Mechanical Seal Device

Abstract

The present invention relates to a mechanical seal device for sealing a process chamber (6) filled with a non-toxic gaseous process medium from a bearing chamber (8). The mechanical seal device comprises a first mechanical seal (2) having a rotating slide ring (20) with a first sliding surface (20a) and a fixed slide ring (21) with a second sliding surface (21a) and a first seal gap (22) defined between the sliding surfaces (20a, 21a), a second mechanical seal (3) having a rotating slide ring (30) with a third sliding surface (30a) and a fixed slide ring (31) with a fourth sliding surface (31a) and a second seal gap (32) defined between the sliding surfaces (30a, 31a), and a fixed slide ring (32) of the first mechanical seal (2). a first preload device (4) for prestressing a fixed slide ring (31) of the second mechanical seal (3) in the axial direction (XX); a second preload device (5) for prestressing a fixed slide ring (31) of the second mechanical seal (3) in the axial direction (XX); and a fluid chamber (7) arranged between the first mechanical seal (2) and the second mechanical seal (3) and in fluid communication with the first seal gap and the second seal gap, for receiving leakage from the process chamber (6) via the first seal gap (22) during operation, the fluid chamber (7) having a return line (9) extending therefrom, the return line (9) being configured to return the process medium from the fluid chamber (7) to the process area.

Description

[Technical Field]

[0001] The present invention relates to a gas-lubricated mechanical seal device for sealing a process chamber filled with a non-toxic gaseous medium against a bearing chamber in which a bearing for supporting a shaft is disposed, and to a compressor device. [Background technology]

[0002] Various designs of mechanical seal devices are known in the prior art. The so-called tandem design, in which two mechanical seals are arranged in series on a shaft and a barrier gas is supplied to the intermediate space between the two mechanical seals, has been demonstrated to be capable of sealing gaseous media. The barrier gas is supplied by a barrier gas device, which, in addition to additional structural effort, also entails continuous operating costs during operation for generating the barrier gas, which must be supplied under a certain pressure. For example, Patent Document 1 describes a gas-lubricated mechanical seal device with a barrier gas device that uses nitrogen as the barrier gas. However, recently, there has been an increasing demand for applications that require the sealing of environmentally non-toxic media such as carbon dioxide and nitrogen. In particular, the compression of carbon dioxide has attracted attention, for example, for removing carbon dioxide from ambient air to reduce the greenhouse effect or for compressing carbon dioxide for storage in a reservoir. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] German Patent Publication No. DE102018208519 Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, an object of the present invention is to provide a mechanical seal device and a compressor device that have a simple structure, are capable of sealing an environmentally non-toxic gaseous medium, in particular carbon dioxide or nitrogen, and can be easily manufactured at low cost.

[0005] This object is achieved by a mechanical seal device having the features of claim 1 and a compressor device having the features of claim 10. The dependent claims specify preferred embodiments of the invention. [Means for solving the problem]

[0006] The gas-lubricated mechanical seal device according to the present invention for sealing a process chamber filled with a non-toxic gaseous medium from a bearing chamber, as described in claim 1, offers the advantage of being particularly cost-effective and reliable in sealing the process chamber from a bearing chamber where ambient pressure prevails. A separate, expensive barrier gas device is not required to seal the rotating component, particularly the shaft. Therefore, the mechanical seal device according to the present invention can be provided at particularly low cost. This is achieved in accordance with the present invention by the mechanical seal device comprising a first mechanical seal and a second mechanical seal. The first mechanical seal comprises a rotating slide ring and a fixed slide ring, with a first seal gap defined between their sliding surfaces. The second mechanical seal comprises a rotating slide ring and a fixed slide ring, with a second seal gap defined between their sliding surfaces. Furthermore, the mechanical seal device comprises a first preload device and a second preload device. The first preload device prestresses the stationary slide ring of the first mechanical seal, and the second preload device prestresses the stationary slide ring of the second mechanical seal. A fluid chamber is disposed between the first mechanical seal and the second mechanical seal, and a return line within the housing extends from the fluid chamber, configured to return a gaseous non-toxic medium to the process region. The fluid chamber is in fluid communication with the first seal gap and the second seal gap, and receives leakage from the process region through the first seal gap during operation. The first mechanical seal and the second mechanical seal are arranged in series such that the rear surface of the stationary slide ring of the first mechanical seal and the rear surface of the stationary slide ring of the second mechanical seal are aligned facing each other. Furthermore, a first step is formed on the inner circumference of the stationary slide ring of the first mechanical seal. The first minimum inner diameter D1 of the stationary slide ring of the first mechanical seal is smaller than the second maximum inner diameter D2 of the stationary slide ring of the first mechanical seal. When the mechanical seal is in an inoperative state, the first seal gap of the first mechanical seal is open, allowing process gas to flow from the process chamber through the open seal gap into the fluid chamber between the first mechanical seal and the second mechanical seal.Furthermore, a second step is formed on the outer periphery of the stationary slide ring of the second mechanical seal. The first minimum outer diameter D3 of the stationary slide ring of the second mechanical seal is smaller than the second maximum outer diameter D4 of the stationary slide ring of the second mechanical seal. When the mechanical seal device is in an inoperative state, the second seal gap of the second mechanical seal is closed or has almost no leakage. Furthermore, a first leakage direction in the first seal gap of the first mechanical seal extends from the outside to the inside from the process chamber to the fluid chamber, and a second leakage direction in the second seal gap of the second mechanical seal extends from the inside to the outside from the fluid chamber to the bearing chamber.

[0007] Therefore, when the mechanical seal device is in an inoperative state—i.e., when the rotating component it seals is not rotating—the first seal gap of the first mechanical seal is open, and the second seal gap of the second mechanical seal is closed. Leaked process medium is returned from the fluid chamber to the process chamber via a return line. When the mechanical seal device is in an inoperative state, the second mechanical seal seals the fluid chamber from the bearing chamber. When the rotating component it seals is rotating, both mechanical seals are in an operative state. A first small leakage occurs from the process chamber through the first seal gap to the fluid chamber, and a second small leakage occurs from the fluid chamber to the bearing chamber through the second seal gap of the second mechanical seal. As a result, no separate barrier medium is required for the two mechanical seals to operate; instead, the first and second mechanical seals are lubricated by the process medium. The majority of leakage through the first seal gap of the first mechanical seal is returned to the process area via the return line and is therefore not lost.In the present invention, the term gaseous non-toxic medium is understood to mean a medium in a gaseous mass state or a supercritical state.

[0008] The mechanical seal device of the present invention exhibits very good sealing performance, even at high speeds when used on a compressor shaft, for example. By arranging a return line from the fluid chamber located between the first and second mechanical seals to the process area, it is possible to recover most of the first leakage through the first seal gap and return it to the process. During operation, the only remaining leakage is the second leakage through the second seal gap of the second mechanical seal, but this is relatively small.

[0009] According to a preferred embodiment of the present invention, the rotary slide ring of the first mechanical seal has a plurality of first conveying grooves on its sliding surface, which are preferably arranged on the outer periphery of the rotary slide ring of the first mechanical seal and preferably extend inward in a crescent shape.

[0010] More preferably, the stationary slide ring of the second mechanical seal is provided with a second conveying groove, which is preferably arranged on the inner periphery so as to extend outward, in particular extending in a crescent shape from the inner periphery of the stationary slide ring of the second mechanical seal to the outside.

[0011] Preferably, the conveying grooves are arranged on all of the slide rings of the first mechanical seal and the second mechanical seal.

[0012] The first pressure differential between the process chamber and the fluid chamber is preferably at least three times higher than the second pressure differential between the fluid chamber and the bearing chamber, and the first pressure differential is preferably at least five times higher, and particularly preferably at least ten times higher, than the second pressure differential at the second mechanical seal.

[0013] More preferably, during operation, the first leakage rate through the first seal gap of the first mechanical seal is at least two times greater than the second leakage rate through the second seal gap of the second mechanical seal.

[0014] Preferably, the first mechanical seal and the second mechanical seal are arranged in a common sleeve.

[0015] The process medium is preferably carbon dioxide or nitrogen. Alternatively, the process medium is a refrigerant, for example, R134a or R245fa.

[0016] The first inner diameter D1 of the fixed sliding ring of the first mechanical seal is more preferably within the range of the following inequality when the maximum second inner diameter is D2. 0.8×D2 ≦ D1 < D2

[0017] In particular, D1 is within the range of 0.9×D2 ≦ D1 < D2.

[0018] This means that the first inner diameter D1 is within a range that is at most 20% smaller than the second inner diameter D2 of the fixed sliding ring.

[0019] The first outer diameter D3 of the fixed sliding ring of the second mechanical seal is more preferably within the range of the following inequality when the maximum second outer diameter is D4. 8×D4 ≦ D3 < D4

[0020] In particular, D3 is within the range of 0.9×D4 ≦ D3 < D4.

[0021] This means that the first outer diameter D3 is within the range from 80% of the second outer diameter D4 to the outer diameter D4 of the second mechanical seal. In particular, this enables adjustment of the closing force acting on the second mechanical seal.

[0022] Furthermore, the present invention relates to a compressor device and a mechanical seal device for compressing a gaseous medium with a compressor according to the present invention.

Brief Description of the Drawings

[0023] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The drawings are as follows. [Figure 1] Schematic cross-sectional view of a mechanical seal device according to a preferred embodiment of the present invention. [Figure 2] FIG. 4 is a schematic top view of the sliding surface of the rotating slide ring of the first mechanical seal. [Figure 3] FIG. 4 is a schematic top view of the sliding surface of the fixed slide ring of the first mechanical seal. [Figure 4] FIG. 10 is a schematic top view of the sliding surface of the rotating slide ring of the second mechanical seal. [Figure 5] FIG. 10 is a schematic top view of the sliding surface of the fixed slide ring of the second mechanical seal. DETAILED DESCRIPTION OF THE INVENTION

[0024] A mechanical seal device 1 according to a preferred embodiment of the present invention will be described in detail below with reference to FIGS.

[0025] The mechanical seal device 1 seals the process chamber 6 against the bearing chamber 8. In the bearing chamber 8, a bearing 80 that supports the shaft 18 is disposed.

[0026] The mechanical seal device 1 comprises two mechanical seals, a first mechanical seal 2 and a second mechanical seal 3. The two mechanical seals 2, 3 are arranged in series and seal the process chamber 6 from the bearing chamber 8. This is a so-called double seal.

[0027] Within the process chamber 6 there is an environmentally non-toxic gaseous medium such as carbon dioxide (CO2) or nitrogen.

[0028] The first mechanical seal 2 includes a rotating slide ring 20 having a first slide surface 20a and a stationary slide ring 21 having a second slide surface 21a. A first seal gap 22 is defined between the two slide surfaces 20a, 21a. The rotating slide ring 20 is configured to rotate by a first drive element 23.

[0029] The second mechanical seal 3 includes a rotating slide ring 30 having a third slide surface 30a and a fixed slide ring 31 having a fourth slide surface 31a. A second seal gap 32 is defined between the two slide surfaces 30a, 31a. The rotating slide ring 30 of the second mechanical seal 3 is configured to rotate by a second drive element 33.

[0030] The first mechanical seal 2 and the second mechanical seal 3 are arranged on a common sleeve 11 fixed to a shaft 18. The mechanical seals are configured without having a through hole.

[0031] 1, the first mechanical seal 2 and the second mechanical seal 3 are arranged so that the rear surface 21b of the stationary slide ring 21 of the first mechanical seal 2 faces the rear surface 31b of the stationary slide ring 31 of the second mechanical seal 3. The stationary slide ring 21 of the first mechanical seal 2 and the stationary slide ring 31 of the second mechanical seal 3 are fixed to the housing 15.

[0032] The stationary slide ring 21 of the first mechanical seal 2 is prestressed in the axial direction of the mechanical seal device 1 by a first preload device 4. The stationary slide ring 31 of the second mechanical seal 3 is prestressed in the axial direction by a second preload device 5. In this exemplary embodiment, the preload devices are several cylindrical springs arranged around the periphery of the rear faces of the stationary slide rings 21, 31.

[0033] As can be seen in Figure 1, a fluid chamber 7 is formed between the first mechanical seal 2 and the second mechanical seal 3. As shown schematically in Figure 1, a return line 9 starts from the fluid chamber 7 and returns to the compressor 10. This allows fluid to be sent through the return line 9 in the direction of the process area and returned to the compressor 10.

[0034] 2 and 3, many first conveying grooves 12 are provided in the rotary slide ring 20 of the first mechanical seal 2. The first conveying grooves 12 extend inward in a crescent shape from the outer periphery of the rotary slide ring 20. No grooves are formed in the slide surface 21a of the fixed slide ring 21.

[0035] 4 and 5, no conveying groove is formed in the rotating slide ring 30 of the second mechanical seal 3. However, a second conveying groove 13 is formed in the fixed slide ring 31. The second conveying groove 13 extends in a crescent shape from the inner periphery of the fixed slide ring 31 toward the outside.

[0036] Thus, in the first mechanical seal 2, the conveying direction through the first seal gap 22 is from the radially outer side to the radially inner side, which is shown in Figure 1 as a first leakage direction 16 (arrow). In the second mechanical seal 3, the second conveying groove 13 defines a radially outer conveying direction, so that a second leakage direction 17 is from the radially inner side to the radially outer side.

[0037] 1, the stationary slide ring 21 of the first mechanical seal 2 has a first step 41 on its inner circumference. The first minimum inner diameter D1 of the stationary slide ring 21 of the first mechanical seal 2 is smaller than the second maximum inner diameter D2 of the stationary slide ring 21 of the first mechanical seal 2. This ensures that the first seal gap 22 remains open when the shaft 18 is not rotating, i.e., when the compressor 10 is not operating.

[0038] In the second mechanical seal 3, a second step 42 is formed on the outer periphery of the stationary slide ring 31 of the second mechanical seal 3. The first minimum outer diameter D3 of the stationary slide ring 31 is smaller than the second maximum outer diameter D4 of the stationary slide ring 31 of the second mechanical seal 3. By using the spring force of the second preload device 5, the second seal gap 32 is ensured to be closed or nearly closed when the compressor 10 is in a stopped state, i.e., when the shaft 18 is not rotating. In other words, the two slide surfaces 30a, 31a come into contact with each other, completely or nearly completely sealing the second mechanical seal 3, so that all or most of the fluid cannot flow from the fluid chamber 7 toward the bearing chamber 8.

[0039] During operation of the mechanical seal device 1, i.e., when the shaft 18 rotates, leakage occurs from the process chamber 6 to the fluid chamber 7 and from the fluid chamber 7 to the bearing chamber 8 through the first seal gap 23. As can be seen in Figure 1, the flow directions through the first seal gap 22 and the second seal gap 32 are radially opposite. In other words, during operation, the flow direction through the first seal gap 22 is radially inward (arrow 16), while the flow direction in the second seal gap 32 is radially outward (arrow 17).

[0040] Thus, during operation of the compressor 10, the first mechanical seal 2 and the second mechanical seal 3 seal normally, but the leakage rates through the seal gaps of the first mechanical seal 2 and the second mechanical seal 3 are different. The leakage rate through the first seal gap 22 of the first mechanical seal 2 is much greater than the leakage rate through the second seal gap 32 of the second mechanical seal 3. Furthermore, leakage that enters the fluid chamber 7 from the process chamber 6 through the first seal gap 22 is returned to the compressor 10 via the return line 9. Arrow 19 in FIG. 1 indicates the direction of return flow from the fluid chamber 7 toward the process area and into the compressor 10. This means that much of the leakage can be recovered through the first mechanical seal 2 and reinjected into the compressor 10 at an appropriate point depending on the pressure level of the returned gaseous process medium. Since the process medium is a gas that is not toxic to the environment, any leakage that leaks from the fluid chamber 7 and enters the bearing chamber 8 through the second seal gap 32 of the second mechanical seal 3 can be released into the environment without any problems.

[0041] In this way, the mechanical seal device 1 according to the present invention uses the process medium as the barrier medium for the first mechanical seal 2 and the second mechanical seal 3. This means that a separate barrier fluid device, which is normally present in mechanical seals, does not need to be provided to provide a barrier medium for the mechanical seals, which significantly reduces the cost of the mechanical seal device 1.

[0042] In this manner, the present invention provides a self-supplying bearing seal that seals the process chamber 6 from the bearing chamber 8. Thus, during operation of the mechanical seal device 1, the process medium provides barrier fluid to both mechanical seals 2, 3. When the mechanical seal device 1 is not in operation, the first seal gap 22 of the first mechanical seal 2 is open, and the second seal gap 32 of the second mechanical seal 3 is completely or substantially closed due to the spring force of the second preload device 5 and the diameter difference between the first outer diameter D3 and the second outer diameter D4 of the stationary slide ring 31. This prevents the process medium that has leaked into the fluid chamber 7 through the first seal gap 22 from leaking into the bearing chamber 8, or only minimal leakage occurs from the fluid chamber 7 toward the bearing chamber 8.

[0043] The second leakage direction 17 from the radially inner side to the radially outer side of the second mechanical seal 3 also prevents oil needed to lubricate the bearing 80 from entering the fluid chamber 7 from the bearing chamber 8.

[0044] The present invention thus provides a very cost-effective mechanical seal arrangement 1 for sealing bearings that does not require any supply of barrier medium. The process medium to be sealed is used as the barrier medium in both mechanical seals. Since the process medium can be an environmentally non-toxic gas, such as carbon dioxide or nitrogen, or a refrigerant such as R134a or R245, leakage of the process medium through the second seal gap 32 during operation is not significant.

[0045] A particularly compact design can also be achieved by arranging the two rear faces 21b, 31b of the two fixed slide rings 21, 31 back to back. The return line 19 extends between the first mechanical seal 2 and the second mechanical seal 3 (see FIG. 1). Furthermore, the mechanical seal device 1 according to the present invention does not require additional labyrinth seals, lip seals, etc. It is also possible to design all of the slide rings of the first and second mechanical seals 2, 3 without through holes, etc. This offers significant cost advantages, especially in the manufacture of the mechanical seals 2, 3.

[0046] In addition to the above description of the invention, explicit reference is made to the diagrammatic representations of the invention in Figures 1-5 for a supplemental disclosure of the invention. [Explanation of symbols]

[0047] 1 Mechanical seal device 2. First mechanical seal 3 Second mechanical seal 4. First preload device 5 Second preload device 6 Process Chamber 7 Fluid chamber 8 Bearing chamber 9 Return Line 10 Compressor 11 Sleeve 12 First conveying groove 13 Second conveying groove 15 Housing 16 First leak direction 17 Second leak direction 18 shaft 19 Return flow direction 20 Rotating Slide Ring 20a First slide surface 21 Fixed slide ring 21a Second slide surface 21b Rear surface of fixed slide ring 21 22 First seal gap 23 First driving element 30 Rotation Slide Ring 30a Additional sliding surface 31 Fixed slide ring 31a Fixed slide surface 31b Rear surface of fixed slide ring 31 32 Second seal gap 33 Second driving element 41 First Step 42 Second step 80 bearings D1: The smallest first inner diameter of the fixed slide ring 21 D2 Maximum second inner diameter of fixed slide ring 21 D3 Minimum first outer diameter of fixed slide ring 31 D4 Maximum second outer diameter of fixed slide ring 31 XX Axial direction

Claims

1. A mechanical seal device for sealing a process chamber (6) filled with a non-toxic gaseous process medium against a bearing chamber (8), comprising: a first mechanical seal (2) including a rotating slide ring (20) having a first slide surface (20a) and a stationary slide ring (21) having a second slide surface (21a), with a first seal gap (22) defined between the slide surfaces (20a, 21a); a second mechanical seal (3) including a rotating slide ring (30) having a third slide surface (30a) and a fixed slide ring (31) having a fourth slide surface (31a), with a second seal gap (32) defined between the slide surfaces (30a, 31a); a first preloading device (4) that applies prestress in the axial direction (X-X) to the fixed slide ring (21) of the first mechanical seal (2); a second preloading device (5) that applies prestress in the axial direction (X-X) to the fixed slide ring (31) of the second mechanical seal (3); a fluid chamber (7) disposed between the first mechanical seal (2) and the second mechanical seal (3), in fluid communication with the first seal gap and the second seal gap, for receiving leakage from the process chamber (6) through the first seal gap (22) during operation, the fluid chamber (7) having a return line (9) extending therefrom, the return line (9) being configured to return process medium from the fluid chamber (7) to a process area; The first mechanical seal (2) and the second mechanical seal (3) are arranged such that a rear surface (21b) of the stationary slide ring (21) of the first mechanical seal (2) and a rear surface (31b) of the stationary slide ring (31) of the second mechanical seal (3) face each other, The stationary slide ring (21) of the first mechanical seal (2) has a first step (41) on its inner periphery so that a first minimum inner diameter D1 of the stationary slide ring (21) of the first mechanical seal (2) is smaller than a second maximum inner diameter D2 of the stationary slide ring (21) of the first mechanical seal (2); the stationary slide ring (31) of the second mechanical seal (3) has a second step (42) on its outer periphery so that a first minimum outer diameter D3 of the stationary slide ring (31) of the second mechanical seal (3) is smaller than a second maximum outer diameter D4 of the stationary slide ring (31) of the second mechanical seal (3); When the mechanical seal device is in an inoperative state, the first seal gap (22) of the first mechanical seal (2) is open, allowing the process medium to flow from the process chamber (6) to the fluid chamber (7) through the open first seal gap (22), while the second seal gap (32) of the second mechanical seal (3) is closed. A mechanical seal device, wherein a first flow direction (16) in the first seal gap (22) extends from the outside to the inside from the process chamber (6) to the fluid chamber (7), and a second flow direction (17) in the second seal gap (32) extends from the fluid chamber (7) to the bearing chamber (8) from the inside to the outside.

2. The mechanical seal device according to claim 1, wherein the rotary slide ring (20) of the first mechanical seal (2) comprises a first conveying groove (12).

3. 3. The mechanical seal device according to claim 2, wherein the first conveying groove (12) extends inward from an outer periphery of the rotary slide ring (20) of the first mechanical seal (2).

4. 2. The mechanical seal device according to claim 1, wherein the fixed slide ring (31) of the second mechanical seal (3) comprises a second conveying groove (13).

5. 5. The mechanical seal device according to claim 4, wherein the second conveying groove (13) extends from an inner periphery of the fixed slide ring (31) of the second mechanical seal (3) toward an outer periphery.

6. 2. The mechanical seal device of claim 1, wherein a first pressure difference between the process chamber (6) and the fluid chamber (7) is at least three times higher than a second pressure difference between the fluid chamber (7) and the bearing chamber (8).

7. 2. The mechanical seal device according to claim 1, wherein the leakage rate of the process medium through the first seal gap (22) of the first mechanical seal (2) is at least twice as large as the leakage rate of the process medium from the fluid chamber (7) to the bearing chamber (8) through the second seal gap (32) of the second mechanical seal (3).

8. 2. The mechanical seal device according to claim 1, wherein the first mechanical seal (2) and the second mechanical seal (3) are arranged on a common sleeve (11).

9. The process chamber (6) contains carbon dioxide, nitrogen, or a refrigerant as a gaseous process medium; 2. The mechanical seal device of claim 1, wherein the mechanical seal device is arranged to seal the process chamber (6) against the bearing chamber (8).

10. The first inner diameter D1 of the stationary slide ring (21) of the first mechanical seal (2) is in the range of 0.8×D2≦D1<D2, and / or 2. The mechanical seal device according to claim 1, wherein the first outer diameter D3 of the stationary slide ring (31) of the second mechanical seal (3) is within a range of 0.8×D4≦D3<D4.

11. 1. A compressor apparatus for compressing a gaseous process medium, comprising: A compressor (10); A compressor apparatus comprising: a mechanical seal device according to any one of claims 1 to 10, for sealing a process chamber (6) against a bearing chamber (8) comprising a bearing (80) supporting a shaft (8) of the compressor (10).

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