JPH0210313B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A valve using the stem seal device of the present invention is a high pressure, high temperature, balanced rise stem gate valve similar to the invention disclosed in the following US patent application: i.e. September 1977
Patent No. 833,684 filed by David Pea. ” and Patent No. 697,084, filed by Charles Day Morrill on June 16, 1976, “High-temperature, high-load, preloaded, solid-lubricating, metal-to-metal interstem seals with preloaded laminates; High pressure, balanced rising stem gate valve.

The stem seal device of this invention is related to the stem seal device disclosed in the aforementioned US Pat. No. 697,084.

Said applications are assigned to the applicant of this invention and their disclosures are incorporated herein by reference.
This technique is utilized in this invention.

In the oil and gas industry, pressure and temperature gradually increase as the hole gets deeper during drilling, and in sour gas fields, the fluid exiting the well contains a relatively high proportion of hydrogen sulfide ( _H2S ). . Seals for valves and wellheads used in oil fields have recently been developed, but these seals are relatively resistant to deterioration due to the interaction of high pressure and high temperature, and are also less susceptible to corrosive fluids such as H ₂ S. It is resistant to

Morrill patent number registered on November 1, 1977
No. 4056272, which is filed by the same applicant as Application No. 697084 and assigned to the right holder of this invention, the disclosure content of which is also adopted in this invention. That is, a static seal between the wellhead and the pipe hanger. This seal consists of a pair of conical metal ring gaskets,
Its cross-sectional shape is approximately rectangular. The metal ring gasket is compressed by a locking screw and a compression ring, and the ends of the gasket are plastically deformed and engage the parallel cylindrical walls of the well head and pipe hanger to create a metal-to-metal seal. It can be tightened up to. The initial cross-sectional shape of the deformable ring used in such static seals is trapezoidal, and is made of Teflon, poly, urethane,
Made of rubber, etc. The ring is disposed between the metal ring gaskets and is pressed against the metal ring gaskets to create a rectangular cross-sectional shape and engage the walls of the well head and pipe hanger. The deformable ring used in this static seal can be used to back up the metal ring gasket if the seal is imperfect, for example if there are scratches or machine marks on the well head or pipe hanger. Acts as a seal. This deformable ring penetrates and seals these scratches and machine marks.

The seal used for dynamic or static sealing between the valve stem and the valve body or bonnet is a retractable frustoconical metal ring gasket with a rectangular cross-sectional shape. This metal ring gasket is disposed within a packing box provided around the stem, and a ring made of a more easily deformable material is sandwiched between the gaskets. Although the metal ring gasket is made of soft wood rather than spring steel, it has a similar elasticity to Belleville springs for two reasons. First, when the gasket is not pressed, the inner diameter of the gasket should be made larger and the outer diameter smaller, so that the seal unit can be held against the packing box without causing excessive friction with the valve stem or packing box. This is to allow easy attachment and detachment. Second
When using a valve, if the temperature or pressure changes,
This is to maintain the compressive engagement between the gasket and the stem or packing box even if the gasket initially becomes deformed or distorted when the packing retainer is tightened, and even if the dimensions of the valve change somewhat. . In other words, the gasket must be stretchable to sustain the pre-applied load.

Said valve stem seal is disclosed in said Application No. 697084.
and in the ASME paper "Seals for Valve Stems and Wellheads for Use at High Pressures and Temperatures" by C.D. Morrill and C.D. Mayer. The latter was prepared for presentation at an academic conference in Mexico City, Mexico, from September 19th to 24th, 1976, and its contents are also used in this invention. A threaded retainer is fastened to the seal disclosed in this invention to compress and flatten the metal ring gasket. In this case, the inner and outer edges of the metal ring gasket are deformed and come into contact and engagement with the outer surface of the valve stem and the wall of the packing box to provide a metal-to-metal seal. The clamping ring sandwiched between the metal ring gaskets is also deformed by compression against the seal and engages the stem and packing box according to the shape of the metal ring gasket. The ring sandwiched between the metal ring gaskets must have some elasticity. Due to initial deformation, the snapping ring is usually set in place while retaining some elasticity. Materials for forming the clamping ring in such seals include fluororesin,
For example, tetrafluoroethylene polymer and graphite. Such materials also include tetrafluoroethylene polymers containing up to about 15% molybdenum disulfide.

The clamping ring used in the valve stem seal is a dynamic seal, which acts to dynamically seal between the metal ring gasket and the stem if the metal ring gasket becomes malfunctioning due to the sliding movement of the stem. It has the following. Such clamping rings also tend to wear to some extent through contact with the stem and lubricate the area of contact between the stem and the metal ring gasket, reducing the friction between the stem and the metal ring gasket. let The clamping ring further provides lubrication between the stem and the clamping ring and between the clamping ring and the metal ring gasket.
Reduce friction. The clamping ring also acts as a backup seal for the metal ring gasket.
This is similar to the back-up seal using a deformable ring for sealing between the well head and pipe hanger in US Pat. No. 4,056,272, and seals by penetrating scratches and mechanical marks on the stem. It is.

The present invention relates to an improvement of the above-mentioned valve stem seal.

The stem seal has three metal ring gaskets with two clamping rings disposed between them. This is known as an SMT type seal. This SMT type seal has an operating pressure of up to 25000 psi (1750 Kg/cm ² ) and an operating temperature of -20
It is designed to provide a sufficient stem seal for valves with temperatures between 0 and 300 degrees Celsius (-29 to 149 degrees Celsius).

However, the operating pressure is 30000psi (2100Kg/
cm ² ) and above, SMT-type seals cannot always provide sufficient valve stem sealing. For example, a material consisting solely of graphite is unsuitable for SMT-type stem seals for valves with operating pressures of 30,000 psi (2,100 Kg/cm ² ). This is because graphite material is
This is because when the gasket is pressed flat and sealed, it tends to be pushed past the metal ring gasket. This is because the graphite is forced out before the gasket is sufficiently flat to form a seal between the valve stem and the packing box. In addition, graphite tends to be worn away or eroded by the operation of the valve stem, which causes the graphite to be deposited on the stem and carried by the stem past the gasket and outside the packing box. This is because they are carried away. When used at operating pressures of 30,000 psi (2,100 Kg/cm ² ), the graphite is extruded and worn due to the reasons mentioned above, causing fluid to leak from the seal and requiring replacement of the graphite clamping ring. occurs.

Similarly, a material consisting only of tetrafluoroethylene polymer (TFE) or M ₀ S ₂
Materials with added
cm ² ) is not suitable for SMT type stem seals of valves used at high pressures. This is because such materials cannot maintain a constant hermetic seal against such high pressures when the valve is subjected to temperature cycling. Valves used in oil fields include
Because high-pressure fluid flows out from a deep well, the valve is heated to approximately 300㎓ (149℃) by this fluid.
It is overheated to the point of When the flow of fluid to the valve stops, such as by shutting down a well, the temperature of the valve cools down to room temperature, approximately 70°C (21°C), but when the well is restarted, the fluid starts flowing again. Initially, the temperature of the bulb rises to 300〓 (149℃) again. Therefore, the valve temperature is about 70〓 to about 300℃.
〓Varies between 21 and 149℃. Within the temperature range at which the valve will be used, the valve stem seal must be able to remain airtight at all times and no matter how temperature cycled. Added TFE ring or M ₀ S ₂
SMT type seals using TFE rings are approximately
At an operating pressure of 30000psi (2100Kg/cm ² ), approximately 70
It has a sealing effect against fluids at room temperature (21℃) and high temperature of 300℃ (149℃), but
When a valve is subjected to a temperature cycle in which the temperature is raised from room temperature to 300㎓ (149℃) and then returned to room temperature, the SMT type seal cannot maintain airtightness at all times. Additionally, a small amount of leakage may occur from the seal when the valve stem is in motion or at rest. Retightening the pack retainer can stop the leak, but temperature cycling causes it to leak again.

The purpose of this invention is to operate at an operating pressure of 30000 psi (2100 psi).
Kg/cm ² ) used in order or more, -20
The object of the present invention is to solve this problem by providing a reliable valve stem seal suitable for valves that are subjected to temperature cycling in the temperature range from -29 to 149°C. Another object of this invention is that when a fluid having a pressure of 30,000 psi (2100 Kg/cm ² ) or more is applied, or the valve is subjected to temperature cycles such as from room temperature to about 300㎓ (149°C) and back to room temperature. The object of the present invention is to provide a seal that is airtight and leak-proof without having to retighten the seal retainer. Still another object of the invention is to provide a simple, compact,
To provide a seal that is inexpensive and easy to manufacture, install, and handle. Still another object of the invention is to provide a seal that is highly wear resistant, durable, relatively resistant to degradation due to high temperatures, temperature changes and high pressures, and chemically stable to the fluids to which it is applied. It is in.

The high pressure, balanced rise stem gate valve of the present invention provides a seal between the valve body bonnet and the valve operating stem, and between the valve body chamber and the balance stem using a metal-to-metal interconnect using a stretchable material. It is a stem seal device. Each sealing device has at least one seal set consisting of a pair of frustoconical, stretchable metal ring gaskets, with a lubricating material such as tetrafluoroethylene polymer between each metal ring gasket. Two assembly rings made of a tall, strong, stretchable material are provided, one assembly ring contacting one metal ring gasket and the other assembly ring contacting the other metal ring gasket. Contact. A core ring is arranged between these two assembly rings. The coefficient of body expansion of this core ring due to heating is smaller than the coefficient of expansion of an assembly ring formed of dense graphite or the like. The inner diameter of the core ring is larger than the inner diameter of the assembly ring. A bearing ring is disposed along the inner circumference of the core ring between the core ring and the operating or balance stem of the valve. The bearing ring is made of the same type of material as the assembly ring, such as tetrafluoroethylene polymer. Each seal set is disposed within an annular packing box. This packing box is adjacent to the valve body,
It is provided to extend around the stem. Each packing box is closed by an annular packing retainer threaded into its interior, pressing against a frustoconical metal ring gasket. Thus, the inner and outer edges of each metal ring gasket engage the stem and packing box, respectively. In this case, sufficient pressure is applied to the concave inner circumferential edge and convex outer circumferential edge of the metal ring gasket, causing plastic deformation. The clamping layer consisting of the core ring and the bearing ring arranged between the assembly rings deforms to conform to the shape of the space formed between the pressed metal ring gaskets and fills substantially the entire space. The volume of the core ring is approximately 1/3 of the volume of the entire clamping layer. Even if the valve is operated and temperature cycles are applied,
Maintains tightness without retightening the retainer.
A preloaded state can be maintained. The valve stem seal set of the present invention can also be used to completely pack the locking screw so that the moving parts are sealed during and after operation, even when subjected to temperature cycling.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a valve having a hollow body in which a chamber 21 and a bonnet 23 are connected to a stud 25 and a nut 27.
It is fixed by Bonnet 23 and chamber 21
A gasket 29 for maintaining appropriate pressure is used to seal the gap between the two. Pedestals 31, 33 attached to the inner ends of the passages 35, 37 cooperate with a pair of opening/closing gates 39, 41 to adjust the flow rate of fluid such as water, oil or gas passing through the valves. The sealant is stored in the storage parts 43, 45, and is delivered to the interface between the opening/closing gates 39, 41 and the pedestals 31, 33 and the pedestal 3 through the passages 47, 49 for distributing the sealant.
1 and 33 and is automatically supplied to the interface between the neck and the valve body to seal these interfaces.

The opening/closing gates 39, 41 are reciprocated between a closed position and an open position by a substantially cylindrical operating stem 51. Although the closed position is shown in Figure 1,
In this position, fluid cannot flow through passages 35,37. On the other hand, in the open position, gate port 5
3, 55 are ports 57, 59 in the pedestals 31, 33
, the fluid flows through passages 35, 37. The upper end of the operating stem 51 extends outwardly from the chamber 21 and passes through a port 61 formed in the bonnet 23. The sealing member 63 of this invention is attached to the operating stem 51.
and a substantially cylindrical packing box 65 formed inside the bonnet 23. This sealing member 63 is press-fitted into the packing box 65 by a packing retainer 67. This Patsukin retainer 6
7 is screwed into a neck 69 formed in the upper part of the bonnet 23 and having an internal thread. Bleeder port 71 is used to check for fluid leakage between working stem 51 and port 61 after working stem 51 is seated rearward.

A screw is also cut on the outside of the neck 69 of the bonnet 23, and the bearing retainer 73 can be screwed into this screw. Threaded upper part 77 of operating stem 51
An operating nut 75 is screwed into the. A flange 79 is formed on the operating nut 75, and thrust bearings 81 and 83 are coaxially disposed above and below the flange 79.
Thrust bearing 8 disposed below flange 79
3 engages with the upper part of the washer 85 disposed on the upper part of the seal retainer 67. The thrust bearing 81 disposed above the flange 79 is attached to the bearing retainer 73.
engages with the inside of the upper end. A non-circular hole 89 is formed in the handwheel 87.
is aligned with a corresponding non-circular portion 91 formed on the operating nut 75. hand wheel 8
7 is held in place by a retainer nut 93 threaded onto the upper end of operating nut 75. The bleeder port 95 is for allowing fluid to escape between the threaded top of the operating stem 51 and the operating nut 75.

A substantially cylindrical balance stem 97 is connected to the lower ends of the opening/closing gates 39 and 41 and extends to the outside of the valve chamber 21 through the port 99. A seal member 101 of the present invention provides a seal between the balance stem 97 and a substantially cylindrical packing box 103 formed within the valve body. This sealing member 101 is press-fitted into the packing box by a packing retainer 105 provided below.
This packing retainer 105 is screwed into a threaded socket 107 formed coaxially with the port 99 and the packing box 103. balance stem 9
7 is securely seated in the annular pedestal formed around port 99 in the valve body, any fluid leakage between this balance stem 97 and port 99 will occur at bleeder port 109. Checked by. A cap 111 is fixed to the valve body with a screw 113, and the cap 111 allows the seal retainer 105,
That is, the lower end of the balance stem 97 is covered.

When the handwheel 87 is turned, the operating nut 75
is rotated, and the operating stem 51 is operated. When the operating stem 51 operates, the opening/closing gates 39 and 41 connected to the operating stem 51 through the hub 115
moves up and down. As the opening/closing gates 39, 41 move up and down, the opening/closing gates 39, 41 are moved by the hub 117.
A balance stem 97 connected to 41 moves up and down. Therefore, the operating stem 51 and the balance stem 9
7 are respective corresponding seal members 63, 10
1, it moves in the axial direction. In this case, the seal members 63, 101 need to be reliably held during and before and after the movement of each stem 51, 97 in the axial direction.

Since the seal members 63 and 101 are the same, it is sufficient to explain only one of them in detail.
Referring to FIGS. 2A and 2B, seal member 63 consists of an upper seal set 119 and a lower seal set 121. Lower matching ring 123
is disposed at the bottom of the annular packing box 65 and located below the lower seal set. The lower surface of the lower matching ring 123 is in contact with the bottom surface of the packing box 65, and the two are complementary to each other. A compliant ring 125 is disposed between the bottom surface 127 of the packing retainer 67 and the upper seal set 119. The upper end surface of the secondary conforming ring 125 is in contact with the bottom surface 127 of the packing retainer 67, and has a correlation. An intermediate matching ring 129 is disposed between the upper seal set 119 and the lower seal set 121.
Upper surface of lower matching ring 123, secondary matching ring 12
5 and both upper and lower surfaces of the intermediate fitting ring 129 are truncated conical shapes, and the angle of the cone is set to match the shape of the upper and lower seal sets 119, 121 in the final assembly position. To explain this point, FIG. 2B shows the seal member of the present invention installed in the valve, but before the seal retainer 67 is tightened to hold the seal member. On the other hand, in FIG. 2A, the seal retainer 67 is fastened to the threaded neck 69 to hold the seal member, and each seal set 119, 121 and each matching ring 123, 1 are attached.
25 and 129 are in the final assembly position. As detailed below, each seal set 119,
The metal ring gasket 131 of 121 has a conical shape that is sharper than the surface of each matching ring. That is, the angle of the cone of the metal ring gasket 131 is smaller in the untightened state of FIG. 2B than in the final fastened position of FIG. 2A. In some cases, either one or both of the lower matching ring 123 and the secondary matching ring 125 may be omitted, but in this case, the bottom surface of the packing box 65 or the bottom surface of the packing retainer 67 is held at a predetermined angle and at a predetermined angle. It needs to be in the shape of a truncated cone with a face. Compatible ring 12
When using 3,125,129, these
It is sufficient that the valve body and bonnet 23 be made of conventional high pressure valve steel, although they must be made of a fairly hard material such as 4140 steel.

Since the upper and lower seal sets 119 and 121 are the same, it is sufficient to describe only one of them in detail. The construction of the seal set 119 is such that two identical assembly rings 133 are disposed between a pair of frustoconical metal ring gaskets 131. The assembly ring 133 is made of a solid lubricant material that is strong, flexible, and has a lower elastic modulus than the metal ring gasket 131. One of the assembly rings 133 is disposed adjacent to one of the metal ring gaskets 131 and the other assembly ring 133 is disposed adjacent to the other metal ring gasket 131.

A core ring 135 is disposed between assembly rings 133. The coefficient of thermal expansion of the core ring 135 is smaller than that of the assembly ring 133. The inner diameter of the core ring 135 is the same as that of the assembly ring 13.
It is larger than the inner diameter of 3. A bearing ring 137 is disposed between the core ring 135 and the operating stem 51 and extends around the inner circumference of the core ring 135 . The bearing ring 137 is made of a strong, flexible, solid lubricant material similar to the material used to form the assembly ring 133. bearing ring 1
37 slips into a hole formed in core ring 135.

The cross-sectional shape of the metal ring gasket 131 is approximately rectangular before being tightened, and is inclined at an angle of about 30° with respect to the horizontal plane. Therefore,
Before being tightened, the conical angle of the metal ring gasket 131 is approximately 120°.
In addition, before the metal ring gasket 131 is tightened, a gap is formed between the operating stem 51 and the packing box 65 and the peripheral edge of the metal ring gasket 131, so there is a gap inside the valve. When installing the metal ring gasket 131, the operating stem 51 and the packing box 65 will not be damaged. Metal ring gasket 131
can be set in place by simply dropping it. When the seal retainer 67 is tightened and the seal member is tightened,
Each metal ring gasket 131 is pressed so that their inner diameter is significantly reduced while their outer diameter is significantly increased. Therefore, the concave inner peripheral edge and the convex outer peripheral edge of each metal ring gasket 131 are deformed. That is, each metal ring gasket 13
1 is plastically deformed and engages with the operating stem 51 and the packing box 65, respectively, thereby creating a metal-to-metal seal. The metal ring gasket 131 should be made of a softer metal than the working stem 51 so that the working stem 51 does not become worn or damaged. For example, the operating stem is K
K Monel alloy can be used, but any suitable steel may also be used. The surface of the operating stem 51 is coated with 3 to 5 mils (7.6×10 ^-3 to 12.7×10 ^-3 cm) of hard coating such as tungsten carbide.
It is desirable to increase the hardness of the surface of the operating stem 51 and increase its durability. By applying such a coating, the hardness of the working stem 51 is increased by about 30 to about 60 Rockwell hardness. Since the metal ring gasket 131 has sufficient plasticity, it can be sealed between metals by applying high stress and deforming the peripheral edge, and has sufficient strength, so it can withstand high preload applied. and can withstand the fluid pressure flowing out of the well. For example, this metal ring gasket 131 is No.
Made of annealed stainless steel (austenitic stainless steel) such as 316 stainless steel, or other metals such as carbon steel or alloy steel. In order to further reduce wear and damage to the operating stem 51, when rounding the concave inner circumferential edge of each metal ring gasket, the radius of the concave inner edge of each metal ring gasket 131
It is desirable that the thickness be approximately half of the thickness of the
For example, if the thickness of the metal ring gasket 131 is
If it is 0.04 inch (1.0 mm), it is best to round the inner edge to a radius of 0.02 inch (0.5 mm). Since the metal ring gasket 131 forms an angle of about 15° with respect to the horizontal in the tightened state, its cone angle is about 150°. On the other hand, the compatible ring 12
The truncated cone surface of 3,125,129 is also approximately
It is placed at an angle of 15°. Therefore, each metal ring gasket 131 is connected to each matching ring 123, 12.
Compatible with 5,129 truncated conical surfaces. By the way, although the metal ring gasket 131 is preferably shaped like a truncated cone, it goes without saying that it may be shaped like a truncated cone at a different angle.

The materials for assembly ring 133 and bearing ring 137 must have a low coefficient of friction. In other words, the material needs to have high lubricity. The materials for assembly ring 133 and bearing ring 137 must also be strong and durable enough to maintain integrity under high pressure, yet be chemically stable to the fluid controlled by the valve. together with the expected temperature during valve operation,
For example, it is required to withstand temperatures of 300°C to -20°C (149°C to -29°C). Such materials must have sufficient elasticity or plasticity and must be able to penetrate into minute gaps. The gap referred to here is a gap formed between the metal ring gasket 131, the operating stem 51, and the packing box 65, and is caused by scratches or mechanical marks formed on the operating stem 51 and the packing box 65. , or during and after operation of the operating stem 51, the metal ring gasket 131 and the operating stem 5
This is a gap created when the new surface of 1 and 1 are adjacent to each other. The latter gap is caused by the fact that, for example, during and after the operation of the operating stem 51, the inner peripheral edge of each metal ring gasket 131 is simultaneously and constantly plastically deformed and does not fit into the newly adjacent operating stem surface. This occurs because there is no such thing. Assembly ring 133 and bearing ring 137
penetrates into the minute gaps mentioned above and exerts a sealing effect. Therefore, this assembly ring 133 and bearing ring 137 can be considered as a seal ring. The material for the assembly ring 133 and the bearing ring 137 is "Teflon".
Alternatively, a tetrafluoroethylene polymer such as that commercially available under the trade name "Moly-Teflon" is suitable. Here, Molyteflon is similar to Teflon but contains up to 15% molybdenum disulfide (M ₀ S ₂ ), among which 5% M ₀ S ₂ and 95% by weight. 2021 from Allied Chemical Company is the most suitable.
It is sold as.

The material for the core ring 135 is the assembly ring 13.
3 and the bearing ring 137, it is required to have strength that can withstand the high preload required for sealing, and is chemically stable to the fluid sealed by this core ring 135.
and the temperature expected during valve operation, e.g.
It is required to be able to withstand temperatures of 300° to -75° (149 to -59°C).

Another feature of the core ring 135 is revealed by applicants' findings that may cause leakage when SMT type seals are used under high pressure and severe temperature changes. However, it should be understood that the seal disclosed here is not a theoretical solution to the problem of leakage.

Rings formed from TFE or TFE with M ₀ S ₂ were temperature cycled to 30000 psi (2100 psi).
When applying pressures in the range of Kg/cm ² ), it is clear that the leakage observed in SMT type stem seals is due to a partial loss of the preload applied to the seal. A comparison can be made with the loss of preload applied to pure elastomer packings disclosed in the ASME paper cited above. When constructing an SMT type seal, tightening the packing retainer applies mechanical pressure to the seal, which is greater than the pressure exerted by the high pressure fluid. When a valve with an SMT-type stem seal is heated from room temperature to 300°C (149°C), the TFE ring expands, but not to a large extent. This is because these rings are surrounded on almost all sides by metal, which has a slower expansion rate than these rings. Therefore, the preload force applied to the seal becomes higher than the original pressure, that is, the pressure before heating. Once the valve has cooled down to room temperature,
The prepressure not only decreases from the pressure raised by the heating of the valve, but also becomes less than the original pressure. This is due to one or both of the following effects. When the bulb is heated to approximately 300℃ (149℃), the ring formed of TFE expands thermally.
The pressure applied to the seal and the surrounding metal increases, creating a higher preload and causing deformation or sagging of the surrounding metal, so that when the seal cools back to room temperature, the volume occupied by the seal increases. The pressure on the seal is now less than the original preload. In addition, when thermal expansion occurs by heating the valve to 300 °C (149 °C) and the pressure applied to the TFE ring increases, the TFE ring undergoes a permanent deformation that is larger than the deformation caused by the preload. It will undergo even greater compression deformation. This deformation does not reverse even when the valve cools to room temperature, so the pressure on the TFE ring is reduced and the seal retainer offsets the pressure to some extent. Therefore, after being subjected to temperature cycling, it is necessary to retighten the packing retainer to obtain the appropriate preload. If this retightening is not done, this valve will not exceed 30,000 psi.
(2100Kg/cm ² ) When used at pressures on the order of 2100Kg/cm 2 , leakage occurs at the seal.

In this invention, TFE and
Instead of TFE added with M ₀ S ₂ , a material with a smaller expansion coefficient when heated than TFE or TFE added with M ₀ S ₂ is used. In a preferred embodiment of the invention, such a material with a low expansion coefficient is used for the core ring 135, and three sides of the core ring 135 are connected to the metal ring gasket 1 through the assembly ring 133 and the bearing ring 137.
31 and adjacent to the operating stem 51. Therefore, the coefficient of thermal expansion of the core ring 135 is equal to that of the assembled ring 1.
33 and bearing ring 137. A suitable material for the core ring 135 is dense graphite, which is commercially available under the trade name "Grafoil." Reference may be made in this regard to US Pat. No. 3,404,061. Although the exact numerical value is unknown, for example, the thermal expansion coefficient of TFE is said to be several times larger than that of graph oil. However, official data shows that the coefficient of linear expansion of graphite produced as a thin stretchable layered sheet or ribbon is parallel to the graphite layer, i.e. in the longitudinal direction for sheets and in the width direction for ribbons. Regarding the direction, 70〓
Approximately -0.02× in the range of 2000 to 2000〓 (21 to 1093℃)
10 ^-5 in/in〓(−0.04×10 ^-5 cm/cm℃),
70〓 to 4000〓 (21 to
1.5×10 ^-5 in/in〓(2.7×
10 ^-5 cm/cm℃). The coefficient of linear expansion of TFE is 78
7.0 to 500 (26 to 260℃)
10.0×10 ^-5 in/in〓 (12.6 to 18.0×10 ^-5 cm/cm℃)
It is. In the case of a solid, the coefficient of body expansion is approximately 3 times the coefficient of linear expansion.
It's double. For more on this, see The Handbook.
The Handbook of Chemistry and Physics
48th edition, page F-90 (Chemical Rubber Company, 1967). Now, even if we assume that the coefficient of thermal expansion of graph oil is three times as large as the coefficient of linear expansion, its coefficient of thermal expansion is approximately 78〓 to 300〓.
It is less than 1/4 of the coefficient of expansion of TFE in the temperature range of 〓(26~149℃).

The layer of rings clamped between the metal ring gaskets (hereinafter referred to as the clamping layer) is the core ring 13.
5, a bearing ring 137 disposed along the inner circumference of the core ring 135, and an assembly ring 133 disposed adjacent to the upper and lower surfaces of the core ring 135 and the bearing ring 137, and a metal ring gasket. When the metal ring gasket 131 is pressed and held, it deforms according to the shape of the space formed between the metal ring gaskets 131, filling almost the entire space. The original cross-sectional shape of the ring of the clamping layer is rectangular, but
It may be deformed to fit the truncated conical shape shown on the right side of FIG. 2 before being installed in the bulb. Its shape corresponds to the truncated conical surface of the matching rings 123, 125, 129, and the matching ring 12
3,125,129 has metal ring gasket 1
31 is pressed. Further, the original cross-sectional shape of the clamping layer ring upon installation is rectangular, and is transformed into a truncated conical shape by forming the seal.

The material for forming the pressure relief core ring 135 is a graphoil ribbon that is tightly compressed and wound into a rigid, seamless ring. Such ribbons are commercially available from Union Carbide Corporation under the name Graphoil Ribbon Pack, and are manufactured by Union Carbide Corporation.
It is described in Corporation Technical Report No. 524-204, a copy of which is attached as an appendix to this product. A tightly wrapped ring of Graphoil ribbon pack exhibits a high coefficient of thermal expansion in the radial direction when placed around the working stem in the packing box, ie, in the direction of the working stem and the packing box. In addition, the core ring 135 is
It may be formed by cutting sheets of graph oil, or it may be formed by stacking sheets. Commercially available graph oil is compressed to about 70% to make it dense, but 100% or complete compression can be done before installation as mentioned above, or it can be installed inside the valve and then form a seal. It may be compressed by

Assembly ring 133 is thinner than core ring 135 and bearing ring 137. This assembly ring 13
3 has approximately the same thickness when the core ring 135 is sufficiently compressed, but its radial width is wider than either the core ring 135 or the bearing ring 137. The radial width of the core ring 135 plus the radial width of the bearing ring 137 is:
It is approximately equal to the radial width of the assembly ring 133.
If a clamping layer is installed inside the valve, assembly ring 1
33 and bearing ring 137 form a slidable interference fit. When this clamping layer is pressed by forming a seal, the inner circumferential edges of the assembly ring 133 and the bearing ring 137 are pressed against the operating stem 51 and the assembly ring 133
The outer peripheral edge of the core ring 135 is tightly engaged with the wall surface of the packing box 65.

Although two seal sets 119, 121 are shown, it is the applicant's belief that a single seal set may be sufficient to provide a sufficient sealing effect. In other words, the second seal set is
Install it as far away as possible from the fluid to be sealed.
This is for emergency or backup use in case the first seal set is damaged. Another feature of the emergency or backup seal is that a passageway 139 is formed in the bonnet 23. This passageway 139 coincides with the passageway 141 formed in the intermediate matching ring 129 to form a flow path when the seal is formed. Passage 139 also communicates with an injection fitting 140 located in a threaded socket located on the exterior of bonnet 23.
An annular groove 143 communicating with the passage 139 is formed in the wall of the packing box 65, and an annular groove 145 communicating with the passage 141 is formed in the inner end of the intermediate fitting ring 129. If the seal sets 119, 121 are damaged, the seal material will be removed from the injection fitting 140.
and the annular groove 14 through the passages 139 and 141.
3 and 145 to form an emergency or backup seal around the packing box 65 and the operating stem, respectively.

The sealing device of this invention has a packing retainer 67.
A preload is applied by tightening.
The pressure in this case is greater than the pressure exerted by the fluid when the valve is actuated. The valve shown in Figure 1, i.e. rated operating pressure 30000psi
(2100 Kg/ ^cm2 ) The prestress applied to the valve stem seal is approximately 37500 psi (2625 Kg/ ^cm2 ).

The valve having the stem seal device of the present invention can be used for 70〓
There is no need to retighten the Patsukin retainer even if it is heated from room temperature (about 21 degrees Celsius) to about 300 degrees Celsius (149 degrees Celsius) and then cooled down to room temperature again. Therefore, the initial preload applied to the valve is maintained during temperature cycling. This is due to the following facts. That is, the pressure created by thermal expansion of the clamping layer between the metal ring gaskets 131, i.e., the initially applied pressure, is not sufficient to permanently deform the metal-enclosed portion of the valve adjacent to the seal. This is because the coefficient of thermal expansion of the core ring 135 is smaller than that of the assembly ring 133 and the bearing ring 137. For similar reasons, the pressure applied by heating is low, so assembly ring 133 and bearing ring 137
does not undergo any further permanent deformation, ie compressive strain, and the preload is not lost even if the rings 133, 137 loosen due to cooling.

According to the applicant, the stem seal device of the present invention can be applied to a fluid of 30,000 psi (2,100 Kg/cm ² ) with a temperature cycle of -20 to 300 degrees (-29 to 149 degrees Celsius) and the seal retainer remains intact. It is said that it can withstand use without having to be retightened. In this case, the assembly ring 133 and the bearing ring 137 are made of TFE with 5% M ₀ S ₂ added, and the core ring 135
is made of graph oil, and the core ring 135
The volume is approximately 1/3 of the volume of the entire clamping layer.
Therefore, in this preferred embodiment, the combined volume of assembly ring 133 and bearing ring 137 is approximately twice the volume of core ring 135. Assembly ring 1
The material forming the Graphoil core ring 13 is not forced out of the metal ring gasket 131 by the formation of the seal, but rather the material forming the Graphoil core ring 13 is disposed between the assembled rings 133 during the formation of the seal.
5, the core ring 13
5 is prevented from being pushed out beyond the metal ring gasket 131. In addition, a bearing ring 1 made of TFE containing 5% M ₀ S ₂ is arranged along the inner circumference of a core ring 135 made of Graph Oil.
37 relieves friction between the operating stem 51 and the stem seal device, and the core ring 135
prevent excessive wear. Therefore, the core ring 135 made of graph oil has a small coefficient of thermal expansion, and its three sides are the assembled ring 13 made of TFE containing 5% M ₀ S ₂ .
3 and the operating stem 5 through the bearing ring 137
1 and metal ring gasket 131 are in contact with each other. In this case, in the clamping layer of the present invention, it is desirable that the volume of the core ring 135 be approximately 1/2 of the total volume of the assembly ring 133 and the bearing ring 137. Of course, the volume ratio of the ring of this clamping layer may be changed, and the material of the ring may also be changed.

In Figures 1, 2A and 2B,
The conical shapes of the metal ring gasket 131 and the ring of the clamping layer are in the opposite direction to the direction of sealing pressure, but the surfaces of the inner and outer peripheral edges of the sealing part are parallel and the engagement state is the same. For example, the seal portion may be reversed. Therefore, the conical shape of each ring of the metal ring gasket 131 and the clamping layer can be oriented in the same direction as the pressure of the fluid being sealed. In addition, the assembly ring 133 and the bearing ring 13
It will also be understood that 7 does not necessarily need to be formed separately. For example, a groove may be integrally formed along the center of the outer periphery of a cylindrical ring, and the member may have a U-shaped cross section. In this case, align the core ring within that groove and then
Installed inside the valve.

Although a preferred embodiment of the invention has been described, numerous modifications may be made by those skilled in the art without departing from the spirit of the invention. Therefore, it goes without saying that what is disclosed herein is for illustrative purposes only and is not intended to limit the scope of the invention. The scope of the invention is indicated in the claims.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of the valve of the present invention, Fig. 2A
Figures 1 and 2B illustrate one embodiment of the operative stem sealing device of the present invention in which the frustoconical metal ring gasket is oriented opposite the pressure being sealed against the inside of the valve. Fig. 2B is a partially enlarged cross-sectional view of the stem seal device of the present invention before the seal retainer is installed in the valve, and Fig. 2A is a partially enlarged cross-sectional view of the stem seal device of the present invention on the same plane. FIG. 3 is a partially enlarged sectional view of the stem seal device after it has been removed. 51...Operating stem, 61...Port, 63,
101... Seal member, 65, 103... Packing box, 67, 105... Packing retainer, 131
...Metal ring gasket, 133... Assembly ring, 135... Core ring, 137... Bearing ring.

Claims (1)

[Claims] 1. The valve has a port below the packing box, and an operating stem movable in the axial direction of the valve extends through the port to the outside of the packing box, and is operated under high pressure and temperature cycling. A sealing device is used to seal between a wall surface of the operating stem and a packing box installed around the operating stem, the sealing device being a sealing device installed in the packing box installed around the operating stem. The gasket comprises first and second metal ring gaskets, and a deformable annular sealing member clamped between the metal ring gaskets in the packing box, and the sealing member is connected to the metal ring gaskets. Adjacent first and second
and a core portion disposed between the annular portions, the annular portion being formed of a strong, deformable material, and the core portion having a coefficient of thermal expansion greater than that of the material forming the annular portion. A sealing device characterized in that it is formed of a small material. 2. The sealing device according to claim 1, wherein the material forming the first and second annular portions has a small coefficient of friction. 3. The sealing device according to claim 2, wherein the first and second annular portions are made of tetrafluoroethylene polymer, and the core portion is made of dense graphite. 4. The sealing device of claim 3, wherein the material forming the first and second annular portions contains up to about 15% molybdenum disulfide. 5. A core ring in which the first and second annular portions are comprised of assembly rings that engage and seal with the operating stem and the packing box, and the core portion has an inner diameter larger than an outer diameter of the operating stem. further comprising a bearing ring disposed along the inner circumference of the core ring between the core ring and the working stem and formed of a durable deformable material. The sealing device according to item 4. 6. The sealing device according to claim 5, wherein the bearing ring is made of the same material as the assembly ring. 7. The core ring and the bearing ring fill almost all of the space formed in the axial direction between the assembly rings and the space formed in the radial direction between the operating stem and the packing box. 7. A sealing device according to claim 6, characterized in that: 8. The sealing device according to claim 7, wherein the volume of the core ring is approximately 1/2 of the total volume of the assembly ring and the bearing ring. 9. Claim 1, characterized in that the coefficient of thermal expansion of the material forming the core portion is smaller than 1/4 of the coefficient of thermal expansion of the material forming the first and second annular portions. sealing device. 10 The metal ring gasket further includes a member for pressing the first and second metal ring gaskets, whereby the metal ring gasket is partially flattened and its inner and outer peripheral edges are deformed to A patent characterized in that the operating stem and the packing box are engaged and sealed, and the first and second annular portions of the sealing member are engaged and sealed with the operating stem and the packing box. A sealing device according to claim 1. 11. The outer peripheral edge of the annular core portion is adjacent to the packing box, and the inner diameter of the core portion is larger than the outer diameter of the stem, and the sealing member has a third annular portion, and the annular portion 11. The sealing device of claim 10, wherein: is formed of a durable, deformable material and is disposed between the core portion and the stem. 12. The seal according to claim 11, wherein the first, second, and third annular portions are made of tetrafluoroethylene polymer, and the core portion is made of dense graphite. Device. 13 The first, second and third annular portions are formed of a material consisting of 95% tetrafluoroethylene polymer and 5% molybdenum disulfide, the core portion is formed of dense graphite, and the metal ring gas When the gasket is compressed, substantially the entire space formed between the metal ring gasket, the operating stem and the packing box is occupied by the first, second and third annular portions and the core portion, and 12. The sealing device according to claim 11, wherein the volume of the core portion is approximately 1/3 of the total volume of the space.