JP2550439B2 - Control valve - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control valve suitable for use in a startup bypass system of a commercial boiler.

[0002]

2. Description of the Related Art A high differential pressure control valve is used in a startup bypass system of a commercial boiler. This high differential pressure control valve
In particular, as represented by the heater bypass valve, at the time of starting the boiler, it controls the flow rate and pressure of a wide range of ultra-high temperature and high-pressure fluid from high-pressure cold water to a sub-critical or super-critical pressure steam through a temperature raising and boosting process. Moreover, during normal operation of the boiler,
A function as a stop valve for shutting off the main steam pipe system on the high pressure side of the boiler and the flash tank or the condenser side on the low pressure side is also required at the same time, and therefore, it is exposed to extremely severe usage conditions.

By the way, the applicant of the present invention filed Japanese Patent Application Laid-Open No. 62-137484.
A control valve as described in Japanese Patent Publication is proposed.

This prior art is as shown in FIG.
A cage 2 is provided coaxially around the valve body 1.
A small hole 2A that is opened and closed by the outer peripheral closing surface 1A of the valve body 1 and forms a downward flow angle of the fluid streamline is formed in the small hole that is not blocked by the valve body 1 of the cage 2. Two
The flow rate of the fluid is controlled by A.

In this prior art, (a) a jet guide for guiding the fluid jet flowing out from the small hole 2A downwardly by reducing the diameter of the valve body 1 below the outer peripheral closing surface 1A with a downward slope. A seat surface 1C which forms the surface 1B and is contacted with and separated from the valve seat 2B (b).
At the lower part of the jet flow guide surface 1B of the valve body 1.
The fluid guided by the jet flow guide surface 1B is provided so as not to directly collide with the flow guide surface 1B while forming a step from B and retracting toward the valve center axis side.

Therefore, according to this prior art, even if water vaporizes just below the small hole of the cage which is the throttle, the water is diffused by the small hole, and the inclination angle of the small hole and the valve body are small. Since it is smoothly discharged downward by the jet flow guide surface, there is no occurrence of an extremely short period cavity growth phenomenon which is a cause of severe cavitation vibration. As a result, it is possible to significantly reduce the severe vibration during control.

[0007]

However, the prior art has the following problems.

A seat surface 1C is provided below the jet guide surface 1B.
Since it is exposed, if the gradient θ1 of the jet guide surface 1B is made smaller to approach the gradient θ2 of the small hole 2A, the jet from the small hole 2A passes through the jet guide surface 1B and the seat surface 1C.
Will collide with. Therefore, the gradient θ of the jet guide surface 1B
1 needs to be made large to some extent, and as a result, a part of the jet from the small hole 2A (P in FIG. 4A) is strongly bent downward toward the valve seat 2B by the jet guide surface 1B, It collides with the valve seat 2B and causes erosion of the valve seat 2B.

A seat surface 1C is provided below the jet guide surface 1B.
Since it is provided so as to be exposed, when the inclination α of the seat surface 1C and the valve seat 2B is increased, the seat surface 1C largely projects outward, and the jet flow guided by the jet guide surface 1B collides with the seat surface. Will end up. Therefore, the seat surface 1C
And the gradient α of the valve seat 2B cannot be made large, and as a result, the collision angle of the flow against the valve seat 2B becomes close to a right angle, and the valve seat 2B
The collision force acting on B becomes large, causing erosion of the valve seat 2B.

The above is a seat surface 1C or a valve seat 2
The damage of B makes it difficult to obtain a leak-free, reliable deadline when the valve is fully closed.

An object of the present invention is to reduce the occurrence of severe vibration during control and improve the shutoff performance when the valve is fully closed.

[0012]

According to the present invention, there is provided a casing having an inlet passage, an outlet passage and a valve chamber, a valve seat formed in the valve chamber of the casing, and supported by the casing.
It has a valve body which is movable toward or away from the valve chamber of the housing relative to the valve seat, thereby enabling connecting and disconnecting the valve seat a seat surface provided on the valve body, wherein A cage is provided coaxially around the valve body, and a small hole is formed in the cage that is opened and closed by the outer peripheral closing surface of the valve body and the fluid flow line forms a downward outflow angle. In a control valve in which a jet guide surface is formed at a lower portion of the outer peripheral closing surface with a downward gradient that is substantially the same as the outflow angle of the small hole and guides a fluid jet flowing out from the small hole downward . , The jet guide surface of the valve body
From the lower part of the outer peripheral closing surface of the valve body to the seat surface of the valve body
A control valve which is formed so as to surround the valve , and the seat surface and the valve seat are provided with a slope greater than the slopes of the small hole and the jet flow guide surface.

[0013]

According to the present invention, there are the following actions.

Even if water vaporizes just below the small hole provided in the inner cage, it is diffused by the small hole and is smoothly discharged downward due to the small hole having a downward slope and the jet guide surface. Therefore, the extremely short period cavity growth phenomenon that causes the intense cavitation vibration does not occur. As a result, severe vibration during control can be significantly reduced.

The jet guide surface surrounds the seat surface
Since the jet guide surface covers the seat surface, even if the jet guide surface and the small holes have substantially the same gradient, the sheet from the small hole passes through the jet guide surface. Erosion of the seat surface can be avoided without colliding with the surface. For this reason, the gradient of the jet guide surface can be made relatively small, and as a result, a part of the jet flow from the small hole is not strongly bent downward toward the valve seat by the jet guide surface, and the valve seat The erosion of can be avoided.

The jet flow guide surface surrounds the seat surface
The jet guide surface covers the seat surface, so even if the seat surface and the valve seat have a larger inclination than the small holes and the jet guide surface, the seat surface is stretched outwards. Ejection of the seat surface can be avoided because the jet flow guided by the jet flow guide surface does not collide with the seat surface without coming out. Therefore, the inclination of the seat surface and the valve seat is made large, and as a result, the collision angle of the flow with respect to the valve seat becomes close to parallel, the collision force acting on the valve seat is relaxed, and erosion of the valve seat can be avoided.

[0017]

1 is a sectional view showing a high differential pressure control valve according to an embodiment of the present invention, FIG. 2 is a sectional view of an essential part of FIG. 1, FIG. 3 is an enlarged view of a III portion of FIG. 2, and FIG. FIG. 4A is a schematic diagram showing a fluid flow state of a conventional structure, and FIG. 4B is a schematic diagram showing a fluid flow state of the present invention structure.

The high differential pressure control valve 10 has a casing 14 having an inlet passage 11, an outlet passage 12 and a valve chamber 13. An upper valve body guide 15 and a lower valve body guide 16 are fixedly arranged in the casing 14. Lower valve disc guide 1
6 is a valve seat 17 that connects the inlet channel 11 and the outlet channel 12
It has. Upper valve body guide 15 and lower valve body guide 16
Supports slidably a valve body 19 integral with the valve rod 18. The valve body 19 is provided so as to face the valve seat 17,
The valve seat 17 is moved upward with respect to the base point, and the seat surface 20 provided on the valve body 19 is brought into contact with and separated from the valve seat 17.

The portion of the lower valve body guide 16 that slidably supports the valve body 19 is a cylindrical inner cage 21. Further, a portion of the upper valve body guide 15 which is continuous with a portion below the valve body 19 slidably supported is a cylindrical outer cage coaxially arranged around the inner cage 21 via an annular flow path 22. It is said to be 23.

The outer cage 23 has a large number of small holes 2 for guiding the fluid flowing from the inlet passage 11 into the valve chamber 13 to the annular passage 22.
4 are provided. The small holes 24 are capable of rectifying the flow of the fluid toward the inner cage 21 in a state where the ejection direction of the fluid is horizontal.

The inner cage 21 is also provided with a large number of small holes 25. The small hole 25 is formed on the outer peripheral closing surface 19 of the valve body 19.
It is opened and closed by A and, under the opened state, it is possible to guide the fluid flowing into the annular flow passage 22 to the outlet flow passage 12. The small hole 25 is provided with an inclination angle state in which the streamline of the fluid is jetted at an outflow angle θ with a downward gradient with respect to the valve center axis.

Further, in the lower part of the outer peripheral closed surface 19A of the valve body 19, a fluid having a diameter reduced at the same downward gradient θ as the outflow angle θ of the small hole 25 of the inner cage 21 and flowing out from the small hole 25. And a jet flow guide surface 26 for guiding the jet flow downward.

At this time, the seat surface 20 of the valve body 19 is
Are recessed so as to be covered by the jet guide surface 26 (see FIG. 2). In other words, the jet flow plan of the valve body 19
The inner surface 26 extends from the outer peripheral closing surface 19A of the valve body 19 to the valve body 19
Is formed so as to surround the seat surface 20 of
I have.

The seat surface 20 of the valve body 19 and the valve seat 17 are provided with a slope α larger than the slope θ of the small hole 25 of the inner cage 21 and the jet guide surface 26 of the valve body 19 (FIG. 3). reference).

Further, in the lower portion of the seat surface 20 of the valve body 19, the seat surface 20 has a concave shape on the valve center axis side and is reduced in diameter, and flows out from the small hole 25 in a state of protruding downward. The fluid guided by the jet flow guide surface 26 is supplied to the outlet passage 12
A rectifying surface 27 is formed for smoothly guiding the sheet toward the exit side.

The surface of the valve element 19 is entirely reinforced with a hard metal material such as stellite.

Next, the operation of the above embodiment will be described.

According to the above-described embodiment, the fluid flowing into the casing 14 and rectified by the large number of small holes 24 of the outer cage 23 is not blocked by the outer peripheral blocking surface 19A of the valve body 19, and the inner cage 21 is not blocked. The flow rate and pressure are controlled in the small holes 25 of the small hole 25, and the jet direction from the small hole 25 is bent by the action of the jet guide surface 26 from the horizontal direction to the downward outlet flow path direction, and is further guided to the jet guide surface 26. ,
It flows down without hitting the seat surface 20 covered by the jet guide surface 26. This fluid is further formed into a smooth flow along the concave rectifying surface 27 provided in the lower portion of the seat surface 20 of the valve body 19, and the outlet flow passage 12
Is discharged toward the outlet side of.

That is, according to the above embodiment, the inner cage 21
Even if a water vaporization phenomenon occurs just below the small hole 25 provided in the above, it is diffused by the small hole 25, and is smoothly discharged downward by the small hole 25 having a downward slope and the jet guide surface 26. Therefore, the cavity growth phenomenon with an extremely short period, which is the cause of the intense cavitation vibration, does not occur. As a result, severe vibration during control can be significantly reduced.

Further, according to the above embodiment, the jet flow guide surface 2
6 is formed so as to surround the seat surface 20.
Since the jet guide surface 26 covers the seat surface 20, the inclination θ of the jet guide surface 26 and the inclination θ of the small hole 25 are increased.
Even if they are the same, the jet from the small hole 25 is
The erosion of the seat surface 20 can be avoided without colliding with the seat surface 20 after 6 times. For this reason, the gradient θ of the jet guide surface 26 can be made relatively small, and as a result, a part of the jet flow from the small hole 25 will be part of the jet guide surface 26.
As a result, the valve seat 17 is not strongly bent downward, and erosion of the valve seat 17 can be avoided.

Further, according to the above embodiment, the jet flow guide surface 2
6 is formed so as to surround the seat surface 20.
Since the jet guide surface 26 covers the seat surface 20, the slope α of the seat surface 20 and the valve seat 17 is set to the small hole 2
5 and the inclination θ of the jet flow guide surface 26 is larger than the seat surface 20 does not greatly project outward, and the jet flow guided by the jet flow guide surface 26 may collide with the seat surface 20. Therefore, the erosion of the seat surface 20 can be avoided. Therefore, the inclination α of the seat surface 20 and the valve seat 17
Is increased, and as a result, the collision angle of the flow with respect to the valve seat 17 is made nearly parallel, and the collision force acting on the valve seat 17 is mitigated, and erosion of the valve seat 17 can also be avoided.

As a result, the valve seat 17 and the seat surface 20 are less likely to be damaged, and it is possible to obtain a tight deadline without leakage when the valve is fully closed.

Since the surface of the valve body 19 is reinforced with a hard metal material such as stellite, the jet guide surface 26 and the rectifying surface 27 along which the jet from the small hole 25 flows are not easily eroded. .

[0034]

As described above, according to the present invention, it is possible to reduce the occurrence of severe vibration during control and improve the shutoff performance when the valve is fully closed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a high differential pressure control valve according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of FIG.

FIG. 3 is an enlarged view of section III in FIG.

FIG. 4 (A) is a schematic diagram showing a fluid flow state of a conventional structure, and FIG. 4 (B) is a schematic diagram showing a fluid flow state of the present invention structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Control valve 14 Casing 17 Valve seat 19 Valve body 19A Outer peripheral closing surface 20 Seat surface 21 Inner cage 25 Small hole 26 Jet guide surface

Claims (1)

(57) [Claims] 1. A casing having an inlet passage, an outlet passage, and a valve chamber, a valve seat formed in the valve chamber of the casing, and a casing supported by the casing to contact and separate the valve chamber of the casing from the valve seat. it has a valve body which is movable in the direction, and away allow seat surface provided on the valve body against the valve seat
In addition, a cage is coaxially provided around the valve body, and a small hole is formed in the cage that is opened and closed by the outer peripheral closing surface of the valve body and the fluid flow line forms a downward outflow angle. At the lower part of the outer peripheral closing surface of the valve body, a jet flow guide surface is formed which has a downward slope that is substantially the same as the outflow angle of the small hole and guides a fluid jet flowing out from the small hole downward. In the control valve, the jet guide surface of the valve body is below the outer peripheral closing surface of the valve body.
From the valve body so as to surround the seat surface of the valve body.
The control valve is characterized in that the seat surface and the valve seat are configured to have a slope greater than the slopes of the small holes and the jet flow guide surface.