US3779863A - Stock flow control system for feeding a paper machine headbox - Google Patents

Stock flow control system for feeding a paper machine headbox Download PDF

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Publication number
US3779863A
US3779863A US00010713A US3779863DA US3779863A US 3779863 A US3779863 A US 3779863A US 00010713 A US00010713 A US 00010713A US 3779863D A US3779863D A US 3779863DA US 3779863 A US3779863 A US 3779863A
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stock
pump
pressure
speed
orifice
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US00010713A
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English (en)
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D Wahren
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ABB Norden Holding AB
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ASEA AB
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/06—Regulating pulp flow

Definitions

  • ABSTRACT Stock feed to a paper machine headbox is controlled by a stock (fan) pump which is controlled to run at variable speeds, the input of stock to the pump originating from a thick stock containing conduit and a conduit containing mixing water.
  • the speed of the pump motor is controlled by a signal from a control element which is responsive to measurements of the stock level or pressure within the headbox and an adjusted value of the forming wire speed.
  • a thick stock pump located in the thick stock conduit is adjusted to run at a variable speed by a control device which is responsive to signals indicating the pressure drop across an orifice in the thick stock conduit and a signal based on the web speed.
  • the thick stock pump may run at a constant speed and the control device can be used to control an orifice opening or throttling device located in thethick stock conduit between the pressure-drop determining orifice and the stock (fan) pump.
  • the invention presented here refers to an arrangement for stock proportioning of paper machines, comprising a thick stock pump for feeding pulp to the system, which feeds a headbox system, from which stock is delivered on to a wire or wet felt.
  • a system consists of a white-water chest, fan (mixture) pump, piping and, possibly, cleaning devices as well as a headbox, from which the stock suspension diluted with whitewater is uniformly distributed over the width of the machine on a wire or wet felt.
  • FIG. 1 A usual arrangement for such stock proportioning is shown in FIG. 1, and comprises a level box 1 provided with an overflow (by the arrow 2) or some other form of lever control, arranged at a certain height over a proportioning point 3, where the driving pressure for the thick stock flow is determined by the difference between levels in the levelbox-and white-water chest.
  • Water for example, previously used water (white-water, arrow 4) is fed to the proportioning point 3, and thick stock is pumped to a levelbox (at 5).
  • the incoming thick stock flow is controlled by means of a manual or automatic, for example, computer-controlled, valve 6.
  • the accuracy requirement means that the levelbox must normally be set up at a height of 4-8m over the white-water level so as to obtain the necessary pressure drop across the basis-weight valve.
  • This system will consequently take up considerable space and will be expensive in view of the piping involved etc. This may lead to disturbances, varying degree of blocking up of the valve owing to the low pressure drop available. Setting up of the levelbox at a considerable height over the proportioning position will require a higher building (insulation, etc.) which can seldom be accomplished. In such a system the influence of friction in pipes may be aggravated and, furthermore, changes in the properties of the stock, for exam ple, beating degree, temperature or degree of cooking, cannot be simply measured or calculated. This means that difficulties may arise with automatic control of the basis-weight valve.
  • the demand imposed on flowmeters can be expressed in such a way that their measuring accuracy must be considerably better than the spontaneous flow fluctuations, which the flow control is intended to reduce on the basis of signals from these instruments.
  • An acceptable value of the variations between the maximum and the minimum values of the moisture content may be i 0.5 percent, which means that corresponding variations for the stock flow must be less than :t 0.25 percent, i.e., a value that is difficult to achieve with conventional instruments of the magnetic flow-meter type.
  • the invention presented here refers to an arrangement for solving the above-mentioned and other problems and is of the type mentioned in the first paragraph of this application.
  • the main feature of this is that an orifice is arranged in the stock line to the headbox. The pressure drop across this orifice is measured and the stock flow is controlled on a desired value for this pressure drop, which is usually proportional to the square of the web (wire) speed.
  • FIG. 2 shows the basic principle of this invention.
  • the pressure drop across the orifice is measured in the normal way for such devices, and the signal for this pressure drop is fed to a control device 19 for the prime mover 21 driving the thick stock pump 17.
  • the prime mover 21 may be a dc. motor controlled by an S.C.R. converter or by some other similar means, but it may also be an a.c.
  • the signal (at 20) gives the actual value of the pressure drop across the orifice 18 and the speed of the motor (21) is controlled on a desired value, which is determined by the machine speed and possibly also the basis-weight as described below.
  • the speed control of motor 21 can be replaced by a motor intended to run at constant speed and supplemented by an extra orifice 22 for the thick stock flow.
  • This orifice is adjustable and, when its setting is changed, it alters the the pressure drop across the orifice 18.
  • this system has the advantage in both these cases that, besides there being hardly any air admixture in the stock (unlike the case where free liquid surfaces occur or an overflow is used, see the FIG. 1), the lines 23 can be arranged vertically, which prevents the accumulation of air normally occurring with descending pulp flows.
  • the speed at the end of the web is measured with a tacho-generator 38, whose output signal is squared in a squaring element 39.
  • the output signal of the latter in its turn will be proportional to the square of the web speed.
  • a suitable pulp proportioning, for example, suitable basisweight is set with a proportionalizing element such as a potentiometer 29, and this proportioning (basisweight) signal 30 is fed to the control element 19 an will constitute the desired value for the pressure drop across the orifice 18. This value is thus adjusted for altered motor speed (at 21) or altered throttling (at 22) and therefore altered proportioning (of stock to the paper machine).
  • the desired-value signal 30 will therefore be proportional to the square of the web speed (v and is thus altered as the machine speed changes.
  • the speed of the wire 11 (not exactly the same as v) is measured in a suitable manner by means of a tachogenerator 24 or by some other conventional means at the drive 25 of the wire.
  • This measuring element gives 26 a signal proportional to the wire speed (v,) at 11.
  • This signal 26 is fed to a squaring element 27, whose out-put signal is therefore proportional to the square of the speed (v,).
  • the v, signal can also be taken out across another proportionalizing element 31, for example, a potentiometer, which is set to a desired value of the square of the slice outflow quotient 4: i.e., the desired ratio between the slice outflow velocity and the wire speed.
  • a desired value for these quantities can be obtained from the pressure or level signals in the headbox, which are measured at 32 and 33 and added in the control element 34 with the desired value (from 31) to form an error signal, which is used for controlling the drive 35 of a stock pump 13 for controlling the desired slice outflow pressure (arrow 36) or outflow quotient.
  • An altered web speed thus also results here in an altered desired value and thus changing of the pump speed.
  • D is the diameter of the measuring element in m and p. the dynamic viscosity (kg/m/s).
  • the pressure value across the orifice 18 can also be controlled on a value proportional to the total-head in the headbox, comprising fluid (stock) pressure plus pressure of any air cushion, plus possibly a negative pressure addition for vacuum running at low speeds.
  • the flow measurement can also be accomplished indirectly by measurement of the head of pump 17 and the pump speed (at 21) and combining of these values. Examples according to the above can be varied in different ways within the framework of the following patent claims.
  • Device for proportioning the pulp suspension for paper machines comprising feed conduits for pumping pulp and water to a mixture pump for pumping pulp mixed with water (stock) to a headbox, from which (headbox) the stock is delivered to a wire for further transport of stock, the driving means of the mixture pump being controlled from a control element responsive to signals from a measuring means within the headbox measuring the level or pressure in the same and to signals from means responsive to the wire speed, one of said conduits being a pulp conduit provided with a thick stock pump for pumping pulp to said mixture pump to be mixed with water from another of said conduits before said mixture pump, in said pulp conduit being arranged an orifice for obtaining a pressure drop and means for measuring said pressure drop and control means for controlling the driving means for said thick stock pump, a reference value for desired basis weight for the suspension being obtained in reference means responsive to the produced web speed, the output of which means is fed to the input of the control means of the thick stock pump together with the output from the pressure drop measuring means, the difference between pressure drop and reference values controlling the feeding rate of
  • control means are connected to another orifice in the pulp line between the pumps which orifice is provided with means for altering the through-flow.
  • Device including a reference device for stock pressure in the headbox, the measuring cushions and possibly plus a negative pressure addition for vacuum running at low speeds, the output signals of said measuring means and reference means together forming an error signal which is fed to the control means in the headbox measuring the stock pressure in 5 means of the driving means for the mixture pump.

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US00010713A 1969-02-18 1970-02-12 Stock flow control system for feeding a paper machine headbox Expired - Lifetime US3779863A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE2196/69A SE345295B (it) 1969-02-18 1969-02-18

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US3779863A true US3779863A (en) 1973-12-18

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US (1) US3779863A (it)
DE (1) DE2007082C3 (it)
FI (1) FI51384C (it)
GB (1) GB1290942A (it)
SE (1) SE345295B (it)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4086130A (en) * 1976-07-16 1978-04-25 Beloit Corporation Control system and method for a multi-channel paper machine distributor
US4146425A (en) * 1974-10-02 1979-03-27 Sulzer Brothers Limited Papermaking machine headbox having a feed channel and an adjacent overflow sump
US5611891A (en) * 1995-12-08 1997-03-18 Westvaco Corporation System and method for controlling papermaking stock consistency
US5709777A (en) * 1993-07-05 1998-01-20 J.M. Voith Gmbh Device and method for the non-clogging throttling of a fluid stream of suspended matter
US6733629B1 (en) * 1999-08-23 2004-05-11 Andritz Oy Method of controlling the operation of an approach system of a paper machine or the like web formation apparatus

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ZA823543B (en) * 1981-06-19 1983-04-27 Albany Int Corp Vacuum control system for dewatering a web of paper
US4398996A (en) * 1981-06-19 1983-08-16 Albany International Corp. Vacuum control system and method for dewatering fabrics
DE3206200C1 (de) * 1982-02-20 1983-06-01 Badische Karton- Und Pappenfabrik Zweigwerk Der Herzberger Papierfabrik Ludwig Osthushenrich Gmbh & Co Kg, 7562 Gernsbach Verfahren zur Regelung der Stoffdichte in einem Stoffloeser

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2571219A (en) * 1950-05-17 1951-10-16 Cew Judson A De Deaeration of paper making fibers
US2847913A (en) * 1956-02-07 1958-08-19 Rice Barton Corp Stock inlet system for a paper making machine
US3077924A (en) * 1957-04-22 1963-02-19 Spruce Falls Power & Paper Co Paper making system
US3206917A (en) * 1961-10-04 1965-09-21 Clark & Vicario Corp Deaerated stock flow control
US3271241A (en) * 1962-12-10 1966-09-06 Kimberly Clark Co Stock supply system for papermaking machines including control of stock consistency and stock flow
US3293120A (en) * 1964-07-29 1966-12-20 Bailey Meter Co Paper machine pressurized headbox control of stock flow
US3562104A (en) * 1967-04-14 1971-02-09 Beloit Corp Stock flow control system for a headbox

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2571219A (en) * 1950-05-17 1951-10-16 Cew Judson A De Deaeration of paper making fibers
US2847913A (en) * 1956-02-07 1958-08-19 Rice Barton Corp Stock inlet system for a paper making machine
US3077924A (en) * 1957-04-22 1963-02-19 Spruce Falls Power & Paper Co Paper making system
US3206917A (en) * 1961-10-04 1965-09-21 Clark & Vicario Corp Deaerated stock flow control
US3271241A (en) * 1962-12-10 1966-09-06 Kimberly Clark Co Stock supply system for papermaking machines including control of stock consistency and stock flow
US3293120A (en) * 1964-07-29 1966-12-20 Bailey Meter Co Paper machine pressurized headbox control of stock flow
US3562104A (en) * 1967-04-14 1971-02-09 Beloit Corp Stock flow control system for a headbox

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4146425A (en) * 1974-10-02 1979-03-27 Sulzer Brothers Limited Papermaking machine headbox having a feed channel and an adjacent overflow sump
US4086130A (en) * 1976-07-16 1978-04-25 Beloit Corporation Control system and method for a multi-channel paper machine distributor
US5709777A (en) * 1993-07-05 1998-01-20 J.M. Voith Gmbh Device and method for the non-clogging throttling of a fluid stream of suspended matter
US5611891A (en) * 1995-12-08 1997-03-18 Westvaco Corporation System and method for controlling papermaking stock consistency
US6733629B1 (en) * 1999-08-23 2004-05-11 Andritz Oy Method of controlling the operation of an approach system of a paper machine or the like web formation apparatus

Also Published As

Publication number Publication date
FI51384B (it) 1976-08-31
FI51384C (fi) 1976-12-10
SE345295B (it) 1972-05-23
DE2007082A1 (de) 1970-11-26
DE2007082B2 (de) 1975-02-20
DE2007082C3 (de) 1975-09-25
GB1290942A (it) 1972-09-27

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