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Method of paper machine control and apparatus for the method

  • US 6,904,331 B2
  • Filed: 01/28/2002
  • Issued: 06/07/2005
  • Est. Priority Date: 04/04/2001
  • Status: Active Grant
First Claim
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1. A method for controlling a paper machine, comprising the steps of:

  • solving difference equations obtained by differentiating heat transfer equations that hold true among a steam drum, web and canvas;

    predicting a dryer steam pressure after grade change; and

    using said predicted dryer steam pressure as a dryer steam pressure setpoint after grade change;

    wherein the initial value of a web'"'"'s moisture percentage at a dryer part inlet is calculated according to changes in a bone dry coated weight and machine speed when solving said difference equations; and

    wherein the initial value of said web'"'"'s dryer part inlet moisture percentage after grade change is evaluated according to the following equation;

    initial





    value





    of





    web




    s





    moisture





    percentage
    =MPNowInit+A1·

    BD2-BD1BD1
    +A2·

    V2-V1V1
    whereBD1=bone dry weight before grade change BD2=bone dry weight setpoint after grade change V1=machine speed before grade change V2=machine speed setpoint after grade change; and

    A1, A2, and MPNOWInit=parameters.

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