JP2003120831A - Ball valve and fluid leakage preventing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact ball valve of a simple constitution and a fluid leakage preventing method capable of providing the safety work in additionally laying the piping on the pipeline and installed piping. SOLUTION: A valve seat is sealed by pressing a seat 19 to ball faces of the ball valves 2, 3 by continuously charging an inert gas having pressure higher than piping pressure at least at the ball downstream side, into a cavity part 14 in a valve close condition, and the leakage of the fluid to the downstream side of the ball valves 2, 3 are prevented by continuously discharging the inert gas from the cavity part 14 to the external.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the addition of pipelines and equipment pipes, and the remodeling.
The present invention relates to a ball valve that enables safe and safe work and a method for preventing leakage of fluid such as gas using the ball valve.

[0002]

2. Description of the Related Art When flammable gas such as natural gas is contained in a pipeline or the like, even if the gas in the pipeline on the construction side is released, a ball valve that shuts off the pipeline causes seat leakage. If so, the work of cutting or welding the pipes for expansion / modification would be extremely dangerous, and it was impossible in reality.

Therefore, in the case of carrying out this kind of construction, conventionally, a method of making the seat seal structure of the ball valve a double seal system to prevent gas from leaking from the downstream side is used, or as shown in FIG. As described above, when the expansion is planned in the future, the pipeline 31 on the downstream side from the ball valve 30 has the water sealing structure 32, and the water sealing structure 3
A construction was also adopted in which a liquid level confirmation pipe 33 was provided in the vicinity of 2, and a tip portion of the cutting position 34 was sealed with a cap 34a to prevent gas leakage.

In addition, according to Japanese Unexamined Patent Publication No. 2001-65715, the pressure of the internal fluid flowing in the pipe system from the seal fluid supply port into the valve body (cavity part) is higher than the pressure of the internal fluid when the ball valve is closed. A ball valve has been proposed in which a high-pressure sealing fluid is press-fitted to prevent leakage as much as possible.

[0005]

However, when the expansion is planned in the future, it is good to adopt the above watertight structure method, but this watertight structure 32 can be used for normal expansion or modification work. There was a problem in that it was a large-scale construction and required equipment costs, etc. to use.

According to the method disclosed in the above publication,
Even when the valve is closed, the upstream side channel, the downstream side channel, and the cavity portion are in communication with each other, so that the fluid that has entered through the supply port flows out to the upstream side channel and the downstream side channel.
Therefore, when stopping the fluid on the upstream side, it is necessary to make the input pressure from the supply port significantly higher than the fluid pressure on the upstream side, and there are many dangers in the construction of adding or modifying the pipeline. It is impossible to adopt.

The present invention was developed in order to solve the above-mentioned problems, and its purpose is to simplify the addition and modification of pipelines on the pipeline and facility piping. Another object of the present invention is to provide a ball valve and a fluid leakage prevention method which can be made compact with a simple structure and can be operated safely.

[0008]

In order to achieve the above object, the invention according to claim 1 rotatably provides a ball having a through hole supported by a stem in a body, and is mounted on both sides of the ball. A cavity is provided between the outer peripheral surface of the ball and the inner peripheral surface of the body by the seal mechanism described above, and at the time of valve closing, a valve for feeding an inert gas having a pressure higher than the piping pressure at least on the ball downstream side into the cavity is provided. A ball valve having a body provided with valves for discharging the inert gas from the cavity to the outside.

In this case, at least one of the valves for feeding and releasing the inert gas into the cavity is a drain valve for communicating the outside with the cavity, and the flow rate of the drain valve can be adjusted. It is preferable to provide it.

Further, the sealing mechanism is configured such that the seat is pressed against and brought into contact with the outer peripheral surface of the ball by a double-sealing system using self-forced force generated by the biasing force of the spring and the pressure in the cavity.

According to a fourth aspect of the present invention, in the valve closed state, an inert gas having a pressure higher than the piping pressure at least on the downstream side of the ball is continuously fed into the cavity portion, whereby the seat is placed on the ball surface of the ball valve. This is a fluid leakage prevention method in which the fluid is prevented from flowing out to the downstream side of the ball valve by continuously pressing the valve seat to seal the valve seat and further discharging the inert gas from the cavity to the outside. Even if valve seat leakage occurs, the piping fluid is discharged to the outside together with the inert gas, and is a fluid leakage prevention method that prevents leakage to the downstream side.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a ball valve and a fluid leakage prevention method according to the present invention will be described with reference to the drawings. Figure 1
[Fig. 2] is an explanatory view showing a state where a ball valve is installed in a pipeline, and Fig. 2 is an enlarged vertical sectional view of the ball valve.

In FIG. 1, 1 is a pipeline,
Ball valves 2 and 3 are installed in the middle of the pipeline 1. The left side of the pipeline 1 is the upstream side, the right side is the downstream side, and a cap stopper 4 is provided at the right end of the pipeline 1.

In FIG. 2, the structure of the ball valve 2 or the ball valve 3 is provided with connecting portions 6 and 7 for connecting both ends of the body 5 to the pipeline 1 by means such as welding. A gas inflow port 8 and a gas outflow port 9 are provided in each. Further, a ball 11 having a through hole 10 is rotatably provided inside the body 5 via upper and lower stems 12 and 13, and the upper stem 12 is driven to open and close by manual operation or automatic operation by an actuator. There is.

A space surrounded by the body 5 and the outer peripheral surface of the ball 11 is formed as a cavity portion 14,
A pair of sealing mechanisms 15 and 16 are mounted between the inner peripheral surface of the body 5 and the outer peripheral surface of the ball 11, and
Is configured to maintain a predetermined sealing property by the sealing mechanisms 15 and 16.

FIG. 3 is an enlarged detailed view of the portion a of FIG. 2 and is an enlarged vertical sectional view showing the sealing mechanisms 15 and 16. In FIG. 3, the ring 1 is attached to the tip of the annular seat retainer 17.
A ring-shaped seat 19 is mounted via an outer ring 18 fixed to the seat retainer 17 by 7a, and the outer ring 18 is biased toward the ball 11 side via a spring 20. In the figure, 21 is an O-ring,
22 is a sealant supply device.

As shown in FIG. 3, the sealing mechanisms 15 and 16 are installed between the seat retainer 17 and the body 5 with respect to the seal point diameter D ₁ between the seat 19 and the ball 11, and are attached to the seat retainer 17. Self-force, that is,
The pressure of the cavity 14 causes the seat 19 to move to the ball 11
The outer diameter side diameter of the O-ring 21 that generates a force to be pressed to the side is D ₂ , and the inner diameter side diameter is D ₃ . Also, the pipeline diameter pressure is P ₁ and P ₃ , and the cavity portion 14 pressure is P
_If P ₂ > P ₁ or P ₃ , the force W with which the seat 19 is pressed against the ball 11 side is W = π / 4 (D ₁ ²
-D ₃ ²⁾ become (P ₂ -P ₁ or P _3).

As a result, when the pressure P ₂ which is the cavity portion 14 is made higher than the pressure P ₁ or P ₃ on the pipeline side, the seats 19 and 19 on both sides are surely pressed against the outer peripheral surface of the ball 11. The presence or absence of fluid leakage to the downstream pipeline can be confirmed by a gas detector (not shown) or the like via the sealant supply device 22 communicating with the downstream sealing mechanism. Can inject a sealant using the sealant supply device 22 to perform valve seat sealing.

In FIGS. 4 and 5, the cavity portion 14
The inflow valve 23 and the outflow valve 24 that inject into and out of the body 5 are screwed into the communication hole 5a of the body 5. In this example, one inlet valve 23 and one outlet valve 24 are provided, but two or more may be provided. These valves can be used as a drain valve that communicates the outside with the cavity portion 14, so that the structure of the ball valve can be made compact. The drain valve may be of a type installed on a portion other than the bottom of the body 5. As shown in FIG. 5, the discharge valve 24 and the inlet valve 23 are connected to the hose joint 23a.
The same valve structure can be used if only the hose joint 24a is changed and the hose 23b or the hose 24b is mounted. It should be noted that the hose 24b of the discharge valve 24 can be safely constructed by pulling the gas to be discharged to a place where the hose 24b can safely carry out the construction.

The inlet valve 23 and the discharge valve 24 have the same structure. The main valve 26 and the auxiliary needle 27 are provided in the main body 25, and the main needle 26 and the auxiliary needle 27 are respectively provided. It is provided to adjust the flow rate while adjusting the screwing. In addition, 28 is a lock bolt of the main needle 26, which is for preventing erroneous operation.

Further, when the ball valve is closed, an inactive gas (for example, nitrogen gas) having a pressure higher than the pipe pressure can flow into and out of the cavity portion 14 continuously from an inactive gas supply source (not shown). In addition, it is performed by continuously discharging the inert gas in the cavity portion 14 to the outside, and as described above, it is performed by appropriately adjusting the gas flow rates of the feed valve 23 and the discharge valve 24.

Next, the operation of the above embodiment will be described.
When the pipeline 1 is to be added or modified, the ball valves 2 and 3 are closed, and an inert gas such as nitrogen gas is continuously fed into the cavity portion 14 from the feed valve 23 to continuously By discharging the gas from the discharge valve 24, the cavity 14 is surely made to contain only the inert gas, and the discharge valve 2
4. Since the flow rate of the inlet / outlet valve 23 can be adjusted, the pressure necessary for the pressure in the pipeline 1 can be set and the discharge amount can be minimized.

Since the inert gas to be fed or discharged can be continuously generated, even if a sheet leak occurs, it is discharged together with the gas in the pipeline, so that the pipeline is discharged to the outflow side of the pipeline 1. There is no danger of the gas being released, and safe expansion and modification work can be performed. In this case, it is not necessary to previously provide a piping facility having a water sealing structure for water sealing.

Further, the inlet valve 23 and the outlet valve 24 shown in FIG.
May be provided in any direction as long as it can communicate the outside with the cavity portion 14, and can be appropriately selected depending on the nature of the gas in the pipeline, and these are arbitrary depending on the implementation. Since the injected inert gas can be widely distributed inside the cavity 14, the inlet valve 23 and the outlet valve 24 may be installed separately from each other. The relationship with P ₁ , P ₂ and P ₃ will be described for each case. When the pressure in the cavity portion 14 is set to be higher than that of the pipelines 1 on both the upstream side and the downstream side (P ₁ <P ₂ > P ₃ ), the cavity portion 1
By the pressure P ₂ of 4, both the seal mechanisms 15 and 16 are surely pressed against the outer peripheral surface of the ball 11 and hermetically sealed, and the pipeline fluid (gas) to the downstream side pipeline 1 is obtained.
Never leaks. When the pressure in the cavity portion 14 is set to be substantially the same as that in the upstream pipeline 1 and higher than that in the downstream pipeline (P ₁ ≈P ₂ > P ₃ ), the pressure P _{2 in the} cavity portion 14 causes the downstream pressure. Only the side sealing mechanism, for example, the sealing mechanism 16 works to perform valve seat sealing,
The pipeline fluid (gas) does not leak to the downstream pipeline 1. When the pressure in the cavity portion 14 is set to be lower than that of the upstream pipeline 1 and higher than that of the downstream pipeline 1 (P ₁ > P ₂ >)
P ₃ ), the upstream fluid pressure causes the upstream seal mechanism, eg, the seal mechanism 15, to operate, while the pressure P _{2 in the} cavity portion 14 causes the downstream seal mechanism, eg, the seal mechanism 1
6 works to seal both upstream and downstream valve seats,
The pipeline fluid (gas) does not leak to the downstream pipeline 1 side. As described above, if at least the inert gas having a pressure higher than that of the downstream pipeline 1 is fed into the cavity portion 14, regardless of the pressure of the upstream pipeline 1, the pressure of the downstream side of the ball valve is surely increased. Leakage of pipeline fluid can be prevented.

[0025]

As is apparent from the above, according to the present invention, when the pipeline is expanded or modified,
By using a compact ball valve with simple equipment, there is no risk of fluid such as gas leaking to the pipeline side, and construction can be performed safely and reliably.

Furthermore, it is possible to use the existing drain valve as the discharge valve or the inlet valve, which contributes to downsizing and cost reduction. Further, the sealing mechanism allows the high-pressure inert gas to be fed into and discharged from the cavity portion, whereby the self-tensioning force is exerted more reliably, the sheet leakage does not occur, and the work can be safely performed.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of the present invention and showing a state in which a ball valve is installed in a pipeline.

FIG. 2 is an enlarged vertical sectional view of the ball valve according to the present invention.

FIG. 3 is an enlarged detailed view of part a of FIG.

FIG. 4 is an enlarged detailed view of portion b of FIG.

5 is an explanatory view showing a joint of a feeding hose attached to the valve structure of FIG. 4. FIG.

FIG. 6 is an explanatory view of a watertight structure in a pipeline showing a conventional example.

[Explanation of symbols]

1 pipeline 2,3 ball valve 5 body 11 balls 12 Upper stem 13 Lower stem 14 Cavity part 15,16 Sealing mechanism 17 seat retainer 19 sheets 21 O-ring 23 Inlet valve 24 release valve

Claims (4)

[Claims] 1. A ball having a through hole supported by a stem is rotatably provided in a body, and a cavity is provided between an outer peripheral surface of the ball and an inner peripheral surface of the body by a sealing mechanism mounted on both sides of the ball. At the same time, the body is provided with a valve for feeding an inert gas having a pressure higher than the piping pressure at least on the ball downstream side into the cavity when the valve is closed, and a valve for discharging the inert gas from the cavity to the outside. A ball valve characterized in that. 2. A drain valve for communicating the outside and the cavity is used for at least one of the valves for feeding and releasing an inert gas into the cavity, and the flow rate of the drain valve can be adjusted. The ball valve according to claim 1, wherein the ball valve is provided. 3. The seal mechanism is a mechanism in which the seat is pressed against and brought into contact with the outer peripheral surface of the ball by a double seal system using self-forced force generated by the biasing force of a spring and the pressure in the cavity. 1. The ball valve according to 1. 4. In the valve closed state, an inert gas having a pressure higher than the piping pressure on the ball downstream side is continuously fed into the cavity to press the seat against the ball surface of the ball valve. A fluid leakage prevention method, characterized in that sealing is performed, and further, an inert gas is continuously discharged from the cavity portion to the outside so that the fluid does not leak to the downstream side of the ball valve.