U.S. patent application number 15/287145 was filed with the patent office on 2017-01-26 for steam valve.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. The applicant listed for this patent is KABUSHIKI KAISHA TOSHIBA. Invention is credited to Takashi ISEKI, Yuichi NAKAMURA, Tomoo OOFUJI, Tsutomu SHIOYAMA.
Application Number | 20170022841 15/287145 |
Document ID | / |
Family ID | 54287571 |
Filed Date | 2017-01-26 |
United States Patent
Application |
20170022841 |
Kind Code |
A1 |
NAKAMURA; Yuichi ; et
al. |
January 26, 2017 |
STEAM VALVE
Abstract
A steam valve 10 of an embodiment includes: a valve element 32
of a steam control valve 30, the valve element 32 being provided to
be movable in an up and down direction; a valve element 42 of a
main stop valve 40, the valve element 42 being provided under the
valve element 32 coaxially with the valve element 32 to be movable
in the up and down direction; a valve seat 60 with which the valve
element 32 and the valve element 42 come into and out of contact;
and a guide tube 43 slidably supporting a valve rod 41 including
the valve element 42, and having a flange portion 43a at a bottom
side in a casing 20. The steam valve 10 further includes: the
casing 20 housing the valve element 32, the valve element 42, the
valve seat 60, and the guide tube 43; a drain discharge hole 23
formed at a bottom side of the casing 20; a drain pipe 70 provided
with a shutoff valve 71 and communicating with the drain discharge
hole 23; and a flow direction changing part 80 which changes a
direction in which steam having passed between the valve element 32
and the valve seat 60 and flowing along the guide tube 43 flows
toward the drain discharge hole 23.
Inventors: |
NAKAMURA; Yuichi; (Yokohama,
JP) ; OOFUJI; Tomoo; (Yokohama, JP) ;
SHIOYAMA; Tsutomu; (Yokohama, JP) ; ISEKI;
Takashi; (Minato, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOSHIBA |
Minato-ku |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Minato-ku
JP
|
Family ID: |
54287571 |
Appl. No.: |
15/287145 |
Filed: |
October 6, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2015/001960 |
Apr 7, 2015 |
|
|
|
15287145 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D 17/145 20130101;
F16K 1/307 20130101; F16K 1/443 20130101; F16K 51/00 20130101; F01D
25/00 20130101; F05D 2220/31 20130101; F01D 17/10 20130101; F16K
1/12 20130101; F16K 1/446 20130101 |
International
Class: |
F01D 17/14 20060101
F01D017/14; F16K 1/44 20060101 F16K001/44; F16K 1/12 20060101
F16K001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 2014 |
JP |
2014-079781 |
Claims
1. A steam valve comprising: a first valve element which is
provided to be movable in an up and down direction and adjusts a
flow rate of steam; a second valve element which is provided under
the first valve element coaxially with the first valve element to
be movable in the up and down direction and shuts off a flow of the
steam; a valve seat with which the first valve element and the
second valve element come into and out of contact; a guide tube
slidably supporting a valve rod including the second valve element,
and having a flange portion protruding outward all over a
circumferential direction, at a bottom side in the steam valve; a
casing housing the first valve element, the second valve element,
the valve seat, and the guide tube; a drain discharge hole formed
in a sidewall of the casing at a bottom side; a drain pipe provided
with a shutoff valve and communicating with the drain discharge
hole; and a flow direction changing part which changes a direction
in which the steam having passed between the first valve element
and the valve seat and flowing along the guide tube, flows toward
the drain discharge hole.
2. The steam valve according to claim 1, wherein the flow direction
changing part is a ridge part protruding outward from a side
surface of the guide tube on the drain discharge hole side and
extending in an axial direction.
3. The steam valve according to claim 2, wherein an upper end
portion of the ridge part has a circumferential width that becomes
smaller upward.
4. The steam valve according to claim 1, wherein the flow direction
changing part comprises: a tubular body whose one end is coupled to
an inlet of the drain discharge hole and whose other end has an
upper half tip protruding in a length direction beyond a lower half
tip of the other end; and a communication hole formed in the length
direction in the tubular body and communicating with the drain
discharge hole.
5. The steam valve according to claim 1, wherein the flow direction
changing part is groove portions arranged in an axial direction in
a plurality of tiers in a side surface of the guide tube on the
drain discharge hole side.
6. The steam valve according to claim 5, wherein the groove
portions are each formed all along a half circumference of the side
surface of the guide tube on the drain discharge hole side.
7. The steam valve according to claim 1, wherein the flow direction
changing part is the valve seat whose inner peripheral surface is
curved such that a passage cross section of a steam passage at a
center of the valve seat becomes larger toward a downstream side
from a throat portion of the steam passage.
8. The steam valve according to claim 1, wherein the flow direction
changing part is constituted by narrowing a gap between the
sidewall of the casing on the side where the drain discharge hole
is formed and the guide tube.
9. The steam valve according to claim 1, wherein the flow direction
changing part is constituted by making an outside diameter of a
sidewall of the guide tube above the flange portion equal to or
more than an outside diameter of the flange portion.
10. The steam valve according to claim 1, wherein the flow
direction changing part is constituted by making a height of the
flange portion of the guide tube three times or more an
axial-direction distance between a bottom surface of the casing and
an upper end of the drain discharge hole.
11. A steam valve comprising: a first valve element which is
provided to be movable in an up and down direction and adjusts a
flow rate of steam; a second valve element which is provided under
the first valve element coaxially with the first valve element to
be movable in the up and down direction and shuts off a flow of the
steam; a valve seat with which the first valve element and the
second valve element come into and out of contact; a guide tube
slidably supporting a valve rod including the second valve element,
and having a flange portion protruding outward all over a
circumferential direction, at a bottom side in the steam valve; a
casing housing the first valve element, the second valve element,
the valve seat, and the guide tube; a drain discharge hole formed
in a bottom wall of the casing, and including a vertical hole
extending from an inner surface of the bottom wall vertically
downward and a lateral hole communicating with the vertical hole
and penetrating laterally; and a drain pipe provided with a shutoff
valve and communicating with the lateral hole of the drain
discharge hole.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of prior International
Application No. PCT/JP2015/001960 filed on Apr. 7, 2015, which is
based upon and claims the benefit of priority from Japanese Patent
Application No. 2014-079781 filed on Apr. 8, 2014; the entire
contents of all of which are incorporated herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a steam
valve.
BACKGROUND
[0003] A steam turbine pipe system includes a main steam pipe which
leads steam generated in a boiler to a steam turbine. In this main
steam pipe, a steam valve for regulating a flow rate of the steam
and shutting off the steam is provided.
[0004] FIG. 18 is a view illustrating a vertical cross section of a
conventional steam valve 300. The conventional steam valve 300
provided in a main steam pipe is what is called a combined steam
valve in which a steam control valve and a main stop valve are
combined in one casing 310.
[0005] As illustrated in FIG. 18, the steam valve 300 includes: a
steam control valve 320 movable in an up and down direction when
driven from above; and a main stop valve 330 provided under the
steam control valve 320 coaxially with the steam control valve 320
and movable in the up and down direction when driven from under.
The steam valve 300 further includes a cylindrical strainer 340
disposed so as to surround the steam control valve 320 and the main
stop valve 330. The strainer 340 prevents a foreign object in the
steam led through a steam inlet 311 from flowing downstream.
[0006] The steam control valve 320 includes a valve rod 321 and a
valve element 323. The valve rod 321 penetrates through an upper
cover 350 and is movable in the up and down direction when driven
from above. The valve element 323 is provided annularly on a lower
end side of the valve rod 321 and has a dented portion 322 in its
lower surface.
[0007] The main stop valve 330 includes a valve rod 331, a valve
element 332, and a guide tube 333. The valve rod 331 penetrates
through a bottom portion of the casing 310 and is movable in the up
and down direction when driven from under. The valve element 332 is
provided on an upper end side of the valve rod 331 and protrudes
radially outward from the valve rod 331 all over the
circumferential direction. The valve element 332 is housed in the
dented portion 322 of the valve element 323 of the steam control
valve 320. The guide tube 333 is a cylinder fixed to the bottom
portion of the casing 310 and having the valve rod 331 penetrating
therethrough at its center.
[0008] Under the valve element 323 of the steam control valve 320
and the valve element 332 of the main stop valve 330, a valve seat
360 which comes into contact with these valve elements is provided.
When the valve element 323 of the steam control valve 320 and the
valve element 332 of the main stop valve 330 are pressed while in
contact with the valve seat 360, it is possible to shut off the
flow of the steam.
[0009] At the bottom side of the casing 310, a drain discharge hole
312 for discharging a drain generated during warming for putting
the steam turbine into operation is provided. As illustrated in
FIG. 18, due to arrangement and structural reasons, the drain
discharge hole 312 is formed in a sidewall of the casing 310 at the
bottom side so as to extend laterally (in the horizontal direction
in FIG. 18). Further, a drain pipe 370 is provided on the drain
discharge hole 312 to lead the drain to the outside. A shutoff
valve 380 is provided in the drain pipe 370. When the shutoff valve
380 is opened, the drain generated during the warming is led to a
condenser. Then, the shutoff valve 380 is closed after the warming.
That is, during the normal operation of the steam turbine, the
drain pipe 370 constitutes a pipe part whose one end communicates
with the inside of the steam valve 300 and whose other end is
closed.
[0010] The steam valve 300 having such a structure is supplied with
the steam superheated by a superheater of the boiler disposed
upstream of the steam valve 300, through the steam inlet 311. The
steam led through the steam inlet 311 passes through the strainer
340 to pass between the valve element 323 of the steam control
valve 320 and the valve element 332 of the main stop valve 330, and
the valve seat 360. Flows of the steam having passed downward in a
through portion provided at the center of the valve seat 360 are
bent along a steam passage downstream of the valve seat 360. Then,
the steam is discharged through a steam outlet 313 to be led to a
high-pressure turbine.
[0011] At this time, the flow rate of the steam is adjusted by a
valve opening degree of the steam control valve 320. Specifically,
when a required flow rate of the steam is small, the valve opening
degree of the steam control valve 320 is small, and when the
required flow rate of the steam is large, the valve opening degree
of the steam control valve 320 is large. When the required flow
rate of the steam is small, a gap between the valve element 323 of
the steam control valve 320 and the valve seat 360 is narrow and
thus the flows of the steam are narrowed in this gap. Then, a flow
velocity of the steam increases.
[0012] Here, as illustrated in FIG. 18, partial steam F of the
steam having passed between the valve element 323 of the steam
control valve 320 and the valve seat 360 flows downward along a
side surface of the guide tube 333. Then, the steam F flows along
the shape of a flange portion 333a which is provided on the guide
tube 333 at the bottom side of the casing 310 to protrude outward
all over the circumference direction. At this time, a component of
velocity directed outward is added, and as illustrated in FIG. 18,
the steam F flows outward.
[0013] Part of the steam F spreading in the circumferential
direction flows toward an opening 312a of the drain discharge hole
312. The drain pipe 370 is influenced by the steam F flowing toward
the drain discharge hole 312. Then, during the normal operation of
the steam turbine, pressure fluctuation occurs in the drain pipe
370 between the opening 312a of the drain discharge hole 312 and
the shutoff valve 380.
[0014] In steam turbines, temperature and pressure of steam have
recently been increased for higher efficiency. Further, downsizing
and the like of devices are also being considered in order to
reduce a manufacturing cost. These increase the flow velocity of
the steam flowing between the valve element 323 of the steam
control valve 320 and the valve seat 360 and the flow velocity of
the steam flowing in the steam passage in the steam valve 300. This
tends to increase the pressure fluctuation occurring in the drain
pipe 370 due to the aforesaid steam F.
[0015] In the above-described conventional steam valve 300, the
operation under a narrowed valve opening degree of the steam
control valve 320, that is, under a low flow rate of the steam
passing through the steam valve 300, sometimes causes an abnormal
temperature increase of the drain pipe 370 more on the steam valve
300 side than the shutoff valve 380. A possible reason for this to
occur may be a thermoacoustic effect caused by the pressure
fluctuation in the drain pipe 370. Such an abnormal temperature
increase may cause breakage of the drain pipe.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a system diagram illustrating an example of a
power generation plant including a steam valve of a first
embodiment.
[0017] FIG. 2 is a perspective view of the steam valve of the first
embodiment.
[0018] FIG. 3 is a view illustrating a vertical cross section of
the steam valve of the first embodiment.
[0019] FIG. 4 is a perspective view of a flow direction changing
part in the steam valve of the first embodiment.
[0020] FIG. 5 is a perspective view of the flow direction changing
part with another structure, in the steam valve of the first
embodiment.
[0021] FIG. 6 is a view illustrating a vertical cross section of a
steam valve of a second embodiment.
[0022] FIG. 7 is a perspective view of a flow direction changing
part in the steam valve of the second embodiment.
[0023] FIG. 8 is a view illustrating an A-A cross section in FIG.
6.
[0024] FIG. 9 is a vertical cross-sectional view of a steam valve
of a third embodiment.
[0025] FIG. 10 is a perspective view of a flow direction changing
part in the steam valve of the third embodiment.
[0026] FIG. 11 is a view illustrating a B-B cross-section in FIG.
9.
[0027] FIG. 12 is a view illustrating a vertical cross section of a
steam valve of a fourth embodiment.
[0028] FIG. 13 is a view illustrating a vertical cross section of a
steam valve of a fifth embodiment.
[0029] FIG. 14 is a view illustrating a C-C cross section in FIG.
13.
[0030] FIG. 15 is a view illustrating a vertical cross section of a
steam valve of a sixth embodiment.
[0031] FIG. 16 is a view illustrating a vertical cross section of a
steam valve of a seventh embodiment.
[0032] FIG. 17 is a view illustrating a vertical cross section of a
steam valve of an eighth embodiment.
[0033] FIG. 18 is a view illustrating a vertical cross section of a
conventional steam valve.
DETAILED DESCRIPTION
[0034] Hereinafter, embodiments of the present invention are
described with reference to the drawings.
[0035] A steam valve of an embodiment includes: a first valve
element which is provided to be movable in an up and down direction
and adjusts a flow rate of steam; a second valve element which is
provided under the first valve element coaxially with the first
valve element to be movable in the up and down direction and shuts
off a flow of the steam; a valve seat with which the first valve
element and the second valve element come into and out of contact;
and a guide tube slidably supporting a valve rod including the
second valve element, and having a flange portion protruding
outward all over the circumferential direction, at a bottom side in
the steam valve.
[0036] The steam valve further includes: a casing housing the first
valve element, the second valve element, the valve seat, and the
guide tube; a drain discharge hole formed in a sidewall of the
casing at a bottom side; a drain pipe provided with a shutoff valve
and communicating with the drain discharge hole; and a flow
direction changing part which changes a direction in which the
steam having passed between the first valve element and the valve
seat and flowing along the guide tube, flows toward the drain
discharge hole.
First Embodiment
[0037] FIG. 1 is a system diagram illustrating an example of a
power generation plant 250 including a steam valve 10 of a first
embodiment.
[0038] As illustrated in FIG. 1, in the power generation plant 250,
steam heated in a superheater 252 of a boiler 251 is led to a
high-pressure turbine 254 via a main steam pipe 253 and the steam
valve 10 provided in the main steam pipe 253. Note that the steam
valve 10, which will be describe later, is a combined steam valve
having functions of a main stop valve and a steam control
valve.
[0039] Here, for example, in a combined cycle system in which a gas
turbine and a steam turbine are combined, the boiler 251 functions
as an exhaust heat recovery boiler. In this case, the boiler 251
functions by using exhaust gas from the gas turbine. In a case
where the combined cycle system including the gas turbine is not
constituted, the boiler 251 burns, for example, a fossil fuel to
use its heat.
[0040] The steam having worked in the high-pressure turbine 254
passes through a low-temperature reheat pipe 255 to be reheated in
a reheater 256 of the boiler 251 and is led to an
intermediate-pressure turbine 259 via a high-temperature reheat
pipe 257 and a reheat steam valve 258 provided in the
high-temperature reheat pipe 257.
[0041] The steam having worked in the intermediate-pressure turbine
259 is led to low-pressure turbines 261 via a crossover pipe 260.
The steam having worked in the low-pressure turbines 261 is
returned to water in a condenser 262. Then, the water is supplied
again to the superheater 252 of the boiler 251 by a feed pump 264
via a low-pressure feedwater heater 263 and a high-pressure
feedwater heater 265. Further, for example, the high-pressure
turbine 254, the intermediate-pressure turbine 259, and the
low-pressure turbines 261 drive a power generator 266 to make it
generate power.
[0042] Note that the structure of the power generation plant 250
described here is an example, and its structure is not limited to
this.
[0043] Next, the structure of the steam valve 10 of the first
embodiment is described.
[0044] FIG. 2 is a perspective view of the steam valve 10 of the
first embodiment. FIG. 3 is a view illustrating a vertical cross
section of the steam valve 10 of the first embodiment. FIG. 4 is a
perspective view of a flow direction changing part 80 in the steam
valve 10 of the first embodiment. Note that the steam valve 10
described here is the combined steam valve having the functions of
the main stop valve and the steam control valve, which is provided
in the main steam pipe.
[0045] As illustrated in FIG. 2 and FIG. 3, the steam valve 10 of
the first embodiment includes a casing 20 forming a steam passage
in which the steam led through a steam inlet 21 in, for example, a
horizontal direction is led vertically downward, and the steam led
vertically downward is led in, for example, the horizontal
direction to flow out through a steam outlet 22. An upper cover 25
covering the casing 20 from above is coupled to the top of the
casing 20 with fixing bolts 24. The upper cover 25 thus coupled to
the casing 20 with the fixing bolts 24 prevents the steam flowing
in the casing 20 from leaking outside.
[0046] As illustrated in FIG. 3, the casing 20 includes therein a
steam control valve 30 movable in an up and down direction when
driven from above and a main stop valve 40 provided under the steam
control valve 30 coaxially with the steam control valve 30 and
movable in the up and down direction when driven from under. The
casing 20 further includes therein a cylindrical strainer 50
disposed so as to surround the steam control valve 30 and the main
stop valve 40. The strainer 50 prevents a foreign object in the
steam led through the steam inlet 21 from flowing downstream. The
strainer 50 is, for example, a porous member or a porous plate.
[0047] The steam control valve 30 adjusts a flow rate of the steam.
In order to shut off the flow of the steam, the steam control valve
30 is closed. The steam control valve 30 includes a valve rod 31
and a valve element 32. The valve rod 31 penetrates through the
upper cover 25 and is supported to be movable in the up and down
direction when driven from above. The valve element 32 is annularly
provided on a lower end side of the valve rod 31 and has a dented
portion 33 in its lower surface. Around the outer periphery of the
valve element 32, a cylindrical guide 34 which guides the up and
down movement of the valve element 32 is provided. The valve
element 32 functions as a first valve element.
[0048] The main stop valve 40 shuts off the flow of the steam. The
main stop valve 40 includes a valve rod 41, a valve element 42, and
a guide tube 43. The valve rod 41 penetrates through a bottom
portion of the casing 20 and is supported so as to be movable in
the up and down direction when driven from under. The valve element
42 is provided on an upper end side of the valve rod 41 and
protrudes radially outward from the valve rod 41 all over the
circumferential direction. The valve element 42 is housed in the
dented portion 33 of the valve element 32 of the steam control
valve 30. That is, the valve element 42 is capable of entering and
exiting from the dented portion 33 of the valve element 32. The
valve element 42 functions as a second valve element.
[0049] The guide tube 43 is fixed to the bottom potion of the
casing 20 and is a cylinder at the center of which the valve rod 41
slidably penetrates therethrough. The guide tube 43 supporting the
valve rod 41 enables the main stop valve 40 to stably move in the
up and down direction.
[0050] The guide tube 43 includes a flange portion 43a protruding
outward all over the circumferential direction, at the bottom
portion side of the casing 20. An upper end portion of the flange
portion 43a is, for example, a slanting surface 43b slanting
downward as illustrated in FIG. 3 and FIG. 4. The shape of the
upper end portion of the flange portion 43a is not limited to this
and may be a curved surface protruding downward, for instance.
[0051] A height I of the flange portion 43a is an axial-direction
distance between a lower end of the flange portion 43a in contact
with a bottom surface of the casing 20 and an upper end of the
flange portion 43a. The height I of the flange portion 43a is, for
example, less than about three times an axial-direction distance J
between the bottom surface of the casing 20 and an upper end of a
later-described drain discharge hole 23.
[0052] Under the valve element 32 of the steam control valve 30 and
the valve element 42 of the main stop valve 40, a valve seat 60
which comes into contact with these valve elements is provided. The
valve seat 60 has a hollow annular shape having a steam passage 61
at its center. For example, when the valve element 32 of the steam
control valve 30 and the valve element 42 of the main stop valve 40
are pressed while in contact with the valve seat 60, the flow of
the steam can be shut off.
[0053] The casing 20 has, at its bottom side, the drain discharge
hole 23 which discharges a drain generated during warming for
putting the steam turbine into operation. As illustrated in FIG. 3,
the drain discharge hole 23 is formed in a sidewall 20a of the
casing 20 at the bottom side to extend laterally (in FIG. 3, a left
horizontal direction) because of arrangement and structural
reasons.
[0054] A drain pipe 70 which leads the drain outside is provided so
as to communicate with the drain discharge hole 23. The drain pipe
70 on the drain discharge hole 23 side is disposed in a
substantially horizontal direction, for instance. Note that the
substantially horizontal direction includes not only the horizontal
direction but also a direction inclined downward by about 0.5 to 2
degrees so as to make the drain flow down. The drain pipe 70 is
provided with a shutoff valve 71.
[0055] When the shutoff valve 71 is opened, the drain generated
during the warming is led to the condenser. Then, the shutoff valve
71 is closed after the warming. That is, while the steam turbine is
in operation, the drain pipe 70 constitutes a pipe part whose one
end communicates with the inside of the steam valve 10 and whose
other end is closed.
[0056] The steam valve 10 further includes a flow direction
changing part 80 which changes a direction in which the steam
having passed between the valve element 32 of the steam control
valve 30 and the valve seat 60 flows toward the drain discharge
hole 23. Here, an example where the flow direction changing part 80
is provided on a side surface 44 of the guide tube 43 is
described.
[0057] As illustrated in FIG. 3 and FIG. 4, the side surface 44 of
the guide tube 43 has, on its drain discharge hole side, a ridge
part 81 protruding outward and extending in the axial direction. As
illustrated in FIG. 3, a downstream end portion of the ridge part
81 faces the drain discharge hole 23. The ridge part 81 functions
as the flow direction changing part 80. Note that FIG. 4 is a view
of the flow direction changing part 80 seen from the drain
discharge hole 23 side.
[0058] The ridge part 81 has a wider circumferential width as it
goes more downstream as illustrated in FIG. 4, for instance. In the
example here, the ridge part 81 has a rectangular axial-direction
cross section as illustrated in FIG. 3, but the axial-direction
cross sectional shape of the ridge part 81 is not limited to any
particular shape. The ridge part 81 only needs to have a ridge
shape capable of dividing the steam F flowing along the guide tube
43, at an upper portion of the guide tube 43. For example, the
ridge part 81 may have a larger protrusion height as it goes more
downstream. In this case, the cross sectional shape of the ridge
part 81 in the cross section in FIG. 3 is trapezoidal.
[0059] Owing to the presence of the ridge part 81, the steam F
flowing along the guide tube 43 can be divided at the ridge part 81
as a boundary. Further, since the ridge part 81 has a larger
circumferential width as it goes more downstream, the direction of
the steam F flowing toward the drain discharge hole 23 facing the
downstream end of the ridge part 81 can be surely changed at the
downstream end. In other words, the increase of the circumferential
width of the ridge potion 81 as it goes more downstream makes it
possible to divide the flow of the steam F in a direction in which
the steam F gets more away from the drain discharge hole 23.
[0060] FIG. 5 is a perspective view of the flow direction changing
part 80 having another structure, in the steam valve 10 of the
first embodiment. Note that FIG. 5 is a view of the flow direction
changing part 80 seen from the drain discharge hole 23 side.
[0061] As illustrated in FIG. 5, in an upper end portion 82 of the
ridge part 81, the circumferential width of the end portion 82 may
be reduced in a tapered manner, for instance. This structure
enables the smooth division of the flow at a branching part of the
flow of the steam F, that is, at the end portion 82. This can
reduce a pressure loss in the end portion 82.
[0062] Next, the flow of the steam in the steam valve 10 is
described.
[0063] For example, the steam superheated by the superheater 252 of
the boiler 251 illustrated in FIG. 1 is supplied through the steam
inlet 21 illustrated in FIG. 3. The steam led through the steam
inlet 21 passes through the strainer 50 and passes between the
valve element 32 of the steam control valve 30 and the valve
element 42 of the main stop valve 40, and the valve seat 60.
[0064] At this time, the main stop valve 40 is fully opened, for
instance. That is, a gap between the valve element 42 of the main
stop valve 40 and the valve seat 60 is set to the maximum. Further,
the opening degree of the steam control valve 30 is set according
to a required flow rate of the steam. That is, the opening degree
is adjusted according to the flow rate of the steam that is to flow
in the gap between the valve element 32 of the steam control valve
30 and the valve seat 60. Here, a description is given, assuming a
condition under which the temperature of the drain pipe 70 is
likely to be abnormal, that is, a case where the flow rate of the
steam that is to flow s small. In this case, the valve opening
degree of the steam control valve 30 is small.
[0065] In the case where the valve opening degree of the steam
control valve 30 is small, the gap between the valve element 32 of
the steam control valve 30 and the valve seat 60 is narrow and thus
the flow of the steam is narrowed in this gap. Then, the velocity
of the steam increases. Partial steam F of the steam having passed
between the valve element 32 of the steam control valve 30 and the
valve seat 60 flows down along the side surface of the guide tube
43 as illustrated in FIG. 3 and FIG. 4.
[0066] Out of the flows of the steam F along the side surface of
the guide tube 43, the flow of the steam F reaching the ridge part
81 branches off at the ridge part 81 as the boundary. In FIG. 4,
the flow branches off to left and right of the ridge part 81 as the
boundary. The steam F that has branched off flows so as to be more
apart from the ridge part 81 as it goes more downstream.
[0067] Accordingly, at the downstream end of the ridge part 81,
there occurs no flow of the steam F toward the drain discharge hole
23 facing the downstream end. Consequently, since pressure
fluctuation of the flow of the steam F is not transmitted to the
drain pipe 70 via the drain discharge hole 23, the abnormal
temperature increase of the drain pipe 70 can be prevented. Here,
the flow of the steam F toward the drain discharge hole 23 refers
to a flow of the steam flowing into an opening 23a of the drain
discharge hole 23 mainly due to a dynamic pressure of the flow (the
same applies to the below).
[0068] The steam F having branched off then flows toward the steam
outlet 22 together with other steam. The steam discharged through
the steam outlet 22 is led to the high-pressure turbine 254.
[0069] Here, the description has been given assuming the case where
the valve opening degree of the steam control valve 30 is small,
but the same operation and effect can also be obtained in a case
where the valve opening degree of the steam control valve 30 is
large.
[0070] Here, a reason why the abnormal temperature increase of the
drain pipe 70 can be prevented by not transmitting the pressure
fluctuation of the flow of the steam F to the drain pipe 70 is
described.
[0071] Here, the frequency of pipe pressure fluctuation of a
cylinder whose inside diameter is R is represented by f(Hz). In
general, a heat flux q (W/m.sup.2) generated by a thermoacoustic
effect due to pressure fluctuation in a boundary layer near a pipe
wall is found by the expression (2), using a relation of the
expression (1) in which a pipe pressure fluctuation amplitude P is
divided by a pipe average pressure P.sub.0 and the obtained value
is made dimensionless (e.g. Arakawa, Kawahashi, Transactions of the
Japan Society of Mechanical Engineers, Vol. 62 No. 598, B(1996), p.
2238-2245).
[ exp . 1 ] P 1 = P / P 0 expression ( 1 ) [ exp .2 ] q = K .times.
( 1 .gamma. ) 2 ( .mu. a 2 .delta. / 5 ) P 1 2 expression ( 2 )
##EQU00001##
[0072] Here, P.sub.1 is a dimensionless pressure amplitude, K is a
constant determined by a pipe shape, .gamma. is a specific heat
ratio, .mu. is a coefficient of viscosity, a is a sound velocity,
and .delta. is the thickness of the boundary layer.
[0073] Since the inner perimeter of the cylinder is .pi.R, a heat
generation amount Q (W/m) per unit length of the cylinder is found
by the expression (3).
[ exp . 3 ] Q = K .times. ( 1 .gamma. ) 2 ( .mu. a 2 .delta. / 5 )
P 1 2 .pi. R expression ( 3 ) ##EQU00002##
[0074] Here, if an angular frequency .omega. is 2.pi.f, the
thickness .delta. of the boundary layer is found by the expression
(4).
[ exp . 4 ] .delta. = 5 v .omega. expression ( 4 ) ##EQU00003##
[0075] Here, .upsilon. is a coefficient of kinematic viscosity.
[0076] As is apparent from the expression (3), the heat generation
(thermoacoustic effect) due to the pipe pressure fluctuation is
proportional to a square of the dimensional pressure amplitude.
This shows that reducing the pipe pressure fluctuation can reduce
the heat generation.
[0077] As described above, according to the steam valve 10 of the
first embodiment, the presence of the flow direction changing part
80 (ridge part 81) can prevent the pressure fluctuation of the flow
of the steam F along the side surface of the guide tube 43 from
being transmitted to the drain pipe 70 via the drain discharge hole
23. This can prevent the abnormal temperature increase of the drain
pipe 70, enabling to provide the highly reliable steam valve
10.
Second Embodiment
[0078] FIG. 6 is a view illustrating a vertical cross section of a
steam valve 11 of a second embodiment. FIG. 7 is a perspective view
of a flow direction changing part 80 in the steam valve 11 of the
second embodiment. FIG. 8 is a view illustrating an A-A cross
section in FIG. 6. Note that, in the following embodiment, the same
components as those in the structure of the steam valve 10 of the
first embodiment are denoted by the same reference signs and
duplicated description is not given or simplified.
[0079] The structure of the steam valve 11 of the second embodiment
is the same as the structure of the steam valve 10 of the first
embodiment except the structure of the flow direction changing part
80. Therefore, the flow direction changing part 80 is mainly
described here.
[0080] As illustrated in FIG. 6 to FIG. 8, the flow direction
changing part 80 includes a tubular body 90 whose one end is
coupled to the drain discharge hole 23 and whose other end has an
upper half tip 91 protruding in the length direction (longitudinal
direction) beyond its lower half tip 92. The flow direction
changing part 80 further includes a communication hole 93 formed in
the tubular body 90 in the length direction and communicating with
the drain discharge hole 23. For example, the communication hole 93
can be formed on a lower half side of the tubular body 90 all along
the length direction. For example, the tubular body 90 is
constituted by forming the communication hole 93 in a column whose
other end has the aforesaid shape.
[0081] Here, assuming, for example, that the cross sectional shape
is a circle in the cross section illustrated in FIG. 8, the upper
half side refers to an upper side of the circle two-divided
vertically by a horizontal straight line passing the center of the
circle. Assuming that the cross sectional shape in the cross
section illustrated in FIG. 8 is a circle, the lower half side
refers to a lower side of the circle two-divided vertically by the
horizontal straight line passing the center of the circle.
[0082] An end portion of the communication hole 93 on a side
different from the drain discharge hole 23 side opens in the steam
valve 11. However, since the upper half tip 91 of the tubular body
90 protrudes toward the guide tube 43 beyond the lower half tip 92,
the end portion of the communication hole 93 on, for example, the
tip side cannot be seen from above. Incidentally, the drain
generated during the warming for putting the steam turbine into
operation passes through the communication hole 93 to flow into the
drain discharge hole 23.
[0083] The tubular body 90 has a cylindrical shape, for instance.
As illustrated in FIG. 6, a height H of the tubular body 90 is
smaller than the height I of the flange portion 43a of the guide
tube 43. The tubular body 90 is fixed to the bottom surface of the
casing 20 by welding or the like, for instance. Further, the
example where the cross section of the communication hole 93 is
rectangular is given here, but this cross section may be
circular.
[0084] In the steam valve 11 including such a flow direction
changing part 80, the partial steam F of the steam having passed
between the valve element 32 of the steam control valve 30 and the
valve seat 60 flows along the side surface of the guide tube 43.
When the steam F flows along the flange portion 43a of the guide
tube 43, a component of velocity directed outward is added, and as
illustrated in FIG. 6, the steam F flows outward. Part of the flow
of the steam F flowing outward flows down onto the tubular body 90
to flow along an outer surface of the tubular body 90. At this
time, the flow of the steam F collides with the top of the tubular
body 90, and as illustrated in FIG. 8, branches off. In FIG. 8, the
flow of the steam F branches off to left and right of the tubular
body 90. That is, the flow direction of the steam F is changed by
the tubular body 90.
[0085] The steam F flowing down onto the tubular body 90 thus once
collides with the tubular body 90 to be changed in its flow
direction. The height H of the tubular body 90 is smaller than the
height I of the flange portion 43a of the guide tube 43, and the
tip-side end portion of the communication hole 93 is covered by the
protruding upper half tip 91. Accordingly, the flow of the steam F
toward the communication hole 93 does not occur. Consequently,
since the pressure fluctuation of the flow of the steam F is not
transmitted to the drain pipe 70 via the communication hole 93 and
the drain discharge hole 23, the abnormal temperature increase of
the drain pipe 70 can be prevented.
[0086] As described above, according to the steam valve 11 of the
second embodiment, the presence of the flow direction changing part
80 can prevent the pressure fluctuation of the flow of the steam F
along the side surface of the guide tube 43 from being transmitted
to the drain pipe 70 via the drain discharge hole 23. This can
prevent the abnormal temperature increase of the drain pipe 70,
enabling to provide the highly reliable steam valve 11.
Third Embodiment
[0087] FIG. 9 is a view illustrating a vertical cross section of a
steam valve 12 of a third embodiment. FIG. 10 is a perspective view
of a flow direction changing part 80 in the steam valve 12 of the
third embodiment. Note that FIG. 10 is a view of the flow direction
changing part 80 seen from the drain discharge hole 23 side. FIG.
11 is a view illustrating a B-B cross section in FIG. 9
[0088] The structure of the steam valve 12 of the third embodiment
is the same as the structure of the steam valve 10 of the first
embodiment except the structure of the flow direction changing part
80. Therefore, the flow direction changing part 80 is mainly
described here.
[0089] As illustrated in FIG. 9 and FIG. 10, the flow direction
changing part 80 includes groove portions 100 formed in the side
surface of the guide tube 43 on the drain discharge hole 23 side
and arranged in the axial direction in a plurality of tiers. For
example, these groove portions 100 are each formed along a half
circumference of the side surface of the guide tube 43 which is the
cylinder, that is, along 1/2 of the circumference.
[0090] Here, the side surface of the guide tube 43 on the drain
discharge hole 23 side is described. As illustrated in FIG. 11, a
straight line parallel to the center line of the drain discharge
hole 23 and passing the center O of the guide tube 43 is
represented by L. Note that the center O of the guide tube 43 is
also the center of the valve rod 41 of the main stop valve 40.
[0091] In this case, a side surface corresponding to regions each
having a center at the center O of the guide tube 43 and each
having an angle .theta. in each direction from the straight line L
(region having an angle 2.theta.) is defined as the side surface of
the guide tube 43 on the drain discharge hole 23 side. In the
above-described example, this angle .theta. is 90 degrees, and the
range of the side surface of the guide tube 43 on the drain
discharge hole 23 side is the half circumference of the side
surface of the guide tube 43 which is the cylinder.
[0092] The angle .theta. is preferably set to 15 to 90 degrees, for
instance. Setting the angle .theta. within this range makes it
possible to reduce the velocity of the flow toward the drain
discharge hole 23, out of the flows of the steam F along the side
surface of the guide tube 43.
[0093] In the steam valve 12 including such a flow direction
changing part 80, the partial steam F of the steam having passed
between the valve element 32 of the steam control valve 30 and the
valve seat 60 flows along the side surface of the guide tube 43.
The steam F flowing along the side surface of the guide tube 43 on
the drain discharge hole 23 side enters the inside of the groove
portions 100 as illustrated in FIG. 9 and FIG. 10 and is disturbed
on the surfaces of the groove portions 100 to form vortices.
Consequently, the flow direction of the steam F is changed, and in
addition, the flow of the steam F is damped, so that the velocity
of the steam F decreases. Then, the steam F flowing down up to the
downstream side of the guide tube 43 has a low velocity.
[0094] Even if the flow of the steam F having such a low velocity
reaches the drain discharge hole 23, the pressure fluctuation
transmitted to the drain pipe 70 via the drain discharge hole 23 is
very small. This can prevent the abnormal temperature increase of
the drain pipe 70.
[0095] As described above, according to the steam valve 12 of the
third embodiment, the presence of the flow direction changing part
80 makes it possible to not only change the flow direction in which
the steam flows toward the drain discharge hole 23 but also damp
the flow of the steam F to decrease the velocity of the flow.
Accordingly, the pressure fluctuation transmitted to the drain pipe
70 via the drain discharge hole 23 is small. This can prevent the
abnormal temperature increase of the drain pipe 70, enabling to
provide the highly reliable steam valve 12.
Fourth Embodiment
[0096] FIG. 12 is a view illustrating a vertical cross section of a
steam valve 13 of a fourth embodiment. The structure of the steam
valve 13 of the fourth embodiment is the same as the structure of
the steam valve 10 of the first embodiment except the structure of
the flow direction changing part 80. Therefore, the flow direction
changing part 80 is mainly described here.
[0097] As illustrated in FIG. 12, the flow direction changing part
80 is the valve seat 60 whose inner peripheral surface is curved
such that a passage cross section of the steam passage 61 at the
center of the valve seat 60 becomes larger as it goes more downward
from a throat portion S of the steam passage 61. Here, the throat
portion S is a cross section where the passage cross section
becomes smallest in the steam passage at the center of the valve
seat 60.
[0098] For example, with the passage sectional area at the throat
portion S being 1, the passage sectional area at an outlet of the
steam passage 61 is preferably about 2.2 to 3 times. By setting it
within this range, the flow of the steam having passed between the
valve element 32 of the steam control valve 30 and the valve seat
60 can spread outward. The curve of the inner peripheral surface of
the valve seat 60 in order for the passage sectional area at the
outlet of the steam passage 61 to fall within the aforesaid range
is preferably gentle enough to prevent the separation of the
flow.
[0099] In the steam valve 12 including such a flow direction
changing part 80, the steam having passed between the valve element
32 of the steam control valve 30 and the valve seat 60 flows along
the inner peripheral surface of the valve seat 60. Then, at the
outlet of the valve seat 60, a flow spreading outward is
obtained.
[0100] In this case, the flow of the steam along the side surface
of the guide tube 43 is minimized. Accordingly, the flow of the
steam flowing along the side surface of the guide tube 43, and on
the downstream side, flowing toward the drain discharge hole 23 is
minimized. Accordingly, the pressure fluctuation of the flow of the
steam is not transmitted to the drain pipe 70 via the drain
discharge hole 23. This can prevent the abnormal temperature
increase of the drain pipe 70.
[0101] The flow having passed through the steam passage 61 of the
valve seat 60 to spread outward spreads in the steam passage
downstream of the valve seat 60 to flow toward the steam outlet
22.
[0102] As described above, according to the steam valve 13 of the
fourth embodiment, the presence of the flow direction changing part
80 can minimize the flow of the steam along the side surface of the
guide tube 43. Accordingly, the pressure fluctuation due to the
steam flowing toward the drain discharge hole 23 is not transmitted
to the drain pipe 70. This can prevent the abnormal temperature
increase of the drain pipe 70, enabling to provide the highly
reliable steam valve 13.
Fifth Embodiment
[0103] FIG. 13 is a view illustrating a vertical cross section of a
steam valve 14 of a fifth embodiment. FIG. 14 is a view
illustrating a C-C section in FIG. 13. The structure of the steam
valve 14 of the fifth embodiment is the same as the structure of
the steam valve 10 of the first embodiment except the structure of
the flow direction changing part 80. Therefore, the flow direction
changing part 80 is mainly described here.
[0104] As illustrated in FIG. 13 and FIG. 14, the flow direction
changing part 80 is constituted by narrowing a gap between the
sidewall 20a of the casing 20 on the side where the drain discharge
hole 23 is formed and the guide tube 43. For example, as
illustrated in FIG. 13 and FIG. 14, the sidewall 20a of the casing
20 on the side where the drain discharge hole 23 is formed
protrudes toward the guide tube 43, so that the gap between the
sidewall 20a and the guide tube 43 can be small.
[0105] Here, as illustrated in FIG. 13, in the gap, an interval
between the sidewall 20 a of the casing 20 and the flange portion
43a of the guide tube 43 is smallest, in the vertical section of
the steam valve 14 including the center of the drain discharge hole
23. A distance D of this smallest gap is set to the minimum
distance allowing the drain to be led to the drain discharge hole
23, for instance.
[0106] In the steam valve 14 including such a flow direction
changing part 80, the partial steam F of the steam F having passed
between the valve element 32 of the steam control valve 30 and the
valve seat 60 flows along the side surface of the guide tube 43.
However, the gap between the sidewall 20a of the casing 20 where
the drain discharge hole 23 is formed and the guide tube 43 is
small. Accordingly, the steam F flows along the side surface of the
guide tube 43 so as to keep away from this gap.
[0107] Accordingly, there occurs no flow of the steam F toward the
drain discharge hole 23. Consequently, the pressure fluctuation of
the flow of the steam F is not transmitted to the drain pipe 70 via
the drain discharge hole 23. This can prevent the abnormal
temperature increase of the drain pipe 70.
[0108] As described above, according to the steam valve 14 of the
fifth embodiment, owing to the presence of the flow direction
changing part 80, there occurs no flow of the steam F toward the
drain discharge hole 23. Accordingly, there is no transmission of
the pressure fluctuation to the drain pipe 70 due to the steam
flowing toward the drain discharge hole 23. This can prevent the
abnormal temperature increase of the drain pipe 70, enabling to
provide the highly reliable steam valve 14.
[0109] In the example described here, the sidewall 20a of the
casing 20 on the side where the drain discharge hole 23 is formed
protrudes toward the guide tube 43 to narrow the gap between the
sidewall 20a and the guide tube 43, but this structure is not
restrictive.
[0110] For example, in a cross section corresponding to the cross
section illustrated in FIG. 13, a structure composed of the steam
control valve 30, the main stop valve 40, the valve seat 60, and
the strainer 50 may be put closer to the sidewall 20a of the casing
20 on the side where the drain discharge hole 23 is formed. That
is, the center axis of the aforesaid structure may be deviated
toward the drain discharge hole 23 from the vertical center axis of
the steam passage downstream of the valve seat 60. In this case as
well, the same operation and effect as the operation and effect in
the steam valve 14 illustrated in FIG. 13 can be obtained.
Sixth Embodiment
[0111] FIG. 15 is a view illustrating a vertical cross section of a
steam valve 15 of a sixth embodiment. The structure of the steam
valve 15 of the sixth embodiment is the same as the structure of
the steam valve 10 of the first embodiment except the structure of
the flow direction changing part 80. Therefore, the flow direction
changing part 80 is mainly described here.
[0112] As illustrated in FIG. 15, the flow direction changing part
80 is constituted by making the outside diameter of the sidewall of
the guide tube 43 above the flange portion 43a equal to the outside
diameter of the flange portion 43a. Here, in FIG. 15, the shape
before the outside diameter of the sidewall above the flange
portion 43a is increased is illustrated by the broken line. The
outside diameter of the sidewall of the guide tube 43 above the
flange portion 43a may be larger than the outside diameter of the
flange portion 43a. That is, the outside diameter of the sidewall
of the guide tube 43 above the flange portion 43a is set equal to
or larger than the outside diameter of the flange portion 43a.
[0113] In the steam valve 15 including such a flow direction
changing part 80, the partial steam F of the steam F having passed
between the valve element 32 of the steam control valve 30 and the
valve seat 60 flows along the side surface of the guide tube 43.
The steam F flowing along the side surface of the guide tube 43
flows substantially vertically downward to collide with the bottom
surface of the casing 20. The steam F which has collided with the
bottom surface of the casing 20 flows toward the steam outlet 22
together with other steam.
[0114] Accordingly, there occurs substantially no flow of the steam
F toward the drain discharge hole 23. Consequently, the pressure
fluctuation of the flow of the steam F is not transmitted to the
drain pipe 70 via the drain discharge hole 23. This can prevent the
abnormal temperature increase of the drain pipe 70.
[0115] As described above, according to the steam valve 15 of the
sixth embodiment, owing to the presence of the flow direction
changing part 80, there occurs substantially no flow of the steam F
toward the drain discharge hole 23. Accordingly, there is no
transmission of the pressure fluctuation to the drain pipe 70 due
to the steam flowing toward the drain discharge hole 23. This can
prevent the abnormal temperature increase of the drain pipe 70,
enabling to provide the highly reliable steam valve 15.
Seventh Embodiment
[0116] FIG. 16 is a view illustrating a vertical cross section of a
steam valve 16 of a seventh embodiment. The structure of the steam
valve 16 of the seventh embodiment is the same as the structure of
the steam valve 10 of the first embodiment except the structure of
the flow direction changing part 80. Therefore, the flow direction
changing part 80 is mainly described here.
[0117] As illustrated in FIG. 16, the flow direction changing part
80 is constituted by making the height I of the flange portion 43a
of the guide tube 43 three times or more the axial-direction
distance J between the bottom surface of the casing 20 and the
upper end of the drain discharge hole 23. Note that the axial
direction is synonymous with the axial direction of the steam
control valve 30 and the main stop valve 40. That is, the axial
direction is the up and down direction in FIG. 16.
[0118] The height I of the flange portion 43a, which is ordinarily
set less than three times the distance J as described above, falls
here within a range exceeding this range. That is, the height I of
the flange portion 43a in the seventh embodiment is set larger than
the aforesaid ordinary height I of the flange portion 43a.
[0119] In the steam valve 16 including such a flow direction
changing part 80, the partial steam F of the steam F having passed
between the valve element 32 of the steam control valve 30 and the
valve seat 60 flows along the side surface of the guide tube 43.
The height I of the flange portion is larger than the ordinary
height I of the flange portion 43a. Accordingly, more upstream than
ordinarily, the component of velocity directed outward is added and
as illustrated in FIG. 16, the steam F flows outward.
[0120] Accordingly, there occurs substantially no flow of the steam
F toward the drain discharge hole 23. Consequently, the pressure
fluctuation of the flow of the steam F is not transmitted to the
drain pipe 70 via the drain discharge hole 23. This can prevent the
abnormal temperature increase of the drain pipe 70.
[0121] As described above, according to the steam valve 16 of the
seventh embodiment, owing to the presence of the flow direction
changing part 80, there occurs substantially no flow of the steam F
toward the drain discharge hole 23. Accordingly, there is no
transmission of the pressure fluctuation to the drain pipe 70 due
to the steam flowing toward the drain discharge hole 23. This can
prevent the abnormal temperature increase of the drain pipe 70,
enabling to provide the highly reliable steam valve 16.
Eight Embodiment
[0122] FIG. 17 is a view illustrating a vertical cross section of a
steam valve 17 of an eighth embodiment. The steam valve 17 of the
eighth embodiment does not include the flow direction changing part
80 unlike those of the above-described embodiments. In the steam
valve 17 of the eighth embodiment, the structure of a drain
discharge hole 110 is different from the structure of the drain
discharge hole 23 of the above-described embodiments. Therefore,
the drain discharge hole 110 is mainly described here.
[0123] As illustrated in FIG. 17, the drain discharge hole 110 is
formed in a bottom wall 20b of the casing 20. The drain discharge
hole 110 includes a vertical hole 111 extending vertically downward
from an inner surface 20c of the bottom wall 20b and a lateral hole
112 communicating with the vertical hole 111 and laterally
penetrating. The lateral hole 112 is formed in the horizontal
direction, for instance. Alternatively, the lateral hole 112 may be
formed so as to slant downward toward the side where the lateral
hole 112 penetrates.
[0124] Here, the drain discharge hole 110 is formed with a hole
diameter large enough for the drain to pass therethrough. In view
of preventing the steam from entering the drain discharge hole 110,
the drain discharge hole 110 preferably has the minimum hole
diameter allowing the passage of the drain.
[0125] On a side surface of the bottom wall 20b through which the
lateral hole 112 penetrates, the drain pipe 70 is provided so as to
communicate with the lateral hole 112. The drain pipe 70 is
provided with the shutoff valve 71.
[0126] In the steam valve 17 including such a drain discharge hole
110, the partial steam F of the steam F having passed between the
valve element 32 of the steam control valve 30 and the valve seat
60 flows along the side surface of the guide tube 43. When the
steam F flows along the flange portion 43a of the guide tube 43,
the component of velocity directed outward is added, and as
illustrate in FIG. 17, the steam F flows outward.
[0127] Accordingly, there occurs substantially no flow of the steam
F toward an opening 111a of the vertical hole 111. Consequently,
there is no transmission of the pressure fluctuation to the drain
pipe 70 due to the steam flowing toward the drain discharge hole
110. Note that the flow of the steam F toward the drain discharge
hole 110 (opening 111a) refers to a flow of the steam flowing into
the opening 111a of the drain discharge hole 110 mainly due to the
dynamic pressure of the flow. Further, for example, even if the
partial steam F enters the vertical hole 111, the steam F does not
enter the lateral hole 112 bending perpendicularly from the
vertical hole 111, owing to a large pressure loss. For the
above-described reasons, it is possible to prevent the abnormal
temperature increase of the drain pipe 70 and provide the highly
reliable steam valve 16.
[0128] As described above, according to the steam valve 17 of the
eighth embodiment, owing to the above-described structure of the
drain discharge hole 110, there occurs no flow of the steam F
toward the drain discharge hole 110 (opening 111a). Accordingly,
there is no transmission of the pressure fluctuation to the drain
pipe 70 due to the steam flowing toward the drain discharge hole
110. This can prevent the abnormal temperature increase of the
drain pipe 70, enabling to provide the highly reliable steam valve
15.
[0129] Here, as an example of a steam valve, the above embodiments
describe the steam valve which is provided in the main steam pipe
and in which the steam control valve 30 and the main stop valve 40
are combined. However, the structures of the embodiments are
applicable also to, for example, a steam valve which is provided in
the high-temperature reheat pipe and in which an intercept valve
and a reheat steam stop valve are combined. In this case, the same
operation and effect as those when the structures of the
embodiments are applied to the steam valve in which the steam
control valve 30 and the main stop valve 40 are combined can be
obtained.
[0130] According to the above-described embodiments, it is possible
to prevent an abnormal temperature increase of a drain pipe to
provide a highly reliable steam valve.
[0131] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *