valve

Abstract

To provide a valve that has a long neck structure suitable for an ultra-low temperature fluid, which opens / closes a channel by lifting / lowering of a valve body, can be simply installed while accurately centering a stem, is provided with a back sheet structure at a height preventing the entry of a fluid to prevent abnormal pressure rise and ground leakage, and can be easily provided with the back sheet structure at high machining accuracy.SOLUTION: A yoke 2 having a packing storage portion 12 is installed on an upper part of a hood 4 of a long neck structure, and a stem 6 is mounted so as to be lifted / lowered. A valve body 7 at a lower end of the stem 6 is provided so as to open / close a channel 8, and a stem through-hole 11 is formed with an annular projecting portion 13. The annular projecting portion is formed so as to fit with a stem insertion hole 30 side. A yoke side back sheet surface 14 is provided in the annular projecting portion, and a stem side back sheet surface 50 is provided in the middle of the stem. In a back sheet mechanism 52, those abut and seal with each other at the time of the maximum lifting-up of the stem.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a valve that opens and closes a flow path inside a body by raising and lowering a valve element, and in particular to a valve with a long neck structure that handles ultra-low temperature fluids such as LNG (liquefied natural gas) and liquid hydrogen. [Background technology]

[0002] Typically, valves for cryogenic fluids such as LNG and liquid hydrogen are provided with a long-neck structure with an extended bonnet cover, known as an extension bonnet, to prevent the gland from freezing, according to standards such as ISO. By lengthening the bonnet in this way, the distance from the valve element (flow path) to the operating part must be at least a certain distance. Examples of this type of cryogenic valve include gate valves, globe valves, needle valves, and plug valves, all of which have a structure in which the valve element is raised and lowered by a stem to open and close the flow path.

[0003] These cryogenic valves typically include a back seat mechanism. When the valve element is raised to open the flow path, a sealing surface on the stem side (the rising side) contacts a sealed surface on the bonnet side to prevent gland leakage. If a liquid enters above the back seat mechanism, the temperature rise can cause the liquid to vaporize and gasify. For example, LNG expands approximately 600 times upon gasification, potentially damaging the packing downstream of the back seat mechanism and causing gas to leak. To prevent this, the ISO standard (ISO 28921-1) requires that long-neck valves be equipped with a function to prevent abnormal pressure buildup in the space between the back seat mechanism and the packing. To address this issue, a back seat mechanism is typically installed at a height that makes it difficult for liquid to enter.

[0004] An example of a valve with a back seat mechanism located at a high position where liquid is less likely to penetrate is the gate valve disclosed in Patent Document 1. This valve has a long-neck bonnet formed as an integral part, and a tapered seating surface (the sealed side) is formed below the packing mounting area inside the bonnet, while a tapered annular seal (the sealing side) is formed on the stem side. When fully open, the annular seal abuts and seals against the seating surface, thereby providing a back seat function by the bonnet-side seating surface and the stem-side annular seal near the top of the bonnet and preventing the escape of the medium fluid. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 63-64671 Summary of the Invention [Problem to be solved by the invention]

[0006] In the long-neck valves described above, the stem is longer to match the length of the extension bonnet, and the longer the stem, the more difficult it becomes to align the stem with the bonnet, yoke, etc. due to bending and distortion that occur during molding and processing. If these are assembled in a misaligned state, the stem may tilt, resulting in insufficient sealing on the side where the packing for preventing fluid leakage is installed near the operating part, and on the backseat mechanism side, the sealing surface on the stem side may come into uneven contact with the sealed surface on the bonnet side, resulting in insufficient sealing, and the necessary sealing may not be achieved in each of these areas.

[0007] When manufacturing a bonnet, there is also the problem of the need to perform so-called backseat machining to create a tapered seating surface (backseat surface) on the inner peripheral surface at a high position inside the bonnet with a one-piece long neck structure. For example, a cutting tool must be inserted deep into the inner peripheral surface of the bonnet from the outside, and the cutting tool must be brought into contact with the surface to be machined in a manner that makes it difficult to see from the outside. Furthermore, because the seating surface must be tapered with a uniform inclination angle and machined to a precise surface roughness, machining can become extremely difficult, potentially resulting in reduced machining accuracy.

[0008] The present invention was developed to solve the problems of the past, and its purpose is to provide a valve with a long neck structure suitable for cryogenic fluids, which opens and closes a flow path by raising and lowering a valve body, which can be easily installed while accurately centering the stem, and which has a back seat structure provided at a height that prevents fluid intrusion, thereby preventing abnormal pressure increases due to fluid expansion and reliably preventing gland leakage, and which can easily be installed with high processing precision. [Means for solving the problem]

[0009] In order to achieve the above object, the invention according to claim 1 is a valve device in which a stem is mounted on the upper part of a bonnet with a long neck structure so as to be movable up and down, with a yoke having a sealing packing storage section attached thereto, a flow path in the body being opened and closed freely by a valve body attached to the lower end of the stem, an annular protrusion that protrudes toward the bonnet side is formed around the bonnet side opening of a stem through-hole provided in the yoke, and this annular protrusion is formed so as to be able to fit into the stem insertion hole provided on the bonnet side, and a tapered yoke side back seat surface that increases in diameter as it approaches the bonnet is provided on the inner periphery of the opening of the annular protrusion, and a tapered stem side back seat surface that decreases in diameter as it approaches the yoke is provided midway on the stem, and a back seat mechanism is provided in which the yoke side back seat surface and the stem side back seat surface come into contact and seal when the stem is lifted up to the maximum. a gasket chamber surrounded on all four sides by the opposing surfaces of the annular protrusion and the annular step is provided between an annular protrusion provided on the outer periphery of the annular protrusion and an annular step provided on the outer periphery opening side of the stem insertion hole, a gasket is disposed on the outer periphery of the annular protrusion, and this gasket is sandwiched between the underside of the yoke and the upper side of the bonnet, and is attached to the gasket chamber in a state where it is disposed between the side surface of the outer periphery of the tip of the annular protrusion and the side surface of the annular step, and the yoke is attached to the bonnet.

[0010] The invention of claim 2 is a valve in which the yoke is detachably attached to the bonnet, and when the yoke is removed from the bonnet, the annular protrusion protrudes beyond the surrounding surface facing the bonnet, so that the yoke-side back seat surface can be exposed.

[0013] Claim 3 The invention relates to a valve in which an annular protrusion provided on the underside of the bonnet is fitted into an annular stepped portion provided on the upper surface of the body, and the bonnet is attached to the body in a centered state.

[0014] Claim 4 The invention relates to a valve in which the inclination angle of the yoke-side back seat surface from the axial direction of the stem is slightly larger than the inclination angle of the stem-side back seat surface from the axial direction of the stem. [Effects of the Invention]

[0015] According to the invention of claim 1, the valve has a long neck structure suitable for cryogenic fluids, in which the valve element moves up and down to open and close the flow path. By fitting the annular protrusion on the yoke side into the stem insertion hole on the bonnet side, the yoke and bonnet can be easily integrated while accurately aligning their centers when connecting these components. After the valve is assembled, the yoke-side back seat surface and packing are mounted on the same yoke, so the stem is kept centered by the packing, and the stem can be accurately centered with respect to the yoke-side back seat surface. This allows the stem to be accommodated in the bonnet in a centered state. With the stem centered as described above, a backseat mechanism is provided at a height that prevents fluid from entering between the bonnet and the yoke. This backseat mechanism has a tapered yoke-side backseat surface and a tapered stem-side backseat surface that come into contact and seal when the stem is lifted to its maximum. This allows the yoke-side backseat surface and the stem-side backseat surface to form a tight seal, providing excellent sealing properties that prevent fluid expansion and abnormal pressure increases, thereby reliably preventing gland leakage.

[0016] Furthermore, by housing the packing around the stem through-hole of the yoke and providing a yoke-side backseat surface with an annular protrusion directly below the packing, the distance between the packing and the yoke-side backseat surface can be reduced. When a seating surface is provided below the packing mounting portion inside the bonnet, as in Patent Document 1, the cavity between the packing mounting portion and the seating surface increases as the distance between them increases. If the cavity becomes larger when a liquid fluid enters the cavity, the fluid expands significantly within the cavity. This expansion pressure can cause an abnormal increase in pressure, placing an excessive load on the packing. In contrast, according to the present invention, when the stem-side backseat surface and the yoke-side backseat surface abut and seal to form the backseat mechanism, the effect of suppressing fluid expansion within the cavity is improved, reducing the load on the packing and improving durability.

[0017] Since the yoke side back seat surface is provided on the inner circumference of the opening of the annular protrusion, this yoke side back seat surface can be easily provided together with the stem side back seat surface with high processing precision, thereby providing a back seat structure that can reliably prevent fluid leakage. By placing the gasket on the outer periphery of the annular protrusion of the yoke, the gasket can be easily positioned and installed as desired, and the gasket can be securely sandwiched between the yoke and the bonnet in a sealed state, making it possible to easily assemble them while ensuring sealing. When the yoke and bonnet are butted together, accurate centering is achieved by the two-stage engagement between the annular protrusion and the stem insertion hole, and between the annular protrusion and the annular step, allowing the yoke and bonnet to be assembled in an accurately positioned state. When the valve is fully open and the stem-side back seat surface abuts the yoke-side back seat surface, and a force is applied to the annular protrusion in a direction pushing it outward, the annular protrusion is supported by the annular step, preventing it from tilting and reliably maintaining high sealing performance from the back seat surface. A gasket chamber is formed between the annular protrusion and the annular step, and by pressing the gasket into this gasket chamber, it is placed between the yoke and the bonnet with a filling rate of 100% or more, preventing it from protruding or falling out, and improving the sealing performance of the gasket to prevent leakage from between the yoke and the bonnet.

[0018] According to the invention of claim 2, a high-precision yoke-side backseat surface can be easily formed by precise surface processing on the yoke before it is attached to the bonnet, and the yoke-side backseat surface can be exposed by removing the yoke from the bonnet, making maintenance of this yoke-side backseat surface easy.

[0021] Claim 3According to the invention, the yoke and bonnet can be attached in a centered state, allowing them to be assembled together with the axial center from the body through the bonnet to the yoke accurately aligned. This makes it possible to minimize the clearance between the stem and the inner surface of the bonnet. This minimizes the area where fluid can enter the upper part of the flow path, preventing expansion due to temperature rise of the liquid cryogenic fluid flowing through the flow path, reducing the adverse effects on the packing and preventing damage to the packing.

[0022] Claim 4 According to the invention, by providing an angle difference between the inclination angle of the yoke-side back seat surface and the stem-side back seat surface, when the valve is fully open, the two back seat surfaces initially come into line contact, and by increasing the force in the valve opening direction from this state, the stem-side back seat surface is pushed into the yoke-side back seat surface in a wedge-like manner, resulting in surface contact. This prevents leakage from occurring in a line contact state, where leakage is likely to occur from positions with low surface pressure if there is distortion or the like at the contact position, and this line contact allows the seal surface pressure to be increased gradually to surface contact, thereby demonstrating sealing performance. It is also possible to increase the sealing performance of the back seat mechanism as needed, ensuring sufficient sealing performance when the valve is fully open. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a longitudinal cross-sectional view showing an embodiment of a valve of the present invention. [Figure 2] 1 is a perspective view of one embodiment of a valve of the present invention. FIG. [Figure 3] FIG. 2 is an enlarged cross-sectional view of part A in FIG. [Figure 4] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, the valve of the present invention will be described in detail based on an embodiment. 1 and 2 show an embodiment of the valve of the present invention, and FIG. 3 shows an enlarged cross-sectional view of part A in FIG. In the figure, the valve of the present invention (hereinafter referred to as valve body 1) is a cryogenic valve consisting of a gate valve, and this valve body 1 comprises a yoke 2, sealing packing 3, bonnet 4, body 5, stem 6, and valve element 7. With the yoke 2 attached to the bonnet 4, the stem 6 is axially mounted so that it can move up and down freely, and the valve element 7 is attached to the lower end of this stem 6, and this valve element 7 forms a straight flow path 8 within the body 5 that can be opened and closed freely.

[0025] 4, yoke 2 is made of a low-temperature resistant metal material such as stainless steel, and has a flange 10 near its bottom for connection to bonnet 4, with yoke 2 fixed to the top of bonnet 4 via this flange 10. A stem through-hole 11 is provided in the axial center of yoke 2, and a packing housing portion 12 for housing packing 3 is formed near the connection side of stem through-hole 11 with bonnet 4, and packing 3 is attached to packing housing portion 12.

[0026] On the underside of the yoke 2, an annular protrusion 13 having a smaller diameter than the flange portion 10 is formed around the bonnet 4 side opening of the stem through-hole 11 so as to protrude toward the bonnet 4 attached to the lower part of the yoke 2. A tapered yoke-side backseat surface 14 is formed on the inner periphery of the opening of the annular protrusion 13, the diameter of which increases as it approaches the bonnet 4. In this embodiment, the inclination angle θ1 of the yoke-side backseat surface 14 from the axis P of the stem 6 is formed to be approximately 30°.

[0027] When an ultra-low temperature fluid such as LNG or liquid hydrogen flows inside the bonnet 4, the yoke-side backseat surface 14 must be positioned higher than the highest height that the liquid may reach as it rises while maintaining its liquid state, and the length (height) of the bonnet 4 must be set accordingly. The highest height that the liquid may reach is the height at which the fluid flowing through the flow path 8 reaches its boiling point. For example, if the fluid is LNG, the average boiling point is -162°C, although this varies depending on the composition of the fluid, and the height at which the temperature is higher than this boiling point corresponds to this height.

[0028] An enlarged annular protrusion 15 is formed on the outer periphery of the annular protrusion 13 of the yoke 2, and the flange 10 is provided so as to protrude from the outer periphery of the annular protrusion 15. An annular gasket 16 is provided so as to be able to be placed (attached) on the side of the annular protrusion 15 facing the bonnet 4. A pair of gland bolts 17 are journaled on the upper surface of the yoke 2 so as to be rotatable in a direction intersecting the journaling direction of the yoke 2.

[0029] 1 and 3, the sealing packing 3 is formed into a cylindrical shape using, for example, expanded graphite containing a reinforcing material, and is attached around the stem 6 while being housed in the packing housing portion 12. A gland 20, which is formed in a substantially cylindrical shape with approximately the same outer diameter as the packing 3, is placed on the outer periphery of the stem 6 above the packing 3, and a plate-shaped gland holder 21 is attached above the gland 20 with the stem 6 passing through its center. The gland holder 21 has a pair of insertion holes 22 into which the tips of the gland bolts 17 can be inserted. With the packing 3 and gland 20 sandwiched between the yoke 2 and the gland holder 21, the tips of the gland bolts 17 are inserted into the insertion holes 22, and a gland nut 23 for fixing the gland bolts 17 is screwed onto them.

[0030] When the gland bolt 17 and the gland nut 23 are tightened, the tightening force is transmitted to the packing 3 via the gland holder 21 and the gland 20, and the packing 3 is tightened into the packing storage section 12, thereby sealing the shaft.

[0031] In Figures 1 to 3, the yoke 2 is removably attached to the bonnet 4 via four sets of mounting bolts and nuts 24. When the yoke 2 is removed from the bonnet 4 by removing the mounting bolts and nuts 24, the annular protrusion 13 protrudes beyond the surrounding surface facing the bonnet 4, and the yoke-side back seat surface 14 is exposed to the outside.

[0032] The bonnet 4, like the yoke 2, has an elongated long-neck structure made of a low-temperature resistant metal material such as stainless steel, and this bonnet 4 prevents freezing of the ultra-low temperature fluid such as LNG or liquid hydrogen near the gland 20, making it possible to flow the ultra-low temperature fluid into the flow path 8 by opening and closing the valve body 7.

[0033] A stem insertion hole 30 is provided inside the bonnet 4, and a stem 6 is inserted into this stem insertion hole 30 so as to be movable up and down. When the stem 6 is moved up and down, a valve body 7 at the lower end of the stem 5 moves toward and away from a valve seat 31 formed inside the body 5, thereby opening and closing a flow path 8.

[0034] The inner diameter φd at the upper end of the stem insertion hole 30 is formed to be approximately the same as the outer diameter φD of the annular protrusion 13 so that they can fit together, and furthermore, an annular step 32 is formed on the outer periphery of the stem insertion hole 30 with an expanded diameter, into which the annular protrusion 15 of the yoke 2 fits. A flange 33 connectable to the flange 10 is formed on the outer periphery of the annular step 32.

[0035] The annular protrusion 15 and the annular step 32 are provided so that their radial widths are the same, and when the annular protrusion 13 is inserted into the stem insertion hole 30, Annular protrusion 13 The side surfaces of the annular protrusion 15 and the side surfaces of the annular step portion 32, and the horizontal surfaces of the annular protrusion 15 and the annular step portion 32 face each other, forming a space surrounded on all four sides by these surfaces, and this space constitutes the gasket chamber 38.

[0036] In this way, when the yoke 2 is attached to the bonnet 4, a gasket chamber 38 is formed between the annular protrusion 15 and the annular step 32 when the annular protrusion 13 is fitted into the stem insertion hole 30, and with the gasket 16 attached to this gasket chamber 38, the tip side of the annular protrusion 15 is fitted into the annular step 32. Next, by tightening the flange portions 10 and 33 with the mounting bolts and nuts 24, the gasket 16 is sandwiched between the underside of the yoke 2 and the top side of the bonnet 4. In this way, the yoke 2 is attached to the top of the bonnet 4 in a centered state, with the yoke 2 and bonnet 4 sealed together by the gasket 16.

[0037] In Figure 3, when the height from the top surface of the annular step 32 to the bottom surface of the annular protrusion 15 is L1, the height of the portion of the stem insertion hole 30 formed by the inner diameter φd is L2, and the height from the top surface of the flange 33 to the bottom surface of the flange 10 is L3, height L1 < height L2 is set so that when the gasket 16 is housed in the gasket chamber 38 and press-fitted, the bottom surface of the annular protrusion 15 and the top surface of the annular step 32 are prevented from coming into contact before the gasket 16 is completely crushed, and the gasket 16 can be installed in an appropriate state without being damaged or broken.

[0038] Furthermore, by making height L1 equal to height L3, when gasket 16 is completely crushed, the bottom surface of flange portion 10 and the top surface of flange portion 33 come into metal contact, and even in the unlikely event that gasket 16 is lost from gasket chamber 38 due to burning or the like, this metal seal reliably prevents leakage.

[0039] As shown in Figures 1 and 3, a flange portion 34 for connection with the body 5 attached to the lower part of the bonnet 4 is formed at the lower part of the bonnet 4, and the bonnet 4 is fixed to the upper part of the body 5 via this flange portion 34. An annular protrusion 35 is formed on the underside of the bonnet 4 so as to be substantially concentric with the stem insertion hole 30, and an annular ridge 36 is formed with an expanded diameter around the outer periphery of this annular protrusion 35, with the flange 34 provided so as to protrude outward from the annular ridge 36. An annular gasket 37 is provided on the side of the annular ridge 36 facing the body 5 so as to be attachable.

[0040] The body 5 is made of a low-temperature resistant metal material, similar to the yoke 2 and bonnet 4, and has the valve seat 31 formed in a direction intersecting the flow path 8 inside the body 5. An annular stepped portion 40 into which the annular protrusion 35 of the bonnet 4 is fitted is formed on the upper surface of the body 5, and an annular expanded diameter recess 41 into which the annular protrusion 36 is fitted is formed with an expanded diameter on the outer circumferential side of this annular stepped portion 40. Furthermore, a flange portion 42 connectable to the flange portion 34 is formed so as to protrude outward from the outer circumferential side of the annular expanded diameter recess 41.

[0041] When the bonnet 4 is attached to the body 5, the annular protrusion 35 is fitted into the annular stepped portion 40, and the leading end of the annular protrusion 36 is fitted into the annular expanded diameter recess 41 with a gasket 37 attached to the opposing surface between the annular protrusion 36 and the annular expanded diameter recess 41. Next, in this embodiment, the flanges 34 and 42 are fastened together with six sets of fastening bolts and nuts 43, thereby sandwiching the gasket 37 between the underside of the bonnet 4 and the upper side of the body 5. In this way, the bonnet 4 is attached to the upper part of the body 5 in a centered state with the bonnet 4 and the body 5 sealed together by the gasket 37.

[0042] The stem 6 is made of a metal material such as stainless steel, and a tapered stem-side backseat surface 50 is formed midway along the stem 6, the diameter of which decreases as it approaches the yoke 2. The stem-side backseat surface 50 is formed in a tapered shape so that a portion or all of it can abut and seal against the yoke-side backseat surface 14 described above. In this case, the stem-side backseat surface 50 is formed so that the inclination angle θ1 of the yoke-side backseat surface 14 from the axis P of the stem 6 is slightly larger than the inclination angle θ2 of the stem-side backseat surface 50 from the axis P of the stem 6. In other words, the inclination angle θ2 of the stem-side backseat surface 50 in this embodiment is set to an angle slightly smaller than the inclination angle θ1 of the yoke-side backseat surface 14, which is 30°.

[0043] The yoke-side back seat surface 14 and the stem-side back seat surface 50 are both formed with high edge quality, and burrs are removed by appropriate processing. Furthermore, a narrowed constricted portion 51 is formed at the boundary position of the upper part of the stem-side back seat surface 50. By providing this constricted portion 51, there is more space to move a cutting tool or the like when processing the stem-side back seat surface 50 on the stem 6, and this stem-side back seat surface 50 can be formed with higher edge quality.

[0044] An operating handle 53 is attached to the stem 6, and the stem 6 can be raised and lowered by rotating the handle 53. The fully open position of the valve element 7 does not change with the operation of the handle 53, and the yoke-side back seat surface 14 and the stem-side back seat surface 50 are in metal-to-metal contact at a fixed reference position. This reference position for metal-to-metal contact is set so as not to be affected by increases or decreases in the dimensions of each part due to temperature changes.

[0045] By operating the handle 53, the valve body 7 is fully opened, and when the stem 6 is lifted to its maximum when the valve body 7 is fully opened, the yoke side back seat surface 14 and the stem side back seat surface 50 come into contact and seal, thereby forming the back seat mechanism 52.

[0046] Although the valve body 1 in the above embodiment is a gate valve, the present invention is not limited to gate valves and can be applied to valves of various structures, such as globe valves, needle valves, and plug valves, as long as the valve body opens and closes a flow path by raising and lowering the valve element and has a back seat mechanism consisting of a back seat surface on the yoke side and a back seat surface on the stem side.

[0047] The inclination angles θ1 and θ2 of the yoke-side back seat surface 14 and the stem-side back seat surface 50 from the axis P of the stem 6 can be set at any angle, as long as the back seat mechanism 52 can be formed by the contact seals of both of these.

[0048] The annular protrusion 36 on the bottom of the bonnet 4 and the annular expanded recess 41 on the top of the body 5 may be omitted. In this case, only the annular protrusion 35 and the annular stepped portion 40 may be formed on the bonnet 4 and the body 5, respectively, and the bonnet 4 and the body 5 may be connected by fitting these together with the gasket 37 sandwiched between the flange portions 34 and 42.

[0049] Four sets of mounting bolts and nuts 24 and six sets of fixing bolts and nuts 43 are used to fasten the yoke 2 to the bonnet 4, and the bonnet 4 to the body 5, respectively, but the number of sets of bolts and nuts may be changed as appropriate depending on various specifications such as the diameter of each flange portion of the valve body 1 and the size of the valve body 1.

[0050] Next, the operation of the valve of the present invention in the above embodiment will be described. 1 to 3 , as described above, the valve body 1 of the present invention has a flange connection structure in which the bonnet 4 and yoke 2 are connected by flanges 10, 33. With the sealing packing 3 housed within the yoke 2, the annular protrusion 13 on the yoke 2 is fitted into the stem insertion hole 30 on the bonnet 4, enabling accurate centering of the yoke 2 and the upper part of the bonnet 4. When assembling the valve body 1, the packing 3 attached to the yoke 2 is centered together with the yoke-side back seat surface 14, and the packing 3 allows the stem 6 to be centered relative to the yoke 2. Therefore, with the stem-side back seat surface 50 accurately centered with the yoke-side back seat surface 14, a back seat mechanism 52 can be configured at a high position on the valve body 1. This back seat mechanism 52 prevents fluid leakage from the flow path 8 toward the gland 20 when the valve is fully open, preventing damage to the packing 3 and external leakage of gasified fluid, thereby achieving excellent sealing.

[0051] In this case, when the valve element 7 is fully open, the stem-side back seat surface 50 abuts and seals against the yoke-side back seat surface 14 to provide the back seat mechanism 52, so that when the stem 6 is operated to reach the fully open state, the back seat mechanism 52 is automatically provided, thereby appropriately preventing the intrusion of fluid. Moreover, since the back seat mechanism 52 is provided at a position higher than the position at which the liquid fluid flowing inside the body 5 rises, there is no risk of the liquid fluid reaching the height of the back seat mechanism 52.

[0052] Furthermore, because the annular protrusion 35 on the bonnet 4 side is fitted into the annular stepped portion 40 on the body 5 side and centered, the yoke 2, bonnet 4, and body 5 can be integrated in a centered state. As a result, even if the bonnet 4 is formed long to comply with standards such as ISO standards (ISO28921-1) and the distance from the position of the valve disc 7 (flow path 8) to the handle 53 is set to a certain amount or more, the stem 6 can be accurately centered with the packing 3, the yoke-side back seat surface 14, and the upper part of the bonnet 4. The valve disc 7 at the lower end of the stem 6, which is centered with the yoke 2, can be accurately seated against the valve seat 31, demonstrating sealing performance when the valve is closed and reliably preventing leakage from the flow path 8.

[0053] A packing housing 12 is provided in the stem through-hole 11 of the yoke 2, and a yoke-side back seat surface 14 is provided on the inner periphery of the opening of the annular protrusion 13 of the yoke 2. This allows the packing 3 housed in the packing housing 12 and the yoke-side back seat surface 14 to be close to each other, thereby minimizing the volume of the cavity between them. This makes it possible to minimize the expansion of the fluid.

[0054] The yoke 2 is detachably mounted on the bonnet 4, and when removed, the annular protrusion 13 protrudes beyond the surrounding surface facing the bonnet 4, exposing the yoke-side backseat surface 14 to the outside. Therefore, when forming the yoke 2, the yoke-side backseat surface 14 can be easily and precisely formed by surface machining or other processing while viewing it directly from the outside, eliminating the need for complex processing such as backing plate machining. Simply removing the yoke 2 from the bonnet 4 exposes the yoke-side backseat surface 14, making repairs and maintenance of the yoke-side backseat surface 14 easy.

[0055] In addition, the packing 3 can be replaced, the gland 20 can be retightened, and internal maintenance can be performed at will. When replacing the packing 3, the gland nut 23 is loosened, the gland bolt 17 is removed from the gland retainer 21, and the gland retainer 21 and the gland 20 are removed, allowing the packing 3 to be easily attached and detached.

[0056] Since the yoke-side back seat surface 14 on the yoke 2 and the stem-side back seat surface 50 on the stem 6 can be directly formed by processing means such as surface processing, an increase in the number of parts can be suppressed and assembly is also easy.

[0057] The gasket 16 is accommodated in the gasket chamber 38 defined between the annular protrusion 15 and the annular step 32 by the step between them. Therefore, the volume of the gasket chamber 38 can be set as desired by adjusting the tightening of the mounting bolts and nuts 24, and the filling rate of the gasket 16 in the gasket chamber 38 can be adjusted within a suitable range.

[0058] When the back seat mechanism 52 performs back sealing, a force from the stem-side back seat surface 50 is applied to the annular protrusion 13 to expand it. In this case, the outer peripheral surface of the annular protrusion 13 comes into contact with the inner peripheral surface at the top end of the stem insertion hole 30, and the outer peripheral surface of the annular protrusion 15 comes into contact with the inner peripheral surface of the annular step 32, respectively, and these two locations support the force acting in the radial expansion direction on the annular protrusion 13. This prevents deformation of the annular protrusion 13 in the radial expansion direction, maintains a sealed contact state between the stem-side back seat surface 50 and the yoke-side back seat surface 14, and reliably prevents fluid intrusion.

[0059] The above describes in detail the embodiments of the present invention, but the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the spirit of the invention described in the claims of the present invention. [Explanation of symbols]

[0060] 1 Valve body 2 York 3. Packing 4. Bonnet 5 Body 6 Stem 7 Valve body 8 Flow path 11 Stem through hole 13 Annular protrusion 14 Yoke side back sheet surface 15 Annular protrusion 16 Gasket 30 Stem insertion hole 32 Annular step 35 Annular protrusion 40 Annular stepped portion 50 Stem side back seat surface 52 Back seat mechanism θ1: Inclination angle of the back seat surface on the yoke side from the stem axis θ2: Inclination angle of the stem side back seat surface from the stem axial direction

Claims

1. A stem is mounted on the upper part of a bonnet having a long neck structure so as to be movable up and down, with a yoke having a sealing packing storage section attached thereto, and a flow path in the body is opened and closed by a valve body provided at the lower end of the stem, and an annular protrusion protruding toward the bonnet is formed around the bonnet-side opening of a stem through-hole provided in the yoke, and this annular protrusion is formed so as to be able to fit into the stem insertion hole provided on the bonnet side, and a tapered yoke-side back seat surface whose diameter increases as it approaches the bonnet is provided on the inner periphery of the opening of the annular protrusion, and a tapered stem-side back seat surface whose diameter decreases as it approaches the yoke is provided midway on the stem, and a back seat mechanism that abuts and seals with the yoke-side back seat surface and the stem-side back seat surface when the stem is fully lifted up, a gasket chamber surrounded on all sides by opposing surfaces of the annular protrusion and the annular step provided on the outer periphery of the annular protrusion and the annular step provided on the outer periphery opening side of the stem insertion hole, a gasket disposed on the outer periphery of the annular protrusion, a gasket sandwiched between the underside of the yoke and the upper side of the bonnet, and mounted in the gasket chamber while being disposed between the side surface of the outer periphery of the tip of the annular protrusion and the side surface of the annular step, and the yoke is attached to the bonnet.

2. 2. The valve according to claim 1, wherein the yoke is detachably attached to the bonnet, and when the yoke is removed from the bonnet, the annular protrusion protrudes beyond the surrounding surface facing the bonnet, and the yoke-side back seat surface is exposed.

3. A valve as described in claim 1 or 2, in which an annular protrusion provided on the underside of the bonnet is fitted into an annular stepped portion provided on the upper side of the body, and the bonnet is attached to the body in a centered state.

4. A valve as described in claim 1, wherein the inclination angle of the yoke side back seat surface from the axial direction of the stem is formed slightly larger than the inclination angle of the stem side back seat surface from the axial direction of the stem.

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