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Based on: Industry Standards and Best Practices

Languages: English

Sample Transcript

Fiber dust or short fibers and fines is relatively easy to remove. An air shower or blowing roll can be used to blow dust out of a felt. A stiff bristle brush mounted opposite an inside roll can also help. Stickies and other organics, pitch, adhesives, surface sizing, oil, and grease are harder to remove. High-pressure steam or hot water showers with or without cleaning chemicals can help remove organics from felts. A bristle brush can help remove stickies from the surface of a felt. Cross-linked resins and coatings, wet strength resins, acrylics, and others can be removed by a high-pressure steam or hot water shower with or without chemicals preferably before they harden.

Dryer Felt System Operations

Training Time: 32 minutes

On conventional paper and board machines, the energy required to dry the sheet to the desired moisture target at the reel is supplied by a series of rotating steam-heated dryer cylinders or cans that are grouped together into drive sections. Each drive section is equipped with one or two dryer felts to hold the sheet tightly against the heated dryer cans. This improves heat transfer to maximize drying, and also helps control cross-machine direction shrinkage and other sheet distortions. This course discusses the importance of dryer felts, how they operate, typical installation steps, felt guiding components, and the safety hazards that are present around dryer felt systems.

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Expertly Designed For Maximum Retention
Multiple Language Support
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Training Content + Interactive Quizzes

On conventional paper and board machines, the energy required to dry the sheet is supplied by rotating steam-heated dryer cylinders that are grouped into multiple drive sections.

In single-tiered "unirun" felt sections, vacuum rolls are often installed on the lower level to help hold the sheet to the rolls.

During installation, a “leader” (an extra length of fabric) is provided to tie the new fabric to the old fabric, so the old fabric can be used to thread the new fabric through its run.

Learning Objectives

  • List the main operating requirements for paper and board machine dryer felts
  • Describe typical dryer can arrangements, felt runs, and locations of single-tiered and double-tiered dryer sections
  • List the major steps required to install a new dryer felt
  • Identify which felt seam types are less likely to mark the sheet
  • Identify and describe typical felt guiding system components
  • Explain how felts are guided and tensioned
  • Explain how seams are straightened
  • Describe common felt contaminants and how they can be removed
  • Identify safety hazards and safety guidelines related to dryer felt systems
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Dryer Felt System Operations FAQs

Why does a dryer "felt" look less like a felt and more like a regular woven fabric?
Modern dryer felts are woven to be as porous as possible to allow water vapor to escape. Felted materials do not allow enough air and water vapor to pass through.

Are different styles of dryer felts used in the different dryer sections on a paper or board machine?
Felts closer to the wet end, where the sheet is wetter and weaker, are often more tightly woven in order to “pump less air” and prevent sheet flutter and sheet breaks.

What is the purpose of a positioner?
The purpose of the positioner is to keep the autoguide centered so that it can make adjustments in both directions at all times.

Why is it important for the felt stretch roll to have a lot of "wrap"?
The high roll wrap ensures that the stretch roll movements serve only to change the felt length, and do not affect fabric guiding.

Why are the bottom felts often missing in later dryer sections?
The sheet is mostly dry in later dryer sections, and the absence of a bottom felt makes them somewhat self cleaning during threading and sheet breaks.

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