WO2003056215A1

WO2003056215A1 - Wear indicator for a seal of a suction roll of a paper or board machine

Info

Publication number: WO2003056215A1
Application number: PCT/FI2002/001002
Authority: WO
Inventors: Arto Kärkkäinen; Vesa Nokelainen; Veli-Matti Miskala; Hannu Savolainen; Kari Koirikivi; Jori Pääkkönen
Original assignee: Metso Paper, Inc.
Priority date: 2001-12-13
Filing date: 2002-12-10
Publication date: 2003-07-10
Also published as: AU2002350760A1; DE10297533T5

Abstract

The invention relates to a seal for a suction roll of a paper or board machine, said seal being placed inside a rotating shell of the suction roll and having a system for monitoring the wear of the seal (22) disposed in connection with the seal (22), said monitoring system comprising means (23, 24) for monitoring the wear of the seal (22). The means for monitoring the wear of the seal comprise an arrangement (23, 24; 27; 30, 31, 32, 33, 40; 37) for determining the need for replacement of the seal (22) based on information about the wear of the seal (22) without interrupting the operation of the suction roll.

Description

Wear indicator for a seal of a suction roll of a paper or board machine.

The invention relates to a seal for a suction roll of a paper or board machine according to the preamble of claim 1.

In paper and board machines, the vacuum zone of the suction box of suction rolls is sealed against the inner surface of the shell by means of side and end seals. The seals wear because of their rubbing contact with the inner surface of the shell, and thus the seals must be replaced at regular intervals, for example, in connection with servicing of a suction roll or maintenance of a paper machine. Since the seals are within a rotating roll shell, it is difficult to check/measure the level of their wear during operation. Premature replacement of a seal is unnecessary and operation time that is too long for a seal, in turn, can cause runnability problems with the roll, for example, providing a sufficient vacuum level can cause problems and even lead to very harmful and expensive shutdowns for repairs, when the vacuums of a suction roll have disappeared because the seals have no longer functioned,

In practice, the need for replacement of seals has been based on each paper or board mill's experience of the interval between replacements of roll seals and in such determination of the seal replacement time, the factor deciding the length of the time period between roll servicing operations has varied according to the applications of use of different rolls, for example, the decisive factor on a former roll is usually the wear of a wire sock, in connection with replacement of which the other parts of the roll have also been serviced, but in many cases the decisive factor is specifically the wear of a side seal. The magnitude/rate of wear is a characteristic that is highly roll-specific and difficult to determine in advance. Determining the time for the first servicing of a new roll is most problematic because there exists no practical history information about the factors of wear. The properties of the roll, among other things, the rate of wear of seals, have been found out only after the first servicing operation. The rate of wear of suction roll seals is also affected by the operation parameters of the roll. If, for example, running vacuums are changed, the rate of wear of the seals also changes. This is one factor that has made it further more difficult to determine the time for the servicing of a roll.

One prior-art wear indicator arrangement for a side seal is disclosed in US patent 5,746,891. In this known arrangement, the state of wear of side seals is checked when a roll/machine is serviced. The side seal is provided with wear indicators, for example, with materials of different colours embedded at different recess depths in recesses formed in the side seals, whereby it has been possible to conclude from the colour visible from the recess how far the seal has worn or the seal is provided with a scale from which it is possible to see how far wear has progressed. In addition, this US patent describes an application example which shows, in connection with a seal, electrical conductors connected to signal lights and to a source of electricity. When insulation wears away, an electric circuit is formed: the signals lights, the source of electricity and water that comes into contact with the electrical conductors, and which electric circuit causes the signal light to illuminate when the seal has worn. However, the proposed arrangements suffer from the problem that the state of wear of the side seal cannot be established until the roll has been stopped for other servicing operations and even with the signal light arrangement information is obtained only at the stage when the signal light has lit up, which means that no continuous information about the state of wear of the seal has been obtained.

International application publication WO 00/43592 discloses a side seal comprising indicator means arranged to continuously, directly or indirectly, give measurement information about a remaining wear allowance or a wear rate of a seal. In the application described in the publication, a transmitter has been arranged in connection with the seal, which transmitter measures its distance to the surface of a roll shell and gives information about the wear of the seal. A problem with this prior-art arrangement is that the transmitter has been placed in connection with a moving seal and it takes a lot of space. The transmitter has also been placed in a wearing part, i.e. in the seal itself, so that when the seal wears away, the frame of the transmitter and the transmitter may come into contact with the shell if no steps have been taken in time to replace the seal. The side seals of suction rolls extend in the longitudinal direction of a roll over the entire length of the roll and thus, if it is desirable to obtain information about the wear of the side seal in the longitudinal direction of the roll, i.e. in the cross direction of the web, several transmitters have to be placed adjacent to one another, the wiring of the transmitters being rather problematic as several wires must be passed from the moving seal inside the roll. The structure is complicated and, in addition, the transmitter shall be replaced or fitted again in connection with replacement of the seal. Moreover, the application described in the publication, which uses an induction transmitter, shall be shielded in order that the metal parts of the roll surrounding it shall not cause any interference in the operation of the transmitter.

The object of the invention is to propose an arrangement by which information is obtained about the wear of a seal of a suction roll and in which the problems described above are eliminated or at least minimized.

With a view to achieving the above objects as well as the ones coming out later, the seal for a suction roll of a paper or board machine according to the invention is mainly characterized by the disclosure in the characterizing part of claim 1.

In accordance with the invention, the means for monitoring the wear of a seal comprise an arrangement for determining the need for replacement of the seal based on information about the wear of the seal without interrupting the operation of the suction roll. In accordance with one advantageous application of the invention, in the arrangement for monitoring the wear of a seal of a suction roll in a paper or board machine, a measuring device is placed in connection with a stationary frame part of a suction box of a suction roll, for example, in a seal holder, whereby substantial benefits are achieved over the arrangement known in the state of the art. This kind of structure is simple and advantageous because in fitting the measuring device it is not necessary to take any requirements of a moving part into account. Also, in the wear monitoring arrangement in accordance with this application of the invention there is thus no risk of the measuring device, for example, a sensor, coming into contact with a shell. The wear indicator for a seal of a suction roll according to this application of the invention is simple to construct and it is small in size. It is also particularly suitable for use in connection with lockable seals because the measuring device, for example, a sensor, is in the frame of the suction box. The mounting of the wear arrangement disposed in connection with a seal of a suction roll in accordance with this application of the invention is easy because it does not require any special steps to be taken in connection with replacement of the seal since the measuring device is attached to a stationary part, for example, to the holder of the seal, which need not be changed in connection with replacement of the seal.

In accordance with one advantageous additional feature of the application of the invention described above, a counter piece fitted in the seal is used in connection with the measuring device, in which case the measuring device thus measures the distance between a stationary part and a moving part (counter piece). This application is also suitable for use in connection with lockable seals because only the counter piece is placed in a moving part, i.e. in a seal. Further, mounting is easy because in connection with replacement of a seal it is only the counter piece that need be attached to the seal if it has not already been fitted in it in advance, which is also possible. In accordance with one advantageous additional feature of the application of the invention described above, as the measuring device is used a sensor that moves with the wearing surface, for example, while loaded by a spring, thus indicating the progress of wear, in which connection no separate counter piece is needed.

An advantage of the application of the invention described above is also that, as the measuring device is not fitted in the seal itself, it is easy to dispose it in different types of seal applications and, in addition, the placing of sensor wires, if any, does not cause any problems because the wires are not connected to a moving part in the structure.

The measuring method applied in connection with this application of the invention described above may be, for example, electric, inductive, mechanical, based on pressure, optical, or the like.

The wear monitoring arrangement in accordance with the application of the invention described above can be accomplished with different types of measuring applications, by means of a sensor attached to the frame of a suction box it is possible to measure distances from different surfaces and, of course, when using an application in which the measurement takes place with respect to a counter piece, several different measurement counter piece arrangements can be designed.

In accordance with a second advantageous application of the invention, at least one monitoring member monitoring the wear of the seal is placed in the seal. The monitoring member is placed inside the seal such that, when the seal wears a certain distance, the monitoring member comes into contact with a shell or wears along with the seal or, for example, breaks, thus providing an indication of the wear of the seal, which indication is transmitted to a monitoring unit, in which the information about wear is processed. In accordance with one advantageous additional feature of this second application of the invention, at least two monitoring members, for example, sensors, extending in the longitudinal direction of a seal are placed in the seal at several desired levels. When the seal wears, the first monitoring member, for example, a sensor, touches the shell and gives an indication, whereby it is known that the seal has worn a certain distance. When the seal wears further, the second monitoring member, for example, a sensor, also touches the shell, which means that the seal has worn the next distance. The information obtained about the wear is processed in a monitoring unit and, when needed, time is computed, for example, such that the measurement of time is zeroed upon replacement of a roll and, when computing time from the start onwards, the time used for wear in respect of the first monitoring member, for example, a sensor, is obtained until the monitoring member, for example, a sensor, gives an indication, on the basis of which it is possible to predict the future useful life, when the starting situation and the first indication of wear are known. When the second monitoring member, for example, a sensor, indicates the next wear, the prediction of the remaining useful life or a wear allowance of the seal can be made still more precise. If there are several monitoring members, the monitoring unit always receives, in a manner corresponding to that described above, information about wear from the wear indication when a monitoring member comes into contact with the inner surface of the suction roll shell. In the application described above, the monitoring members can extend either over the entire length of the seal or over part of it. When using monitoring members extending over the entire length of the seal, the monitoring member coming into contact with the shell when the seal wears, in which connection the monitoring member, for example, breaks and an indication of the wear of the seal is thus obtained. There may be one or more monitoring members at different levels of the seal. When several monitoring members placed at different levels are used, information about the wear of the seal is obtained at desired intervals of wear. When using monitoring members that extend over the entire length of the seal in accordance with one advantageous additional feature of this second application of the invention, the monitoring members can be based on passing an electric current through the monitoring member or they can be, for example, optical fibres, which monitoring members are connected at one end of the seal to a current/light source and at the other end to a receiver unit, so that when the monitoring member is damaged when coming into contact with the shell, the flow of current/light stops, thus providing information indicating the wear of the seal.

The monitoring unit used in the wear monitoring system in accordance with this second application of the invention can be connected by means of wires to the wear monitoring members placed in the seal or the monitoring unit can be a separate unit to which information from the monitoring members is passed in a wireless manner, for example, telemetrically.

The monitoring members, for example, sensors of the wear monitoring system in accordance with this second application of the invention advantageously extend over the entire length of the seal, in which connection they are very easy to accomplish and mount in practice and the wiring to the monitoring devices is simpler than in the systems in accordance with the state of the art.

The invention is also suitable for use in connection with lockable seals and, when needed, control of a lockable seal can be combined with the measurement such that when the seal is moved, a locking sequence is repeated in order that the seal shall be separated from a shell. When needed, measurement of temperature can also be combined with the measuring arrangement.

In the following, the invention will be described in greater detail with reference to the figure of the appended drawing, but the invention is not by any means meant to narrowly limited to the details thereof. Figure 1 is a schematic view of one application of the invention, in which a system for monitoring the wear of a seal is mounted in connection with stationary frame structures of a suction box of a suction roll.

Figure 2 is a schematic view of a second application of the invention, in which a system for monitoring the wear of a seal is mounted in connection with stationary frame structures of a suction box of a suction roll and which is particularly suitable for use in connection with narrow seals.

Figure 3 shows an application of the invention, in which a system for monitoring the wear of a seal is mounted in connection with stationary frame structures of a suction box of a suction roll and in which no counter piece for a measuring device is used.

Figure 4 shows some alternatives for distances measured in connection with an application of the invention, in which a system for monitoring the wear of a seal is mounted in connection with stationary frame structures of a suction box of a suction roll, to monitor the wear of a seal.

Figure 5 is a schematic view of an application example of the invention, in which a suction roll seal comprises monitoring members extending in a longitudinal direction.

Figure 6 is a schematic view of a further application example of the invention, in which longitudinal monitoring members in a seal extend over the entire length of the seal.

Figure 7 is a schematic view of one application example in which members monitoring the wear of a seal extend in a transverse direction. As shown in Fig. 1, for the purpose of pressing seals 22 of a suction zone/suction zones of a suction box in a suction roll against the inner surface of a roll shell 21, a loading hose/loading hoses 26 is/are arranged in a seal holder 25 underneath the seal, i.e. on the side of the seal 22 opposite to the inner surface of the shell 21, the seal 22 being pressed by means of a pressure supplied into said loading hose. When the seal 22 wears, the pressure in the loading hose 26 can be increased, if needed, in order that the sealing effect of the seal 22 shall be maintained.

In accordance with the application shown in Fig. 1, a system for measuring the level of wear of the seal 22 is fitted in connection with the seal structure of the suction roll. A measuring device 23, for example, a sensor, is fixedly mounted in connection with a stationary frame part of the suction box of the suction roll, for example, in the holder 25 of the seal 22, and the measuring device 23 is used for measuring the distance to a counter piece 24 attached in connection with the seal 22, for example, to its lower surface. When in the initial situation, when the seal 22 is loaded against the shell 21, the measurement is zeroed, the wear of the seal 22 is found out based on a change detected by the measuring device 23 in the position of the counter piece 24.

The application shown in Fig. 2 is particularly suitable for use in connection with very narrow seals, but it can, of course, also be applied in connection with wide seals. In Fig. 2, corresponding reference numerals have been used of the parts corresponding to those of Fig. 1. A measuring device 23 is used for measuring the distance of a counter piece 24, which counter piece 24 is preferably made of a magnetic metal, thus obtaining continuous information about the wear of the seal 22. The measuring device 23 is attached to a seal holder 25, which is, as that of Fig. 1, a part fixedly mounted to the frame part of the suction box.

The measuring application of the wear indicator arrangement shown in Fig. 3 uses a sensor which, for example, while being loaded by a spring, moves with the wearing surface, thus indicating the progress of wear. In Fig. 3, the same reference signs have been used of the parts corresponding to those of Figs. 1 and 2. The measuring device 23 is a sensor which is provided with a loading member 27, for example, with a member that operates with spring loading, whereby the measuring device 23 moves with the wearing surface of a seal 22, and information about the progress of wear is thus obtained based on movement S.

In accordance with Fig. 4, the wear indicator arrangement can be accomplished with different types of measurement applications, and by means of the measuring device, for example, a sensor attached to the frame of the suction box it is possible to measure distances from various surfaces and several different arrangements for the measurement counter piece can, of course, be designed or it is possible to use a measurement application, for example, a sensor in connection with which no counter piece is needed. Fig. 4 illustrates a few possible arrangements. The numbers circled in Fig. 4 represent the different measuring alternatives described in the following. When a seal 22 is pressed to the bottom, i.e. against the side surface of a shell 21, the distances between points 1-3 or 2-3 can be measured, whereby information is obtained about the wear of the seal. Further, it is possible to measure distances 2-4, 2-5, 2-6, 5-9, 6-9, 7-8, 10-11, 10-6. Information about the wear of the seal is thus obtained as the distances change as a result of wear.

Although Figs. 1-4 show applications of the invention in connection with side seals of a suction roll, the arrangement can, of course, be applied, according to the principles described above, in connection with end seals, too.

In the following Figs. 5-7, the same reference numerals are used of the parts corresponding to one another.

In Fig. 5, a seal is designated by the reference numeral 22 while the numeral 25 designates a seal holder and the reference numeral 26 designates a loading hose of the seal. A suction box is denoted with the reference numeral 28 and a shell of a suction roll is denoted with the reference numeral 21. The wear monitoring members, for example, wear monitoring wires placed in the seal are denoted with the reference numerals 30, 31, 32, 33 and a monitoring unit connected with them with the reference numeral 37. The monitoring members, for example, sensors 30, 31, 32, 33 are made of an electrically conductive material, such as, for example, metal. The monitoring members, for example, wires, can be electrically conductive, as mentioned above, for example, electric conductors, they can also be optical fibres or other equivalent monitoring members, on the basis of which an indication of wear can be transmitted from the seal to the monitoring unit 37.

When optical fibres are used, light-transmitting means and, correspondingly, receiver means are connected to the fibres, whereby light is passed from one end to the other end and, when the seal wears away, the optical fibre, for example, breaking because of wear, they do not conduct light, thereby providing an indication of the wear of the seal.

In this application of the invention, it is possible to use one or more longitudinal or transverse monitoring members depending on the required information about the wear of the seal. The monitoring unit 37 may also be connected by means of wires to the wear monitoring members or it can be a separate unit, to which information is passed in a wireless manner, for example, telemetrically.

As shown in Fig. 5, for the purpose of pressing the seals of a suction zone/zones 22 of a suction box of a suction roll against the inner surface of the shell 21 of the roll, the loading hose 26 is arranged in the holder 25 of the seal 22 underneath the seal, i.e. on the side of the seal 22 opposite to the inner surface of the shell 21, the seal 22 being pressed by means of a pressure fed into the loading hose. When the seal 22 wears, the pressure in the loading hose can be increased, if needed, in order that the sealing effect of the seal 22 shall be maintained. In normal operation conditions, the loading pressure need not be increased when the seal wears. As shown in Figs. 5 and 6, monitoring members, for example, sensors 30, 31, 32, 33 extending in the longitudinal direction of the seal 22 are placed in the seal 22 at different depths XI, X2. When the seal 22 wears, a first monitoring member, for example, the sensor 30, comes into contact with the inner surface of the shell 21 and gives an indication of the wear of the seal XI (Fig. 5). Similarly, a monitoring member, for example, the sensor 30 when coming into contact with the shell 21 wears out / breaks, whereby an indication of the wear of the seal XI is also obtained (Fig. 6). When the seal 22 wears further, a second monitoring member, for example, the sensor 31 comes into contact with the inner surface of the shell 21, thus providing a second indication of the wear of the seal X2, on the basis of which information is obtained about the progress of wear (Fig. 5). Similarly, a monitoring member, for example, the sensor 31 when coming into contact with the shell 21 wears out / breaks, whereby an indication of the wear of the seal X2 is also obtained (Fig. 6). The information about the wear XI, X2 is passed to the monitoring unit 37, the information about the wear of the seal 22 being obtained based on a time measuring arrangement associated with the monitoring unit, and thus further, if there are several seals, as shown, for example, in Fig. 6, the wires 32 and 33, in turn, wear out when they come into contact with the inner surface of the shell.

In the application example of the invention shown in Fig. 7, monitoring members 40, for example, sensors, are placed so that they extend in a direction that is transverse to the longitudinal direction of a seal 22, which members wear when the seal 22 wears and thereby transmit information about the wear of the seal 22.

In Figs. 6 and 7, a longitudinal monitoring member 30 (31, 32, 33) is connected at one longitudinal end of the seal to a current source or equivalent 34 and at the other end to a receiver means 35, whereby when the longitudinal monitoring member 30 wears out or when the transverse monitoring member 40 gives an indication, an indication of the wear of the seal is obtained as the flow of current stops or, when a sensor based on optical fibres is used, based on a break in the light.

Claims

1. A seal for a suction roll of a paper or board machine, said seal being placed inside a rotating shell (21) of the suction roll and having a system for monitoring the wear of the seal (22) disposed in connection with the seal (22), said monitoring system comprising means (23, 24; 27; 30, 31, 32, 33, 37, 40) for monitoring the wear of the seal (22), characterized in that the means for monitoring the wear of the seal comprise an arrangement (23, 24; 27; 30, 31, 32, 33, 40; 37) for determining the need for replacement of the seal (22) based on information about the wear of the seal (22) without interrupting the operation of the suction roll.

2. A seal for a suction roll as claimed in claim 1, characterized in that the means (23, 24; 27) for monitoring the wear of the seal (22) comprise a measuring device (23) fixed in connection with stationary frame structures of a suction box of the suction roll, continuous information about the wear of the seal (22) being obtained when measuring by said measuring device (23).

3. A seal for a suction roll as claimed in claim 1 or 2, characterized in that the measuring device (23) is fixed in connection with a holder (25) of a side seal.

4. A seal for a suction roll as claimed in any one of claims 1 to 3, characterized in that the means (23, 24) for monitoring the wear of the seal comprise a counter piece (24) fixed in connection with the seal (22), continuous information about the wear of the seal (22) being obtained when measuring by said measuring device (23) the location or relative distance of the counter piece (24) fixed in connection with the seal (22).

5. A seal for a suction roll as claimed in claim 4, characterized in that the counter piece (24) is fixed to the side opposite to the wearing side of the seal (22).

6. A seal for a suction roll as claimed in claim 4 or 5, characterized in that the measuring device (23) is an inductive sensing device and the counter piece (24) is made of a magnetic metal.

7. A seal for a suction roll as claimed in any one of claims 1 to 3, characterized in that the means (23, 27) for monitoring the wear of the seal (22) comprise a spring loading member (27) arranged to move with the wearing surface of the seal (22), whereby continuous information about the wear of the seal (22) is obtained by said measuring device (23).

8. A seal for a suction roll as claimed in claim 1 or 2, characterized in that the means for monitoring the wear of the seal are based on electrical measurement of distance.

9. A seal for a suction roll as claimed in claim 1 or 2, characterized in that the means for monitoring the wear of the seal are based on mechanical measurement of distance.

10. A seal for a suction roll as claimed in claim 1 or 2, characterized in that the means for monitoring the wear of the seal are based on measurement of distance carried out by means of pressure.

11. A seal for a suction roll as claimed in claim 1 or 2, characterized in that the means for monitoring the wear of the seal are based on optical measurement of distance.

12. A seal for a suction roll as claimed in claim 1 or 2, characterized in that the means for monitoring the wear of the seal are disposed in connection with a lockable seal.

13. A seal for a suction roll as claimed in claim 1, characterized in that at least one monitoring member (30, 31, 32, 33; 40) is arranged in the seal (22) to indicate the wear of the seal, which monitoring member, when the seal (22) wears and the monitoring member comes into contact with the inner surface of the shell (21) of the suction roll, is arranged to provide an indication, which indication is arranged to be transmitted to a monitoring unit (37).

14. A seal for a suction roll as claimed in claim 1 or 13, characterized in that time measuring means are associated with the monitoring unit (37), whereby a prediction of the wear of the seal (22) can be made based on each wear indication (XI; X2).

15. A seal for a suction roll as claimed in claim 1, 13 or 14, characterized in that the monitoring member (30, 31, 32, 33) extends in the longitudinal direction of the seal and extends over the entire length of the seal (22).

16. A seal for a suction roll as claimed in claim 1, 13 or 14, characterized in that the monitoring member (30, 31) extends in the longitudinal direction of the seal and extends over a certain portion of the length of the seal (22).

17. A seal for a suction roll as claimed in claim 1, 13 or 14, characterized in that the monitoring member (40) extends in a direction transverse to the longitudinal direction of the seal (22).

18. A seal for a suction roll as claimed in any one of claims 1, 13 to 17, characterized in that the monitoring member (30, 31, 32, 33; 40) is made of metal.

19. A seal for a suction roll as claimed in any one of claims 1, 13 to 17, characterized in that the monitoring member (30, 31, 32, 33; 40) is an optical fibre.