Slip-ring seal assembly
Patent Information
- Application Number
- EP2023701038
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-02-07
- Filing Date
- 2023-01-17
- Publication Date
- 2024-12-18
AI Technical Summary
Existing mechanical seal arrangements for sealing non-toxic gaseous media, such as CO2 or nitrogen, require complex and costly separate sealing gas devices, which are inefficient and not environmentally friendly, especially when compressing CO2 to reduce the greenhouse effect.
A gas-lubricated mechanical seal arrangement featuring two mechanical seals in series, where the first seal is open when stationary and the second seal is closed, utilizing the process medium as a barrier medium, eliminating the need for a separate sealing gas device and allowing leakage to be routed back to the process area, thereby reducing operational costs and environmental impact.
This solution provides a cost-effective and reliable sealing mechanism with minimal leakage, even at high speeds, without the need for a separate barrier medium, effectively sealing non-toxic gases and allowing for the recovery of leaked gas, thus reducing operational costs and environmental impact.
Smart Images
Figure 1.1
Abstract
Description
[0001] Mechanical seal arrangement
[0002] Description
[0003] The invention relates to a gas-lubricated mechanical seal arrangement for sealing a process chamber filled with a non-toxic, gaseous medium from a bearing chamber in which a bearing for supporting a shaft is arranged, as well as to a compressor arrangement.
[0004] Mechanical seal assemblies are known in various designs from the prior art. The so-called tandem design has proven effective for sealing gaseous media. In this design, two mechanical seals are arranged in series on a shaft, and a barrier gas is supplied into a space between the two mechanical seals. The barrier gas is provided by a barrier gas device, which, in addition to the additional structural complexity, also incurs continuous operating costs due to the generation of the barrier gas, which must be supplied at a predetermined pressure. For example, DE 10 2018 208 519 A1 describes a gas-lubricated mechanical seal assembly with a barrier gas device that uses nitrogen as the barrier gas.Recently, however, there has been an increasing demand for applications in which media that are non-toxic to the environment, such as carbon dioxide or nitrogen, have to be sealed. In particular, the compression of carbon dioxide is of primary importance in order to remove it from the ambient air to reduce the greenhouse effect and to compress it, for example, for storage in reservoirs.
[0005] It is therefore an object of the present invention to provide a mechanical seal arrangement which, with a simple structure and simple, cost-effective manufacture, enables sealing of gaseous media which are non-toxic to the environment, in particular CO2 or nitrogen, as well as a compressor arrangement.
[0006] This object is achieved by a mechanical seal assembly having the features of claim 1 and a compressor assembly having the features of claim 10. The subclaims show preferred developments of the invention. The gas-lubricated mechanical seal assembly according to the invention for sealing a process chamber filled with a gaseous, non-toxic medium from a storage chamber, having the features of claim 1, has the advantage that a particularly cost-effective and reliable sealing of the process chamber from a storage chamber in which ambient pressure prevails is possible. In this case, no complex, separate sealing gas device needs to be provided to enable sealing on a rotating component, in particular a shaft. The mechanical seal assembly according to the invention can thus be provided particularly cost-effectively.This is achieved according to the invention in that the mechanical seal arrangement has a first mechanical seal and a second mechanical seal. The first mechanical seal comprises a rotating and a stationary seal ring, which define a first sealing gap between their sliding surfaces. The second mechanical seal comprises a rotating and a stationary seal ring, which define a second sealing gap between their sliding surfaces. Furthermore, the mechanical seal arrangement comprises a first and a second prestressing device. The first prestressing device prestresses the stationary seal ring of the first mechanical seal, and the second prestressing device prestresses the stationary seal ring of the second mechanical seal.A fluid chamber is arranged between the first and second mechanical seals, from which a return line leads in a housing, which is designed to return the gaseous, non-toxic medium to the process area. The fluid chamber is in fluid communication with the first and second sealing gaps and, during operation, absorbs any leakage from the process chamber that escapes via the first sealing gap. The first and second mechanical seals are arranged in series such that a rear side of the stationary seal ring of the first mechanical seal and a rear side of the stationary seal ring of the second mechanical seal are aligned opposite one another. Furthermore, a first step is formed on the inner circumference of the stationary seal ring of the first mechanical seal.Here, a minimum first inner diameter D1 of the stationary seal ring of the first mechanical seal is smaller than a maximum second inner diameter D2 of the stationary seal ring of the first mechanical seal. When the mechanical seal is at rest, the first sealing gap of the first mechanical seal is open so that process gas can flow from the process chamber through the open sealing gap into the fluid chamber between the first and second mechanical seals. Furthermore, a second step is formed on the outer circumference of the stationary seal ring of the second mechanical seal. A minimum first outer diameter D3 of the stationary seal ring of the second mechanical seal is smaller than a maximum second outer diameter D4 of the stationary seal ring of the second mechanical seal. When the mechanical seal arrangement is at rest, the second sealing gap of the second mechanical seal is closed or has very little leakage.Furthermore, a first leakage direction in the first sealing gap of the first mechanical seal runs from the outside from the process chamber to the inside to the fluid chamber and a second leakage direction in the second sealing gap of the second mechanical seal runs from the inside from the fluid chamber to the outside to the bearing chamber.
[0007] Thus, when the mechanical seal arrangement is at rest, in which the rotating component on which the mechanical seal arrangement seals is not rotating, the first sealing gap of the first mechanical seal is open and the second sealing gap of the second mechanical seal is closed. The leaking process medium is returned to the process chamber via the return line from the fluid chamber. When the mechanical seal arrangement is not rotating, the second mechanical seal seals the fluid chamber from the bearing chamber. When the rotatable component to be sealed is rotating, both mechanical seals are in the activated state. There is a first small leakage from the process chamber into the fluid chamber via the first sealing gap, and there is a second small leakage from the fluid chamber via the second sealing gap of the second mechanical seal to the bearing chamber.Thus, no separate sealing medium is required for the operation of the two mechanical seals; instead, the first and second mechanical seals are lubricated by the process medium. A large portion of the leakage through the first sealing gap of the first mechanical seal is returned to the process area via the return line and is therefore not lost. According to the invention, the term "gaseous, non-toxic medium" refers to a medium in the gaseous state or in the supercritical state.
[0008] The mechanical seal arrangement according to the invention also exhibits very good sealing performance even at high speeds, for example, when used on a compressor shaft. By arranging the return line from the fluid chamber located between the first and second mechanical seals to the process area, a large portion of the first leakage can be recovered via the first sealing gap and returned to the process. During operation, the only remaining leakage is the second leakage via the second sealing gap of the second mechanical seal, which, however, is relatively small.
[0009] According to a preferred embodiment of the invention, the rotating seal ring of the first mechanical seal has a plurality of first conveying grooves on the sliding surface. The first conveying grooves are preferably arranged on the outer circumference of the rotating seal ring of the first mechanical seal and preferably extend inward in a crescent shape.
[0010] Further preferably, the stationary seal ring of the second mechanical seal has second conveying grooves. The second conveying grooves are preferably arranged on the inner circumference extending outward and, in particular, extend outward in a crescent shape from the inner circumference of the stationary seal ring of the second mechanical seal. Conveying grooves are preferably provided on all seal rings of the first and second mechanical seals.
[0011] Preferably, a first differential pressure between the process chamber and the fluid chamber is at least three times as great as a second differential pressure between the fluid chamber and the storage chamber. Preferably, the first differential pressure is at least five times as great, in particular at least ten times as great, as the second differential pressure at the second mechanical seal.
[0012] Further preferably, during operation, an amount of the first leakage via the first sealing gap of the first mechanical seal is at least twice as large as an amount of the second leakage via the second sealing gap of the second mechanical seal.
[0013] Preferably, the first and second mechanical seals are arranged on a common sleeve.
[0014] Carbon dioxide or nitrogen is particularly preferred as the process medium. Alternatively, the process medium is a refrigerant, for example, R134a or R245fa.
[0015] Further preferably, the first inner diameter D1 of the stationary seal ring of the first mechanical seal lies in a range defined by the following inequality:
[0016] 0.8 x D2 < D1 < D2, where D2 is the maximum second inner diameter, and in particular D1 is in the range 0.9 x D2 < D1 < D2.
[0017] Thus, the first inner diameter D1 lies in a range which is a maximum of 20% smaller than the second inner diameter D2 of the stationary seal ring.
[0018] More preferably, the first outer diameter D3 of the stationary seal ring of the second mechanical seal lies in a range defined by the following inequality:
[0019] 0.8 x D4 < D3 < D4, where D4 is the maximum second outer diameter, and in particular D3 is in the range 0.9 x D4 < D3 < D4.
[0020] This means that the first outer diameter D3 lies in a range between 80% of the second outer diameter D4 of the second mechanical seal and the outer diameter D4. This allows, in particular, the closing forces acting on the second mechanical seal to be designed.
[0021] Furthermore, the present invention relates to a compressor arrangement for compressing a gaseous medium, comprising a compressor and a mechanical seal arrangement according to the invention. A preferred embodiment of the invention is described in detail below with reference to the accompanying drawing. In the drawing:
[0022] Fig. 1 is a schematic sectional view of a mechanical seal arrangement according to a preferred embodiment of the invention,
[0023] Fig. 2 is a schematic plan view of a sliding surface of a rotating seal ring of a first mechanical seal,
[0024] Fig. 3 is a schematic plan view of a sliding surface of a stationary seal ring of the first mechanical seal,
[0025] Fig. 4 is a schematic plan view of a sliding surface of a rotating seal ring of a second mechanical seal and
[0026] Fig. 5 is a schematic plan view of a sliding surface of a stationary seal ring of the second mechanical seal.
[0027] A mechanical seal arrangement 1 according to a preferred embodiment of the invention is described in detail below with reference to Figures 1 to 5.
[0028] The mechanical seal assembly 1 seals a process chamber 6 from a bearing chamber 8. A bearing 80 is arranged in the bearing chamber 8, on which a shaft 18 is mounted.
[0029] The mechanical seal assembly 1 comprises two mechanical seals, namely a first mechanical seal 2 and a second mechanical seal 3. The two mechanical seals 2, 3 are arranged in series to seal the process chamber 6 from the storage chamber 8. This is a so-called double seal.
[0030] In process chamber 6, a gaseous medium that is non-toxic to the environment, for example carbon dioxide (CO2) or nitrogen, is present.
[0031] The first mechanical seal 2 comprises a rotating seal ring 20 with a first sliding surface 20a and a stationary seal ring 21 with a second sliding surface 21a. A first sealing gap 22 is defined between the two sliding surfaces 20a, 21a. The rotating seal ring 20 is set in rotation by means of a first driver element 23.
[0032] The second mechanical seal 3 comprises a rotating seal ring 30 with a third sliding surface 30a and a stationary seal ring 31 with a fourth sliding surface 31a. A second sealing gap 32 is defined between the two sliding surfaces 30a, 31a. The rotating seal ring 30 of the second mechanical seal 3 is set in rotation by a second driver element 33. The first mechanical seal 2 and the second mechanical seal 3 are arranged on a common sleeve 11, which is fixed to the shaft 18. The seal rings are designed without through holes.
[0033] As can be further seen from Fig. 1, the arrangement of the first mechanical seal 2 and the second mechanical seal 3 is such that a rear side 21b of the stationary seal ring 21 of the first mechanical seal 2 is directed toward a rear side 31b of the stationary seal ring 31 of the second mechanical seal 3. The stationary seal ring 21 of the first mechanical seal 2 and the stationary seal ring 31 of the second mechanical seal 3 are fixed to a housing 15.
[0034] The stationary seal ring 21 of the first mechanical seal 2 is preloaded in the axial direction XX of the mechanical seal assembly 1 by a first preloading device 4. The stationary seal ring 31 of the second mechanical seal 3 is preloaded in the axial direction XX by a second preloading device 5. In this exemplary embodiment, the preloading devices are a plurality of cylindrical springs arranged along the circumference on the rear sides of the stationary seal rings 21, 31.
[0035] As can be further seen from Fig. 1, a fluid chamber 7 is formed between the first mechanical seal 2 and the second mechanical seal 3. A return line 9 leads from the fluid chamber 7 back to a compressor 10, which is schematically indicated in Fig. 1. Fluid can thus be returned to the compressor 10 via the return line 9 in the direction of the process area.
[0036] As can be seen from Figs. 2 and 3, a plurality of first conveying grooves 12 are provided in the rotating seal ring 20 of the first mechanical seal 2. The first conveying grooves 12 extend inward in a crescent shape from an outer circumference of the rotating seal ring 20. No grooves are formed in the sliding surface 21a of the stationary seal ring 21.
[0037] As can also be seen from Figs. 4 and 5, no conveying grooves are formed in the rotating seal ring 30 of the second mechanical seal 3. However, second conveying grooves 13 are formed in the stationary seal ring 31. The second conveying grooves 13 extend outwardly in a crescent shape from an inner circumference of the stationary seal ring 31.
[0038] Thus, in the first mechanical seal 2, a conveying direction across the first sealing gap 22 is from radially outside to radially inside. This is indicated in Fig. 1 by a first leakage direction 16 (arrow). In the second mechanical seal 3, a second leakage direction 17 is from radially inside to radially outside, since the second conveying grooves 13 define a conveying direction in the radially outward direction. As can also be seen from Fig. 1, the stationary seal ring 21 of the first mechanical seal has a first step 41 on the inner circumference. A minimum first inner diameter D1 of the stationary seal ring 21 of the first mechanical seal 2 is smaller than a maximum second inner diameter D2 of the stationary seal ring 21 of the first mechanical seal 2. This ensures that when the shaft 18 is not rotating, i.e. when the compressor 10 is not in operation, the first sealing gap 22 remains open.
[0039] In the second mechanical seal 3, a second step 42 is formed on the outer circumference of the stationary slide ring 31 of the second mechanical seal 3. A minimum first outer diameter D3 of the stationary slide ring 31 is smaller than a maximum second outer diameter D4 of the stationary slide ring 31 of the second mechanical seal 3. With the support of the spring force of the second pretensioning device 5, it is ensured that when the compressor 10 is at a standstill, i.e. when the shaft 18 is not rotating, the second sealing gap 32 is closed or almost closed. This means that the two sliding surfaces 30a, 31a are in contact with one another and seal the second mechanical seal 3 completely or almost completely, so that little or no fluid can flow from the fluid chamber 7 towards the bearing chamber 8.
[0040] During operation of the mechanical seal assembly 1 with the rotating shaft 18, leakage occurs via the first sealing gap 23 from the process chamber 6 into the fluid chamber 7 and from the fluid chamber 7 into the bearing chamber 8. As can be seen from Fig. 1, the flow directions through the first sealing gap 22 and the second sealing gap 32 are radially opposite. This means that the flow direction through the first sealing gap 22 is radially inward (arrow 16), while the flow direction in the second sealing gap 32 is radially outward during operation (arrow 17).
[0041] Thus, the first and second mechanical seals 2, 3 seal in the usual way during operation of the compressor 10, although the leakage quantities across the sealing gaps of the first and second mechanical seals 2, 3 are different. The leakage quantity across the first sealing gap 22 of the first mechanical seal 2 is much greater than the leakage quantity across the second sealing gap 32 of the second mechanical seal 3. Furthermore, leakage that passes from the process chamber 6 into the fluid chamber 7 via the first sealing gap 22 is returned to the compressor 10 via the return line 9. The arrows 19 in Fig. 1 illustrate the return flow direction from the fluid chamber 7 towards the process area to the compressor 10. Thus, a large amount of the leakage can be recovered via the first mechanical seal 2 and reintroduced into the compressor 10 at a corresponding point, which corresponds to the pressure level of the returned gaseous process medium.The leakage from the fluid chamber 7 into the bearing chamber 8 via the second sealing gap 32 of the second mechanical seal 3 can be easily released into the environment, since the process medium is a gas that is non-toxic to the environment.
[0042] Thus, the mechanical seal assembly 1 according to the invention also uses the process medium as a barrier medium for the first and second mechanical seals 2, 3. This eliminates the need for a separate barrier fluid device, which is typically required for mechanical seals to provide the barrier medium for the mechanical seals. This significantly reduces the cost of the mechanical seal assembly 1.
[0043] The invention thus provides a self-sufficient bearing seal that seals the process chamber 6 from the bearing chamber 8. During operation of the mechanical seal assembly 1, the process medium thus provides the barrier fluid in both mechanical seals 2, 3. When the mechanical seal assembly 1 is stationary, the first sealing gap 22 of the first mechanical seal 2 is open, and the second sealing gap 32 of the second mechanical seal 3 is closed or substantially closed by the spring forces of the second preloading device 5 and the diameter difference between the first outer diameter D3 and the second outer diameter D4 on the stationary seal ring 31. This prevents the process medium that has leaked into the fluid chamber 7 via the first sealing gap 22 from escaping into the bearing chamber 8, or only minimal leakage occurs from the fluid chamber 7 toward the bearing chamber 8.
[0044] The second leakage direction 17 of the second mechanical seal 3 from radially inside to radially outside also prevents oil from the bearing chamber 8, which is necessary for the lubrication of the bearing 80, from entering the fluid chamber 7.
[0045] Thus, the present invention provides a highly cost-effective mechanical seal assembly 1 for bearing sealing, which completely eliminates the need for a supply unit for the sealing medium. The process medium to be sealed is used as the sealing medium in both mechanical seals. Leakage of the process medium during operation via the second sealing gap 32 is uncritical, since the process medium can be an environmentally non-toxic gas such as carbon dioxide or nitrogen, or even a refrigerant such as R134a or R245.
[0046] The back-to-back arrangement of the two rear sides 21b, 31b of the two stationary seal rings 21, 31 further enables a particularly compact design. The return line 19 runs between the first and second mechanical seals 2, 3 (see Fig. 1). Furthermore, the mechanical seal arrangement 1 according to the invention also eliminates the need for any additional labyrinth seals, lip seals, or the like. Furthermore, the design of all seal rings of the first and second mechanical seals 2, 3 can be made without through holes or the like. This allows for a significant cost advantage, particularly in the manufacture of the mechanical seals 2, 3.
[0047] In addition to the above written description of the invention, reference is hereby explicitly made to the graphic representation of the invention in Figs. 1 to 5 for its supplementary disclosure.
[0048] List of reference symbols
[0049] 1 mechanical seal arrangement
[0050] 2 first mechanical seal
[0051] 3 second mechanical seal
[0052] 4 first pre-tensioning device
[0053] 5 second pretensioning device
[0054] 6 Process room
[0055] 7 Fluid chamber
[0056] 8 storage rooms
[0057] 9 Return line
[0058] 10 compressors
[0059] 11 sleeve
[0060] 12 first conveyor grooves
[0061] 13 second conveying grooves
[0062] 15 housings
[0063] 16 first leak direction
[0064] 17 second leak direction
[0065] 18 Wave
[0066] 19 Return flow direction
[0067] 20 rotating slide ring
[0068] 20a first sliding surface
[0069] 21 stationary sliding ring
[0070] 21a second sliding surface
[0071] 21 b Back of the stationary sliding ring 21
[0072] 22 first sealing gap
[0073] 23 first driver element
[0074] 30 rotating slide ring
[0075] 30a third sliding surface
[0076] 31 stationary sliding ring
[0077] 31a fourth sliding surface
[0078] 31b Back of the stationary sliding ring 31
[0079] 32 second sealing gap
[0080] 33 second driver element
[0081] 41 first stage
[0082] 42 second stage
[0083] 80 warehouses
[0084] D1 minimum first inner diameter of the stationary seal ring 21 D2 maximum second inner diameter of the stationary seal ring 21
[0085] D3 minimum first outer diameter of the stationary seal ring 31
[0086] D4 maximum second outer diameter of the stationary seal ring 31
[0087] XX Axial direction
Claims
Claims 1. Mechanical seal arrangement for sealing a process chamber (6) filled with a non-toxic, gaseous process medium from a storage chamber (8), comprising: - a first mechanical seal (2) with a rotating sliding ring (20) with a first sliding surface (20a) and a stationary sliding ring (21) with a second sliding surface (21a), which define a first sealing gap (22) between the sliding surfaces (20a, 21a), - a second mechanical seal (3) with a rotating sliding ring (30) with a third sliding surface (30a) and a stationary sliding ring (31) with a fourth sliding surface (31a), which define a second sealing gap (32) between the sliding surfaces (30a, 31a), - a first preloading device (4) which preloads the stationary sliding ring (21) of the first mechanical seal (2) in the axial direction (XX), - a second preloading device (5) which preloads the stationary sliding ring (31) of the second mechanical seal (3) in the axial direction (XX), - a fluid chamber (7) arranged between the first mechanical seal (2) and the second mechanical seal (3), which is in fluid communication with the first and second sealing gaps and, in operation, receives leakage via the first sealing gap (22) from the process chamber (6), and from which a return line (9) leads, designed for returning process medium from the fluid chamber (7) to a process area, - wherein the first mechanical seal (2) and the second mechanical seal (3) are arranged such that a rear side (21b) of the stationary sliding ring (21) of the first mechanical seal (2) and a rear side (31b) of the stationary sliding ring (31) of the second mechanical seal (3) are facing opposite each other, - wherein the stationary sliding ring (21) of the first mechanical seal (2) forms a first stage (41) on the inner circumference, such that a minimum first inner diameter D1 of the stationary sliding ring (21) of the first mechanical seal (2) is smaller than a maximum second inner diameter D2 of the stationary sliding ring (21) of the first mechanical seal (2), - wherein the stationary sliding ring (31) of the second mechanical seal (3) forms a second stage (42) on the outer circumference, such that a minimum first outer diameter D3 of the stationary sliding ring (31) of the second mechanical seal (3) is smaller than a maximum second outer diameter D4 of the stationary sliding ring (31) of the second mechanical seal (3), - wherein in the rest state of the mechanical seal arrangement the first sealing gap (22) of the first mechanical seal (2) is open, so that process medium can flow from the process chamber (6) through the open first sealing gap (22) into the fluid chamber (7) and wherein the second sealing gap (32) of the second mechanical seal (3) is closed, and - wherein a first leakage direction (16) in the first sealing gap (22) extends from the outside of the process chamber (6) inwards to the fluid chamber (7), and a second leakage direction (17) in the second sealing gap (32) extends from the inside of the fluid chamber (7) outwards to the storage chamber (8). Mechanical seal arrangement according to claim 1, wherein the rotating sliding ring (20) of the first mechanical seal (2) has first conveying grooves (12). Mechanical seal arrangement according to claim 2, wherein the first conveying grooves (12) extend inwards from the outer circumference of the rotating sliding ring (20) of the first mechanical seal (2). Mechanical seal arrangement according to any one of the preceding claims, wherein the stationary sliding ring (31) of the second mechanical seal (3) has second conveying grooves (13). Mechanical seal arrangement according to claim 4, wherein the second conveying grooves (13) extend outwards from the inner circumference of the stationary sliding ring (31) of the second mechanical seal (3).Mechanical seal arrangement according to any one of the preceding claims, wherein a first differential pressure between the process chamber (6) and the fluid chamber (7) is at least three times greater than a second differential pressure between the fluid chamber (7) and the storage chamber (8). Mechanical seal arrangement according to any one of the preceding claims, wherein a leakage rate of the process medium through the first sealing gap (22) of the first mechanical seal (2) is at least twice as great as a leakage rate of the process medium from the fluid chamber (7) through the second sealing gap (32) of the second mechanical seal (3) to the storage chamber (8).
8. Mechanical seal arrangement according to one of the preceding claims, wherein the first mechanical seal (2) and the second mechanical seal (3) are arranged on a common sleeve (11).
9. Mechanical seal arrangement according to one of the preceding claims, wherein carbon dioxide or nitrogen or a refrigerant is present as the gaseous process medium in the process chamber (6) and the mechanical seal arrangement is configured to seal the process chamber (6) against the storage chamber (8).
10. Mechanical seal arrangement according to one of the preceding claims, wherein the first inner diameter D1 of the stationary sliding ring (21) of the first mechanical seal (2) is in a region of 0.8 x D2 < D1 < D2, and / or wherein the first outer diameter D3 of the stationary sliding ring (31) of the second mechanical seal (3) is in a range of 0.8 x D4 < D3 < D4 lies.
11. Compressor arrangement for compressing a gaseous process medium comprising a compressor (10) and a mechanical seal arrangement according to one of the preceding claims, in order to seal a process chamber (6) against a storage chamber (8) with a bearing (80) which supports a shaft (18) of the compressor (10).