Method, system and a computer program product for condition monitoring of a continuous element moving in a fiber web or paper finishing machine

The invention relates to a method for monitoring the condition of a continuous element (44) moving in a fiber web or paper finishing machine, said monitoring being performed with a rotating machine element (41), which is equipped with a sensor assembly (24) that measures force or pressure and against which the continuous element moves. In the method, the machine element is made to rotate against the continuous element, a measurement signal (25) is generated between the machine element and the continuous element with the sensor assembly, and a cross-directional profile (21) of force or pressure generated between the machine element and the continuous element is formed from the measurement signal. Said moving continuous element is a fabric (32, 33) installed in a fabric run (22, 23) traveling via the machine element. In the method, the fabric is additionally installed in a fabric run, wherein it moves via said machine element equipped with a sensor assembly, a reference profile (35) is formed for the cross-directional profile after installing the fabric in the fabric run, the cross-directional profile formed from the measurement signal and representing force or pressure generated between the machine element and the fabric is compared with the reference profile, and information (37) is produced from the comparison for monitoring the condition of the fabric. The invention also relates to a corresponding system and a computer program product.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a U.S. national phase of PCT/FI2017/050121 filed on Feb. 24, 2017 and claims priority on FI 20165145 filed on Feb. 25, 2016, both of which are incorporated herein by reference

Not applicable.

BACKGROUND OF THE INVENTION

The invention relates to a method for monitoring the condition of a continuous element moving in a fiber web or paper finishing machine, said monitoring being performed with a rotating machine element, which is equipped with a sensor assembly that measures force or pressure and against which the continuous element moves, and whereinthe machine element is made to rotate against the continuous element,a measurement signal is generated between the machine element and the continuous element with the sensor assembly,a cross-directional profile of force or pressure generated between the machine element and the continuous element is formed from the measurement signal.
The invention also relates to a corresponding system and a computer program product.

Profiles, quality and/or tightness of parent rolls produced by paper machines and paper finishing processes have conventionally been monitored with manual methods. One of these is the knocking of parent rolls between reel rails during the operation of the machine. In this case, the user of the measuring device (wooden block or “Beloit Hammer”) goes in front of a rotating winding-up parent roll to perform the measurement. The user walks in the cross direction of the machine from side to side scanning, by knocking, the variations in the tightness and/or hardness of the parent roll and the quality of the roll in general. Based on the observations, conclusions are drawn regarding paper profiles, needs of profiling changes and modification needs of reel parameters (such as linear load).

Recently, safety at work has increasingly come to the fore in all aspects related to operating of paper machines. One manifestation of this is the attempt to prevent operators from going inside a paper machine, near rotating rolls, for example. For this objective, safety gates and light curtains are installed, for example. These ensure that one cannot access dangerous places during the machine operation. In new machines, such safety fittings are already standard equipment, particularly at reels and winders. In old machines, they will become more and more common as the machines are rebuilt. In western countries, user safety must be taken into account in each machine rebuild, and everything must be done to maximize safety. In practice, this leads to the necessity of denying user access to dangerous places.

Due to the aforementioned reasons, it is impossible for operators in many machines to gain access to profile monitoring in the wind-up section, which is an essential part of machine monitoring. This is because access between the reel rails is forbidden during the machine operation. This prohibition is further strengthened by equipping the reel with safety gates. Opening the door of the gates stops the production. The introduction of these safety improvements is grounded, since, when a web break occurs, an operator knocking a roll is in danger. This also applies to situations in which a parent roll starts to decompose for some reason. In such a situation, an operator feeling the surface of a parent roll will certainly get hurt and the risk of death is significant.

In addition to the knocking performed in an operating machine, it is of course also possible to try to monitor roll profiles by measuring, knocking and/or manually probing parent rolls that have already been completed and stopped. In this case, it is already late for any improving actions, as the roll is already completed. At this stage, nothing can any longer be done to improve its tightness or other properties. Furthermore, the measuring of even stopped parent rolls begins to be challenging today for safety reasons. In addition, it is difficult to enter the winder's unwinder or the preceding reel spool storage rails because of safety gates, for example. In some cases, the same applies even to shipping roll sets completed at the winder. In some mills (particularly in North America), access to the dry end side of the winder is also restricted.

In addition to the aforementioned rolls, manual methods have traditionally also been used to monitor paper machine fabrics. One example of these is the measurement of fabric tension with a manually operated tension measurement device. In this case, the user of the measurement device goes to a suitable position in a fabric run, close to the fabric, and presses the device against the fabric. The user walks in the cross direction of the machine from side to side scanning in this way variations in the fabric tension in the cross direction. Based on the measurement, it is possible to draw conclusions about the fabric condition, possible slackened areas and the future fabric change requirement. The condition of a fabric can also be monitored during the machine operation with moisture or permeability measurements.

Fabric and web tension measurement with a roll equipped with sensors is known from FI patent 113804. However, this publication does not propose a method for condition monitoring of a target element; instead, monitoring of both the fabric condition/wear and the roll quality/hardness have practically been implemented with the aforementioned manual methods.

For the aforementioned reasons alone, many mills have started to look for possibilities to get rid of fabric scanning and other inspections related to their condition performed during the machine operation, due to safety at work aspects. This poses a problem to operators, since it should be possible to monitor fabric wear even under conditions other than during a shutdown.

SUMMARY OF THE INVENTION

The object of this invention is to provide a method, a system, a rotating machine element and a computer program product, which can be used to improve the safety at work in a fiber web or a paper finishing machine while monitoring the condition of a continuous element, more specifically a fabric, moving in the machine. The characteristic features of the method, the system, the rotating machine element and the computer program product according to the invention are set forth, respectively, in claims1,16,20and21.

In the method, the fabric is installed in a fabric run, wherein it moves via a machine element equipped with a sensor assembly, a reference profile is formed for the tension profile of the fabric formed between the rotating machine element and the fabric after installing the fabric in the fabric run, the tension profile, formed from the measurement signal, of the fabric formed between the machine element and the fabric and the reference profile are compared, and information is produced from this comparison for monitoring the condition of the fabric. The comparison provides information about the condition and quality of the fabric. Owing to the formed reference profile, it is possible to identify a change in the fabric condition already at an early stage, monitor its development, make the condition change and the related information available for the machine control system or known to the operator, and perform actions regarding the fabric. Thus, the invention also improves safety at work. Owing to the reference profile and the comparison made relative thereto, it is possible to determine the condition of the fabric without the operator having to go near it in order to take manual measurements. Furthermore, the invention enables easy and quick observation of the response caused to the fabric condition and quality by the actions taken.

According to an embodiment, the sensor assembly, with which the cross-directional profiles of force or pressure are formed, may include one or more sensors installed on the shell and/or the cover of the machine element. The sensor may measure force or pressure directly or indirectly. Owing to the sensor assembly, the fabric condition can be monitored even with measurement arrangements that already exist in the machine element, this taking place surprisingly by utilizing a cross-directional profile measurement of the nip between the machine element and the fabric, for example. In other words, with the invention it is possible to diversify the purpose of use of an existing sensor assembly in a surprising way without major installation or modification work. If the machine element is already equipped with a sensor assembly for measuring the cross-directional profile of nip force of a nip, for example, the method according to the invention can even be a merely program-based implementation in the machine control automation. In this case, it is very simple to implement.

Some examples of moving continuous elements include fabrics, already referred to above, as well as rolls formed from the web. By applying the same principle, it is also possible to provide monitoring methods for parent rolls and shipping rolls, which do not involve dangerous working methods during the machine operation or other work safety risks while taking the measurements. Correspondingly, work safety related to fabric condition monitoring also improves, as it can also be performed utilizing the method. Other advantages of the invention are that the systems are automated and real-time. Other additional advantages achieved with the method, system and computer program product according to the invention become apparent from the description, and the characteristic features are set forth in the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring more particularly toFIGS. 1-8:

FIG. 1is a rough diagrammatic view of one example of an embodiment of the invention, which in this case is a fiber web machine10. In addition to a fiber web machine, the invention can also be utilized in a paper finishing machine, for example. Some examples of these may include slitting, calendering, coating, surface sizing and rewinding. A fiber web or paper finishing machine includes one or more sub-entities11-14. A fiber web machine may include the following as subsequent sub-entities (FIG. 1from left) located in the web travel direction, i.e. in the machine direction: headbox (not shown), web forming section11, press section12, dryer section13, one or more possible finishing devices (not shown), and reel14. A finishing device may be an integral part of the machine line (online) or a separate sub-entity of its own (offline). Other components may of course exist between parts11-14. Thus, the order set forth is not intended to limit the invention in any way. For example, after the dryer section13, calendering, coating, surface sizing and/or after-drying can take place, these being mentioned in this context merely as a few examples prior to the reel14.

At least some of the sub-entities11-14of the fiber web machine10have one or more rotating machine elements41. Some examples of rotating machine elements41are rolls and cylinders15,16,18,19that are in contact with or otherwise indirectly influence the web W. At least one fabric32,33may be arranged to travel via rolls and cylinders15,16, such as is the case with sub-entities11-13, for example. Fabrics32,33rotate in fabric runs22,23. In addition to rolls and cylinders, fabric runs22,23are defined by lead rolls17, which belong to rotating machine elements41. Via these, the fabric32,33is set to travel in the fabric run22,23arranged for it. A sub-entity14may also be without a fabric run. This is the case in the exemplifying embodiment related to the reel, i.e. sub-entity14. In this case, the machine elements18,19, i.e. rolls, are in direct contact with the web W. In some positions, the contact of the web W with a rotating machine element and/or a fabric can be one-sided only.

At least in some of the sub-entities12,14of the fiber web machine10, the machine element41is set against a moving continuous element44. According to a first embodiment, the moving continuous element44may be a fabric32,33installed in the fabric run22,23traveling via a machine element41. Thus, according to the first embodiment, the machine element41can define the fabric run22,23. In this case, the rotating machine element41equipped with a sensor assembly24can be one or more lead rolls17of the fabric run22, for example. Via the lead roll17, the fabric32rotates i.e. moves in the fabric run22supported at the wrap angle selected thereto. According to another embodiment, the machine element41does not necessarily need to define, i.e. be part of the fabric run22,23. In this case, the fabric only travels via it in production conditions, for example. This may be the case, for example, in a press nip34in the press section12.

According to a third embodiment, the machine element41can also be a reel drum18of a reel14. In this case, the moving continuous element44is a roll45formed from the web W. A moving roll45, the movement thus being a rotating movement, is formed on the opposite side of the web W relative to the reel drum18. The reel drum18forms, in a manner known per se, a reel nip42together with the roll45formed from the web W. In this case the reel drum18and/or the roll45can be loaded in a manner known per se against each other. Generally, the moving continuous element44can also be called an object element or an object, or even more specifically, a moving object element or a moving object.

FIG. 2shows an example of a rotating machine element41. For example, the machine element41may be a lead roll17that defines the fabric run22in some position of the fiber web machine10, a nip roll16that forms, i.e. is included in a press nip34, a reel drum18located at the reel14, or a web roll19preceding the reel14. However, the machine element41does not necessarily need to define, i.e. participate in defining a fabric run22,23. In this case, it can be said that the fabric32only travels via it. For instance, this may be the case in the press section12, where the fabric32, for example, travels via the press nip34, wherein the second machine element41is a nip roll16equipped with a sensor assembly24. Thus, it can be said that two fabrics32,33travel via the nip roll16. The nip roll16defines, i.e. is part of the fabric run23, wherein the fabric33now travels. The machine element41is equipped with a sensor assembly24measuring force or pressure. The sensor assembly24can be composed of any sensors that measure pressure or force directly or indirectly. By way of example, these may include piezoelectric sensors, piezoceramic sensors, piezoresistive sensors, force sensitive FSR sensors, capacitive sensors, inductive sensors, optical sensors, electromechanical film sensors, etc., which have a sufficient resolution for producing desired information. The sensor assembly24may be formed of a sensor band36or a set of sensors formed of one or more discrete sensors36.

According to an embodiment, the sensor assembly24may be based on, for example, an electromechanical film sensor36known per se. One or more film sensors36may be arranged on the roll shell31and/or cover43. An example of such a diaphragm sensor36are sensors known with the trade name EMFi. Other sensors made of film-like materials operating according to a similar principle can also be applied, such as PVDF sensors. More generally, these can be referred to as pressure sensitive film sensors. The sensor assembly24may typically be installed on the surface of the shell31of the machine element41. In this case, one or more surface layers, more generally a cover43, are on top of it. Under or within the cover43, the sensor assembly24is protected, or it can be installed between the cover layers.

Sensors36can be disposed on the shell31and/or the cover43of the machine element41in a rising manner, as is shown inFIG. 2. The sensor assembly24may also be disposed on the shell31and/or the cover43of the machine element41in a circumferential direction. In that case the sensors may be disposed uniformly distributed on the roll shell31at a distance from each other. In this case, an area free of sensors remains between them. When disposed in a rising manner, the sensors rotate around the shell31of the machine element41in a spiral fashion at a distance from each other. The angle of rotation of the sensors36, more generally, of the sensor assembly24, on the shell31of the machine element41may range between 180 and 320 degrees, for example. The machine element41may be provided with data transfer means20known per se for delivering a measurement signal25generated by the sensor assembly24to condition monitoring38included in the machine control automation. For example, this can be implemented with a transmitter provided at the roll end. With it, the measurement signal25is delivered to a receiver40disposed outside the roll. The receiver40may also be provided with a delivery feature for delivering the measurement signal25further to the machine control automation, to reception means46arranged therein.

The method for condition monitoring of a continuous element44, more specifically a fabric32,33, moving in a fiber web or paper finishing machine is described below in more detail as an exemplifying embodiment referring toFIGS. 3 and 4.FIG. 3illustrates the fiber web machine10ofFIG. 1and condition monitoring38connected thereto, andFIG. 4is a flowchart view of the method at the general level. The condition of a moving continuous element44is monitored with a rotating machine element41. For example, as shown inFIG. 2, a sensor assembly24measuring force or pressure is disposed on the shell31and/or the cover43of the machine element41. Thus the fabric32,33now moves against the machine element41.

As step401of the method, the machine element41equipped with a sensor assembly24is made to rotate against a moving continuous element44, more specifically a fabric32,33. The machine element41equipped with the sensor assembly24may be, for example, a lead roll17included in the fabric run22,23and/or a nip roll16included in the press nip34.

As step402of the method, a measurement signal25is generated between the machine element41and the moving continuous element44, more specifically the fabric32,33, with the sensor assembly24arranged in the machine element41. The measurement signal25formed with the sensor assembly24is proportional to force or pressure generated between the machine element41and the fabric32,33. This force or pressure may vary in the cross direction (CD) of the machine, i.e. in the longitudinal direction of the machine element41.

The measurement signal25generated with the sensor assembly24can be stored. As step403, a cross-directional profile21of force or pressure generated between the machine element41and the moving continuous element44is formed from the measurement signal25. In the case of a fabric32, this can also be referred to as the tension profile21.1of the fabric32.

The cross-directional profile21of force or pressure, more specifically the tension profile21.1of the fabric32, formed in step403can be utilized in step404, which can include two steps404.1,404.2at least partially in a parallel manner. As step404.1, a reference profile35.1is formed for the cross-directional profile21; thus, in this case for the tension profile21.1of the fabric32, using the measurement signal25. This can take place, for example, mainly immediately after installing the fabric32in the fabric run22and/or when it is determined that the fabric32operates in a way optimal for it. In this way, it is possible to know the tension profile21.1of the fabric32as new and thereby in a perfect operating condition. Thus, it is also possible to speak of an essentially new fabric32and the related reference profile35.1. For example, the reference profile35.1is formed by collecting the measurement signal25over a relatively long period that is known to be good as regards the operation of the fabric32, and by calculating the average of it. Thus, the collection of the measurement signal25and the formation of the reference profile35may be mainly continuous-time.

The formation of the reference profile35can also take place with preset periods. The reference profile35is characterized by a preset type of constancy and quality as regards the moving continuous element44that is the target. The aim is to form a reference profile35when the operating conditions of the fiber web machine10and/or the operation of the component of interest are known to be mainly optimal and production is known to take place mainly without disturbances. As regards the fabric32, its operation can then be said to be optimal without any phenomena affecting its ageing. In that case the measurement signal25, from which the reference profile35is formed, is as free as possible of disturbances and phenomena related to ageing. In addition, it is also characteristic of the formation of the reference profile35that it takes place in acceptable operating conditions as regards the condition/quality of the moving continuous element44. The reference profile35of force or pressure between each machine element41and the related moving continuous element44is stored in the machine control automation for use. The reference profile35is used to analyze a momentary cross-directional profile21formed in a position corresponding to the reference profile35, which can be performed as step404.2in parallel with step404.1.

As step404.2of the method, the cross-directional profile21formed from the measurement signal25and representing force or pressure generated between the machine element41and the moving continuous element44, more specifically the fabric32,22, here more specifically the tension profile21.1of the fabric32, is compared with the reference profile35.1already formed for it earlier in step404.1. The cross-directional profile is here measured directly, i.e. immediately between the machine element41and the fabric32,33(at lead roll17and nip roll16). The measurement of the cross-directional profile can also be indirect. This is the case, for example, in the embodiment related to a press nip34, set forth somewhat later in the description. In that there may be another fabric33between the nip roll16, equipped with a sensor assembly24, and the fabric32.

Thus, the purpose of the comparison, performed as step404.2, is to identify variation in the cross-directional profile21of force or pressure, more specifically the tension profile21.1of the fabric32, relative to the reference profile35. More precisely, this comparison may be a mutual comparison of a momentary cross-directional profile21and a reference profile35formed over a longer period for identifying variation, a difference or an equivalent change in accordance with a preset criterion in the cross-directional profile21relative to the reference profile35. A variation, difference or change indicates a change in the condition or quality of the moving continuous element, more specifically the fabric32.

As step405, information37, particularly visual information, is produced from the comparison for monitoring the condition of the moving continuous element44, more specifically the fabric32,33. More specifically, the comparison can be used to produce visual information37regarding the level of variation, difference or equivalent change determined in the cross-directional profile21and its point of manifestation in the cross-machine direction (CD).

If it is determined in step406that a variation, difference or change in accordance with the preset criterion was found, it is possible to proceed to step407for performing actions regarding the condition or quality of the continuous element44, more specifically the fabric32. Along with these actions, or if changes in accordance with the preset criterion were not identified in step406, the execution of the method is continued. The method can be executed as a parallel continuous loop at least regarding the comparison. The generation of the reference signal35, i.e. step404.1, may be periodic in accordance with the preset criterion. For example, it can be performed for a newly introduced moving continuous element44(FIG. 5, fabric). On the other hand, it may also take place as a specific calibration run. In this case, the reference profile35is formed according as the condition of the moving continuous element44changes (FIG. 6, reeling).

FIG. 5is a flowchart view of an example of a method according to the invention for monitoring the condition of the fabric32, whereasFIG. 7illustrates, at a general level, information37produced from profile measurement data for monitoring the condition of the fabric32. Thus, the continuous element44is now the fabric32installed in the fabric run22defined by the machine element41, a lead roll17in this case. Correspondingly, the cross-directional profile21of force or pressure is the tension profile21.1of the fabric32, of which a basic example is shown inFIG. 7. The same flowchart and principle would also be applicable to the condition monitoring of a fabric performed at a roll nip, such as a press nip34, as is explained somewhat later. In this application of the method, the sub-steps are mainly similar to those already described inFIG. 4. The reference profile35.1is now formed for an essentially new fabric32. Before forming it, the fabric32is installed in the fabric run22, wherein it moves via a machine element41, in this case a lead roll17, equipped with a sensor assembly24. The steps501-503can be corresponding in principle to what is set forth inFIG. 4. As step504.1, a reference profile35.1is formed for the tension of an essentially new fabric32. This may be performed mainly immediately after installing the fabric32in the fabric run22. In some cases, however, the fabric32may be allowed a running-in period, relatively short in relation to the entire life of the fabric32, before forming the actual reference profile35.1. In that the fabric32will achieve the optimal operating condition designed for it. Thus, in this context the definition “essentially new fabric” may be understood as fabrics of the aforementioned kind, for example.

According to an embodiment, a differential profile of the fabric32can be formed in the comparison performed as step504.2. The differential profile is obtained when the stored reference profile35.1is deducted from the real-time tension profile21.1measured continuously during production. In this case, the profile measurement of fabrics32and comparison takes place automatically and during production and does not require a shutdown. In addition, the operator does not need to enter dangerous conditions going inside the machine to perform the aforementioned observation. The computed differential profile can be used to form indices, for example, representing the condition of the fabric32. Indices formed as step505can be displayed as trends, for example. In this way, it is possible to easily see any changes taking place over time in the condition of the fabric32.

One or more indices representing the condition of the fabric32can be formed. At least one of the following can be formed as indices: excessive deviation of the differential profile, excessive deviation of the real-time tension profile21.1, excessive peak-to-peak variation of the differential profile and/or too high/low an individual value in the tension profile21.1. These can be displayed as trends, for example, in the control room user interfaces.

As information37, it is possible to produce a real-time production-time tension profile21.1of the fabric32and, in addition thereto, the aforementioned computed differential profile, in which the mainly real-time tension profile21.1has been deducted from the reference profile. These can be displayed in the control room, for example, as profile displays or a color chart and/or a waterfall plot on the operator display panels. From these, it is easy to see how the tension profile21.1of the fabric32has changed since new. Based on the indices, an alarm can be given when values start to approach alarm limits. When the limit is exceeded, an alarm is given.

The development of the indices can also be compared with corresponding measurements taken and stored during the life of earlier fabrics. The comparison can be made manually or automatically. Based on the comparison, alarms can be activated, for example, when the indices approach values that are based on empirical information, which indicate the fabric32reaching its end of life. In that case it is possible to learn to alarm even automatically more accurately when the values start to approach such values that indicate the fabric32reaching its end of life (values measured before the change of earlier fabrics represent the condition of an end-of-life fabric). Thus, it is possible to schedule, in a controlled manner, the correct point of time for the replacement of the fabric32.

The aforementioned aspects are analyzed as step506either automatically by condition monitoring or by the operator. If the preset criterion is met, reconditioning actions regarding the fabric32can be taken as step507, or the fabric32can be replaced with a new one if determined that it has finally reached its end of life.

In addition, as step506, it is also possible to compare the difference of tension profiles21.1following each other temporally, i.e. successive tension profiles. If a change is determined in these, a sudden fabric failure, for example, can be identified based on it. The system can learn to identify sudden fabric failures, for example, by examining the difference between adjacent measurements of the tension profile: an excessive difference represents a failed point that has emerged in the fabric. The tension profile and its trend also show other things, which indirectly affect the operation and lifecycle of fabrics. For example, these include the performance of stretchers and guides and the total tension of the fabric32.

With the aforementioned method, changes in the mechanical condition of the fabric32are identified. According to another embodiment, another reference profile35can be formed for the fabric32,33(in addition to or instead of the tension profile measurement) by measuring the cross-directional profile of nip pressure of a loadable press nip34formed between two rolls15and16. The press nip34is formed, in a manner known per se, by two rotating rolls15,16that are placeable and loadable against each other, with at least one fabric32,33traveling between them. At least one of the rolls16is equipped with a sensor assembly24. In this case, the fabric run22,23includes at least one press nip34. As the design and principle of operation of the roll nip and the rolls15,16included in it are known per se for those skilled in the art, it is not necessary to explain them more profoundly in this context. At a roll nip, water is removed from the web that passes through the roll nip. Since roll covers wear off slowly, a change in the nip load profile visible over the change interval of the fabric32,33is mostly due to wear/compacting/soiling of the fabric32,22passing via the press nip34. In the press, the machine element41can define the fabric run22,23. However, it should also be noted that in the press, the machine element41does not always necessarily need to define, i.e. be part of the fabric run22,23. In this case, the fabric32only travels functionally via the machine element16, as is the case in the press nip34, for example.

This measurement and the formation of the reference profile can also be performed mainly immediately after the installation of the fabric32,33. In some cases, however, the fabric32,33may even here be allowed a running-in period, relatively short in comparison with the entire life of the fabric32,33, before forming the actual stabilized reference profile35.1. The real-time cross-directional profile of the press nip34continuously formed at each point in time is compared with the reference profile35.1formed with the new fabric32,33for determining the change caused by the wear of the fabric32,33. According to an embodiment, in the comparison is formed a differential profile for the cross-directional profile of the press nip34and the reference profile35.1formed for it. Based on the differential profile, indices, for example, are faulted for the condition of the fabric32,33, which are then displayed as trends, for example.

In the same way as for the fabric tension in the embodiment set forth above, here, too, at least one of the following can be formed as indices for the condition of the fabric32,33: deviation of the differential profile, deviation of the real-time cross-directional profile of the press nip34, peak-to-peak variation of the differential profile and/or too high/low an individual value in the cross-directional profile of the press nip34. In addition, as information37, it is possible to produce a cross-directional profile and a differential profile of the press nip34, which can be displayed as profile displays, a color chart and/or a waterfall plot, for example.

The invention brings forward the change caused by the wear of the fabric32,33, and again, limit values can be defined for this, according to which the wear of the fabric32,33is identified and its replacement interval can be optimized. It is also possible to examine the set-up of a new fabric32,33via a nip profile and tension profile measurement. The sub-steps of the method can be similar to those with the lead roll17, except for that in this case, a rotating machine element41equipped with a sensor assembly24is naturally one of the rolls16in the press nip34. For example, this measurement can be used to examine blocking and wearing of a fabric32,33.

FIG. 6is a flowchart view of an example of a method according to the invention for monitoring the condition of a roll45formed in a reel14, andFIG. 8, in turn, illustrates at a basic level information37produced from profile measurement data in roll forming. In this embodiment, the machine element41is thus a reel drum18, while the continuous element44is a roll45to be formed from the web W. The roll45is formed on the opposite side of the web W relative to the reel drum18.

Steps601and602may correspond to those described above regarding their basic principles. The cross-directional profile21to be formed, i.e. in this case the linear load profile formed at the reel drum18between the reel drum18and the roll45to be formed from the web W corresponds to the hardness profile21.2of the roll45. As step602, at the reel14, a load trend in the machine direction MD of the nip42between the reel drum18and the roll45is additionally formed at the reel drum18. For both of these, reference profiles35.2are formed in step604.1using reeling parameters that are different relative to the diameter of the roll45.

In addition to the above measurements, the tension profile and the tension trend in the machine direction MD of the web W arriving at the reel14can be measured at the web roll19preceding the reel drum18, more generally the reel14. This gives a tightness profile for the roll45.

The hardness profile and the tension profile of the reel14are displayed to operators in the control room. Then it is not necessary to measure the profiles of the rolls45by going between the rails of the reel14. The web tension level and the reel14nip load level, which are seen from the above measurements, determine the tightness of the roll45relative to the diameter. The hardness profile and the tension profile, as well as the nip load of the reel14, determine the profile of the tightness of the forming roll45and how uniform the roll45is. These values defined with the sensor assembly24can be displayed to operators as profiles, trends and combined hardness indices, for example. In addition to these, other quality parameters of paper can be used for support. For example, in addition to the nip load and web tension, the effect of paper friction and permeability can be included—the higher the permeability or friction, the smaller the value needed for the web tension and the nip load.

As step605, a trend representing the tightness of the roll45, which can be displayed in the control room, is produced as information from the different machine directional MD parameters and/or indices formed based on the comparison, representing their combined effect. This can be used to search deviations in accordance with a preset criterion, and when such is found, an alarm can be given as step606. In that case the operator, as step607, can assess the need of tightening reeling parameters and carry out the necessary actions.

As step605, a quality index can also be produced as information for cross-directional hardness profiles21.2, tension profiles and their combination. This can be displayed as a trend, and an alarm can be activated when detecting an excessive change or an extreme value in the trend, for example. A quality index can be formed, for example, based on deviation, peak-to-peak variation and/or differences between the edges of the roll45and the center area. This index can be displayed in the control room as a trend, for example, and again, excessive variations or extreme values in the trend may trigger an alarm, based on which the operator can carry out profile improving actions as step607. For example, if there is a hard hump at the roll edge, the operator can first check whether edge trimming operates adequately, and if this is the case, then increase calendar load at the edges and/or profile the basis weight downwards.

The development of indices relative to the roll45diameter can be compared (manually or automatically) with corresponding measurements taken during the production of already completed rolls and indices and their development. Thus, it is possible to learn to alarm even automatically more accurately when the values start to approach such values that require operator actions. Indices can then be analyzed in order to identify risks of sudden damaging of the roll45. The system can also learn to identify risks of sudden damaging of the roll45, for example, by examining the difference between adjacent hardness measurements: an excessive difference represents a risk for structural damage of a parent roll. Correspondingly, an excessive difference in the tension profile represents a risk for a web break.

Limit values between the alarm limits for different parameters/indices can be determined by measuring the rolls45with different reeling parameters and by examining their quality with traditional methods. In other words, in this case, automatic measurements/indices/alarms are calibrated to represent the same as operators have earlier performed according to the prior art.

At the reel14, the method can also be used to identify excessive vibration of parent/shipping rolls and to also alarm of these.

In turn,FIGS. 7 and 8show graphs of cross-directional profiles21.1,21.2for applications shown inFIGS. 5 and 6. It will be evident for those skilled in the art that the shapes of the profiles can in reality vary even greatly from these. The position axis, i.e. the positions on the shell31of the machine element41in the cross-machine direction CD, is shown in the horizontal direction, and the force axis is shown in the vertical direction. InFIGS. 7 and 8, the reference profile35.1,35.2is drawn with a continuous line. It represents the cross-directional profile in conditions where the tension of the fabric32and/or the cross-directional profile of force of the press nip34at the fabric32is as desired (FIG. 7) and the hardness and tightness of the roll45to be formed are as desired (FIG. 8). The reference profile35.1can have been formed immediately after the installation of the fabric32. The reference profile35.2can have been formed on a roll or a set of rolls of an equivalent grade that is known to be good. In addition, instead of one profile, the reference profile35.2may be a set of profiles that considers the diameter growth of the roll45. In other words, as the diameter increases while forming the roll45, the reference profile35.2used in the comparison will also change.

The cross-directional profiles21.2,21.2drawn with broken lines inFIGS. 7 and 8illustrate the mainly real-time profile measured on the machine element41.FIG. 7can represent, at a basic level, a tension measurement of a fabric32on a lead roll17and/or a cross-directional profile measurement of nip pressure of a press nip34. In the case of a fabric32, this could be a situation where the tension measured at the lead roll17of the fabric32is uneven, which leads to problems in its operation. On the other hand, in the case of a fabric32, this could also be a situation where the fabric32has become locally compacted, which also leads to problems in its operation. In this case, the measurement is made at the press nip34. Correspondingly, in the case of the roll45shown at a basic level inFIG. 8, this could be a situation where the hardness and/or tightness of the roll45shows unevenness. These manifest a problem related to roll forming and/or web forming.

These mainly real-time measured cross-directional profiles21.1,21.2clearly show the difference relative to the reference profiles35.1,35.2formed. The comparison of the measured cross-directional profiles21.1,21.2with the reference profiles35.1,35.2can be carried out online, mainly automatically. In this case, the measurement signal25shows whether the measured profile changes, and if it does, the type of the change.

Detection of variations, differences and changes from the profiles and, for example, indices formed therefrom, more generally the comparison, can be performed mainly continuous-time. Information37can be further processed compared to mere profiles. For example, it can include different kind of indices, trends and tables. Information37can be published on the display panel27of the information system38specifically to each position at predefined intervals or at user-defined intervals, for example.

In addition to a method, the invention also relates to a system for monitoring the condition of a continuous element44, more specifically a fabric32, moving in a fiber web or paper finishing machine. Condition monitoring is arranged to be performed with a rotating machine element41, which is equipped with a sensor assembly24that measures force or pressure. The moving continuous element44is arrangeable to move against the machine element41. The system includes a sensor assembly24that measures force or pressure and is disposed on a shell31and/or a cover43of one or more machine elements41for generating a measurement signal25between the machine element41and the moving continuous element44, processing means47, user interface means27and memory means26. The processing means47is arranged to form a cross-directional profile21of force or pressure arranged to be generated between the machine element41and the moving continuous element44, from the measurement signal25. The user interface means27is provided for examining the cross-directional profile21.

The continuous element44is a fabric32,33installed in a fabric run22,23arranged to travel via the machine element41. The cross-directional profile21of force or pressure is a tension profile21.1of a fabric32,33and/or a cross-directional profile of nip pressure of a press nip34, for example. The rotating machine element41equipped with the sensor assembly24is a lead roll17of the fabric run22or a nip roll16included in the fabric run23, for example. The fabric32,33is arranged to travel in the fabric run22,23via the lead roll17and/or the nip roll16.

In the system, the measurement signal25formed with the sensor assembly24is arranged to be used to form, with the processor means47, a reference profile35.1for the cross-directional profile21of force or pressure arranged to be generated between the machine element41and the moving continuous element44, more specifically a fabric32,33, more specifically for the tension profile21.1or the fabric32,33and/or for the cross-directional profile of nip pressure. The reference profile35.1is formed after installing the fabric32,33in the fabric run22,23. Thus, its operation essentially corresponds to a new fabric. The reference profile35is arranged to be stored in the memory means26.

In turn, the processing means47is arranged to compare the cross-directional profile21of force or pressure arranged to be generated between the machine element16-18and the moving continuous element44, more specifically the fabric32,33, more specifically the tension profile21.1of the fabric32,33and/or the cross-directional profile of nip pressure, with the reference profile35.1. The purpose of the comparison is to identify variations, differences and changes in the profiles. In addition, the processing means47is also arranged to define the reference profile35.1and compute the differential profile.

In turn, the user interface means27is arranged to produce, for example, visual information37from the comparison, for monitoring the condition of the moving continuous element44, more specifically the fabric32,33. The system is arranged to carry out the sub-steps of the method described above in a computer-implemented way, for example. It is also possible to add temperature, moisture and other similar sensors to the system.

The rotating machine element41can be arranged to define a fabric run22. In this case, it can be a lead roll17of the fabric run22, for example. On the other hand, the rotating machine element14can also be a nip roll16. A nip roll16can also be arranged to define a fabric run23, in which the condition of the fabric33traveling therein is monitored. On the other hand, the nip roll16can also be such, via the nip34of which the fabric32,33is arranged to travel.

In addition to a method and a system, the invention also relates to a rotating machine element41. It includes a shell31, a cover43disposed on the shell31and a sensor assembly24installed in a spiral fashion under or within the cover43. The machine element41is used in the method or system described above for monitoring the condition of a fabric32,33.

A rotating machine element41may be in the system, for example, a lead roll17defining the fabric run22and/or a nip roll16forming a press nip34and defining the fabric run23, via which a fabric32belonging to a different fabric run22can travel.

In addition to a method and a system, the invention also relates to a computer program product29. The computer program product29, which may be placed, for example, in a suitable storage media or is downloadable over an information network, has a computer program logic30configured to provide the different applications of the method described above for monitoring the condition of the fabric32,33.

The methods, systems and computer program logics30according to the invention can be arranged as part of the machine control automation, for example. The condition monitoring of fabrics32and the monitoring of quality and/or the hardness of the roll45can be automatic and take place mainly in continuous-time. Thus, by using the methods described above, it is possible to provide condition monitoring methods, which do not involve work safety risks while performing measurements. In addition, an advantage is that the systems are automated, real-time and learning. In the case of rolls45, the invention can be applied to all of the reeling steps of a fiber web and paper finishing machine10(parent rolls and shipping rolls as examples).

It is understood that the above description and the figures related thereto are only intended to illustrate the present invention. Thus, the invention is not only limited to the embodiments proposed above or those defined in the claims, but many different variations and modifications of the invention, which are possible within the inventive idea defined in the appended claims, will be evident to those skilled in the art.