Stator diaphragm with seal ring, steam turbines and power plants including stator diaphragm and methods for arranging seal rings in stator diaphragms

Abstract

The present disclosure relates to a stator diaphragm comprising a diaphragm body including a radially outer ring, a radially inner ring and a plurality of stator vanes extending between the radially outer ring and the radially inner ring. The diaphragm body further comprises an axial seal face and a circular groove at the axial seal face. The stator diaphragm further comprises a seal ring and a plurality of spacers arranged in the circular groove, and the spacers axially position the seal ring in the circular groove. The present disclosure further relates to steam turbines comprising such stator diaphragms, to power plants comprising said steam turbines, and to methods for arranging a seal ring between a seal face of a stator diaphragm and a stationary part of a steam turbine.

Description

STATOR DIAPHRAGM WITH SEAL RING, STEAM TURBINES AND POWER PLANTS INCLUDING STATOR DIAPHRAGM AND METHODS FOR ARRANGING SEAL RINGS IN STATOR DIAPHRAGMSTECHNICAL FIELD

[0001] The present disclosure relates to seals and sealing of stator diaphragms for turbines, particularly for steam turbines. The present disclosure further relates to steam turbines as well as to power plants comprising such stator diaphragms. The present disclosure further particularly relates to methods of adaptation of axial clearances for stator diaphragms.BACKGROUND

[0002] Steam turbines are rotary mechanical devices that generate mechanical energy from steam that flows through the turbine. For example, electrical power may be generated when the turbine is connected to a generator. A steam turbine comprises a rotor which includes a shaft and a plurality of rows of rotor blades. A row of blades may also be known as wheel. The shaft is arranged along an axial direction of the turbine, and the plurality of rows of blades is connected to the shaft. The rotor is supported by bearings and is housed in a casing, e.g. a cylinder-shaped casing.

[0003] A plurality of nozzles (also known as stator blades) may be fixed with respect to the casing and form part of a stator. The nozzles may also be called “vanes” and may be directly or indirectly attached to the casing. A row of vanes indirectly connected to a casing is herein called a "diaphragm". A stator diaphragm may be regarded herein as a disc-shaped device including a row of vanes. The nozzles are arranged between the rows of rotor blades in a turbine. The interaction between the nozzles and the rotor blades is responsible for rotation of a turbine. The casing and the nozzles form the stationary parts of the steam turbine.

[0004] A pair of a row of nozzles and a subsequent row of rotor blades is usually referred to as a stage of a turbine. A steam turbine typically comprises a plurality of stages. A steam turbine may comprise sections which operate at different pressures. Turbine sections are also known as cylinders. A steam turbine may for example comprise at least one of a high-pressure (HP) section, an intermediate pressure (IP) section and a low-pressure (LP) section.

[0005] During operation of the steam turbine, the nozzles have a fixed position. They direct the flow of steam that is between a preceding rotor blade row and the next rotor blade row. Rows of rotor blades are designed to turn as the steam passes through them. The rotation of the rows turns the shaft to which they are attached. And the shaft may for example turn a generator for producing electric power.

[0006] Steam may be provided at a high pressure side of a steam turbine through a steam inlet. The steam may then expand along the various stages of the turbine. In order to ensure that the steam follows the intended path, several sealings are provided, both in relation with the rotor blades and in relation with the stator blades. Such sealings may be configured to avoid any fluid (steam) loss in varying operational conditions, e.g. with varying pressure and temperature and thus are to provide appropriate sealing regardless of (thermal) expansion of parts. In particular, a seal ring is provided at an axial face of the diaphragm, e.g. between two neighboring stator diaphragms. This face is also known as an axial seal face. The other face of the diaphragm that is upstream (high-pressure side) is called a forward face. A seal ring can also seal a space between a stator diaphragm and a casing. Such a seal ring extends along the circumference of a stator diaphragm.

[0007] In order to provide appropriate axial clearance between rotor blades and stator blades, it is necessary to precisely machine a face of the stator diaphragm to properly align rotor blades and stator blades. In essence, this machining is needed to be able to fit a stator diaphragm into a casing and to allow said stator diaphragm to work with other elements of a turbine. Such machining requires a significant amount of time and is technologically challenging. It is also not done at a power plant, but at a specialized machine shop that has capabilities to perform said machining. It may be the case that, after an installation attempt, further machining is required. It follows that a stator diaphragm has to be taken from a power plant to a machine shop which impacts the time of servicing or upgrading a steam turbine. This also means that said stator diaphragm, especially for older machines, has to be transported even multiple times between a power plant and a shop before the steam turbine will finally be assembled with a proper axial clearance.

[0008] The present disclosure provides examples of methods, stator diaphragms, steam turbines and power plants that allow for adjustment of clearance with reduction or elimination at least some of the aforementioned problems. Specific examples pursue at least one of avoiding the need to transport multiple times a stator diaphragm between a power plant and a machining shop, decreasing the time of servicing, upgrading or manufacturing.SUMMARY

[0009] The principles of the invention will be disclosed below and explained. It should be noted that any explanations are provided for a better understanding of the invention and should not be understood as exhaustive or limiting to the invention. It should be noted that while the description is focused on power plants, turbines are used also outside power plants and the invention as well as its benefits described herein are also applicable to turbines used outside of power plants.

[0010] In an aspect of the present disclosure, a stator diaphragm is provided. The stator diaphragm comprises a diaphragm body including a radially outer ring, a radially inner ring and a plurality of stator vanes extending between the radially outer ring and the radially inner ring. The diaphragm body comprises an axial seal face and a circular groove at the axial seal face. The stator diaphragm further comprises a seal ring and a plurality of spacers arranged in the circular groove, wherein the spacers axially position the seal ring in the circular groove. In other words, the spacers are configured to axially position the seal ring in the circular groove. The stator diaphragm can be a stator diaphragm for a steam turbine.

[0011] In accordance with this aspect, an axial seal for a stator diaphragm body is provided i.e., a seal that seals a space between the stator diaphragm body and a component axially downstream from the stator diaphragm body. The component can be, but is not limited to, another stator diaphragm, or casing. The axial position of the seal ring is determined by the spacers in the circular groove. By selecting suitable spacers, the position of the seal ring may be changed. Thereby, the position of the stator diaphragm is changed and so the axial clarence between rotor blades and stator blades is changed. Suitable spacers can be spacers with a suitable length. In other words, the position of the stator diaphragm body with respect to another component is determined by the spacers, as the seal ring engages with such other component. Specifically, the stator diaphragm is being moved upstream by the spacers.

[0012] Machining of the stator diaphragm known in the art .e.g., for adjusting clearance, to be able to assemble a turbine can thereby be avoided. This offers a great advantage in terms of saving of time as this machining cannot be done at a site where a (steam) turbine is or is to be installed. It follows that a stator diaphragm according to this aspect does not have to be transported multiple times between a machining shop and a power plant in order to assemble a turbine with a proper axial clearance. The use of spacers offers a possibility to adjust and, if needed, to re-adjust the axial clearance directly at a power plant. The possibility to re-adjust has many benefits. The benefits include time saving and so longer energy production, higher efficiency when compared to turbines with suboptimal clearance and allows to improve a sealing of a turbine that is in use. Additionally, this allows to further adjust and readjust theaxial clearance by replacing a seal ring with another seal ring of a different size. This is beneficial as it allows to better perform said adjustment and readjustment. Specifically, there is no more limitation to what can be achieved in terms of adjustment and readjustment with the spacers only.

[0013] In examples, the plurality of spacers may be arranged in a plurality of holes circumferentially distributed along the circular groove. The spacers may be easily and precisely positioned within such holes. In examples, the seal ring is composed of a plurality of seal segments. For example, 2, 4, 6, 8 or a different number of segments. Preferably, 4 seal segments are used for a seal ring. The usage of seal segments facilitates transport and installation of the seal ring as well as clearance adjustment with the spacers. Specifically, each segment can be adjusted individually and no tension is created on the stator diaphragm by adjustments described above. Additionally, the use of seal segments allows adjusting and readjusting the axial clearance to a greater extent by using seal segments of different size. This is specifically beneficial when replacing spacers does not offer the adjustment or readjustment that is needed, and the final tuning of axial clearance has to be done by replacing seal segments. In examples, the seal ring is made of austenitic steel. This specifically improves the sealing of the circular groove. This prevents corrosion within the circular groove. A combination of segmented seal ring with the usage of austenitic steel is very beneficial. The austenitic steel prevents from the need to have sealing on each segment of the segmented seal ring.

[0014] In a further aspect, a steam turbine is provided comprising a stator diaphragm according to the previous aspect. The steam turbine can be a newly manufactured steam turbine or a used steam turbine. The steam turbine can also incorporate newly manufactured or refurbished parts as well as used parts. The used steam turbines are benefiting most of the invention as adjusting provided by the invention is the most complex for the used steam turbines. Specifically, the greatest challenges for used steam turbines is adjustments due to casing deformations that are typical for used steam turbines. Said casing deformations occur because of different factors known to a skilled person. This aspect proved to be versatile as it can be used on a reaction turbine, an impulse turbine, a reaction-impulse turbine, an axial turbine, and a radial turbine, radial-axial turbine. The reaction-impulse turbine includes both reaction blades and impulse blades. In yet a further aspect, a fossil, renewable-energy, waste- to-energy, combined-cycle or nuclear power plant comprising such a steam turbine is provided. This aspect further underlines the relevancy and versatility of the invention.

[0015] In some examples, the seal ring of the stator diaphragm is configured to provide a sealing between the stator diaphragm and a stationary part of the steam turbine, in particulara casing of the steam turbine. In examples, the stationary part of the steam turbine comprises a plurality of secondary spacers, such that the seal ring is arranged between the spacers of the stator diaphragm and the secondary spacers. Providing spacers at opposite axial sides of the seal ring can improve stability of the axial position of the seal ring. The secondary spacers can also be used to adjust and readjust the axial clearance.

[0016] In a further aspect, a method for arranging a seal ring between a seal face of a stator diaphragm and a stationary part of a turbine is provided. The method comprises providing a circular groove at the seal face, arranging a plurality of spacers in the circular groove and arranging the seal ring in the circular groove. The spacers axially position the seal ring in the circular groove.

[0017] In accordance with this aspect, the axial position of the stator diaphragm may easily be adjusted without the need for machining the seal face of the stator diaphragm. The method ensures that there is no need to transport a stator diaphragm multiple times between a machining shop and a power plant in order to assemble a steam turbine with a proper axial clearance. In examples, providing a circular groove includes machining the circular groove at a machine shop. In those examples, a stator diaphragm is transported only once to a power plant or a place where a steam turbine is needed to be assembled as adjustment is done at the power plant or the place where a steam turbine is needed to be assembled. The method may be used both in servicing or in upgrades, and when replacing a stator diaphragm with a new or refurbished stator diaphragm. The method can also be used for retrofitting existing stator diaphragms.

[0018] In some examples, the method may comprise removing the seal ring, replacing one or more of the spacers with differently sized spacers and positioning the seal ring in the circular groove. By choosing differently sized spacers, the axial position of the stator diaphragm may be easily adjusted and so the axial clearance can be easily adjusted. In some examples, arranging the seal ring in the circular groove comprises arranging at least one segment of the seal ring in the circular groove.

[0019] Elements of the aspects, aspects, examples and elements thereof can be combined together in any number and order to form new aspects and examples which are within the scope of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 schematically illustrates a cross-sectional view of a section of a steam turbine;

[0021] Figure 2 schematically illustrates a cross-sectional view of a portion of an example of a stator diaphragm;

[0022] Figure 3 schematically illustrates a portion of an example of an arrangement of a seal ring in a groove of a stator diaphragm;

[0023] Figure 4 illustrates an example of a stator diaphragm including a segment of a seal ring with four spacer;

[0024] Figure 5A illustrates a flow chart of an example of a method for providing a seal ring in a stator diaphragm; and

[0025] Figure 5B illustrates a flowchart of another example of a method for providing a seal ring in a stator diaphragm.DETAILED DESCRIPTION OF EXAMPLES

[0026] Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation only, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment.

[0027] It is intended that the present disclosure covers modifications and variations as come within the scope of the appended claims and their equivalents.

[0028] Figure 1 schematically illustrates an axial cross-section of a steam turbine 10. The steam turbine comprises a rotor and a stator arranged within a turbine casing 12. The rotor has a rotor shaft 50 configured to rotate about rotational axis 52. The rotor has a plurality of rotor stages, each stage comprising a ring or row of rotor blades arranged around and rotating with the rotor shaft. One rotor blade 30 of the first rotor stage has been indicated in figure 1 .

[0029] Upstream of every rotor stage, a stator diaphragm is arranged comprising a plurality of vanes. A first stage stator diaphragm 20 comprises a plurality of stator vanes 20B circumferentially arranged around the rotor shaft 50. The vanes of the stator diaphragms are configured to direct steam against the rotor blades.

[0030] In accordance with the present disclosure, a stator diaphragm 22 is provided which comprises a diaphragm body including a radially outer ring 22A, a radially inner ring 22C and a plurality of stator vanes 22B extending between the radially outer ring and the radially inner ring. The diaphragm body comprises an axial seal face.

[0031] The axial seal face is provided at a low pressure side of the radially outer ring 22A of stator diaphragm 22. An axial seal 40 is provided between the axial seal face of the stator diaphragm 22 and a portion of the turbine casing 12. The seal 40 is illustrated in more detail in figure 2.

[0032] The section of the steam turbine 20 may be a low pressure, intermediate pressure, or high pressure section of a steam turbine. The steam turbine 20 may be e.g. a reaction turbine or an impulse turbine. The steam turbine 20 may also include aspects of both reaction and impulse turbines. The steam turbine 20 may also include aspects of radial, axial turbines.

[0033] The steam turbine may form part of a power plant, e.g. a fossil, renewable-energy, waste-to-energy, combined-cycle or nuclear power plant. In any of such power plants, heated steam may be generated. Steam may expand through the multiple stages and set the rotor blades and rotor shaft 50 in rotation. The rotor shaft 50 may be operatively connected to a rotor of a generator. The generator (not illustrated) may convert the mechanical energy into electrical energy. The generator can be, for example, a 2-pole or a 4-pole generator. Electrical power generated by the generator may be provided to an electrical grid.

[0034] As illustrated in figure 2, the stator diaphragm 22 comprise a circular groove 45 at the axial seal face 42 of the diaphragm body. The stator diaphragm 22 further comprises a seal ring 44 and a plurality of spacers 46 arranged in the circular groove 45. The spacers 46 axially position the seal ring 44 in the circular groove 45. That is, the spacers 46 determine the axial position of the seal ring 44 and retain the seal ring 44 in its position.

[0035] More particularly, the length of the spacers 46 determines the axial position of the stator diaphragm 22. By choosing different spacers 46 with different lengths, the axial position of the stator diaphragm 22 is changed. Different lengths of spacers determine not only the axial position of the stator diaphragm 22, but also the extent to which the seal ring axially extends beyond the circular groove. In other words, the length of the spacers determines the axial clearance of the stator diaphragm in the turbine when the seal engages a component that is axially downstream from the stator diaphragm.

[0036] In use, suitable spacers 46 may be selected to position the stator diaphragm 22 as needed. Rather than multiple machining of the face of the stator diaphragm to fit the seal ring 44 in place with a proper axial clearance, spacers 46 with a different length may be selected, and which may be placed in the same holes 48. In some examples, a skilled person may select suitable spacers from a plurality of spacers with different standardized dimensions. A possibility to use standardized spacers has many benefits recognizable by a skilled person in this filed. All those benefits and their implications will not be listed here for the reasons ofbrevity. In other examples, a skilled person may in addition to a plurality of spacers with different standardized dimensions change the axial clearance by replacing the seal ring 44 with another seal ring 44 of a different size. It should be noted that this replacement is not possible without the usage of spacers 46. This replacement offers more possibilities to adjust the axial clearance.

[0037] In the example of figure 2, a plurality of holes 48 are distributed circumferentially along the circular groove 45. The holes 48 may be formed as local axial extensions of the circular groove 45. The holes 48 may be formed by drilling. The holes 48 may be shaped and sized such that the spacers 46 fit precisely in them. The spacers 46 may, depending on their length, axially protrude out of the holes 48. E.g. the smallest spacers may axially fit substantially exactly in the holes 48 and not significantly axially protrude from the holes. Larger spacers may axially protrude from the holes 48 and thereby “push” the seal ring outwards.

[0038] In the example of figure 2, the spacers 46 are axially arranged substantially completely between the seal ring 44 and the axial seal face of the diaphragm body and the seal ring 44 is welded to the spacers 46. The spacers 46 in this example may retain the seal ring 44 in position by the welded connection. The spacers 46 may be dowels or pins 46.

[0039] Alternative spacers such as screws or bolts may be used in other examples. The screw or bolts may be fixed in the holes 48 in the stator diaphragm e.g. with a threaded connection. An aspect of using bolts or screws is that the axial position of the seal ring 44 may be easily adjusted. Pins may be easier to use in case of a deviation between the plane of the stator diaphragm and the seal ring. In some examples, the bolts or screws may extend through the seal ring. Thereby the seal ring and bolts / screws are directly fixed in place.

[0040] In any of the previous examples, the stator diaphragm body and / or seal ring may be peened. Peening is a cold work process tending to expand the surface of the cold metal, thus inducing compressive stresses or relieving tensile stresses already present. It can also encourage strain hardening of the surface metal. Peening may be used to fix the seal ring in place.

[0041] Figure 3 schematically illustrates a portion of an example of an arrangement of a seal ring 44 in a groove 45 of a stator diaphragm 22. The stator diaphragm 22 comprises a radially inner ring 22C, a radially outer ring 22A, and a plurality of vanes 22B radially extending between the inner ring 22C and the outer ring 22A. The outer ring 22A comprises a circular groove 45 and a seal ring 44 is arranged in the groove 45. A plurality of spacers may be arranged in the circular groove 45.

[0042] In some examples, as illustrated in figure 3, the seal ring 44 may be composed of a plurality of ring segments 44A. In this particular example, the seal ring 44 is composed of 4 ring segments 44A, each of the ring segments 44A covering an arc of 902. In this specific example, four holes and corresponding spacers may be distributed along each of the ring segments i.e., in total 16 holes and spacers may be provided in this example.

[0043] In some examples, the seal ring of the stator diaphragm is configured to provide a sealing between the stator diaphragm and a stationary part of the steam turbine, in particular a casing of the steam turbine. In some non-illustrated examples, the stationary part of the steam turbine e.g. the turbine casing may comprise a plurality of secondary spacers, such that the seal ring 44 is arranged between the spacers of the stator diaphragm 22 and the secondary spacers. The stability of the seal ring and precise positioning of the stator diaphragm 22 can thereby be enhanced which leads to an improved axial clearance adjustment.

[0044] Figure 4 illustrates one of the segments 44A of a seal ring 44. This example relates to seal rings including seal segments. This particular example includes 4 seal segments. In other examples, different number of seal segments can be used, e.g., 2, 6, 8, 10, 12, 16 etc. In the example of Fig. 4, there are 4 pins used per each seal segment. Other spacers disclosed herein can be used in other examples. A combination of different spacers can be used in other examples.

[0045] Figure 5A illustrates a flow chart of an example of a method 100 for arranging a seal ring between a seal face of a stator diaphragm and a stationary part of a turbine. The method 100 comprises, at block 110, providing the stator diaphragm with a circular groove at the seal face. The method further comprises, at block 120, arranging a plurality of spacers in the circular groove and, at block 130, arranging the seal ring in the circular groove.

[0046] The axial position of the seal ring may easily be ensured without the need for machining the seal face of the stator diaphragm: by selecting suitably sized spacers (pins, dowels, screws, bolts or others), the position of the seal ring may be determined and changed.

[0047] Figure 5B illustrates a flow chart of another example of a method 200 for arranging a seal ring between a seal face of a stator diaphragm and a stationary part of a turbine. In this example, the seal ring may be substituting a previously used seal ring.

[0048] In examples, providing the stator diaphragm with a circular groove comprises machining the circular groove. Any machining of the stator diaphragm may take place in a factory and the need for machining as explained herein is reduced or even completely avoided in examples. In particular, any machining to adjust the position of the seal ring and stator diaphragm with respect to the remaining structure of the steam turbine may be reduced oravoided. This represents a significant time reduction in assembly, and repair. In examples, new and refurbished stator diaphragms may be combined in the same steam turbine (section).

[0049] In some examples, the method may be provided as a retrofit to an existing stator diaphragm. These examples are illustrated in figure 5B. In method 200, at block 210, a stator diaphragm is provided. In the next step, at block 220, the existing seal ring (which may be integrally formed or otherwise fixedly attached to the stator diaphragm) may be removed. The circular groove may then be machined at block 230, and a seal ring with suitably sized spacers may then be arranged in the circular groove (blocks 240, 250, similarly to what was illustrated in figure 5A).

[0050] In examples, the method may further comprise, at block 240, drilling a plurality of holes along the circular groove, and arranging the plurality of spacers in the plurality of holes. In this particular example, drilling of the holes may be carried out in factory and any machining may be avoided on site. Such drilling may also form part of a method for retrofitting commented on before.

[0051] The method may further comprise attaching the seal ring to the spacers. In some examples, the seal ring may be welded to the spacers. In other examples, the spacers may be screws or bolts, and the screws or bolts may extend through the seal ring.

[0052] In some examples, the method may further comprise peening the stator diaphragm. Peening may involve peening of the seal face of the stator diaphragm, and / or of the seal ring and / or the spacers. By small local deformations of these components, they may be firmly attached to each other and fixed in place.

[0053] In some examples, the method may further comprise removing the seal ring and replacing one or more of the spacers with differently sized spacers. The method may then also comprise positioning a (new) seal ring in the circular groove. With examples according to the present disclosure, the axial position of the seal ring with respect to the seal face of the stator diaphragm can be easily changed by selecting differently sized spacers. In particular, spacers with a different length may be selected.

[0054] In any of the herein illustrated examples, a seal ring of any suitable material may be used. Austenitic steel rings may be used as an example. Austenitic steel rings may expand in the groove at operational temperature and provide an effective seal.

[0055] This written description uses examples to disclose a teaching, including the preferred embodiments, and also to enable any person skilled in the art to put the teaching into practice, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include otherexamples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Elements from the various embodiments, aspects and examples described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments, aspects and examples in accordance with principles of this application which are part of the disclosure. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.

Claims

CLAIMS1. A stator diaphragm comprising a diaphragm body including a radially outer ring, a radially inner ring and a plurality of stator vanes extending between the radially outer ring and the radially inner ring, wherein the diaphragm body comprises an axial seal face and a circular groove at the axial seal face, and further comprising: a seal ring and a plurality of spacers arranged in the circular groove, wherein the spacers axially position the seal ring in the circular groove.

2. The stator diaphragm of claim 1 , wherein the plurality of spacers is arranged in a plurality of holes circumferentially distributed along the circular groove.

3. The stator diaphragm of any of claims 1 - 2, wherein the spacers are selected from a group including dowels, pins, bolts, and screws.

4. The stator diaphragm of claim 3, wherein the bolts or screws extend through the seal ring.

5. The stator diaphragm of any of claims 1 - 4, wherein the spacers have an axial length, and the axial length of the spacers determines the position of the seal ring.

6. The stator diaphragm of any of claims 1 - 5, wherein the circular groove is arranged at the axial seal face of the radially outer ring.

7. The stator diaphragm of any of claims 1 - 6, wherein the axial seal face of the stator diaphragm is at a low pressure side of the stator diaphragm.

8. The stator diaphragm of any of claims 1 - 7, wherein the seal ring is composed of a plurality of seal segments.

9. A steam turbine comprising the stator diaphragm of any of claims 1 - 8, wherein the steam turbine is at least one from a reaction turbine, an impulse turbine, an axial turbine, and a radial turbine.

10. The steam turbine of claim 9, wherein the seal ring of the stator diaphragm is configured to provide a sealing between the stator diaphragm and a stationary part of the steam turbine, and wherein the stationary part of the steam turbine comprises a plurality of secondary spacers, such that the seal ring is arranged between the spacers of the stator diaphragm and the secondary spacers.11 . A fossil, renewable-energy, waste-to-energy, combined-cycle or nuclear power plant comprising the steam turbine of any of claims 9 - 10.

12. A method for arranging a seal ring between a seal face of a stator diaphragm and a stationary part of a turbine, comprising: providing a circular groove at the seal face; arranging a plurality of spacers in the circular groove; and arranging the seal ring in the circular groove, wherein the spacers axially position the seal ring in the circular groove.

13. The method of claim 12, wherein providing a circular groove comprises machining the circular groove.

14. The method of claim 13, further comprising removing an existing seal ring prior to machining the circular groove.

15. The method of any of claims 12 - 14, wherein arranging a plurality of spacers in the circular groove includes: drilling a plurality of holes along the circular groove, and arranging the plurality of spacers in the plurality of holes.

16. The method of any of claims 12 - 16, wherein arranging the seal ring in the circular groove comprises arranging at least one segment of the seal ring in the circular groove.

17. The method of any of claims 12 - 17, further comprising: removing the seal ring; replacing one or more of the spacers with differently sized spacers; and positioning the seal ring in the circular groove.

18. The method of any of claims 12 - 18, further comprising: replacing the seal ring with differently sized seal ring; and positioning the differently sized seal ring in the circular groove 19. The stator diaphragm of any of claims 1 - 8 or the method of any of claims 12 - 18, wherein the seal ring is made of austenitic steel.

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