Plate heat exchanger comprising pressure sensors, method, and system for monitoring the condition of gaskets in a plate heat exchanger

Abstract

The invention relates to a plate heat exchanger in which a plurality of heat exchanger plates are held together in a pressure frame between a frame head provided with media connections and an end cover by means of a clamping device to form a plate stack. A flow space is formed between each pair of adjacent plates by means of a peripheral gasket. The flow spaces are alternately connected in a fluid-conducting manner to two different pairs of media connections, such that adjacent flow spaces can be traversed by different heat-exchange media. In order to enable monitoring of the condition of the gaskets, at least one pressure sensor is arranged on the frame head along a contour line of the peripheral gaskets, the pressure sensor measuring the surface pressure acting on the peripheral gaskets in the plate stack.

Description

[0001] title

[0002] Plate heat exchangers with pressure sensors, method and system for monitoring the condition of seals in a plate heat exchanger

[0003] Description

[0004] The present invention relates to a plate heat exchanger with a plurality of heat exchanger plates which are held together in a frame between a frame head with media connections and a cover by means of a clamping device to form a plate stack. In particular, the invention relates to a plate heat exchanger which is equipped with pressure sensors to monitor the seals in the plate stack.

[0005] Plate heat exchangers, used for transferring heat between different media, are known from the prior art. A typical problem with these heat exchangers is the regular replacement of the gaskets, which are responsible for sealing the flow spaces between the plates. In conventional systems, the condition of the gaskets is often difficult to assess, which can lead to unexpected leaks.

[0006] The construction of a plate heat exchanger is described, for example, in the document EP 08 48 225 A2.

[0007] WO 2005 / 119 197 Al describes a system that uses pressure sensors to monitor the pressure between the plate and the seal, as well as the pressure of the incoming fluid. These values ​​are used to calculate a

[0008] 34870-P-WO Ur / ef uses differential pressure to predict potential leaks. For this purpose, a sensor is provided on each plate, positioned between the gasket and the plate, so that it makes contact with both the gasket and the plate. This is very complex and prone to errors. Another disadvantage of this solution is that it cannot reflect the actual condition of the gaskets in the plate stack.

[0009] One objective of the invention is to develop a solution that enables more precise monitoring of the condition of the seals in order to improve the operational reliability and maintenance efficiency of plate heat exchangers.

[0010] The problem is solved with respect to a plate heat exchanger by the features of claim 1. A method according to the invention and a system for monitoring the condition of seals in a plate heat exchanger are specified in claims 8 and 12. Advantageous embodiments are described in the dependent claims.

[0011] In a plate heat exchanger with a plurality of heat exchanger plates held together in a frame between a frame head provided with media connections and a cover by a clamping device to form a plate stack, wherein a flow space enclosed by a circumferential seal is formed in each space between two adjacent plates and the successive flow spaces in the plate stack are alternately connected to two different pairs of media connections in a fluid-conducting manner, so that each adjacent flow space can be traversed by different heat exchange media, at least one pressure sensor is provided according to the invention, which is arranged on the frame head along a contour line of the circumferential seals in such a way that it measures the surface pressure acting on the circumferential seals in the plate stack.This allows for precise and continuous monitoring of the sealing load, which increases operational reliability.

[0012] 34870-P-WO Ur / ef The invention is not limited to having all media connections arranged on the frame head. Rather, the invention also includes multi-pass plate heat exchangers in which some of the media connections – generally at least one connection for one of the heat exchange media – can be located on the cover.

[0013] Preferably, several pressure sensors are arranged on the frame head of the plate heat exchanger along the contour line. This improves the accuracy of the pressure measurement across the entire sealing line.

[0014] According to a preferred embodiment of the invention, the plate heat exchanger has heat exchanger plates with openings for two heat exchange media, and each of the flow chambers is connected to one of the pairs of media connections via at least two openings in one adjacent plate and at least two openings aligned therewith in the opposite, other adjacent plate, while the adjacent flow chamber is connected to the other pair of media connections via at least two further openings in said one plate and at least two openings aligned therewith in said other plate, through passageways past the first-mentioned flow chamber. Circumferential seals for sealing the flow chambers of each heat exchange medium and ring seals for sealing the passageways of the other heat exchange medium are provided in the spaces between the plates.This enables efficient media routing and sealing.

[0015] Pressure sensors can be provided for both the circumferential seals and the ring seals. Preferably, in the plate heat exchanger, at least one of the pressure sensors is arranged in a bridge area where the contour line of the circumferential seals runs obliquely between two openings. This increases the monitoring accuracy in critical areas.

[0016] 34870-P-WO Ur / ef The pressure sensors can advantageously be designed as piezoresistive film sensors. This ensures high sensitivity and reliability of the pressure measurement.

[0017] In particular, the at least one pressure sensor may consist of two sensor films, each equipped with at least one electrode, between which a layer of a pressure-sensitive material is applied that changes its electrical resistance depending on an applied pressure force. This enables precise detection of pressure changes.

[0018] The clamping device can advantageously include a number of circumferentially distributed clamping screws. This ensures an even distribution of pressure on the stack of plates. Alternatively, the clamping frame can be designed as a so-called central locking frame with at least one rear pressure spindle, which presses the cover against the stack of plates from behind.

[0019] In addition to gasketed plate heat exchangers, the invention can also be used with semi-welded plate heat exchangers. In this case, at least some of the heat exchanger plates are bonded together in pairs to form cassettes, in particular by welding. Naturally, no gasket is required or provided between the welded plates. Circumferential gaskets and ring gaskets in the area of ​​the openings for the heat exchange medium flowing to the next space are present only between the cassettes adjacent to each other in the plate stack. The surface pressure monitoring according to the invention can also be advantageously used for these cassettes. In this case, it can be particularly advantageous to also provide a pressure sensor in the area of ​​the ring gaskets.

[0020] The inventive method for monitoring the condition of seals in a plate heat exchanger with a plurality of seals in a frame between a

[0021] 34870-P-WO Ur / ef, a frame head equipped with media connections and a cover, clamped together by a clamping device to form a stack of heat exchanger plates, in particular a plate heat exchanger of the type described above, comprises the following steps: placing at least one pressure sensor on the frame head along a contour line of the seals in the plate stack of the heat exchanger; repeatedly measuring a surface pressure acting on the seals by the at least one pressure sensor; acquiring and storing the pressure measurement data over a defined period; analyzing the acquired pressure measurement data to identify trends and / or deviations in the pressure profile, and determining the condition of the seals based on the identified deviations or pressure trends in order to detect potential seal failure at an early stage. This enables proactive maintenance and extends the service life of the seals.

[0022] The surface pressure measurement using at least one pressure sensor can be performed continuously or discontinuously at regular intervals or event-driven, for example, when a certain typical fluid pressure is reached during operation or during operational breaks when no additional fluid pressure exists in the heat exchanger. The measurements are carried out and recorded over an extended period, corresponding to the typical service life of the seals, in order to continuously monitor and assess the seal's behavior and condition. This period can range from months to several years.

[0023] According to a preferred embodiment of the invention, the method additionally includes the step of measuring the distance between the frame head and the cover of the plate heat exchanger in order to determine the degree of compression of the seals. This helps to assess the maintenance requirements.

[0024] 34870-P-WO Ur / ef The distance can preferably be determined using a non-contact measuring device, in particular by means of laser distance measurement. This ensures precise and fast distance measurement.

[0025] As part of this process, an analysis of the spacing data can be performed to determine whether the plate stack can be retensioned or whether the seals need to be replaced. This optimizes the maintenance process.

[0026] A system according to the invention for monitoring the condition of seals in a plate heat exchanger with a plurality of heat exchanger plates held together in a frame between a frame head provided with media connections and a cover by means of a clamping device to form a plate stack comprises at least one pressure sensor positioned on the frame head along a contour line of the seals in the plate stack to measure the surface pressure on the seals, a data acquisition unit connected to the at least one pressure sensor to repeatedly acquire and store pressure measurement data, a data processing unit programmed to analyze the stored pressure measurement data and to identify pressure trends and / or deviations in the pressure profile, and a display or alarm unit that provides information about the condition of the seals based on the analyzed deviations or pressure trends.to provide early warning of a potential seal failure. This improves operational reliability and maintenance efficiency.

[0027] The data acquisition unit and the data processing unit can, in principle, be implemented as physically and / or logically separate units, or they can be realized through corresponding program components on a common processor-controlled computing unit.

[0028] 34870-P-WO Ur / ef According to a further development of the invention, a system also comprises a distance measuring system, in particular a laser distance measuring system, which is configured to measure the distance between the frame head and the cover of the plate heat exchanger. This enables monitoring of the compression level of the seals.

[0029] The data processing unit can be configured to decide, based on the distance measurements, whether the stack of plates can be retensioned using the clamping device or whether the seals need to be replaced.

[0030] This optimizes maintenance requirements and extends the service life of the seals.

[0031] The invention can be better understood with reference to the following drawings and description. The components in the illustrations are not necessarily to scale; rather, the focus is on illustrating various preferred embodiments of the invention. It shows:

[0032] Figure 1 is a perspective exploded view of a plate heat exchanger,

[0033] Figure 2 shows an isometric view of the frame of the plate heat exchanger with pressure sensors arranged on the frame head and

[0034] Figure 3 shows a block diagram of a system according to the invention for monitoring the condition of seals in a plate heat exchanger.

[0035] Figure 1 shows a plate heat exchanger (also commonly referred to as a plate heat exchanger) with a plurality of plates 2, 3, 4, 6, 7 with a rectangular outer shape, which are joined together in a pressure frame in a flush arrangement to form a stack of plates 5.

[0036] The pressure frame comprises a frame head 1, which is equipped with connections 13a, 13b, 14a, 14b for the heat exchanger media, to which the fluid lines are connected.

[0037] 34870-P-WO Ur / ef. Support rods 9 and 11 at the top and bottom, which are attached to the frame head 1 and a support 10, serve to stabilize the printing frame. A movable cover 8 forms the end, with which the stack of plates 5 is held together under tension against the frame head 1 by means of clamping screws 12.

[0038] The pressure frame within the scope of the invention can be either a skeletonized frame, as shown in Figures 1 and 2, or a closed housing in which the plates are held together under preload to form a plate stack 5. The cover 8 does not necessarily have to completely cover the plates 2, 3, 4, 6, 7 on the back, but merely forms an abutment for a clamping device of any design, with which the plates are held together against the frame head 1, and can therefore also be of a skeletonized design.

[0039] The plate stack 5 comprises a starting plate 2, a number of mirror-image left and right heat exchanger plates 3, 4, and one left and one right switching plate 6, 7, which reverse the flow paths for the heat exchanger media in the outlet direction. Instead of switching plates, deflection plates can generally be provided, particularly in multi-pass plate heat exchangers, which direct the fluid flow towards a media connection provided on the cover instead of towards the frame head.

[0040] Between plates 2, 3, 4, 6, 7, a circumferential seal 17a, 17b and two ring seals 18 are arranged, which, for manufacturing and maintenance reasons, can be connected to the circumferential seals 17a, 17b via webs as shown here. The seals 17a, 17b, 18 are designed to be fitted into specially shaped grooves on plates 1, 2, 3, 4, 6, 7 or to be glued directly onto plates 1, 2, 3, 4, 6, 7.

[0041] 34870-P-WO Ur / ef The seals are typically made of elastic material such as rubber or special plastics that are resistant to the fluids used in the heat exchanger. In the exemplary embodiment, the seals are made of EPDM (ethylene propylene diene monomer rubber).

[0042] Each of the heat exchanger plates 3, 4 and the initial plate 2 has four openings 15a, 15b, 16a, 16b, which are each arranged in the corner sections, wherein the left openings 15a, 15b of the plates 2, 3, 4 shown in Figure 1 are supplied via the connections 13a, 13b by a first heat exchange medium A and the two right openings 16a, 16b via the connections 14a, 14b by a second heat exchange medium B.

[0043] Flow spaces are formed between plates 2, 3, and 4, sealed by circumferential seals 17a and 17b, and each of these spaces can be used by one of the heat exchanger media. The ring seals 18 each seal a pair of openings against the respective flow space. Each plate is designed with a corrugated profile to generate turbulent flow and maximize heat transfer.

[0044] The arrangement of plates 3 and 4 and the insertion of the circumferential seals 17a and 17b as well as the ring seals 18 are carried out alternately, so that adjacent flow chambers are supplied with different heat exchanger media. Figure 1 indicates the corresponding flow paths of both media with black and white arrows, respectively.

[0045] At the start plate, all four openings 15a, 15b, 16a, 16b are sealed against the frame head 1 to prevent the heat exchanger fluids from escaping between the plate pack 5 and the frame head 1. The circumferential seal between the start plate 2 and the frame head 1, however, does not serve a sealing function but merely ensures uniform contact and distribution of the surface pressure.

[0046] 34870-P-WO Ur / ef The first switching plate 6 has only openings 16a, 16b on the right, while the medium A is returned towards the connection 13b on the frame head 1. The second switching plate 7 has no openings on the right and accordingly returns the medium B towards the connection 14b on the frame head 1. The openings formed in the second switching plate 7 have no function but are present solely for manufacturing reasons, in order to be able to use the same plate shape, rotated by 180°, as both the first and second switching plates 6, 7.

[0047] Clamping screws 12 are evenly distributed around the stack of plates 5 to hold the plates together under uniform preload and to ensure a reliable seal for the gaskets 17a, 17b, 18. Of course, any other clamping device suitable for holding the plates together under preload can be used instead of clamping screws 12. For example, as explained earlier, the pressure frame can be designed as a central locking frame with a rear pressure spindle that presses the cover against the stack of plates.

[0048] Figure 2 shows a similar pressure frame for a plate heat exchanger with frame head 1, support rods 9 and 11, a support 10, and the movable cover 8 held against the frame head by clamping screws 12, from a different perspective. For clarity, the plates 2, 3, 4, 6, 7 of the plate heat exchanger have been omitted. Instead, only an example of a circumferential seal 17a is shown. In reality, the stack of plates 5, which is not shown here, naturally contains a multitude of seals 17a, 17b that alternately open the left and right openings.

[0049] A dotted contour line 19 is drawn on the inner surface of the frame head 1, corresponding to the course of the circumferential seal 17a. This is an imaginary line that corresponds to a projection of the center line of the circumferential seal 17a. According to the invention, pressure sensors 20, 21 are located along this line 19.

[0050] 34870-P-WO Ur / ef. Figure 2 shows two pressure sensors 20, 21 as examples. Of course, further pressure sensors may be present and arranged along contour line 19. The bridge areas between the connection openings 13b and 14a or 13a and 14b are particularly susceptible to leaks at the seals 17a, 17b, where the seals run below and diagonally between the openings 15b and 16a or 15a and 16b. The pressure sensor 21 is therefore arranged in this area.

[0051] The pressure sensors 20, 21 are positioned to enable the measurement and monitoring of the surface pressure acting on the circumferential seals 17a, 17b within the plate stack 5, without requiring the pressure sensors 20, 21 to be in direct contact with the circumferential seals 17a, 17b within the plate stack 5. Direct contact between the pressure sensors and the circumferential seals 17a, 17b within the plate stack 5 would be disadvantageous, as it would be complex to manufacture and prone to failure, which in turn could lead to sealing problems.

[0052] Preferably, piezoresistive film sensors can be used as pressure sensors 20, 21. These consist of two films on which electrodes are applied. Between the films is a pressure-sensitive material which changes its electrical resistance under mechanical stress. This change in resistance between the electrodes or at the points where the electrodes cross is measured and serves as a measure of the surface pressure. Alternative pressure sensors, such as capacitive sensors, can also be used within the scope of the invention.

[0053] A laser distance measuring device 22 is also attached laterally to the frame head 1 in Figure 2. This measures the distance to a target 23 arranged on the movable cover 8. This allows the thickness of the plate stack 5, including the seals 17a, 17b located between the individual plates 2, 3, 4, 6, 7, to be measured. If the plate thickness is known, the degree of compression of the seals 17a, 17b can be determined, thus enabling an estimation of whether the seals 17a, 17b are sufficient.

[0054] 34870-P-WO Ur / ef whether the clamping screws 12 can be further compressed by tightening them to increase the surface pressure, or whether they should be replaced. Of course, the arrangement of the laser distance measuring device 22 is purely exemplary; a measurement from one side would also be possible, from which the thickness of the stack of plates could be determined by triangulation. Other distance measurement methods besides laser distance measurement can also be used within the scope of the invention.

[0055] Within the scope of the invention, the surface pressure can be continuously monitored by the pressure sensors 20, 21, enabling early detection of sealing problems. By analyzing the measured pressure data, changes in the condition of the seals can be identified and appropriate maintenance measures can be taken before leaks occur. This not only improves operational reliability but also optimizes maintenance intervals and extends the service life of the heat exchanger.

[0056] The pressure sensors 20, 21 in the plate heat exchanger are integrated into a monitoring system, shown by way of example in Figure 3, which enables continuous acquisition and processing of the pressure data. Several sensors 20 are shown by way of example, which can be arranged along the contour line 19. Each sensor 20, 21 is connected via a fieldbus to a central processing unit 24, which collects the measurement data supplied by the sensors 20, 21 in real time. The processing unit 24 is equipped with a microcontroller pP, which queries the sensor values ​​at regular intervals and stores them in RAM. An I / O component manages the external connections.

[0057] For the acquisition and processing of the print data, the computing unit 24 is equipped with various program components 25, 26. A data acquisition component 25 acquires and stores the sensor data. A data processing component 26 evaluates the data stored over longer periods in order to identify long-term trends and changes. The algorithm of the data processing component 26

[0058] 34870-P-WO Ur / ef analyzes the stored data for deviations from the normal pressure profile. Historical data is also included to determine whether there is a gradual deterioration of the seals. Among other things, a moving average can be calculated, which averages the data over a predefined period. This averaging helps to smooth out temporary fluctuations caused by external influences, thermal variations, or fluid pressure fluctuations. AI-based data analysis of the pressure data is also possible within the scope of the present invention and can increase the reliability of early detection of aging and material fatigue in the seals 17a, 17b.

[0059] Long-term analysis of pressure data allows conclusions to be drawn about the condition of the seals. A gradual decrease in surface pressure, for example, could indicate hardening or deterioration of the seals. In such a case, the system can automatically trigger maintenance alarms indicating that the seals need to be replaced. These messages can be displayed via a user interface. The user interface typically includes input devices such as a keyboard 28 and output devices such as a monitor 27. For transmitting alarms and warnings, as well as for remote monitoring and control, the processing unit 24 may also have a LAN or WAN interface.

[0060] The computing unit 24 can additionally be connected to the laser distance measuring device 22 and other measuring devices such as a manometer 29, which in this case measures the fluid pressure in the heat exchanger, which also affects the surface pressure on the seals 17a, 17b. Thus, based on the distance measurement data, the computing unit can determine the degree of compression of the seals 17a, 17b and, if necessary, recommend retightening the clamping screws 12 to increase the surface pressure if it has fallen below a minimum value for leak-free operation in the long term.

[0061] 34870-P-WO Ur / ef Additionally, the analysis also enables the optimization of maintenance intervals by providing accurate predictions of when maintenance will be required. This reduces operating costs and increases the efficiency of the heat exchanger, as unplanned downtime is avoided.

[0062] Overall, the system offers a precise and predictive maintenance strategy based on the continuous monitoring and analysis of surface pressure.

[0063] 34870-P-WO Ur / ef

Claims

Claims 1. Plate heat exchanger with a plurality of heat exchanger plates (3, 4) held together in a pressure frame between a frame head (1) provided with media connections and a cover (8) by a clamping device to form a plate stack (5), wherein a flow space enclosed by a circumferential seal (17a, 17b) is formed in each space between two adjacent plates and the successive flow spaces in the plate stack (5) are alternately connected to two different pairs of media connections in a fluid-conducting manner, so that each adjacent flow space can be supplied with different heat exchange media, characterized by at least one pressure sensor (20, 21) which is arranged on the frame head (1) along a contour line of the circumferential seals (19) in such a way that it measures a surface pressure acting on the circumferential seals (17a, 17b) in the plate stack (5).

2. Plate heat exchanger according to claim 1, in which several pressure sensors (20, 21) are arranged on the frame head (1) along the extent of the contour line (19).

3. Plate heat exchanger according to claim 1 or 2, wherein the heat exchanger plates (3, 4) have openings (15a, 15b, 16a, 16b) for two heat exchange media and each of the flow spaces has at least two openings (15a, 15b) in one adjacent plate (3) and at least two openings (15a, 15b) aligned therewith in the opposite, other plate (3). 34870-P-WO Ur / ef the adjacent plate (4) is connected to one of the pairs of media connections (13a, 13b), while the adjacent flow space is connected to the other pair of media connections (14a, 14b) via at least two further openings (16a, 16b) in the aforementioned one plate (3) and at least two openings (16a, 16b) aligned therewith in the aforementioned other plate (4) via passage channels past the first-mentioned flow space, wherein the circumferential seals (17a, 17b) for sealing the flow spaces of one heat exchange medium and ring seals (18) for sealing the passage channels of the other heat exchange medium are provided in the spaces between the plates.

4. Plate heat exchanger according to claim 3, in which at least one of the pressure sensors (20, 21) is arranged in a bridge area in which the contour line of the circumferential seals (19) runs obliquely between two openings (15b, 16a).

5. Plate heat exchanger according to one of the preceding claims, wherein the at least one pressure sensor (20, 21) is designed as a piezoresistive foil sensor.

6. Plate heat exchanger according to one of the preceding claims, wherein the at least one pressure sensor (20, 21) comprises two sensor films, each provided with at least one electrode, between which a layer of a pressure-sensitive material is applied which changes its electrical resistance depending on an applied pressure force.

7. Plate heat exchanger according to one of the preceding claims, wherein the clamping device comprises a plurality of circumferentially distributed clamping screws (12) or a rear pressure spindle. 34870-P-WO Ur / ef 8. Plate heat exchanger according to one of the preceding claims, in which at least a part of the heat exchanger plates (3, 4) are joined in pairs to form cassettes by material bonding, in particular by welding, and the circumferential seal (17a, 17b) is arranged between the cassettes adjacent to each other in the plate stack (5).

9. Method for monitoring the condition of seals (17a, 17b) in a plate heat exchanger with a plurality of heat exchanger plates (3, 4) held together in a pressure frame between a frame head (1) provided with media connections and a cover (8) via a clamping device to form a plate stack (5), in particular a plate heat exchanger according to one of the preceding claims, comprising the steps: - Placing at least one pressure sensor (20, 21) on the frame head (1) along a contour line (19) of the seals (17a, 17b) in the plate stack (5) of the heat exchanger; - repeated measurement of a surface pressure acting on the seals (17a, 17b) by means of at least one pressure sensor (20, 21); - Recording and storing pressure measurement data over a defined period; - Analyzing the recorded pressure measurement data to identify trends and / or deviations in the pressure curve, and - Determining the condition of the seals (17a, 17b) based on the identified deviations or pressure trends in order to detect a potential seal failure early.

10. Method according to claim 9, comprising the step of measuring the distance between the frame head (1) and the cover (8) of the plate heat exchanger in order to determine a degree of compression of the seals (17a, 17b). 34870-P-WO Ur / ef 11. Method according to claim 10, wherein the distance is determined by means of a non-contact measuring device, in particular by means of a laser distance measurement (22).

12. Method according to claim 11, comprising the analysis of the distance data to determine whether the plate stack (5) can be retensioned or whether a replacement of the seals (17a, 17b) is required.

13. System for monitoring the condition of seals (17a, 17b) in a plate heat exchanger with a plurality of heat exchanger plates (3, 4) held together in a pressure frame between a frame head (1) provided with media connections and a cover (8) via a clamping device to form a plate stack (5), in particular a plate heat exchanger according to one of claims 1 to 8, comprising: - at least one pressure sensor (20, 21) positioned on the frame head (1) along a contour line (19) of the seals (17a, 17b) in the plate stack (5) to measure the surface pressure on the seals (17a, 17b), - a data acquisition unit (25) connected to the at least one pressure sensor (20, 21) to repeatedly acquire and store pressure measurement data, - a data processing unit (26) which is programmed to analyze the stored pressure measurement data and to identify pressure trends and / or deviations in the pressure history, and - a display or alarm unit (27) that provides information about the condition of the seals (17a, 17b) based on the analyzed deviations or pressure trends in order to provide early warning of a potential seal failure. 34870-P-WO Ur / ef 14. System according to claim 13, characterized in that it comprises a distance measuring system, in particular a laser distance measuring system (22), which is configured to measure the distance between the frame head (1) and the cover (8) of the plate heat exchanger.

15. System according to claim 14, wherein the data processing unit (26) is configured to decide, based on the distance measurements, whether the stack of plates (5) can be retensioned using the clamping device or whether the seals (17a, 17b) need to be replaced. 34870-P-WO Ur / ef

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