Method for testing the leak tightness of a steam installation using a removable inflatable helical seal and corresponding assembly
The inflatable helical seal addresses the challenges of cumbersome and risky leak testing in steam turbines by enabling quick, safe, and reliable leak detection without turbine operation, using a removable seal with defined pressure and turn count.
Patent Information
- Application Number
- FR2023011469
- Authority / Receiving Office
- FR · FR
- Patent Type
- Utility models
- Current Assignee / Owner
- Filing Date
- 2023-10-23
- Publication Date
- 2025-11-07
- Estimated Expiration
- 2033-10-23
AI Technical Summary
Existing leak testing methods for steam turbines, such as the half-ring system with O-rings, are cumbersome, prone to imperfect seals, noisy, and risky to leave in place during operation, potentially damaging the turbine, and can drop fixing screws into the lower casing.
A removable inflatable helical seal is used, comprising an envelope with multiple turns surrounding the rotor, inflated to press against the sealed box and bearing, allowing leak testing without turbine operation, with features like a specific pressure range and turn count, and an inlet for inflation fluid.
Facilitates quick and safe leak testing by eliminating noise pollution and reducing risks of damage, ensuring reliable detection of leaks without turbine operation, and preventing screw loss.
Smart Images
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Abstract
Description
Title of the invention: Method for testing the leak tightness of a steam installation using a removable inflatable helical seal and corresponding assembly
[0001] The present invention relates to a method for testing the leakage of an installation comprising a steam turbine having a stator and a rotor that is movable and rotates relative to the stator around an axis, and at least one bearing.
[0002] The invention also relates to a corresponding assembly, comprising such an installation.
[0003] The invention also relates to a naval platform comprising such an assembly.
[0004] It is known, for ensuring the seal between the rotor and the stator of a turbine at Steam, by using one or more sealed boxes fixed to the stator, to prevent steam from escaping into the surrounding atmosphere. Such sealed boxes are sometimes also used between stages of the steam turbine.
[0005] These sealed boxes, known per se, create steam rings between the rotor and a comb fixed relative to the stator. In principle, these sealed boxes are only sealed when steam is available, that is, when the turbine is running.
[0006] To perform a leak test of the system when it is stopped, one solution is to use a system comprising two half-rings secured to each other by nuts around the rotor between the sealed housing and the bearing, and conventional O-rings. The system is positioned axially between the sealed housing and the bearing. The system is then pressurized using compressed air. The compressed air in the turbine can pass between the sealed housing and the rotor, but is stopped by the system and the bearing. This allows any leaks in the system to be detected by their noise, as the leak through the sealed housing is eliminated or limited. Thus, the leak test functions correctly.
[0007] However, the half-ring system is difficult to implement. Indeed, it generally takes more than half a day to equip a turbine with it. The seal obtained between the sealed box and the bearing is rarely perfect, which generates an air leak. This air leak is characterized by potentially significant noise. This acoustic "pollution" can make the detection of other leaks more difficult.
[0008] Furthermore, this system lacks a keying device. Therefore, there is a risk that it may be left in place beneath a turbine dust cover. However, starting the turbine while the system is still in place could damage the turbine.
[0009] Finally, during the installation or dismantling of the system, it is possible that fixing screws may fall into a lower casing of the turbine.
[0010] One object of the invention is therefore to facilitate the performance of leak tests.
[0011] To this end, the invention relates to a method for testing the leak-tightness of an installation comprising a steam turbine, the turbine having a stator, a rotor rotating relative to the stator around an axis, at least one bearing, and at least one sealed box intended to ensure a seal between the rotor and the stator when the turbine is in operation, the sealed box being non-sealed when the turbine is not in operation, the method comprising the following steps:
[0012] - obtaining an inflatable helical seal, the seal comprising an envelope forming a plurality of turns and defining an internal volume, the seal includes an inlet adapted to allow inflation fluid to enter the internal volume,
[0013] - installation of the seal on the turbine, the coils of the seal surrounding the rotor around the axis, the seal being located axially between the sealed box and the bearing,
[0014] - inflation of the seal put in place to bring it from a slightly or uninflated state, to a inflated state, in which a first of the turns presses axially on the sealed box, a last of the turns presses axially on the bearing, and any two successive turns along the axis are axially supported on each other, and
[0015] - pressurizing the installation to test its leak-tightness, with the seal in place and in the inflated state, the turbine not being in operation.
[0016] According to other advantageous aspects of the invention, the method comprises one or more of the following features, taken individually or in all technically possible combinations:
[0017] - the internal volume is at a pressure between 1.0 and 2.0 bar absolute in the state Inflated, preferably between 1.2 and 1.6 bar;
[0018] - the seal has a number of turns between 2.5 and 3.5;
[0019] - the inlet is located on a radially outer edge of one of the turns of the joint put in position, relative to the axis;
[0020] - the inlet is located at one longitudinal end of the joint put in place following the spirals, the longitudinal end being located axially on the bearing side;
[0021] - the envelope comprises two sheets glued one on top of the other, forming two edges protruding extending along the spirals, one of the two edges being located, radially with respect to the axis, on one side of the internal volume when the joint is in place, and the other of the two edges being located on the other side;
[0022] - the coils, in their deflated state, have a width radially with respect to the axis between 40 and 60 mm, and, in the inflated state of the installed seal, a thickness between 7.0 and 10.0 mm along the axis; and
[0023] - the seal includes a tab located in a longitudinal extension of the internal volume by following the coils of the seal in place, the tab being against the sealed box.
[0024] The invention also relates to an assembly comprising:
[0025] - an installation comprising a steam turbine, the turbine comprising a stator, a rotor that rotates relative to the stator around an axis, at least one bearing, and at least one sealed box designed to ensure a seal between the rotor and the stator when the turbine is in operation, the sealed box being unsealed when the turbine is not in operation, and
[0026] - an inflatable helical seal comprising a casing forming a plurality of coils and defining an internal volume, the seal including an inlet adapted to allow inflation fluid to enter the internal volume,
[0027] the seal being adapted to be fitted onto the turbine, the coils of the seal surrounding the rotor around the axis, the seal being located axially between the sealed box and the bearing,
[0028] the seal put in place being adapted to go from a slightly or not inflated state, to a state inflated, in which a first of the turns presses axially on the sealed box, a last of the turns presses axially on the bearing, and any two successive turns along the axis are axially supported on each other,
[0029] the installation being adapted to be pressurized to test its leak-tightness.
[0030] The invention also relates to a naval platform comprising an assembly as described above.
[0031] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings, in which:
[0032] [Fig-1] [Fig.1] is a schematic representation of an assembly according to the invention, on which a method according to the invention is implemented,
[0033] [Fig.2] [Fig.2] is a detailed cross-sectional view along a radial plane relative to the rotor axis of the assembly shown in [Fig.1], showing the helical seal in the swollen state between a sealing box and a turbine bearing,
[0034] [Fig.3] [Fig.3] is a perspective view of the joint shown in Figures 1 and 2, the seal being in a deflated state,
[0035] [Fig.4] [Fig.4] is a front view (along the axis of the turbine) of the joint shown In Figures 1 to 3, the seal is shown in its deflated state, and
[0036] [Fig. 5] [Fig. 5] is a local view, in section perpendicular to its length, of the joint shown in Figures 1 to 4, showing the structure of the joint envelope, the joint being in the deflated state.
[0037] With reference to [Fig.1], a naval platform 10 according to the invention is described.
[0038] The naval platform 10 is, for example, a submarine or a vessel surface.
[0039] In addition to classic equipment of a naval platform (not shown), the naval platform 10 includes an assembly 12 according to the invention.
[0040] The assembly 12 includes an installation 14, and an inflatable helical seal 16 adapted to be fitted onto a steam turbine 18 of the installation.
[0041] Installation 14 is, for example, intended to provide propulsion for naval platform 10.
[0042] The installation 14 is adapted to be pressurized to test its leak tightness, the turbine 18 not being in operation.
[0043] The turbine 18 comprises a stator 20, and a rotor 22 movable in rotation relative to the stator around an axis X. The turbine 18 comprises a bearing 24 and a sealed box 26 located on one side of the stator 20 along the axis X, and for example another bearing 28 and another sealed box 30 located on the opposite side of the stator.
[0044] The stator 20 surrounds the rotor 22 around the X axis. The rotor 22 and the stator 20 advantageously define radially between them one or more passages 32 for steam.
[0045] The bearings 24, 28 are for example located around a shaft 34 of the rotor extending along the X axis.
[0046] The bearing 24 includes for example a cover 36 visible in the [Fig.2].
[0047] The sealed box 26 is advantageously located axially between the stator 20 and the bearing 24, for example downstream of the stator in the direction of steam expansion.
[0048] The sealed box 26 is adapted to ensure a seal between the rotor 22 and the stator 20 when the turbine 18 is operating, that is, when the turbine is actually expanding steam, according to a technology known per se. The sealed box 26 is not sealed when the turbine 18 is not operating.
[0049] The sealed box 26 and the bearing 24 axially delimit between them a space 38 in which the seal 16 is intended to be installed to carry out a sealing test.
[0050] For example, the sealed box 26 includes a body 40 fixed on the stator 20, and at least one comb holder 42 fixed on the body, and at least one comb 44 fixed on the comb holder.
[0051] The comb 44 advantageously surrounds the rotor 22 around the X axis and is located opposite a surface 46 radially outside the rotor 22. Sealing is ensured when the comb 44 is in contact with the surface 46.
[0052] The seal 16 includes a casing 48 (Figures 3 to 5) forming a plurality of turns 50 and defining an internal volume 52. The seal 16 includes an inlet 54 adapted to allow an inflation fluid 58 to enter the internal volume 52.
[0053] The seal 16 is adapted to be fitted onto the turbine 18 (Figures 1 and 2), the turbine not being in operation in principle, the turns 50 of the seal surrounding the rotor 22 around the axis X, the seal 16 being located axially between the sealed box 26 and level 24.
[0054] The seal 16 put in place is adapted to go from a state that is not very inflated or not inflated (Figures 3 to 5), to a state that is inflated ([Fig.2]), in which a first 50A of the turns 50 presses axially on the sealed box 26, a last 50B of the turns 50 presses axially on the bearing 24, and two of the successive turns 50 along the axis X are in axial contact with each other.
[0055] The seal 16 advantageously has a number of turns 50 between 2.5 and 3.5, and for example substantially equal to 3.0.
[0056] The seal 16 includes, for example, a tab 60 ([Fig.3]) located in a longitudinal extension of the inner volume 52 following the turns 50 of the seal in place, the tab being against the sealed box 26. The tab 60 facilitates the installation of the seal 16 and its removal (an operator can advantageously hold the seal during installation).
[0057] By "spire", we mean, for example, a portion of the joint 16 in its length direction making exactly one turn around the axis X.
[0058] Advantageously, the first 50A of the turns 50 extends against the sealed box 26, radially to the body 40.
[0059] Advantageously, the last 50B of the turns extends against the bearing 24, radially to the cover 36.
[0060] For example, the coils 50 have, in the deflated state radially with respect to the X axis, a width El between 40 and 60 mm, and, in the inflated state of the joint in place, a thickness E2 between 7.0 and 10.0 mm along the X axis.
[0061] For example, two of the turns 50 are located axially on either side of a radial protrusion 62 of the rotor 22.
[0062] The envelope 48 comprises for example two sheets 48A, 48B ([Fig.5]) glued one on top of the other forming two protruding edges 64, 66 extending along the coils 50, one of the two edges being located, radially with respect to the X axis, on one side of the internal volume 52 when the seal 16 is in place, and the other of the two edges being located on the other side.
[0063] The internal volume 52 is for example at a pressure between 1.0 and 2.0 bar absolute in the inflated state, preferably between 1.2 and 1.6 bar.
[0064] The inlet 54 is advantageously located on the radially external edge 64 of one of the turns 50 of the seal 16, relative to the axis X. The inlet 54 is advantageously located at a longitudinal end 68 of the seal 16 placed following the turns, the end being located axially on the side of the bearing 24.
[0065] The inlet 54 is for example connected to a source 70 of inflation fluid 58, for example a bulb, or alternatively a source of compressed air.
[0066] We will now describe the operation of assembly 12 and illustrate a process according to the invention.
[0067] The seal 16 is installed on the turbine 18, generally when the turbine is stationary. The turns 50 of the seal surround the rotor 22 around the X-axis. The seal 16 is located axially between the sealed housing 26 and the bearing 24.
[0068] Then, the installed seal 16 is inflated to bring it from a slightly or uninflated state (Figures 3 to 5) to an inflated state ([Fig. 2]). The first 50A of the turns 50 bears axially on the sealed box 26, advantageously up to the body 40. The last 50B of the turns 50 bears axially on the bearing 24, advantageously up to the cover 36. Any two successive turns 50 along the X-axis bear axially against each other. The seal 16 thus creates continuity between the sealed box 26, advantageously its body 40, and the bearing 24, advantageously its cover 36. The seal 16 prevents or limits leakage between the comb 44 and the rotor 22 by forming a barrier between the sealed box 26 and the bearing 24.
[0069] The installation 14 is then pressurized, for example by injecting compressed air 72 into the turbine 18. It is thus possible to detect any leaks, for example by their noise, without being hindered by the fact that the sealed box 26 is not itself sealed.
[0070] The seal 16 is then deflated and, in principle, removed. Optionally, covers (not shown), which had been removed from the turbine 18 to allow the seal to be fitted, are put back in place.
[0071] Thanks to the characteristics described above, the seal 16 is installed and inflated easily and quickly. This facilitates leak testing. The risk of leaving a solid system in place that could damage the turbine 18 when the installation 14 is restarted, or of inserting a fixing screw into the turbine, is eliminated.
[0072] The sealing provided by the seal 16 is possibly relative, but advantageously sufficient to avoid any untimely noise when the installation 14 is pressurized.
Claims
Demands
1. A method for testing the leak-tightness of an installation (14) comprising a steam turbine (18), the turbine (18) having a stator (20), a rotor (22) rotatable relative to the stator (20) about an axis (X), at least one bearing (24), and at least one sealed box (26) for sealing between the rotor (22) and the stator (20) when the turbine (18) is in operation, the sealed box (26) being non-sealing when the turbine (18) is not in operation, the method comprising the following steps: - obtaining an inflatable helical seal (16), the seal (16) comprising a casing (48) forming a plurality of turns (50) and defining an internal volume (52), the seal (16) comprising an inlet (54) adapted for introducing an inflation fluid (58) into the internal volume (52), - installing the seal (16) on the turbine (18), the turns (50) of the joint (16) surrounding the rotor (22) around the axis (X),the seal (16) being located axially between the sealed box (26) and the bearing (24), - inflation of the seal (16) in place to bring it from a slightly or uninflated state, to an inflated state, in which a first (50A) of the turns (50) presses axially on the sealed box (26), a last (50B) of the turns (50) presses axially on the bearing (24), and any two successive turns (50) along the axis (X) are axially pressed against each other, and - pressurization of the installation (14) to test its tightness, the seal (16) being in place and inflated, the turbine (18) not being in operation.
2. A method according to claim 1, wherein the internal volume (52) is at a pressure between 1.0 and 2.0 bar absolute in the inflated state, preferably between 1.2 and 1.6 bar.
3. Method according to claim 1 or 2, wherein the seal (16) has a number of turns (50) between 2.5 and 3.
5.
4. A method according to any one of claims 1 to 3, wherein the inlet (54) is located on an edge (64) radially outside one of the turns (50) of the seal (16) put in place, with respect to the axis (X).
5. A method according to any one of claims 1 to 4, wherein the inlet (54) is located at a longitudinal end (68) of the seal (16) installed following the turns (50), the longitudinal end (68) located axially on the side of the bearing (24).
6. A method according to any one of claims 1 to 5, wherein the envelope (48) comprises two sheets (48A, 48B) glued together to form two projecting edges (64, 66) extending along the coils (50), one of the two edges (64, 66) being located, radially with respect to the axis (X), on one side of the inner volume (52) when the seal (16) is in place, and the other of the two edges (64, 66) being located on the other side.
7. A method according to any one of claims 1 to 6, wherein the coils (50) have, in the deflated state, radially with respect to the axis (X), a width (El) of between 40 and 60 mm, and, in the inflated state of the joint (16) in place, a thickness (E2) of between 7.0 and 10.0 mm along the axis (X).
8. A method according to any one of claims 1 to 7, wherein the seal (16) comprises a tab (60) situated in a longitudinal extension of the inner volume (52) following the turns (50) of the seal (16) in place, the tab (60) being against the sealed box (26).
9. Assembly (12) comprising: - an installation (14) comprising a steam turbine (18), the turbine (18) having a stator (20), a rotor (22) rotatable relative to the stator (20) about an axis (X), at least one bearing (24), and at least one sealed box (26) for sealing between the rotor (22) and the stator (20) when the turbine (18) is in operation, the sealed box (26) being non-sealing when the turbine (18) is not in operation, and - an inflatable helical seal (16) comprising a casing (48) forming a plurality of turns (50) and defining an internal volume (52), the seal (16) having an inlet (54) adapted for allowing an inflation fluid (58) to enter the internal volume (52), the seal (16) being adapted for being fitted onto the turbine (18), the turns (50) of the joint (16) surrounding the rotor (22) around the axis (X),the seal (16) being located axially between the sealed box (26) and the bearing (24), the seal (16) being adapted to go from a slightly or not inflated state, to an inflated state, in which a first (50A) of the turns (50) presses axially on the sealed box (26), a last (50B) of the turns (50) presses axially on the bearing (24), and two of the successive turns (50) along the axis (X) are in contact with each other, axially, the installation (14) being adapted to be pressurized to test its leak-tightness.
10. Naval platform (10) comprising an assembly (12) according to claim 9.