JPH056101U - Nozzle diaphragm of steam turbine - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention suppresses galling during assembly of a steam turbine, and causes uneven expansion and contraction of the casing during rapid start-up of the steam turbine or load change. Even if the side surface of the mounting groove is distorted or twisted, the sealing performance can be ensured in response to the deformation of the side surface of the mounting groove. [Structure] Mounting groove 2 bored in turbine casing 2
In the nozzle diaphragm 20 of the steam turbine having the outer ring portion 22 inserted in a, gaps CL1, CL2 are formed in the groove width direction between the mounting groove 2a and the outer ring portion 22, and the mounting groove 2a Elastically displaceable sealing means 30, 31, 32 for hermetically sealing the side sealing surface 27 are provided on the outer ring portion 22 side.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

  The present invention relates to a nozzle diaphragm used in a steam turbine, and particularly to an assembled diaphragm. Nozzle diaphragm that can be easily installed and improves the sealing performance. Regarding the improvement of the system.

[0002]

[Prior art]

  Generally, a steam turbine has a rotor rotatably supported in a turbine casing. , One end of the rotor is connected to the generator. In the turbine casing Nozzles (stator vanes) are installed on the turbine casing side of each turbine stage. A nozzle diaphragm for holding is provided with rotor blades in pairs on the rotor side. It A steam turbine consists of a turbine casing and a nozzle diaphragm. A stationary part and a rotating part composed of a rotor and a moving blade. Steam tar The turbine section of the bottle consists of a nozzle and blades located downstream of this nozzle. To be done.

[0003]   In a steam turbine, a nozzle and moving blades form a steam passage, and the steam is guided from the steam inlet. The energy of the incoming steam is transmitted to the rotor blades through the nozzle, and the rotational energy is transmitted to the rotor. Generate.

[0004]   The nozzle diaphragm is composed of an outer ring portion that holds the nozzle and an inner ring portion. The outer ring of the nozzle diaphragm is mounted in the turbine casing in the circumferential direction. It is fitted in the groove. On the other hand, the inner ring part is placed between the protrusions formed in the circumferential direction of the rotor. To be done. A seal part such as a labyrinth packing is located on the inner peripheral end of the inner ring facing the rotor. A material is provided to prevent steam from leaking from the rotor side.

[0005]   By the way, on the turbine casing side, the outer ring and the mounting groove form a seal. Is made. The seal part is affected by the pressure difference between the steam inlet pressure and the outlet pressure during operation. The downstream radial side surface of the outer ring portion is pressed toward the mounting groove side, and is pressed to the downstream radial side surface of the mounting groove. The close contact prevents steam from leaking from the outer ring side. Outer ring part The contact area of the contact surface with the mounting groove is determined so as to ensure a predetermined surface pressure.

[0006]   In addition, in order to prevent steam from leaking from the seal part, clear the space between the outer ring part and the mounting groove. It is desirable to set the lance as small as possible, so the clearance is almost zero. The nozzle diaphragm is attached to the turbine casing.   As described above, in the conventional steam turbine, the steam passage formed by the nozzle and the moving blades. Except for the other parts, steam is prevented from leaking and the sealing effect is improved, resulting in leakage loss. Is configured so that no

[0007]

[Problems to be solved by the device]

  Recent steam turbine plants have good start-up characteristics and can handle sudden load changes. Turbine performance that can follow even when required, and therefore when used under severe conditions There are many.

[0008]   Further, in the steam turbine, in particular, since the turbine casing has a large heat capacity, The entire turbine casing does not expand and contract uniformly in response to rapid heat changes, resulting in uneven Repeated expansion and contraction may cause distortion or twisting.   Especially in the turbine stage on the first stage where steam conditions (temperature, pressure, etc.) are severe, Creep deformation may occur in the casing over time, and The clearance is made close to zero and the outer ring part is fitted into the mounting groove to form the seal part. Contacting the mounting groove of the turbine casing with the outer ring of the nozzle diaphragm, There is a possibility that a gap will be created on the surface, steam will leak from this gap, and the sealing effect will be impaired. is there. In addition, the leaked steam causes erosion on the contact surface, increasing leakage loss, There is a risk of degrading the performance of the steam turbine.

[0009]   Moreover, when the clearance between the outer ring portion and the mounting groove is set to be close to zero, When the outer ring part is fitted into the mounting groove during assembly, galling occurs on the contact surface, There is a risk of impairing reliability.   Also, if the clearance is set large, the pressure difference between the upstream and downstream of the steam is small. There is a problem that the sealing performance cannot be exhibited sufficiently.

[0010]   The present invention was made in consideration of the above-mentioned circumstances, and when the steam turbine is assembled, In addition to suppressing the occurrence of galling, it can be used when the steam turbine starts rapidly or when the load changes. The turbine casing expands and contracts unevenly, causing distortion on the sides of the mounting groove. Even if kinks occur, the sealing performance can be ensured by responding to the deformation of the side surface of the mounting groove. The present invention aims to provide a nozzle diaphragm of a steam turbine. .

[0011]

[Means for Solving the Problems]

  The nozzle diaphragm of the steam turbine according to the present invention solves the above-mentioned problems. In order to provide an outer ring portion to be inserted into a mounting groove formed in the turbine casing, In the nozzle diaphragm of the steam turbine, between the mounting groove and the outer ring portion The air gap is formed in the groove width direction and the side sealing surface of the mounting groove is hermetically sealed. The elastically displaceable sealing means is provided on the outer ring portion side.

[0012]   The nozzle diaphragm of the steam turbine according to the present invention solves the above-mentioned problems. For this reason, it is inserted in the mounting groove drilled in the first stage of the turbine casing of the double-flow turbine. And an inner ring portion integrally provided with the outer ring portion via a nozzle. In the nozzle diaphragm of the air turbine, there is an empty space between the mounting groove and the outer ring portion. The gap is formed in the groove width direction, and the outer ring portion is biased in the groove width direction to attach An elastic member that hermetically seals the side sealing surface of the groove is provided in the inner ring portion. .

[0013]

[Action]

  The nozzle diaphragm of the steam turbine according to the present invention is provided between the mounting groove and the outer ring portion. Form a gap in the groove width direction and airtightly seal the side sealing surface of the mounting groove. Assembly of the steam turbine by elastically displaceable sealing means on the outer ring side The outer ring portion is smoothly inserted into the mounting groove at the time of skidding, and galling is suppressed. And tar Even if the side surface of the mounting groove is deformed due to uneven thermal expansion or contraction of the bottle casing, As the outer ring side can be brought into close contact with the mounting groove according to deformation, the sealing machine Fulfills Noh.

[0014]   Further, the nozzle diaphragm of the steam turbine according to the present invention includes a mounting groove, an outer ring portion, and A gap is formed in the groove width direction, and the outer ring is biased in the groove width direction for mounting. By providing the inner ring with an elastic member that hermetically seals the side sealing surface of the groove, When the air turbine is assembled, the outer ring portion is smoothly inserted into the groove to prevent galling.

[0015]

【Example】

  Hereinafter, refer to the attached drawings for the nozzle diaphragm of the steam turbine according to the present invention. I will explain.

[0016]   FIG. 1 is a perspective view of a steam turbine nozzle diaphragm according to a first embodiment of the present invention. FIG. 2 is an enlarged vertical sectional view showing the entire double-flow low-pressure turbine that has been inserted. FIG. 3 is an enlarged vertical sectional view of the main part shown in FIG. It is a partially broken perspective view showing the state where the 1st key member was attached.

[0017]   As shown in FIG. 1, the double-flow low-pressure turbine as a steam turbine has an external casing. An inner casing 2 is built in the bag 1. In the inner casing 2, there is a rotary energy A rotor 3 for generating gear is rotatably supported, and one end of the rotor 3 is a generator. (Not shown).

[0018]   At the center of the outer casing 1 and the inner casing 2, these casings 1 , 2 is penetrated to form a steam inlet 4, and the steam introduced from the steam inlet 4 is The flow is divided in the partial casing 2. At both ends of the inner casing 2, the steam outlet parts 5, 6 is provided, and the finished steam is discharged from the steam outlets 5 and 6 to a condenser (not shown). Will be issued.

[0019]   Inside the inner casing 2, turbine stages are configured in multiple stages, and each turbine stage has an internal Nozzles (stator vanes) 21, 21B to 21N, 21b to 21n are kept on the side of the casing 2 The nozzle diaphragms 20 and 20B to 20N and 20b to 20n are respectively installed. Be kicked. Further, the rotor blades 12A to 12N, 12 are provided on the rotor 3 side of each turbine stage. a to 12n are paired with the nozzles 21, 21B to 21N and 21b to 21n, respectively. Is provided.

[0020]   Then, the nozzle diaphragms 20, 20B to 20N, 20b to 20n are formed. Nozzles 21, 21B to 21N, 21b to 21n and moving blades 12A on the downstream side thereof 12N and 12a to 12n are paired with each other to form a paragraph of the steam turbine. It That is, the first stage on the side of the steam inlet 4 is the nozzle 21 of the diaphragm 20 and the moving blade 12A and 12a, and the Nth stage is nozzles 20N and 20n. The moving blades 12N and 12n are respectively configured.

[0021]   A plurality of mounting grooves 2A to 2N and 2a to 2n are formed in the inner casing 2 in the circumferential direction. Nozzle diaphragms 20 and 20 are formed in the mounting grooves 2A to 2N and 2a to 2n. B-20N and 20b-20n are respectively fitted. The rotor 3 has a plurality of protrusions. 11A to 11N and 11a to 11n are provided in the circumferential direction, and these protrusions 11A to 11 Moving blades 12A to 12N and 12a to 12n are planted in N and 11a to 11n, respectively. It

[0022]   The nozzle diaphragms 20, 20B to 20N, 20b to 20n have, for example, the first stage. Taking the constituent nozzle diaphragm 20 as an example, the outer ring portion 2 that holds the nozzle 21 2 and the inner ring portion 23. The inner ring portion 23 is formed between the protrusions 11A and 11a. The inner ring portion 23 facing the rotor 3 is disposed in a concave portion formed in A seal member (not shown) such as packing is provided to prevent steam from leaking from the rotor 3 side. To prevent.

[0023]   By the way, the outer ring portion 22 is shorter than the axial length of the mounting groove 2a as shown in FIG. When set and inserted into the mounting groove 2a, the specified axial clearances CL1, CL2 are secured, It is attached so that it can be displaced in any direction.

[0024]   Further, on the downstream side surface 22A of the outer ring portion 22, a side groove 30 is formed in the circumferential direction. A ring-shaped first key with a coil spring 31 as an elastic body in the circumferential groove 30 of The member 32 is attached. The sealing means includes the circumferential groove 30, the coil spring 31, and the first groove. It is composed of the key member 32.

[0025]   A protrusion 30 </ b> C is formed at the opening of the circumferential groove 30 so as to project inward of the circumferential groove 30. , The axial displacement of the first key member 32 is restricted to prevent the first key member 32 from coming off. First key part The downstream side surface 32 a of the material 32 is attached to the mounting groove 2 a by the spring biasing force of the coil spring 31. It is pressed against the downstream side surface 27. Therefore, the first key member 32 is below the mounting groove 2a. When it comes into close contact with the flow side surface 27, it seals the gap between the mounting groove 2a and the outer ring portion 22. It has become.

[0026]   As shown in FIG. 3, the first key member 32 is a key split piece that is divided into multiple pieces in the circumferential direction. It is composed of 32A to 32N. Each of the key split pieces 32A to 32N has a T-shaped axial section. It is formed in a letter shape. Further, each of the key split pieces 32A to 32N has a protrusion on each side surface in the axial direction. 33 and a sliding groove 34 which is slidably fitted to the protrusion 33 are formed. This The protrusion 33 and the sliding groove 34 are fitted to each other to form the first key member 32. It Each of the key split pieces 32A to 32N independently moves when it receives a force from the axial direction. Slides so that it can be displaced in any direction.

[0027]   The axial displacement amount M1 of each key split piece 32A to 32N is determined by the mounting groove 2a and the outer ring portion 2. It is set to be larger than the axial clearance (CL1 + CL2) between it and 2 (see Fig. 2). When the key split pieces 32A to 32N are displaced outward by a predetermined displacement amount M1. , The radial projections 35 of the key split pieces 32A to 32N are aligned with the projections 30C of the circumferential groove 30. It is regulated and prevents the key split pieces 32A to 32N from falling off from the circumferential groove 30. Growling.   Next, the operation of the nozzle diaphragm of the steam turbine according to the first embodiment will be described. And explain.

[0028]   When assembling the steam turbine, the nozzle diaphragm 20 is mounted in the mounting groove 2a. At this time, a predetermined gap (CL1 + CL2) is formed between the mounting groove 2a and the outer ring portion 22, Since the first key member 32 is elastically displaced inward of the circumferential groove 30, the outer ring portion 22 is attached. It is smoothly inserted into the groove 2a.

[0029]   The differential pressure (P1-P2) before and after the nozzle diaphragm 20 is small during operation of the steam turbine. Between the downstream side surface 22A of the outer ring portion 22 and the downstream side surface 27 of the mounting groove 2a. When CL2 is present, the first key member 32 is attached to the bottom of the mounting groove 2a by the coil spring 31. The flow side surface 27 is spring-biased and closely contacts. Therefore, the mounting groove 2a and the nozzle die The clearance CL2 between the flam 20 and the outer ring portion 22 is sealed, and Prevent steam leakage.

[0030]   In addition, the differential pressure (P1-P2) before and after the nozzle diaphragm 20 during operation of the steam turbine. Is large, the nozzle diaphragm 20 is pressed downstream, and the downstream side surface of the outer ring portion 22 is When 22A and the downstream side surface 27 of the mounting groove 2a come into close contact, the first key member 32 is rotated. The mounting groove 2 a and the outer ring portion 22 side of the nozzle diaphragm 20 are housed in the side groove 30. Sealed.

[0031]   Further, due to uneven thermal expansion and contraction of the inner casing 2, the downstream side of the mounting groove 2a Even if the side surface 27 is deformed, the key split pieces 32A to 32N are respectively deformed according to the deformation. The spring is independently biased to the downstream side surface 27 of the mounting groove 2a. For this reason, even if Even if the downstream side surface 27 of the groove 2a is deformed, it is possible to seal according to the deformation. In this way, the sealing function is reliably achieved over the entire circumference of the sealing surface.

[0032]   Further, the first key member 32 is constantly pressed against the downstream side surface 27 of the mounting groove 2a. Since they are in close contact with each other, the transition occurs from start to stop of the steam turbine Even if the downstream side surface 27 of the mounting groove 2a is changed, it follows the change and is excellent. Exhibits sealing performance.   FIG. 4 shows a modified example of the first embodiment, which is the same part as that of FIGS. 1 to 3. Alternatively, the corresponding parts are denoted by the same reference numerals and the description thereof is omitted.

[0033]   A side groove 40 is formed on the downstream side surface 22A of the outer ring portion 22 in the circumferential direction. A ring-shaped second key member 4 is provided in the groove 40 via a coil spring 41 as an elastic body. 2 is attached. The sealing means includes the annular groove 40, the coil spring 41, and the second key. It is composed of members.

[0034]   The downstream end surface 42a of the second key member 42 is driven by the spring biasing force of the coil spring 41. It is pressed against the downstream side surface 27 of the mounting groove 2a. Therefore, the second key member 42 When closely attached to the downstream side surface 27 of the mounting groove 2a, the mounting groove 2a and the outer ring portion 22 are sealed. It is supposed to do.

[0035]   The second key member 42 is a key split piece 42A to 42N divided into a large number in the circumferential direction. It is composed of Each of the key split pieces 42A to 42N has an axial section as shown in FIG. It is formed in a D shape. The key split pieces 42A to 42N are the same as those in the first embodiment. In the same manner as above, each side surface in the axial direction is provided with a locking portion (not shown) slidable in the axial direction. I am. These locking portions are fitted with each other to form the second key member 42. Therefore, the key split pieces 42A to 42N become independent when they receive a force from the axial direction. Then, it slides so that it can be displaced in the axial direction.

[0036]   The displacement amount M2 by which the key split pieces 42A to 42N are displaced in the axial direction is equal to the mounting groove 2a. It is set to be larger than the axial gap (CL3 + CL4) with the outer ring portion 22. That In each of the key split pieces 42A to 42N, the downstream end surface 42a is on the downstream side of the mounting groove 2a. The outer ring 22 is pressed against the surface 27 and is moved relative to the outer ring 22 in accordance with the axial displacement of the outer ring 22. It slides in the circumferential groove 40 so as to be displaceable.   Next, the operation of the nozzle diaphragm of the steam turbine according to the above modification will be explained. Reveal

[0037]   When assembling the steam turbine, the nozzle diaphragm 20 is mounted in the mounting groove 2a. At this time, a predetermined gap (CL3 + CL4) is formed between the mounting groove 2a and the outer ring portion 22, Since the second key member 42 is elastically displaced inward of the circumferential groove 40, the outer ring portion 22 is attached. It is smoothly inserted into the groove 2a, and galling is suppressed.

[0038]   The differential pressure (P1-P2) before and after the nozzle diaphragm 20 is small during operation of the steam turbine. Between the downstream side surface 22A of the outer ring portion 22 and the downstream side surface 27 of the mounting groove 2a. When CL4 is present, the second key member 42 on the outer ring portion 22 side is formed by the coil spring 41. The downstream side surface 27 of the mounting groove 2a is spring-biased and closely contacts. Therefore, the mounting groove 2a The outer ring portion 22 side of the nozzle diaphragm 20 is sealed.

[0039]   In addition, the differential pressure (P1-P2) before and after the nozzle diaphragm 20 during operation of the steam turbine. Is large, the nozzle diaphragm 20 is pressed downstream, and the downstream side surface of the outer ring portion 22 is When 22A and the downstream side surface 27 of the mounting groove 2a come into close contact, the second key member 42 is rotated. The mounting groove 2 a and the outer ring portion 22 side of the nozzle diaphragm 20 are housed in the side groove 40. Sealed.

[0040]   Further, due to uneven thermal expansion and contraction of the inner casing 2, the downstream side of the mounting groove 2a Even if the radial side surface 27 is deformed, the key split pieces 42A to 42N are deformed according to the deformation. Each of them is independently spring-biased on the downstream side surface 27 of the mounting groove 2a. For this reason, Even if the downstream side surface 27 of the mounting groove 2a is deformed, the sealing is surely performed according to the deformation. Perform performance.

[0041]   It should be noted that, in both the above embodiment and the modified example, the nozzle used in the first stage of the steam turbine Although the diaphragm has been described, it is not limited to this, and other turbine stages may be used. It goes without saying that it is also applicable to loss.

[0042]   Next, the diaphragm of the steam turbine according to the second embodiment of the present invention will be described with reference to FIG. Will be described with reference to. The same parts as those in FIGS. The reference numerals are given and the description thereof is omitted.

[0043]   This steam turbine is a double-flow turbine, and the turbine casing is The inner casing 2 is housed in the part casing, and the tar is placed in the inner casing 2. Bin paragraph is accommodated. Of these, the interior of the stationary part that constitutes the first-stage turbine stage Mounting grooves 2a and 2b are formed in the casing 2 in the circumferential direction, and the mounting grooves 2a and 2b are formed. A nozzle diaphragm 50 is inserted in the. Nozzle diaphragm 50 The outer ring portions 52, 52 holding the ring 51 and the inner ring portion 54.

[0044]   The inner ring portion 54 is disposed in the concave portion of the rotor 3, and the inner circumference of the inner ring portion 54 facing the rotor 3 A seal member (not shown) is provided on the side to prevent steam from leaking from the rotor 3 side. ing.

[0045]   By the way, the outer ring portions 52, 52 are attached to the mounting grooves 2a, 2b, respectively, as shown in FIG. It is set shorter than the groove width of. Therefore, the outer ring portions 52, 52 are attached to the mounting grooves 2a, 2b. Once inserted and installed, ensure a certain axial clearance CL5, CL6 on the upstream side. Growling.

[0046]   In addition, in the center of the inner ring portion 54, a metal as an elastic member composed of a bellows for high temperature is used. A generic bellows 55 is provided in a double-tube structure. Downstream side surface 52a of the outer ring portions 52, 52 , 52b, when high-pressure steam is introduced from the steam inlet portion 4 into the inner casing 2. , The metal bellows 55 elastically expands due to the pressure difference between the upstream and downstream of the steam passage, and the mounting groove 2 It is pressed against the downstream side surfaces 26 and 27 of a and 2b, respectively. Therefore, the outer ring portion 52 , 52 is brought into close contact with the downstream side surfaces 26, 27 of the mounting grooves 2a, 2b due to the differential pressure, A seal is provided between the groove 2a, 2b and the outer ring portion 52, 52.   Next, the operation of the nozzle diaphragm of the steam turbine according to the second embodiment will be described. And explain.

[0047]   When installing the steam turbine, attach the nozzle diaphragm 50 to the mounting grooves 2a and 2b. When mounting, a predetermined clearance CL5, CL6 is provided between the mounting grooves 2a, 2b and the outer ring portions 52, 52. The outer ring portions 52, 52 are smoothly inserted into the mounting grooves 2a, 2b, Is suppressed.

[0048]   Large and small differential pressure (P1-P2) before and after the nozzle diaphragm 50 during operation of the steam turbine Irrespective of the above, the downstream side surfaces 52a, 52b of the outer ring portions 52, 52 and the mounting grooves 2a, 2b And the downstream side surfaces 26 and 27 of each of them are in close contact with each other. For this reason, Prevent the leakage of steam.

[0049]   The spring constant of the coil spring and the bellow The elastic constant is determined by the differential pressure (P1-P2) before and after the nozzle diaphragm. Sufficient surface pressure is ensured even during rated operation of the bottle.

[0050]   Further, in each of the above-described embodiments and modifications, the outer ring portion side is located on the downstream side surface in the mounting groove. Because they are in close contact at all times, there is a loss due to fluctuations in the steam pressure introduced into the steam turbine. Even if the diaphragm is vibrated, the vibration can be suppressed.

[0051]

[Effect of device]

  As described above, the nozzle diaphragm of the steam turbine according to the present invention is A gap is formed in the groove width direction between the groove and the outer ring part, and the side groove of the mounting groove is sealed. By providing the elastically displaceable sealing means that seals the surface airtight on the outer ring side , The outer ring part is smoothly inserted into the groove when the steam turbine is installed, so galling is suppressed. It can be stopped and the workability at the time of assembling the steam turbine can be improved. .

[0052]   Furthermore, even if the side surface of the mounting groove is deformed due to uneven thermal expansion or contraction of the casing, Since the outer ring side can be brought into close contact with the mounting groove according to the deformation, sealing performance Performance, reduce steam turbine leakage loss, and improve steam turbine The performance of can be improved.

[0053]   Further, the nozzle diaphragm of the steam turbine according to the present invention includes a mounting groove, an outer ring portion, and A gap is formed in the groove width direction, and the outer ring portion is biased in the groove width direction. By providing the inner ring with an elastic member that hermetically seals the side sealing surface of the mounting groove , Assembling the nozzle diaphragm used in the first stage of the double-flow low-pressure turbine in the casing When attaching, the outer ring part is smoothly inserted into the groove, so it is possible to prevent galling. Therefore, the workability when assembling the steam turbine can be improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an entire steam turbine in which a nozzle diaphragm of a steam turbine according to a first embodiment of the present invention is incorporated.

FIG. 2 is an enlarged vertical sectional view of an essential part showing an enlarged part of FIG.

FIG. 3 is a partially cutaway perspective view showing a state in which a first key member as a sealing means is attached to the nozzle diaphragm of FIG.

FIG. 4 is an enlarged vertical sectional view of an essential part showing an essential part of a modified example of the first embodiment.

FIG. 5 is an enlarged vertical sectional view of an essential part showing an enlarged essential part of a nozzle diaphragm of a steam turbine according to a second embodiment of the present invention.

[Explanation of symbols]

1 Outer casing 2 Inner casing 2A ~ 2N, 2a ~ 2n mounting groove 20,50 nozzle diaphragm 22, 52, 52 Outer ring part 23,54 Inner ring part CL1 to CL6 Gap 30, 40 Circumferential groove (seal means) 31, 41 Coil spring (seal means) 32 First key member (sealing means) 42 Second key member (sealing means) 55 Metal bellows (elastic member)

Claims (2)

[Scope of utility model registration request] 1. In a nozzle diaphragm of a steam turbine having an outer ring portion inserted into a mounting groove formed in a turbine casing, a gap is formed in the groove width direction between the mounting groove and the outer ring portion. In addition, a nozzle diaphragm of a steam turbine, characterized in that elastically displaceable sealing means for hermetically sealing the side sealing surface of the mounting groove is provided on the outer ring portion side. 2. A nozzle diaphragm for a steam turbine, comprising: an outer ring portion inserted into a mounting groove formed in the first stage of a turbine casing of a double-flow turbine; and an inner ring portion integrally provided with the outer ring portion via a nozzle. In the elastic member, a space is formed between the mounting groove and the outer ring portion in the groove width direction, and the outer ring portion is biased in the groove width direction to hermetically seal the side sealing surface of the mounting groove. A nozzle diaphragm for a steam turbine, wherein the nozzle diaphragm is provided on the inner ring portion.