rotation of the vacuum pump (10a1) is increased at the stage at which the pick-up roll (11) is transferred into connection with the web (W) situated on the wet wire (H0) in order to transfer the web to the press section.