WO2012117160A1

WO2012117160A1 - Method for condition monitoring of process element, monitoring system, and process element

Info

Publication number: WO2012117160A1
Application number: PCT/FI2012/050192
Authority: WO
Inventors: Rauno Enqvist; Juha METTÄLÄ; Petri Nieminen
Original assignee: Metso Fabrics Inc.
Priority date: 2011-02-28
Filing date: 2012-02-27
Publication date: 2012-09-07
Also published as: FI20115200A0; FI20115200A

Abstract

The invention relates to a method for monitoring the condition of a process element, a monitoring system, and a process element. The process element (1) comprises at least one wear detector (3) arranged inside the structure of the element at a wear thickness (HK) from the outer surface (8) of the element being monitored.

Description

Method for condition monitoring of process element, monitoring system, and process element

Background of the invention

[0001] The invention relates to a method for monitoring the condition of a process element. During operation, the process element is run in an industrial process device, such as paper machine or filter device, wherein the process element helps support the material being processed. The process element moves in relation to the process device. In the method, the wear of at least one outer surface of the moving process element is monitored during its operation.

[0002] The invention further relates to a monitoring system and a process element. The field of the invention is described in the preambles of the independent claims of the patent application.

[0003] The process element wears during operation, as it moves in the process device. The outer surface of the process element may rub against the members guiding it, such as rolls, guide rolls and guide or filter surfaces, in which case its outer surface wears. Further, the relative movement between the process element and the material being processed may also wear the outer surface of the process element. The wearing of the process element may cause changes in the process yield and quality. In addition, the process element may also wear to the point that it breaks down during operation and causes an unplanned production shutdown - or at worst it may even damage the process equipment.

Brief description of the invention

[0004] It is an object of the present invention to provide a novel method and system for condition monitoring of a process element, and a novel process element.

[0005] The method of the invention is characterised by furnishing the process element with at least one wear detector that comprises connection means for non-contacting remote reading; arranging the wear detector inside the process element at a predefined wear thickness from the original outer surface being monitored; using the process element to support the material being processed in a paper machine or filter device, whereby the process element wears and material is removed from its outer surface; monitoring the change in the thickness caused by the wear of the process element by estab- lishing a connection to the wear detector from at least one wear monitoring unit external to the process element; and determining the wear of the process element outer surface on the basis of the setting up of the connection.

[0006] The monitoring system of the invention is characterised in that the system comprises at least one wear detector that comprises connection means for non-contacting remote reading; the wear detector is arranged at a predefined wear thickness from the original outer surface of the process element being monitored; the system comprises at least one wear monitoring unit for establishing a connection between the unit and the wear detector; and the wear monitoring unit is arranged to determine a change in the thickness caused by the wear of the monitored process element outer surface on the basis of the setting up of the connection between the wear monitoring unit and wear detector.

[0007] The process element of the invention is characterised in that the process element comprises several wear detectors for monitoring the change in the thickness caused by wear; the wear detectors comprise connection means for non-contacting remote reading; the wear detectors are arranged inside the process element; and the wear detectors are arranged at least at two different predefined wear thicknesses from the original process element outer surface being monitored.

[0008] The idea is that the process element is furnished with remotely readable wear detectors that are arranged at a desired wear thickness from the process element outer surface being monitored. When the process element is run in the process device, the outer surface being monitored wears and material is removed from it. This affects the setting up of the remote connection between the wear detectors in the process element and the monitoring unit outside the process element. The monitoring unit has a control strategy, according to which the monitoring unit determines the wear of the process element.

[0009] One advantage is that it offers a simple solution for wireless remote monitoring of the wear of the process element. The wear detector may be of ON/OFF type, in which case it does not need to comprise any measuring sensors or means. This type of detector may be inexpensive in price and operationally reliable. Further, arranging the wear detector inside the process element is quite easy, as is the selection and setting of the wear thickness to be monitored. [0010] The idea of an embodiment is to furnish the process element with several wear detectors.

[0011] The idea of an embodiment is to furnish the process element with several wear detectors that are arranged at least at two different wear thicknesses to be monitored from the original outer surface of the process element. Further, there may be several wear detectors adapted for each wear thickness, whereby it is possible to monitor two or more locations on the outer surface of the process element, for instance the edge areas and web area or filter section, depending on the application.

[0012] The idea of an embodiment is to furnish the process element with several wear detectors that are arranged at the same wear thickness, and to take two or more wear detectors into account in the monitoring unit when determining the wear degree of the process element. With this embodiment, it is possible to improve the reliability of monitoring, since the determination of wear is based on two or more detectors. When the process conditions are especially severe, this embodiment may be beneficial.

[0013] The idea of an embodiment is that the process element has opposite outer surfaces and the wear of both are monitored with one or more wear detectors. This embodiment may be used in filter devices, for instance, where the process element is a band-like filter element with both surfaces alternately exposed to wear.

[0014] The idea of an embodiment is that the process element is a textile structure. The process element may be formed of synthetic threads, such as polymer threads. Alternatively, the threads may be of metal. The process element may be formed by weaving, knitting, winding, or it may be a moulded structure with support threads and moulded elastomer. The process element may be made directly into the usage form for each application, or it may for instance be made of a preformed textile structure, such as fabric, by cutting and sewing. Further, the process element may have one or more seams or other sections enabling its installation.

[0015] The idea of an embodiment is that the process element is a paper machine belt, which in this patent application refers to an elongated element used in a paper machine, board machine or pulp processing device. Typically, during use, one outer surface of the paper machine belt is against a fibre web or corresponding material being processed. The paper machine belt may be one of the following, for example: a pulp fabric, drying fabric, press felt, shoe press belt or belt, paper machine transfer belt or support belt. The paper machine belt may be a textile structure, metal band or separate moulded cylindrical sheath.

[0016] The idea of an embodiment is that the process element is a moving filter element intended to be run in a filter device. The filter element may be one of the following, for instance: a band filter belt, disc filter bag, drum filter element or cleaner felt. The filter element may be a textile structure.

[0017] The idea of an embodiment is that a recess according to the wear thickness is formed on the process element outer surface being monitored, and the wear detector is arranged at the bottom of the recess. The recesses may be formed already when the basic structure of the process element is made or, alternatively, the recesses may be formed in a separate step in connection with the finishing of the element, for instance. The recesses may be formed by removing material from the outer surface of the process element. Any suitable technique, such as cutting, chip removal, or electromagnetic radiation, may be used in removing material.

[0018] The idea of an embodiment is to arrange between the wear detector and process element outer surface at least one protective layer that covers the wear detector toward the outer surface of the process element. The wear detector may be arranged in a recess opening toward the outer surface of the process element and the recess filled with a protective layer after the wear detector has been arranged at its bottom. The protective layer may be a suitable mass or it may be a separate piece that is fastened to the process element.

[0019] The idea of an embodiment is to arrange between the wear detector and process element outer surface at least one protective layer that prevents the establishment of a connection between the wear monitoring unit and wear detector. The protective layer may form a barrier to radio-frequency wave penetration, or it may prevent the transmission of a light beam through it. The wear monitoring unit may have a control strategy that interprets the process element to have worn to the extent of the wear thickness of the wear detector in a situation where a remote connection is established between the wear monitoring unit and wear detector after the protective layer has worn off at least partly.

[0020] The idea of an embodiment is that at least one protective layer covers the wear detector to prevent the establishment of a connection between the wear monitoring unit and wear detector. The wear monitoring unit is arranged to determine the wear degree on the basis of the strength of the established connection. When the outer surface of the process element and, at the same time, also the protective layer wear, a connection begins to form already before the protective layer is fully worn off. A thinning protective layer cannot fully prevent the establishment of a connection.

[0021] The idea of an embodiment is that the wear detector is arranged inside the basic structure of the process element, whereby it is invisible from the side of the outer surface being monitored. Between the wear detector and the outer surface being monitored, there is then one or more structural layers that prevent the establishment of a connection between the wear detector and wear monitoring unit. When the process element outer surface being monitored wears so does the structural layer preventing the establishment of a connection, and as a result, the strength of the connection established between the wear detector and wear monitoring unit increases according to the degree of wear. The stronger the signal or corresponding connection is, the more the outer surface being monitored has worn.

[0022] The idea of an embodiment is to establish a connection between the wear detector and wear monitoring unit. When the connection is established in a normal manner, it is interpreted in the wear monitoring unit as an allowed wear of the process element. The process element is further interpreted to have worn to the extent of the wear thickness corresponding to the wear detector in a situation where the wear detector has malfunctioned as a result of the process element outer surface having worn to the wear detector. The wear detector may malfunction so that it detaches from the process element or one or more of its parts are broken.

[0023] The idea of an embodiment is that the connection established between the wear detector and wear monitoring unit is based on the use of radio-frequency waves.

[0024] The idea of an embodiment is to use as the wear monitoring unit an electronic terminal and to establish a connection between it and the wear detector by means of radio waves. The wear monitoring unit and wear detector may comprise a transmitter and receiver.

[0025] The idea of an embodiment is that the wear detector comprises a Radio Frequency Identification (RFID) tag. The wear sensor may be a passive RFID tag which comprises no power source of its own but the ex- tremely low electric current required by its operation is induced from radio- frequency scanning received by the antenna contained therein and transmitted by the wear monitoring unit acting as a reading device. By means of this induced current, the tag is able to transmit a response to an inquiry sent by the wear monitoring unit. In other words, the wear monitoring unit searches (scans) the environment for a tag, and the tag transmits an ID code (response) stored in the microchip after the scanning has induced thereto the electric current necessary for the transmission. The RFID tag may be read at a radio frequency without visual connection, and it may even be read through obstacles. In addition, the wear monitoring unit acting as the RFID reading device may read simultaneously several RFID tags that may be arranged at different wear thicknesses from the process element outer surface being monitored. The size of the wear detector based on RFID technology may be very small, which facilitates its arrangement in the structure of the process element. In addition, this type of wear detector is inexpensive, reliable and highly available.

[0026] The idea of an embodiment is that the wear detector is arranged to establish a radio-frequency connection with the monitoring unit and comprises at least one antenna part. The antenna may for instance be a loop formed of metal wire and cover a predefined surface area of the outer surface of the process element. A sensor may cover the edge section or web section of the paper machine belt, for instance. When the antenna part is damaged through wear, no connection can be established to the wear monitoring unit.

[0027] The idea of an embodiment is to establish an optical connection between the wear detector and wear monitoring unit. The wear monitoring unit may then comprise a light source, such as laser or LED. Further, the wear detector may comprise a reflector that reflects the light back to the wear monitoring unit when there is no obstacle between the wear detector and wear monitoring unit. As the process element wears, the reflector may damage, and no connection can be established, which will be interpreted to indicate that the process element has worn to the extent of the wear thickness corresponding to the wear detector. Alternatively, the optical connection is intentionally prevented by a structural or protective layer, and after the layer has worn off, the optical connection is established, which will be interpreted to indicate that the process element has worn to the extent of the wear thickness corresponding to the wear detector. [0028] The idea of an embodiment is to furnish the process element with several wear detectors that are arranged at least at a predefined critical wear thickness from the original outer surface of the process element and at one or more allowed distances predicting the wear degree from the original outer surface. This way, it is possible to get an indication of various wear degrees and to monitor the development of wear. The wear detectors may be arranged to detect a wear degree of 25%, 30% and 40%, for instance.

[0029] The idea of an embodiment is that the process element is a pulp drying machine fabric or pulp wire that is run in a pulp processing device. The original thickness of the pulp wire may be 2 mm and its critical thickness 1 .6 mm. The highest allowed wear is then 0.4 mm. One or more wear detectors are then arranged at a distance of 0.4 mm from the bottom surface of the pulp wire, that is, the outer surface on the machine side which is the critical outer surface for wear in a pulp wire. The wear detectors are arranged at one or both edge areas of the wire. Further, wear detectors may also be arranged at a distance of 0.1 mm, 0.2 mm and 0.3 mm from the outer surface.

[0030] The idea of an embodiment is that the wear monitoring unit comprises a control unit with one or more control strategies for interpreting and processing information obtained from one or more wear detectors.

[0031] The idea of an embodiment is that the wear monitoring unit comprises telecommunication means for transmitting monitoring data, alarms, reports and other required data onward. Wear information may be transmitted to the control unit of the process device, condition monitoring system, or electronic terminal, such as mobile phone or computer.

Brief description of the figures

[0032] Some embodiments will be explained in more detail in the attached drawings, in which

Figure 1 is a schematic representation of a process element that is a belt in the form of a closed loop that may be run in a process device and is furnished with wear detectors,

Figure 2 is a schematic representation of a part of a process element with a textile structure, as seen from the top,

Figure 3 is a schematic representation of the cross-section of the process element of Figure 2, as seen in direction A-A, Figure 4 is a schematic cross-sectional representation of a part of a process element, in which the malfunction of a wear detector is arranged to indicate wear,

Figure 5 is a schematic cross-sectional representation of a part of a process element with wear detectors arranged at different wear thicknesses,

Figure 6 is a schematic cross-sectional representation of a part of a process element, the wear of both opposite outer surfaces of which is monitored by wear detectors,

Figure 7 is a schematic cross-sectional representation of a part of a process element, in which a wear detector is arranged between structural layers instead of in a recess,

Figure 8 is a schematic representation of a part of a process element, in which the wear detectors comprise antenna parts having monitoring areas, as seen from the top,

Figure 9 is a schematic representation of a part of a paper machine and the utilisation of wear sensors,

Figure 10 is a schematic representation of a disc filter comprising several sectors,

Figure 1 1 is a schematic representation of one sector of a disc filter and a disc filter bag arranged on top of it, the bag being a process element and having wear detectors.

[0033] In the figures, some embodiments are shown in a simplified manner for the sake of clarity. In the figures, like reference numerals identify like elements.

Detailed description of some embodiments

[0034] Figure 1 shows a process element 1 that is an elongated band-like belt with a length in the machine direction MD and width in the cross direction of the process device. During operation, the process element moves in the machine direction MD. The process element 1 may be made into the shape of a closed loop or it may have a seam 2 for connecting its ends and forming a loop. The process element 1 may be a paper machine belt or a belt used in a filter device. It should be mentioned that the belt need not be a closed loop, and in some embodiments, it may also be a band-like piece.

[0035] The process element 1 may on its cross-direction edges have edge areas R and a web area K between them. Further, the process element has opposite outer surfaces, of which a machine surface T is on the process device side and a web surface P is on the side of the material being processed or supported. The wear of the outer surface of the process element 1 may be monitored using a wear detector 3. There may be one or more wear detectors 3, and they may be arranged on both outer surfaces depending on what the process element is and where does wear take place. A wear monitoring system also consists of one or more wear monitoring units 4 external to the process element 1 to determine the wear of the process element. The wear monitoring unit 4 establishes a remote connection with the wear detector 3, and this connection establishment is utilised in determining the wear of the outer surface of the process element 1 .

[0036] Figure 2 shows a process element 1 with a textile structure comprising threads. It may be a woven structure with machine-direction MD threads 5 and cross-direction CMD threads 6. The structure may comprise one or more layers. Instead of weaving, the textile structure may be formed by winding, for example, or it may have a support structure made of threads, around which polymer layers are moulded. There may be several wear detectors 3 and they may be arranged inside the structure of the process element 1 so that they are invisible toward the surface, or they may be arranged in recesses 7 made into the structure.

[0037] Figure 3 shows an embodiment, in which the web surface P of the process element 1 has a recess 7 that extends to a distance from the original outermost surface 8 of the web surface P. The wear detector 3 may be arranged at the bottom of the recess 7, whereby the distance between the wear detector 3 and outer surface 8 defines the desired wear thickness HK to be monitored, and the size of the thickness may be determined taking into consideration the total thickness HT, criticality and application of the process element 1 . The wear detector 3 may be covered by a protective layer 9 that may be made of a paste, fabric, or some other suitable material. The wear endurance of the protective layer 9 may be dimensioned to correspond to the wear of the basic structure of the process element 1 , in which case the intention is that the protective layer 9 wears in substantially the same manner as the process element during use.

[0038] The wear detector 3 may be a transmitter or a transmitter- receiver that is capable of establishing a radio connection with the wear monitoring unit 4a. The protective layer 9 may be selected to deter or completely prevent the establishment of the connection. When a protective layer 9 deter- ring the transmission of radio waves wears, a connection can be established, which is interpreted in the wear monitoring unit 4 as an indication that the outer surface 8 of the process element 1 has worn to the defined limit. It is also possible to determine the degree of wear on the basis of signal strength. The stronger a signal is formed between the wear detector 3 and wear monitoring unit 4a, the more the outer surface 8 has worn.

[0039] Further, it is possible to establish an optical connection between the wear monitoring unit 4b and wear detector 3. The wear detector 3 may, at its simplest, then be a reflector. When the protective layer 9 has partially or entirely worn off, a light beam transmitted by the wear monitoring unit 4b is reflected back, which is interpreted as an indication that the process element 1 has worn to the extent of the defined wear thickness HK. The wear monitoring unit 4b may have a light source, such as laser.

[0040] For the sake of clarity, the cross-sectional figures 3 to 7 do not show the basic structure of the process element in detail.

[0041] In Figure 4, the outer surface 8 of the process element 1 has a recess 7 that may be made during the manufacture of the process element or thereafter in a separate finishing step for instance by cutting, pressing, or using a technique that utilises electromagnetic radiation. A wear detector 3 is arranged in the recess 7 and positioned at a predefined wear thickness HK from the original outer surface 8. Between the wear detector 3 and wear monitoring unit 4, a connection is established that may be based on electromagnetic radiation, such as radio waves or a light beam. When the outer surface of the process element 1 wears during use and material is removed from it, at some point the wear detector 3 is no longer protected in the recess 3 but is subjected to a corresponding wear effect as the structure of the process element surrounding it. As a result of this, the wear detector 3 finally malfunctions or detaches from the process element 1 , whereby the connection to the wear monitoring unit 4 breaks. The breaking of the connection is interpreted in the control unit of the wear monitoring unit 4 to indicate that the process element 1 has worn to the extent of the wear thickness HK corresponding to said wear detector 3. On the basis of this, the control unit may inform the degree of wear to the control unit of the process device, condition monitoring system, or electronic terminal. The process element 1 may have several wear detectors 3 arranged at the same wear thickness HK, whereby the wear monitoring unit 4 may take several monitoring results into consideration. This improves the reliability of the monitoring even further.

[0042] Figure 5 shows a process element 1 having on one outer surface 8 several wear detectors 3 arranged at different distances from the level of the original outer surface. The element 1 may then have different alarm limits for the wear thickness HK, such as a wear of 10% and 40% of the original thickness. Otherwise, the solution shown in Figure 5 may comprise features shown in other figures of this patent application.

[0043] Figure 6 shows a process element 1 with both outer surfaces furnished with wear detectors 3. In some embodiments, both surfaces of the element 1 are subjected to wear, the development of which needs to be monitored. There may be detectors 3 on opposite outer surfaces of the element 1 at the same or different wear thicknesses. Otherwise, the solution shown in Figure 6 may comprise features shown in other figures of this patent application.

[0044] Figure 7 shows a process element 1 that differs from the embodiments described above in that the wear detector 3 is arranged inside the structure without the recess 7 formed on the outer surface 8 of the element 1 . The wear detector 3 may be arranged in place during the manufacture of the element structure. The detector 3 may for instance be arranged between superposed structural layers when the element 1 comprises several fabric layers, moulded layers or other structural layers. Further, it may be arranged in the structure before coating, in which case it remains under the coating layer. Another possibility is to push a small detector inside the porous structure of the element 1 without breaking the structure. This may be possible in textile structures, for example. Figure 7 shows that between the wear detector 3 and outer surface 8 of the process element 1 , there is a material layer 10 belonging to the element 1 .

[0045] In the solution of Figure 7, wear monitoring may be based on the fact that a signal strengthens between the detector 3 and monitoring unit 4a as the material layer 10 wears. Alternatively, the monitoring may be based on forming an optical, acoustic or some other connection between the detector 3 and wear monitoring unit 4b after the material layer 10 has partly or entirely worn off. It is also possible that the signals used in monitoring penetrate the material layer 10 and a connection is established between the detector 3 and monitoring unit 4a, 4b. When the element 1 has worn so much that the material layer 10 has partly or entirely worn off, the detector 3 or a part thereof may break or detach. As a result of this, a connection cannot be established, which may be interpreted to indicate that the element 1 has worn to the wear thickness shown by the detector 3.

[0046] Figure 8 shows a part of a process element 1 , in the structure of which one or more wear detectors 3 are arranged comprising one or more antenna parts 1 1 for transmitting or receiving signals. At its simplest, the antenna part 1 1 may be a metal thread or the like that can form a loop. This type of antenna part 1 1 is easy to arrange in the structure. In some cases, the threads belonging to the textile structure may be replaced with threads acting as antenna parts. Further, the antenna part may be a film-like piece or a section printed on the structural layer. The monitoring area of the detector 3 may be expanded with the antenna part 1 1 . The antenna part 1 1 may cover the edge part R, for instance, or even the entire web area K of the process element 1 . When the antenna part 1 1 malfunctions due to the wear of the element 1 , a connection is no longer established, and the element 1 is interpreted as having worn to the defined wear thickness. Alternatively, monitoring may be based on the fact that the antenna part 1 1 is covered by a structure or material layers so that the propagation of signals is prevented or weakened. In such a case, the wear of the outer surface of the element 1 improves the establishment of a connection, which may be detected in the monitoring unit 4. The wear monitoring unit 4 comprises a control strategy, according to which it controls monitoring in each case.

[0047] Figure 9 shows a part of a paper machine 12. The paper machine 12 may have several different positions 13a to 13d, in which various paper machine belts may be used, which constitute the process elements 1 of this patent application. A paper machine belt may be used to support and move a fibre web 14 and to affect its properties. By means of one or more wear detectors 3 arranged on the paper machine belt and the wear monitoring unit 4, it is possible to monitor the wear of one or both outer surfaces of the belt. The wear monitoring unit 4 may be arranged in a fixed position 13a to 13d, or it may be a movable device. The wear detection unit 4 may transmit wear-related monitoring information, alarms and other information to the condition monitoring system 15 either wirelessly or over a wire. The condition monitoring system 15 may further transmit information to an information system 16 or a portable electronic terminal 17. [0048] Figure 10 shows a disc filter 18 as an example of using the process element 1 in a filter device. The disc filter 18 has one or more discs that each comprise several sectors 19 connected to a rotating centre channel 20. The disc is rotated in a basin 21 containing a mixture to be filtered. A disc filter bag is arranged on each sector 19, and the bag constitutes a process element 1 of this patent application. The wear of the disc filter bag may be monitored by means of a wear detector 3 arranged thereto. The features described above in this patent application are also suitable for use in monitoring disc filter bags and other moving and wear-prone filter elements.

[0049] Figure 1 1 shows a disc filter bag arranged on a sector 19 and equipped with several wear detectors 3. Detectors 3 may also be arranged at the wider end of the bag, in the mid-section and in the neck area.

[0050] In the following a possible wear detector type and related matters are described briefly. The detector may comprise an RF tag or RFID (Radio Frequency Identification). The RF tag may be very small, which facilitates its installation in the process element. An RF tag is also inexpensive, reliable, and easily available. The detector may be a passive RFID that does not comprise its own power source, but the small electric current required by it is induced by radio-frequency scanning arriving at an antenna belonging to it, the scanning being transmitted by the wear monitoring unit acting as a reading device. By means of this induced current, the tag is able to transmit a response to the inquiry sent by the reading device. In other words, the reading device inquires (scans) the environment for a tag and the detector transmits an ID code (response) stored in a micro-chip after the scanning has induced the electric current necessary for transmission. The RFID may be read on a radio frequency without visual contact and it may even be read through obstacles. In addition, an RFID reader may simultaneously read several RFIDs. The system may comprise one or more portable electronic terminals that may act as reading devices. The portable terminal may be a data collection device, portable computer, palmtop computer, mobile phone, or any other electronic device equipped with the necessary means for remote reading of the tag. The terminal may comprise a control unit belonging to the monitoring system.

[0051] In some cases, the features disclosed in this patent application may be used as such, regardless of other features. On the other hand, the features disclosed in this patent application may, when necessary, be combined to form various combinations. [0052] The drawings and the related description are only intended to illustrate the idea of the invention. The invention may vary in detail within the scope of the claims.

Claims

2101998PC WO 2012/117160 PCT/FI2012/050192 15 Claims

1. A method for monitoring the condition of a process element, in which the process element (1) is run in an industrial process device (12, 18) and in which method the wear of at least one outer surface (8) of the moving process element (1) is monitored during its operation,

characterised by

furnishing the process element (1) with at least one wear detector (3) that comprises connection means for non-contacting remote reading;

arranging the wear detector (3) inside the process element (1) at a predefined wear thickness (HK) from the original outer surface (8) being monitored;

using the process element (1) to support the material being processed in a paper machine (12) or filter device (18), whereby the process element (1) wears and material is removed from its outer surface (8);

monitoring the change in the thickness caused by the wear of the process element (1) by establishing a connection to the wear detector (3) from at least one wear monitoring unit (4, 4a, 4b) external to the process element; and

determining the wear of the process element outer surface (8) on the basis of the setting up of the connection.

2. A method as claimed in claim 1, characterised by using several wear detectors (3) in the process element (1); and arranging wear detectors (3) at least at two different monitored wear thickness (HK) from its original outer surface (8).

3. A method as claimed in claim 1 or 2, characterised by interpreting in condition monitoring as an allowed wear of the process element (1) a situation in which a connection is established between the wear monitoring unit (4) and wear detector (3); and

interpreting in condition monitoring that the process element (1) has worn to the extent of the wear thickness (HK) corresponding to the wear detector (3) in a situation in which the wear detector (3) being monitored has malfunctioned when the outer surface (8) of the process element has worn to the wear detector (3), as a result of which no connection is established between the wear monitoring unit (4) and wear detector (3).

4. A method as claimed in claim 1 or 2, characterised by 2101998PC

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arranging between the wear detector (3) and process element outer surface (8) at least one protective layer (9) that prevents the establishment of a connection between the wear monitoring unit (4) and wear detector (3); and interpreting the process element (1) to have worn to the extent of the wear thickness (HK) of the wear detector (3) in a situation where a connection is established between the wear monitoring unit (4) and wear detector (3) after the protective layer (9) has worn off at least partly.

5. A method as claimed in claim 1 or 2, characterised by arranging the wear detector (3) inside the process element (1) so that between the wear detector and monitored outer surface of the process element there is at least one structural layer (10) that is subjected to wear during the use of the process element; and

determining the wear on the basis of the strength of the connection established between the wear detector (3) and wear monitoring unit (4), in which case the wear is found to be the higher, the stronger the established connection is.

6. A method as claimed in any one of the preceding claims, characterised by

using an electronic terminal as the wear monitoring unit (4); and establishing a connection between an electronic terminal and wear detector (3) by means of radio waves.

7. A method as claimed in any one of preceding claims 1 to 5, characterised by

furnishing the wear monitoring unit (4b) with a light source;

furnishing the wear detector (3) with a reflector; and

determining the wear of the monitored outer surface of the process element on the basis of an optical connection established between the wear monitoring unit (4b) and wear detector (3).

8. A method as claimed in any one of the preceding claims, characterised by

monitoring the wear of a surface of a process element (1) made of textile.

9. A method as claimed in any one of the preceding claims, characterised by

monitoring the wear of a paper machine belt run in a paper machine or a filter belt or filter bag run in a filter device. 2101998PC

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10. A monitoring system, in which the condition of a process element (1 ) is monitored in a paper machine (14) or filter device (18),

c h a r a c t e r i s e d in that

the system comprises at least one wear detector (3) that comprises connection means for non-contacting remote reading;

the wear detector (3) is arranged at a predefined wear thickness (HK) from the original outer surface (8) of the process element (1 ) being monitored;

the system also comprises at least one condition monitoring unit (4, 4a, 4b) for establishing a connection between it and the wear detector (3); and the wear monitoring unit (4, 4a, 4b) is arranged to determine the change caused by wear in the thickness of the monitored outer surface (8) of the process element (1 ) on the basis of the connection establishment between the wear monitoring unit and wear detector.

1 1 . A system as claimed in claim 10,

c h a r a c t e r i s e d in that

the wear monitoring unit (4) is an electronic terminal that is adapted to establish a connection to the wear detector (3) by means of radio waves; and

the wear monitoring unit (4) is adapted to interpret that the process element (1 ) has worn to the monitored wear thickness (HK) in a situation in which the wear detector (3) does not respond to the connection establishment of the terminal.

12. A process element that is runnable in a paper machine or filter device and comprises opposite outer surfaces (8) and a basic structure between them;

c h a r a c t e r i s e d in that

the process element (1 ) comprises several wear detectors (3) for monitoring change in the thickness caused by wear;

the wear detectors (3) comprise connection means for non- contacting remote reading;

the wear detectors (3) are arranged inside the process element (1 ); and

wear detectors (3) are arranged at least at two different predefined wear thicknesses (HK) from the original outer surface (8) of the process element being monitored. 2101998PC

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13. An arrangement as claimed in claim 12, characterised in that

a malfunction of the wear detector (3) and non-establishment of a remotely readable connection is arranged to indicate that the process element (1) has worn to the extent of the wear thickness (HK) defined by the wear detector (3).

14. A process element as claimed in claim 12 or 13, character- is e d in that

recesses (7) according to wear thicknesses (HK) are formed on the outer surface (8) of the process element being monitored; and

the wear detectors (3) are arranged at the bottom of the recesses

(7) .

15. A process element as claimed in any one of claims 12 to 14, characterised in that

between the wear detector (3) and process element outer surface

(8) , at least one protective layer (9) is arranged that covers the wear detector toward the outer surface of the process element.

16. A process element as claimed in any one of claims 12 to 15, characterised in that

the process element (1) is a textile structure.

17. A process element as claimed in any one of claims 12 to 16, characterised in that

the process element (1) is one of the following: pulp drying machine wire, wet wire, drying wire, press felt, shoe press belt, paper machine transfer belt, band filter belt, disc filter bag, drum filter element, cleaner felt.