US3926719A - Dry line controller - Google Patents

Dry line controller Download PDF

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Publication number
US3926719A
US3926719A US220635A US22063572A US3926719A US 3926719 A US3926719 A US 3926719A US 220635 A US220635 A US 220635A US 22063572 A US22063572 A US 22063572A US 3926719 A US3926719 A US 3926719A
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United States
Prior art keywords
wire
change
basis weight
dry basis
bone dry
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US220635A
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English (en)
Inventor
David A Spitz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Industrial Nucleonics Corp
ABB Automation Inc
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Industrial Nucleonics Corp
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Publication date
Application filed by Industrial Nucleonics Corp filed Critical Industrial Nucleonics Corp
Priority to US220635A priority Critical patent/US3926719A/en
Priority to CA155,655A priority patent/CA975203A/en
Priority to JP48010610A priority patent/JPS4882104A/ja
Application granted granted Critical
Publication of US3926719A publication Critical patent/US3926719A/en
Assigned to PROCESS AUTOMATION BUSINESS INC., reassignment PROCESS AUTOMATION BUSINESS INC., CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). EFFECTIVE 02/17/88 Assignors: ACCURAY CORPORATION
Assigned to ACCURAY CORPORATION reassignment ACCURAY CORPORATION CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). EFFECTIVE: 07/02/79 Assignors: ACCURAY LEASING CORPORATION
Anticipated expiration legal-status Critical
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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
    • 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
    • D21F1/08—Regulating consistency
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F7/00—Other details of machines for making continuous webs of paper
    • D21F7/003—Indicating or regulating the moisture content of the layer

Definitions

  • Patent D MOTOR SPEED CONTROL FBSG BSPG c VFPG vos'Ta VDSB VFPG FBSG BSPG
  • the present invention relates generally to Fourdri- 5 nier machines, and more particularly, to a Fourdrinier machine wherein dry line position is controlled in response to indications of bone dry basis weight of a fibrous product formed by the machine and the speed of a Fourdrinier wire.
  • a Fourdrinier machine for making a fibrous sheet product, such as paper, from a fiber water slurry
  • the slurry spouts from a headbox to a moving Fourdrinier wire.
  • the slurry while on the wire, dries in response to drainage through the wire. Drainage is in response to suction provided beneath the wire by table rolls.
  • a dandy roller is positioned toward the end of the Fourdrinier wire.
  • the dry line occurs at a location such that the mat is excessively wet when it engages the dandy roll, the dandy roll alters fiber formation of the matv Because of these factors, it is desirable to control the position of the dry line on the Fourdrinier wire.
  • the dry line has a tendency to remain at a relatively fixed location.
  • the position of the line has a tendency to vary, however, from one location to another when a grade change of the fibrous product formed by the wire is commanded.
  • the dry line position may also vary significantly during non-grade change operation, if substantial changes in bone dry basis weight of the fibrous product and/or wire speed are commanded.
  • Water drainage is a direct function of wire speed because wire speed is related to the degree of vacuum placed on the bottom surface of the mat by table rolls located beneath the Fourdrinier wire. The greater the speed of the wire. the greater the vacuum exerted by the table rolls, to increase drainage. While wire speed also affects total drainage from the wire because of its effect on the time the mat is on the wire, this is a secondary effect that is much less significant than the primary wire speed effect on table roll vacuum.
  • each step of the stream fiow is computed in accordance with the present invention as:
  • QWSI-I stream flow set point prior to the change i.e. for a grade change, the set point for the grade being formed before the grade change began
  • COVG a constant determined from a theoretically derived curve fit of the vacuum profile between the table rolls and wire, as a function of wire velocity.
  • COBG a constant determined from a theoretically derived curve fit of the vacuum profile between the table rolls and the wire. as a function of bone dry basis weight.
  • Equation l is valid only if a refiner feeding thick stock into the machine is operating in the same condition before the grade change as after. If the refiner operation is altered in conjunction with grade change, the alteration should be performed after the remainder of the grade change operations have been performed. In response to alterations of the refiner operation, the operator maintains the dry line position substantially constant by manually controlling stream flow to the headbox until the dry line returns to its initial location.
  • an object of the present invention to provide a new and improved system for and method of controlling dry line position.
  • Another object of the invention is to provide a new and improved system for and method of maintaining the position of a dry line at substantially the same location after a substantial change in a property of a fibrous sheet product has been effected as before the change.
  • Another object of the present invention is to provide a new and improved system and process for maintaining the position of a dry line at substantially the same location after a grade change has been performed as before the change.
  • Another object of the invention is to provide a system for and method of automatically maintaining a dry line position substantially constant by utilizing virtually identical analytic approaches with many different fibrous sheet producing machines.
  • FIGURE is a schematic diagram of a preferred embodiment of the invention.
  • FIGURE wherein a thick slurry of water and fiber is fed by source ll, which may be a paper making refiner, to headbox 12 via conduits l3 and 14, between which is connected pump 15.
  • source ll which may be a paper making refiner
  • the fiber-water slurry in headbox l2 spouts from slice [6 thereof onto moving Fourdrinier wire 17.
  • Beneath Fourdrinier wire 17 are table rolls l8 and flat boxes 18a which provide a vacuum or sunction effect on the lower surface of wire 17 to provide drainage for the mat of fiber and water formed on the upper surface of wire 17.
  • Toward the end of wire 17 remote from slice 16 is dandy roll 19.
  • White water drained from wire 17 is caught in pit 21 and fed back, via pipe 22, pump 15, and conduit 14, to the inlet of headbox 12.
  • the white water in conduit 22 dilutes the thick slurry fed to pump by conduit 13.
  • Flow of fluid in pipe 14, and therefore steady state flow from slice 16 to wire 17, termed the stream flow, is controlled by valve 23 in line 14.
  • the flow of thick stock in conduit 13, which determines the bone dry basis weight, i.e.. fiber weight per unit area. of the sheet formed by wire 17, is controlled by valve 24 in line 13.
  • Valves 23 and 24 are respectively driven by actuators 25 and 26 to set point values commensurate with desired stream flow and bone dry basis weight for a particular grade.
  • flow meters 27 and 28 are provided in lines 13 and 14. If the flow meters are not used, the positions of the valves may be used to alternatively provide flow indications.
  • Flow meters 27 and 28 derive signals which are compared with set point sig nals for the flows in conduits 13 and 14 in subtracting nodes 29 and 30, respectively. Difference output signals derived from nodes 29 and 30 are fed to actuators 26 and 25, respectively, to provide negative feedback loops.
  • Wire 17 is driven by motor 32 at a forward speed determined by a set point signal fed to motor speed control circuit 33.
  • the set point input signals for node 29 and motor speed controller 33 are derived by general purpose digital computer 34 in a manner indicated in the previously referenced Rice application.
  • the set point signal for node 30 is derived by computer 34 in accordance with the present invention.
  • Computer 34 responds to grade indicating input signals to derive the various set points. During a grade change, the various set points are changed incrementally, i.e., in steps, by computer 34 as trajectories for controlling valves 23 and 24, as well as motor 32. The number of steps required for a particular grade change is determined by computer 34 as described in the referenced Rice application.
  • computer 34 responds to signals stored in the memory thereof to determine the values of: QWSH, TGKG, FBSG, BSPG, VFPG, and VDSB, where:
  • QWSH stream flow set point prior to the change i.e., the set point for the grade being previously formed
  • F BSG the bone dry basis weight set point for the grade being formed prior to the change. as stored in memory
  • BSPG bone dry basis weight set point subsequent to the change i.e.. bone dry basis weight for the grade of paper after the grade change has been completed
  • VDSB wire speed set point prior to the grade change
  • the change in stream flow, DQWG, during each step of the grade change is determined by computer 34 in accordance with Equation l supra.
  • the computer 34 is programmed in a manner well known to those skilled in the art to solve the equation.
  • the values of DQWG increment the previous value for the set point of valve 23 in the computer so that a trajectory of values QWKG for valve 23 is fed by computer 34 to node 30 during grade change.
  • the value of QWKG during the lth step of a grade change having TGKG steps is:
  • QwKG hD0wo+QwsH (21.
  • the computer successively feeds each of the incremented QWKG values of stream flow set point to node 30. Concomitantly with the feeding of incremented stream flow set point values to node 30, computer 34 feeds incremental values for the set points of thick stock flow and motor speed to node 29 and motor speed control 33.
  • Equation l From Equation l it is seen that if the speed of wire 17 is not changed from the beginning to the completion of a grade change and if there is no change in the bone dry basis weight of the sheet formed on wire 17 from the beginning to the end of the grade change, there is no change in the flow of slurry fed by conduit 14 to headbox 12. Relative changes in the speed of wire 17 from the beginning to the end of a grade change have a greater effect on changes of stream flow than relative changes in bone dry basis weight because of the higher value of the COVG coefficient than the COBG coefficient.
  • Equation I. can be tuned by first observing its effect on the dry line position during speed changes, adjusting COVG, then observing its effect on the dry line position during grade change and adjusting COBG. If, during a speed increase, the dry line moves upstream, COVG should be increased. Once COVG has been set, dry line change with a basis weight change and small speed change should be observed. if the basis weight increases, and the dry line moves upstream, COBG should be decreased. The new values of COBG and COVG are stored in the computer memory.
  • stream flow set point trajectories can be, and are preferably, calculated by computer 34 in response to the new and 6 old set point values of bone dry basis weight and/or wire speed.
  • said fibrous product being formed in response to a fiber water slurry fed to the wire and that is relatively dilute compared to the thick stock, comprising a first control for changing the fibrous product grade, said first control comprising means for deriving signals indicative of values for bone dry basis weight of the product before and after said change by said first control and indicative of values for wire speed before and after said change, said changes in bone dry basis weight and wire speed resulting in said change in the fibrous product grade, means responsive to said bone dry basis weight signals for incrementally controlling bone dry basis weight of the product, and means responsive to said wire speed signals for incrementally controlling the speed of the wire, a second control comprising means for incrementally controlling the flow rate of the fiber water slurry being fed to the wire in response to the signals indicative of the wire speed and bone dry basis weight before and
  • VDSB wire speed set point prior to the change
  • COVG a constant determined from a curve fit of the vacuum profile between the table rolls and wire, as a function of wire velocity
  • COBG a constant determined from a curve fit of the vacuum profile between the table rolls and the wire, as a function of bone dry basis weight.
  • said computing means includes means for storing signals representing the fractional powers for the bone dry basis weight and speed ratios, said signals respectively representing the values substantially equal to 0.4 and 0.8.

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US220635A 1972-01-25 1972-01-25 Dry line controller Expired - Lifetime US3926719A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US220635A US3926719A (en) 1972-01-25 1972-01-25 Dry line controller
CA155,655A CA975203A (en) 1972-01-25 1972-11-06 Paper machine dry line controller
JP48010610A JPS4882104A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1972-01-25 1973-01-25

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US220635A US3926719A (en) 1972-01-25 1972-01-25 Dry line controller

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US3926719A true US3926719A (en) 1975-12-16

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US (1) US3926719A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
JP (1) JPS4882104A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
CA (1) CA975203A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2926072A1 (de) * 1978-06-30 1980-01-10 Centre Tech Ind Papier Verfahren und vorrichtung zur prozesssteuerung der auflaufeinrichtung in der siebpartie einer papiermaschine
FR2506357A1 (fr) * 1981-05-25 1982-11-26 Asea Ab Dispositif de reglage du grammage dans des machines a papier
US4500968A (en) * 1982-06-29 1985-02-19 Domtar Inc. Paper machine wet line control
US5011573A (en) * 1986-12-30 1991-04-30 Antti Johannes Niemi Method and apparatus for control of dry-line on the wire of a fourdrinier paper machine
US5611891A (en) * 1995-12-08 1997-03-18 Westvaco Corporation System and method for controlling papermaking stock consistency

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3649444A (en) * 1969-05-15 1972-03-14 Westvaco Corp Moisture control system including control of pulp flow to a paper machine headbox in response to moisture measurement
US3676295A (en) * 1969-09-12 1972-07-11 Industrial Nucleonics Corp Noninteracting control of moisture and fiber content of fibrous sheet during manufacture
US3687802A (en) * 1970-06-22 1972-08-29 Owens Illinois Inc Controlling the moisture,mullen and basis weight of paper
US3703436A (en) * 1970-02-03 1972-11-21 Industrial Nucleonics Corp Anticipatory control of headbox slice opening in a paper machine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3649444A (en) * 1969-05-15 1972-03-14 Westvaco Corp Moisture control system including control of pulp flow to a paper machine headbox in response to moisture measurement
US3676295A (en) * 1969-09-12 1972-07-11 Industrial Nucleonics Corp Noninteracting control of moisture and fiber content of fibrous sheet during manufacture
US3703436A (en) * 1970-02-03 1972-11-21 Industrial Nucleonics Corp Anticipatory control of headbox slice opening in a paper machine
US3687802A (en) * 1970-06-22 1972-08-29 Owens Illinois Inc Controlling the moisture,mullen and basis weight of paper

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2926072A1 (de) * 1978-06-30 1980-01-10 Centre Tech Ind Papier Verfahren und vorrichtung zur prozesssteuerung der auflaufeinrichtung in der siebpartie einer papiermaschine
FR2506357A1 (fr) * 1981-05-25 1982-11-26 Asea Ab Dispositif de reglage du grammage dans des machines a papier
US4500968A (en) * 1982-06-29 1985-02-19 Domtar Inc. Paper machine wet line control
US5011573A (en) * 1986-12-30 1991-04-30 Antti Johannes Niemi Method and apparatus for control of dry-line on the wire of a fourdrinier paper machine
US5611891A (en) * 1995-12-08 1997-03-18 Westvaco Corporation System and method for controlling papermaking stock consistency

Also Published As

Publication number Publication date
CA975203A (en) 1975-09-30
JPS4882104A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1973-11-02

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Owner name: ACCURAY CORPORATION

Free format text: CHANGE OF NAME;ASSIGNOR:ACCURAY LEASING CORPORATION;REEL/FRAME:005027/0452

Effective date: 19790702

Owner name: PROCESS AUTOMATION BUSINESS INC.,

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Effective date: 19880412