Overview
The Hydraulic Headbox, also known as a full-hydraulic flow box, is a pressurized stock approach system designed for modern high-speed paper and board machines. Unlike an air cushion headbox, it operates as a fully liquid-filled system without an internal air pad.
Stock enters through the tapered inlet header and is distributed across the machine width before passing through the Step-Diffuser Turbulence Generator. Controlled turbulence helps disperse fiber flocs and maintain a uniform fiber suspension as the stock approaches the slice opening.
VANVEO hydraulic headboxes are suitable for paper and board production where stable stock flow, consistent jet conditions, formation quality, and cross-direction profile control are important.
Working Principle
The hydraulic headbox controls stock pressure, flow distribution, and turbulence through a fully hydraulic flow path.
Stock first enters the tapered inlet header, which progressively distributes the flow across the machine width. It then passes through the Step-Diffuser Turbulence Generator, where controlled changes in flow velocity and direction create micro-turbulence.
This turbulence helps reduce fiber flocculation and promotes a more uniform fiber suspension before the stock reaches the slice chamber.
The homogenized stock is discharged through the precision-adjustable slice opening onto the forming section. Stable hydraulic pressure and flow conditions support consistent jet performance and accurate jet-to-wire ratio adjustment at high machine speeds.
For a general explanation of headbox operation, see our Headbox Working Principle guide.
Key Features
Step-Diffuser Turbulence Generator
The Step-Diffuser Turbulence Generator creates controlled micro-turbulence within the stock flow to promote fiber dispersion and reduce fiber flocculation without internal rotating rectifier rolls.
Stable Stock Flow and Jet Performance
The tapered inlet header and diffuser system are designed for uniform stock distribution across the machine width, supporting stable jet conditions and consistent sheet formation at high machine speeds.
No Internal Rotating Components
The hydraulic configuration uses a fixed turbulence-generation system rather than internal rotating rectifier rolls. This reduces the number of moving components inside the headbox and simplifies the internal flow structure.
Precision Slice Adjustment
The slice opening can be adjusted according to production requirements. Manual or automatic adjustment configurations are available for controlling the stock jet entering the forming section.
Dilution Water Control Compatibility
The hydraulic headbox can be configured for dilution water control systems to support cross-direction basis weight profile adjustment where required.
Stainless Steel Wet-End Construction
Wet-end components can be manufactured from SS304 or SS316L stainless steel. Polished or electropolished surfaces can be provided according to process and cleanability requirements.
Applications
VANVEO hydraulic headboxes are designed for high-speed paper and board production, including:
- Fine paper and writing paper
- Printing paper
- Kraft paper
- Packaging paper
- Linerboard
- Fluting paper
- Paperboard and specialty board
- High-speed paper machine upgrades and retrofit projects
The hydraulic configuration is particularly suitable for paper machines operating at approximately 600–1200 m/min. The final design is determined according to machine width, paper grade, stock consistency, flow rate, and forming-section requirements.
Technical Specifications
| Parameter | Specification |
|---|---|
| Headbox Type | Hydraulic / Full-Hydraulic Headbox |
| Operating Speed | 600–1200 m/min |
| Machine / Wire Width | 1092–6000 mm, customizable |
| Pulp Consistency | 0.3–1.2% |
| Turbulence Generator | Step-Diffuser Type |
| Pulsation Control | External Pulsation Dampener |
| Material Construction | SS304 / SS316L Stainless Steel |
| Surface Finish | Polished / Electropolished, according to requirements |
| Slice Adjustment | Precision Manual or Automatic Control |
| Dilution Control | Available according to configuration |
Final specifications are determined according to paper grade, machine speed, machine width, stock conditions, flow rate, and forming-section requirements.
Hydraulic Headbox Design & Customization
Hydraulic headboxes are configured according to the specific requirements of each paper machine rather than supplied as a single standard size.
VANVEO can configure the headbox according to:
- Paper machine width
- Operating speed
- Paper or board grade
- Stock consistency
- Required stock flow rate
- Slice opening and adjustment method
- Turbulence generator configuration
- Dilution water control requirements
- Manual or automatic control
- Existing machine dimensions for retrofit projects
This allows the hydraulic headbox to be matched to the existing approach flow and forming systems.
Advantages for High-Speed Paper Machines
Consistent Formation
Controlled turbulence promotes uniform fiber dispersion and helps maintain consistent sheet formation during high-speed production.
Stable Hydraulic Flow
The fully hydraulic configuration provides controlled stock pressure and flow conditions, supporting stable jet performance at the forming section.
Simplified Internal Structure
Without internal rotating rectifier rolls, the headbox has fewer moving components within the wet end, simplifying inspection and maintenance.
Automation Compatibility
Depending on the configuration, the hydraulic headbox can be integrated with automatic slice adjustment, dilution water systems, and paper machine QCS/DCS control systems.
FAQ
What is a hydraulic headbox?
A hydraulic headbox is a pressurized, fully liquid-filled headbox used to distribute pulp stock uniformly across the width of a paper machine. It uses controlled hydraulic flow and turbulence generation to prepare the stock before it reaches the forming section.
What is the operating speed of a hydraulic headbox?
VANVEO hydraulic headboxes are typically designed for paper and board machines operating at approximately 600–1200 m/min. The final design depends on machine width, stock conditions, flow rate, paper grade, and forming-section requirements.
Why is a turbulence generator used in a hydraulic headbox?
The turbulence generator creates controlled micro-turbulence within the stock flow. This helps disperse fiber flocs and maintain a more uniform fiber suspension before the stock reaches the slice opening.
Does a hydraulic headbox require a pulsation dampener?
An external pulsation dampener is commonly used with hydraulic headbox systems to reduce pressure fluctuations from the approach flow system and maintain stable stock delivery to the headbox.
Can a hydraulic headbox be customized for an existing paper machine?
Yes. Hydraulic headboxes can be configured according to machine width, operating speed, stock consistency, flow rate, slice requirements, and existing machine dimensions. Retrofit configurations can also be considered for paper machine upgrades.
For a detailed comparison between hydraulic and air cushion headboxes, see Air Cushion vs. Hydraulic Headbox: Selection Guide.
