Abstract: The system effects an automatic observation of the dry line on wire of the Fourdrinier paper machine and the control actions based on it. In order to produce an image of the dry line range on wire this is illuminated by means of a large, diffusely illuminating surface (20) of even luminosity. The material on moving wire (10) is imaged by an optoelectric camera (40) on a detector whereby the pulp surface preceding the dry line and being specularly reflecting is found homogeneous and bright while the web surface following it and being diffusely reflecting is found homogeneous but matter and darker. The electric image signal delivered by the detector is conducted to a computer (50) in which the dry line is identified as the borderline of said surfaces of different brightness.

Abstract: The control method is directed to a quality characteristic of the process material, typically to its outlet concentration. In control of the actuator which is a part of feedforward or feedback control of outlet concentration, one takes account of changes of the material volume and flow, in addition to the inlet concentration or control deviation. With this object, at least two of the quantities of inlet flow, outlet flow and material volume are measured or determined and by means of them a variable is further determined with regard to which the control method is invariant. Two alternative variables are presented, one being typically applicable to control of a process with finite distribution of the flow velocity and the other to control of a process with vigorous mixing. By means of a time-variable control method, the controls can also be implemented with time as the independent variable. The invention also relates to devices which implement the control methods presented.

Abstract: The method and apparatus automate the observation of the dry line on the wire of the Fourdrinier paper machine on whose visual observation by eye the conventional control of the paper machine is based. In the invention, the position of the dry line and its such values which deviate from normal, and the quantities which express its form, are reproduced to the operator repeatedly. In order to carry out this, it is formed as one essential feature of the invention, the image of the plane of the wire with an opto-electric camera and the electric, discrete image information is transmitted into a computer. While the conventional observation of the dry line is based on reflections from the pulp surface which are brighter than the other surface, these, however, disturb an instrumental observation and check an interpretation of the result of observation.

Abstract: The invention relates to a method and apparatus for controlling the pH in a continuous flow vessel into which process material is fed through a feed channel and controlling chemical solution is fed through a control channel and in which the pH is measured at an output part of the vessel in order to effect the control by controlling the control chemical feed according to the feedback method, the value of a reference variable being given by a pH number.