Selecting the appropriate felt for a paper machine is a critical step in ensuring paper quality and production efficiency. Below are the key factors to consider during selection, with paper basis weight being a fundamental prerequisite that determines the felt’s structure and performance.
1. Paper Basis Weight and Grammage
Paper basis weight directly dictates the felt’s load-bearing requirements and dewatering challenges.
- Low basis weight papers (e.g., tissue, lightweight printing paper): Thin, low-strength, and prone to breakage.
- Require felts that are soft-textured and smooth-surfaced to minimize wear and crushing of the paper web.
- Felts must have good air permeability to ensure rapid dewatering and avoid over-compression of the web.
- High basis weight papers (e.g., paperboard, specialty paper): Thick, high-moisture content, and structurally more stable.
- Require felts with stable structure and excellent compression resistance to withstand higher linear pressure.
- Felts must have sufficient water-holding capacity and good water conductivity for efficient removal of large volumes of water.
2. Paper Type and Quality Requirements
Different paper grades demand distinct felt properties.
- Cultural/Printing Paper: High requirements for surface smoothness and uniformity.
- Felts need to be fine-surfaced and clean to avoid leaving indentations or stains on the paper.
- Packaging Paper/Paperboard: High requirements for strength and stiffness, with relatively lower demands on surface smoothness.
- Felts need to be wear-resistant and structurally stable to endure long-term, high-intensity pressing.
- Tissue Paper: High requirements for softness and absorbency.
- Felts must be soft-textured with minimal fiber shedding to ensure the paper’s feel and cleanliness.
3. Paper Machine Parameters
The operational parameters of the paper machine directly impact the felt’s lifespan and efficiency.
- Machine Speed: Higher speeds demand felts with superior wear resistance, fatigue resistance, and stability.
- High-speed machines typically use needle-punched felts due to their stable structure and resistance to deformation.
- Press Type:
- Conventional Pressing: Requires felts with good compression resistance and elasticity.
- Vacuum Pressing/Shoe Pressing: Felts must have excellent air permeability and compatibility with the shoe plate.
- Shoe pressing, in particular, demands felts with outstanding lateral water drainage and resistance to permanent compression set.
- Linear Pressure: Higher linear pressure in the press section requires felts with enhanced pressure resistance, structural strength, and dimensional stability.
4. Felt Properties
The physical and chemical properties of the felt itself are core criteria for selection.
- Structure Type:
- Woven Felts: Stable structure, long service life, suitable for low-speed, wide-width machines or those producing high-basis-weight paperboard.
- Needle-Punched Felts: Elastic, breathable, and easy to install, these are the most widely used type, ideal for high-speed machines.
- Base Fabric Structure:
- Single-layer base fabric: Cost-effective, suitable for low-basis-weight, low-speed applications.
- Double/multi-layer base fabric: Higher strength and stability, capable of withstanding higher linear pressure, ideal for high-basis-weight, high-speed machines.
- Material:
- Wool: Good elasticity, high moisture absorption, soft surface, but expensive with poor wear resistance.
- Nylon: Excellent wear resistance, high strength, and good elasticity—main raw material for needle-punched felts.
- Polyester: High-temperature resistance, suitable for dryer sections or high-temperature environments.
- Air Permeability and Thickness:
- Air permeability must match the paper grade and machine speed to ensure dewatering efficiency.
- Thickness affects the felt’s water-holding capacity and compression-recovery performance.
5. Operational Cost and Maintenance
- Service Life: Directly related to downtime and replacement costs.
- Maintenance Needs: Ease of cleaning and resistance to deposits impact daily operational costs.
- Total Cost of Ownership: Consider purchase cost, service life, and maintenance expenses to select the most cost-effective option.
Post time: Nov-20-2025