Mechanical seal assembly with torque meter and method thereof

Abstract

The present invention relates to a mechanical seal assembly. The mechanical seal assembly includes a mechanical seal (2) having a rotating slide ring (3) and a fixed slide ring (4) that define a seal gap (5) between their sliding surfaces (3a, 4a), and a torque meter (6) configured to detect a torque acting on the fixed slide ring (4). The torque meter (6) includes a measurement unit (7) and a sensor (9). The measurement unit (7) is fixed to a housing (8) by a foot (72) and has a free end (71) that protrudes into a groove (40) formed in the outer periphery of the fixed slide ring (4). The sensor (9) is configured to detect a change in position of the measurement unit (7) in the groove (40).

Description

[Technical Field]

[0001] The present invention relates to a mechanical seal assembly equipped with a torque meter and a method for inspecting the wear of the sliding surfaces of the mechanical seal assembly. [Background technology]

[0002] Various designs of mechanical seal assemblies are known in the prior art. A problem area for mechanical seal assemblies is determining the wear condition of the sliding surfaces of the slide rings. During normal operation, mechanical seals are typically contactless seals, in which a gas or fluid cushion is provided between the sliding surfaces of the stationary and rotating slide rings. However, even during operation, situations occur in which the slide rings come into contact with each other during machine startup, disconnection, or between machine startup and the lifting of the sliding surfaces. Pressure surges acting in the axial direction of the mechanical seal can also occur during operation, establishing contact between the sliding surfaces. However, such contact can damage the sliding surfaces and require the slide rings to be replaced. For example, it is known that wear of the sliding surfaces can be determined based on leakage across the seal gap. However, other alternatives for determining the condition of the sliding surfaces would be desirable. Summary of the Invention [Problem to be solved by the invention]

[0003] Therefore, an object of the present invention is to provide a mechanical seal assembly and a method for inspecting the wear state of a sliding surface that are simply designed, easy to manufacture, cost-effective, and capable of quickly and reliably determining the wear state of the sliding surface. [Means for solving the problem]

[0004] This object is achieved by a mechanical seal assembly having the features of claim 1 and by a method having the features of claim 13. The dependent claims in each case indicate preferred developments of the invention.

[0005] The mechanical seal assembly according to the present invention, having the features of claim 1, offers the advantage of enabling a different, more easily implemented wear detection method for the sliding surfaces of the rotating and / or stationary slide rings of a mechanical seal. In particular, direct torque measurement of the torque acting on the stationary slide ring is possible, both in a test mode on a test stand and when the mechanical seal is installed to seal against a shaft or the like. This is achieved according to the present invention in that the mechanical seal assembly comprises a mechanical seal having a rotating and a stationary slide ring that define a seal gap between their sliding surfaces. Furthermore, a torque meter configured to detect torque acting on the stationary slide ring is provided. In this case, the torque meter comprises a measuring unit and a sensor. The measuring unit is fixed to the housing of the mechanical seal by a foot and is disposed by its free end in a groove formed in the outer periphery of the stationary slide ring. The sensor is configured to detect a change in position of the measuring unit within the groove. In this case, the change in position of the measuring unit is a measure of the torque acting on the stationary slide ring. In this case, the detected torque value on the fixed slide ring indicates the state of wear on the sliding surfaces of the rotating and fixed slide rings, allowing for simple and reliable detection of the condition of the sliding surfaces and enabling prompt replacement of the slide rings if necessary.

[0006] In particular, the torque meter according to the invention allows reliable torque measurement even in the event of axial movements of the fixed slide ring which may occur due to pressure surges during operation, for example.

[0007] In this way, reliable torque detection is possible even in the case of a fixed slide ring that is movable in the axial direction.

[0008] The measuring unit is preferably configured as a flat rod. Such a measuring unit comprises a flat, bar-like rod fixed at one end and having a length greater than its cross-sectional dimension. The cross section of the flat rod is preferably rectangular. The free end of the flat rod is placed in a groove in the fixed slide ring, and the foot of the flat rod is fixed stationary in the housing. Therefore, when torque is transmitted to the fixed slide ring, the fixed slide ring moves in the circumferential direction, and the free end of the flat rod comes into contact with the groove wall and undergoes a position change. The position change is a measure of the torque transmitted to the fixed slide ring, and based on this, the wear of the sliding surface of the slide ring can be determined.

[0009] Preferably, in each case, a protruding area, in particular a cam-shaped area, is formed on each flat side of the free end of the flat rod. In this case, the width of the flat rod in the groove is preferably minimally smaller than the width of the groove, so that when a torque is transmitted to the fixed slide ring, the position change of the free end of the flat rod occurs immediately. As a result, even small torques can be reliably detected.

[0010] More preferably, the foot of the measuring unit has a thickness greater than that of the free end, and preferably the thickness of the foot of the measuring unit is twice the thickness of the free end.

[0011] The torque meter sensor is particularly preferably an optical sensor. In this case, the optical sensor detects a change in position of the free end of the measuring unit due to torque transmitted to the fixed slide ring. Preferably, the optical sensor is a reflective type, detecting, for example, a light beam, such as a laser beam, reflected from the free end of the measuring unit. Alternatively, the optical sensor is an optical fiber Bragg grating (FBG) sensor. In particular, optical sensors have the advantage that they do not require current for measurement by the measuring unit, making them suitable for use in sealing work where there is a risk of explosion, etc. When the measuring unit is configured as a flat rod, it is preferable that a special reflective surface for the optical sensor is formed on at least one flat side of the flat rod. This can particularly improve the accuracy of the determination.

[0012] Alternatively, the torque meter's sensor is a strain gauge. Strain gauge sensors are very cost-effective to provide and very robust in design. They can be used, for example, in sealing operations in the presence of multiple dust particles, where optical measurement methods provide insufficient results.

[0013] Alternatively, the torque meter's sensor is a piezoelectric element, which is very robust and relatively cost-effective to provide. Since a current also flows through a piezoelectric sensor, its field of use is usually limited to gaseous media, where no electrical short circuit occurs.

[0014] A particularly simple and cost-effective design is possible if the groove in the stationary slide ring extends in the axial direction of the mechanical seal assembly, so that the groove is parallel to the central axis of the shaft to be sealed.

[0015] More preferably, the fixed slide ring is axially biased by a biasing device, in which case a pressure ring is preferably provided between the biasing device and the fixed slide ring, and particularly preferably, the biasing device consists of a plurality of individual spring elements arranged along the circumference of the mechanical seal.

[0016] Furthermore, the mechanical seal assembly preferably includes a controller configured to determine wear on the sliding surface of the mechanical seal based on the detected torque on the stationary slide ring. The controller is particularly preferably configured to determine wear on the sliding surface of the slide ring based on the magnitude of the torque. In this case, for example, a torque threshold value can be stored in a database and the detected torque value can be compared with the threshold value. If the threshold value is exceeded, this indicates excessive wear of the sliding surface, and the controller unit may output, for example, a replacement signal or a replacement message.

[0017] Furthermore, the controller is configured to operate the mechanical seal assembly so that contact occurs between the sliding surfaces of the rotating slide ring and the fixed slide ring, and the torque meter detects the contact torque generated when the sliding surfaces contact, and determines the wear of the sliding surfaces based on the contact torque. Determining the torque when the sliding surfaces contact is a reference for the wear of the sliding surfaces. This may occur, for example, when the rotational speed of the shaft to be sealed is low and there is not yet or not enough medium present in the seal gap to lift the sliding surfaces of the slide rings.

[0018] More preferably, the controller unit is configured to detect the breakaway torque of the mechanical seal when the mechanical seal is in a stopped state. When the mechanical seal is stopped, the sliding surfaces of the rotating slide ring and the fixed slide ring are in contact with each other. When the rotating slide ring rotates relative to the fixed slide ring, the breakaway torque is reached. This can be reliably and easily determined using the torque meter according to the present invention. Again, the greater the breakaway torque of the mechanical seal assembly, the greater the wear on the sliding surfaces of the slide rings. If the breakaway torque threshold is exceeded, it can be determined that excessive wear has occurred and that the seal ring needs to be replaced.

[0019] The present invention further relates to a method for inspecting the wear of the sliding surfaces of the mechanical seal assembly according to the present invention as described above, the method comprising the steps of detecting a torque acting on the stationary slide ring and comparing the detected torque with a stored torque threshold, and if the torque is greater than the torque threshold, it is determined that there is excessive wear on the sliding surfaces. In this case, the method according to the present invention enables the above-mentioned advantages.

[0020] More preferably, in this case, the method includes operating the mechanical seal assembly at a rotational speed such that the sliding surfaces of the rotating slide ring and the stationary slide ring contact each other. In this case, a contact torque generated on the stationary slide ring when the sliding surfaces contact is detected, and the detected contact torque is compared with a stored contact torque threshold. If the contact torque is greater than the threshold, it is determined that there is excessive wear on the sliding surfaces. Then, for example, a signal or message may be output, and the slide ring may be replaced.

[0021] Particularly preferably, the method according to the present invention detects the breakaway torque from the standstill state of the mechanical seal as the contact torque, which is as described above and in this case the torque value at which the relative rotation of the rotating slide ring with respect to the fixed slide ring begins.

[0022] Preferably, the torque of the stationary slide ring is continuously detected during operation of the mechanical seal. During normal operation of the mechanical seal, there is no direct contact between the sliding surfaces of the slide rings. However, even during operation, a constant torque is always applied to the stationary slide ring, and this torque increases as the sliding surface wear increases. Therefore, the torque detected during operation also serves as an indicator of the wear of the sliding surface of the slide ring. When the torque detected during operation exceeds the threshold, it is suggested that the slide ring needs to be replaced.

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic cross-sectional view of a mechanical seal assembly according to a first embodiment of the invention. [Figure 2] FIG. 2 is a schematic partial plan view of the mechanical seal assembly of FIG. 1. [Figure 3] FIG. 2 is a partial perspective view of the mechanical seal assembly of FIG. 1. [Figure 4] FIG. 2 is a partial side view of the mechanical seal assembly of FIG. 1. [Figure 5] FIG. 4 is a schematic cross-sectional view of a mechanical seal assembly according to a second embodiment of the invention. [Figure 6] FIG. 4 is a schematic cross-sectional view of a mechanical seal assembly according to a third embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The mechanical seal assembly 1 and a method for inspecting the wear of the sliding surfaces of the mechanical seal assembly will be described in detail below with reference to FIGS.

[0026] As shown in Figure 1, the mechanical seal assembly 1 includes a mechanical seal 2 having a rotating slide ring 3 and a stationary slide ring 4. A seal gap 5 is defined between a sliding surface 3a of the rotating slide ring 3 and a sliding surface 4a of the stationary slide ring 4. During operation, the sliding surfaces 3a and 4a of the slide rings are normally not in contact with each other.

[0027] In this case, the mechanical seal assembly 1 seals the product region 13 from the atmosphere region 14 at the shaft 17 .

[0028] The rotating slide ring 3 is connected to the shaft 17 via the slide ring carrier 30 , and the rotation of the shaft is transmitted to the rotating slide ring 3 via the slide ring carrier 30 .

[0029] The fixed slide ring 4 is arranged non-rotatably in a housing 8. As can be seen in Figure 1, the housing 8 comprises a sleeve region 80 extending in the axial direction XX of the mechanical seal assembly 1. In this case, the fixed slide ring 4 is movable in the axial direction XX on the sleeve region 80. A pressure ring 11 is provided on the rear side 4b of the fixed slide ring 4, which is pressurized in the axial direction XX against the rotating slide ring 3 by a pressurizing element 10, in particular a plurality of spring elements.

[0030] The mechanical seal assembly 1 further comprises a torque meter 6, which is shown in detail in Figures 1 to 4. The torque meter 6 comprises a measurement unit 7 and a sensor 9, which in this embodiment is an optical sensor. In this case, the sensor 9 comprises an optical fiber 90 and a light source / receiver assembly 91. The light source / receiver assembly 91 emits light within the optical fiber 90 and receives a corresponding reflection.

[0031] The measuring unit 7 is shown in detail in Figures 1 and 3 in its overall view. The measuring unit 7 comprises a flat rod 70, one end of which is fixed to the housing 8. In this case, the flat rod 70 is fixed at one end via a base plate 73, which is fixed to the housing 8 using bolts 15, 16. The free end 71 of the flat rod 70 protrudes into a groove 40 formed in the outer periphery of the fixed slide ring 4. A foot 72 connected to the base plate has a greater thickness than the free end 71 (see Figure 3).

[0032] As can be seen in particular from Figure 1, the groove 40 extends in the axial direction XX of the mechanical seal assembly 1. As can also be seen from Figure 1, in this case the free end 71 extends in the axial direction XX from the base plate 73 through the entire groove 40 and has a small overhang that axially extends beyond the groove 40.

[0033] As shown by the dashed line in Figure 1, an optical fiber 90 is also guided to the groove 40, the optical fiber 90 having a 90° bend (see Figure 2). In this case, a reflective surface 75 is provided on the flat side 71a of the free end 71 of the flat rod 70 (see Figure 2). A light beam (arrow A) emitted by the light source / receiver assembly 91 is reflected therefrom and sent back to said light source / receiver assembly.

[0034] Furthermore, flat rod 70 is provided with protruding regions 74 on both sides (see especially Figures 2 and 3), which are also located within groove 40. In this case, protruding regions 74 are configured such that there is a small gap 18 on each side relative to the walls of groove 40 (Figure 2).

[0035] The groove 40 in the fixed slide ring 4 is formed straight and parallel to the axial direction XX, allowing the fixed slide ring 4 to move in the axial direction. For example, in FIG. 1, if the shaft 17 moves leftward, the rotating slide ring 3 also moves axially, but this can be readjusted by the preload force F applied by the preload element 10 via the pressure ring 11. As can be seen in FIG. 3, in this case, the torque meter 6 fixed to the housing 8 remains stationary, but the determination and recording area of ​​the torque meter 6 remains positioned in the groove 40 in the fixed slide ring 4.

[0036] In this case, the function and measurement method of the torque detection device 6 are as follows: During normal operation of the mechanical seal assembly 1, when a medium is present in the seal gap 5 and the sliding surfaces 3a, 4a of the slide rings 3, 4 are not in contact with each other, if a torque acts on the stationary slide ring 4 (schematically indicated by arrow B in FIG. 4 ), the groove wall 40a of the groove 40 comes into contact with the measuring unit 7, in particular one of the protruding regions 74. As a result, there is no longer a gap 18 between the groove wall 40a and the protruding region 74. This causes a deformation of the flat rod 70, such that the sensor 9, which continuously or intermittently emits a light beam A, can detect a change in the reflection of the light beam, resulting in a corresponding change in the position of the measuring unit 7, in particular its free end 71. This change in reflection can then be detected by the sensor 9. The sensor 9 is connected to a controller 12, which evaluates the sensor signal. The torque acting on the stationary slide ring 4 can be determined from the change in the sensor signal.

[0037] In this case, the controller 12 is further configured to compare the torque value thus determined with a torque threshold value. If the determined torque value exceeds the threshold value, this is a clear indication of wear of the sliding surfaces 3a, 4a, since the torque transmission from the rotating slide ring 3 to the fixed slide ring 4 is much smaller when the sliding surfaces 3a, 4a are not worn than when the sliding surfaces show wear, e.g., undulations or waves.

[0038] Torque measurements can be performed when the rotating and fixed slide rings are in contact at their sliding surfaces 3a, 4a, for example, when the shaft 17 is stationary or at very low rotational speeds where contact at the sliding surfaces 3a, 4a still exists. In the case of worn slide rings, contact between the sliding surfaces lasts longer than in the case of new slide rings. Therefore, the torque transmitted from the rotating slide ring 3 to the fixed slide ring 4 is significantly higher than in the case of new slide rings without wear or corrugations. In particular, the breakaway torque from the standstill of the shaft 17 can also be detected, and this breakaway torque is also significantly higher in the case of worn slide rings than in the case of slide rings with no or little wear.

[0039] As can be seen in particular from Figures 1 and 4, the fixed slide ring 4 comprises a radially outwardly facing peripheral flange area 41, in the interior of which is formed a groove 40. In this case, the flange area 41 is free of sliding surfaces (see also Figure 4).

[0040] When a torque is transmitted from the rotating slide ring 3 to the fixed slide ring 4, a circumferential force is generated acting on the flat rod 70, which is loaded in a bending manner and deforms. This deformation can be detected by optical path measurement. In this case, the controller 12 is configured to measure the force acting on the measuring unit 7, for example, based on known material parameters of the measuring unit 7, and to calculate the torque acting on the fixed slide ring 4 based on the known slide ring geometry.

[0041] In this case, the torque acting on the fixed slide ring 4 can always be detected due to the axial arrangement of the grooves 40, regardless of the axial position of the fixed slide ring 4. The measuring unit 7 is preferably made from stainless steel.

[0042] FIG. 5 shows a mechanical seal assembly 1 according to a second embodiment of the invention. Identical or functionally identical parts are designated by the same reference symbols as in the first embodiment. The second embodiment is substantially identical to the first embodiment, except that a strain gauge 92 is used as the sensor 9 instead of an optical sensor. As shown in FIG. 5 , the strain gauge 92 is disposed in the region of the foot 72 of the flat rod 70. When torque is transmitted to the fixed slide ring 4, a force is transmitted to the free end 71 of the flat rod 70 of the measurement unit 7, as in the first embodiment. The electrical resistance of the strain gauge 92 changes depending on the degree of curvature of the flat rod 70. This change can be detected by the controller 12, and based on this, the force acting on the measurement unit 7 due to the torque transmitted to the fixed slide ring 4 can be determined. Otherwise, this embodiment is identical to the previous embodiment, and the description of the previous embodiment is referred to. Alternatively, an optical FBG sensor can be used in place of the strain gauge 92.

[0043] FIG. 6 shows a mechanical seal device 1 according to a third embodiment of the present invention. Identical or functionally identical parts are designated by the same reference symbols as in the previous embodiment. In this third embodiment, the sensor 9 is a piezoelectric sensor 93 arranged on the groove wall 40a of the groove 40. When torque is transmitted from the rotating slide ring 3 to the fixed slide ring 4, a force is transmitted to the measuring unit 7, which bends, particularly in the region of the free end 71. This results in a force acting on the piezoelectric sensor 93, which in turn changes its electrical resistance, which can be detected by the controller 12. Based on the changed electrical resistance of the piezoelectric sensor, the controller 12 can then determine the force acting on the piezoelectric sensor 93, and thus the torque. To enable torque detection regardless of the direction of rotation, the piezoelectric sensors 93 are preferably arranged on both groove walls of the groove 40. In other respects, this embodiment is identical to the previous embodiment, and reference is made to the description of the previous embodiment.

[0044] In this case, the method according to the present invention for inspecting the wear state of the sliding surfaces 3a, 4a is performed in all embodiments, particularly when the sliding surfaces of the slide rings come into contact with each other. When the sliding surfaces come into contact, the contact torque can be detected by the various sensors 9 of the torque detection device 6 described in the embodiments. The contact torque is then compared with a threshold value stored in the controller 12. If the contact torque exceeds the threshold value, the controller 12 immediately determines that excessive wear exists on the sliding surfaces 3a, 4a of the slide rings. At this point, a signal or message can be output, for example, to warn of the excessive wear and recommend replacing the slide rings.

[0045] Furthermore, in particular, the breakaway torque of the sliding surface can be detected from the stopped state of the shaft 17. If the breakaway torque is also greater than a predetermined threshold, the controller 12 can similarly determine excessive wear of the sliding surface and output a corresponding indicator. [Explanation of symbols]

[0046] 1 Mechanical Seal Assembly 2 Mechanical seal 3 Rotating Slide Ring 3a Sliding surface of rotating slide ring 4 Fixed slide ring 4a Sliding surface of rotating slide ring 4b Rear side of fixed slide ring 5 Seal gap 6 Torque meter 7 Measuring Unit 8. Housing 9 Sensors 10 Preload element 11 Pressure Ring 12 Controllers 13 Product Area 14 Atmospheric Region 15, 16 Bolts 17 Shaft 18 Gap between groove wall and measuring unit 30 Slide Ring Carrier 40 grooves 40a Groove wall 41 Flange area 70 Flat Rod 71 Free end 71a flat side 72 Flat rod foot 73 Base Plate 74 Prominent area 75 Reflective surface 80 sleeve area 90 Optical Fiber 91 Light Source / Receiver Assembly 92 Strain gauge 93 Piezo Sensor A Light beam B Force transmitted to the fixed slide ring F Pressure force XX Axial direction

Claims

1. a mechanical seal (2) having a rotating slide ring (3) and a fixed slide ring (4) that define a seal gap (5) between their sliding surfaces (3a, 4a); a torque meter (6) configured to detect a torque acting on the fixed slide ring (4); The torque meter (6) comprises a measurement unit (7) and a sensor (9), The measuring unit (7) is fixed to the housing (8) by a foot (72) and has a free end (71) protruding into a groove (40) formed on the outer periphery of the fixed slide ring (4); The sensor (9) is configured to detect a change in position of the measuring unit (7) within the groove (40); a controller (12) configured to determine wear of the sliding surfaces (3 a, 4 a) of the mechanical seal (2) based on the detected torque of the fixed slide ring (4); The controller (12) is further configured to operate the mechanical seal assembly (1) so that contact between the rotating slide ring (3) and the fixed slide ring (4) occurs on the sliding surfaces (3 a, 4 a), and is further configured to detect a contact torque generated when the sliding surfaces (3 a, 4 a) contact each other, and to determine wear of the sliding surfaces based on the contact torque.

2. 2. A mechanical seal assembly according to claim 1, wherein the measuring unit (7) comprises a flat rod (70) fixed at one end.

3. 2. The mechanical seal assembly according to claim 1, wherein protruding regions (74) are formed on both sides of the free end (71) of the measuring unit (7) facing the groove wall (40a) of the groove (40).

4. 2. The mechanical seal assembly according to claim 1, wherein the foot (72) of the measuring unit (7) has a thickness greater than the free end (71).

5. The mechanical seal assembly of claim 1, wherein the sensor (9) is an optical sensor.

6. 6. The mechanical seal assembly according to claim 5, wherein the measuring unit (7) is formed with a reflective surface (75) for the optical sensor.

7. The mechanical seal assembly of claim 1, wherein the sensor (9) comprises a strain gauge (92) arranged in the measurement unit (7).

8. The mechanical seal assembly of claim 1, wherein the sensor (9) comprises a piezoelectric sensor (93) disposed on a groove wall (40a) within the groove (40).

9. said groove (40) extending in the axial direction (X-X) of said mechanical seal assembly (1); and / or The mechanical seal assembly according to claim 1, wherein the stationary slide ring (4) is axially (X-X) preloaded by a preloading element (10).

10. 10. The mechanical seal assembly according to claim 1, wherein the controller is further configured to determine wear of the sliding surfaces based on a comparison between the detected torque value and a threshold value if the detected torque value is greater than the threshold value.

11. a mechanical seal (2) having a rotating slide ring (3) and a fixed slide ring (4) that define a seal gap (5) between their sliding surfaces (3a, 4a); a torque meter (6) configured to detect a torque acting on the fixed slide ring (4); The torque meter (6) comprises a measurement unit (7) and a sensor (9), The measuring unit (7) is a mechanical seal assembly fixed to a housing (8) by feet (72) and having a free end (71) protruding into a groove (40) formed on the outer periphery of the fixed slide ring (4), 1. A method for inspecting wear of the sliding surfaces (3 a, 4 a) of the mechanical seal assembly, wherein the sensor (9) is configured to detect a change in position of the measuring unit (7) in the groove (40), operating the mechanical seal assembly; detecting a torque acting on the fixed slide ring (4); comparing the detected torque with a stored torque threshold; If the torque is greater than the torque threshold, it is determined that there is excessive wear on the sliding surfaces (3 a, 4 a); operating the mechanical seal assembly at a rotational speed such that the sliding surfaces (3a, 4a) of the rotating slide ring (3) and the stationary slide ring (4) come into contact; detecting a contact torque generated in the fixed slide ring (4) when the sliding surfaces contact each other; comparing the detected torque with a stored contact torque threshold; determining that there is excessive wear on the sliding surfaces (3a, 4a) if the contact torque is greater than the contact torque threshold.

12. 12. The method according to claim 11, further comprising detecting a breakaway torque of the sliding surfaces from a rest state of the mechanical seal (2) and comparing the detected breakaway torque with a breakaway torque threshold, and determining that there is excessive wear on the sliding surfaces (3 a, 4 a) if the detected breakaway torque is greater than the breakaway torque threshold.

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