Hard Calendar for Paper Machines

A hard calendar is a machine typically installed at the end of the paper machine (PM) line before the reel. It is designed for both-sided smoothening of paper webs for the production of industrial and cultural papers. A steam box is sometimes installed before the calendar to further enhance the smoothness of the paper surface.

Design Features

Multi or Single-NIP Press:

• NIP Combinations:
  • Two hard rolls.
  • An oil-heated thermo roll and a hard roll.
  • An oil-heated thermo roll and a swimming roll (hard) with camber control according to the load applied.

Main Parts

1. Supporting Structure:

   • Composed of structural steel stands.
   • Minimizes operating vibrations.
   • Stands are connected by strengthened bolts and designed for safe handling during installation with a crane or other lifting devices.
   • Provides maximum machine rigidity both at standstill and during operation.

2. Top Roll:

   • Solid or thermo roll.
   • Fixed or floating with air bellow loading/lifting.
   • Made of cast iron with a chilling depth of 10-12 mm.

3. Bottom Roll:

   • Solid or swimming roll.
   • Fixed or floating with hydraulic upward loading/lowering.
   • Made of cast iron with a chilling depth of 10-12 mm.

4. Swinging Doctors:

   • Used to clean the rolls during operation.

5. Spreader Roll:

   • Ensures even distribution of the paper web.

6. Web Guiding Roll with Bedding:

   • Guides the paper web through the calendar.

7. Pneumatic / Hydraulic Loading:

   • Applies the necessary pressure for smoothening.

8. Heating Station for Thermo Roll:

   • Provides oil heating for the thermo roll.

9. Hydraulic Station for Swimming Roll:

   • Controls the camber and loading of the swimming roll.

10. Drive for Both Rolls:

    • Powers the rotation of the rolls.

Advantages

• Easy Installation and Assembly: Designed for straightforward setup and integration into existing PM lines.
• Simple Routine Maintenance: Facilitates regular maintenance with minimal downtime.

Additional Features

• Enhanced Smoothness: The optional steam box installed before the calendar can further improve the smoothness of the paper surface.
• Load Control: The camber control of the swimming roll adjusts according to the load, ensuring consistent paper quality.

This hard calendar design ensures high-quality smoothening of paper webs, enhancing the final product’s surface quality while maintaining ease of installation, operation, and maintenance.