JP2001207806A - Supporting structure for steam turbine casing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supporting structure for a steam turbine casing maintaining a sliding function and generating no excessive stress or uneven distortion or the like in an outer casing even when excessive frictional resistance or uneven frictional resistance occurs in a sliding face supporting the outer casing. SOLUTION: In a constitution of this supporting structure for the steam turbine casing, a plurality of rib plates are projectively fixed on an outer face of the outer casing of a steam turbine and a foot plate slidably mounted on a base plate attached to a foundation frame supporting the steam turbine is fixed to the rib plates with space with the outer face of the outer casing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a support structure for a steam turbine casing.

[0002]

2. Description of the Related Art A conventional steam turbine cabin support structure will be described with reference to FIGS. FIG. 4 is a perspective view showing a low-pressure casing of a general steam turbine with a part cut away.

As shown in FIG. 4 as an example of a low-pressure casing, a casing of a steam turbine is generally divided into upper and lower parts, and stationary vanes are provided inside an outer casing 1 to which upper and lower flange portions 4 are fastened. An inner casing 2 provided on the inner peripheral side is mounted, and a turbine rotor 3 provided with a moving blade is inserted through the center of the inner casing 2 and supported by bearings 5.

A foot plate 6 is horizontally fixed below the upper and lower flange portions 4 of the outer casing 1, and the foot plate 6 is placed on a base frame (not shown in FIG. The inner casing 2 and the turbine rotor 3 are supported.

FIG. 5 is a cross-sectional view of a conventional supporting portion of an external cabin. In FIG. 5, the upper external compartment 1a of the external compartment 1
The upper outer flange 4a is fixed to the lower outer casing 1 by welding.
b, a lower flange 4b is fixed by welding.
The upper and lower flanges 4a, 4b are fastened with bolts.

Below the lower flange 4b, a rib plate 7 projecting perpendicular to the outer surface of the lower outer casing 1b and serving as a reinforcing plate is welded and fixed to the lower flange 4b and the lower outer casing 1b. At the lower edge of the rib plate 7, the foot plate 6
Are welded and fixed to the rib plate 7 and the outer surface of the lower outer casing 1b.

[0007] The foot plate 6 is slidably mounted on a base plate 9 horizontally mounted on the upper surface of a concrete or steel base frame 8, and the outer casing 1 is supported on the base frame 8. The contact portion between the foot plate 6 and the base plate 9 forms a sliding surface 10.

In the conventional structure for supporting a steam turbine casing as described above, when the steam turbine is in an operating state, thermal expansion occurs in the external casing 1 due to the effect of the internal steam temperature. For this reason, a fixing point (anchor block) for the base frame 8 is provided near the center of the steam inlet 11 to serve as a starting point for thermal expansion. The sliding surface 10 of the base plate 9 on the base stand 8 side and the foot plate 6 on the side of the outer casing 1 is moved so that portions other than the fixed point can move against thermal expansion.
Are machined smoothly.

As a result, the foot plate 6 fixed to the outer casing 1 is slidably supported on the base plate 9 so that the outer casing 1 can be deformed by thermal expansion. It prevents the generation of excessive stress and uneven distortion.

[0010]

However, in the above-described conventional structure for supporting a steam turbine casing, the sliding surface 10 serving as a sliding mechanism involving the contact friction between the base plate 9 and the foot plate 6 includes equipment, Since the load such as the own weight of the structure and the external pressure from the atmosphere due to the vacuum state in the outer casing 1 is received from the vertical direction, the static friction force in the sliding portion 10 becomes excessive, The frictional resistance becomes uneven due to the different distribution of the coefficient of friction.The frictional resistance, which has the problem that the sliding function is reduced or hindered, becomes excessive or nonuniform. As a result of the inhibition of the sliding function, deformation of the outer casing 1 due to thermal expansion or the like is restricted, and excessive stress such as thermal stress is generated inside the outer casing 1. For this reason, fatigue of the structural members is promoted, or abnormal distortion is generated in the outer casing 1, and the inner casing 2 supported and positioned by the outer casing 1 is deformed. (Internal casing 2) and the rotating part (turbine rotor 3) come into contact with each other, which may cause large vibrations and damage the steam turbine.

The present invention solves the problem of the conventional structure for supporting a steam turbine casing, and slides even if excessive frictional resistance or uneven frictional resistance is generated on a sliding surface supporting an external casing. It is an object of the present invention to provide a support structure for a steam turbine cabin that maintains its function and does not generate excessive stress, uneven distortion, or the like in an external cabin.

[0012]

Means for Solving the Problems (1) The present invention has been made to solve the above problems, and as a first means, a plurality of rib plates are provided on the outer surface of an outer casing of a steam turbine. A foot plate that is protruded and fixed and slidably mounted on a base plate attached to a base frame that supports the steam turbine is fixed to the rib plate with a gap from the outer surface of the outer casing. The present invention provides a support structure for a steam turbine cabin, which is characterized in that:

According to the first means, since the foot plate and the outer casing are not directly welded, the deformation difference between the outer casing and the foot plate due to the difference in thermal expansion and the difference in rigidity is reduced by the out-of-plane of the rib plate. The deformation can be absorbed, and the outer casing can be freely deformed.

Further, even if the frictional resistance is excessive or non-uniform on the sliding surface, the deformation difference between the outer casing and the foot plate can be absorbed as the out-of-plane deformation of the rib plate.

(2) As a second means, in the structure for supporting a steam turbine casing of the first means, the foot plate is divided into a plurality of pieces and each of the divided foot plates is at least one of the ribs. The present invention provides a support structure for a steam turbine casing, which is fixed to a plate.

According to the second means, in addition to the function of the first means, since the foot plate is divided,
The in-plane rigidity is reduced, and each of the divided foot plates can be deformed in accordance with the thermal expansion of the outer casing.

Further, even if the frictional resistance is excessive or non-uniform on the sliding surface, it is balanced in each of the divided foot plates to reduce the occurrence of excessive stress and distortion.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A support structure for a steam turbine casing according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a support portion of an outer casing according to the present embodiment, and FIG. 2 is a partial perspective view showing an assembled state of the outer casing and a foot plate.

1 and 2 are denoted by the same reference numerals in FIGS. 1 and 2 so as to clarify their mutual relations to facilitate understanding of the present embodiment. The description is omitted. This is the same in FIG. 3 of a second embodiment described later.

The present embodiment differs from the conventional example in that the foot plate 16 is fixed to the lower edge of the rib plate 7 by a welding operation. It is not directly welded to the cabin 1b and the foot plate 16
A gap δ is provided between the lower outer casing 1b side edge and the outer surface of the lower outer casing 1b.

The outer casing 1 is composed of an upper outer casing 1a and a lower outer casing 1b.
and a pressure vessel bolted at the lower flange 4b to the outer casing 1 during operation of the turbine, and the inside of the outer casing 1 is kept at a vacuum, so that the atmospheric pressure and its own weight act vertically downward.

In order to support these loads, a rib plate 7 serving as a reinforcing plate is welded and fixed to the lower flange 4b and the lower outer casing 1b at appropriate intervals in terms of strength. The foot plate 16 is attached to the rib plate 7 so as to protrude from the outer surface of 1b. Foot plate 16 is rib plate 7
, But is not directly welded to the lower outer casing 1b.

The foot plate 16 is placed on a base plate 9 mounted on the base frame 8, and the outer casing 1 is slidably moved on the sliding surface 10 between the foot plate 16 and the base plate 9. Supported by

In the above-described structure for supporting the steam turbine casing of the present embodiment, the external casing 1
Thermal expansion occurs due to the effect of the internal steam temperature. At this time, the sliding surface 1 between the foot plate 16 and the base plate 9
At zero, frictional resistance is generated by multiplying the load acting thereon by the friction coefficient.

In the above-mentioned conventional structure, the foot plate 6 is directly welded to the lower outer casing 1b. On the other hand, while being excessively restrained as if a hoop was fitted, the restraint was further promoted by the influence of excessive and uneven frictional resistance, and excessive stress such as thermal stress was generated inside the external casing 1 or abnormal. Which resulted in distortion.

On the other hand, in the present embodiment, since the foot plate 16 and the outer casing 1 are not directly welded, a difference in deformation between the outer casing 1 and the foot plate 16 due to a difference in thermal expansion or rigidity is reduced. It can be absorbed as out-of-plane deformation of the rib plate 7.

As a result, the influence of the foot plate 16 for restraining the deformation of the outer casing 1 can be eliminated, and the outer casing 1 can be freely deformed, so that excessive stress such as thermal stress or abnormal distortion is generated. Can be reduced.

Also, even if the frictional resistance is excessive or non-uniform on the sliding surface 10, the rib plate 7 is similarly out-of-plane, and the difference in deformation between the external casing 1 and the foot plate 16 can be absorbed. Generation of stress and distortion can be reduced.

The deformation difference between the outer casing 1 and the foot plate 16 which can be absorbed as out-of-plane deformation of the rib plate 7 is appropriately calculated, and the shape of the rib plate 7, the outer casing 1 and the foot plate 1 are calculated.
In order to determine the amount of the gap δ with respect to 6, it is desirable to carry out numerical calculations such as finite element analysis in advance.

A structure for supporting a steam turbine casing according to a second embodiment of the present invention will be described with reference to FIGS.
Also in this embodiment, a cross-sectional view of the support portion of the outer casing is shown in the same manner as in FIG. 1 of the first embodiment, but the foot plate 16 in FIG. 1 is different from the foot plate 26 in this embodiment. Shall be replaced. FIG. 3 is a partial perspective view showing an assembled state of the outer casing and the foot plate in the present embodiment.

In this embodiment, as shown in FIG. 3, the foot plate 26 is divided for each rib plate 7 as a reinforcing plate, which is different from the first embodiment described above.
The other points are the same as the first embodiment.

In the support structure of the steam turbine casing according to the present embodiment, while the load such as its own weight and vacuum load acting vertically downward during operation of the steam turbine is supported by the foot plate 26 as before, Since the in-plane rigidity can be reduced, each of the divided foot plates 26 can be deformed in accordance with the thermal expansion of the outer casing 1, and is superimposed on the effect of absorbing the displacement difference due to the out-of-plane deformation of the rib plate 7. As a result, it is possible to reduce the occurrence of excessive stress and distortion such as thermal stress in the external casing 1.

Further, even if the frictional resistance is excessive or uneven on the sliding surface, each of the divided foot plates 26
In the same manner, it is possible to reduce the occurrence of excessive stress and strain by superimposing on the out-of-plane deformation of the rib plate 7 in the same manner.

In this embodiment, the foot plate 26 is divided into a plurality of rib plates 7 in FIG. 3, but the foot plate 26 is divided into a plurality of pieces and the divided foot plates 26 are appropriately divided. A plurality of rib plates 7
May be fixed to the foot plate 26.
Can be set to the extent that the in-plane rigidity is required to be reduced by the division.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes may be made to the specific structure within the scope of the present invention. Needless to say.

For example, in the embodiment, the support structure for the low-pressure external compartment is illustrated and described. However, the present invention is not limited to the low-pressure compartment, but can be applied to a support structure for a steam turbine compartment.

[0037]

(1) According to the first aspect of the present invention, the support structure of the steam turbine casing is formed by projecting and fixing a plurality of rib plates on the outer surface of the outer casing of the steam turbine to support the steam turbine. The foot plate slidably mounted on the base plate attached to the base frame to be mounted is fixed to the rib plate with a gap between the foot plate and the outer surface of the outer casing. Since the outer casing and the outer casing are not directly welded, the deformation difference due to the difference in thermal expansion and rigidity between the outer casing and the foot plate can be absorbed as out-of-plane deformation of the rib plate, and the deformation of the outer casing Since the influence of the foot plate that restrains the airtightness can be eliminated and the outer casing can be freely deformed, generation of excessive stress such as thermal stress and abnormal distortion can be reduced.

Further, even if the frictional resistance becomes excessively or non-uniformly on the sliding surface, as the out-of-plane deformation of the rib plate, the deformation difference between the outer casing and the foot plate can be absorbed, so that excessive stress and distortion are generated. Can be reduced.

(2) According to the invention of claim 2, in the support structure of the steam turbine casing according to claim 1,
Since the foot plate is divided into a plurality of parts and each of the divided foot plates is fixed to at least one of the rib plates, in addition to the effect of the invention of claim 1, the foot plate is divided. Therefore, the in-plane rigidity can be reduced, and each divided foot plate can be deformed in response to the thermal expansion of the outer casing, superimposed on the effect of absorbing the displacement difference due to the out-of-plane deformation of the rib plate. As a result, it is possible to reduce the occurrence of excessive stress or distortion such as thermal stress in the external compartment.

Even if the frictional resistance is excessive or non-uniform on the sliding surface, the frictional resistance is balanced in each of the divided foot plates. Generation of distortion can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a support structure of a steam turbine casing according to a first embodiment of the present invention, and is a cross-sectional view of a support portion of an external casing.

FIG. 2 is a partial perspective view showing an assembled state of an outer casing and a foot plate according to the first embodiment of the present invention.

FIG. 3 is a partial perspective view showing an assembled state of an outer casing and a foot plate according to a second embodiment of the present invention.

FIG. 4 is a partially cutaway perspective view showing a low-pressure cabin of a general steam turbine.

FIG. 5 is a cross-sectional view of a conventional supporting portion of an external compartment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 outer casing 1a upper outer casing 1b lower outer casing 2 inner casing 3 turbine rotor 4 flange 4a upper flange 4b lower flange 6 foot plate 7 rib plate 8 base frame 9 base plate 10 sliding surface 16 foot plate 26 Foot plate

Claims (2)

[Claims] A plurality of rib plates projectingly fixed to an outer surface of an outer casing of the steam turbine, and a foot plate slidably mounted on a base plate attached to a base frame supporting the steam turbine. A supporting structure for the steam turbine casing, which is fixed to the rib plate with a gap provided between the outer casing and the outer casing. 2. The steam turbine casing supporting structure according to claim 1, wherein the foot plate is divided into a plurality of parts, and each of the divided foot plates is fixed to at least one of the rib plates. Characteristic steam turbine cabin support structure.