JPH06159009A - Steam turbine casing - Google Patents

Abstract

PURPOSE:To prevent a leakage of steam owing to the temperature rise of a bolt prior to a casing in the starting, or a generation of a stress corrosion cutting of the bolt owing to a long period of operation, in the horizontal flanges of a steam turbine high or medium pressure casing. CONSTITUTION:Steam passages 17A and 17B are provided near the inner walls of horizontal flanges 2A and 2B, so as to cool the horizontal flanges 2A and 2b by letting flow a steam of a relatively low temperature to the steam passages 17A and 17B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine casing, and more particularly to a cooling structure for a horizontal flange portion of a high and medium pressure casing.

[0002]

2. Description of the Related Art FIG. 11 is a cross-sectional view showing an example of a horizontal flange portion of a conventional steam turbine high-to-medium pressure casing, taken along a plane orthogonal to a rotation axis. The casing is divided into a casing upper half (1A) and a casing lower half (1B) in two horizontal planes, and horizontal flanges (2A) and (2
B). A large number of studs (3) are implanted in the lower horizontal flange (2B), and the upper half of the casing (1
A) is tightened by a nut (4) and is formed integrally with the lower half part (1B) of the casing. In order to facilitate tightening of the bolt and to control the tightening force, bolt heating which heats the bolt and utilizes its thermal expansion is usually performed, but since it is not related to the present invention, detailed description thereof will be omitted.

The horizontal flange bolts (3), especially the inner casing tightening bolts and the horizontal flanges, are heated by the influence of high temperature steam during operation, and when the bolts are tightened for a long time, the bolts and flanges Becomes a problem due to high temperature creep, causing steam leakage from the horizontal flange surface. Therefore, relatively low-temperature steam is flowed through the bolt hole (5) to cool it, and the bolt tightening force after long-time use at high temperature is secured.

[0004]

The conventional steam turbine casing has the following problems to be solved. 1) When the temperature of the casing is low at startup, the temperature of the bolt rises earlier than the casing due to the steam supplied to the bolt holes, the bolt tightening force decreases, and the cooling steam leaks from the horizontal flange surface. was there. 2) Stress corrosion cracking (Stress C
orrosion Crack; stress corrosion occurs in which corrosion is accelerated under stress, which causes cracks. ) Was generated, or the cooling steam leaked from the screw part.

[0005]

SUMMARY OF THE INVENTION The present invention proposes the following steam turbine casing in order to solve the above conventional problems. 1) Steam characterized in that a cooling steam flow path is formed inside the horizontal flange bolts of the horizontal flange portions of the upper half of the casing and the lower half of the casing along a surface substantially parallel to the inner surface of the casing. Turbine casing. 2) The steam turbine casing according to the above 1), characterized in that a pipe for supplying cooling steam to the flow passage from an arbitrary blade row outlet in the steam turbine is provided. 3) The steam turbine casing according to 1) or 2) above, wherein an obstacle is provided in the flow passage so that the flow velocity distribution of the cooling steam is uniform.

[0006]

Since the present invention has the above-mentioned structure, the following effects can be obtained. 1) The heat flux transferred from the high temperature steam to the horizontal flange and the bolt is blocked by the cooling steam flowing in the steam flow path inside the bolt. Therefore, the horizontal flange and the bolt are not heated to a high temperature, and the bolt and the flange are not distorted by creep and the bolt tightening force is not reduced. 2) Even after long-term operation, no stress corrosion cracking occurs in the horizontal flange bolts, and cooling steam does not leak from the threads.

3) At the time of starting the steam turbine, the bolts are warmed before the flanges, so that the bolts are not warmed and steam is not leaked from the horizontal flange surface. 4) When the steam turbine is started, the cooling steam passage blocks an excessive heat flux flowing from the inside of the flange, so that the temperature of the casing does not rise before the bolt. Therefore, the tightening force of the bolt becomes excessive, and the yielding of the bolt and flange reduces the tightening force of the bolt.
No steam leaks from the horizontal flange surface.

5) Since the temperature difference in the rotating shaft direction is also reduced, the bolt stress does not become excessive on the low temperature side.

[0009]

1 is a transverse sectional view showing a horizontal flange portion of a first embodiment in which the present invention is applied to a high-to-medium pressure casing, taken along a plane orthogonal to a rotation axis. In this figure, the same parts as those of the conventional one described with reference to FIG. 11 are given the same reference numerals to avoid redundancy, and detailed description thereof is omitted.

In this embodiment, the horizontal flanges (2) of the upper half (1A) and the lower half (1B) of the casing are used.
A) and (2B) are provided with a groove in the inner surface, and a lid (6
By welding A) and (6B), a cooling steam flow path (17A) is formed inside the stud (3) and along a surface substantially parallel to the inner surface of the casing (almost vertical surface).
(17B) is formed. Then, this cooling steam flow path (1
7A) and (17B) are cooled by flowing relatively low temperature steam. No cooling steam is supplied to the bolt holes (5). The pair of cooling steam passages (17A) and (17B) are provided at vertically symmetrical and horizontally symmetrical positions in order to prevent generation of thermal stress.

The cooling steam is supplied by piping from an arbitrary blade row outlet in the steam turbine. Therefore, the temperature of the cooling steam can be freely selected depending on from which paragraph the air is extracted. Further, it is also possible to extract the air from a plurality of paragraphs at the same time to control the temperature of the cooling steam so that the cooling is effectively performed when the turbine is started and stopped.

Next, FIG. 2 is a horizontal cross-sectional view (II-II cross section of FIG. 3) showing the horizontal flange portion of the second embodiment of the present invention cut along a plane orthogonal to the rotation axis, and FIG. FIG. 4 is a plan view showing the lower half only with the upper half removed, FIG. 4 is a side view from the inside of the casing (right side of FIG. 2), and FIG. 5 is a perspective view of the same. Also in these drawings, the same parts as those described above are designated by the same reference numerals, and detailed description thereof will be omitted.

Also in this embodiment, the casing upper half portion (1A) and the casing lower half portion (1B) have horizontal flanges (2A), (2B) which are substantially parallel to the inner surface of the casing and inside the horizontal flange bolts. Cooling steam passages (flat cooling chambers) (27A) and (27B) are formed along the surface, and the cooling steam inlet (7) relatively cools the steam in these passages (27A) and (27B). Is washed away. (8) is a cooling steam outlet. In this embodiment, the flat cooling chamber (27
A baffle plate (9) is provided so that the flow velocity distribution is uniform in A) and (27B).

Next, FIG. 6 is a horizontal cross-sectional view (cross-section VI-VI in FIG. 7) of the horizontal flange portion of the third embodiment of the present invention cut along a plane orthogonal to the rotation axis, and FIG. VII-VII is a horizontal cross-sectional view, and FIG. 8 is a perspective view of a high temperature pipe to be cast. Also in these drawings, the same parts as those described above are designated by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the casing (1
A), (1B) horizontal flange portions (2A), (2B) inside the bolt hole (5), along a plane substantially parallel to the inner surface of the casing, as shown in FIG. 1
0) is cast into the casing during manufacturing to form the cooling steam channels (37A) and (37B). In this case, in the vicinity of the cross section having the steam inlet hole (11) shown in FIG.
A large number of bent portions as shown in a) are provided to increase the density of the cooling steam flow paths (37A) and (37B).

Such cooling steam flow paths (37A), (3
7B), low-temperature steam is introduced from the downstream side, and is naturally discharged to the low-pressure chamber (13) isolated by the dummy ring (12). When the cooling steam flow rate is controlled according to the operating state, the cooling steam flow path (37B) is once taken out of the casing (1B) and controlled by the control valve (14) as shown in FIG. You can also

FIG. 10 is a diagram showing an example of an analysis result performed for quantitatively confirming the effect of the present invention. Figure 10
10A shows a radial temperature distribution in the case of a conventional horizontal flange portion shape, and FIG. 10B shows a radial temperature distribution in the case where a thermal shield and a cooling steam passage are provided.

[0018]

According to the present invention, the horizontal flange and the bolt can be effectively cooled without steam leaking from the horizontal flange surface or the thread portion of the flange bolt and stress corrosion cracking of the bolt. The reliability of the high and medium pressure steam turbine inner casing and the outer casing is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a horizontal flange portion of a first embodiment of the present invention cut along a plane orthogonal to a rotation axis.

FIG. 2 is a cross-sectional view showing a horizontal flange portion of a second embodiment of the present invention by cutting along a plane orthogonal to the rotation axis (of FIG. 3).
II-II cross section).

FIG. 3 is a plan view showing the lower half only with the upper half of FIG. 2 removed.

FIG. 4 is a side view seen from the right side of FIG.

FIG. 5 is a perspective view of the second embodiment.

6 is a cross-sectional view showing a horizontal flange portion of a third embodiment of the present invention by cutting along a plane orthogonal to the rotation axis (of FIG. 7).
VI-VI cross section).

7 is a horizontal sectional view taken along line VII-VII of FIG.

FIG. 8 is a perspective view of a high temperature pipe which is cast and cast in the third embodiment.

FIG. 9 is a diagram showing a modification of the third embodiment.

FIG. 10 is a diagram showing an example of an analysis result performed in order to quantitatively confirm the effect of the present invention.

FIG. 11 is a cross-sectional view showing an example of a horizontal flange portion of a conventional steam turbine high-to-intermediate pressure casing, taken along a plane orthogonal to the rotation axis.

[Explanation of symbols]

 (1A) Upper half of casing (1B) Lower half of casing (2A), (2B) Horizontal flange (3) Implant bolt (4) Nut (5) Bolt hole (6A), (6B) Lid (7) Cooling steam Inlet (8) Cooling steam outlet (9) Baffle plate (10) High temperature piping (11) Steam inlet hole (12) Dummy ring (13) Low pressure chamber (14) Control valve (17A), (17B) Cooling steam flow Line (27A), (27B) Cooling steam flow path (cooling chamber) (37A), (37B) Cooling steam flow path

Continued Front Page (72) Inventor Toru Kobayashi 2-1-1 Niihama, Arai-cho, Takasago-shi, Hyogo Mitsubishi Heavy Industries Ltd. Takasago Laboratory

Claims (3)

[Claims] 1. A flow path for cooling steam is formed inside a horizontal flange bolt of a horizontal flange portion of an upper half portion of a casing and a horizontal flange portion of a lower half portion of the casing, along a surface substantially parallel to an inner surface of the casing. And steam turbine casing. 2. The steam turbine casing according to claim 1, further comprising a pipe for supplying cooling steam to the flow passage from an arbitrary blade row outlet in the steam turbine. 3. The steam turbine casing according to claim 1, wherein an obstacle is provided so that the flow velocity distribution of the cooling steam becomes uniform in the flow passage.