JP2014118909A - Turbine - Google Patents

Abstract

An object of the present invention is to move in the axial direction of thermal expansion during normal operation and to reduce the thrust force applied to the thrust bearing in the event of an earthquake to prevent damage to the intermediate bearing stand.
SOLUTION: A rotor 1, a casing 11, a thrust bearing 8 that receives an axial load of the rotor 1, an intermediate bearing base 10 that fixes a thrust bearing housing 9 including the thrust bearing 8 as a basis, an axial fixing key 15, and a rotor 1, a rotor 4, a casing 14, a thrust bearing 17 that receives an axial load of the rotor 4, a thrust bearing housing 18 that accommodates the thrust bearing 17, and a casing 14. A connecting portion 33 that is connected in the direction, and a damper mechanism 19 that is provided between the vehicle compartment 14 and the foundation and that can move the vehicle compartment 14 for thermal expansion during normal operation and attenuate axial movement in the event of an earthquake.
[Selection] Figure 1

Description

  The present invention relates to a turbine.

  Thrust bearings are provided on the rotating shafts of various turbines such as steam turbines and gas turbines. The thrust bearing is a bearing that supports axial thrust forces in a plurality of turbine rotors and generator rotors that are interconnected by a coupling.

  The thrust bearing serves as a starting point of axial elongation due to the heat of the turbine rotor. The turbine rotor, which is a rotating part, thermally expands forward and rearward from the thrust bearing as a starting point.

  On the other hand, a casing is provided as a stationary part for wrapping steam that has flowed in and covers the turbine blades. A high-pressure casing is provided as a high-pressure turbine casing, and an internal casing into which steam for rotating the turbine flows and an external casing containing steam exhausted from the internal casing are provided as low-pressure turbine casings. Yes.

  The high-pressure casing thermally expands forward from an intermediate bearing stand provided between the high-pressure casing and the low-pressure casing, but does not thermally expand rearward. The low-pressure external compartment is thermally expanded forward and backward from an axially fixed key provided at the center in the axial direction of the low-pressure external compartment and fixed to the foundation.

  Below, the literature name which disclosed the thrust bearing in the conventional turbine is described.

JP-A-10-299765 JP-A-4-209903

  Patent Document 1 describes a thrust bearing in which a damper mechanism including a piston and sealed oil is interposed between a thrust pad and a thrust bearing casing in the thrust bearing. With such a configuration, the thrust force is absorbed by the damper mechanism when an earthquake occurs, and the thrust force acting on the pad is alleviated.

  Patent Document 2 describes a turbine in which a plurality of turbine rotors are provided with thrust bearings, and turbine turbines adjacent in the axial direction are coupled via a flexible shaft coupling that absorbs axial elongation. With this configuration, the difference in axial extension between the turbine rotor and the stationary part during thermal expansion is reduced, and the number of packing teeth is increased to improve turbine efficiency.

  By the way, when an earthquake exceeding the magnitude assumed at the time of design occurs, the thrust bearing receives an impact force in the axial direction from the turbine rotor, and there is a possibility that the intermediate bearing base including the thrust bearing may be damaged. The repair takes a long time and hinders the early restoration of turbine equipment after the earthquake.

  Further, as described above, a large impact force is applied to the thrust bearing when an earthquake occurs. For this reason, if the intermediate bearing stand that is the starting point in the axial direction of the turbine rotor is damaged, the axial movement of the turbine rotor cannot be constrained, and the turbine rotor and the stationary part may be contacted and damaged. . In that case, a large-scale repair such as replacement of blades and packing is required.

  In order to solve such a problem, it is possible to install a turbine having a high design seismic intensity. However, this requires time and cost for development. In order to reduce such time and cost, it is expected to examine and take measures against the thrust bearing.

  As described above, the thrust bearing is the starting point for the axial extension of the turbine rotor. For this reason, if a thrust bearing is separately installed in addition to the conventional thrust bearing, the axial extension of the turbine rotor is restricted and a new problem arises.

  In the thrust bearing described in Patent Document 1, the thrust force applied to the thrust bearing is reduced by providing a damper mechanism between the thrust pad and the thrust bearing casing. However, the influence on the turbine performance is described. It has not been.

  In the turbine described in Patent Document 2, thrust bearings are provided on a plurality of turbine rotors, and adjacent turbine rotors are coupled with flexible shaft joints to absorb axial elongation. There is no description on the structure and effect of preventing damage around the bearings in.

  In view of the above circumstances, the present invention moves in accordance with the turbine rotor with respect to the axial extension during thermal expansion, and is applied to a thrust bearing when an excessive earthquake exceeding the scale assumed at the time of design occurs. An object of the present invention is to provide a turbine capable of reducing the thrust force and preventing damage to the intermediate bearing stand.

The turbine of the present invention is
A first rotor;
A first passenger compartment provided in the first rotor;
A first thrust bearing that receives an axial load of the first rotor;
A first thrust bearing housing enclosing the first thrust bearing;
A fixing device for fixing the first thrust bearing housing to a foundation;
A second rotor coupled to the first rotor or coupled to the first rotor via at least one other rotor;
A second passenger compartment provided in the second rotor;
A second thrust bearing that receives an axial load of the second rotor;
A second thrust bearing housing that houses the second thrust bearing;
A connecting portion for connecting the second thrust bearing housing and the second casing in an axial direction;
It is provided between the second casing and the foundation, and is capable of moving in the axial direction with respect to the foundation for thermal expansion during normal operation. An axial movement restraining device for attenuating the movement of the passenger compartment in the axial direction;
It is characterized by providing.

  According to the turbine of the present invention, the axial movement at the time of thermal expansion moves following the turbine rotor, and when an excessive earthquake exceeding the scale assumed at the time of design occurs, the thrust bearing is applied. It is possible to reduce the thrust force and prevent damage to the intermediate bearing stand.

It is a longitudinal cross-sectional view which shows the structure of the turbine by Embodiment 1 of this invention. It is a longitudinal cross-sectional view which shows the structure of the turbine by Embodiment 2 of this invention. It is a longitudinal cross-sectional view which shows the structure of the packing used with the turbine by a reference example. It is a longitudinal cross-sectional view which shows the structure of the packing used with the turbine by Embodiment 3 of this invention. It is a longitudinal cross-sectional view which shows the structure of the turbine by the said reference example. It is the elements on larger scale which show in detail the structure of the peripheral part of the intermediate bearing stand used with the turbine by the reference example.

  First, before describing an embodiment of the present invention, a turbine as a reference example will be described with reference to FIG.

  As rotating parts, the high pressure turbine rotor 1 in the high pressure casing 11, the low pressure A turbine rotor 2 in the low pressure A external casing 12, the low pressure B turbine rotor 3 in the low pressure B external casing 13, and the low pressure C turbine in the low pressure C external casing 14. The rotor 4 and the generator rotor 5 of the generator 34 are coupled by couplings 6a to 6d, respectively.

  On the other hand, a thrust bearing 8 that fixes the axial direction of the high-pressure turbine rotor 1 by sandwiching a thrust collar 7 formed integrally with the high-pressure turbine rotor 1 as a stationary part, a thrust bearing housing 9 that includes the thrust bearing 8, and a thrust bearing An intermediate bearing stand 10 is provided for fixing the housing 9 to a foundation (not shown). Further, as a stationary part, a high-pressure casing 11, a low-pressure A external casing 12, a low-pressure B external casing 13, and a low-pressure C external casing 14 are provided, and the axial directions of the casings 11 to 14 are axially fixed keys 15a. , 15b and 15c.

  The configuration of the peripheral portion of the intermediate bearing stand 10 is shown in FIG. As described above, the thrust bearing 8 fixes the axial direction of the high-pressure turbine rotor 1 by sandwiching the thrust collar 7 formed integrally with the high-pressure turbine rotor 1, and the thrust bearing housing 9 includes the thrust bearing 8. The intermediate bearing base 10 is fixed to the foundation 20 by the intermediate bearing base axial direction fixing key 21, and thereby the axial direction of the thrust bearing housing 9 is fixed. Here, the intermediate bearing base 10 for fixing the thrust bearing housing 9 to the foundation 20 and the intermediate bearing base axial direction fixing key 21 correspond to a fixing device.

  The thrust bearing 8 is a starting point of axial extension due to the heat of the turbine rotors 1 to 4 that are rotating parts. The thrust bearing 8 is the starting point (leftward in the figure) and the rear (rightward in the figure). ) Freely expand without being restrained. In particular, the rear portions of the turbine rotors 2 to 4 are greatly expanded due to the long axial length.

  The high-pressure casing 11 which is a stationary part thermally expands forward starting from an intermediate bearing stand 10 provided between the high-pressure casing 11 and the low-pressure A outer casing 12, but does not thermally expand rearward.

  Furthermore, the low-pressure A external casing 12, the low-pressure B external casing 13, and the low-pressure C external casing 14, which are stationary parts, are provided at the center in the axial direction of the respective casings and are axially fixed keys 15a fixed to the foundation. , 15b, and 15c, starting from the front and rear, respectively. That is, since each of the passenger compartments 12 to 14 thermally expands forward and rearward from the central portion, each thermal expansion is small.

  For this reason, the difference of thermal expansion becomes large behind the turbine rotors 2 to 4 of the rotating portion, particularly between the low pressure C turbine rotor 4 and the low pressure C external casing 14.

  In addition, when an earthquake exceeding the scale assumed at the time of design occurs in such a configuration, all of the axial impact forces from the turbine rotors 1 to 4 are applied to one thrust bearing 8. For this reason, the peripheral part of the intermediate bearing stand 10 incorporating the thrust bearing 8 may be damaged.

  When two or more thrust bearings 8 are provided, the axial impact force can be dispersed. However, since the thrust bearing 8 is the starting point of the axial extension of the turbine rotors 1 to 4, when a new thrust bearing is installed in addition to the thrust bearing 8, the turbine rotor 1 is fixed to the foundation in the new thrust bearing. An axial elongation of ~ 4 is a problem.

  Next, a turbine according to an embodiment of the present invention will be described with reference to the drawings.

(1) Embodiment 1
A turbine according to Embodiment 1 of the present invention will be described with reference to FIG.

  In the turbine according to the above reference example shown in FIG. 5, one thrust bearing 8 is provided, and an axially fixed key 15 c fixed to the foundation is provided at the axially central portion of the low-pressure C turbine rotor 14. .

  On the other hand, in the first embodiment, a thrust bearing 17 is newly provided in addition to the thrust bearing 8. The thrust bearing 17 supports the axial direction of the low-pressure C turbine rotor 4 by sandwiching a thrust collar 16 formed integrally with the low-pressure C turbine rotor 4, and the thrust bearing housing 18 includes the thrust bearing 17. The thrust bearing housing 18 is connected to the low-pressure C external casing 14 by a connecting portion 33 without being fixed to the foundation.

  Furthermore, in the first embodiment, a damper mechanism 19 is provided for the low-pressure C outer casing 14 in place of the axial direction fixing key 15c. The damper mechanism 19 corresponds to an axial movement restraining device that restrains axial movement relative to the foundation of the low-pressure C external casing 14 when an earthquake occurs.

  Specifically, the damper mechanism 19 has a damping force that acts as a resistance component and converges displacement against a periodic vibration in which a thrust force increases rapidly in the axial direction in a short time when an earthquake occurs. Type shock absorbers, gas-filled type shock absorbers, etc.

  Since such a damper mechanism 19 is provided between the foundation and the low-pressure C external casing 14, unlike the axial direction fixed key during normal operation, the low-pressure C external casing 14 is opposed to the foundation during normal operation. Does not have the effect of fixing. For this reason, the low pressure C external casing 14 is freely thermally expanded without being constrained with respect to the foundation.

  As described above, in the turbine according to the reference example, the center portion is based on the center by the low-pressure C turbine rotor 4 that is long in the axial direction from the thrust bearing 8 that is the starting point of thermal expansion and that is largely thermally expanded, and the axial fixing key 15c. On the other hand, the difference in thermal expansion between the low pressure C external casing 14 and the fixed low pressure C external casing 14 increases.

  On the other hand, according to the first embodiment, the low-pressure C external casing 14 is not fixed to the foundation by the damper mechanism 19 and freely expands thermally. Is reduced.

  On the other hand, when an earthquake occurs, the damper mechanism 19 exerts a damping force that converges the periodic vibration in the axial direction as described above. Thereby, the displacement with respect to the foundation of the low-pressure C external casing 14 is attenuated.

  As a result, two thrust bearings, in which a thrust bearing 17 newly provided in addition to the thrust bearing 8 used in the reference example is added in the event of an earthquake, distributes excessive thrust force in the axial direction to one The impact force per hit can be reduced. Thereby, the load applied to the intermediate bearing stand 10 that fixes the thrust bearing 8 to the foundation is reduced, and damage can be prevented.

  As described above, according to the first embodiment, the newly provided thrust bearing 17 moves freely following the low-pressure C turbine rotor 4 without being restricted by the axial expansion during thermal expansion. Reduce the difference between the rotating part and the stationary part, absorb the axial movement of the low-pressure C external casing 14 when an excessive earthquake occurs, and share the thrust force with the thrust bearing 8 to prevent damage Is possible.

(2) Embodiment 2
A turbine according to a second embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same component as the said Embodiment 1, and the overlapping description is abbreviate | omitted.

  In the first embodiment, the thrust bearing 17 and the damper mechanism 19 are provided in one low-pressure C external casing 14 that is the farthest from the thrust bearing 8 that is the starting point of thermal expansion in the axial direction of the turbine rotors 2 to 4. ing.

  On the other hand, in the second embodiment, the thrust bearings 23, 26, and 17 and the damper mechanisms 19a, 19b, and 19c are provided in all the low-pressure A external compartment 12, the low-pressure B external compartment 13, and the low-pressure C external compartment 14, respectively. In the second embodiment, the thrust bearings and the damper mechanisms are provided in all the low-pressure external compartments 12 to 14, but it is not always necessary to provide them in all the low-pressure external compartments. It may be provided in a single low-pressure external compartment.

  More specifically, in the same manner as in the first embodiment with respect to the low-pressure C external casing 14, the thrust bearing 17 sandwiches the thrust collar 16 formed integrally with the low-pressure C turbine rotor 4, so that the low-pressure C turbine rotor 4 The axial bearing is supported, and the thrust bearing housing 18 includes the thrust bearing 17, and the thrust bearing housing 18 is fixed to the low-pressure C external casing 14 by the connecting portion 33c without being fixed to the foundation. In addition, a damper mechanism 19c is provided for the low-pressure C outer casing 14 in place of the axially fixed key.

  Similarly, with respect to the low pressure A external casing 12, the thrust bearing 23 supports the axial direction of the low pressure A turbine rotor 2 by sandwiching a thrust collar 22 formed integrally with the low pressure A turbine rotor 2, and a thrust bearing housing 24 Includes the thrust bearing 23, and the thrust bearing housing 24 is fixed to the low pressure A external casing 12 by the connecting portion 33a without being fixed to the foundation. In addition, a damper mechanism 19a is provided for the low pressure A external casing 12 in place of the axially fixed key.

  Further, with respect to the low pressure B outer casing 13, the thrust bearing 26 supports the axial direction of the low pressure B turbine rotor 3 by sandwiching a thrust collar 25 formed integrally with the low pressure B turbine rotor 3, and the thrust bearing housing 27 is provided. The thrust bearing 26 is included, and the thrust bearing housing 27 is fixed to the low-pressure B external casing 13 by the connecting portion 33b without being fixed to the foundation. In addition, a damper mechanism 19b is provided for the low-pressure B external casing 13 instead of the axially fixed key.

  As with the damper mechanism 19 described in the first embodiment, the damper mechanisms 19a to 19c act as a resistance component against the periodic vibration in which the thrust force suddenly increases in the axial direction in a short time when an earthquake occurs. Has a damping force to converge.

  Since such damper mechanisms 19a to 19c are provided between the foundation and the respective external compartments 12 to 14, the function of fixing the external compartments 12 to 14 to the foundation is provided during normal operation. do not have. For this reason, any of the external compartments 12 to 14 is freely thermally expanded without being constrained with respect to the foundation.

  In the turbine rotors 2 to 4, only the thrust bearing 8 is the starting point of thermal expansion, and is freely thermally expanded rearward. There is almost no difference in thermal expansion between the turbine rotors 2 to 4 and the external casings 12 to 14 that are not fixed during normal operation.

  When an earthquake occurs, the damper mechanisms 19a to 19c attenuate the displacements of the bases of all the external compartments 12 to 14.

  As a result, in addition to the thrust bearing 8, three thrust bearings 23, 26, and 17 newly provided disperse excessive thrust force in the axial direction and greatly reduce the impact force per unit. Can do. Thereby, the load applied to the intermediate bearing stand 10 that fixes the thrust bearing 8 to the foundation is reduced, and damage can be prevented.

  As described above, according to the second embodiment, the newly provided thrust bearings 23, 26, and 17 follow the turbine rotors 2 to 4 without being constrained by the axial expansion during thermal expansion. And the difference between the rotating part and the stationary part is reduced to almost zero, and when an excessive earthquake occurs, the axial movement of the external casings 12 to 14 is absorbed, and the thrust bearing 8 and the thrust force are reduced to 1/4. It is possible to prevent damage by sharing them one by one.

(3) Embodiment 3
A turbine according to Embodiment 3 of the present invention will be described with reference to FIGS. 3 and 4. In addition, description is abbreviate | omitted about the location which overlaps with the said Embodiment 1,2.

  The turbine according to the third embodiment includes the following configuration related to packing in addition to the configuration of the turbine according to any of the first or second embodiments.

  FIG. 3 shows a configuration of packing in a turbine as a reference example. Leakage steam is generated between the rotating part 28 and the stationary part 29 in the turbine. The leaked steam does not work on the turbine, so if the amount of leak increases, the performance of the turbine decreases.

  Therefore, in order to prevent or suppress such leaked steam, a packing 30 is provided in the fluid leakage preventing portion in the stationary portion 29. The packing 30 includes a plurality of packing teeth 31 so as to face the rotating portion 28.

  Here, in the turbine according to the reference example, as shown in FIG. 3, the rotating portion 28 has a structure with a flat surface. Packing teeth 31 are provided with a uniform length on the packing 30 of the stationary part 29 so that the surface faces the flat rotating part 28.

  On the other hand, in the turbine according to the third embodiment, as shown in FIG. 4, a stepped rotor groove 32 is formed on the surface of the rotating portion 28 facing the packing teeth 31 a and 31 b of the packing 30 of the stationary portion 29. Has been. The packing teeth 31 a and 31 b have different lengths so as not to interfere with each other according to the step of the rotor groove 32. That is, the packing teeth 32a facing the convex portions 32a of the rotor groove 32 are short, and the packing teeth 32b facing the concave portions 32b are long.

  Since the rotor groove 32 having such a step and the packing teeth 31a and 31b having different lengths according to the step are provided in the fluid leakage preventing portion, the amount of leaked steam is higher than that of the reference example according to the third embodiment. Can be reduced.

  Incidentally, in the turbine according to the reference example shown in FIG. 5, and further in the first embodiment shown in FIG. 1 and the turbine according to the second embodiment shown in FIG. 2, the low pressure A corresponding to the rotating portion 28. The turbine rotor 2, the low pressure B turbine rotor 3, and the low pressure C turbine rotor 4 extend in the axial direction with a thrust bearing 8 installed in the high pressure turbine rotor 1 as a starting point.

  On the other hand, in the turbine according to the reference example shown in FIG. 5, the low pressure A external casing 12, the low pressure B external casing 13, and the low pressure C external casing 14 corresponding to the stationary portion 29 are axially fixed keys 15 a and 15 b, respectively. 16c, the axial extension difference between the rotating part 28 and the stationary part 29 increases as the distance from the thrust bearing 8 increases. For this reason, the difference in the axial extension between the low-pressure C turbine rotor 4 and the low-pressure C external casing 14 is the largest.

  In such a portion where the difference in the elongation in the axial direction is large, if the configuration having the rotor groove 32 as shown in FIG. 4 is adopted, the packing teeth 31a and 31b having different lengths according to the unevenness of the rotor groove 32 and the rotor The positional relationship between the convex portion 32a and the concave portion 32b of the groove 32 is shifted, and the packing teeth are brought into contact with each other. As a result, in the turbine according to the reference example, it is difficult to employ the rotor groove 32 having a step shown in FIG.

  On the other hand, in the first embodiment, as described above, of the low-pressure external casings 12 to 14 as the stationary portion 29, the low-pressure C external casing 14 farthest from the thrust bearing 8 is restrained during normal operation. Without following the axial extension of the rotating portion 28. For this reason, the axial expansion difference between the low pressure C turbine rotor 4 and the low pressure C external casing 14 is reduced. In the case where the third embodiment has the configuration of the turbine of the first embodiment, the fluid leakage prevention unit in the low-pressure C external casing 14 may have the packing configuration shown in FIG.

  Furthermore, in the second embodiment, since all the low-pressure external casings 12 to 14 as the stationary portion 29 extend following the axial extension of the rotating portion 28, the low-pressure A turbine rotor 2 and the low-pressure A external casing 12, The axial expansion difference between the low-pressure B turbine rotor 3 and the low-pressure B outer casing 13 and the low-pressure C turbine rotor 4 and the low-pressure C outer casing 14 is further reduced. When the third embodiment includes the turbine configuration of the second embodiment, the fluid leakage prevention portion in the low pressure A external casing 12, the low pressure B external casing 13, and the low pressure C external casing 14 is shown in FIG. The structure of the made packing can be provided.

  By reducing the axial expansion difference between the turbine rotor and the external casing, the positional deviation between the packing teeth 31a, 31b and the convex portions 32a, 32b of the rotor groove 32 is reduced, and the packing teeth 31a are reduced. , 31b can be avoided. Thereby, in the turbine according to the third embodiment, by providing the configuration of the first or second embodiment, it is possible to employ the rotor groove 32 having a step, and the amount of leaked steam is reduced and the turbine performance is reduced. It can contribute to improvement.

  Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the technical scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the technical scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  For example, in the first embodiment, as shown in FIG. 1, three low-pressure A turbine rotors 2, a low-pressure B turbine rotor 3, and a low-pressure C turbine rotor 4 are provided as low-pressure turbine rotors. Two low pressure A external compartments 12, a low pressure B external compartment 13, and a low pressure C external compartment 14 are provided, and a thrust bearing housing 18 is connected to the low pressure C external compartment 14 provided in the low pressure C turbine rotor 4. .

  However, at least one low-pressure turbine rotor and low-pressure external casing are provided, and the thrust bearing housing is connected to at least one low-pressure external casing, preferably a constant-pressure external casing farthest from the high-pressure turbine rotor. That's fine.

DESCRIPTION OF SYMBOLS 1 High pressure turbine rotor 2 Low pressure A turbine rotor 3 Low pressure B turbine rotor 4 Low pressure C turbine rotor 5 Generator rotor 6a, 6b, 6c, 6d Coupling 7, 16, 22, 25 Thrust collar 8, 17, 23, 26 Thrust bearing 9, 18, 24, 27 Thrust bearing housing 10 Intermediate bearing stand 11 High pressure casing 12 Low pressure A outer casing 13 Low pressure B outer casing 14 Low pressure C outer casing 15a, 15b, 15c Axial direction fixed keys 19, 19a, 19b , 19c Damper mechanism 20 Base 21 Intermediate bearing stand axial direction fixed key 28 Rotating part 29 Static part 30 Packing 31, 31a, 31b Packing tooth 32 Rotor groove 33, 33a, 33b, 33c Connecting part 34 Generator

Claims (4)

A first rotor;
A first passenger compartment provided in the first rotor;
A first thrust bearing that receives an axial load of the first rotor;
A first thrust bearing housing enclosing the first thrust bearing;
A fixing device for fixing the first thrust bearing housing to a foundation;
A second rotor coupled to the first rotor or coupled to the first rotor via at least one other rotor;
A second passenger compartment provided in the second rotor;
A second thrust bearing that receives an axial load of the second rotor;
A second thrust bearing housing that houses the second thrust bearing;
A connecting portion for connecting the second thrust bearing housing and the second casing in an axial direction;
It is provided between the second casing and the foundation, and is capable of moving in the axial direction with respect to the foundation for thermal expansion during normal operation. An axial movement restraining device for attenuating the movement of the passenger compartment in the axial direction;
A turbine comprising: At least one other rotor coupled between the first rotor and the second rotor;
A third compartment provided in the other rotor;
A third thrust bearing that receives an axial load of the other rotor;
A third thrust bearing housing that houses the third thrust bearing;
A second connecting portion for connecting the third thrust bearing housing and the third casing in an axial direction;
The second casing is provided between the second casing and the foundation, and is movable in the axial direction with respect to the foundation during normal operation, and in the axial direction of the second casing when an earthquake occurs. An axial movement restraining device that damps movement;
The turbine according to claim 1, comprising:   The turbine according to claim 1, wherein the axial movement restraint device has a damper mechanism that acts as a resistance component against a thrust force when an earthquake occurs. In the fluid leakage prevention part of the second rotor, a step groove provided along the axial direction;
In the fluid leakage prevention part of the second casing, a packing provided with packing teeth so as to face the step groove along the axial direction;
The turbine according to claim 1, further comprising:

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