Wire Part of the Paper Machine (PM)

The wire part of the PM is crucial for stock dewatering, transforming the stock into a “paper sheet.” The process begins with the stock exiting the headbox onto a longitudinal endless wire, where fibers settle down as the stock is dewatered.

Key Components and Design:

Main Structure:

• Endless Wire: Embraced at the headbox side by a breast roll and on the other side by a suction roll (couch roll) and a driving roll. This combination ensures better driving force distribution and cautious influence on the wire, enhancing paper web removal and transfer into the press part.

• Dewatering Elements:

  • Located in the upper part between rolls, these elements have plastic or ceramic foils.
  • The wire with stock moves over their surface, and dewatering occurs via vacuum contact.

Dewatering Elements and Their Order:

1. Forming Board:

   • Welded from stainless steel and fixed to carriers on stands for height adjustment.
   • Equipped with a wide foil and foils of 65 mm width, made of polyethylene or ceramics.

2. Dewatering Foils:

   • Welded stainless steel, fixed to beams with height-adjustable stands.
   • Foil design can be stationary or turnable for angle adjustments (0 – 2.5°).
   • 65 mm wide foils made of polyethylene or ceramics.

3. Hydrofoils Box:

   • Welded stainless steel, fitted with 5 – 7 foils of 65 mm width.
   • Height adjustable and foils fixed by T-shaped groovings.

4. Depression Water Box:

   • Welded stainless steel with 5 – 7 foils, 65 mm width.
   • Depression created by a fan, regulated by a suction valve and sliding gates.

5. Suction Box:

   • Welded stainless steel, fitted with a cover of polyethylene or ceramics (30 to 40 mm height).
   • Suction zone with slots or round holes, 40 to 50% free cover area.
   • Vacuum created by a vacuum pump and regulated automatically or manually.

6. Multi-Chamber Suction Box:

   • Welded stainless steel, height-adjustable, with different foils in each chamber.
   • Each chamber connected separately to the PM vacuum system, with vacuum created by a pump and regulated by control valves.

Additional Elements:

• Steam Box: Increases paper temperature before pressing, enhancing dryness.
• Rolls and Guide Systems: Guide, carry, and stretch the wire, maintaining the correct tension and alignment.
• Showers: Clean the wire using low-pressure and high-pressure water to remove fibers and prevent contamination.

Advantages of Design:

1. Height and Longitudinal Adjustability: Ensures optimal placement and performance of dewatering elements.
2. Simple Foil Replacement: Facilitates easy maintenance and replacement of foils.
3. Compactness: The design allows for a space-efficient setup.
4. Efficient Dewatering: The correct placement of dewatering elements ensures effective dewatering and fiber formation.

Accessories and Systems:

• Wire Guide Systems: Both manual and automatic systems maintain wire alignment and tension.
• Vacuum Systems: Include water separators, vacuum pumps, and control valves for precise vacuum regulation.
• Doctor Blades and Nozzles: For cleaning and maintaining the wire and rolls.

Conclusion:

The wire part of the PM is an essential component, ensuring efficient stock dewatering and paper formation. With advanced design elements and accessories, the wire part ensures high performance, easy maintenance, and high-quality paper production.