JP2016084905A - Trunnion type ball valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a trunnion type ball valve capable of realizing high sealability while preventing dropping of a ball seat from a seat retainer even against high pressure fluid, relieving abnormal increased pressure in a cavity while avoiding abrasion of the ball seat, restricting an increasing in the number of component elements to assure its strength while simplifying its structure and capable of improving its workability and assemblability.SOLUTION: A ball seat 6 is installed within an installing groove 22 formed at a seat retainer 5 so as to prevent jumping out and under free-state and at the same time a surplus pressure caused by an abnormal increased pressure in a cavity 25 at the time of full-closed state or full-opened state is moved in a direction opposite to that of a ball 3 by a self-restraining force of the seat retainer 5, and the ball seat 6 is pushed out toward the ball 3 with fluid pressure flowed to the rear surface side of the ball seat 6 in the installing groove 22 to relief it into a flow passage 15 through a communication part arranged between an inner peripheral surface 17 of the ball seat 6 and the installing groove 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a trunnion type ball valve, and more particularly to a mounting structure of a ball seat and a seat retainer that can exhibit high sealing performance while avoiding abnormal pressure increase in a valve cavity.

  A trunnion type ball valve is a valve that is particularly suitable for high-pressure fluids. Normally, a ball seat that serves as a valve seat is mounted on a body while being held by a seat retainer, and this ball seat is valved by the resilient force of a coil spring. It is provided in a structure in which fluid is sealed with a primary (upstream) ball sheet by being ejected in the body direction and pressed against the ball sheet.

  In this way, when the ball seat and the seat retainer are separate, the ball seat is provided in a structure that prevents the ball seat from falling off. Screws are provided on the female screw and the seal ring, respectively, and the seal ring is attached to the seat via the female screw and the male screw. A disc spring is mounted on the back of the seat, and the disc and the seal ring are pressed in the valve body direction by the disc spring. The seal ring is pressed against the valve body by a compression coil spring mounted on the back side in a state in which the thread ends of each other are brought into contact with each other and are prevented from popping out of the seat due to looseness. The gap between the contact surfaces is prevented. A seal member is provided on the inner diameter side of the seal ring, and this seal member prevents the pressure from entering the back side, and prevents the pressure ring from entering the back of the seal ring caused by the back ring action. Yes.

  In the ball valve in Patent Document 2, a serrated uneven portion is formed in the packing liner, and the seat packing is coupled to the packing liner by entering the seat packing into the serrated uneven portion. At that time, the sheet packing is integrated with the packing liner in a press-fitted state, thereby preventing back leakage from the sheet packing. Further, since the back surface of the seat packing is fixed in a state where it is press-fitted into the packing liner, the seat packing is prevented from popping out due to the back pressure action of the fluid pressure.

  On the other hand, in the ball valve of Patent Document 3, a valve seat holding ring is engaged with the outer periphery on the back side of the valve seat, and a fluid communication groove is provided circumferentially on the engagement surface of the valve seat holding ring. By equalizing the pressure difference between the inlet-side flow passage pressure and the pocket pressure from the fluid communication groove through the fluid communication hole, the valve seat is pulled back to the normal position to prevent deformation and breakage. ing.

JP-A-9-133225 Japanese Utility Model Publication No. 2-124377 Utility Model Registration No. 2577156

  In a trunnion-type ball valve with a general structure in which the ball seat is repelled by a coil spring, when abnormal pressure rises in the cavity, the ball seat moves to the primary side together with the seat retainer and moves between the seat and the valve body. Since the pressure is relieved, wear of the contact surface with the valve body of the seat becomes severe. As a result, the seal point becomes unstable and the relief pressure varies, and the pressure is released so that the contact portion of the sheet can be pry open during relief, so that the contact surface is easily damaged.

  In the ball valve of Patent Document 1, relief when abnormal pressure rises in the cavity is not considered. Further, since this ball valve has a disc spring, a compression coil spring, and a seal member in addition to the seal ring and the seat, the number of parts increases and the structure becomes complicated. In this case, since a large number of grooves and dents for component mounting are formed in the seal ring, the rigidity of the entire seal ring is liable to decrease, and in order to solve this problem, it is necessary to use a high-strength material as the seal ring material. Sometimes. Furthermore, since the seal member is disposed on the inner diameter side of the seal ring and the compression coil spring is provided on the back surface side of the seal ring, the assemblability is poor.

In the ball valve of Patent Document 2, since the seat packing is easily consumed due to the relief of abnormal pressure increase in the cavity, the seat packing is integrated by being press-fitted into the packing liner. If the temperature rises, it may expand and jump out of the packing liner.
Since this sheet packing is provided with a taper in the vicinity of the back as a leakage preventing structure and is intended to be integrated with the packing liner due to the wedge effect, it is difficult to set the dimensions of the packing liner and the sheet packing. When the sheet packing is press-fitted into the packing liner by such an uneven structure, the assembling work becomes difficult. At that time, if the seat packing is not deformed to a predetermined state, the seat packing may not fit in a predetermined position of the packing liner, and the seat packing may be partially worn during assembly and valve operation. Therefore, when the sheet packing is fixed to the packing liner by press-fitting, it is necessary to process the sheet surface after press-fitting.

  In the ball valve of Patent Document 3, the pressure difference is reduced through the fluid communication groove and the fluid communication hole when the valve body is rotated to prevent the valve seat from popping out and deforming. Is not taken into account.

  The present invention has been developed in order to solve the conventional problems, and its purpose is to exhibit high sealing performance while preventing the ball seat from falling off the seat retainer even for high-pressure fluid, Providing a trunnion-type ball valve that relieves abnormal pressure increase in the cavity while avoiding wear of the ball seat, and that can reduce the number of parts, simplify the structure, secure strength, and improve workability and assembly There is to do.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a seat retainer in which a ball seat is mounted on one or both of balls having a through hole provided in a body, and the ball is rotated through a stem. In the ball valve provided, the ball seat is prevented from popping out into the mounting groove formed in the seat retainer and mounted in a free state, and an excessive pressure rise due to abnormal pressure increase in the cavity when fully closed or fully opened. The pressure is moved in the opposite direction to the ball by the self-tensioning force of the seat retainer, and the ball seat is pushed out to the ball side by the fluid pressure flowing into the back side of the ball seat in the mounting groove to It is a trunnion type ball valve configured to relieve in the flow path through a communication portion provided between the mounting groove.

  In the invention according to claim 2, the engaging portion provided on the inner peripheral opening side of the mounting groove is opposed to the engaging portion provided on the outer peripheral mounting side of the ball seat so as to be able to be locked in the inserting direction. It is a trunnion type ball valve in which the ball seat is prevented from jumping out of the mounting groove and the ball seat is mounted in the mounting groove in a free state.

  According to a third aspect of the present invention, the threaded portion is provided as an engaging portion to be provided in the inner periphery of the mounting groove, and the male threaded portion of the ball seat is screwed into the female threaded portion as the engaging portion, and the rear end side of the male threaded portion This is a trunnion type ball valve in which the rear end side of the female threaded portion is provided so as to be able to be locked and the ball seat is prevented from popping out.

  The invention according to claim 4 is a trunnion-type ball valve in which the thread at the inner end of the female screw portion and the screw thread at the outer end of the male screw portion are locked to prevent the ball seat from popping out.

  The invention according to claim 5 is a trunnion-type ball valve in which at least one relief groove communicating with the communicating portion is formed on the inner circumferential surface of the ball seat or the mounting groove of the seat retainer facing the inner circumferential surface. .

  According to the first aspect of the invention, the ball seat is mounted while preventing the ball retainer from popping into the mounting groove of the seat retainer, and the ball seat is prevented from dropping even when a high-pressure fluid flows or the valve is slightly opened. High sealing performance can be demonstrated. When the ball seat is attached to the seat retainer in a free state, even if abnormal pressure rises when fully closed or fully opened, the seat retainer is moved in the opposite direction to the ball by the so-called self-tightening force that uses the pressure in the cavity. In addition, the excess pressure due to abnormal pressure increase in the cavity is relieved in the flow path through the communication portion between the inner peripheral surface of the ball seat and the mounting groove, so that the ball seat Prevent wear on the contact surface with the ball. For this reason, the relief point at the time of the valve closing seal can be stabilized and the abnormal pressure increase can be surely avoided, and when the valve is closed, the high sealing performance is maintained and the high pressure fluid is prevented from leaking. In addition, the relief mechanism can be configured with a ball seat and a seat retainer to reduce the number of parts, simplify the internal structure, install the ball seat while ensuring strength without increasing grooves and dents, and improve workability and assembly. Can also be improved.

  According to the second aspect of the present invention, the ball seat is mounted on the seat retainer mounting groove in a free state, so that the ball seat is movable relative to the seat retainer when a force in the protruding direction is applied to the ball seat. In addition, while the fluid between the back side of the ball seat and the seat retainer flows to the secondary side, the ball seat can be prevented from popping out by the opposing engaging portion and locking portion.

  According to the third aspect of the present invention, since the female thread portion is provided as an engaging portion and the male screw portion as a locking portion so as to be able to be locked in the loading direction, it is easy to utilize these screws. The ball seat can be attached to the seat retainer, and after screwing, the ball seat can be reliably prevented from popping out by locking the rear end side of the opposing male screw portion and the rear end side of the female screw portion. .

  According to the fourth aspect of the invention, the ball sheet is reliably prevented from popping out by locking the screw threads while preventing the ball sheet and the seat retainer from re-screwing and maintaining the free state of the ball sheet. . Moreover, the threads can be easily formed without complicated processing at the time of manufacture, and assembly is also easy.

  According to the invention of claim 5, when the cavity and the flow path side can communicate with each other by the relief groove, the seat retainer and the ball seat move in opposite directions due to self-tightening force, and the ball seat rear surface is separated from the seat retainer. Furthermore, the abnormal pressure increase can be eliminated by discharging the pressure in the cavity through the relief groove.

It is a longitudinal section showing a 1st embodiment of a trunnion type ball valve of the present invention. It is an AA cross-section schematic in FIG. It is BB expanded sectional drawing in FIG. It is the longitudinal cross-sectional view which showed the assembly process of the ball seat. It is a partially expanded sectional view which shows the state at the time of abnormal pressure | voltage rise generation | occurrence | production. It is a partially expanded sectional view which shows the state which the ball seat of FIG. 5 moved. FIG. 4 is a partially enlarged cross-sectional view showing a slightly opened state of the ball in a region E in FIG. 3. It is a principal part expanded sectional view of 2nd Embodiment of the trunnion type | mold ball valve of this invention. It is a principal part expanded sectional view of 3rd Embodiment of the trunnion type | mold ball valve of this invention. It is a perspective view which shows the principal part of 4th Embodiment of the trunnion type | mold ball valve of this invention.

  Hereinafter, embodiments and operations of a trunnion type ball valve according to the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the trunnion type ball valve of the present invention in an opened state, and FIG. 2 shows an enlarged cross-sectional view taken along the line BB in FIG. 1, that is, the central cross section of the trunnion type ball valve of the present invention. A plane view is shown.

  1 has a body 2, a ball 3, a stem 4, a seat retainer 5, and a ball seat 6, and in particular, a high-pressure fluid of class (nominal pressure) 150 to 2500. Suitable for use as an application.

The body 2 has an annular body 10 and annular caps 11, 11 on both sides, which are made of carbon steel, stainless steel, or the like, and are integrated by bolts and nuts 12.
In the body 2, a ball 3 is rotatably provided via a stem 4 including an upper stem 4 a and a lower stem 4 b, and a seat retainer in which a ball seat 6 is mounted on both the balls 3, that is, on the upstream and downstream sides. 5 is disposed. The ball 3 is made of stainless steel, and is provided with a through hole 3 a that can communicate with the flow path 15 in the valve body 1. In this embodiment, the ball seat 6 and the seat retainer 5 are attached to both the balls 3, but these may be provided on one of the balls 3.

The ball sheet 6 is formed in an annular shape from a resin material such as PTFE (polytetrafluoroethylene), nylon, PEEK (polyetheretherketone), and a sealing surface 16 is provided on the contact side of the ball 3. 16 is provided with an annular inner peripheral surface 17 up to the end side.
On the seat retainer 5 mounting side on the outer periphery of the ball seat 6, a male screw portion 20 is provided as a locking portion, and this male screw portion 20 is provided up to about half the length in the mounting direction of the ball seat 6. .

3 and 4, at least one relief groove 21 is formed on the inner peripheral surface of the ball seat 6. The relief groove 21 is provided from the vicinity of the boundary between the inner peripheral surface 17 and the seal surface 16 to the end side at a predetermined depth, and the relief groove 21 is formed on the ball seat 6 after being mounted on the seat retainer 5. It is provided so that it can communicate with the communication part 30 provided between the inner peripheral surface 17 side and the outer peripheral surface side (male screw part 20 side). The relief grooves 21 are desirably provided at a plurality of locations on the inner peripheral surface 17 of the ball seat at equal intervals. Further, the relief groove may be provided in a mounting groove 22, which will be described later, of the seat retainer 5 that faces the inner peripheral surface 17 of the ball seat 6.
Although not shown, for a large-diameter valve of size 10B or more, a groove or a hole that can be tightened or removed by a tightening jig may be provided on the outer periphery of the ball seat 6. Easy assembly.

  On the other hand, the seat retainer 5 is provided in a substantially cylindrical shape with a metal material such as carbon steel or stainless steel so that the mounting side of the ball seat 6 is slightly enlarged in diameter, and the ball seat 6 is inserted therein. A possible annular mounting groove 22 is provided. On the opening side of the inner periphery of the mounting groove 22, a female screw portion 23 that can be screwed with the male screw portion 20 is provided as a projecting engagement portion. The female thread portion 23 is provided from the opening side to approximately half the length of the mounting groove 22, and the thread 23 a of the female thread portion 23 is the threaded portion 20 of the ball seat 6 in the case of the valve body 1 of size 3B. The same specifications as the screw thread 20a. A bottomed hole 24 having a diameter larger than the outer diameter of the male threaded portion 20 is provided on the back side of the female threaded portion 23, and the depth of the bottomed hole 24 is formed to be larger than the length of the male threaded portion 20. The inner diameter of the bottomed hole 24 is slightly larger than the outer diameter of the external thread portion 20.

  The male thread portion 20 is screwed into the female screw portion 23 of the mounting groove 22 of the seat retainer 5, and the ball seat 6 is inserted into the mounting groove 22 in a state where the male screw portion 20 is accommodated in the bottomed hole 24. The After the male screw portion 20 and the female screw portion 23 are screwed together, the rear end side of the male screw portion 20 and the rear end side of the female screw portion 23 face each other so as to be latchable in the loading direction of the male screw portion 20. The ball sheet 6 is prevented from jumping out from the mounting groove 22, and the ball sheet 6 is mounted in a free state, that is, in a state of being movable at least in the direction of the flow path center axis L with respect to the mounting groove 22.

  After the ball seat 6 is mounted, excess pressure due to abnormal pressure increase in the cavity 25 of the valve body 1 when fully closed or fully opened is moved in the opposite direction to the ball 3 by the self-tightening force of the seat retainer 5, and The ball sheet 6 is pushed out to the ball 3 side by the fluid pressure flowing into the back surface side of the ball sheet 6 in the mounting groove 22, and at this time, abnormal pressure increase in the cavity 25 is relieved in the flow path 15 through the communication portion 30. It has become so. Here, the abnormal pressure increase in the cavity 25 means that the body 2 or the ball 3 in the valve body 1 in the valve closed state is caused by an increase in the temperature of the fluid or a high temperature in the environment in which the valve body 1 is installed. This is a phenomenon in which the pressure in the closed space (cavity 25) surrounded by the ball seat 6, the seat retainer 5 and the like increases.

  Here, as shown in FIG. 7, when pressure is applied to the back side of the ball sheet 6, the pushing load generated on the ball sheet 6 acts on the threads 20a and 23a. It is necessary to provide the ball seat 6 and the seat retainer 5 so as to set the thread height so as to ensure the material strength (screw shear strength) that prevents the sheet 6 from popping out. In this case, the force applied to the threads 20a, 23a is prevented from exceeding the yield point of the material of the ball seat 6, and even if the ball seat 6 contracts at a low temperature in consideration of the minimum operating temperature of the valve body 1, the threads are separated. The dimensions should be set so as to catch.

  The screw threads 20a and 23a are desirably fine threads, and in this case, the height of the screw threads can be adjusted while ensuring the number of threads by shortening the screw length as much as possible. Further, since the fine screw has a short pitch, it is preferable in the trunnion type ball valve of the present invention in that the number of incomplete threads in the circumferential direction is reduced.

  In this embodiment, in the case of the valve body 1 of size 3B, the ball seat material: PTFE, the thread height: about 0.8 mm, the thread pitch: 1.5 mm (using fine screws), and the minimum operating temperature: −46 ° C. The amount of shrinkage in the radial direction of the ball sheet is about 0.5 mm, and the hook is about 0.6 mm (considering thermal shrinkage on the metal side).

  When the ball seat 6 is mounted on the seat retainer 5, in FIG. 4 (a), the ball seat 6 is rotated in the screwing direction while the screw portion 20 is positioned in the mounting groove 22, and screwed in the arrow direction. To. As shown in FIG. 4B, when the ball seat 6 is screwed in until the screw thread 20a is removed from the screw thread 23a, these screw connections are released, and the ball sheet 6 is prevented from coming off from the seat retainer 5. It becomes free in the state.

  At this time, the depth of the bottomed hole 24 is larger than the length of the male threaded portion 20 as described above, so that the screw thread 20a surely exceeds the region of the threaded thread 23a, and the male threaded portion 20 is in the bottomed hole 24. It is possible to charge until it is accommodated in the housing, and a clearance C in the loading direction (the direction of the flow path center axis L in FIG. 1) is provided between the threads 20 and 23a as shown in FIG. Since the inner diameter of the bottomed hole 24 is slightly larger than the outer diameter of the external thread portion 20, a radial gap G is also provided between them. In the range of the clearance C, it is possible to advance and retreat with little sliding resistance. The dimensions such as the clearance C and the size of the gap G are set in consideration of the environmental temperature at the time of assembly and the temperature difference due to the difference in the assembly location. In the case of this embodiment, it is provided so as to be able to cope with an assembly temperature of a maximum of 40 ° C. in the summer and a minimum of 10 ° C. in the winter.

  After the assembly, the ball seat 6 is rotated in the direction opposite to the screwing direction, and it is confirmed that the ball seat 6 does not re-screw or drop off. In this case, the ball seat 6 is rotated until the highest portion (completely threaded portion) between the thread 23a of the seat retainer 5 and the thread 20a of the ball seat 6 is locked, and the screw tip start portions are not Do not align the positions of the complete threaded parts). As a result, re-screwing of the ball seat 6 after the seat retainer 5 is mounted is prevented, and the ball seat 6 is reliably moved.

  Here, when the male screw portion 20a is compared to a timepiece in FIG. 2, the start portion of the screw tip is preferably arranged so as to avoid the 3 o'clock position x. This is because when the valve body 1 in the valve closed state is turned to the valve open state by rotating the stem 4 counterclockwise, the flow path 15 closed by the ball 3 begins to open from the position 3 o'clock, This is because when the flow velocity at the beginning of opening of the valve is high, the ball seat 6 tends to pop out. Specifically, it is preferable to arrange the highest portions of the thread 23a of the seat retainer 5 and the thread 20a of the ball seat 6 at the 3 o'clock position.

  In the above embodiment, the threaded portion 20 is provided on the outer peripheral side of the ball seat 6 and the female threaded portion 23 is provided on the seat retainer 5, but the female threaded portion is provided on the inner peripheral side of the ball seat 6 and the threaded portion is provided on the seat retainer 5. (Both not shown), and the ball seat 6 may be mounted in the mounting groove 22 of the seat retainer 5 in a free state while screwing them together as described above.

  Moreover, the latching | locking part 20 and the engaging part 23 may each be other than a screw, and the latching | locking part 20 and the engaging part 23 mutually latch, and the ball seat 6 protrudes from the seat retainer 5. As long as the ball seat 6 can be mounted in the mounting groove 22 in a free state, these can be provided in various shapes.

Next, the operation of the above-described embodiment of the trunnion type ball valve of the present invention will be described.
The trunnion-type ball valve according to the present invention is shown in FIG. 5 because it prevents popping out in the mounting groove 22 of the seat retainer 5 and allows the high-pressure fluid to be sealed by the ball seat 6 mounted in a free state. The structure can be simplified while minimizing the number of points, and the ball seat 6 can be mounted simply by screwing it into the seat retainer 5.

  At the time of this assembly, the male screw portion 20 and the female screw portion 23 can be screwed together to insert the ball seat 6 into the bottomed hole 24, thereby preventing wear or damage without applying excessive force. However, it can be mounted accurately and easily to a predetermined position with a small number of assembly steps. At this time, it is possible to mount the seat retainer 5 and the ball seat 6 with sufficient clearance C and gap G without requiring a special jig or the like, and extra stress is generated from the initial state of assembly. Prevents and has good durability during operation. Furthermore, it can be assembled in a state that is not easily affected by the environmental temperature.

  Further, by avoiding the press-fitting of the ball seat 6 by screwing, there are many options for the sheet material, for example, various materials such as a low temperature material, a high temperature material, a low strength material, and a high strength material. A material can be used, and even when the ball seat 6 is provided with a high-strength material, the mounting is easy. After the ball seat 6 is completely screwed in, the ball seat 6 can be mounted in a state of idling to the bottomed hole 24 side, so that the ball seat 6 can be naturally loosened without a separate member for preventing looseness. Dropping can be prevented.

When the valve main body 1 is in a fully closed state, as shown in FIG. 3, the ball seat 6 is pressed against the ball 3 via the seat retainer 5 by the coil spring 31, whereby the sealing surface 16 of the ball seat 6 is Leakage is prevented by tightly sealing the ball 3 over the entire circumference. In this case, the seat retainer 5 and the cap 11 are sealed with an O-ring 32 and a packing 33.
As shown in FIG. 7A, the back surface 6 a of the ball seat 6 is in close contact with the seat retainer 5 at the innermost diameter position P, and prevents fluid from passing through the valve cavity 25 from this portion.

  When the valve body 1 is opened to be in a slightly opened state, the ball seat 6 that has been pressed against the ball 3 as described above is not subject to being pressed due to the rotational movement of the ball 3. The fluid pressure flowing in through the pressure is applied to the back surface 6a of the ball sheet 6, and the ball sheet 6 is instantaneously pushed out toward the ball 3 as shown in FIG. 7B.

  At this time, the rear end side of the screw thread 20a of the male screw part 20 and the screw thread 23a of the female screw part 23 abuts (locks) to prevent the ball seat 6 from popping out. When the pressure applied to the back surface 6a of the ball sheet 6 and the pressure in the cavity 25 become the same pressure, the force by which the ball sheet 6 is pushed out to the ball 3 side is lost.

  When the valve body 1 is fully opened, the sealing surface 16 of the ball seat 6 is tightly sealed to the ball 3 again over the entire circumference, as shown in FIG.

  When the pressure in the cavity 25 increases due to abnormal pressure increase, the ball seat 6 is pushed by this pressure as shown in FIG. 5 and tilts toward the inner diameter side as shown by the arrow in the figure. Due to this deformation, the ball seat 6 and the ball 3 are sealed with a seal diameter φdR at a seal point R slightly smaller in diameter than the seal point before occurrence of abnormal pressure increase, and the ball seat 6 and the seat retainer 5 are sealed at the seal point P. Sealing is performed with a back seal diameter φdP.

In this ball sheet 6, the pressure in the cavity 25 (cavity pressure) is applied to both the seal surface 16 side and the back surface 6a side. Here, on the seal surface 16 side and the back surface 6a side, each seal point has a seal diameter φdR> back surface seal diameter φdP.
A difference is provided in the seal diameter so that Using this difference in diameter, the force applied to the back side of the ball sheet 6 by the cavity pressure is set to be larger than the force applied to the ball 3 side, and the ball sheet 6 is pushed out to the ball 3 side. Yes.

This pushing force is
[Cavity pressure P] × [Cavity pressure receiving area X on the back surface of the ball sheet 6]
Can be expressed as
The pressure receiving area is
(ΦdR−φdP) ² × π × 4
Can be expressed as

  On the other hand, the cavity pressure is applied to both the cap 11 side and the mounting groove 22 side of the ball seat 6 in the seat retainer 5. The seat retainer 5 is sealed from the inner periphery of the cap 11 by an O-ring 32 on the cap 11 side. In this embodiment, this seal point is represented by D, and this seal diameter is represented by retainer seal diameter φD.

Here, on the cap 11 side and the mounting groove 22 side of the ball seat 6, each seal point is φdD> φdR.
A difference is provided in the seal diameter so that By utilizing this difference in diameter, the seat retainer 5 is set to be pulled back to the opposite side of the ball 3 against the elastic force of the coil spring 31 by the cavity pressure.
This pullback force is also called self-tension,
[Cavity pressure P] × [Cavity pressure receiving area Y in the mounting groove 22 of the ball sheet 6]
Can be expressed as The pressure receiving area Y is
(ΦdP−φdR) ² × π × 4.

  FIG. 6 shows a state in which the ball sheet 6 is pushed out to the ball 3 side by the cavity pressure. In this way, the fluid pressure from the cavity 25 that has flowed into the gap G between the external thread portion 20 and the internal thread portion 23 of the back surface side of the ball sheet 6 in the mounting groove 22 pushes the ball sheet 6 toward the ball 3, The fluid pressure in the cavity 25 is relieved in the flow path on the primary side of the ball 3 through the relief groove 21 from the communication portion 30 between the inner peripheral surface 17 and the mounting groove 22.

  Since the seat retainer 5 is also pulled back to the opposite side of the ball 3 by the cavity pressure, as described above, the ball seat 6 is quickly pushed between the back surface 6a of the ball seat 6 and the mounting groove 22 of the seat retainer 5. Thus, the gap G can be formed, and the fluid in the cavity 25 can be relieved from the back surface 6 a of the ball seat 6 to the flow path 15 on the primary side via the communication portion 30.

  As described above, even when the ball seat 6 moves in a free state through the mounting groove 22 of the seat retainer 5 and the pressure inside the cavity 25 is abnormally increased for some reason, the mechanism can release this pressure to the flow path side. By providing, the so-called self-relief function is exhibited, and the position of the seal point P on the back side is always constant, so that the self-relief function is stabilized and the abnormal pressure increase is surely eliminated. Directionality can be easily controlled.

  Even when the ball sheet 6 expands due to the high-pressure fluid and the volume increases, the volume increase is relieved in the clearance C, and the wear of the sealing surface 16 due to the ball sheet 6 coming out or bulging toward the ball 3 side is reduced. Can be avoided.

  In this case, the protrusion of the ball seat 6 due to the back pressure action of the fluid pressure can be controlled by the relationship between the thread shear strength and the ball seat back pressure, that is, the relationship between the material strength and the pressure acting area on the back side. If the ball seat 6 is formed while adjusting the angle, it is possible to reliably prevent popping out.

  FIG. 8 shows a second embodiment of the trunnion type ball valve of the present invention. In the following embodiments, the same parts as those in the above embodiments are denoted by the same reference numerals, and the description thereof is omitted.

Here, as shown in FIG. 8, when the ball sheet 6 is pressed against the ball 3, the diameter of the ball sheet 6 is increased along the spherical surface of the ball 3 as indicated by the arrow, particularly on the sealing surface side of the ball sheet 6. Adds force to deform in the direction. Then, the sealing position between the ball seat 6 and the ball 3 may be shifted.
Further, since the ball sheet 6 is enlarged in diameter and provided in the mounting groove 22 of the seat retainer 5, the ball sheet 6 may be damaged if it is excessively pressed against the screw portion 23. Such a diameter expansion phenomenon of the ball seat 6 is more conspicuous when a fast-flowing fluid enters the narrow space between the ball 3 and the ball seat 6 in the slightly opened state of the valve body 1 as shown in FIG. It becomes.

In order to prevent these, in this embodiment, the front end side of the thread 23a of the female thread portion 23 is cut out, and a surface 23b parallel to the outer periphery of the ball seat 6 is provided. Thereby, the stress concentration in the contact portion between the screw thread 23a and the ball sheet 6 can be relaxed, and damage to the ball sheet 6 can be prevented.
Further, by setting the inner diameter of the parallel surface 23b of the screw thread 23a to a dimension close to the outer diameter of the ball sheet 6, the expansion of the ball sheet 6 is suppressed, and the deviation of the sealing position between the ball sheet 6 and the ball 3 is suppressed. Can be reduced.

  FIG. 9 shows a third embodiment of the trunnion type ball valve of the present invention. In this embodiment, by forming an inclined surface 6b inclined toward the inner diameter on the back surface 6a side of the ball sheet 6, the back surface 6a of the ball sheet 6 and the sheet are located at a position P closest to the inner diameter of the inclined surface 6b. Sealing with the mounting groove 22 of the retainer 5 is performed. Thereby, in the fully open state shown in FIG. 1 or the fully closed state shown in FIG. 2, the fluid pressure from the flow path 15 does not enter the back surface 6 a of the ball seat 6.

  In addition, in FIG. 8 described above, the back surface 6a of the ball seat 6 is annular at a position P closest to the inner diameter, while being parallel to the bottom surface of the mounting groove 22 of the seat retainer 5 and perpendicular to the flow path axis L of FIG. The protrusion 40 may be provided. In this case, the gap between the seat retainer 5 and the mounting groove 22 can be sealed by the annular protrusion 40 on the innermost diameter side of the back surface 6 a of the ball seat 6.

  FIG. 10 shows a seat retainer and a ball seat in the fourth embodiment of the trunnion type ball valve of the present invention. In this embodiment, as shown in FIG. 10 (a), in the seat retainer 5, an annular edge portion having two to four notches 50 in the circumferential direction instead of the female thread portion provided on the inner periphery of the mounting groove. 51. On the other hand, instead of the male thread portion provided on the outer periphery of the ball seat 6, two to four annular protrusions 52 corresponding to the notch portions 50 are provided in the circumferential direction.

  When the ball seat 6 is mounted on the seat retainer 5, the ball seat 6 is inserted into the seat retainer 5 with the annular protrusion 52 aligned with the position of the notch 50 as shown in FIG. Next, the ball seat 6 is rotated with respect to the seat retainer 5 in the direction of the arrow in FIG. 10B until the annular protrusion 52 shown in FIG. Like that. Accordingly, the annular protrusion 52 is engaged with the annular edge 51 in FIG. 10C, and the ball seat 6 is mounted in a free state, that is, in a movable state with respect to the mounting groove 22 by this rotational engagement. , It can be prevented from falling off.

  The embodiment of the present invention has been described in detail above, but the present invention is not limited to the above-described embodiment, and the scope does not depart from the spirit of the invention described in the claims of the present invention. Thus, various changes can be made.

DESCRIPTION OF SYMBOLS 1 Valve body 2 Body 3 Ball 3a Through-hole 4 Stem 5 Seat retainer 6 Ball seat 17 Inner peripheral surface 20 Male thread part (locking part)
20a, 23a Thread 21 Relief groove 22 Mounting groove 23 Female thread part (engagement part)
25 cavity 30 communication part

Claims (5)

  In a ball valve in which a seat retainer in which a ball seat is mounted is disposed on one or both of the balls having a through hole provided in a body, and the ball is rotatably provided via a stem. The seat retainer is prevented from popping into the mounting groove formed in the seat retainer and mounted in a free state, and excessive pressure due to abnormal pressure increase in the cavity when fully closed or fully opened is Is moved in the opposite direction, and a communicating portion provided between the inner peripheral surface of the ball sheet and the mounting groove is formed by pushing the ball sheet to the ball side by the fluid pressure flowing into the back surface side of the ball sheet in the mounting groove. A trunnion type ball valve characterized by relief in the flow path.   The engaging portion provided on the opening side of the inner periphery of the mounting groove is opposed to the engaging portion provided on the outer peripheral mounting side of the ball seat so as to be able to be locked in the loading direction. The trunnion-type ball valve according to claim 1, wherein the ball seat is prevented from popping out and is mounted in the mounting groove in a free state.   The threaded portion is provided as an engaging portion to be provided in the inner periphery of the mounting groove, and the male threaded portion of the ball seat is screwed into the female threaded portion as a locking portion, and the rear end side of the male threaded portion and the female threaded portion The trunnion-type ball valve according to claim 2, wherein the rear end side of the ball seat is provided so as to be locked to prevent the ball seat from jumping out.   4. The trunnion-type ball valve according to claim 3, wherein the internal thread of the female thread portion and the external thread of the external thread portion are locked to prevent the ball seat from popping out.   The at least 1 relief groove | channel which communicates with the said communication part is formed in the mounting groove of the seat retainer facing the inner peripheral surface of this ball seat or this inner peripheral surface. Trunnion type ball valve.

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