Spiral dryer fabric is a flexible dryer mesh made of polyester (PET) monofilament exclusively used in the dryer section of paper machines. Unlike the woven structure of flat-woven dryer fabrics, it is constructed by spirally winding monofilaments and interlocking them without weft yarns. It is the mainstream choice for high-speed production of high-grade paper. This article gives a precise analysis from core properties, structure, performance, and applications.

1. Core Definition & Material Properties

Spiral dryer fabric uses only high-viscosity polyester (PET) monofilament (no flat yarns). Special equipment winds monofilaments into continuous spiral loops, which are then locked by adjacent loops with a seam wire (connector wire) to form an endless belt. Some high-end versions use hydrolytically stable polyester monofilament to withstand the high-temperature and high-humidity environment of the dryer section.

Key material advantages: operating temperature 120–190 °C, acid and alkali resistance, anti-aging, low elongation, stable dimensions during long-term operation.

2. Key Structure & Classification

The spiral dryer fabric mainly consists of spiral yarns (main body, determines aperture and air permeability) and seam/connector wires (connection, determines strength and flexibility). It has no layer structure and is classified as follows:

1. By cross-section of spiral yarn
   • Round filament spiral fabric: general-purpose, uniform air permeability, moderate wear resistance.
   • Shaped filament (e.g., oval) spiral fabric: smaller contact area with paper sheet, lighter marks, suitable for high-grade cultural paper, coated paper.
2. By seam wire type
   • Single seam wire: standard type, good flexibility, low tension requirement, suitable for medium-high speed.
   • Double seam wire: reinforced type, higher strength, lower deformation, suitable for ultra-high speed (>1200 m/min).
3. By joint type No traditional mechanical joints; all use spiral loop connection (smooth, step-less), custom-made endless belt for direct installation.
4. By air permeability
   • Low: <300 m³/(m²·h) for thin paper at low drying temperature.
   • Medium: 300–800 m³/(m²·h) for general use.
   • High: >800 m³/(m²·h) for rapid dewatering of high-moisture webs.

3. Core Advantages (vs. Flat-woven Dryer Fabric)

1. Excellent flexibility and smooth running Without weft yarns, the fabric can bend freely. The joint is gap-less and step-less, with low vibration and noise even at high speed (>800 m/min), avoiding scratches and heavy mesh marks.
2. Highly customizable air permeability Air permeability can be precisely controlled by adjusting filament diameter and spiral pitch, ranging from 100 to 1500 m³/(m²·h), adaptable to various drying processes.
3. Better sheet surface quality No interlaced points; contact with the sheet is linear rather than point contact. Combined with shaped filaments, mesh marks and indentations are minimized, ideal for high-grade cultural paper, coated paper, etc.
4. Easy local repair, low loss The interlocked spiral structure allows partial replacement of broken filaments or seam wires without replacing the whole fabric, reducing maintenance cost.
5. Adaptable to special dryers Flexible structure fits curved dryers, air floatation dryers and other non-standard drying equipment, which flat-woven fabrics cannot match due to rigidity.

4. Main Limitations

1. Low rigidity, easy to run off-center or wrinkle Without weft restraint, dimensional stability is lower than flat-woven fabrics. It requires high-precision tension control, guide rolls and web guiding systems; otherwise, it easily wanders, wrinkles or sags.
2. Higher purchase and maintenance cost Complex manufacturing and higher material requirements lead to a 30%–50% higher cost than flat-woven fabrics of similar permeability. It also needs regular cleaning.
3. Relatively lower wear resistance Without interlaced support points, local wear may accelerate in contaminated or scaled dryer environments.
4. Narrow application range Not suitable for heavy paperboards (e.g., corrugated paper, linerboard, basis weight >200 g), as the fabric may deform under heavy load. Only for thin paper and specialty paper.
5. Strict tension control Requires stable and uniform tension; excessive tension breaks seam wires, insufficient tension causes sagging.

5. Key Performance Indicators

1. Air permeability: core index, m³/(m²·h).
2. Spiral and seam wire diameter: determines strength and wear resistance.
3. Breaking strength: warp (spiral) and weft (seam wire), N/5 cm.
4. Elongation at break: ≤3% preferred.
5. Flatness: ≤0.5 mm/m for uniform drying.

6. Typical Applications

Spiral dryer fabric is designed for medium–high to ultra-high speed thin paper and specialty paper:

1. High-grade cultural paper: offset paper, writing paper, copy paper (800–1200 m/min, low marks required).
2. Specialty thin paper: coated paper, lightweight coated paper, cigarette paper, security paper.
3. Tissue paper: toilet paper, facial tissue on high-speed lines with curved dryers.
4. Nonwovens: high-end spunlace, spunbonded nonwovens.

Not recommended: heavy paperboard, corrugated board, low-speed heavy paper production.

7. Selection & Operation Guidelines

(1) Three Selection Principles

1. By speed: <800 m/min → choose flat-woven fabric (cost-effective). ≥800 m/min → spiral dryer fabric.
   

   1200 m/min → double seam wire + hydrolytically stable polyester.

2. By paper type: Thin paper (<70 g), high-grade paper → spiral fabric. Heavy paper (>200 g) → not suitable. For ultra-low marks → shaped (oval) filament spiral fabric.
3. By equipment: Suitable only for machines with stable tension and web guiding systems and clean dryer sections.

(2) Four Maintenance Keys

1. Tension control: maintain stable and uniform tension.
2. Cleaning: regular high-pressure washing and descaling.
3. Guiding system: ensure stable guide and web guide rolls.
4. Protection: avoid sharp objects damaging the mesh.

8. Quick Comparison: Spiral vs. Flat-woven Dryer Fabric

9. Summary

Spiral dryer fabric is a high-end customized consumable for paper drying, with core values of smooth high-speed running and excellent sheet surface quality. However, it has higher requirements on equipment, cost and maintenance, and is not universal.

It is the optimal choice only when:

• machine speed ≥800 m/min,
• producing high-grade thin or specialty paper,
• equipped with stable tension and web guiding systems. Otherwise, flat-woven fabric is more practical and economical.