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 noisy half-toroidal systems by providing a reliable and efficient method for sealing tests in steam turbines, ensuring leak detection without risking turbine damage.
Patent Information
- Application Number
- FR2023011469
- Authority / Receiving Office
- FR · FR
- Patent Type
- Utility models
- Current Assignee / Owner
- Filing Date
- 2023-10-23
- Publication Date
- 2025-04-25
- Estimated Expiration
- 2033-10-23
AI Technical Summary
Existing sealing tests for steam turbines using half-toroidal systems are cumbersome, often imperfect, noisy, and pose risks of damage during turbine rotation, with screws potentially falling into lower housings.
An inflatable helical seal with an envelope forming multiple turns is installed between the waterproof box and the landing, inflated to press against both, forming a barrier to test sealing without operation, using compressed air for detection of leaks.
Facilitates easy and quick sealing tests, reduces noise, and prevents turbine damage by eliminating the need for cumbersome half-toroidal systems, ensuring reliable leak detection.
Smart Images
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Abstract
Description
Title of the invention: Method for testing the 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 tightness of an installation comprising a steam turbine comprising a stator and a rotor which can rotate 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, to ensure the seal between the rotor and the stator of a turbine at steam, to use one or more watertight boxes fixed on the stator, to prevent the steam from escaping into the surrounding atmosphere. Such watertight boxes are sometimes also used between stages of the steam turbine.
[0005] These sealed boxes, known in themselves, 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 to say when the turbine is in operation.
[0006] To carry out a leak test of the installation when stopped, one solution consists of using a system comprising two half-crowns fixed to each other by nuts around the rotor between the sealed box and the bearing, and conventional O-rings, the system being arranged axially between the sealed box and the bearing. The installation is then pressurized using compressed air. The compressed air located in the turbine can pass between the sealed box and the rotor, but is stopped by the system and the bearing. This makes it possible to detect, by their noise, any leaks in the installation, the leak through the sealed box being eliminated or limited. Thus, the leak test works correctly.
[0007] However, the half-crown system is difficult to implement. In fact, 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 a noise that can be significant. This acoustic "pollution" can make the detection of other leaks more difficult.
[0008] Furthermore, this system does not have a keying device. There is therefore a risk that it will be left in place under a turbine dust cover. However, rotating the turbine while the system is still in place is likely to damage the turbine.
[0009] Finally, when installing or dismantling the system, it is possible that fixing screws fall into a lower casing of the turbine.
[0010] One aim of the invention is therefore to facilitate the carrying out of leak tests.
[0011] To this end, the invention relates to a method for testing the tightness of an installation comprising a steam turbine, the turbine comprising a stator, a rotor which can rotate relative to the stator about 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 interior volume, the seal comprising an inlet adapted to allow an inflation fluid to enter the interior volume,
[0013] - installation of the seal on the turbine, the turns 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 change it from a slightly or not at all inflated 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 in axial support on each other, and
[0015] - pressurizing the installation to test its tightness, the seal being 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 characteristics, taken in isolation or in all technically possible combinations:
[0017] - the interior 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 seal put in place, relative to the axis;
[0020] - the inlet is located at a longitudinal end of the joint put in place following the coils, the longitudinal end being located axially on the bearing side;
[0021] - the envelope comprises two sheets glued together to form two edges projections extending along the turns, one of the two edges being located, radially relative to the axis, on one side of the interior volume when the seal is in place, and the other of the two edges being located on the other side;
[0022] - the coils have, in the deflated state, radially relative to the axis, a width between 40 and 60 mm, and, in the inflated state of the seal in place, a thickness between 7.0 and 10.0 mm along the axis; and
[0023] - the seal comprises a tab located in a longitudinal extension of the interior volume by following the turns of the seal in place, the tab being against the waterproof box.
[0024] The invention also relates to an assembly comprising:
[0025] - an installation comprising a steam turbine, the turbine comprising a stator, a rotor capable of rotating relative to the stator about an axis, at least one bearing, and at least one sealed box intended to ensure sealing 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, and
[0026] - an inflatable helical seal comprising an envelope forming a plurality of coils and defining an interior volume, the seal comprising an inlet adapted to allow an inflation fluid to enter the interior volume,
[0027] the seal being adapted to be placed on the turbine, the turns 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 pass 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 in axial support on each other,
[0029] the installation being adapted to be put under pressure to test its tightness.
[0030] The invention also relates to a naval platform comprising an assembly as described above.
[0031] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings, in which:
[0032] [Fig-1] [Fig.l] is a schematic representation of a set according to the invention, on which a method according to the invention is implemented,
[0033] [Fig.2] [Fig.2] is a detail view, in section along a radial plane relative to the rotor axis, of the assembly shown in [Fig.l], showing the helical seal in the inflated 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 being in the deflated state, and
[0036] [Fig.5] [Fig.5] is a local view, in section perpendicular to its length, of the seal shown in Figures 1 to 4, showing the structure of the seal envelope, the seal being in the deflated state.
[0037] With reference to [Fig.l], a naval platform 10 according to the invention is described.
[0038] The naval platform 10 is for example an underwater vehicle or a building of surface.
[0039] In addition to conventional equipment of a naval platform (not shown), the naval platform 10 comprises an assembly 12 according to the invention.
[0040] The assembly 12 comprises an installation 14, and an inflatable helical seal 16 adapted to be placed on a steam turbine 18 of the installation.
[0041] The installation 14 is for example intended to ensure the propulsion of the naval platform 10.
[0042] The installation 14 is adapted to be pressurized to test its 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 for example the rotor 22 around the axis X. 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 axis X.
[0046] The bearing 24 comprises for example a cover 36 visible in [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 in operation, that is to say when the turbine actually expands steam, according to a technology known per se. The sealed box 26 is not sealed when the turbine 18 is not in operation.
[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 comprises 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 axis X and is located opposite a radially outer surface 46 of the rotor 22. Sealing is ensured when the comb 44 is in contact with the surface 46.
[0052] The seal 16 comprises a casing 48 (Figures 3 to 5) forming a plurality of turns 50 and defining an interior volume 52. The seal 16 comprises an inlet 54 adapted to allow an inflation fluid 58 to enter the interior volume 52.
[0053] The seal 16 is adapted to be placed on the turbine 18 (Figures 1 and 2), the turbine not being in principle in operation, 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 pass from a slightly or not inflated state (Figures 3 to 5), to an inflated state ([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 any two of the turns 50 successive along the axis X are in axial support on each other.
[0055] The seal 16 advantageously has a number of turns 50 of between 2.5 and 3.5, and for example substantially equal to 3.0.
[0056] The seal 16 comprises for example a tab 60 ([Fig.3]) located in a longitudinal extension of the interior volume 52 following the turns 50 of the seal put 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 “turn” is meant for example a portion of the seal 16 in the direction of its length making exactly one turn around the axis X.
[0058] Advantageously, the first 50A of the turns 50 extends against the sealed box 26, radially up to the body 40.
[0059] Advantageously, the last 50B of the turns extends against the bearing 24, radially up to the cover 36.
[0060] For example, the turns 50 have, in the deflated state radially relative to the axis X, a width E1 of between 40 and 60 mm, and, in the inflated state of the seal in place, a thickness E2 of between 7.0 and 10.0 mm along the axis X.
[0061] For example, two of the turns 50 are located axially on either side of a radial protuberance 62 of the rotor 22.
[0062] The envelope 48 comprises for example two sheets 48A, 48B ([Fig.5]) glued to one another to form two projecting edges 64, 66 extending along the turns 50, one of the two edges being located, radially relative to the axis X, on one side of the interior volume 52 when the seal 16 is in place, and the other of the two edges being located on the other side.
[0063] The interior volume 52 is for example at a pressure of 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 outer 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 put in place 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 the assembly 12 and illustrate a method according to the invention.
[0067] The seal 16 is placed on the turbine 18, in principle when stopped. The turns 50 of the seal surround the rotor 22 around the axis X. The seal 16 is located axially between the sealed box 26 and the bearing 24.
[0068] Then, the seal 16 put in place is inflated to make it pass from the little or not inflated state (Figures 3 to 5), to an inflated state ([Fig.2]). The first 50A of the turns 50 presses axially on the sealed box 26, advantageously up to the body 40. The last 50B of the turns 50 presses axially on the bearing 24, advantageously up to the cover 36. Any two of the turns 50 successive along the axis X are in axial support on 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 a leak passing 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 bothered 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 replaced.
[0071] Thanks to the characteristics described above, the seal 16 is installed and inflated easily and quickly. This facilitates the performance of leak tests. The risk of leaving in place a solid system which could damage the turbine 18 when restarting the installation 14, or of introducing a fixing screw into the turbine, disappears.
[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
Claims
1. A method for testing the tightness of an installation (14) comprising a steam turbine (18), the turbine (18) comprising 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) intended to ensure a seal between the rotor (22) and the stator (20) when the turbine (18) is in operation, the sealed box (26) being non-sealed 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 interior volume (52), the seal (16) comprising an inlet (54) adapted to allow an inflation fluid (58) to enter the interior volume (52), - placing the seal (16) on the turbine (18), the turns (50) of the seal (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) put in place to make it pass from a little 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 any two of the turns (50) successive along the axis (X) are in axial support on each other, and - pressurizing the installation (14) to test its sealing, the seal (16) being in place and in the inflated state, the turbine (18) not being in operation.,
2. A method according to claim 1, wherein the interior volume (52) is at a pressure of between 1.0 and 2.0 bar absolute in the inflated state, preferably between 1.2 and 1.6 bar.
3. A method according to claim 1 or 2, wherein the seal (16) has a number of turns (50) of between 2.5 and 3.
5.
4. Method according to any one of claims 1 to 3, in which the inlet (54) is located on a radially outer edge (64) of one of the turns (50) of the seal (16) put in place, relative to the axis (X).
5. Method according to any one of claims 1 to 4, in which the inlet (54) is located at a longitudinal end (68) of the seal (16) put in place following the turns (50), the longitudinal end (68) is located axially on the side of the bearing (24).
6. Method according to any one of claims 1 to 5, in which the envelope (48) comprises two sheets (48A, 48B) glued to each other forming two projecting edges (64, 66) extending along the turns (50), one of the two edges (64, 66) being located, radially with respect to the axis (X), on one side of the interior 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. Method according to any one of claims 1 to 6, in which the turns (50) have, in the deflated state, radially relative to the axis (X), a width (El) of between 40 and 60 mm, and, in the inflated state of the seal (16) in place, a thickness (E2) of between 7.0 and 10.0 mm along the axis (X).
8. Method according to any one of claims 1 to 7, in which the seal (16) comprises a tab (60) located in a longitudinal extension of the interior volume (52) following the turns (50) of the seal (16) put 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) comprising 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) intended to ensure a seal between the rotor (22) and the stator (20) when the turbine (18) is in operation, the sealed box (26) being non-sealed 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 interior volume (52), the seal (16) comprising an inlet (54) adapted to allow an inflation fluid (58) to enter the interior volume (52), the seal (16) being adapted to be placed on the turbine (18), the turns (50) of the seal (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) put in place being adapted to pass 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 any two of the turns (50) successive along the axis (X) are in support on each other, axially, the installation (14) being adapted to be put under pressure to test its tightness.
10. Naval platform (10) comprising an assembly (12) according to claim 9.