JPH09178037A - Bellows seal valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain perfect sealing function so that crack or the like is not generated on a bellows even in the use for a long term. SOLUTION: This valve is constituted so that an expansible bellows 40 is stuck fast to a valve stem 23 at the one end and to a valve cover 17 at the other end, for preventing liquid from leaking through the position where the valve stem 23 penetrates through the valve cover 17. In this case, the bellows 40 is fitted so as to become in the natural length in the condition of valve opening. For preventing displacement of the bellows 40 in the lateral direction, a guide slidingly contacting with the inner circumferential face of a valve box extending cylinder 15 is provided on the way of the bellows 40. The bellows 40 is an omega bellows made of inconel alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bellows seal valve which is used in, for example, a nuclear power plant and is required to never leak to the outside.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a bellows seal valve,
(A) is a side sectional view and (B) is a longitudinal sectional view of an essential part. The bellows seal valve shown in FIG. 2 has a fluid passage 11 and a valve seat 13.
A valve box extension cylinder (extension bonnet) 15 is fixed to an upper portion of the valve box 10 in which the valve box 10 is formed, a valve lid 17 is fixed to an upper end of the valve box 10, and a drive unit 30 is provided above the valve lid 17 via a support member 61. The valve rod 23 and the valve body 21 are connected to the output unit 31.
Is provided. As shown in FIG. 2 (A), the valve rod 23
Although a gland packing 19 is filled in a portion of the valve penetrating through the valve lid 17, it is difficult to completely stop the leak even when the valve rod 23 is repeatedly moved up and down. Therefore, as shown in FIG. An expandable bellows 40 is provided in close contact with the valve lid 17 via the upper retainer 45 and in close contact with the valve rod 23 via the lower retainer 46 so that there is no leakage.

FIG. 3 shows a bellows of a conventional bellows seal valve and its vicinity. (A) is a vertical sectional view of the bellows in a natural state, (B) is a vertical sectional view of the valve closed state, and (C) is a valve. It is a longitudinal cross-sectional view of an open state. As shown in FIG. 3, an upper retainer 45 is attached to each of the upper end and the lower end of the bellows 40.
And a lower retainer 46 are airtightly attached. The upper retainer 45 is attached to the valve lid 17, and the lower retainer 46 is attached to the valve rod 2.
It is attached to 3 airtightly. As shown in FIG. 3 (A), the natural state length Lf of the conventional bellows 40 is shown in FIG.
It is manufactured to have a length equal to the closed length Lc shown in FIG. In the valve open state, the bellows 40 is compressed and the bellows 40 is compressed.
The valve open state length Lo shown in (C) is obtained.

2 and 3, the drive unit 30 drives the valve body 21 up and down through the output unit 31 and the valve rod 23 to move the valve body 21 away from or in contact with the valve seat 13. 1
1 is opened and closed. The upper retainer 45 of the bellows 40 is closely fixed to the valve lid 17, and the lower retainer 46 is the valve rod 23.
Even if the valve rod 23 moves up and down, the bellows 40 expands and contracts to tightly fix the space between the upper retainer 45 and the valve lid 17 and between the lower retainer 46 and the valve rod 23. Since the state is completely maintained, fluid leakage can be completely prevented.

[0005]

The conventional bellows seal valve is as described above, and it is required that it is a fluid such as a high temperature and high pressure primary coolant in a nuclear power plant and never leaks to the outside. The bellows 40 is made of a highly durable material so that cracks due to repeated stress and corrosion due to fluid contact do not occur.
So-called stress corrosion cracking may occur when repeated stress and corrosive fluid contact are superimposed and applied during many years of operation and use, and this must be prevented to maintain a perfect sealing function for a long period of time. There was a problem that it did not happen.

The present invention has been made in order to solve the above-mentioned problems, and the bellows 40 can be used even after long-term operation and use.
It is an object of the present invention to obtain a bellows seal valve capable of maintaining a perfect sealing function by preventing cracks and the like from occurring in the bellows.

[0007]

The bellows seal valve according to the present invention is formed and attached so that the bellows has a natural length when the valve is open. Also,
In order to prevent the bellows from being displaced in the lateral direction, a guide is provided in the middle of the bellows so as to slide on and guide the inner peripheral surface of the valve box extension cylinder. The bellows is an omega bellows of Inconel alloy.

Since the bellows of the bellows seal valve according to the present invention is formed and attached so as to have a natural length when the valve is open, when the bellows is in contact with a fluid in a bad environment when the valve is open. In the natural state, there is no stress, and when stress occurs in the valve closed state, it does not come into contact with fluid in a bad environment. Therefore, the conditions of stress corrosion that occur when stress and fluid contact are received at the same time are not the same, and the possibility of cracks and the like is significantly reduced compared to the conventional case. It is generally known that damage caused by stress corrosion is extremely serious, as compared with damage caused by individual causes of stress fatigue or corrosion. If there is a guide in the middle of the bellows that slides on and guides the inner wall surface of the valve box extension cylinder, the bellows can be prevented from being displaced in the lateral direction, and secondary stress can be prevented from occurring. Increase in stress due to the application of dynamic stress is avoided, and fatigue is reduced. Further, if this bellows is an Omega bellows of Inconel alloy, its excellent corrosion resistance and toughness prevent damage or the like even after long-term use.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. First, an outline of a bellows seal valve will be described. FIG. 2 shows an example of a bellows seal valve,
(A) is a side sectional view and (B) is a longitudinal sectional view of an essential part. In the bellows seal valve shown in FIG. 2, a valve box extension cylinder part (extension bonnet) 15 is fixed to the upper part of a valve box 10 in which a fluid passage 11 and a valve seat 13 are formed, and a valve lid 17 is fixed to the upper end thereof. And the drive unit 30 is provided above the support member 61.
Is provided. The left and right openings of the valve box 10 are connected to a pipe (not shown) through which a fluid that should never leak to the outside flows, and the fluid flows through the fluid passage 11. The valve rod 23 connected to the valve body 21 extends upward in the valve box extension cylinder portion 15 and penetrates the valve lid 17 to extend upward and is connected to the output portion 31 of the drive portion 30. FIG.
As shown in (A), a gland packing 19 is inserted and filled in a portion where the valve rod 23 penetrates the valve lid 17 so as to close the gap, and the packing is pressed to prevent the fluid from leaking. .

However, in FIG. 2, when the valve rod 23 repeatedly moves up and down, it is difficult to completely stop the leak with the gland packing 19. Therefore, in order to completely prevent the leak, the inside of the valve box extension cylinder portion 15 is prevented. An expandable bellows 40 is provided in the cylindrical space as shown in FIG.
5 through the valve lid 17 and fixed to the lower retainer 46
It is provided in close contact with and fixed to the valve rod 23 via. This bellows 40 is made of Inconel alloy (for example, Inconel 600: Ni 76%, Cr 16%, Fe 8%, other S
i, Mn, C, etc.) are omega bellows. Also, one or more guides 4 may be provided in the middle of the bellows 40.
2 are provided. The inner peripheral surface of the valve box extension cylinder portion 15 is smoothly finished, and the outer peripheral surface of the guide 42 is formed so as to be in sliding contact with the smooth inner peripheral surface of the valve box extension cylinder portion 15. In addition, 41 is a seal ring provided in large numbers on the outer periphery.

FIG. 1 shows a bellows and its vicinity, which is one embodiment of a bellows seal valve according to the present invention,
(A) is a vertical sectional view of a bellows in a natural state, (B) is a vertical sectional view of a valve closed state, and (C) is a vertical sectional view of a valve opened state. As shown in FIG. 1 (A), an upper retainer 45 and a lower retainer 46 are firmly attached to the upper and lower ends of the bellows 40 by continuous welding over the entire circumference so that there is absolutely no leakage. This bellows 40
As shown in FIGS. 1B and 1C, the valve box extension cylinder portion 15
Inside, the upper retainer 45 is provided in close contact with the valve lid 17, and the lower retainer 46 is provided in close contact with the valve rod 23 so as to never leak. As shown in FIG. 1A, the natural length Lf of the bellows 40 according to the present invention.
(The length in the free state without applying any force) is made equal to the valve open state length Lo shown in FIG. 1 (C).

Next, the operation and action of the bellows seal valve shown in FIGS. 1 and 2 will be described. In FIG. 2, the valve body 2 is driven by the drive unit 30 via the output unit 31 and the valve rod 23.
When the valve 1 is driven up and down and the valve body 21 is separated from and brought into contact with the valve seat 13, the fluid passage 11 is communicated and closed, the fluid passing through this valve is circulated, and the flow is blocked. In FIG.
The upper retainer 45 of the bellows 40 is fixedly attached in close contact with the valve lid 17, and the lower retainer 46 is attached to the valve rod 23.
Since it is fixedly attached in close contact with the valve stem 2,
Even if 3 moves up and down, the bellows 40 expands and contracts to maintain a tightly fixed state between the upper retainer 45 and the valve lid 17 and between the lower retainer 46 and the valve rod 23.
Fluid outside the bellows 40 cannot enter the inside of the bellows 40 at all, and it is absolutely impossible to reach the gap between the valve stem 23 and the valve lid 17, thus preventing fluid leakage. Can be completely stopped.

The bellows 40 of the bellows seal valve has a fatigue due to repeated stress caused by the repeated deformation applied to the bellows 40 due to repeated use for many years, for example, 10 MPa.
The bellows 40 is excellent because there is a risk that the bellows 40 may crack due to long-term use due to corrosion that may occur due to contact with a fluid containing boric acid and the like at a high pressure exceeding 300 ° C. and a high temperature exceeding 300 ° C. It was made of corrosion-resistant alloy to improve durability. However, as shown in FIG. 3A, the bellows 40 of the conventional bellows seal valve is manufactured so that the length Lf in the natural state is equal to the length Lc in the closed state. In the valve open state shown in (), the bellows 40 is exposed to the corrosive fluid at the same time when the bellows 40 is compressed and stress is generated, so that the condition of stress corrosion is satisfied and damage such as stress corrosion cracking occurs. It was likely to occur.

With respect to such a problem, the bellows 40 of the bellows seal valve according to the present invention shown in FIG. 1 cannot be said to be free from fatigue and corrosion due to long-term operation and use, but it is shown in FIG. The bellows 40 is shown in FIG.
Unlike the bellows 40 shown in FIG. 1A, as shown in FIG. 1A, the length Lf in the natural state is made equal to the length Lo in the valve open state. That is, since the bellows 40 is formed and attached so as to have a natural length in the valve open state, when the bellows 40 is in contact with a fluid in a bad environment in the valve open state as shown in FIG. 1C. Bellows 4
0 is a natural state in which there is no stress, and as shown in FIG. 1 (B), when expansion stress is generated in the bellows 40 with the valve closed, the bellows 40 does not come into contact with the fluid in a bad environment. In this way, the conditions of stress corrosion that occur when stress and fluid contact in a bad environment are received at the same time do not occur, so the phenomenon of stress corrosion cracking does not occur, and the occurrence of damage is significantly reduced compared to the past. . Generally, even if fatigue does not occur due to repeated stress fatigue, and corrosion does not occur only by contact with a fluid in a bad environment, fatigue under repeated stress and fluid contact in a bad environment are simultaneously received. A so-called stress corrosion cracking phenomenon is known, in which a remarkable corrosive crack may sometimes occur. The bellows 40 of the bellows seal valve according to the present invention excludes the condition that the stress corrosion cracking phenomenon occurs from being satisfied, whereby the durability of the bellows seal valve can be dramatically improved.

Further, as shown in FIG. 2 (B), if there is a guide 42 in the middle of the bellows 40 for slidingly guiding the inner wall surface of the valve box extension cylinder portion 15, the bellows 40 is displaced in the lateral direction. It is prevented that the secondary stress is generated in the bellows 40, the increase of the stress due to the load of the secondary stress is avoided, the fatigue due to the long-term use is reduced, and the damage such as the crack is generated. Contribute to the prevention of.

Further, if the bellows 40 is an omega bellows of an Inconel alloy, its excellent corrosion resistance and toughness will surely exert a sealing function for a long period of time without causing damage even after long-term use. .

[0017]

As described above, according to the present invention, since the length of the bellows in the natural state is equal to the length of the valve open state, the bellows simultaneously causes corrosive fluid contact and stress. It will not be received, so-called stress corrosion cracking phenomenon will be prevented from occurring and it will withstand long-term use and maintain its sealing function. Further, the provision of the guide prevents irregular deformation of the bellows. Further, if the bellows is made of an Inconel alloy omega bellows, the durability is further improved due to excellent corrosion resistance and toughness.

[Brief description of the drawings]

FIG. 1 shows a bellows which is one embodiment of a bellows seal valve according to the present invention and its vicinity, (A) is a vertical cross-sectional view of the bellows in a natural state, (B) is a vertical cross-sectional view in a valve closed state, (C) is a vertical cross-sectional view of the valve open state.

2A and 2B show an example of a bellows seal valve, FIG. 2A is a side sectional view, and FIG.

FIG. 3 shows a bellows of a conventional bellows seal valve and its vicinity, (A) is a vertical sectional view of the bellows in a natural state, (B) is a vertical sectional view of a valve closed state, and (C) is a valve opened state. FIG.

[Explanation of symbols]

10: valve box, 11: fluid passage, 13: valve seat, 15:
Valve box extension cylinder part, 17: Valve lid, 19: Gland packing, 21: Valve body, 23: Valve rod, 40: Bellows, 4
2: Guide, 45: Upper retainer, 46: Lower retainer, Lf: Length in natural state, Lc: Length in closed state, Lo:
Open length.

Claims (3)

[Claims] Claim: What is claimed is: 1. A bellows, which is expandable and contractible so as to prevent fluid leakage at a portion where a valve rod for driving the valve body to move up and down penetrates a valve lid at an upper end of a valve box extension cylinder, has one end closely attached to the valve rod. A bellows seal valve having the other end in close contact with the valve lid, wherein the bellows is formed and attached so as to have a natural length when the valve is open. 2. The guide according to claim 1, further comprising a guide for slidingly guiding the inner peripheral surface of the valve box extension cylinder part in the middle of the bellows so as to prevent the expanding and contracting bellows from being displaced laterally. Bellows seal valve. 3. The bellows seal valve according to claim 1, wherein the bellows is an Omega bellows of Inconel alloy.