JPS6153479B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus that analyzes and continuously monitors pressure fluctuations in paper stock liquid in each device before the headbox, which is a factor in fluctuations in basis weight in a paper machine. Among the amounts of paper produced by a paper machine, the most important factor is basis weight. In recent years, with the development of basis weight meters, highly accurate control methods have been developed for basis weight control.
Feedback loop control including dead time delay, first-order delay, and second-order delay has come to be implemented, and basis weight control of 1 to 2 minutes or more has become commonplace. However, these control loops do not meet the requirements of paper machines that have paper stock liquid frequency fluctuations of less than 1 min to 2 min, which is equivalent to shortening time, due to paper basis weight fluctuations, and machine tuning methods There is nothing else. Some manufacturers have developed wet part tuning methods for paper machines and provide their know-how, but these are only short-term comparisons, and the final judgment is based on the basis weight indicator. . Therefore, if other factors are involved, we will end up searching for indirect causes and will not be satisfied. The present invention introduces the subject device to enable continuous monitoring of pressure fluctuations in paper stock liquid at any location, at any time, as a distribution amount of fluctuating frequency components, and the results obtained by machine tuning can be monitored continuously. This is a device that can instantly monitor the movement of each frequency component, and provides an online frequency analysis device for the causes of basis weight fluctuations in paper machines that accurately grasps the pressure fluctuations of the stock liquid at each point. It is something to do.

Most of the short term fluctuations that are currently a problem are caused by each flow and its equipment from the wire part to the previous one. The factors that affect basis weight can be collectively referred to as flow rate fluctuations. Fluctuations in flow rate are thought to be caused by fluctuations in pressure, and partial fluctuations in flow rate also affect concentration. FIG. 3 shows a schematic diagram of the pressure fluctuation measurement points around the approach flow. As shown in the figure, the raw material is supplied through a stock valve 1, sent to a cleaner 3 by a pump 2, and from the cleaner 3 through a screen 4 to a head box 5, from which it is spouted onto a paper screen 6. The sensor a shown in Fig. 1 measures pressure fluctuations at the inlet or outlet of the pump 2, cleaner 3, screen 4, etc. shown in the figure, or at the head box 5 times, etc. do. All the pressure energy depends on the pump 2, and there is also pulsation of the beam due to the rotation speed, but the range where the basis weight is affected is naturally limited, and the detection frequency band is 1/60Hz to 1Hz. think. Figure 2 A shows the above sensor a.
This is the paper stock liquid pressure fluctuation waveform at the outlet ○D of the cleaner 3 measured by
Shows the pressure fluctuation waveform measured at outlet ○. The sensor a detects the pressure fluctuation at each point as a frequency signal (analog signal), and applies the detection output to the A/D converter d shown in FIG. 2, which converts it into a digital signal. In the figure, b is an electrical input, and c is an input changeover switch. Further, the digital signal obtained by the A/D converter d is inputted into an arithmetic unit e consisting of a frequency discrimination circuit for frequency analysis. f is an operation section of the calculation section e. The calculation output of the calculation section e is given to the display section g and the recording section h, so that the frequency analysis results in the calculation section e are continuously displayed and recorded at the same time. As a result, the stock liquid pressure fluctuations in each device detected by the sensor a are continuously and automatically monitored as a common frequency distribution amount. For example, the pressure fluctuations detected by sensor a are displayed and recorded as information as shown in FIG. Can be monitored continuously. In the figure, the numbers on the horizontal axis indicate frequencies, and the vertical axis indicates the distribution amount (%) of each frequency. The headbox located at the leading edge of a paper machine differs depending on the manufacturer, and the state of the paper in the flow direction and lateral direction changes greatly depending on the state of the ejection from the headbox. Therefore, it is the operator's job to find the best characteristics of each piece of equipment, but this can only be done by changing the paper web's formation and basis weight. Depending on the headbox, pressure fluctuations caused by previous equipment, such as the screen, cleaner, each pit, etc., or concentration fluctuations caused by these fluctuations, etc., may not be eliminated by the headbox, and each point It is necessary to investigate the following. By introducing the analysis device according to the present invention into a paper machine, it is possible to
It is possible to continuously monitor the pressure fluctuation of the paper stock liquid as the distribution amount of fluctuating frequency components for any given time, and the results of machine tuning can be instantly monitored as the movement of each frequency component, making it the best method. It is possible to check at a glance whether or not the pressure state has been tuned, and the amount of distribution of frequency components included in the pressure fluctuation waveform at each point can be accurately grasped for each frequency. As a result, pressure fluctuation factors can be detected accurately and early, and countermeasures can be taken quickly.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the invention. Fig. 1 is a block diagram showing this analyzer, Fig. 2 shows an example of the pressure fluctuation waveform detected by the sensor, Fig. 3 shows the pressure fluctuation measurement points in the paper machine, and Fig. 4 is an information graph displayed by this analyzer. a...Sensor for detecting pressure fluctuations, d...A/D converter, e...Calculating unit, g...Display unit, h...Recording unit, ○i~
○...Pressure fluctuation measurement point.

Claims (1)

[Claims] 1. Sensors detect the pressure fluctuations in the stock liquid in each device before the head box, and convert the analog signal (frequency signal) indicating the stock liquid pressure fluctuation detected by the sensor into a digital signal using a converter. The digital signal is input into a calculation section consisting of a frequency discrimination circuit to perform frequency analysis, and the calculation output of the frequency analysis is given to a display section for display, and at the same time, the calculation output is given to a recording section. A paper machine characterized in that it is configured to record and continuously and automatically monitor paper stock fluid pressure fluctuations in each device detected by the sensor as a common frequency distribution amount. Online frequency analyzer for basis weight variation factors.