Crescent Former High-Speed Tissue Machine:
The Complete Engineering & Operating Guide

1. The Industry Paradigm Shift: Why the Crescent Former?

In household and commercial sanitary paper production, market profitability is dictated by two decisive metrics: hand-feel softness (bulk & formation uniformity) and specific energy consumption per ton.

Historically, small-to-medium mills relied on traditional cylinder mould machines or Fourdrinier forming tables. However, as international markets require lighter basis weights (13–18 gsm) at speeds exceeding 800 m/min, older technologies hit an insurmountable mechanical wall:

• Fourdrinier Limitations: High two-sidedness, significant fiber loss in free-surface dewatering, high drive power demand, and severe sheet breakage at speeds above 600 m/min.
• Cylinder Mould Limitations: Inability to exceed 200 m/min, poor formation, high MD/CD ratio (often > 3:1), resulting in stiff, rough paper.

The Crescent Former (CF) represents the pinnacle of modern tissue forming technology. By jetting pulp directly into the convergent wedge formed between the forming fabric and the press felt around a solid forming roll, centrifugal force and fabric tension achieve rapid, ultra-gentle two-sided dewatering.

2. Core Mechanical Subsystems & Architecture

2.1 All-Stainless Hydraulic Headbox (SS316L)

All wet-end components in contact with the stock are machined from solid SS316L stainless steel with electrochemical mirror polishing (Ra < 0.2 μm) to eliminate fiber hang-up and slime accumulation.

• Step Diffuser Explosion Chamber: Multiple rows of precisely tapered step tubes generate controlled micro-scale turbulence, breaking up fiber flocs immediately prior to the slice lip.
• Micro-Adjustable Slice Lip: Equipped with micrometer-pitch adjustment screws (or optional motorized QCS closed-loop actuators) to maintain CD basis weight profile deviation strictly within ±1.5%.

2.2 Cantilevered Crescent Forming Unit

The forming roll (Φ1,200 mm) is engineered with stainless steel cladding and heavy-duty spherical roller bearings. The entire forming frame features a pneumatic cantilevered structural beam. This enables maintenance crews to complete full wire and felt replacements in under 90 minutes without dismantling major drive shafts or bearing pedestals.

2.3 Suction Press Section

Equipped with a Φ800 mm blind-drilled, polyurethane-covered suction press roll. Operating at linear nip pressures of 90 to 110 kN/m, it achieves an outgoing sheet dryness of 42% to 44%. Every 1% increase in press dryness reduces dryer steam consumption by approx. 4%, substantially cutting daily operational OPEX.

2.4 Alloy Steel Yankee Dryer vs. Traditional Cast Iron

Traditional cast-iron Yankee dryers are heavy, have thick shells with lower thermal conductivity, and carry catastrophic explosion risks under thermal shock.

SEN International standardizes on Alloy Steel Yankee Cylinders (Φ3,660 mm × 3,200 mm):

• 30% Higher Heat Transfer: Thinner, higher-strength steel walls with internal circumferential grooving drastically increase steam condensation heat flux.
• Zero Explosion Hazard: Ductile steel construction eliminates the brittle fracture risk of cast iron.
• Global Compliance: Manufactured under strict ASME Section VIII Boiler & Pressure Vessel Code and Canadian Registration Number (CRN) standards.

2.5 High-Velocity Hot Air Hood (120 m/s)

A two-half, symmetrical aerodynamic impingement hood operating at nozzle velocities up to 120 m/s and air temperatures up to 250°C (steam heated) or 450°C (gas direct-fired). Equipped with a dual-stage heat recovery system that captures exhaust thermal energy to preheat makeup air and process shower water.

3. Technology Comparison: Crescent Former vs. Legacy Systems

4. Furnish Versatility: Virgin Wood Pulp & Recycled Waste Paper

SEN International turnkey lines are engineered to process both 100% Virgin Bleached Kraft Pulp (NBSK / BHKP) and 100% Post-Consumer Recycled Paper (SOW / MOW / Ledger).

When utilizing recycled waste paper, the line integrates an advanced Flotation Deinking and High-Consistency Thermal Dispersion System (95°C–105°C). Heavy contaminants, micro-stickies, latex, and residual ink particles are dispersed down to invisible sizes (<40 μm), completely eliminating black specks, stickies, and cylinder coating buildup.

5. Standard Turnkey Delivery Models