Index Quality of Head Box

The head box is designed to meet stringent quality standards, ensuring consistent paper formation and superior paper quality. The key quality indices are as follows:

• Cross Base Weight Difference: ≤ ±1.5% (for an appraisal base weight of 200 g/m²)
• Opening Width Difference: Between the upper slice and bottom lip is ≤ 0.1mm
• Surface Roughness Inside the Head Box: ≤ 0.4μm (achieving a mirror surface result)
• Liquid Level Accuracy: ≤ 0.5mm
• Pressure Accuracy Inside the Head Box: ≤ 0.5%
• MD CD Ratio: Variable from 1.25:1 to 1.8:1

Design Parameters

Box Body:

• Airtight attenuation pond with overflow holes on both sides.
• Can be installed with overflow on one or both sides.
• Uses an oblique stock-inlet to reduce stock retention.
• Features PMMA view holes for quick cleaning.

Inlet Taper Manifold:

• Consists of tapered and rectangular manifolds with a pressure balance observing pipe.
• Square taper manifold can be adjusted up and down for easy cleaning.

Distribution Elements:

• Three-step diffuser made of organic glass integral casting.

Holy Roll:

• Double holy roll head box with throat roll and slice roll.
• Roll body holes are in a spiral helix with an opening ratio of 35-39% for the throat roll and 49-52% for the weir plate roll.
• Driven by a worm reduction with a TEFC motor, the gear box can adjust the holy roll speed according to the paper machine’s operating speed.

Upper-lip Regulator:

• Includes whole width regulating device, part micrometric setting, and frame against deformation.
• Up/down regulation range: 0-100mm
• Front/back range: 5-30mm, with scale index.
• Micro-adjuster allows precision adjustments to maintain cross base-weight differences within allowable ranges.

Lower Lip: Fixed.

Injection Spray Pipe: Fixed, made of stainless steel with special stainless steel shower nozzles.

Material of Construction (MOC)

• Inlet Pipe: Stainless steel (304), including companion flange.
• Stepped Hole Diffuser: PMMA.
• Side Wall: Stainless steel plate (304).
• Upper Part: Stainless steel (304).
• Bottom Beam: Stainless steel (316L) with mild steel reinforcing ribs.
• Upper-lip Frame: Stainless steel (304).
• Vertical Small Lip Plate: Stainless steel (316L).
• Holy Roll: Stainless seamless steel tube (304).
• Bottom Lip: Stainless steel (304).
• Micro-adjuster: Cast aluminum.

Head Box Controlling System

A. Controlling Parameters:

• General pressure, liquid level, stock speed/wire speed ratio.
• Uses pressure transmitter to test general pressure head and differential-pressure transmitter to test stock level.
• Computer control signals (4-20mA DC) regulate the pulp-distributing fan pump frequency converter and roots blower to maintain stable stock jet speed.

B. PIC – General Pressure Head Control:

• EJA flange differential pressure transmitter.
• PLC regulating loop with AI & AO interface circuit.
• Pulp distributing fan pump VFD (supplied by customer).

C. LIC – Level Control:

• EJA flange-type level transmitters.
• PLC regulating loop with AI-AO interface circuit.
• Roots blower.

D. Control Accuracy:

• Level control within ±1mm.
• General pressure fluctuation control within ±0.5%.

Advantages

• High dewatering efficiency.
• Space-saving design.
• Improved paper symmetry.
• Enhanced web strength and reduced/eliminated porosity.
• Better fiber formation in paper sheets.
• Improved dewatering capacity monitoring.

This design ensures high-quality paper production, meeting stringent industry standards and offering flexibility for various paper grades and production requirements.