Paper machine headbox pressure


Harman, Jr. Shannon, Cleveland. It has been established that preferably the spouting velocity, that is the rate of discharge of stock from the headbox, should be properly correlated with the velocity of the traveling screen in order to produce a satisfactory web. If the spouting velocity deviates substantially from that of the screen poor paper formation may result or a web having undesirable variations in thickness may be formed.

As the velocity of the screen is adjusted from time to time, in response to observations and measurements made on the web or finished paper, and further as the velocity of the screen will vary with changes in voltage, frequency and the like of the drive motors for the screen it follows that corresponding and immediate changes should be made in the headbox spouting velocity. Heretofore as taught by Eastwood in United States Patent 3, and by De Mers in United States Patent 1,93 6, correlation between screen velocity and spouting velocity may be obtained by varying the level of stock in the headbox.

The advent of the pressurized headbox, however, that is a headbox wherein a pad of compressed air is maintained above the level of stock, while permitting higher spouting velocities and hence higher machine speeds, has presented a new control problem. Accordingly, it is an object of this invention to provide a control for a paper machine headbox of the pressurized type.

It is a further object to provide a pressurized headbox control wherein the spouting velocity of the stock immediately and in proper proportion follows variations in speed of the traveling screen. It is another object of this invention to provide a pressurized hcadbox control wherein the level of stock in the headbox is maintained at a predetermined desired value, hence assisting in the maintenance of a spouting stock of uniform mixture and quality.

Still another object is to provide a pressurized headbox control which while reacting instantaneously to changes in machine speed is stable in operation, produces the desired results without cycling, causing neither fluctuations in the quality of the spouting stock, nor undesired fluctuations in the rate of stock fed to the headbox.

These and other objects will be apparent from the de scription to follow and from the drawings in which:. Referring now to FIG. The screen 3 is provided with the usual breast roll 4 and a couch roll 5 located at opposite ends of the screen, the latter being driven by any suitable means such as an electric motor or the like not shown.

Below the screen 3 is a pit 6 for receiving the water drained from the stock white water which is recycled through a conduit 7 to the stock supply system.

Feedstock is supplied the headbox 1 by means of a fan pump 8 through a conduit 9. Makeup stock is introduced into the stock supply system through a conduit We have shown in conduits 7 and 10 valves 11 and 12 respectively as representative of any conventional means, manual or automatic, for maintaining a desired ratio between recycled white water and makeup stock. Compressed air from any suitable source not shown is introduced into the headbox through a conduit 13 to pressurize the headbox and maintain an air pad above the level of stock.

The velocity of the stock spouting from the orifice 2 may be varied by prilex daphne the differential pressure across the orfice. This differential pressure is equal to the total head within the headbox, that is the head produced by the weight of stock above the. Conveniently, therefore, the spouting velocity can be varied by varying the pressure of the air pad and to accomplish this we show in conduit 13 valves 14 and 15, the valve 14 controlling the supply of compressed air to the headbox and the valve 15 controlling the air wasted therefrom to the atmosphere.

Any desired air pressure may be maintained by proper adjustment of valves 14 and It is evident that as the spouting velocity of stock through the orifice tube varies so must the supply of stock to the headbox vary to maintain a desired level of stock within the headbox. We accordingly show as representative of a suitable control means for the stock input a valve 16 disposed in the conduit 9.

As evident flow control of the feedstock could also be obtained, if desired, by varying the speed of pump 8 solely or in combination with adjustment of valve As this description is addressed to those skilled in the art we have purposely, in FIG. In FIG. Measuring instruments and final control elements shown in FIG. While in FIG. Therein we show a transmitter 17 responsive to the diiferential across the orifice 2, or in other words, responsive to the total head within the headbox 1, which establishes a pneumatic loading pressure proportional to the differential.

This loading pressure is transmitted through relays 21 and 18 to valves 14 and 15 arranged to operate in opposite directions. Thus as the pressure established by transmitter 17 increases indicating an increase in total head, theoutput pressure of relay 18 will decrease proportionally causing valve 14 to move in a closing direction and valve 15 to move in an opening direction to thereby decrease the pressure of the air pad.

The relay 18 may be of the type described in Panich United States Patent 2, and is preferably of the socalled proportional plus reset type incorporating a proportional band adjustment and having automatic adjustable reset.How to measure the quality and performance of a papermachine headbox. The main task of a papermachine PM headbox is to distribute fibers and fillers from the feeded suspension as uniform as possible on top of a running conveyor wire in view of time machine direction, MD and in view of localisation cross machine direction, CD.

Even there is a very well performing PM headbox, the basis weight distribution of paper is influenced from other parts of the papermachine as well. Pressure variations from the constant part of PM could generate flow variations of the jet from the headbox finally. Although headboxes are able to reduce such pressure variations from the constant part very well, - and could be demonstrated with BTF-System - this pressure variations will result in variation of mass distribution on the running wire.

It should be mentioned the different principles of headbox design of BTF and others. Conventional headboxes with CD flow spreaders will generate from variation of flow variation of mass distribution in CD and MD in the same time, which is a very unsufficient situation.

Paper Mill Machinery

But the wire itself and all the other dewatering devices will influence the initial mass distribution on the wire. Hopefully a more or less uniform mass distribution could be kept during a uniform filtration process and will not going worse.

Non uniform abrasion or insufficient tension and stretching of the wire or wrong adjusted dewatering elements as foils and suction boxes may influence the mass distribution in cross machine direction. If there is enough data from measuring basis weight avaible, statistics could help to carry out the effect of mass distribution and its reasons.

The most important tool to rectify the performance of a papermachine as a total system is analysis of variance of basis weight distribution in paper. To do this, there is the need of about 20 paper samples from the top of the produced paper reel as long as the trim of the papermachine is. Sometimes samples are simply called profiles and from this stripes of paper the basis weight should be measured on a small area. The two dimensional analysis of variance is able to separate the total variation into three parts.

There are systematic variation in mashine direction and systematic variation in cross mashine direction and non systematic residual variation. As mentioned above and surching for reasons of such variation, MD variation could be supposed generated by the constant part or poor condition of the wire part.

CD variation is mainly generated from the headbox or flow approach system. Sometimes the already described MD and CD variation are called systematic errors and they could be eliminated on principle or reduced in reality by elimination of the corresponding defects in the papermachine.

If all systematic variation is eliminated, there are still the non systematic residual or stochastic variations. In the view of the author, this residual variation is a measurement to characterize the performance of a paper production unit. But this is only true if the systematic CD and MD variations are eliminated in fact. There are other statistical and number screening tools avaible to analyze systematic variations in CD and MD direction and to find the reasons.

Some of this methods are looking on the time series of basis weigt figures and try to find out variations, which could be constructed by overlapping variations of special frequencies and amplitudes. For example it is possible to get from such an analyze a tracable variation of mass distribution significant amplitudes with a special frequency and the problem is nor far beyond to be solved.

The most frequent and significant basis weight variation with frequency about 20 Hertz is caused nearly always from the rotor of the screens in front of the headbox. The rotating wings of the rotor are covering the main outlet of the screen periodically and this generate variations in pressure and flow to the headbox gas mask list could be found as periodic basis weight variations in the paper.

That is the reason, why BTF-Systems are carefully designed in aspect of mechanical and hydraulic vibrations. The BTF distribution tank with a perforated plate and suitable design is one of the most performing unit to reduce hydraulic variation from the constant part and the special perforated plate converts the non desired vibrations to micro turbulences, just wright to provide floculation of the suspension.

Within the BTF-System the forming unit takes care of the uniform distribution of the fiber containing suspension in cross machine direction.TT AFS. It can be operated with a wide range of raw materials from virgin fibers to recycled paper. The screening effect of the Toscotec Pressure Screen TT AFS is excellent thanks to the centrifugal action of the multi-foil rotor that has a special shape engineered to enhance de-flocculation and contaminants separation while at the same time reducing fractionation and pressure pulsations to a minimum.

Rotor clearance can be easily adjusted and it is possible to quickly replace the foils. The basket is profiled and electro-polished as standard; it can be drilled or slotted. It additionally can be chromium plated. The seal can be single or double mechanical type. Basket, rotor and seal are customized to fulfil requirements of each different application. The internal flow through the screen body have been studied with Computational Fluid Zerotier 443 CFD in order to have constant speed through the basket in all zones from inlet to accept, to get an optimal velocity difference between stock rotation and flow.

Screen body internal surfaces are electro-polished. A vent on the top of the machine helps to de-aerate the stock. Electrical power consumption is very low and pressure drops are minimized. Several units can be installed on the same machine in a cascading configuration. Tail screen can be equipped with heavy rejects junk trap. The Toscotec Vibrating Screen TT V can be used as final stage for rejects de-watering after other screens such as vortiscreens, superscreens and pressure screens.

TT SAF. Toscotec Short Approach Flow TT SAF, patented by Toscotec sinceallows every mill, new or existing one, to reduce energy consumptions and installation space, without compromises in terms of performances. TT MBP. TT RS. The Toscotec Rotating Screen TT RS is used in recycled paper stock preparation plants to de-water the coarse rejects coming from upstream cleaning equipment.

TT RG. For the proper performance of a continuous pulper working with recycled paper Toscotec Low Density Pulpera cleaning unit such as the ragger TT RG is required to be installed. TT TM. Optimized to work with heavily contaminated recycled paper or with rewinder trims, the Toscotec Low Density Pulper TT TM is designed to perform an extremely efficient and low energy slushing in continuous mode and to remove rejects without breaking them.

TT VP. Suitable to work both with virgin pulp, broke, recycled paper and non-wood fibers, the Toscotec Medium Density pulper TT VP is designed to perform an extremely efficient and low energy slushing in discontinuous mode.

TT TMC. TT VS The Toscotec Vortiscreen TT VS-3 can be installed as the only coarse screen in converting broke lines or as the last tail screening stage for the treatment of the rejects coming from drilled Toscotec Superscreens in recycled paper processing lines. The Toscotec Vortiscreen TT VS-1 is used in recycled paper stock preparation plants mainly for the detrashing of the continuous TM Pulpers and as a dumping machine of high consistency batch pulpers. TT SS.Air Cushion type headbox can increase the sizing pressure to meet the requirements of medium and high speed paper machines.

US3171775A - Distributor system for a paper machine headbox - Google Patents

The headbox consists of square taper tube device, evener roll device, top lip plate adjusting device, box body,control system, spraying device, air path system, etc. The headbox is designed with customer performance parameters, which can ensure work performance.

Headbox is used for sizing in fourdrinier wire section of paper making machine for producing cardboard paper, corrugated base paper, writing and printing paper, offset paper and so on.

It can be used to produce the paper sheet with uniform and stable quantity, and there is no longitudinal flow on the web. The lip area of headbox should not be affected by pressure, temperature and opening degree of the lip to ensure the uniform distribution of the width. The ratio of jet to wire speed is controllable. Method to protect doctor blade. Dryer cylinder export to europe.

Share to:. Paper Machine Air Cushion type headbox Air Cushion type headbox can increase the sizing pressure to meet the requirements of medium and high speed paper machines. Inquire Add to Basket. Product Description Air Cushion Headbox Air Cushion type headbox can increase the sizing pressure to meet the requirements of medium and high speed paper machines. Air Cushion Headbox Air Cushion type headbox can increase the sizing pressure to meet the requirements of medium and high speed paper machines.

Product Search. Product Category. Related Products. Paper Machine hydraulic type headbox. Paper Machine open type headbox. Ceramic dewatering element for paper machine. Paper Machine Rubber Press Roll. Paper Machine Groove Press Roll.

Paper Machine Spray Shower System. Paper Machine Dryer Cylinder Turbulator bars. Dryer Cylinder Steam Rotary joint.

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Headbox Pressure measurement in the headbox. Measuring task:. Application The paper suspension is pumped into the headbox of the paper machine. Via the hydraulically pressurized headbox it passes through a tapered cross-flow distributor and manifold, through the rectangular discharge opening, or slice, onto the screen. The outflow speed of the suspension is adjusted to match the speed of the screen by adjusting the pressure of the headbox feed pump.

This means an accurate pressure measurement, with minimal turbulence created in the headbox is vital at this part of the process. Your benefit Reliable. Cost effective. Measuring range - Distance. Measuring range - Pressure.JavaScript is disabled for your browser.

Efficient and pulsation-free headbox screening

Some features of this site may not work without it. Search Knowledge Commons. This Collection. View Usage Statistics. Modeling and control of various styles of paper machine headboxes. Author Facca, Angelo G. Degree Master of Science.

ModuScreen HBE

Subject Papermaking machinery Automatic control Headbox. Metadata Show full item record. Abstract In this thesis non-linear mathematical models of a typical paper machine approach system with three different styles of headboxes are presented.

The non-linear models include the dynamics of the fan pump, DC motor, pressure screen, attenuator, headbox and piping sections. Headbox models of a hydraulic and two air-cushioned headboxes traditional and internal weir are covered. The models were developed from first principles. Total head at the headbox slice is controlled by manipulation of the applied armature voltage of the variable speed DC motor. Stock level in the air-cushioned headboxes is controlled by manipulation of the air pad bleed valve.

Simple analog Proportional-Integral PI controllers were selected to track without offset the desired level and total head set-points. The downhill simplex method developed by Nelder and Mead was used for controller fine-tuning. The performance criterion was the integrated absolute error IAE with weighting factors for both pressure and level loops. Step and frequency response plots were generated at operating points of 60, 75 and 90 kPa to evaluate the non-linear behaviour of each headbox model.

The step response plots highlighted the strong interaction that exists between level and pressure loops of the air-cushioned headboxes. With the PI gains used the transient responses of the pressure loop of all headboxes were underdamped. The open-loop frequency responses in all models illustrated the non-linearity of the centrifugal fan pump.

In addition the effect of the fan pump on the stock level and total head was found to be strong. The effect of the bleed valve on the stock level was also determined to be strong.Headbox operation in paper machine is very important as it decides the quality of the paper by uniform supply of the stock in forming section across the width of the wire section. The new generation of control system, integrates the operation of headbox with VFD and PLC system and improves the performance of paper machine and quality of paper at the reel.

The essential requirement is pressure and level control with respect to speed of the machine and jet velocity ratio. Pressure is controlled through regulation of root blower speed through VFD and level is controlled through regulation of fan pump speed through VFD. Our automation system provides control of machine speed or fix jet velocity ratio. The papermaking stock pumped in a pipe is converted to a uniform rectangular flow with absolutely the same flow rate and flow direction across the wire width.

Papermakers adjust the jet-to-wire speed difference to fine-tune the paper structure. Jet velocity is governed by Headbox pressure. The jet is the narrow stream of papermaking furnish that comes out of the slice opening from the Headbox. Level, Pressure. Mail: info amtechelectronics. Login Sign Up. Prev Next. Forgot Password Enter Your Email :.

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Subscribe Archive Newsletter. All Rights Reserved. User Login Form. Username :. Password :. Forgot Your Password? Forgot Password. Enter Your Email :. Paper machines operating above ft/min require a special, high pressure headbox known as a hydraulic headbox. These headboxes do not use rectifier rolls. multi-variate non-linear process in a paper machine called the headbox.

complicated and in order to achieve the same pressure in every width section the. The paper machine headbox is an equipment that supply very low consistency stock into the forming section uniformly. Keywords: Paper machine, Headbox, Pressure/Stock Level, Headbox Consistency, Mathematical Modeling. 1. Introduction. The first ever paper was invented in. pressure along the cross machine direction.

A recirculation valve is Flow stabilization in headbox improves paper formation. The headbox slice is also. The paper suspension is pumped into the headbox of the paper machine. Via the hydraulically pressurized headbox it passes through a tapered cross-flow. Conveniently, therefore, the spouting velocity can be varied by varying the pressure of the air pad and to accomplish this we show in conduit 13 valves 14 and.

Machine-directional streaks in paper are often due to wake effects, possibly originating at the slice of the paper machine headbox.

If so, the streaks have to. Hydraulic headbox (high speed): for paper machines with speeds up to m/min. It can control the edge flow of directional distribution of fiber banners.

A HEADBOX OF A MACHINE PRODUCING A FIBROUS SHEET HAS A SLICE OPENING CONTROLLED IN Sensors of the total head and air pressure within the headbox derive. Flow nozzles· may 'be classified into two main types: metro boxing club. Flow nozzles where the stock velocity at the slice is created in a small pond by air pressure where the. should only be used in comparisons for one paper machine when no changes of Pressure pulses in hydraulic headboxes are detrimental to fourdrinier de.

Correct landing of the jet from the headbox onto the forming fabric is essential high-speed paper machines, the empirical process is hampered by.

Double Layer Test Liner Paper Machine

headbox: the pressure chamber where turbulence is applied to break up fiber clumps in the slurry. The main job of the headbox is to distribute the fiber slurry. Paper Machine Clothing · Second Edition | Pressure pulses (headbox, pressure screens, and stock delivery system). Cockling. • Poor formation.

Valmet headbox family comprises an optimal selection of paper machine headboxes to meet various production requirements in paper and board making. The Slice opening together with the head box pressure determines the volume In Practice, the L/B ratio on a paper machine varies in the range between. Multi-tube bundle, dilution water system: the actual operation of the regulation of quantitative banners; balance room: attenuation of pressure.

The non-linear models include the dynamics of the fan pump, DC motor, pressure screen, attenuator, headbox and piping sections. Headbox models of a hydraulic. Global Equipment International, LLC. buys and sells paper machine components One (1) used Escher Wyss Headbox with pressure equalizing chamber.