Overview
The Open Headbox (also known as an open flow box) is a gravity-fed solution designed for low-to-medium speed paper machines, typically operating below 200 m/min.
Compared to pressurized systems such as air cushion and hydraulic designs, this type of headbox focuses on simplicity, capital efficiency, and ease of operation.
As a fundamental component of the wet end system, it delivers pulp onto the forming wire through a stable overflow mechanism, making it particularly suitable for packaging and board grades.
Working Principle
An open headbox operates based on gravity flow rather than internal pressure.
Pulp stock enters the chamber through a precision-designed manifold distribution system, ensuring even cross-machine distribution. The stock then flows over a weir or discharge opening, where the liquid level determines hydrostatic pressure and controls the jet onto the wire.
Flow stability depends on:
- Consistent inlet flow
- Stable liquid level
- Accurate mechanical adjustment
Due to limited internal turbulence generation, fiber dispersion control is lower than in pressurized headboxes, making this design more suitable for standard-grade production rather than high-precision applications.
Key Features
Simple Gravity-Based Operation
No air cushion or hydraulic system required, reducing system complexity and operator dependency.
Capital-Efficient Solution
Lower initial investment while maintaining reliable production performance.
Precision Slice Lip Adjustment
Equipped with manual or micro-adjustment mechanisms to optimize CD (cross-direction) basis weight profile.
Internal Surface Polishing
All wetted parts are polished stainless steel (SS304/SS316L), reducing fiber deposition and extending cleaning intervals.
Easy Integration
Designed for seamless installation on existing paper machines, making it ideal for retrofit and upgrade projects.
Applications
Board & Packaging Paper
Suitable for linerboard and corrugated medium production.
Low-Speed Paper Machines
Ideal for stable operations with moderate formation requirements.
Small & Medium Paper Mills
A practical solution for cost-sensitive or entry-level production lines.
Technical Specifications
| Parameter | Specification |
|---|---|
| Operating Speed | ≤ 200 m/min |
| Wire Width | 1092 – 4800 mm (Customizable) |
| Pulp Consistency | 0.3% – 1.0% |
| Flow Type | Gravity Flow |
| Control System | Manual or Basic Automatic |
Advantages
Cost-Effective Operation
Lower capital investment compared to pressurized headboxes.
Operational Simplicity
Minimal components reduce operational complexity and training requirements.
Low Maintenance Demand
Simplified structure reduces downtime and maintenance workload.
Proven Stability for Corrugated & Linerboard Production
Reliable performance in packaging-grade applications.
Comparison with Other Types
Vs. Air Cushion Headbox
Open headboxes lack internal pressure stabilization, resulting in lower formation quality and speed limitations. In comparison, an Air Cushion Headbox provides improved flow stability and is better suited for medium-speed production requiring enhanced uniformity.
Vs. Hydraulic Headbox
Hydraulic headboxes offer advanced turbulence control and are designed for high-speed production environments. Compared to open headboxes, a Hydraulic Headbox delivers superior formation quality, precision, and efficiency.
FAQ
Q1: What is the main limitation of an open headbox?
A: It offers limited control over turbulence and flow uniformity, which can affect formation quality at higher operating speeds.
Q2: Is it suitable for high-quality paper production?
A: Open headboxes are primarily used for packaging and board grades rather than high-end printing papers requiring precise formation.
Q3: Can it be upgraded to a pressurized system?
A: Yes. While upgrades are possible, many mills choose to transition to an air cushion or hydraulic headbox to achieve higher speeds, improved formation, and better long-term efficiency.
