JP2005048853A - Ball valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball valve for ultra-low temperature fluid capable of securely maintaining the sealing property of a seat retainer and a ball without causing distortion on a seal face of a ball seat, achieving pressure relief securely in accordance with abnormal rise of pressure in a cavity, and being safely used for a long time even when using ultra-low temperature fluid such as liquefied petroleum gas and liquefied natural gas. <P>SOLUTION: This ball valve 1 is constituted in such a way that the annular ball seat 12 nipped between the annular seat retainer 11 and an outer ring 16 is abutted on a surface of the ball to seal a section between the ball 3 and the seat retainer 11. A recessed mounting channel 13 in which the ball seat 12 is mounted is formed on a ball face side of the seat retainer 11. A clearance 14 equivalent to difference of dimension in heat shrinkage between the seat retainer 11 and the ball seat 12 is provided between an inner peripheral face 12a of the ball seat 12 mounted in the mounting channel 13 and an inner peripheral face 13a on a flow passage side of the mounting channel 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultra-low temperature trunnion-type ball valve suitable for controlling an ultra-low temperature fluid such as liquefied petroleum gas or liquefied natural gas, and more particularly to a ball valve excellent in sealing performance.

  In the trunnion type ball valve, the applied fluid is an ultra-low temperature fluid such as liquefied ethylene (liquefaction temperature: -104 ° C), liquefied natural gas (liquefaction temperature: -160 ° C), liquid nitrogen (liquefaction temperature: -196 ° C), etc. In the case of a resin ball sheet, the flexibility of the sheet is lost, the sealing performance is lowered, and fluid leakage may occur. For this measure, conventionally, there has been proposed means for securing a sealing property between the ball seat and the ball by interposing an elastic member such as a leaf spring between the ball seat and the body. However, it could not be said to ensure good sealing performance.

Therefore, a resin such as tetrafluoroethylene resin (PTFE) or a rubber ball sheet is inserted into a mounting groove formed on a metal sheet retainer such as stainless steel, and this ball sheet is elastically supported by a disc spring or the like. A structure in which the seat retainer and the ball are sealed by being bounced to the ball side through a member is often employed (for example, see Patent Document 1).
However, in the low temperature range, or even in the ultra low temperature range, the ball sheet, in particular, the portion including the seal surface protruding from the mounting groove causes local deformation due to the difference in thermal shrinkage with the seat retainer, and the ball sheet Since the sealing surface is distorted, good sealing performance cannot be maintained, and the problem of sealing performance has not yet been solved.
Japanese Patent Publication No. 3-47167 (page 1-3, FIG. 2)

  The present invention has been developed as a result of diligent research in order to solve the above-described problems of conventional trunnion-type ball valves. The purpose of the present invention is to apply liquefied petroleum gas as an applied fluid. Even for ultra-low temperature fluids such as natural gas and liquefied natural gas, the seal performance of the ball retainer and the ball is reliably maintained without causing distortion on the ball seat seal surface, and in response to abnormal pressure increase in the cavity An object of the present invention is to provide a ball valve for a cryogenic fluid that can be reliably pressure-relieved and can be used safely over a long period of time.

  In order to achieve the above object, the invention according to claim 1 is configured such that a ball having a through hole is rotatably mounted in a body, and an annular seat retainer and an outer ring are provided on both sides or one side of the ball surface. In a ball valve configured to abut a ring-shaped ball seat held between the two and seal between the ball and the seat retainer, the ball seat is mounted on the ball surface side of the seat retainer A concave mounting groove is formed, and the ball valve is provided with a predetermined gap between the inner peripheral surface of the ball seat mounted in the mounting groove and the flow path side inner peripheral surface of the mounting groove.

  In the invention according to claim 2, the gap is a gap corresponding to a difference in heat shrinkage between the seat retainer and the ball seat.

  The invention according to claim 3 is a ball valve in which a ball seat mounted in the mounting groove is held by an outer ring via a tightening member.

Invention, the width of the inner part surface and the clamping surface of the outer ring of the mounting groove and T _1, the width of the ball seat which is clamped between the inner part surface and the clamping surface of the outer ring mounting groove according to claim 4 If the set to T _2, at the lowest working temperature, a nipped ball valve as T ₁ and T ₂ are substantially equal.

  The invention according to claim 5 is the ball valve in which a pair of lip portions are formed on the sealing surface of the ball seat that seals the inner surface of the seat retainer.

In the invention according to claim 6, when the seal point diameter of the ball sheet is D ₁ and the seal point diameter of the lip portion located on the inner peripheral side of the lip portion is D ₂ , D ₁ > D ₂ It is a ball valve.

  The invention according to claim 7 is a ball valve in which a metal seat portion is formed on the seat retainer.

  According to an eighth aspect of the present invention, a ball having a through-hole is rotatably mounted in the body, and an annular shape held between the annular seat retainer and the outer ring on both sides or one side of the surface of the ball. In the ball valve configured to contact the ball seat and seal between the ball and the seat retainer, a tongue-like opening is provided between the inner peripheral surface of the body and the outer peripheral surface of the seat retainer. And a ball valve equipped with a U-ring composed of a spring for expanding the opening with the primary side as the opening.

  According to the ninth aspect of the present invention, a U-ring presser is attached to a groove formed on the outer peripheral surface of the seat retainer on the primary side, and the protrusion formed on the U-ring presser is brought into contact with the spring from the opening of the U-ring. This is a ball valve that is locked.

Balls invention according to claim 10, the seal point diameter of the ball seat and D _1, if the outer diameter of the U-ring which is mounted between the body and the seat retainer and the D _3, which is a D 1 _{<D 3} It is a valve.

According to the ball valve of the present invention, even if the applied fluid is an ultra-low temperature fluid such as liquefied petroleum gas or liquefied natural gas, the seal point between the ball seat and the ball is generated without causing distortion on the seal surface of the ball seat. It was possible to move while maintaining good sealing performance, and it became possible to ensure high sealing performance over a long period of time.
In addition, pressure relief can be reliably performed in response to abnormal pressure increase in the cavity.

A preferred embodiment of the seat structure of the ball valve in the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a trunnion-type ball valve 1, and as shown in FIG. 1, a primary-side flow path 4 and a secondary channel communicated with a body 2 through a through-hole 3 a formed in the ball 3. A side flow path 5 is provided, and seal mechanisms 6 and 7 to be described later are provided at peripheral portions of the opening ends in the body 2 of the primary side flow path 4 and the secondary side flow path 5. The ball 3 is rotatably provided in the body 2 via the. Further, as shown in the figure, the ball 3 is supported by the upper stem 8 and the lower stem 9, and the lower end of the upper stem 8 penetrating the upper portion of the body 2 is attached to the upper portion of the ball 3. The upper end of the upper stem 8 is fixed to a valve driving means (not shown), and the ball 3 is rotated by operating this valve driving means, so that the primary side flow path 4 and the secondary side flow path 5 are communicated / blocked. Is done. In the figure, reference numeral 10 denotes a so-called cavity formed by the body 2, the ball 3, and the seal mechanisms 6 and 7 when the valve is fully closed or fully opened.

2 is an enlarged cross-sectional view of the primary-side seal mechanism 6 shown in FIG. 1, and FIG. 3 is an enlarged cross-sectional view of the secondary-side seal mechanism 7.
As shown in FIGS. 1 to 3, the sealing mechanisms 6 and 7 of the present invention have an annular ball seat on the ball surface side of an annular seat retainer 11 slidable in the axial direction of the flow path of the body 2. A concave mounting groove 13 for mounting 12 is formed. Between the inner peripheral surface 12a of the ball seat 12 mounted in the mounting groove 13 and the flow path side inner peripheral surface 13a of the mounting groove 13, a ball A gap 14 corresponding to the difference in thermal shrinkage between the sheet 12 and the sheet retainer 11 is provided. In this example, the ball sheet 12 formed of ethylene trifluoride resin (hereinafter referred to as PCTFE) is used, but the present invention is not limited to this and may be made of other materials.

The seat retainer 11 is formed with a female thread portion 11b, and the ball seat 12 mounted in the mounting groove 13 is connected to the ring-shaped outer ring via a tightening member 15 such as a bolt screwed to the female thread portion 11b. 16 is holding. The clamping surface 16a of the outer ring 16 is a plane perpendicular to the axial direction, and the ball seat 12 can be smoothly contracted along this plane. Further, as shown in FIG. 4, the width of the holding surface 16a of the inner part surface 13b and the outer ring 16 of the mounting groove 13 and _{T 1,} and the holding surface 16a of the inner part surface 13b and the outer ring 16 of the mounting groove 13 If the width of in the ball seat 12 which is held to a T _2, at the lowest working temperature, by sandwiching the ball seat 12 so as T ₁ and T ₂ are substantially equal, the ball along the holding surface 16a sheets 12 can be smoothly contracted.

  In addition, a pair of ring-shaped lip portions 12c and 12c are formed on the sealing surface 12b of the ball sheet 12 that seals the inner surface 13b of the mounting groove 13, and the ball sheet 12 even when the ball sheet 12 contracts. The contact surface pressure between the seat retainer 11 and the seat retainer 11 can be increased, and fluid leakage from the back surface of the ball seat is prevented.

As shown in FIG. 4, D ₁ is a seal point diameter between the ball sheet 12 and the ball 3 on the primary side, and D ₂ is a lip portion 12 c located on the inner peripheral side of the lip portion and a mounting groove 13. of a seal point diameter of the inner part surface 13b, which sets the relationship between _{D 1} and _{D 2} to _D 1> _{D 2.} As a result, the ball seat 12 is pressed against the seat retainer 11 by the fluid pressure, and the surface pressure between the back surface 13b and the lip portions 12c and 12c is increased, thereby preventing back leakage through the surface. .

  Further, an annular metal sheet portion 17 is provided on the ball surface side of the seat retainer 11 so that the metal sheet portion 17 is metalized on the ball 3 even if the ball sheet 12 is melted or burned off due to a fire or the like. It keeps the sealing performance in emergency by touching, exhibits a fire-safe function, and prevents the ball seat 12 from popping out. In this example, the metal seat portion 17 is used to form a concave mounting groove 13 for mounting the ball sheet 12 on the seat retainer 11, thereby simplifying the structure.

In the figure, reference numeral 18 denotes a U-ring having a substantially U-shaped cross section having a tongue-shaped opening 18a, and a spring 19 is inserted into the opening 18a so as to expand the tongue-shaped opening 18a. Has been. As shown in the figure, the U-rings 18 and 18 of the primary and secondary side seal mechanisms 6 and 7 are arranged with the inner peripheral surface of the body 2 in a state where the opening 18a faces the primary side with respect to the flow path. When the pressure on the opening side is higher than the pressure on the side opposite to the opening 18a, the tongue-shaped opening 18a is expanded and exhibits a self-sealing effect. In addition, the inner peripheral surface of the body 2 and the outer peripheral surface of the seat retainer 11 are reliably sealed to prevent passage of fluid from the opening side.
The U-ring 18 can also be sealed from the opposite side of the opening 18a by increasing the spring strength, and the U-ring 18 in the primary-side sealing mechanism 6 is increased when the pressure in the cavity 10 is increased. After slightly moving to the opening 18a side, the pressure in the cavity 10 is applied to the outer diameter position of the U-ring 18 by engaging with the seat retainer 11 so that the ball seat 12 and the ball 3 It is structured to perform pressure relief from the middle.

That is, as shown in FIG. 2, in the sealing mechanism 6 on the primary side, the U ring 18 is locked to the seat retainer 11, and therefore, in this example, the U ring presser 20, which is a two-piece annular member, is It is attached to the groove 11c formed in the retainer 11, and the protrusion 20a formed on the U-ring presser 20 comes into contact with the spring 19 from the opening 18a of the U-ring 18 so that the U-ring 18 is locked. I have to. Further, as shown in FIG. 3, in the secondary-side seal mechanism 7, the protrusion 11 d formed on the seat retainer 11 comes into contact with the spring 19 from the opening 18 a of the U-ring 18 to engage the U-ring 18. and so as to stop, when the ball valve is in the valve closed state, the outer diameter of the U-ring 18, the fluid pressure acts on the area difference between the sealing point diameter D ₁ that will be described later, the ball seat 12 the ball 3 side It is structured to be pushed and sealed. In the seal mechanisms 6 and 7, the protrusions 20a and 11d prevent damage to the U-ring 18 body made of PCTFE in this example.

  Further, on the inner peripheral surface of the body 2 on the primary side and the secondary side, a step portion 2a having an inclined surface is formed, and an elastic member attached to the step portion 2a, in this example, a leaf spring 21, A slanted spring receiving surface 11e formed on the seat retainer 11 is elastically ejected, and the ball seat 12 mounted in the mounting groove 13 together with the seat retainer 11 is elastically biased toward the ball 3 side. In addition, before and after the leaf spring 21, a gap is provided in which the seat retainer 11 can retreat.

As shown in FIG. 2, D ₁ is a seal point diameter between the ball seat 12 and the ball 3 on the primary side, and D ₃ is mounted between the inner peripheral surface of the body 2 and the outer peripheral surface of the seat retainer 11. and an outer diameter of the U-ring 18, which sets the relationship between _{D 1} and _{D 3} to _D 1 _{<D 3.} As a result, the leaf spring 21 is set to a necessary minimum load only for applying an initial surface pressure between the ball 3 and the ball seat 12 in order to perform self-sealing valve seat sealing using fluid pressure. In addition, due to the contraction of the ball seat 12, the seat retainer 11 has a load that can be retracted.

As shown in FIG. 1, the ball 3 to which the upper stem 8 is attached is formed with a vent hole 3b, so that the cavity pressure and the piping pressure can be made equal when the valve is opened. Further, as shown in FIG. 3, D ₁ is a seal point diameter between the ball seat 12 and the ball 3 on the secondary side, and D ₄ is a distance between the inner peripheral surface of the body 2 and the outer peripheral surface of the seat retainer 11. an inner diameter of the U-ring 18 mounted between, the relationship between D ₁ and D ₄ are set to D _1> D _4, thereby, the valve closing, the sealing mechanism 7 on the secondary side cavity When pressure increases, while the U-ring 18 is engaged with the stepped portion 2b of the body 2 to move in close contact, D ₁ and acts are cavity pressure area difference between D _4, the ball seat 12 is a ball 3 Therefore, the cavity pressure is relieved only to the primary side of the valve via the primary-side seal mechanism 6. Also, during maintenance, the cavity pressure is reliably wiped by opening the valve.

Next, the operation of the ball valve of the present invention in a low temperature state will be described.
As shown in FIG. 5, when the valve body 1 is brought into an ultra-low temperature state by the ultra-low temperature fluid, the ball seat 12 that seals between the ball 3 and the seat retainer 11 starts to contract. As described above, between the inner peripheral surface 12a of the ball sheet 12 mounted in the mounting groove 13 and the flow path side inner peripheral surface 13a of the mounting groove 13, there is a difference in thermal shrinkage between the ball sheet 12 and the seat retainer 11. A corresponding gap 14 is provided, and the ball sheet 12 is contracted in the radial direction so as to fill the gap 14 as shown by an arrow in the figure without being prevented from contracting.

  For example, when the diameter φ169.8 mm of the inner peripheral surface 12 a of the ball sheet 12 and the diameter φ169.0 mm of the flow channel side inner peripheral surface 13 a of the mounting groove 13, this dimensional difference is φ0.8 mm, and at the minimum operating temperature, When the ball seat 12 contracts, the dimensional difference φ0.8 mm (gap 14) is set to be substantially zero.

  At the same time, the contraction force in the radial direction is converted into a component force in the axial direction by the contact angle between the ball 3 and the ball sheet 12, and the ball sheet 12 is moved together with the seat retainer 11 and the ball 3 as shown by the arrow in FIG. Retreat away from. Accordingly, since the shrinkage of the ball sheet 12 in the radial direction and the axial direction is not hindered, the seal point between the ball 3 and the ball sheet 12 can be satisfactorily sealed without causing deformation of the seal surface of the ball sheet 12. It is possible to move while maintaining the property.

  Further, as the ball seat 12 moves backward, the seat retainer 11 presses the spring 19, and the resilience of the spring 19 increases. Therefore, the ball seat 12 can maintain a good sealing point with the ball 3 by retreating, and the pressing force to the ball 3 can be increased to ensure a good valve seat sealing performance.

When the ball valve is closed, the ball seat 12 is pushed to the ball 3 side and sealed by the self-sealing force of the sealing mechanisms 6 and 7 and the elastic force of the leaf spring 21 due to fluid pressure.
Further, when the pressure in the cavity 10 rises and becomes equal to or higher than a predetermined pressure, the primary-side seal mechanism 6 moves the U-ring 18 and is locked to the U-ring presser 20, and the seat retainer 11 By being integrated, the cavity pressure that has entered the space between the U-ring 18 and the step 11f of the seat retainer 11 is canceled out.
Accordingly, when the cavity pressure acts on the area difference between the outer diameter D ₃ and the seal point diameter D ₁ of the U ring 18, the ball sheet 12 is pressed to the opposite side of the ball 3 by this pressure, and the sheet The retainer 11 moves away from the ball 3 and retreats, and a gap is generated between the ball 3 and the ball seat 12, so that the pressure abnormally increased from the gap can be relieved.

Next, a sealing performance test was performed on the above-described ball valve of the present invention, and the test results are shown in Table 1.
As shown in Table 1, when the ball valve of the present invention is compared with a ball valve (comparative product) that does not have a gap (gap 14 in the figure), the difference in the amount of seat leakage clearly appears as the pressure increases. You can see that Therefore, as is clear from this test, it can be seen that the ball valve of the present invention maintains a very good sealing performance even at a high pressure.

It is a longitudinal cross-sectional view of the trunnion type ball valve in the present invention. FIG. 2 is an enlarged cross-sectional view of a primary side seal mechanism shown in FIG. 1. FIG. 2 is an enlarged cross-sectional view of a secondary side seal mechanism shown in FIG. 1. It is action | operation explanatory drawing of the seal mechanism at the time of normal temperature. It is action | operation explanatory drawing of the seal mechanism at the time of low temperature.

Explanation of symbols

1 Trunnion type ball valve (valve body)
2 Body 3 Ball 3a Through hole 11 Seat retainer 11c Groove 12 Ball seat 12a Inner peripheral surface 12b Seal surface 12c Lip portion 13 Mounting groove 13a Inner peripheral surface 13b Back surface 14 Clearance 15 Tightening member (bolt)
16 Outer ring 16a Holding surface 17 Metal sheet part 18 U ring 18a Opening 19 Spring 20 U ring presser 20a Protrusion part

Claims (10)

  A ball having a through hole is rotatably mounted in the body, and an annular ball seat held between the annular seat retainer and the outer ring is brought into contact with both sides or one side of the surface of the ball, In the ball valve configured to seal between the ball and the seat retainer, a concave mounting groove for mounting the ball seat is formed on the ball surface side of the seat retainer. A ball valve characterized in that a predetermined gap is provided between the inner peripheral surface of the ball seat and the inner peripheral surface of the mounting groove on the flow path side.   The ball valve according to claim 1, wherein the gap is a gap corresponding to a thermal shrinkage dimensional difference between the seat retainer and the ball seat.   The ball valve according to claim 1 or 2, wherein a ball seat mounted in the mounting groove is held by an outer ring via a tightening member. In claim 3, the mounting width of the inner part surface and the clamping surface of the outer ring and T ₁ of the groove, T ₂ the width of the ball seat which is clamped between the inner part surface and the clamping surface of the outer ring of the mounting groove In this case, the ball valve is clamped so that T ₁ and T ₂ are substantially equal at the minimum use temperature.   The ball valve according to any one of claims 1 to 4, wherein a pair of lip portions are formed on a sealing surface of a ball seat that seals a back surface of the mounting groove. A seal point diameter of the ball seat and D _1, of the lip, the seal point diameter of the lip portion located on the inner peripheral side when the D _2, D _1> D ₂ and the of claims 1 to 5 The ball valve according to any one of claims.   The ball valve according to any one of claims 1 to 6, wherein a metal seat portion is formed on the seat retainer.   A ball having a through hole is rotatably mounted in the body, and an annular ball seat held between the annular seat retainer and the outer ring is brought into contact with both sides or one side of the surface of the ball, In the ball valve configured to seal between the ball and the seat retainer, a tongue-like opening is formed between the inner peripheral surface of the body and the outer peripheral surface of the seat retainer, and the opening is expanded. A ball valve having a U-ring formed of a spring that has a primary side as an opening side.   A U-ring presser is mounted on the groove formed on the outer peripheral surface of the seat retainer on the primary side, and the protrusion formed on the U-ring presser is brought into contact with the spring from the opening of the U-ring to be locked. The ball valve according to claim 8. 10. The ball according to claim 8, wherein D ₁ <D ₃ , where D ₁ is a diameter of a seal point of the ball seat and D ₃ is an outer diameter of a U-ring mounted between the body and the seat retainer. valve.

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