Index Quality of Head Box

• The cross base weight difference is ≤ ±1.5%; Appraisal base weight is 200 g/m2)
• The Opening width difference between upper slice and bottom lip is ≤ 0.1mm.
• Surface roughness inside of the head box ≤ 0.4μm (up to a mirror surface result).
• Liquid level accuracy of head box: ≤0.5mm;
• Pressure accuracy of inside of head box: ≤0.5%;
• MD CD Ratio: Variable from 1.25:1 to 1.8:1

Design Parameters

Box Body: It is airtight attenuation pond, overflow holes on both sides. It can be installed with overflow at one side or both sides. In the meanwhile, it is used by oblique stock-inlet to reduce the stock detained in the head box. View hole PMMA of wallboard is used for quick opening to clean the inside of head box.

Inlet taper manifold: It consists of Tapered and Rectangular manifold, fitted with pressure balance observing pipe. Square taper manifold can be turned up and down to be convenient for cleaning.

Distribution elements: Three-step diffuser, the material is organic glass integral casting manufacturing.

Holy roll: Double holy roll head box has throat roll and slice one. The roll body holes are in spiral helix, opening ratio of throat roll is 35-39%, opening ratio of weir plate roll is 49-52%. The holy roll is driven by worm reduction with TEFC motor. The user can adjust gear box to change the rotate speed of holy roll according to the operating speed of paper machine and use different stocks to achieve the best evenness.

Upper-lip regulator: The upper-lip regulator consists of upper-lip whole width regulating device, part micrometric setting and frame against deformation. For the upper lip, the up/down regulation range is 0-100mm, and front/back range is 5-30mm, with scale index. The micro-adjuster can partially in precision finely adjusts the lip opening to keep cross base-weight difference to be inside the allowable range. The pitch for micro adjustment would be 120-180mm.

The Lower lip is a fixed one.

Injection Spray Pipe: (Fixed) it uses stainless steel pipe, the shower nozzle MOC is special stainless steel.

MOC

The parts and the items in contact with the stock and rotary parts, which need regulation, are all of stainless steel.

• inlet pipe: All inlet pipes are of stainless steel (304) (including companion flange)
• Stepped hole diffuser: the whole piece of PMMA;
• Side wall: stainless steel plate(304);
• Upper part: stainless steel(304);
• Bottom beam: stainless steel (316L)+ Mild Steel (for reinforcing rib), assembling unit
• Upper-lip frame: stainless steel 304;
• Vertical small lip plate is of stainless steel 316L;
• Holy roll: stainless seamless steel tube 304;
• Bottom lip: SS304
• Micro-adjustor: cast aluminum;

Head Box Controlling System

A: The controlling parameters of air cushion head box are general pressure, liquid level, stock speed/wire speed ratio. The controlling system uses pressure transmitter to really test the general pressure head and uses the differential–pressure transmitter to test the stock level. After relevant coupling technology treatment according to the set value of the general pressure head and stock level height and stock level value really tested, the computer gives out the control signal(s) (4-20mA DC) and the pulp-distributing Fan pump frequency converter and Roots blower’s one separately controls the stock approach quantity and air-blast one to keep the stock jet speed from head-box lip-opening stably the same as the wire speed.

B: PIC- general pressure head control of head box

• EJA flange differential pressure transmitter;
• PLC regulating loop and AI & A0 interface circuit;
• Pulp distributing Fan pump VFD (Supplied by Customer)

C: LIC- level control of head box

• EJA flange-type level transmitters;
• PLC regulating loop and AI-A0 interface circuit;
• Roots blower

D: Control Accuracy

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