JP2000179712A - Ball valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability and hold operability of a ball valve by exhibiting a function in a ball seat for a long period. SOLUTION: In a ball valve enclosing a ball 4 for opening/closing or controlling a flow passage 6, at least a sealing side ball seat in a ball seat 9 which is brought into contact with a surface of the ball 4 is formed by mixing polymerization inhibitor with fluororesin such as PFA(copolymer of tetrafluoroethylene and perfluoroalkylvinylether), PTFE(polytetrafluoroethylene), or the like, and a clearance between the ball seat 9 and a body 1 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is directed to controlling water, oil, gas or steam in the field of daily life and fluids in the manufacturing industries such as the petroleum industry, petrochemical industry, other chemical industries, and the pharmaceutical industry. More particularly, the present invention relates to a ball valve equipped with a ball seat suitable for a fluid such as a monomer such as styrene or butadiene or chlorine gas.

[0002]

2. Description of the Related Art A ring-shaped ball seat mounted on a ball valve has a sealing function in contact with a fluid, and is generally made of polytetrafluoroethylene (hereinafter, PT).
PTFE) is used in many cases, and PTFE is a material suitable as a ball seat material because it has chemical resistance, low friction, and moderate elasticity.

[0003] However, a sheet made of PTFE is made of styrene,
When applied to fluids such as ethylenically unsaturated monomers such as butadiene and vinyl chloride, the monomers permeate into the sheet material and partially polymerize, causing the seat to swell or be damaged, causing the ball valve to malfunction. And there are drawbacks such as leakage of fluid.

[0004] As an improved sheet material which solves this drawback, Japanese Patent Publication No. 2-1193 and Japanese Utility Model Publication No. 58-5148 are known.
No. 1 publication has been proposed. These sheet materials are
It is a molded product melt-formed with a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (hereinafter referred to as PFA). Similarly, a fluororesin (hereinafter, referred to as modified PTFE) obtained by improving polytetrafluoroethylene by disabling a PFA component has been proposed as an improved sheet material.

[0005]

However, the sheet molded products made of PFA or modified PTFE proposed in these publications have excellent properties such as chemical resistance, heat resistance, and non-adhesiveness like PTFE. However, a phenomenon occurs in which a monomer fluid such as styrene polymerizes and reacts with a small amount of radicals in PAF to swell the sheet. Therefore, even if this PFA or modified PTFE molded article is used, The function was impaired and the ball seat had to be replaced after a short period of use.

The present invention has been developed as a result of intensive studies in view of the problems of conventional ball seats, and has a long-lasting performance by exhibiting the functions of ball seats for a long period of time. It is an object of the present invention to provide a ball valve capable of maintaining the operability of the ball valve for a long time.

[0007]

In order to achieve the above object, an invention according to claim 1 is a ball valve having a built-in ball for opening / closing and controlling a flow path. Among them, at least the ball sheet on the sealing side is a ball valve in which a polymerization inhibitor is mixed into a fluororesin such as PFA or PTFE or modified PTFE to form a molded product, and a gap between the ball sheet and the body is eliminated.

According to a second aspect of the present invention, there is provided a ball valve having a built-in ball for opening / closing or controlling a flow path, wherein at least a sealing-side ball sheet of the ball sheet in contact with the ball surface is made of PFA or PTFE. Modified PTFE
A ball valve which is formed by mixing a polymerization inhibitor into a fluororesin or the like, has a substantially rectangular cross section of the ball sheet, and surrounds at least two sides of the ball sheet with a body or a metal ring to reduce the flow path contact surface. It is. In this case, in the case of a trunnion ball type ball valve, the ball seat is supported by a retainer urged by a spring, and the cross section of the ball sheet is substantially rectangular, and at least two sides of the ball seat are surrounded by the retainer. Let it.

According to a fourth aspect of the present invention, there is provided a ball valve including a ball for opening / closing or controlling a flow path, wherein at least a sealing-side ball sheet of the ball sheet contacting the ball surface is made of PFA or PTFE. Modified PTFE
The ball valve is a ball valve formed by mixing a polymerization inhibitor into a fluororesin or the like, and having an elastic portion that communicates a cavity provided in the body with a flow path.

The ball seat according to the first, second, third or fourth aspect is particularly preferably a molded article obtained by mixing a polymerization inhibitor into PFA.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the ball valve according to the present invention will be specifically described with reference to the drawings. In the ball valve shown in FIG. 1, a body 1 having an inlet (primary side) 2 and an outlet (secondary side) 3 is formed by connecting a bolt portion 1a and a cap 1b with bolts and nuts 1c. A ball 4 having a through hole 4a therein is provided. The ball 4 is provided so as to rotate by the rotation of the stem 5 to communicate with or block the flow path 6, and the stem 5 is shown in FIG. It is provided so as to be rotated by a manual handle 7 or an actuator mounted on the upper surface of the shaft mounting portion of the body 1. The ball 4 is not limited to the two-way valve shown in FIG. 1 and may be a three-way valve or a four-way valve.
Notched grooves formed by cutting the ball 4 may be used.

A ring-shaped ball seat 9 is mounted on a mounting portion 8 having an L-shaped cross section formed on the body 1 between the inner periphery of the body 1 and the surface of the ball 4. The ball seat 9 has a sealing function and a function of reducing the operation torque due to the rotation of the ball 4, and the ball valve of the floating ball type normally pushes the ball 4 by a fluid pressure when the ball is closed, so that the ball 4 is Acting as a sealing force on the secondary side ball seat 9, the trunnion ball type ball valve is such that the ball seat 9 exerts a sealing function on the primary side. However, the sealing may be performed on the primary side even in a floating ball type depending on the usage, and the trunnion ball type may be sealed on both the primary and secondary sides.

Therefore, the ball seat 9 in this embodiment is
It is provided at least on the side that exerts the sealing function, but the ball seat 9 in this example may be mounted on the ball seats on both sides or on the other ball seat side, and these are optional depending on the implementation. It is.

The ball seat 9 in FIG. 1 and FIG.
When molding a fluororesin such as PFA, PTFE, modified PTFE, etc., it is molded by mixing a polymerization inhibitor. In this case, since PTFE has a high melting point, P
A method is adopted in which a polymerization inhibitor is mixed with TFE powder, compression molding is performed, and then the mixture is placed in a heating furnace and heated and sintered at a temperature equal to or higher than the melting point to form a ball sheet. The PFA mixed with the agent can be melted and formed by various molding methods.

As the material of the ball sheet 9 in this embodiment, a ball sheet formed of a PFA material mixed with a polymerization inhibitor gave particularly preferable results. This polymerization inhibitor is a substance that slows down the polymerization rate only by adding a small amount to the monomer, and the polymerization inhibitor in this example includes, for example, an amine derivative, a phenol derivative or a resonance stabilizing effect on the surface. It has been confirmed that carbon fibers or carbon particles having the same are preferable.

Among them, amine derivatives include DPPD
(N, N'-diphenyl-p-phenylenediamine),
There are DNPD (N, N'-dinaphthyl-p-phenylenediamine), IPPD (N-isopropyl-N'-phenyl-p-phenylenediamine) and OPPD (N-octyl-N'-phenyl-p-phenylenediamine). ,
Among phenol derivatives, monophenols include DT
There are BMP (2,6-di-tert-butyl-4-methylphenol) and SP (styrenated phenol) (alkylated phenol) (cyclohexylated phenol), and bisphenols include MBMTB << 2,2′-methylenebis (4-methyl-6-t-butylphenol) >><< 2
2'-methylenebis (4-methyl-6-methylcyclohexylphenol), BBMTBP <<4,4'-butylidenebis (3-methyl-6-t-butylphenol) >>, TBMTBP <<4,4'-thiobis (3-methyl -6-t-butylphenol)].

In particular, in the present example, DNA (N, N'-dinaphthyl-p
-Phenylenediamine) formed from the resin mixed with 1 to 2% by weight of the ball seat 9 makes it possible to obtain a ball valve that has achieved the intended purpose.

Further, in FIG.
The character surface and the mounting portion 8 having an L-shaped cross section of the body 1 are brought into contact with each other to make a gap therebetween, thereby reducing the portion that undergoes a polymerization reaction due to liquid contact and avoiding the cause of the formation of the polymer. This prevents deposits due to the polymerization reaction from being produced on the outer periphery of the ball sheet 9.

The material of the ball seat 9 in FIGS. 3 and 4 is the same as the material shown in FIG. 2, and therefore the description thereof is omitted, but FIG. 3 particularly shows that the cross section of the ball seat 9 is substantially rectangular. In addition, two or more sides of the ball sheet 9 are surrounded by the metal ring 10 to minimize the flow path contact surface such as the liquid contact area. FIG. 4 shows the U-shaped groove-shaped mounting portion 8 a of the body 1. This is an example in which the ball sheet 9 is fitted so as to surround two or more sides of the ball sheet 9, and the cause of the formation of the polymer is avoided. This prevents deposits from being formed on the outer periphery of the ball seat 9. In the example of FIG. 3, a ball seat 9 between two metal rings 10, 10 is provided.
Has no gap in contact with the body, and the amount of the contact portion with the body can be appropriately set.

FIGS. 7 and 8 show a trunnion ball type ball valve.
Is also a ball seat using the same material as in FIG.

In particular, FIG. 7 shows O
This is an example in which the ball seat 9 is supported by a retainer 13 which is urged forward via a ring 12, the cross section of the ball seat 9 is substantially rectangular, and two or more sides of the ball seat 9 are surrounded by the retainer 13. FIG. 8 shows an example in which the retainer 13 is urged toward the ball 4 by the spring 11 via the seal ring 14 and the seal retainer 15.

The material of the ball seat 9 in FIGS. 5 and 6 is the same as the material shown in FIG. 2. In particular, one or several small outer circumferential grooves 16 are formed on the outer circumferential surface of the ball seat 9 to form a body. 1 and the cavity 17 are made in a state of uniform pressure. Also, one or a plurality of small inner peripheral grooves 18a or 18b are formed in the ball seat 9, and the inner peripheral groove 1 is formed.
The portion in which 8a or 18b is formed becomes an elastic portion 19 which is deformed by bending due to abnormal pressure rise of the cavity 17, and is provided so as to be pressure-relieved from this portion 19.

In the case of the structure shown in FIGS. 7 and 8,
When the cavity 17 is abnormally pressurized, the portion of the spring 11 becomes an elastic portion and is pressed, so that the ball seat 9 is separated from the ball 4 together with the retainer 13 and pressure-reliefed.

Next, the operation of each embodiment will be described. Since the ball sheet 9 in this example is a molded article in which a polymerization inhibitor is mixed into a fluororesin such as PFA or PTFE or modified PTFE, for example, a monomer fluid such as styrene or butadiene or a permeable fluid such as chlorine gas is used for the ball sheet 9. Even when the fluid is supplied to the valve, the fluid is absorbed by the ball seat 9 without causing a swelling action in which the size and volume of the ball seat 9 increase, and the monomer fluid undergoes a polymerization reaction in the ball seat 9. Since there is no polymer, there is no possibility that a polymer is generated in the ball seat 9, and the operability of the ball 4 is maintained.

In particular, since the gap between the ball sheet 9 and the body 4 is eliminated and the contact surface of the ball sheet 9 with the flow path is reduced as much as possible, the ball sheet 9 exhibits a swelling-resistant effect, It surely prevents the occurrence of things.

Further, since the ball seat 9 has the pressure relief function, the ball seat 9 can prevent the inconvenience due to abnormal pressure rise by the ball seat 9 in combination with the above-described swelling action. it can.

When a butadiene monomer was supplied to the ball valve in each of the examples of FIGS. 2 to 8 in which the ball seat 9 of the present embodiment was mounted, an experiment was conducted.
Although there was a remarkable increase in dimensional change due to swelling in months, it was confirmed that the ball sheet 9 in the present invention had no dimensional change even after 5 months, swelling and polymer generation were prevented, and had a long life. Also, no increase in the operating torque of the ball 4 with the ball seat 9 mounted thereon was observed, and no failure occurred due to abnormal pressure rise in the cavity. In particular, in the example of FIG. 2, it was confirmed that there was no significant dimensional change even after one year, and that the life was long.

[0028]

Thus, according to the present invention, there is provided a ball seat having a high durability because it has a swelling action as compared with the conventional ball seat product and can prevent the generation of polymerization products. It is possible to obtain a ball valve that maintains the sealing property without lowering the operability of the ball valve.

Further, according to the present invention, it is possible to mount a ball seat capable of reliably removing abnormal pressure rise in a cavity in a body,
A long-life ball seat can be obtained, and it can be applied to various ball valves.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a ball valve according to the present invention.

FIG. 2 is an enlarged view of a part a in FIG.

FIG. 3 is an enlarged view of a part a showing another example of FIG. 1;

FIG. 4 is an enlarged view of a part a showing still another example of FIG. 1;

FIG. 5 is an enlarged view of a part a showing still another example of FIG. 1;

FIG. 6 is an enlarged view of a part a showing still another example of FIG. 1;

FIG. 7 is an enlarged view of a portion a showing still another example of FIG. 1;

FIG. 8 is an enlarged view of a portion a showing still another example of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body 4 Ball 6 Flow path 8, 8a Mounting part 9 Ball seat 10 Metal ring 11 Spring 13 Retainer 16 Outer peripheral groove 18a, 18b Inner peripheral groove 19 Elastic part

[Procedure amendment]

[Submission date] December 18, 1998 (1998.12.
18)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

[0004] As an improved sheet material which solves this drawback, Japanese Patent Publication No. 2-1193 and Japanese Utility Model Publication No. 58-5148 are known.
No. 1 publication has been proposed. These sheet materials are
It is a molded product melt-formed with a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (hereinafter referred to as PFA). Similarly, a fluororesin (hereinafter referred to as modified PTFE) improved by adding a PFA component to polytetrafluoroethylene has been proposed as an improved sheet material.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

A ring-shaped ball seat 9 is mounted on a mounting portion 8 having an L-shaped cross section formed on the body 1 between the inner periphery of the body 1 and the surface of the ball 4. The ball seat 9 has a sealing function and a function of reducing the operation torque due to the rotation of the ball 4, and the ball valve of the floating ball type normally pushes the ball 4 by a fluid pressure when the ball is closed, so that the ball 4 is acts as a sealing force against the secondary side of the ball seat 9, trunnion ball type ball valve would ball seat 9 on the primary side to exhibit a sealing function. However, the sealing may be performed on the primary side even in a floating ball type depending on the usage, and the trunnion ball type may be sealed on both the primary and secondary sides.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

When a butadiene monomer was supplied to the ball valve in each of the examples of FIGS. 2 to 8 in which the ball seat 9 of the present embodiment was mounted, an experiment was conducted.
There was a significant dimension change due to swelling in months, the ball seat 9 in the present invention, there is no dimensional change after 5 months, prevents the occurrence of swelling and the polymer product is, it was confirmed a long lifetime, Also, no increase in the operating torque of the ball 4 with the ball seat 9 mounted thereon was observed, and no failure occurred due to abnormal pressure rise in the cavity. In particular, it was confirmed that the example shown in FIG. 2 did not show any significant dimensional change even after one year, and had a long life. ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 6, 1999 (1999.1.6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

However, the sheet molded products made of PFA or modified PTFE proposed in these publications have excellent properties such as chemical resistance, heat resistance, and non-adhesiveness like PTFE. However, a phenomenon in which a monomer fluid such as styrene polymerizes and reacts with a minute amount of radicals in PFA to cause swelling of the sheet, so that even if the molded article of PFA or modified PTFE, The function was impaired and the ball seat had to be replaced after a short period of use.

Claims (4)

[Claims] 1. A ball valve having a built-in ball for opening / closing or controlling a flow path, wherein at least a sealing-side ball sheet of a ball sheet in contact with the ball surface is made of tetrafluoroethylene, perfluoroalkyl vinyl ether and A ball valve formed by mixing a polymerization inhibitor into a fluororesin such as a copolymer or polytetrafluoroethylene, and eliminating a gap between a ball seat and a body. 2. A ball valve having a built-in ball for opening / closing or controlling a flow path, wherein at least a sealing-side ball sheet of a ball sheet contacting the ball surface is made of tetrafluoroethylene, perfluoroalkyl vinyl ether and A mixture of a copolymer or a fluororesin such as polytetrafluoroethylene mixed with a polymerization inhibitor is formed, and the cross section of the ball sheet is substantially rectangular, and at least two sides of the ball sheet are surrounded by a body or a metal ring. A ball valve having a reduced flow path contact surface. 3. The ball valve according to claim 2, wherein the ball seat is supported by a retainer urged forward by a spring, the cross section of the ball seat is substantially rectangular, and two or more sides of the ball seat are surrounded by the retainer. 4. A ball valve incorporating a ball for opening / closing or controlling a flow path, wherein at least a sealing-side ball sheet of a ball sheet in contact with the ball surface is made of tetrafluoroethylene, perfluoroalkyl vinyl ether, The ball seat is formed by mixing a polymerization inhibitor into a fluororesin such as a copolymer or polytetrafluoroethylene, and the ball seat communicates with the cavity when the cavity provided in the body is pressurized. A ball valve provided with a resilient portion.