FI115921B - A method for measuring the tension of a drying wire in a dryer section of a papermaking machine - Google Patents

Description

115921

A method for measuring the tension of a drying wire in a dryer section of a papermaking machine

The invention relates to a method according to the preamble of claim 1.

As is known in the prior art, the dryer groups of dryer parts based on the cylinder drying of a papermaking machine employ double wire and / or single wire. In the two-wire feed, the drying cylinder groups have two wires which press one of the webs above and 10 against the heated cylinder surfaces. In a single-wire delivery, each dryer cylinder group has only one dryer wire in which the web passes through the entire group so that the dryer wire presses the web against the heated cylinder surfaces of the drying cylinders and the turning rolls or rollers between the drying cylinders remain on the outside. For single-wire feeds of this type, the drying cylinders are outside the wire loop and the pivoting cylinders or rollers are located inside it.

As the speeds of the paper machines increase, runner problems have also begun in the single wire export area, especially in the first dryer cylinder groups of the dryer section. As has been known in the past, attempts have been made to reduce these problems by using various runnability components, such as blower boxes marketed by HiRun under the trade name of the applicant. One type of driver- ;;;; The blade component is described in FI Patent Publication 110625, which discloses a blower control device in a paper machine or the like, which blowing device comprises a blowing blade fitted at the opening of the nip between the wire and the cylinder and at least two near the wire. with a fitted nozzle. First * t

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The '1' nozzle is located at the opening nip between the wire and the cylinder, blowing air away from the gap between the wire and the blowing device. The second nozzle is • »* ·; · * fitted in the direction of the wire travel at a distance from said opening nip.

; The air jets discharged from the nozzles maintain a vacuum in the space between the blower and the blower. Further, the blowing device is provided with a throttle-thrust member extending a short distance from the nip opening 2 115921, which divides the vacuum space formed between the first and second nozzles into a boosted vacuum region bordering the first opening nip and a second zone of smaller vacuum. Also known in the art is a system having mechanical seals on both sides of the opening nip and additional suction.

In the case of runnability components, gaskets placed in connection with blowing devices and the like are used to limit the desired negative pressure ranges. If the tension of the drying wire 10 is not correct, the wire may bend and wear the seals of the blowing devices, after which the runnability component will no longer function as desired. This results in a loss of runnability and, at the same time, a reduction in efficiency as the production rate drops, which can result in very high financial losses.

15

Maintaining the correct tension of the drying fabric is also important for the runnability of the drying group, so knowledge of the wire tension and its possible variations is important for the functioning of the drying sections of the drying section.

• · • * »• .. '20 In practice, today, the situation is monitored by monitoring the pocket vacuum by measuring the pressure of' ·· * 'from the pocket space. However, this measurement does not always tell the whole '·· ** truth. For example, when the wire tension falls for some reason, the vacuum in the pocket • * »• ;;; may be normal even though the wire has been bent due to a decrease in tension and the runner component seals may have worn out. If the tension of the wire returns to normal, the situation is particularly problematic because the seals produced by the bent wire will not keep the vacuum within the desired range.

[In practice, it is also possible to indirectly monitor the wire tension by the wire tension '; '' Computational hydraulic motor pressures, but that motor has: 30 high hysteresis, so the resulting tension is only indicative. Thus, one of the non-essential objectives of the invention is to provide feedback tension measurement and more accurate tension control.

It is an object of the invention to provide a method and apparatus for eliminating and / or minimizing the above problems.

In order to achieve the foregoing and further objects, the process according to the invention is essentially characterized by what is stated in the characterizing part of claim 1.

10

According to the invention, the deflection of the wire is measured, for example, by a laser, optical or mechanical measuring method, preferably by continuous measurement. The measurement is performed as a distance measurement, either intact or touch measurement. If the deflection of the wire increases beyond the defined alarm limit, which causes the wire tension 15 to fall, measures are taken to prevent the seals limiting the vacuum areas of the blower from being worn. The measurement of the deflection of the wire is carried out using at least one measuring point, more preferably several measuring points are used to obtain more accurate information on the curvature of the wire, which together with the vacuum measurement of the pocket space gives the reference tension of the wire.

The measurement according to the invention is most preferably carried out automatically, continuously * ;;; measurement, but it is also possible to use manual measurement at intervals to carry out the invention. When using automatic 25 measurement, the measuring devices can be placed either on the side of the wire on which the web passes or on the opposite side. When using a manual measuring arrangement, the measurement is preferably performed from the paper side. In this case, the seals can be protected from wear by placing a wear-resistant element in connection with or proximity to the sealing element, whereby the lack of feedback on the wire tensioning does not cause the seals to wear excessively when the wire tension falls unexpectedly.

4, 115921

When measuring the deflection of a wire by, for example, a laser, optical or mechanical measuring method together with measuring the vacuum in the pocket, the measurement results from the calculation is kept constant but adjusts the suction / blowing of the runnability component or checks the operation of the vacuum measurement.

According to a preferred embodiment of the invention, the measurement is measured as a three-point measurement, whereby the measurement results provide a circular arc of the deflection of the wire, and together with the results of the pocket vacuum measurement provide reference fabric tension.

For example, the measuring device used in connection with the invention is fixedly connected to the runnability component when continuous measurement is used.

Preferably, in connection with the method according to the invention, there is feedback from measurement to control of runnability component vacuum and wire tension. In the event of problems with the wire tension during measurement, the cause of the change in wire thickness is determined and the necessary corrective action is taken. If desired, a plurality of measuring devices may also be provided in a direction transverse to the direction of the wire travel, whereby the tension profile of the wire can be measured. The arrangement may also be combined with a wire permeability measuring device.

By means of a feedback tension measurement according to a preferred aspect of the invention, the - ';;; The tension is adjusted more precisely because the result is an actual tension change '1' regardless of the hysteresis of the adjustment.

In the following, the invention will be described in more detail with reference to the accompanying drawings *, · 30, the details of which, however, are by no means intended to be narrowly limited.

5, 115921

The figure schematically illustrates a preferred embodiment of the invention.

In the diagrammatic embodiment of the invention shown in the figure, the invention is illustrated in a drying cylinder group 5 applying a single wire threading of a papermaking dryer, the drying group showing two successive drying cylinders 10 and 12 and a pivoting web which kneels from the top row drying cylinder 10 to the bottom row turning cylinder or roll 14 and further to the top row drying cylinder 12.

In the pocket space T between the drying cylinders 10, 12, the swivel cylinder or roll 14, the drying wire 16, a runnability component, for example a blowing box 30, is provided to increase the runnability of the paper web W in cylinder drying.

15

The runnability component 30 provides for the flow of web W and wire 16 from cylinder 10 to pivoting cylinder or roll 14 vacuum regions 34'and 34 "separated by a seal 50, which seal 50 is preferably a labyrinth seal. : .v From the nozzles 36, 44 of the blower device connected to the blowing air chambers ... by means of the blows, i.e. air jets, obtained by the '20 36' and 44 ', indicated by the arrows • *' · · · ' 34 ".

· ;;; In the figure, the invention is described only with respect to one type of runnability component * '· 30, but the invention is applicable to many different types of runnability components, 25 components, and situations where a runnability component is not required, ”! but information is needed on the tension of the drying wire 16.

] 'The preferred embodiment of the invention shown in the figure has a runtime command; 'To component 30 on the wall facing the web W and the wire 16 below the gasket 50 ;,; : 30 is a measuring device 60 through which the curvature of the wire 16 is measured as a continuous measurement ''. In addition, the measuring device 60 is provided with means for measuring the underpressure of the pocket space T. The measuring device 60 shown in the figure performs the measurement with a laser meter with three-point measurement. The measuring device 60 may be, for example, a laser measuring device, an optical measuring device or a mechanical measuring device. The measurement results obtained from the measuring device 60 are transmitted to the measurement result calculation unit 61, where the measurement results 5 calculate the curvature of the wire 16, whereby the deflection of the wire 16 is obtained. According to a further advantageous feature of the invention, the calculation of the measurement results is combined with the automation system 62, by means of which the information obtained through the calculation of the measurement results can be performed to correct the tension of the wire 16.

10

There may be a plurality of measuring devices 60 in the transverse direction of the direction of travel of the wire 16, whereby the tension profile of the wire 16 in addition to the deflection of the wire 16 can also be determined. The arrangement may also be connected to a wire 16 permeability measuring device.

15

The three-point laser measuring device 60 shown in the figure is provided with a plurality of sensors. If desired, a fourth measuring point (not shown) which is not in line may be used to obtain a more reliable result. Some or all of the measuring points are; Y: replaceable, for example, with mechanical knuckles, but the accuracy of measurement *; · 20 may be affected.

HM * «· Y (ί The measuring system 60, 61 can be connected to the automation system 62 for monitoring the distance and moving the sealing strokes 50 of the runnability component 30 according to the bending of the wire 16 to prevent the seals 50 from being worn keeping the vacuum in the opening nip.

Thus, to measure the tension of the wire, the radius of curvature R of the wire and the vacuum / pressure difference p of the pocket are measured over the wire, whereupon the pocket pins are almost vertical: the reference tension of the wire T is given by T == pxR. When processing the results as needed:: ': 30 higher tensile information resolutions can be taken into account for the direction of wire travel in space where the export is substantially different from vertical export, wire weight, running speed, paper web weights, paper web tension.

The invention can also be implemented as a so-called basic arrangement in which the tension of the wire 5 16 is manually measured by a laser meter. The location of the rolls and cylinders 10, 12, 14 is known, and in this embodiment, the pressure difference is assumed to be constant throughout the distance from the drying cylinder 10 to the rotating cylinder or roll 14 and one laser is sufficient to perform the single point measurement. According to the invention, the laser measuring device may also be replaced by a mechanical or other optical measuring device.

10

The invention is very suitable for use with the concept illustrated in the figure, but it can also measure the tension of the wire 16 at any point in the drying cycle when a suitable pressure difference is provided over the wire 16. In order to achieve a sufficient pressure difference, the paper web W facing the wire 16 seals the wire 16, 15 because the air permeability of the paper web W is lower than that of the wire 16, and is even necessary in certain applications to achieve a sufficiently high pressure difference.

The invention has been described above with reference only to some preferred embodiments thereof, the details of which, however, are not intended to be narrowly limited.

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Claims (8)

Method in a drying section of a paper machine for measuring the tension in a drying wire (16), characterized in that in the method the tension in the drying wire (16) is measured in one of drying cylinders (10,12), a breaking cylinder or roller (14). and the drying wire (16) defined pocket space (T) by a laser, optical or mechanical measurement method at eating least one measuring point as a distance measurement which is performed continuously or at appropriate intervals, that in the process the pressure of the pocket space (T) is measured in the relevant pocket space. and, on the basis of the measurement results, in a calculation unit (61) a reference voltage is determined in the wire (16). Method according to Claim 1, characterized in that the measuring method is applied in conjunction with an executable component (30) located in the pocket compartment (30), through which an underpressure is promoted which promotes the drivability of a support of the drying wire (16). paper web (W) to be dried, that the underpressure in the pocket space (T) is determined for investigating the function of the executability component (30) on the basis of the voltage in the wire (16) obtained in the calculating unit (61) on the basis of the measurement results measured with a measuring device (60). • »·» »» • »· 20 Method according to claim 1 or 2, characterized in that the measuring method is applied to a location of the course of the drying wire (16) where a pressure difference acts over the wire (16). • · Method according to any one of claims 1-3, characterized in that in the process. . The result is that the results from the calculation unit (61) are led to an automation system (62), whereby the automation system (62) provides instructions for carrying out the necessary corrective measures when the voltage determined in the measurement results is determined on the basis of the measurement results. ; lane (16) is outside a set alarm limit. * »* *» T »« π 115921 Method according to any of claims 1-4, characterized in that in the method, the voltage in the wire (16) is measured with a measuring device (60) fixed to the drivability component (30) as a continuous measurement. 5 Method according to any of claims 1-5, characterized in that the measurement is carried out as a three-point measurement. Method according to any one of claims 1-6, characterized in that the method is applied in a transverse direction in a transverse direction in several places with the measuring device (s) (60) performing the measurement, in the running direction of the wire (16). of the measurement results, a voltage profile is obtained in the wire (16). Method according to any of claims 1-7, characterized in that the method is applied in a drying cylinder group applying single-wire drawing, wherein the paper web (W) to be dried has been arranged to run supported by the drying wire (16). The drying wire (16) presses the web (W) against heated cylinder surfaces on the drying cylinders (10,12) and the web (W) becomes on the outer curve side of the breaking cylinders or rollers (14) between the drying cylinders. I 1 »ti I ·« f 1 • 1 • · * (· <· 1 1 f · • 1 • I »*» · • »· • I · · *» i