Method and arrangement in a paper machine or the like close to a moving web to be dried and usually supported against a wire, sealing device and paper machine

A method in paper machine or a board machine close to a moving web to be dried and supported against a wire, the method comprising:

• maintaining first and second spaces with different pressures in connection with the moving web to be dried or with the wire, the two spaces being located one after the other in a web travel direction of the moving web;
• drawing a first control air stream (V1) out from the second space to create a negative pressure in the second space;
• maintaining a seal between the first and second spaces to maintain a pressure difference between the first and second spaces;
• transferring air between the first and second spaces through a first gap between the seal and the moving web or between the seal and the wire;
• maintaining a third space having a pressure, which differs from the pressure in the second space, whereby the seal has a first side toward the web and a second side toward the third space;
• supplying a second control air stream (V2) to the third space;
• transferring air between the second space and the third space through a second gap created between the second and third spaces;
• moving the seal toward or away from the moving web to control a size of the first gap based on an effect of at least one of pressures and air streams prevailing in at least one of the spaces and the gaps;
• monitoring and controlling a volume flow of the first control air stream (V1);
• and
• monitoring and controlling a volume flow of the second control air stream (V2).