Hydraulic headbox operates without air cushion and is fully filled with paper stock. It has some elements as classical high pressurized closed headbox. Main difference lays in built-in block with stage diffuser and an installation of pulsation damper in front of the headbox. This headbox is proper for paper machines operating with lower consistency and speed above 300 m/min.

Main parts

Pulsation damper (1) is installed before headbox itself, including inlet section, perforated plate with stage openings and top part with side outlet to the distributor. Air cushion occurs above the stock level in the damper. Stock inlet is either vertical or horizontal. Optimal stream through the headbox is done by inlet geometry, perforated plate and keeping the proper stock level. Major task of this system is dampening of pulsation in main stock stream caused by cleaners in approach flow system. The equipment could be designed as round distributor as well because all benefits of the system remain but stock inlet to the headbox is done through distribution hoses having identical diameter and length. Last case utilizes favorably consistency control with diluting water.

Inlet body(2). Its role is guide the stock to paper machine run direction and distribute it homogenously across whole paper web width. Inlet bodies are suited with recirculation. Recirculation setting is very important due to certain paper properties. When the round distributor and headbox is connected through the distribution hoses an inlet body with constant cross profile without recirculation is used.

Stage diffuser block (3) distributes the stock regularly across whole width of the headbox and produces controlled turbulences to de-flocculate the fibres and let to each stock stream from diffuser outlet even flow profile. The block is produced from plastic or stainless steel with plastic inserts. The third alternative enables optimizing in case when real throughput doesn’t correspond with dimensioned throughput or when the intensity of turbulence should be changed.

The same could be done in case of throughput break for instance headbox lip damage. Identical inserts don’t have to be installed across the whole diffuser but inserts with smaller or bigger profile can be used in the edge parts. Concerning this aspect the stage diffuser has big potential for operation optimizing.

Inlet chamber with outlet nozzle (4) brings the paper stock to the wire and rectifies its outlet. It is of stainless steel and parts of headbox coming in touch with the stock are of stainless steel to and electric chemically polished. Use of quality material provides headbox with great stability and long life.

Adjusting equipment (5) serves for adjusting of headbox slice slip and stock outlet onto the wire.

Possibilities of cross profile control

• Manual control of top lip shifting mechanisms, eventually valves of dilution water (without automatics)
• Fully automatic control of cross profile through QCS of PM control system – step motors of shifting mechanisms, eventually electronic controlled valves for diluting water

Material

• Headbox is made of stainless steel
• Stands are from common steel, zinc coated outside, respectively of stainless steel
• Base rails are from cast iron
• Part coming in touch with stock are made from stainless steel and polished

Accessories

• Headbox stands
• Front foot bridge or front and back foot bridge incl. ladders
• Source of pressurized air
• Inlet pipes
• Base rails
• Slide valve of the knotter
• Format guides
• Source of dilution water-pump + distribution

Scope of delivery

• Complete machine according to main parts description
• Accessories according to customer’s inquiry

Use of hydraulic headboxes

• For closer flow scope which is important namely in cases when narrow assortment of paper is required
• With round distributor is suitable for speeds above 700 m/min