Size Press in Paper Machine

The size press is located behind the pre-drying section of the paper machine. It is designed as a two-roll press with hydraulic or pneumatic loading, where the rolls are positioned horizontally. The movable roll, which is the first roll in the paper run direction, is situated below the stationary roll.

Design Features

Rolls:

• Dynamically balanced for the required speed.
• Can be coated with different materials (rubber, ceramics) based on the type of paper and sizing agent used.
• The sizing agent is introduced through distribution pipes between the rolls and is retained by external dams.
• Excess sizing agent is collected and redirected back to the working station through a system of waste troughs and pipes.
• Rolls not in contact with the paper web and their front parts are cleaned by side and front doctors.

Sizing Process:

• The paper web passes through a sizing bath.
• Sizing agent volume is controlled by a set of valves, which can be regulated manually or electro-pneumatically.
• The paper can be sized on both sides or only one side as required.
• The paper web is guided through the size press using an inlet guide roll and spreader roll to ensure even distribution before entering the after-drying part.

Threading System:

• Equipped with a threading rope system to safely feed the paper web from the previous drying section to the following drying section.

Main Parts

1. Bearing Structure (1):

   • Comprised of individual stands fixed by bolts and locks.

2. Stationary Press Roll with Bearing (2):

   • Fixed in position, provides a stable press surface.

3. Movable Press Roll with Bearing (3):

   • Positioned below the stationary roll, adjustable for press loading.

4. Shifting Equipment:

   • Adjusts the position of the inlet guide roll to modify the paper web run.

5. Paper Guide Rolls (4):

   • Direct the paper through the size press and into the drying section.

6. Side and Front Doctors (5):

   • Clean the non-contact surfaces of the rolls.

7. Spreader Roll with Drive (6):

   • Ensures the paper web is spread evenly before entering the drying section.

8. Size Agent Inlet (7) and Outlet (8):

   • Introduces and removes the sizing agent, maintaining a controlled flow.

9. Hydraulic Circuit, Control Console, Pneumatic Circuit:

   • Manages the press operation and loading systems.

10. Safety Covers and Foot Bridges (9):

    • Provide operator safety and accessibility for maintenance.

Material

• Bearing Structure and Rolls: Made of common carbon steel.
• Size Agent Inlet and Outlet Parts: Made of stainless steel for corrosion resistance.

Accessories

• Rope Threading System: For safe paper web threading.
• Size Press Drive: Includes both mechanical and electric components with control systems.
• Sizing Agent Preparation System: Ensures proper preparation and delivery of the sizing agent.

Scope of Delivery

• Complete machine according to the main parts description.
• Optional accessories based on customer requirements.

Paper Surface Treatment

1. Surface Sizing:
   • Improves paper quality and reduces sizing agent consumption due to better retention compared to sizing in substance.
2. Surface Treatment with Special Agents:
   • Achieves hydrophobic, greaseproof properties, etc.
3. Surface Dyeing:
   • Saves costs compared to dyeing in substance, achieves special color effects, and reduces wastewater pollution.
4. Application of Thin Special Coatings:
   • Thermoplastics, pigments, clays, etc.

Technical Parameters

Advantages:

• High Sizing Efficiency: Ensures effective paper treatment.
• High Operational Reliability: Provides consistent performance.
• Small Space Demands: Compact design for easy integration.

The size press enhances the quality and properties of the paper by applying sizing agents, achieving better surface characteristics, and optimizing the paper production process.