JPH0362881B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to valves, and more particularly to control valves for steam turbines subjected to cyclic loading.

Steam turbines operate under base load for long periods of time with negligible temperature transients. However, when used for peak loads, parts are subjected to a hot start after a day/night outage, a medium start after a weekend outage, and a cold start after a long outage. As a result, large temperature changes occur at the control valves that control the amount of steam entering the turbine. This transient high temperature generates repetitive stress. In order to extend the service life of a control valve, it is necessary to change the internal structure of the control valve.

Generally, a turbine control valve constructed in accordance with the present invention has a body with an internal cavity. The interior cavity has a generally circular, elongated first aperture on one side and a generally circular, elongated first aperture opposite the first aperture with a valve seat formed therein. 2 openings and a third opening for introducing steam into the internal cavity. The control valve has a valve body that mates with the valve seat to close the second opening, and a valve lid having a generally cylindrical portion and a flange at one end of the cylindrical portion. . The flange includes a circumferential sealing surface proximate the first opening. The valve lid has a centrally located through-axis bore and two counterbore holes extend inwardly from the unflangeed end of the valve lid. The first counterbore terminates in a corner that is long and has a large radius of curvature, and the second counterbore is deep enough to receive the valve plug and terminates in a corner that also has a radius of curvature. . The cylindrical portion of the valve lid includes a raised first portion on the outer surface proximate the flange;
and a raised second portion on the same outer surface spaced apart from the first portion. The diameter of the first portion is greater than the diameter of the second portion. The first opening of the body also has first and second raised portions that engage with the first and second portions of the cylindrical portion of the valve lid, respectively. It matches. The gaps between the mating parts are very small. The control valve also includes a hardened sleeve tightly fitted into a first counterbored hole in the valve lid, a stem guide bushing secured in an axial hole in the valve cover, and a stem guide bushing that slides into the stem guide bush. a movably disposed valve stem; and a valve slidably disposed in the hardened sleeve and secured to the valve stem and the valve body such that sliding movement between the valve stem and the valve stem is small. Equipped with a body guide. The valve body has a through port in the center, and the valve stem closes the through port when a valve closing force is applied to the valve body via the valve stem, and the valve stem closes the through port when a valve closing force is applied to the valve body via the valve stem. By opening the through port at a given time, a control valve that can operate under cyclic loads where large temperature changes are applied to the valve body is provided.

The objects and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

Referring to the drawings and in particular to FIG. 1, a control valve 1 of a steam turbine (not shown) used for peak loads is shown. The control valve 1 is
Main body 3 with a large cavity (internal cavity) 5 inside
The cavity 5 has a substantially circular long first opening 7 on one side thereof (the top side in FIG. 1);
a second substantially circular opening 9 with a valve seat 11 opposite the first opening 7 and a second opening 9 for introducing steam;
It is provided with a third opening 13 that coincides with the center of the cavity 5.

The valve body 15 is disposed within the cavity 5 in combination with the valve seat 11 to control the steam flow between the valve seat 11 and the valve body 15 .

A valve cover 17 disposed in the first opening 7 has a generally cylindrical portion 19 and a flange 21 integrally formed on one side of one end of the cylindrical portion 19 . The flange 21 has a circumferential sealing surface 23 that engages with a circumferential sealing surface 25 disposed on the main body 3 so as to surround the first opening 7 . The gasket 27 has a circumferential sealing surface 23,
25 to form a pressure-tight seal. The valve cover 17 has a through shaft hole 29 in the center position, and two counterbore holes 31 and 33 are provided in the flange 2.
1 extends inward from the tip of the valve lid 17 without the valve cover 17. The first counterbore hole 31 is connected to the second counterbore hole 3
The corner 35 has a greater depth or length and a larger radius of curvature than the corner 35. Second counterbore hole 33
has a depth sufficient to receive the valve body 15 and terminates in a corner 37 which also has a radius of curvature.

The cylindrical portion 19 of the valve lid 17 has a raised first land (first portion) 39 on its outer surface adjacent to the flange 21 and a raised first land (first portion) 39 on the outer surface at a distance from the first land 39. A second land (second portion) 41 is provided. The first land 39 has a larger diameter than the second land 41. First opening 7 of main body 3
are the first land 39 and the second land of the cylindrical portion 19.
A first land (first land) that engages with the land 41, respectively.
portion) 43 and a second land (second portion) 45. Lands 39, 41, 4 that engage with each other
Between 3 and 45, generally 0.05~0.15mm (0.002~
There is a small gap measuring 0.006 inch).

A hardened nitroalloy sleeve (liner) 47 is tightly fitted into the first counterbore 31 by an interference fit. A stiffening pin 49 extends through the wall of the valve lid 17 and also extends through the sleeve 47 to prevent rotation of the sleeve 47 relative to the valve lid 17. It is partially inserted. The pin 49 is held in place by a disc 51 tack welded to the valve lid 17.

The valve stem guide bush 53 is fixed in the through shaft hole 29 of the valve cover 17 by an engaging screw portion 55, and the valve stem guide bush 53 is formed with a hexagonal head for receiving a wrench. .

The valve stem 57 is slidably disposed in the valve stem guide bush 53, and the valve body guide 59 is attached to the valve stem 57.
It is slidably disposed in the hardened sleeve 47 and fixed to the valve stem 57 and the valve body 15 so that the sliding movement between the valve body guide 59 and the valve body guide 59 is slight.
The valve body 15 is provided with a through port 61 at the center position. The valve rod 57 closes the through port 61 when a valve closing force is applied to the valve rod 57, and opens the through port 61 when a valve opening force is applied to the valve rod 57.

The control valve described above exhibits improved cyclic load capability due to the large radius of curvature of the inner wall corners of the valve lid, which minimizes the peak stresses in the valve lid wall during cyclic operation, and the valve stem guide bushings. The engagement area between the valve lid and the valve lid is separated from the corners with a large radius of curvature in an area of relatively low thermal stress, and the tight clearance between the lands maintains the strength of the valve lid and protects the outer surface of the valve lid. The steam is allowed to flow through the gap along the gasket to the gasket;
The valve lid is heated more evenly, and the difference in diameter between the lands also makes it easier to remove the valve lid from a rusted body after operation in a steam environment.

[Brief explanation of drawings]

Figure 1 is a partial cross-sectional view of a steam turbine control valve manufactured for peak load operation; Figure 2 is an enlarged view of a portion of the valve cover and stem guide bushing of the control valve shown in Figure 1; FIG. Explanation of symbols, 1... Control valve, 3... Main body, 5...
...Vacancy (internal space), 7...First opening, 9...Second opening, 11...Valve seat, 13...Third opening, 15
... Valve body, 17 ... Valve lid, 19 ... Cylindrical part, 21 ... Flange, 23 ... Circumferential sealing surface,
25...Circumferential sealing surface, 29...Through shaft hole, 3
1, 33...first and second counterbore holes, 35, 37...
...Corner, 39,43...1st land (first part), 41,45...2nd land (second part), 4
7... Surface hardened sleeve, 53... Valve stem guide bush, 57... Valve stem, 59... Valve body guide, 6
1...Through port.

Claims (1)

Claims: 1. A body with an internal cavity, the internal cavity having a generally circular, elongated first opening on one side of the internal cavity; a second generally circular aperture opposite the aperture and having a valve seat formed therein; and a third aperture for introducing steam into the interior cavity; the body, the opening having a circumferential sealing surface adjacent the internal cavity; a valve body mating with the valve seat to close the second opening; and a substantially cylindrical portion. an integral flange at one end of the cylindrical portion;
the flange includes a circumferential sealing surface that engages the circumferential sealing surface proximate the first opening;
the valve lid includes a centrally located through-axis bore having two counterbores extending inwardly from the flanged end, a first of the counterbores terminating in a long, large radius corner; The second counterbore is deep enough to receive the valve body and terminates in a corner also having a radius of curvature, the cylindrical portion being a raised first portion on the outer surface proximate the flange. and a raised second portion on the same outer surface spaced apart from the first portion, the first portion having a diameter greater than the second portion. and the first opening of the main body also includes an elevated first portion and a second raised portion, the first and second portions extending from the first portion of the cylindrical portion of the valve lid. , second
a surface hardened sleeve that fits tightly into the first counterbored hole in the valve lid, the sleeve fitting tightly into the first counterbore in the valve lid; a valve stem guide bushing fixed in the shaft hole of the lid; a valve stem slidably disposed in the valve stem guide bush; and the surface hardening so that sliding movement between the valve stem is small. a valve body guide slidably disposed in a sleeve and fixed to the valve body, the valve body having a through port in a central portion, and the valve stem being closed to the valve body. By closing the through port when a valve force is applied via the valve stem and opening the through port when a valve opening force is applied to the valve body via the valve stem, a large force is applied to the valve body. A turbine control valve capable of operating under cyclic loads where temperature changes occur.