Rotary kinetic fluid motors or pumps – Including heat insulation or exchange means – Cooling fluid contacts shaft – seal or bearing
Reexamination Certificate
1999-10-28
2001-08-14
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
Including heat insulation or exchange means
Cooling fluid contacts shaft, seal or bearing
Reexamination Certificate
active
06273675
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cooling architecture for flanges of a steam turbine casing in order to prevent the leakage of steam caused by a drop of the fastening force of bolts for fastening the flanges.
2. Prior Art
FIG. 4
is a sectional view illustrating a portion of the casing of a conventional steam turbine, wherein reference numeral
10
denotes an upper casing, and
11
denotes a lower casing. A steam turbine is hermetically sealed by these two casings to prevent the leakage of the steam to the outside. Reference numerals
12
and
13
denote flanges of the upper and lower casings
10
and
11
. The two flanges
12
and
13
are joined together and are fastened by bolts
14
which are arranged every predetermined interval along the axis of the turbine to couple the upper and lower casings
10
and
11
together. Reference numeral
15
denotes a heat insulator which covers the surfaces of the flanges
12
and
13
, upper parts of the bolts
14
and the surfaces of the upper and lower casings
10
and
11
as shown.
In the casing of the steam turbine constituted as above, because the steam of a high temperature flows through the inner steam turbine, the casing is heated by high temperature steam, and the flanges
12
and
13
are also heated and are thermally deformed. Upon receiving the thermal deformation, the bolts
14
undergo the thermal extension and gradually decrease the fastening force after repetitions of the above-mentioned cycle. As the fastening force drops, the steam leaks through the junction surface between the flanges
12
and
13
. Because the temperature of the steam is high, the leakage of the stream is dangerous. Besides, large amount of the leakage of steam affects the performance of the steam turbine.
In order to prevent the leakage of steam, there has heretofore been employed a cooling architecture shown in
FIG. 5
, wherein reference numerals
10
to
15
denote the same elements as those of FIG.
4
. In this case, however, holes
25
are formed in the vertical direction to penetrate through the flanges
12
and
13
and the heat insulator
15
near the bolts
14
in order to prevent the bolts
14
and the flanges
12
and
13
near the bolts from being thermally deformed. Because the peripheries of the holes
25
are heated to a high temperature by the steam, natural convection flow of the ambient air
30
is generated to spontaneously cool the portions of the flanges around the bolts
14
.
In the conventional casing of the steam turbine as described above, the casing, too, is heated to a high temperature due to the high-temperature steam, the bolts for coupling the flanges are thermally deformed to gradually decrease the fastening force, and the steam may leak through the junction surfaces of the flanges. As shown in
FIG. 5
, therefore, holes
25
are formed in the flanges
12
,
13
and in the heat insulator
15
around the bolts
14
, in order to cool the bolts
14
and the flanges
12
and
13
around the bolts based on the natural convection of the air.
According to the above-described conventional method, that is, perforation of the flanges
12
and
13
, however, holes must be pierced through not only the flanges
12
and
13
, but also the heat insulator
15
, and laborious work for piercing the holes is required. Besides, the holes are clogged with the dust of the heat insulator and the air is not often naturally convected to a sufficient degree, and some countermeasure must be taken.
The present invention, therefore, provides a cooling architecture which reliably cools the flanges of the steam turbine casing based on the natural convection of the air, and by forming holes through the heat insulator, but not through the flange to create the natural convection of the air with a simple process.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problem according to a first aspect of the present invention, there is provided a cooling architecture for flanges which are formed on a steam turbine upper and lower casings for hermetically covering a steam turbine, are fastened together with bolts, and are covered with heat insulators including upper and lower casings, and bolts, wherein pipes for introducing the air are arranged at the contact surface near the bolts between the outer surfaces of the flanges and the heat insulator for covering the outer surfaces of the flanges, and extended upward and downward beyond the outer surfaces of the heat insulator.
According to a second aspect of the present invention there is provided a cooling architecture for flanges, which are formed on turbine upper and lower casings for hermetically covering a steam turbine, are fastened together with bolts, and are covered with heat insulators including the upper and lower casings and bolts, wherein grooves for introducing the air are formed through the heat insulator covering the outer surfaces of the flanges so as to be contacted to the outer surfaces of the flanges near the bolts.
In the flange-cooling architecture according to the first aspect, the pipes are arranged in the heat insulators so as to contact with the flanges. The flanges are heated at high temperatures by the high-temperature steam. As the bolts fastening the flanges are thermally deformed, the fastening force of the bolts decreases. Here, however, the flanges are heated at a temperature higher than the temperature of the surrounding air. Accordingly, the air are introduced into the pipes from the lower ends thereof and flows out from the upper ends by a natural convection force. Owing to the natural convection, the flanges are cooled, and the bolts are prevented from being thermally deformed and reducing the fastening force. Thus, because the fastening force does not decrease, no gap develops between the two flanges, and the steam does not leak. The number of the pipes can be increased along the axial direction to obtain a more reliable cooling effect if necessary.
According to the cooling architecture of the second aspect, the grooves are formed through the heat insulator covering the outer surfaces of the flanges near the bolts so as to contact with the outer surfaces of the flanges instead of providing the pipes. Therefore, no pipe is required, and no hole needs be pierced in the flanges which are rigid members unlike that of the prior art. Thus, the air is introduced into the grooves in the same manner as in the first aspect, the flanges and bolts are cooled by the natural convection, and the cooling architecture is constructed more easily.
REFERENCES:
patent: 53-125504 (1978-11-01), None
patent: 54-035507 (1979-03-01), None
patent: 61-200310 (1986-09-01), None
patent: 10-196312 (1998-07-01), None
patent: 002133328 (1999-12-01), None
Magoshi Ryotaro
Nakano Takashi
Mitsubishi Heavy Industries Ltd.
Ryznic John E.
Wallenstein & Wagner Ltd.
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