Runnability component and a method for controlling underpressure in a drying section of a paper machine or the like

A runnability component for a drying section of a paper machine, the machine having a pocket space between two drying cylinders and one turn roll, the pocket space being formed by a first drying cylinder, a second drying cylinder located after the first drying cylinder in the longitudinal direction of the machine, a turn roll located between, and offset from, the first and second drying cylinders, and a wire supporting a web and travelling from the first drying cylinder to the turn roll and from the turn roll to the second drying cylinder, a first web run being formed between the first drying cylinder and the turn roll and a second web run being formed between the turn roll and the second drying cylinder, with the web running on an outer surface of the wire relative to the pocket space and on the periphery of the turn roll, the runnability component comprising:

• a box-shaped component elongated in the cross-direction of the paper machine and extending substantially over an entire width of the first and second web runs and positionable in the pocket space, the box-shaped component having an entry side, an exit side, and an intermediate side between the entry side and the exit side;
• and
• a sealing element on an outer surface of the entry side dividing the outer surface of the entry side into a first part and a second part, the entry side having a channel extending from the first part to the second part.

A method for saving energy in a drying section of a paper machine, the machine having a pocket space between two drying cylinders and one turn roll, the pocket space being formed by a first drying cylinder, a second drying cylinder located after the first drying cylinder in the longitudinal direction of the machine, a turn roll located between, and offset from, the first and second drying cylinders, and a wire supporting a web and travelling from the first drying cylinder to the turn roll and from the turn roll to the second drying cylinder, a first web run being formed between the first drying cylinder and the turn roll and a second web run being formed between the turn roll and the second drying cylinder, with the web running on an outer surface of the wire relative to the pocket space and on the periphery of the turn roll, the method comprising:

• sealing off the pocket space with a box-shaped component elongated in the cross-direction of the paper machine and extending substantially over the entire width of the first and second web runs and positioned in the pocket space, the box-shaped component having an entry side, an exit side, and an intermediate side between the entry side and the exit side, the entry side having an entry side blow nozzle positioned to blow air substantially against the travel direction of the web and away from the pocket space in a gap between the box-shaped component and the first drying cylinder;
• sealing off a gap between the box-shaped component and the first drying cylinder with a sealing element on an outer surface of the entry side dividing the outer surface of the entry side into a first part and a second part, the entry side having a channel extending from the first part to the second part;
• and
• creating an underpressure in a first underpressure zone defined by the sealing element, the first part of the outer surface of the entry side of the box-shaped component, the intermediate side of the box-shaped component, the exit side of the box-shaped component, the turn roll and the wire;
• creating an underpressure in a second underpressure zone in the pocket space defined by the sealing element, the second part of the outer surface of the entry side of the box-shaped component, and the wire;
• controlling a pressure difference between the first and second underpressure zones by means of the channel.