JP2002276830A - Seal structure of ball valve and ball valve provided with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a sealing property in a ball valve by enhancing sealing properties of a first sealing means and a second sealing means. SOLUTION: This seal structure is provided with a seat retainer 20 displaceable in an axial direction of a flow passage 13 while retaining a ball seat 17; a spring retainer 22 disposed at an opposite side to the ball seat 17 of the seat retainer 20 and displaceable in an axial direction of the flow passage; a first sealing means 24 for sealing a space between the seat retainer 20, the spring retainer 22 and a housing 12; a second sealing means 25 radially inwardly disposed as compared with the first sealing means 24 and sealing a space between the seat retainer 20 and the spring retainer 22; a back pressure space 18 surrounded by the seat retainer 20 and the spring retainer 22 and sealed against the flow passage 13 by the first sealing means 24 and the second sealing means 25; and a communication bore 23 formed on the seat retainer 20 and communicating a body cavity 16 with the back pressure space 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball valve sealing structure and a ball valve provided with the same.
In particular, the present invention relates to a technique that is effective when applied to improve sealing performance when a ball valve is used at a low or high temperature.

[0002]

2. Description of the Related Art In recent years, development of clean energy such as LNG has become active worldwide, and various valves have been used to control those plant pipings. When automatically controlling the valve, a 90-degree open / close ball valve is suitable in terms of operability and cost.

Here, a conventional ball valve sealing structure will be described.

FIG. 5 is a sectional view of an essential part showing an example of a seal structure in a conventional ball valve, and FIG. 6 is a sectional view of an essential part showing another example of a seal structure in a conventional ball valve.

In the ball valve shown in FIG. 5, a ball 114 having a through hole (not shown) is rotatably disposed on a flow path 113 formed in a housing 112, and the ball 114 is rotated. The channel 113 is opened and closed by communicating or blocking the through hole and the channel 113, and an annular ball sheet 117 is provided in contact with the outer peripheral surface of the ball 114. And ball seat 11
7 is urged toward the ball 114 by the spring 121 and the annular
Are disposed so as to be displaceable in the axial direction.

An annular groove 1 is formed on the outer periphery of the seat retainer 120.
20a is formed, and an O-ring 128 for sealing between the seat retainer 120 and the housing 112 is mounted in the annular groove 120a. The O-ring 128 prevents fluid from entering the body cavity 116.

Here, the O-ring 128 is generally made of rubber having elasticity, and is disposed at a place to be sealed in a state where a predetermined crushing margin is given, so that an additional pressing force is not applied. It is a self-sealing sealing member that exhibits sealing properties.

The O-ring 128 can be sealed from a low pressure to a high pressure, but the usable temperature range is -55 to 3
It is about 00 ° C. Therefore, instead of the O-ring 128, a seal member 123 (FIG. 6) made of expanded graphite is used for a ball valve used in a low-temperature range or a high-temperature range outside this temperature range.

The sealing member 123 made of expanded graphite is a non-self-sealing sealing member that does not exhibit a predetermined sealing performance unless a pressing force is continuously applied.

That is, in FIG. 6, a spring 121 is provided on the opposite side of the seat retainer 120 from the ball 114.
A spring retainer 122 urged toward the seat retainer 120 by the spring is disposed. The seal member 123 made of expanded graphite, which is pressed against the seat retainer 120 by the spring retainer 122 and seals between the housing 112 and the seat retainer 120, is mounted.

[0011]

However, in the case of a sealing member made of expanded graphite, if the pressing force of the spring is weak, the leak becomes more severe as the pressure of the fluid becomes higher (for example, 5 MPa or more).

As a countermeasure, it is conceivable to increase the pressing force by increasing the spring. However, since the spring is a component that must be arranged in a limited space inside the ball valve, there is a limit to improving the pressing force due to the increase in the size of the spring. When the pressing force of the spring is increased, the pressing force of the ball seat against the ball is increased, and the operating torque is increased. Then, a stem for rotating the ball must be strengthened, or a large actuator capable of obtaining a large output torque is required for an actuator used in automation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ball valve seal structure capable of improving the sealing property within the range of a normal valve space and a ball valve provided with the same.

[0014]

In order to solve the above-mentioned problems, a ball valve sealing structure according to the present invention is formed on a ball by rotating a ball disposed on a flow path formed in a housing. A seal structure provided in a ball valve that opens and closes a flow path through a formed through hole, and is provided so as to hold an annular ball sheet in contact with the outer peripheral surface of the ball and to be displaceable in the axial direction of the flow path. An annular holding member, an annular pressing member arranged on the opposite side of the holding member to the ball seat and displaceable in the axial direction of the flow path, and sealing between the holding member, the pressing member, and the housing. An annular first sealing means, an annular second sealing means disposed radially inward of the first sealing means and sealing between the holding member and the pressing member, and a holding member and the pressing member. Surrounded And a back pressure space sealed with respect to the flow path by the first seal means and the second seal means, and formed in the holding member. It has a communication hole for communicating the body cavity with the back pressure space.

According to the invention, since the body cavity and the back pressure space communicate with each other through the communication hole, the first sealing means and the second sealing means are reliably compressed by the pressing means. As a result, the self-sealing property is improved, and the sealing property of the ball valve can be improved.

[0016]

Embodiments of the present invention will be described below more specifically with reference to the drawings. Here, the same reference numerals are given to the same members in the attached drawings,
In addition, duplicate description is omitted. The embodiments of the present invention are particularly useful forms in which the present invention is implemented, and the present invention is not limited to the embodiments.

FIG. 1 is a sectional view showing a ball valve provided with a seal structure according to an embodiment of the present invention. FIG. 2 is a sectional view showing a primary part of the ball valve shown in FIG.
FIG. 3 is a cross-sectional view showing a main part on the secondary side in the ball valve of FIG. 1, and FIG. 4 is a cross-sectional view showing a main part of a ball valve provided with a seal structure according to another embodiment of the present invention. .

In the ball valve of the present embodiment shown in FIGS. 1 and 2, the housing 12 comprises a body 12a and a body cap 12b, and has a side entry type in which a cylindrical flow path 13 is formed. It has a structure. However, another structure such as a top entry type may be used.

Inside the housing 12, a ball 14 having a cylindrical through hole 14a communicating with the flow path 13 is arranged on the flow path 13. This ball 14 is in the flow path 1
A pair of stems 15a, 15 arranged in a direction perpendicular to
5b is supported by a stem 15a, which is mounted rotatably in a direction to open and close the flow path 13 by the through-holes 14a and 15b as the rotation fulcrum. Here, the ball 14 is made of metal or resin, in the case of a metal, for example stainless steel, carbon steel, ductile, iron, bronze, brass,
When stellite or the like is made of a resin, for example, a fluorine resin or a nylon resin is used.

Incidentally, around the stems 15a and 15b,
A body cavity 16, which is a space defined by the flow path 13 and surrounded by the housing 12 and the balls 14, is formed.

As shown in detail in FIGS. 2 and 3, the space between the flow path 13 and the body cavity 16 is sealed,
In order to prevent the fluid from leaking from the channel 13 to the body cavity 16, an annular ball sheet 17 is provided on the inflow side and the outflow side of the ball 14 in contact with the outer peripheral surface of the ball 14. I have. Therefore, the ball 14 rotates while sliding on the ball seat 17.
The ball seat 17 is made of a resin such as a fluororesin.
Alternatively, it is formed of a rubber material such as synthetic rubber, but may be formed of metal.

The ball seat 17 is held by an annular seat retainer (holding member) 20. The seat retainer 20 is provided so as to be displaceable in the axial direction of the flow path 13. A spring (elastic member) 21 is held on the opposite side of the seat retainer 20 from the ball seat 17, and the seat retainer 20 is held by the spring 21. The spring retainer (pressing member) 22 urged to the side
Are provided so as to be displaceable in the axial direction. Spring 21
Uses a coil spring, but a leaf spring, a disc spring, or the like may be used. In the present embodiment, the spring retainer 22 holding the spring 21 is a pressing member. However, a member provided so as to be displaceable in the axial direction of the flow path 13 without holding the spring 21 is used. It may be a pressing member.

An annular first seal means 24 which is pressed by the seat retainer 20 by the spring retainer 22 to seal between the seat retainer 20, the spring retainer 22 and the housing 12, and has a smaller diameter than this seal portion. An annular second sealing means 25 for sealing between the seat retainer 20 and the spring retainer 22
Is installed. In the present embodiment, the first
The two sealing means 24 and the second sealing means 25 are provided, but may be one or three or more. Further, the numbers of the first sealing means 24 and the second sealing means 25 may be different from each other.

As shown, the first seal means 24 and the second seal means 25 are located coaxially with each other, and the second seal means 25 is more radially oriented than the first seal means 24. It is located inside.

However, it is sufficient that the second sealing means 25 is disposed radially inward of the first sealing means 24.
Not necessarily the first sealing means 24 and the second sealing means 25
Need not be coaxial with each other. Further, the first sealing means 24 and the second sealing means 25 do not have to be located at the same position in the radial direction, and may be displaced from each other. further,
The second sealing means 25 seals between the seat retainer 20 and the spring retainer 22 by an annular projection 20 a formed on the seat retainer 20.
0a may be formed separately to seal between the seat retainer 20 and the spring retainer 22.

Here, the first sealing means 24 and the second sealing means 25 are crushed and deformed when a pressing force is applied to exhibit a sealing property, that is, a non-self-sealing sealing member. I have. Examples of the material of such a non-self-sealing sealing member include expanded graphite, carbon fiber, fluororesin fiber, aramid fiber, and asbestos. However, a non-self-sealing sealing member may be formed of a material other than those listed here. Note that the first sealing means 24 and the second sealing means 25 may use a sealing member that is crushed without applying a pressing force to exhibit sealing properties, that is, a sealing member having self-sealing properties. Examples of the self-sealing sealing member include rubber and various resins.

The first seal means 24 and the second seal means 25 seal the passage 13 with the seat retainer 20 and the spring retainer 2.
2, a back pressure space 18 is formed. The seat retainer 20 includes the body cavity 1.
A communication hole 23 that connects the back pressure space 6 with the back pressure space 18 is formed. Therefore, the pressure in the back pressure space 18 is the same as the pressure in the body cavity 16.

Next, the operation of the ball valve having such a structure will be described. For convenience of description, the primary side, which is the fluid inflow side, is the left side in FIG. 1 and FIG. 2, and the secondary side, which is the fluid outflow side, is the right side view in FIG. 1 and FIG.

However, in the ball valve, the above-described seal structure of the ball valve may be provided on both the primary side and the secondary side as described above, but it is provided only on the primary side and the secondary side has a different structure. Alternatively, it may be provided only on the secondary side, and the primary side may have a different structure. That is, the seal structure may be provided on at least one of the primary side and the secondary side.

[0030] the through hole 14a and the flow passage 13 of the ball 14 is subjected to fluid pressure in the valve closed position do not communicate, the primary side, in FIG. 2, the diameter D ₁ and the diameter D ₂
A ring-shaped region surrounded by ^{_{S 1 (= (D 1 2}} -
D _{² 2)} π / 4) receiving fluid pressure _{P 1} on. Therefore, the force acting on the area _{S 1} by the fluid pressure _{P 1 F 1}
Then, F ₁ = P ₁ × S ₁ , and this force F ₁ presses the first sealing means 24 and the second sealing means 25.

On the other hand, as described above, the spring retainer 2
The back pressure space 18 surrounded by the seat retainer 20 and the seat pressure retainer 20 has the same pressure as the body cavity 16 due to the communication hole 23. The cavity pressure in the body cavity 16 is stably maintained at a low pressure by the volume of the cavity and a relief operation (pressure release operation) on the secondary side described later.

Therefore, in the back pressure space 18, the diameter D₃ 
And diameter D₄ Ring-shaped area S surrounded by₂ (= (D
₃ ²-D₄ ²) Π / 4) to cavity pressure P₂ Receiving
You. Therefore, the cavity pressure P₂ By the area S₂ Made in
Use force F₂ Then F ₂ = P₂ × S₂ Tona
This force F₂ Force the spring retainer 22 to F₁ To
Acts as a force to push back against.

Here, since the back pressure space 18 communicates with the body cavity 16, it is ensured that P ₁ > P ₂
Becomes

Therefore, if the spring force, which is the force by which the spring 21 presses the spring retainer 22 in the direction of the ball 14, is F ₃ , the spring retainer 22 receives the force of F ₁ + F ₃ -F ₂ and receives the ball 14.
, And the first sealing means 24 and the second sealing means 25 are compressed by the force of F ₁ + F ₃ -F ₂ to enhance the self-sealing property. Thereby, the primary side and the body cavity 16 are connected to the first sealing means 2.
The sealing is surely performed by the fourth and second sealing means 25 and the ball seat 17.

In this case, the ball seat 17
Is F ₁ + F ₃ − acting on the spring retainer 22.
Regardless of the force ^{_{F 2, f = (D 1}} 2 -D 5 2) π /
The ball 14 is pressed by a force of 4 × (P ₁ −P ₂ ) + F ₃ . Therefore, the force acting on the spring retainer 22 increases the pressing force of the ball seat 17 on the ball 14, that is, the rotational torque of the ball 14, and the stem 15
This does not increase the operating force of the a and 15b.

Next, on the secondary side, in FIG. 3, the back pressure space 18 has the same pressure as the body cavity 16 due to the communication hole 23, so that the back pressure space 18 has a diameter D _3.
And a ring-shaped region _S 2 surrounded by the diameter _{D 4} (=
Receiving the cavity pressure _{P 2} in ^{_{(D 3 2 -D 4 2)}} π / 4). Therefore, the area _{S 2} by the cavity pressure _{P 2}
The force acting when the _{F 2, F 2 = P 2} × S 2 , and this force _{F 2} acts as a force to push back the spring retainer 22 in. On the other hand, the spring retainer 22 is biased toward the ball 14 side by a spring force F _3.

Therefore, the cavity pressure is reduced.
F if not₃ > F₂ Spring to be
Power F₃ Is set, the spring retainer 22
Is F ₃ -F₂ Moves in the direction of the ball 14 under the force of
Will be. Thereby, the first sealing means 24 and
And the second sealing means 25 is F₃ -F₂ Compressed by the force of
You. Here, the cavity pressure P₂ Force F₂ But sp
Ring force F₃ , That is, F₃ <F₂
 , The spring retainer 22 becomes F ₂ −
F₃ Moves in the opposite direction to the ball 14
You. Then, the first seat by the spring retainer 22 is
The compression of the sealing means 24 and the second sealing means 25 is released.
Loss of sealing performance and cavity pressure P₂ Is a spring
Between the retainer 22 and the seat retainer 20 on the secondary side.
Relieved by the flow path 13.

[0038] By such relief operation will be kept below a certain level the pressure of the cavity pressure P ₂ in. Therefore, the spring force F ₃ and the diameter D ₃
And the size of the diameter D ₄ By a predetermined set, the cavity pressure P ₂ can be held sufficiently lower than the primary side. In the present embodiment, when the peak fluid pressure is 100 kgf / cm ² , when the cavity pressure P ₂ becomes 15 kgf / cm ² or more, the spring force is relieved to the secondary flow path. F ₃ is set.

According to the above description, the sealing mechanism compresses the first sealing means 24 and the second sealing means 25 using the fluid pressure on the primary side, and
It functions to ensure the sealing property between the cavity 3 and the cavity 12. On the secondary side, it functions to release the cavity pressure.

A technique for obtaining a pressing force by using two sealing members having different diameters from each other, such as the first sealing means 24 and the second sealing means 25, is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 7-1.
No. 90212, JP-A-7-180777, and Utility Model Registration No. 3050961. In this technique, a seal member is attached to each of an annular outer circumferential groove and an inner circumferential groove.

However, since the non-self-sealing seal member is a non-expandable ring that does not expand and contract like a self-sealing seal member such as an O-ring, the seal member cannot be mounted in the annular groove. Further, even if it can be mounted, a predetermined sealing property cannot be obtained because no pressing force is applied.

Therefore, even if a non-self-sealing sealing member is applied to the technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-190212, it is not possible to obtain the function and effect as described in the present application. Class 6 ball valve with this seal structure
00, size 4B as a sample, measurement of sheet leakage,
Performed for cavity leakage and passage leakage. The measurement conditions were as follows: temperature at room temperature (about 10 ° C.) and low temperature (−100
° C) and the maximum pressure was 10 MPa.

Here, the cavity leakage measurement is to measure the leakage from the drain plug 16a of the body cavity 16 by applying pressure from the body 12a side or the body cap 12b side. The measurement time here was 1 minute at each pressure.

In addition, the measurement of the passage leakage refers to the measurement of the body 12a.
Pressure is applied from the side to measure leakage on the body cap 12b side, and conversely, pressure is applied from the body cap 12b side to measure leakage on the body 12a side. In this passage leak measurement, one measurement was divided into 2 to 4 pressure levels, and continuous measurement was performed for 5 minutes at each pressure for a total of 10 to 20 minutes.

Table 1 shows the measurement results of cavity leakage due to body pressurization, and Table 2 shows the measurement results of cavity leakage due to cap pressurization.

[0046]

[Table 1]

[0047]

[Table 2]

As can be seen from Tables 1 and 2, no cavity leakage occurred at any test pressure and at both room temperature and low temperature.

Next, Table 3 shows the measurement result of the passage leakage due to the body pressurization, and Table 4 shows the measurement result of the passage leakage due to the cap pressurization.

[0050]

[Table 3]

[0051]

[Table 4]

As can be seen from Tables 3 and 4, no passage leakage occurred at any test pressure and at both room temperature and low temperature.

From these test results, it has been clarified that by applying the present sealing structure to a ball valve, extremely excellent sealing properties can be obtained.

As shown in FIG. 4, the communication hole 23 can be provided with a valve member 26 for flowing fluid only in one direction. The valve member 26 has a distal end directed toward the back pressure space 18 and is displaceable in the direction of fluid flow. When the fluid flows from the back pressure space 18 to the body cavity 16, the flow path is opened to move the fluid. And when the fluid flows from the body cavity 16 to the back pressure space 18, the flow path is closed to prevent the movement of the fluid.

In this way, when the cavity pressure is relieved, the cavity pressure is reduced to the secondary back pressure space 18.
Therefore, the seat retainer 20 and the spring retainer 22 move in the opposite direction to the ball 14 integrally. Then, the cavity pressure can be relieved from between the ball 14 and the ball seat 17 to the flow path 13.

Although the valve member 26 in this embodiment has a conical shape, the present invention is not limited to this. That is, the valve member only needs to be able to flow fluid from the back pressure space 18 to the body cavity 16 only. For example, various valve members such as a flexible tongue-shaped member may be used. Can be adopted.

[0057]

As apparent from the above description, the following effects can be obtained according to the present invention.

(1) Since the first sealing means and the second sealing means are reliably compressed by the pressing means and the self-sealing property is improved, the sealing property of the ball valve can be improved.

(2) That is, on the fluid inflow side,
The first sealing means and the second sealing means are compressed by the fluid pressure, and it is possible to ensure the sealing performance between the flow path and the cavity.

(3) On the outflow side of the fluid, when the cavity pressure becomes higher than a predetermined value, the cavity pressure is relieved and the cavity pressure can be released.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a ball valve provided with a seal structure according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a primary part of the ball valve of FIG. 1 on a primary side;

FIG. 3 is a sectional view showing a main part on the secondary side in the ball valve of FIG. 1;

FIG. 4 is a cross-sectional view illustrating a main part of a ball valve provided with a seal structure according to another embodiment of the present invention.

FIG. 5 is a sectional view of a main part showing an example of a seal structure in a conventional ball valve.

FIG. 6 is a sectional view of a main part showing another example of a seal structure in a conventional ball valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Housing 12a Body 12b Body cap 13 Flow path 14 Ball 14a Through hole 15a, 15b Stem 16 Body cavity 17 Ball seat 18 Back pressure space 18a Pressing part 20 Sea retainer (holding member) 20a Annular projection 21 Spring (elastic member) 22 Spring retainer (pressing member) 23 Communication hole 24 First seal means 25 Second seal means 26 Valve member 112 Housing 113 Flow path 114 Ball 116 Body cavity 117 Ball seat 120 Sea retainer 120a Annular groove 121 Spring 122 Spring retainer 123 Sealing member 128 O-ring

Claims (7)

[Claims] 1. A seal structure provided in a ball valve that opens and closes a flow path through a through hole formed in a ball by rotating a ball disposed on a flow path formed in a housing. An annular holding member that holds an annular ball sheet in contact with the outer peripheral surface of the ball and is displaceable in the axial direction of the flow path; and is disposed on the opposite side of the holding member from the ball sheet. ,
An annular pressing member provided so as to be displaceable in the axial direction of the flow path; an annular first sealing means for sealing between the holding member, the pressing member, and the housing; and the first sealing means. A second sealing means disposed radially inward of the holding member and sealing between the holding member and the pressing member. 2. A seal structure provided in a ball valve that opens and closes a flow path through a through hole formed in the ball by rotating a ball disposed on a flow path formed in a housing. An annular holding member that holds an annular ball sheet in contact with the outer peripheral surface of the ball and is displaceable in the axial direction of the flow path; and is disposed on the opposite side of the holding member from the ball sheet. ,
An annular pressing member provided so as to be displaceable in the axial direction of the flow path; an annular first sealing means for sealing between the holding member, the pressing member, and the housing; and the first sealing means. An annular second sealing means disposed radially inward of the holding member and sealing between the holding member and the pressing member; and the first sealing means surrounded by the holding member and the pressing member, and A back pressure space sealed with respect to the flow path by the second sealing means; and a body cavity formed in the holding member, surrounded by the housing and the ball, and formed separately from the flow path. A seal structure for a ball valve, comprising: a communication hole that communicates a tee with the back pressure space. 3. The ball valve sealing structure according to claim 1, wherein the first sealing means and the second sealing means have a non-self-sealing property. 4. The ball valve according to claim 1, wherein the pressing member holds an elastic member for urging the pressing member toward the holding member. Seal structure. 5. The communication hole is provided with a valve member that allows movement of the fluid from the back pressure space to the body cavity and prevents movement of the fluid from the body cavity to the back pressure space. The seal structure of a ball valve according to any one of claims 2 to 4, wherein the seal structure is provided. 6. A ball, wherein the ball valve sealing structure according to claim 1 is provided on at least one of a fluid inflow side and a fluid outflow side. valve. 7. The ball valve sealing structure according to claim 4, which is provided on the fluid outflow side, wherein when the cavity pressure becomes a predetermined pressure or more, the pressing member opposes the urging force of the elastic member. The ball valve according to claim 6, wherein the biasing force of the elastic member is set so as to move in a direction opposite to the direction of the ball.