SEALING LIP AND METHOD FOR MONITORING THE SEALING LIP

Description

[0001] The invention relates to a sealing lip for a headbox, wherein the sealing lip has a wear volume. The invention further relates to a sealing lip system comprising a sealing lip according to the invention and an evaluation unit for signal processing. The invention also relates to a headbox with a sealing lip according to the invention. The invention also covers a method for monitoring a sealing lip system according to the invention.

[0002] In pulp and paper production, the dewatering of fiber suspensions takes place in the forming area. The headbox allows for the even distribution of the fiber suspension across the width of the headbox, with the fiber suspension being fed into the forming area in a jet. If the jet is designed as a free jet, this can lead to jet expansion, uneven distribution, or even the mixing of air into the jet, which is detrimental to the further process. For this reason, sealing lips are used for headboxes, as they allow jet guidance and prevent air from mixing into the jet.

[0003] US 2004 / 0163788 A1 describes a pulp former with a headbox, where the former is designed as a twin-wire former. The sealing lips of the headbox connect the area between the headbox and the wires of the twin-wire former. Thus, the sealing lips typically extend beyond the tangent point of the forming rolls. Depending on the jet pressure of the suspension guided between the sealing lips, the sealing lips are lightly pressed against the fabrics guided over the forming rolls, creating a sealing contact.

[0004] DE 10 2017 119 325 A1 describes a sealing lip for a headbox made of a fiber composite material and featuring improved performance characteristics. Due to the contact of the sealing lips with the fabrics guided over the forming rolls, the sealing lips are subject to wear and tear and should offer the longest possible service life.

[0005] Sealing lips are located in a sensitive machine area. Failure of the sealing lip—e.g., due to parts breaking off—means that these parts can enter the forming area and cause, for example, damage to the clothing. Failure of the sealing lips therefore poses a threat to machine operation and operational safety. Unplanned downtimes can result. This must be avoided.

[0006] One way to increase operational reliability is to extend the service life of the sealing lip—e.g., by selecting suitable materials—and to ensure trouble-free operation of the sealing lips between the machine's usual service intervals. Replacement is then carried out proactively. If damage to the sealing lip is suspected, a visual inspection of the sealing lip is typically performed, which requires an unplanned machine downtime, as the sealing lip is removed from the machine for inspection.

[0007] The aim of the invention is a sealing lip for a headbox with improved operational reliability.

[0008] This is achieved according to the invention in that at least one indicator is arranged within the sealing lip, at least partially in the area of ​​the wear volume, and the indicator is designed as an electrical or optical conductor. Initially, the indicator is arranged completely within the sealing lip. However, as the sealing lip progresses, the indicator, which is designed as an electrical or optical conductor, is exposed from the sealing lip. With this exposure, however, the electrical or optical properties of the conductor change significantly, allowing the progression of wear to be precisely assessed. The effect of the invention thus lies in the monitoring of the condition of the sealing lip and the continuous assessment of wear.

[0009] An advantageous embodiment of the sealing lip is characterized in that the indicator is arranged normal to a wear direction of the sealing lip and at least in sections in a transverse direction of the sealing lip. The sealing lips establish a connection between the headbox and the former, with the sealing lip typically tangentially contacting the clothing running around the respective forming roll. It follows directly from this that wear occurs in the radial direction with respect to the forming roll, and in a direction normal to the surface of the sealing lip with respect to the sealing lip. Thus, the wear direction of the sealing lip is typically normal to the surface of the sealing lip. Sealing lips are generally in the form of elongated, thin lamellae. They can have a dimension of, for example, 5 m in a transverse direction, a dimension of 500 mm in a longitudinal direction, and a dimension of, for example, one millimeter in the height direction.According to the above definition, wear occurs primarily in the height direction of the sealing lip and thus perpendicular to the longitudinal direction and perpendicular to the transverse direction of the sealing lip. By positioning the indicator perpendicular to the wear direction, the progression of wear can be precisely assessed, as the indicator is positioned in the sealing lip at a defined height. Furthermore, the indicator is positioned at least partially in the transverse direction. Advantageously, the indicator extends across the entire transverse direction of the sealing lip. This allows for reliable detection of severe wear of the sealing lip, even in one area.

[0010] In a further advantageous embodiment, in addition to a first indicator, at least a second indicator is arranged in the sealing lip, and the second indicator is offset from the first indicator in the direction of wear. With the offset arrangement of individual indicators in the direction of wear, i.e. in the direction of the height of the sealing lip, the progress of wear can be evaluated more precisely, since the indicators are arranged in the sealing lip at different levels of defined height. The second indicator is also arranged at least partially in the region of the wear volume and is designed as an electrical or optical conductor. Advantageously, the second indicator is arranged normal to a wear direction of the sealing lip.

[0011] An equally advantageous embodiment of the sealing lip is characterized in that, in addition to a first indicator, at least one further indicator is arranged, wherein the first indicator is arranged in a first section in the transverse direction of the sealing lip and the further indicator is arranged in a second section in the transverse direction of the sealing lip. The section-by-section arrangement of the indicators in the transverse direction of the sealing lip enables the section-by-section evaluation of the wear of the sealing lip. The further indicator is also arranged at least partially in the region of the wear volume and is designed as an electrical or optical conductor. Advantageously, the further indicator is arranged normal to a wear direction of the sealing lip.

[0012] An advantageous embodiment of the sealing lip is characterized in that the indicator is embedded in the sealing lip in an electrically or optically insulating environment. According to the invention, the indicator—or the second indicator or the further indicator—is designed as an electrical or optical conductor. Embedding the indicator—or the second indicator or the further indicator—in the sealing lip in an electrically or optically insulating environment thus encompasses the following configurations.

[0013] In a first embodiment, the indicator is electrically conductive and surrounded by electrical insulation or embedded in it, whereby the thus insulated indicator is embedded in an electrically conductive sealing lip. For example, an indicator designed as a copper strip can be embedded in an electrically conductive sealing lip made of carbon or metal, whereby the indicator is insulated. With progressive wear, the electrical insulation of the indicator is damaged, whereby an electrically conductive connection is created between the sealing lip and the indicator. The change in the electrical properties of the indicator can be recorded directly. In general, a wide variety of electrical properties can be evaluated for this purpose, such as conductivity, resistance, impedance, whereby the electrical properties of the indicator can be measured individually or in relation to a surrounding mass, e.g.the surrounding machine or other indicators can be detected.

[0014] In a second embodiment, the indicator is electrically conductive and embedded in an electrically insulating sealing lip. For example, an indicator formed as a copper strip can be embedded in a sealing lip made of GRP (fiberglass plastic) or plastic, thus providing electrical insulation. As wear progresses, the electrically conductive indicator is exposed from the insulating environment, causing the electrical properties of the indicator to change, which can be detected immediately. The evaluation of the electrical properties is carried out analogously to the first embodiment described above.

[0015] In a third embodiment, the indicator is optically conductive or an optical conductor. Optical conductors are constructed in such a way that light is conducted in a core region, while a surrounding region provides (total) reflection of the light waves. Thus, the region of the optical conductor surrounding the conductive core region already fulfills the requirement of optical insulation. The optical properties of the sealing lip in which the indicator is embedded therefore have no further influence. With progressive wear, the optically conductive indicator is exposed from the sealing lip, and if the optical insulation is compromised, the optical properties of the indicator change, which can be detected immediately. The evaluation of the optical properties includes, for example, transmission, optical attenuation, reflection, etc.In summary, it can be stated that the sealing lip is characterized in that an indicator designed as an electrical conductor is embedded in the sealing lip in an electrically insulating environment or that an indicator designed as an optical conductor is embedded in the sealing lip.

[0016] The aim of the invention is also a sealing lip system with improved operational reliability, wherein the sealing lip system comprises a sealing lip according to the invention and an evaluation unit for signal processing.

[0017] This is achieved according to the invention in that the indicator is optically or electrically connected to the evaluation unit and the indicator can be monitored via the evaluation unit. The electrical or optical properties of the indicator can therefore be monitored via the evaluation unit. With regard to the electrical properties, conductivity, resistance or impedance have already been mentioned, whereby these are monitored in relation to the indicator on its own or in relation to a surrounding mass, e.g. the surrounding machine or other indicators. With regard to the optical properties, transmission, optical attenuation or reflection can be evaluated, for example. With progressive wear, the indicator arranged within the sealing lip becomes exposed.When the indicator is exposed, the monitored properties change significantly, for example because the electrical conductor is exposed from its electrically insulating environment or because the optical conductor is exposed.

[0018] The evaluation unit can be arranged separately from the sealing lip, with the evaluation unit being connected to the indicator, for example, by a cable.

[0019] The evaluation unit can also be mounted directly on the sealing lip and connected to the indicator. The evaluation unit records the indicator's properties and processes them for further transmission. Further transmission by the evaluation unit (e.g., to a plant control system) can be wireless active, wireless passive (via RFID, NFC, or similar), or cable-based.

[0020] The invention also aims to provide a headbox with a sealing lip that allows for particularly reliable operation. This is made possible by a headbox with a sealing lip according to the invention, which eliminates unexpected failure of the sealing lip.

[0021] Furthermore, the invention aims at a method for the safe operation of a sealing lip in a headbox. This is achieved by monitoring the sealing lip system and is characterized in that the optical or electrical properties of the indicator are measured by the evaluation unit. As wear progresses, the conductive indicator arranged within the sealing lip is exposed, with the monitored properties changing significantly with the exposure of the indicator, for example, if the electrical conductor is exposed from its electrically insulating environment or the optical conductor is damaged.

[0022] A particularly advantageous embodiment of the method is characterized in that the evaluation unit measures the optical or electrical properties of a first indicator and at least one further indicator, wherein the change in the optical or electrical properties of the first indicator relative to the further indicator is used as a measure of the wear of the sealing lip. The change in the properties of the first indicator relative to the further indicator allows for improved classification of the wear. If, for example, the first indicator is offset relative to the further indicator in the direction of wear, the wear progression in the direction of wear can be evaluated.For example, if the first indicator is arranged in a first section transverse to the sealing lip and the second indicator is arranged in a further section transverse to the sealing lip, the differential wear in the transverse direction of the sealing lip can be evaluated. In general, the relative evaluation of the electrical or optical properties of the first indicator compared to the second indicator is one way to evaluate the change in the electrical or optical properties.

[0023] An advantageous embodiment of the method is characterized in that the optical properties of the indicator, comprising light conduction, transmission, optical attenuation or reflection, or the electrical properties of the indicator, comprising conductivity, insulation resistance or impedance, are measured by means of the evaluation unit, wherein wear of the sealing lip with material removal on the indicator causes a change in the optical or electrical properties compared to the optical or electrical properties of the undamaged indicator and is used as a measure of the wear of the sealing lip. Wear of the sealing lip with material removal on the indicator means that the indicator is exposed from the sealing lip due to the wear and tear, and the indicator is damaged or material is removed from the indicator. The damage to the indicator influences its optical and electrical conductivity.For example, in a fiber optic cable, the total internal reflection of the light in the area surrounding the core is altered—and thus the light conduction in the core area of ​​the fiber optic cable. Likewise, the electrical conductivity of an electrically conductive indicator changes if it is exposed or damaged due to wear.

[0024] In an advantageous embodiment, a change in the optical or electrical properties of the indicator is measurable as soon as wear on the sealing lip leads to an exposure of the indicator from its electrically or optically insulating environment. The indicator is designed as an electrical or optical conductor and embedded in an insulating environment. Wear causes the indicator to be exposed from the insulating environment. In the case of an electrically conductive indicator, damage to the insulation causes a measurable change in the electrical properties of the indicator. In the case of an optical conductor or light guide, the area surrounding the core area of ​​the light guide can be interpreted as an optically insulating environment, meaning that damage to the optically insulating environment causes a measurable change in the optical properties of the indicator. In summary, a change in the optical orThe electrical properties of the indicator can be measured as soon as wear on the sealing lip leads to damage to the optical conductor or exposure of the electrical indicator from its electrically insulating environment.

[0025] An equally advantageous embodiment of the method is characterized in that wear of the sealing lip with an interruption or destruction of the indicator causes a further distinguishable change in the optical or electrical properties. Surprisingly, it was found that by measuring the optical or electrical properties of the indicator, a clear distinction can be made as to whether the indicator is embedded in the sealing lip without damaging the indicator, whether the indicator has been exposed and damaged, or whether the indicator has been interrupted and thus destroyed by wear. Thus, after an initial indication of damage to the indicator, the sealing lip may well continue to be used until the indicator is completely interrupted. Likewise, the indication of an interruption in the indicator can represent the first indication of damage to the indicator.This may, for example, indicate spontaneous crack formation in the sealing lip, which can be detected by the method according to the invention.

[0026] A further advantageous embodiment of the method is characterized in that the evaluation unit measures the properties of the indicator against a reference. Thus, the optical or electrical properties can be measured relative to the indicator itself, against a surrounding mass (e.g., the surrounding machine), or in relation to other indicators.

[0027] The invention will now be described by way of example with reference to the drawings. Fig. 1 shows a headbox with sealing lips. Fig. 2 shows a sealing lip according to the invention. Fig. 3 shows an example of the progression of a property of the indicator over the wear of the sealing lip.

[0028] Fig. 1 shows a headbox 3 with sealing lips 1, wherein the sealing lips 1 are arranged in the nozzle area of ​​the headbox 3 and establish a connection between the headbox 3 and a former (not shown), e.g. twin-wire former, wherein a fiber suspension is fed to the former via the headbox through the nozzle area between the sealing lips 1. In the case of a twin-wire former, the stock suspension is introduced between two clothings (dewatering wires), wherein the upper and lower clothing are guided around an upper and lower forming roll, respectively. The upper sealing lip 1 touches the clothing guided around the upper forming roll, wherein the upper sealing lip is arranged tangentially to the upper forming roll. Analogously, the lower sealing lip 1 touches the clothing guided around the lower forming roll, wherein the lower sealing lip is arranged tangentially to the lower forming roll.As a result of the contact of the sealing lips with the surrounding coverings, increasing wear occurs on the sealing lips. In . Figur 1 The transverse direction 4 – based on the "cross-machine direction" – is also shown, as is the direction of the height 6 of the sealing lip. Due to the tangential contact of the sealing lips with the coverings, wear occurs primarily in a direction perpendicular to the transverse direction 4 and the longitudinal direction 5. Wear thus occurs primarily in the direction of height 6.

[0029] Fig. 2 shows a sealing lip 1 according to the invention with an indicator 2. Sealing lips 1 typically have the shape of elongated, thin slats. They can have a dimension of, for example, 5 m in a transverse direction 4 (based on a "cross-machine direction"), a dimension of 500 mm in a longitudinal direction 5 (based on a "longitudinal machine direction"), and a dimension of, for example, one millimeter in the height direction 6. Fig. 2 The sealing lip 1 is interrupted several times in order to fully represent the very elongated sealing lip 1. The interruptions are shown as lines with short divisions, whereby in Fig. 2 the sealing lip is shown interrupted once in the longitudinal direction 5 and interrupted four times in the transverse direction 4.

[0030] Advantageously, the indicator 2 is arranged in an area in the longitudinal direction 5 of the sealing lip 1 in which increased wear is to be expected, for example in an area in the longitudinal direction 5 of the sealing lip 1 in which the sealing lip 1 is in contact with the covering of the former. In an advantageous embodiment of the sealing lip 1, the indicator 2 is parallel to the transverse direction 4 and viewed from the fastening end of the sealing lip 1 (in Fig. 2 in the upper region of the sealing lip) in the longitudinal direction 5 of the sealing lip 1 in the region between the first quarter and the second quarter of the sealing lip 1. The indicator 2 is designed according to the invention as an electrical or optical conductor. In an advantageous embodiment, the indicator 2 is embedded in the sealing lip 1 in an electrically or optically insulating environment. Various configurations of the sealing lip 1 are conceivable. In a first configuration, the indicator is electrically conductive and surrounded by electrical insulation, wherein the insulated indicator is embedded in an electrically conductive sealing lip. For example, an indicator designed as a copper strip can be embedded in an electrically conductive sealing lip made of carbon or metal, wherein the indicator is insulated.

[0031] In a second embodiment, the indicator is electrically conductive and embedded in an electrically insulating sealing lip. For example, an indicator formed as a copper strip can be embedded in a sealing lip made of GRP (fiberglass plastic) or plastic, thus providing electrical insulation.

[0032] In a third embodiment, the indicator is optically conductive or an optical conductor. The optical properties of the sealing lip into which the indicator is embedded have no further influence.

[0033] Fig. 3 shows an example of the progression of a property of the indicator over the wear of the sealing lip. The sealing lip system allows monitoring of the wear of the sealing lip by recording the optical or electrical properties of the indicator 2 via the evaluation unit. It was determined that by measuring the optical or electrical properties of the indicator 2, different wear states of the sealing lip 1 can be distinguished. Fig.3 The abscissa shows an increasing wear condition of the sealing lip 1 from left to right, and the ordinate shows an optical or electrical property of the indicator. In particular, it can be distinguished whether the indicator 2 is embedded in the sealing lip without damaging the indicator (see Fig.3 Reference number 7), whether there is exposure of the indicator with injury to the indicator (see Fig.3 Reference number 8) or whether the indicator is interrupted by wear (see Fig.3 Reference number 9) and was thus destroyed. For example, using the example of an electrically conductive indicator (2) embedded in the sealing lip in an electrically insulating environment, the electrical conductor has an electrical resistance (see Fig.3 Reference number 7). By exposing the indicator 2, whereby the insulation of the indicator 2 has been interrupted and a conductive connection to the environment is established, the resistance of the conductor decreases significantly (see Fig.3 Reference number 8). However, with further wear and interruption of indicator 2 and thus with interruption of the conductive connection, a significantly higher resistance is established (see Fig.3Reference number 9). With respect to an indicator designed as an electrical conductor, a wide variety of properties of the indicator can be recorded and evaluated, such as conductivity, resistance, impedance, whereby the electrical properties of the indicator are recorded individually or in relation to a surrounding mass, e.g., the surrounding machine or other indicators. When using an indicator designed as an optical conductor, a wide variety of optical properties of the indicator can be recorded and evaluated in a similar manner, such as transmission, optical attenuation, reflection, etc.

[0034] The present invention offers numerous advantages, in particular, safe operation of headboxes with sealing lips is possible because unforeseen failure of the sealing lip can be ruled out. The properties according to the invention thus have the effect of enabling continuous monitoring of the wear of the sealing lip without requiring the sealing lip to be removed from the machine. In addition to the possibility of detecting when a certain wear limit is reached - namely when the indicator is exposed or damaged - the invention also allows spontaneous failure of the sealing lip to be detected, e.g., when a crack forms. In the latter case, the indicator has been interrupted by a crack, for example, and thus destroyed, and the damage is recorded immediately. Reference symbol

[0035] (1)Sealing lip (2)Indicator (3)Headbox (4)Transverse direction (5)Longitudinal direction (6)Direction of height (7)Signal when the indicator is fully embedded (8)Signal when the indicator is exposed / damaged (9)Signal when the indicator is interrupted

Claims

1. Sealing lip (1) for a headbox (3), the sealing lip (1) having a wear volume, characterised in that at least one indicator (2) is arranged inside the sealing lip (1) at least partially in the region of the wear volume and the indicator (2) is designed as an electrical or optical conductor.

2. Sealing lip (1) according to claim 1, characterised in that the indicator (2) is arranged normal to a direction of wear of the sealing lip (1) and at least in sections in a transverse direction (4) of the sealing lip (1).

3. Sealing lip (1) according to claim 2, characterised in that at least one second indicator (2) is arranged next to the indicator (2) and the second indicator (2) is offset from the indicator (2) in the direction of wear.

4. Sealing lip (1) according to one of claims 1 to 3, characterized in that at least one further indicator (2) is arranged next to the indicator (2), the indicator (2) being arranged in a first section in the transverse direction (4) of the sealing lip (1) and the further indicator (2) being arranged in a second section in the transverse direction (4) of the sealing lip (1).

5. Sealing lip (1) according to any one of claims 1 to 4, characterised in that the indicator (2) is embedded in the sealing lip (1) in an electrically or optically insulating environment.

6. Sealing lip system comprising a sealing lip (1) according to one of claims 1 to 5 and an evaluation unit for signal processing, characterised in that the indicator (2) is optically or electrically connected to the evaluation unit and the indicator (2) can be monitored via the evaluation unit.

7. Headbox (3) with a sealing lip (1) according to one of claims 1 to 5.

8. Method for monitoring the sealing lip system according to claim 6, characterised in that the optical or electrical properties of the indicator (2) are measured by means of the evaluation unit.

9. Method according to claim 8, characterized in that the optical or electrical properties of a first indicator (2) and at least one further indicator (2) are measured by means of the evaluation unit, the change in the optical or electrical properties of the first indicator (2) with respect to the further indicator (2) being used as a measure of the wear of the sealing lip (1).

10. Method according to claim 8, characterised in that the optical properties of the indicator (2), comprising optical fibre, transmission, optical attenuation or reflection, or the electrical properties of the indicator (2), comprising the conductivity, the insulation resistance or the impedance, are measured by means of the evaluation unit, wherein wear of the sealing lip (1) with material removal on the indicator (2) causes a change in the optical or electrical properties compared with the optical or electrical properties of the undamaged indicator (2) and is used as a measure of the wear of the sealing lip (1).

11. Method according to claim 8, characterised in that a change in the optical or electrical properties of the indicator (2) can be measured as soon as the wear on the sealing lip (1) leads to the indicator (2) being exposed from its electrically or optically insulating environment.

12. Method according to claim 11, characterised in that wear of the sealing lip (1) with an interruption or destruction of the indicator (2) causes a further distinguishable change in the optical or electrical properties.

13. Method according to claim 10, characterised in that the properties of the indicator (2) are measured against a reference by means of the evaluation unit.