JPH06101415A - Steam turbine casing - Google Patents

Abstract

PURPOSE:To previously prevent corrosion of flanges or the like by providing cylindrical members on a circular space formed by fastening bolts and their through-holes for preventing corrosion of the flanges and the fastening bolts of upper and lower half casings, and punching thereon ports for inflow and outflow of steam. CONSTITUTION:A steam turbine casing is formed such that flanges 1a, 1b of upper and lower half casings are in close contact, bolts 2 are penetrated through fastening bolt holes 4 and followed by fastening by means of nuts 3, and airtight structure is provided. Communication ports 5 are formed between the fastening bolt holes 4 for warming or cooling steam. Cylindrical members 10 are provided on a circular space formed by the fastening bolt holes 4 and the fastening bolts 2 for preventing corrosion of the flanges 1a, 1b and the fastening bolts 2. A plurality of steam ports 10a, 10b are formed on the cylindrical members 10 for inflow and outflow of the above-stated steam.

Description

Detailed Description of the Invention

[0001]

This invention relates to steam turbine casings.

[0002]

2. Description of the Related Art A steam turbine casing is composed of an upper half casing and a lower half casing, and a flange connecting these casings must have such strength that high temperature and high pressure steam inside the casing does not leak from the joint surface to the outside of the casing. Therefore, each flange has a sufficient thickness and area, and both flanges are tightened by bolts. In this way, when the structure is such that the thickness and area of each flange are large, the heat capacity of the flange is large accordingly, and
Since the heat conduction of each flange becomes small, each flange is deformed by thermal stress caused by the difference in steam temperature inside and outside the casing or the difference in temperature between steam and the atmosphere.

In order to provide the casing and the tightening bolts with sufficient strength to cope with this deformation, steam is circulated through the tightening bolt holes of the flange to improve thermal deformation and the strength of the tightening bolts. At this time, there is cooling for circulating the relatively low temperature steam to cool the flange, and warming for heating through the high temperature steam.
Select one according to the characteristics of the device.

FIG. 4 shows the structure of the flange portion of the conventional steam turbine casing described above, and a case where cooling is performed will be described.

In the figure, the flange 1 of the upper half casing
Both flange surfaces 1 of a and the flange 1b of the lower half casing
The a ′ and 1b ′ are in close contact with each other, and the tightening bolt 2 is inserted into the tightening bolt holes 4 formed in both flanges, and is tightened by the nuts 3 at both ends of the tightening bolt 2. A steam passage hole 5 is formed in the flange 1a of the upper half casing and a flange 1b of the lower half casing, and cooling steam 6 shown by an arrow in the drawing is used for tightening bolts from the steam passage hole 5 formed in the flange 1a of the upper half casing. It flows into the hole 4. Then, while passing around the tightening bolt 2, it flows into the steam passage hole 5 formed in the flange 1b of the lower half casing, and the cooling steam 6 flowing out from this steam passage hole 5 flows around the tightening bolt hole 4. It passes through and flows into the cooling steam 6 of the flange 1a of the upper half casing. Thereby, the flange 1a of the upper half casing, the flange 1b of the lower half casing and the tightening bolt 2 are sufficiently cooled. The steam passage holes 5 are alternately formed in the flange 1a of the upper half casing and the flange 1b of the lower half casing so as to cool the entire tightening bolt 2 as shown in the figure.

[0006]

However, the above-mentioned flange structure has a problem that the periphery of the flange and the like is eroded by cooling or warming. That is, since the cooling steam 6 contains solid particles introduced from the turbine stage in the middle or outside the turbine, the cooling steam 6 is shown in FIG.
When the cooling steam 6 including the solid particles 6a flows into the steam passage hole 5 from the tightening bolt hole 4 as described above, the flow direction changes rapidly, so that the vortex 7 is generated at the inlet of the steam passage hole 5. The solid particles 6a in the cooling steam 6 cause an eroded portion 8 in a part of the tightening bolt 2.

Further, as shown in detail in the Y part of FIG. 4, when jetting from the outlet of the steam passage hole 5 into the tightening bolt hole 4, the solid particles 6a in the cooling steam 6 directly hit the tightening bolt 2 and are eroded. Part 9 arises.

The same applies to the case where the flange portion of the steam turbine casing is warmed, and the tightening bolt 2 is eroded by the solid particles 6a contained in the warming steam 6.

As described above, since the tightening bolt 2 is subjected to high stress in order to have sufficient strength for tightening the flange, the extreme corrosion of the surface of the bolt causes the stress concentration. Therefore, it is not preferable in terms of strength. Then, if the deterioration of the bottle strength becomes excessive, the high temperature and high pressure steam inside the casing will leak from the joint surface to the outside of the casing.

Therefore, it is an object of the present invention to provide a safe and highly reliable steam turbine casing that prevents erosion that occurs in the flange tightening bolt when cooling or warming is performed.

[0011]

According to the present invention, in order to make a steam turbine casing have an airtight structure, the surfaces of the flanges of the upper half casing and the lower half casing are brought into close contact with each other, and a plurality of tightening members are formed on the flanges. In the steam turbine casing, the tightening bolt holes are tightened by penetrating the tightening bolts into the bolt holes, and steam passage holes for flowing steam for warming or cooling are formed in the flanges by communicating between the tightening bolt holes. A cylindrical erosion preventive member for preventing erosion of the flange and the tightening bolt is arranged in an annular space formed by and the tightening bolt, and a steam hole through which a plurality of steam flows in and out is provided in the cylinder. It is a thing.

[0012]

With the above construction, steam is prevented from eroding the flange and the tightening bolt by the cylindrical erosion preventing member arranged in the annular space formed by the tightening bolt hole and the tightening bolt.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a flange of a steam turbine casing showing an embodiment of the present invention.
The difference from the conventional example shown in FIG. 4 is that an erosion prevention member 10 formed in a ring-shaped cylinder surrounding the outer peripheral wall of the tightening bolt 2 is additionally provided, and both ends of the erosion prevention member 10 are fixed by nuts 3. Is. The erosion prevention member 10 is, for example, A in FIG.
As shown in FIG. 2 showing the details of the portion, a wall surface 10 is provided at a portion where the cooling steam 6 flows from the steam passage hole 5 into the tightening bolt hole 4.
a is provided, and steam holes 10b are provided at both ends thereof. Further, in the erosion prevention member 10, for example, as shown in FIG. 3 showing the details of the portion B of FIG.
A wall surface 10a is provided at a portion where the steam flows into the steam passage hole 5, and steam holes 10b are provided at both ends thereof.

As described above, the erosion preventing member 10 is provided at a position where the cooling steam 6 directly collides with the cooling steam 6 after flowing through the steam passage hole 5 so that the cooling steam 6 does not directly collide with the base material of the tightening bolt 2. ing. As a result, the tightening bolt 2 is not corroded, and the tightening bolt 2
The function of can be maintained long enough.

Although the erosion preventive member 10 is eroded by the cooling steam 6 over time, the parts can be easily replaced. Therefore, if the parts are replaced during the regular inspection of the steam turbine, the function of the casing flange can be maintained sufficiently long. There are advantages.

Further, if the erosion preventing member 10 is subjected to a surface treatment to increase its hardness, its erosion resistance is improved, so that the period for replacing the parts of the erosion preventing member 10 can be lengthened.
As described above, according to the present embodiment, it is possible to obtain an effect that the erosion resistance can be significantly improved as compared with the conventional turbine device and that the function can be performed sufficiently long.

[0018]

As described above, according to the present invention, since the erosion preventing member is provided, the flange of the steam turbine casing and the tightening bolt are less eroded and these functions can be maintained for a long time. Therefore, the erosion resistance can be significantly improved as compared with the conventional turbine casing.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a steam turbine casing showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing details of a portion A in FIG.

FIG. 3 is an explanatory diagram showing details of a portion B in FIG.

FIG. 4 is a cross-sectional view showing the structure of a conventional steam turbine casing.

5 is an explanatory diagram showing details of an X portion of FIG. 4. FIG.

6 is an explanatory diagram showing details of a Y portion of FIG. 4. FIG.

[Explanation of symbols]

 1a Upper half casing flange 1b Lower half casing flange 2 Tightening bolt 3 Nut 4 Tightening bolt hole 5 Steam passage hole 6 Cooling steam

Claims (1)

[Claims] 1. To make a steam turbine casing an airtight structure, the surfaces of respective flanges of the upper half casing and the lower half casing are brought into close contact with each other, and the tightening bolts are passed through a plurality of tightening bolt holes formed in the flanges. In the steam turbine casing, wherein the flange is formed with a steam passage hole through which the steam for warming or cooling is communicated between the tightening bolt holes, the steam turbine casing is formed by the tightening bolt hole and the tightening bolt. A cylindrical erosion preventive member for preventing erosion of the flange and the tightening bolt is arranged in the annular space to be provided, and a plurality of steam holes through which the steam flows in and out of the cylinder of the erosion preventive member are provided. A steam turbine casing characterized by the above.