Conical seal assembly for rotary equipment and rotary equipment including the seal assembly - Patents.com

Abstract

The shaft seal assembly (1) includes a rotary seal member (31) adapted to be drivingly coupled to a rotating shaft (5) of a rotary device, and a stationary porous seal member (41) adapted to be coupled to a stationary housing of the rotary device and extending around the rotary seal member (31). The shaft seal assembly further includes at least one seal gas inlet port (55) adapted to communicate pressurized seal gas to the stationary porous seal member (41). The rotary seal member (31) has a conical outer seal surface (35), and the stationary porous seal member (41) has a conical inner seal surface (43). The conical inner seal surface (43) faces the conical outer seal surface (35).

Description

[Technical Field]

[0001] Disclosed herein is a seal for rotating equipment such as, but not limited to, turbomachinery. assembly is. [Background technology]

[0002] Turbomachinery, such as, but not limited to, centrifugal and axial compressors, requires rotating seals to prevent or limit fluid leakage towards bearings or the environment.

[0003] A variety of shaft sealing devices have been developed for this purpose, including labyrinth seals, oil-filled seals, mechanical contact seals, and dry gas seals.

[0004] Dry gas seals include a stationary ring and a rotating ring adapted to rotate integrally with the shaft. A dry seal gas, typically the same process gas that flows through the rotating equipment, is injected into the seal to provide a barrier against gas leakage. The majority of the dry seal gas flows across the inner labyrinth seal back into the machine, and a small portion of the dry seal gas flows from the dry gas seal as a primary or secondary vent and is either recovered or flared.

[0005] While providing excellent sealing properties, dry gas seals are not without drawbacks, such as the need to provide seal gas even while the rotating equipment is idle. Furthermore, the flow rate of the exhausted seal gas is relatively high, which can result in serious environmental impacts or loss of valuable gas components if the exhausted seal gas is not recovered.

[0006] Attempts have been made to overcome these drawbacks by using a stationary porous seal member cooperating with a rotating seal member. A pressurized seal gas is supplied to the porous seal member and migrates across the porous seal member toward the interface between the stationary and rotating seal members. These seal assemblies using porous seal members have several drawbacks. In particular, they suffer from a relatively high leakage rate due to the short length of the leakage flow path. Summary of the Invention [Problem to be solved by the invention]

[0007] It would therefore be desirable to provide a seal assembly that uses a porous seal member that overcomes or mitigates at least some of the disadvantages and limitations of prior art seal assemblies.

[0008] A shaft seal assembly is disclosed that is configured to sealingly separate high-pressure and low-pressure regions of a rotary piece of equipment, such as a compressor or another turbomachine. As used herein, the term "rotary equipment" may encompass any machine having an outer casing and a shaft supported for rotation within the casing. The shaft seal assembly includes a rotary seal member adapted to be drivingly coupled to the rotary shaft for rotation therewith, and a stationary porous seal member adapted to be coupled to a stationary housing of the rotary equipment and extending around the rotary seal member. The shaft seal assembly further includes at least one seal gas inlet port adapted to deliver pressurized seal gas to the stationary porous seal member. The rotary seal member has a conical outer seal surface (i.e., a convex conical seal surface), and the stationary porous seal member has a conical inner seal surface (i.e., a concave conical seal surface). The conical inner seal surface faces the conical outer seal surface.

[0009] In a presently preferred embodiment disclosed herein, the conical outer and inner sealing surfaces each have a respective first end adapted to face the high pressure region and a second end adapted to face the low pressure region when the shaft seal assembly is installed in the rotating equipment, each of the first ends having a larger diameter than the corresponding second end.

[0010] Further features and embodiments of the seal assembly are described below and set forth in the accompanying claims.

[0011] According to a further aspect, disclosed herein is a rotary machine, such as a turbomachine, in which a high pressure region and a low pressure region are sealingly separated from one another. At least one or more of the shaft seal assemblies outlined above may be disposed along a rotating shaft between the high pressure region and the low pressure region. [Brief explanation of the drawings]

[0012] Reference will now be made briefly to the accompanying drawings, in which: [Figure 1] FIG. 1 is a schematic diagram of a turbomachine including a shaft seal assembly according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of a shaft seal assembly according to one embodiment of the present disclosure. [Figure 3] FIG. 3 is a cross-sectional view of a shaft seal assembly according to the present disclosure in a further embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following description relates specifically to turbomachines, and more specifically to dynamic compressors such as axial or centrifugal compressors and pumps. However, it should be understood that the novel features of the present disclosure may be advantageously used to provide efficient shaft seals in other types of rotating equipment, such as turbines, expanders, and other rotary machines, where a high pressure side or region and a low pressure side or region are sealingly separated from one another.

[0014] A novel seal assembly for use in rotating equipment has a rotating conical surface cooperating with a stationary, i.e., non-rotating, conical surface to provide an efficient seal along the rotating shaft of a turbomachine. The stationary conical surface surrounds the rotating conical surface. The stationary conical surface is formed in a porous medium through which pressurized sealing gas can flow. A gap or space between the stationary conical surface and the rotating conical surface is formed under the combined action of the pressurized sealing gas and an elastic axial force applied to the stationary conical surface.

[0015] By "axial force" is understood a force directed in the direction of the geometric axis of the fixed and rotating conical surfaces, the axis substantially coinciding with the axis of rotation of the shaft on which the seal assembly is mounted.

[0016] The elastic axial force is oriented to urge the fixed conical surface against the rotating conical surface in the direction of the axis of rotation of the turbomachine rotating shaft, thereby effectively separating the high and low pressure regions with minimal seal gas flow.

[0017] Referring now to the drawings, Figure 1 illustrates schematically a turbomachine 1, e.g., a centrifugal compressor, including a casing 3 and a rotatable shaft 5 supported for rotation within the casing 3. An impeller 7 rotates with the rotatable shaft 5 about its axis of rotation AA. Process gas flows to the compressor 1 through a suction side 9 that is fluidly coupled to an inlet line 10. The pressurized process gas is delivered by the compressor 1 at a delivery side 11 and flows in an outlet line 12.

[0018] The rotating shaft 5 is supported by bearings shown schematically at 13 and 15. Seal assemblies 17 and 19 are positioned along the rotating shaft 5 inside the bearings 13 and 15 to prevent process gas from leaking along the rotating shaft 5 and through the bearings 13 and 15 towards the environment. In a further embodiment not shown, additional seal assemblies may be positioned between adjacent compressor stages within the casing 3.

[0019] 2 illustrates one embodiment of the presently disclosed seal assembly 17. Seal assembly 19 may be configured substantially similarly to seal assembly 17.

[0020] Generally speaking, the seal assembly 17 is disposed between the high pressure region HP and the low pressure region LP, for example, between the most upstream compressor stage and bearing 13 or between the most downstream compressor stage and bearing 15.

[0021] In each embodiment, the seal assembly 17 includes a rotary seal member 31 constrained, i.e., connected, to the rotary shaft 5 for rotation therewith and to prevent axial displacement of the rotary seal member 31 along the shaft 5. Here, "constrained to the rotary shaft" means that the rotary seal member 31 rotates integrally with the shaft 5. The rotary seal member 31 can be connected, i.e., secured, to the rotary shaft 5 by any suitable method, such as welding, a slip fit, a friction fit, adhesives, etc. In other embodiments, the rotary seal member 31 can be connected to the rotary shaft 5 by screws, pins, clamps, keys, tabs, splined profiles, etc. As a non-limiting example, in FIG. 2 , the mechanical connection between the rotary shaft 5 and the rotary seal member 31 is represented schematically by a screw 33.

[0022] The rotary seal member 31 includes a shaft sleeve having a cylindrical through-bore for the rotary shaft 5 and a conical outer surface 35, i.e., a conical male surface. The conical outer surface 35 is coaxial with the shaft 5, i.e., its axis coincides with the axis of rotation AA of the rotary shaft 5 and the compressor rotor. The conical outer surface 35 surrounds an inner cylindrical surface 36 of the rotary seal member 31. One or more stationary seal members, such as O-rings 37, may be positioned between the inner cylindrical surface 36 and the rotary shaft 5.

[0023] The conical outer surface 35 of the rotary seal member 31 extends from a first end facing the high-pressure region HP to a second end facing the low-pressure region LP. The conical outer surface 35 has a circular cross-section with a variable diameter. The first end facing the high-pressure region HP has a larger diameter than the second end; i.e., the ideal apex of the conical outer surface 35 is located opposite the high-pressure region HP. In other, currently less preferred, embodiments, the positions of the conical outer surface 35 relative to the high-pressure and low-pressure regions may be reversed; i.e., the larger diameter end of the conical outer surface 35 may face the low-pressure region and the smaller diameter end of the conical outer surface 35 may face the high-pressure region.

[0024] The seal assembly 17 further includes a stationary porous seal member 41 that is substantially coaxial with the rotary seal member 31. As understood herein, "substantially coaxial" means that the stationary porous seal member 41 and the rotary seal member 31 are coaxial within acceptable mechanical tolerances, which may vary depending on the particular application. Generally speaking, the relative positions of the geometric axes of the conical surfaces of the rotary seal member 31 and the stationary porous seal member 41 may deviate from strict coaxiality with respect to both eccentricity and mutual tilt. The eccentricity of the two axes may be within a range of 0% to 5% of the maximum diameter of the opposing conical surfaces. The parallelism error, i.e., angular offset, may be, for example, 0° to 5°, preferably 0° to 2° or less.

[0025] As used herein, the term "fixed" means that the fixed porous seal member 41 does not rotate with the rotating shaft 5 about the rotation axis AA. However, the fixed porous seal member 41 may oscillate or rock about a fixed position. For example, the fixed porous seal member 41 may have a limited angular displacement within a range of 0° to 2° or less due to mechanical tolerances.

[0026] Furthermore, the stationary porous sealing member 41 is capable of limited displacement in the axial direction, i.e., parallel to the axis of rotation AA of the rotating shaft 5. The axial displacement may be caused by thermal expansion of the turbomachine. The displacement may range, for example, from 0 to 20 mm, but generally depends on the axial length of the turbomachine.

[0027] Furthermore, as will be explained in more detail below, the stationary porous seal member 41 is adapted to move slightly relative to the rotary seal member 31 in the direction of the rotational axis AA of the rotary shaft 5 to form a gap between the conical inner surface of the stationary porous seal member 41 and the conical outer surface 35 of the rotary seal member 31 to prevent mutual contact therebetween when the rotary shaft 5 is rotating. This mutual displacement between the opposing conical surfaces may be in the range of 1 micrometer to 1000 micrometers or less, for example 1 micrometer to 500 micrometers or less, preferably less than 300 micrometers, and even more preferably less than 200 micrometers.

[0028] The stationary porous seal member 41 can include a body of porous material made, for example, of a sintered material. In embodiments, the sintered material can be selected from carbon, graphite, alumina, tungsten carbide, etc. In other embodiments, the body of porous material can be manufactured by additive manufacturing with an appropriate porous structure.

[0029] In the embodiment of Figure 2, the stationary porous seal member 41 is formed entirely of a porous material, however in other embodiments not shown, for example when the stationary porous seal member 41 is manufactured by additive manufacturing, the stationary porous seal member 41 may include porous and non-porous regions.

[0030] In this specification and the appended claims, the term "porous" in reference to the stationary porous seal member 41 means that a seal gas injected into the seal will move through the stationary seal member 41 under a pressure differential.

[0031] 2, the stationary porous seal member 41 includes a conical female surface 43, i.e., a conical inner surface 43. The conical inner surface 43 surrounds the conical outer surface 35 of the rotary seal member 31, i.e., extends around the rotary seal member 31, and is substantially coaxial with the rotary seal member 31 in the sense defined above. In use, a gap 45 is formed between the conical inner surface 43 and the conical outer surface 35, as described below.

[0032] The conical inner surface 43 of the stationary porous seal member 41 extends from a first end facing the high pressure region HP to a second end facing the low pressure region LP. The conical inner surface 43 has a circular cross-section with a variable diameter, the first end having a larger diameter than the second end, i.e., the ideal apex of the conical inner surface 43 is located opposite the high pressure region HP. In another, currently less preferred embodiment, the larger diameter end of the conical inner surface 43 faces the low pressure region HP and the smaller diameter end of the conical inner surface 43 faces the high pressure region HP.

[0033] In the embodiment of FIG. 2, the stationary porous seal member 41 is housed within an annular housing 47 that surrounds the stationary porous seal member 41 and the rotary seal member 31. The stationary porous seal member 41 has an exterior surface in sealing contact with the annular housing 47. In the embodiment of FIG. 2, the exterior surface of the stationary porous seal member 41 includes a major cylindrical outer surface 49 coaxial with the conical inner surface 43 and two end planar surfaces 51, 53. The major cylindrical outer surface 49 and the end planar surfaces 51, 53 are in sealing contact with the inner surface of the annular housing 47. In this manner, pressurized seal gas delivered to the stationary porous seal member 41 is prevented from leaking through the side surfaces 49, 51, 53.

[0034] The annular housing 47 includes at least one seal gas inlet port 55. In a preferred embodiment, the multiple seal gas inlet ports 55 are distributed annularly around the rotational axis AA of the rotating shaft 5. In a preferred embodiment, the seal gas inlet ports 55 are distributed at a constant angular pitch around the rotational axis AA. The seal gas inlet port 55 is located adjacent to or near the end of the fixed porous seal member 41 facing the high-pressure side and opposite the end of the conical inner surface 43 facing the low-pressure side.

[0035] In the illustrated embodiment, the fixed porous sealing member 41 is resiliently biased axially, i.e., in the direction of the geometric axis of the conical surfaces 35, 43, such that the conical inner surface 43 is pressed against the conical outer surface 35.

[0036] In some embodiments, a resilient member presses the stationary porous seal member 41 against the rotary seal member 31. In each embodiment, the resilient member can include one or more resilient elements, such as compression springs. In FIG. 2, the resilient member includes a plurality of compression springs 57 arranged about the axis AA. In the embodiment of FIG. 2, the springs 57 are disposed between the annular housing 47 and a ring casing 59 in which the annular housing 47 is disposed. The ring casing 59 can be rigidly mounted within the casing 5 of the compressor 1.

[0037] As shown in FIG. 2 , the axial extension of the annular housing 47 is less than the axial length of an inner seat 61 formed within a ring casing 59 in which the annular housing 47 is slidably received. In this manner, sufficient axial clearance exists between the annular housing 47 and the ring casing 49 to allow the annular housing 47 to move axially, i.e., toward the rotational axis AA of the rotatable shaft 5. In a non-operating state, when pressurized sealing gas is not delivered to the seal assembly 17, the spring 57 urges the stationary porous seal member 41 to a rest position abutting the rotary seal member 31. In the rest position, the conical inner surface 43 contacts the conical outer surface 35.

[0038] The radial dimension of ring casing 59 is such that a radial clearance is provided between annular housing 47 and ring casing 59 as shown at 62 .

[0039] Balancing gaskets 63, 65 are disposed between the annular housing 47 and the ring casing 59. The gaskets 63, 65 allow some axial and radial displacement of the annular housing 47 inside the seat 61 of the ring casing 59.

[0040] At least one aperture 67 in the ring casing 59 is fluidly coupled, directly or indirectly, to a source of pressurized seal gas and is adapted to deliver the pressurized seal gas toward the seal gas inlet port 55. The source of pressurized seal gas may be any source of sufficiently clean gas at a pressure higher than the pressure in the high pressure region HP. In some embodiments, the pressurized seal gas may be process gas diverted from the delivery side of the compressor 1 and suitably pre-treated, for example, in a pre-treatment unit 71, as shown schematically in FIG. 1. In other embodiments, a dedicated seal gas source, for example a nitrogen source, may be foreseen for this purpose.

[0041] In use, pressurized seal gas is delivered through aperture 67 in ring casing 59 and forced into seal gas inlet port 55. The porous structure of stationary porous seal member 41 allows the pressurized seal gas to migrate therethrough and leak past inner conical surface 43. The seal gas pressure generates a hydrostatic lift force with an axial component that opposes the elastic force of spring 57. This hydrostatic lift force is sufficient to displace stationary porous seal member 41 relative to rotary seal member 31 in the direction of rotation axis AA. The axial displacement forms gap 45 between inner conical surface 43 and outer conical surface 35. The size of conical gap 45 is determined by a balance between the hydrostatic force generated by the pressurized seal gas, the axial thrust exerted by elastic member 57, and the force acting on axially displaceable stationary porous seal member 41 resulting from the pressure differential between high-pressure zone HP and low-pressure zone LP.

[0042] The axial clearance of ring casing 59 allows axial housing 47 to move axially against the elastic thrust of elastic member 57. Gaskets 63 and 65 prevent gas leakage between ring casing 59 and annular housing 47, thus allowing stationary porous seal member 41 to "float" on rotary seal member 31 due to the hydrostatic thrust generated by pressurized seal gas moving through the porous structure of stationary porous seal member 41.

[0043] The porous structure of the stationary porous seal member 41 gradually reduces the pressure of the pressurized seal gas moving through the porous structure from the seal gas inlet port 55 toward the conical inner surface 43. Figure 2 shows isobars representing the pressure change of the seal gas within the porous structure of the stationary porous seal member 41. The pressure decreases from the first end (facing the high-pressure region HP) of the conical inner surface 43 and the conical outer surface 35 toward the second end (facing the low-pressure region LP). Some of the seal gas that escapes through the gap 45 leaks into the high-pressure region HP, i.e., the interior of the compressor 1, while the remainder flows toward the low-pressure side. A vent (not shown) may be provided to collect the seal gas escaping toward the low-pressure region and prevent the decompressed seal gas from dispersing toward the environment. In some embodiments, an additional seal may be positioned between the seal assembly 17 and the outboard bearing 13, and separation gas may be delivered between the seal assembly 17 and the outboard bearing 13 to prevent the seal gas from contacting the bearing 13.

[0044] When the compressor 1 is at rest, pressurized sealing gas is not required through the seal assemblies 17, 19, thereby avoiding the need for continuous sealing gas delivery as otherwise required by current technology dry gas seals. This is achieved by the multiplication effect of the contact pressure between the two mating members 31 and 41 due to the slope of the conical inner surface 43 and the conical outer surface 35.

[0045] The axial and radial clearances around the annular housing 47 compensate for wear of the porous material forming the stationary porous seal member 41. Additionally, the axial and radial clearances allow for axial and radial displacement of the seal assembly that may be caused by radial and axial displacement of the rotating shaft 5 due to, for example, thermal expansion.

[0046] In the embodiment of Figure 2, axial and radial displacement of the annular housing 47 and the stationary porous seal member 41 housed therein is permitted by the ability of the gaskets 63, 65 to deform. However, if greater radial and axial displacement of the stationary porous seal member 41 is necessary or desired, separate gaskets adapted to permit radial and axial movement may be used. An embodiment of a seal assembly that may permit greater radial and axial displacement is shown in Figure 3. Like reference numerals indicate parts corresponding to those in Figure 2, and these parts will not be described again in detail.

[0047] In the embodiment of FIG. 3, the stationary porous sealing member 41 is rigidly constrained within the annular housing 47 in a manner similar to that of FIG. 2. Unlike the embodiment of FIG. 2, in FIG. 3 an intermediate annular component 75 is provided between the ring casing 59 and the annular housing 47, with the stationary porous sealing member 41 housed therein. The annular housing 47 is disposed on the intermediate annular component 75 with a radial clearance. Annular balance gaskets 77, 79 seal the gap between the annular housing 47 and the intermediate annular component 75 and allow radial displacement of the annular housing 47 inside the intermediate annular component 75 to compensate for radial movement of the rotating shaft 5.

[0048] The intermediate annular component 75 is housed in the seat 61 formed by the ring casing 59 with an axial clearance, i.e., a space that allows the unit including the fixed porous sealing member 41, the annular housing 47, and the intermediate annular component 75 to be displaced in the direction of the rotation axis AA of the rotating shaft 5. Annular balance gasket 77、79 allows axial displacement between intermediate annular component 75 and ring casing 59 to seal the gap therebetween. Thus, stationary porous seal member 41 can be lifted from rotary seal member 31 by the hydrostatic thrust generated by pressurized seal gas injected into the seal assembly through apertures 67A and 67B, and the gas travels through the porous structure of stationary porous seal member 41.

[0049] Apertures 67A and 67B in ring casing 59 and intermediate annular component 75 supply pressurized seal gas to seal gas inlet port 55. As mentioned above, the seal gas may be pressurized process gas diverted from the delivery side of compressor 1. Alternatively or additionally, a separate source of pressurized seal gas may be envisioned.

[0050] The sealing gas moving through the porous structure of the stationary porous seal member 41 generates a hydrostatic thrust sufficient to displace the stationary porous seal member 41 and the rotary seal member 31 relative to one another in the direction of the rotational axis AA of the shaft 5, thereby forming the gap 45. As with the embodiment of Figure 2 described above, the amount of thrust required to lift the stationary porous seal member 41 from the rotary seal member 31 depends on the pressure differential across the seal assembly and the total biasing force applied by the resilient members 57 (e.g., spings 57).

[0051] By providing separate sets of gaskets 77, 79 and 81, 83, greater axial and radial displacement of the stationary porous seal member 41 relative to the rotary seal member 31 is possible.

[0052] Some or all of the surfaces of the seal assembly described above may be hardened to reduce wear of the mechanically contacting surfaces. In some embodiments, the conical outer surface 35 of the rotary seal member 31 and / or the conical inner surface 43 of the stationary porous seal member 41 may be hardened. Additionally or alternatively, some surfaces or surface portions of the seal assembly members that are in sliding contact with one another may be hardened, such as in the areas labeled 87 and 89 in FIG. 3 . In some embodiments, hardnesses of greater than 30 HRC, preferably greater than 70 HRC, or even higher may be envisioned. Any known hardening technique adapted to achieve the desired hardness value may be used. For example, suitable hardening techniques include nitriding, tungsten / chromium carbide coating, etc.

[0053] In some embodiments, non-resilient features may be positioned between adjacent components that allow for mutual radial displacement, for example, due to vibrations induced by rotation of compressor 1. For example, a non-resilient feature, such as a non-resilient coating 91, may be disposed between the outer surface of annular housing 47 and intermediate annular component 75. Non-resilient feature 91 is adapted to damp vibrations generated during rotation of rotatable shaft 5, thus reducing noise and wear.

[0054] Certain exemplary embodiments have been described to provide a general understanding of the principles of the structure, function, and use of the systems, devices, and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the systems, devices, and methods explicitly described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments, and that the scope of the present invention is defined only by the claims. Features described or illustrated in connection with one exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be within the scope of the present invention.

Claims

1. 1. A shaft seal assembly configured to sealingly separate a high pressure region and a low pressure region of a rotating machine, comprising: a rotary seal member drivingly coupled to and configured to co-rotate with a rotary shaft of the rotary equipment; a stationary porous seal member adapted to be coupled to a stationary housing of the rotary equipment and extending around the rotary seal member; at least one seal gas inlet port adapted to communicate pressurized seal gas with said stationary porous seal member; A shaft seal assembly, wherein the rotary seal member has a conical outer seal surface and the stationary porous seal member has a conical inner seal surface, the conical inner seal surface opposing the conical outer seal surface.

2. 2. The shaft seal assembly of claim 1, wherein the conical outer sealing surface has a first end adapted to face the high pressure region and a second end adapted to face the low pressure region, the first end having a larger diameter than the second end, and the conical inner sealing surface has a first end adapted to face the high pressure region and a second end adapted to face the low pressure region, the first end having a larger diameter than the second end.

3. 2. The shaft seal assembly of claim 1, wherein the conical outer sealing surface has a first end adapted to face the high pressure region and a second end adapted to face the low pressure region, the first end having a smaller diameter than the second end, and the conical inner sealing surface has a first end adapted to face the high pressure region and a second end adapted to face the low pressure region, the first end having a smaller diameter than the second end.

4. 4. The shaft seal assembly of claim 2 or 3, wherein the at least one seal gas inlet port is located near the first end of the conical inner seal surface.

5. The shaft seal assembly of any one of claims 1 to 4, further comprising a resilient member adapted to axially urge the conical inner sealing surface toward the conical outer sealing surface.

6. 6. The shaft seal assembly of claim 5, wherein in use, the pressurized sealing gas flows through the stationary porous seal member between the conical inner seal surface and the conical outer seal surface to balance the axial thrust of the resilient member of the stationary porous seal member and form a gap between the conical inner seal surface and the conical outer seal surface.

7. The shaft seal assembly of claim 6 , wherein, in use, sealing gas pressure within the gap decreases from the first end toward the second end.

8. A shaft seal assembly according to any preceding claim, wherein the stationary porous seal member is housed within a ring casing and is axially movable therein.

9. The shaft seal assembly of claim 8 , wherein the stationary porous seal member is radially movable with the ring casing.

10. 10. A shaft seal assembly according to claim 8 or 9, wherein the stationary porous seal member is rigidly constrained to an annular housing carried by the ring casing.

11. The shaft seal assembly of claim 10 , wherein the annular housing is retained within the ring casing with axial and radial clearances for axial and radial movement within the ring casing.

12. 11. The shaft seal assembly of claim 10, wherein the annular housing is mounted to the intermediate annular component with a radial clearance relative to the intermediate annular component, and the intermediate annular component is retained in the ring casing with an axial clearance.

13. The shaft seal assembly according to claim 10 or 11, wherein a balance gasket is disposed between the ring casing and the annular housing.

14. The shaft seal assembly of claim 12 , wherein balance gaskets are disposed between the intermediate annular component and the ring casing, and between the annular housing and the intermediate annular component.

15. A shaft seal assembly according to any preceding claim, wherein the stationary porous seal member has an outer cylindrical surface coaxial with the conical inner seal surface.

16. A shaft seal assembly according to any preceding claim, wherein the conical outer sealing surface is integral with a shaft sleeve adapted to be angularly coupled to a rotating shaft.

17. A shaft seal assembly according to any preceding claim, including a plurality of sealing gas inlet ports arranged circumferentially around the conical inner sealing surface.

18. A shaft seal assembly according to any preceding claim, including a hardening treatment on at least some surfaces that are subjected to mechanical contact.

19. The shaft seal assembly of any preceding claim, further comprising a non-resilient feature between two components of the shaft seal assembly.

20. A rotating machine comprising a stationary casing and a shaft supported for rotation within the casing, the rotating machine comprising a shaft seal assembly according to any one of claims 1 to 19 disposed between a high pressure region and a low pressure region.

Images