Packing for high-pressure valves

Abstract

The valve bonnet defines a packing box having an interior surface roughness average (Ra) of 0.15 or less, e.g., 0.10 to 0.15. A plurality of polytetrafluoroethylene (PTFE) packing rings reside within the packing stack. Packers are bolted to the bonnet and extend into the packing box. The packers are configured to apply packing pressures to the packing, e.g., 100 megapascals (MPa) to 200 MPa. Such a configuration may enable high-pressure valves, e.g., valves capable of holding pressures up to 10,000 pounds per square inch (PSI) or up to 15,000 PSI.

Description

[Technical Field]

[0001] The present disclosure relates to packing for high pressure valves. [Background technology]

[0002] In oil and gas processing, valves are often used to direct and regulate fluids through conduits within the plant. The valve itself includes an outer housing that defines an internal flow path. Within the valve are valve internals that regulate flow within the flow path. Some valves include a valve stem that extends from the valve internals through the valve housing to the external environment. The valve stem can be used to manipulate the valve internals, for example, by an operator or actuator. As the stem penetrates the valve housing that holds the fluid, a seal, or packing, surrounds the stem to prevent or reduce leakage from the flow path along the stem to the external environment. Summary of the Invention

[0003] The present disclosure provides a high-pressure valve having the following features: The valve bonnet defines a packing box having an inner surface roughness average (Ra) of 0.15 or less, e.g., 0.10 to 0.15. In some embodiments, the valve stem extending through the valve bonnet into the valve body defines an outer surface having an Ra of 0.15 or less. A plurality of polytetrafluoroethylene (PTFE) packing rings are located within the packing stack. Packers are bolted to the bonnet and extend into the packing box. The packers are configured to apply packing pressures (i.e., stresses) to the packing, e.g., 100 megapascals (MPa) to 200 MPa. Such a configuration may enable a high-pressure valve, e.g., a valve capable of holding 10,000 pounds per square inch (PSI) pressure or 15,000 PSI (68.95 gigapascals or 103.42 gigapascals).

[0004] In some embodiments, the valve can further include an anti-extrusion ring within the packing stack. In such embodiments, the anti-extrusion ring comprises a material harder than PTFE, for example, carbon such as graphite, and / or Inconel. Generally, in embodiments having anti-extrusion rings, the anti-extrusion rings are located at both ends of the packing stack.

[0005] In some embodiments, the valve further includes a valve body attached to the valve bonnet, for example, by bolts or similar fasteners. A metal gasket may be between the valve bonnet and the valve body. In some embodiments, the metal gasket defines a substantially T-shaped profile. In some embodiments, the metal gasket may include a self-energizing and / or pressure-energizing metal gasket.

[0006] An example of the subject matter described within this disclosure is a method having the following features: A valve packing including a PTFE packing ring is provided; The provided valve packing is inserted into a packing box; The packing box has an inner surface roughness of 0.15 or less, e.g., 0.10 to 0.15, Roughness Average (Ra); A packing pressure of 100 megapascals (MPa) to 200 MPa is applied to the valve packing by a packer.

[0007] In some embodiments, anti-extrusion rings may be provided and inserted into the packing box along with the PTFE packing ring. In such embodiments, the anti-extrusion rings may be placed on either side of the PTFE packing ring before the valve packing is inserted into the packing box.

[0008] In operation, the packing box is attached to the valve and pressure is maintained within the valve by the valve packing, for example, a pressure of 10,000 PSI or 15,000 PSI (68.95 Giga Pascals or 103.42 Giga Pascals) can be maintained. [Brief explanation of the drawings]

[0009] These and other features will be readily understood from a reading of the following detailed description taken in conjunction with the accompanying drawings. [Figure 1] FIG. 1 is a cross-sectional side view of an exemplary valve. [Figure 2] FIG. 2 is a cross-sectional side view of the packing box of the exemplary valve shown in FIG. 1. [Figure 3] 2 is a cross-sectional side view of the interface between the valve body and the valve bonnet of the exemplary valve shown in FIG. 1. FIG. [Figure 4] FIG. 1 is a flow diagram of an exemplary method that may be used according to aspects of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Certain embodiments will now be described to provide a general understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods explicitly described herein and illustrated in the accompanying drawings are non-limiting embodiments, and that features illustrated or described in connection with one embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be within the scope of the present invention.

[0011] Furthermore, in this disclosure, like-named components of embodiments generally have similar characteristics, and therefore, every feature of each like-named component within a particular embodiment is not necessarily described in full detail. Additionally, to the extent that linear or circular dimensions are used in describing the disclosed systems, devices, and methods, such dimensions are not intended to limit the types of shapes that may be used with such systems, devices, and methods. Those skilled in the art will recognize that the equivalents of such linear and circular dimensions can be readily determined for any geometric shape. The size and shape of the systems and devices and their components may depend, at least, on the anatomical structure of the subject with whom the systems and devices are to be used, the size and shape of the components with which the systems and devices are to be used, and the method and procedure with which the systems and devices are to be used.

[0012] High-pressure valves, for example, valves rated to handle internal pressures of 10,000 pounds per square inch (PSI) (68.95 gigapascals) or greater, are difficult to manufacture due to limitations on the materials and geometries that can be used for such operating conditions. These difficulties extend to selecting packing materials around the valve stem, also called a packing stack, to prevent or reduce leakage around the valve stem. This disclosure describes packing stacks made from standard materials and packing boxes that can be used together in high-pressure valve applications.

[0013] A cross-sectional view of such a high-pressure valve 100 is shown in FIG. 1. In the context of this disclosure, a high-pressure valve is a valve capable of holding a pressure of at least 10,000 pounds per square inch (68.95 gigapascals), e.g., 15,000 pounds per square inch (103.42 gigapascals). The valve includes a valve body 102 defining a primary flow path 104 for a working fluid. The valve body can be constructed as a single, integral piece, for example, by casting, forging, or additive manufacturing. In some embodiments, the primary flow path 104 can be formed in the valve body by conventional machining. Alternatively or additionally, portions of the valve body 102, such as the flange 106, may be welded, brazed, or otherwise attached to the valve body 102. An upper portion of the valve body 102 defines a cavity disposed to receive a valve internal 108, e.g., a valve plunger or cage. Different valve internals 108 may be used depending on the type of valve, for example, a gate valve may accept a gate and stem, a ball valve may accept a ball, a globe valve may accept a plunger and stem, etc.

[0014] A valve bonnet 110 rests on the valve body 102. The valve bonnet 110 defines a central passage 112 through which a valve stem 114 extends from an upper end of the valve bonnet 110, through the valve bonnet 110, and to the valve internals 108. The valve stem 114 exchanges actuation force between the valve internals 108 and an external actuator or operator. The upper end of the central passage 112 defines a packing box 116. The packing box 116 includes a seal 118 to prevent fluid from exiting the primary flow path 104 within the valve body 102. Further details regarding the seal 118 are provided throughout this disclosure. In the illustrated embodiment, the bonnet 110 is attached to the valve body by a threaded stud 120 and a nut 122. Other attachment mechanisms, such as bolts or clamps, may be used without departing from this disclosure. In some embodiments, a gasket 124 is included between the valve bonnet 110 and the valve body.

[0015] The packing box 116 is shown in detail in FIG. 2. As previously mentioned, the packing box 116 itself is defined by the bonnet 110. The inner surface 202 of the packing box 116, particularly the surface parallel to the valve stem 114, has a roughness average (Ra) of 0.15 or less, e.g., 0.10. In contrast, a typical packing box has an Ra of substantially 3.2 (±5%). In some cases, additional machining can be used to achieve such a smooth inner surface 202 after the packing box 116 is formed. Within the packing box 116 is a seal 118, or packing stack 204, that surrounds the stem 114 and seals (e.g., partially or completely seals) the annulus defined by the outer surface of the stem 114 and the inner surface 202 of the packing box 116.

[0016] Packing stack 204 includes packing rings 205. In some embodiments, packing rings 205 include polytetrafluoroethylene (PTFE) packing rings 205. While virgin PTFE can be used for packing rings 205, in some embodiments, PTFE reinforced with carbon (e.g., carbon braid) or other fibers can be used without departing from this disclosure. In some embodiments, anti-extrusion rings 206 are included within packing stack 204, more specifically, at both ends of packing stack 204. These anti-extrusion rings 206 are made of a harder material than packing rings 205; for example, in some embodiments, anti-extrusion rings 206 can include carbon and / or Inconel. In some embodiments, carbon can include graphite. In some embodiments, the overall height of anti-extrusion rings 206 is substantially half (within 10%) of the overall height of packing rings 205. In some embodiments, the overall height of anti-extrusion rings 206 is greater than half the overall height of packing rings 205. In some embodiments, the height of each anti-extrusion ring is equal to or greater than half the height of an individual packing ring 205. In other words, in some embodiments, each anti-extrusion ring 206 is at least half the height of one packing ring 205. In some embodiments, the packing stack defines reduced control gaps to further reduce the leakage rate through the packing stack 204. In some embodiments, the clearance at various control gaps 212 is reduced compared to standard (low-pressure) valves. Such gaps 212 are between the stem 114 and the bonnet 110, between the guide bushing 214 at the bottom of the packing box 116 and the stem 114, between the packer 208 and the stem 114, and between the packer 208 and the bonnet 110.

[0017] Packer 208 is attached to the upper end of bonnet 110, for example, by bolts or studs 210, and extends partially into packing box 116 to abut the upper end of packing stack 204. Packer 208 is configured to apply a packing pressure (i.e., stress) to packing stack 204. Such pressure can be adjusted by bolts or studs 210; for example, the desired packing pressure can be proportional to the torque of the bolts or nuts on studs 210. In some embodiments, the packing pressure is set between 100 megapascals (MPa) and 200 MPa. In some embodiments, such load can be applied and / or adjusted while the valve is pressurized with fluid. Packer 208 can be tightened with or without a live load. Note that such high packing pressures have been used with PTFE packing rings by applicant, even though such PTFE rings are not rated for such packing pressures. For example, PTFE rings are typically rated for packing pressures of substantially 30 MPa in such applications. However, applicants have tested configurations described herein that include high packing pressures and found that leakage through the packing can be less than 1.78 x 10^-4 mbar liters per second per millimeter of stem diameter under static and dynamic conditions. Such testing was performed using helium.

[0018] Moving the valve further down, FIG. 3 illustrates the interface between the valve body 102 and the valve bonnet 110. As previously mentioned, in some embodiments, the bonnet 110 is attached to the body 102 by studs 120. Between the body 102 and the bonnet 110, a gasket may be compressed, for example, by tension within the studs 120. Various gasket profiles, such as the substantially T-shaped profile shown in FIG. 3, can be used without departing from this disclosure. Such gasket profiles are commonly used in high-pressure applications. However, other self-energizing gaskets can be used without departing from this disclosure. In some embodiments, the gasket provides a leak rate of 50 ppm or less.

[0019] 4 is a flow diagram of an exemplary method 400 that may be used according to aspects of the present disclosure. At 402, a valve packing 204 is provided that includes a PTFE packing ring 205. In some embodiments, an anti-extrusion ring 206 is provided with the PTFE packing ring 205.

[0020] At 404, the provided valve packing ring 205 is inserted into the packing box 116. The packing box 116 can include an inner surface having a roughness average (Ra) of 0.15 or less, e.g., 0.10 Ra. In embodiments in which an anti-extrusion ring 206 is also provided, the anti-extrusion ring 206 is also inserted into the packing box 116; for example, the anti-extrusion rings 206 can be placed on either side of the PTFE ring 205 before inserting the valve packing into the packing box 116.

[0021] At 406, a pressure of 100 MPa to 200 MPa is applied to the valve packing 204 by the packer 208. During operation, the pressure is maintained within the valve at least in part by the packing. In some embodiments, the pressure maintained within the valve is up to 10,000 PSI (68.95 gigapascals). In some embodiments, the pressure maintained within the valve is up to 15,000 PSI (103.42 gigapascals).

[0022] While this disclosure includes details of many specific embodiments, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features unique to particular inventions. Certain features described in this disclosure in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as working in a particular combination and initially claimed as such, one or more features from a claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0023] Similarly, although operations are depicted in the figures in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown, or in any sequential order, or that all of the illustrated operations be performed, to achieve desirable results. Furthermore, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described components and systems may generally be integrated together in a single product or packaged in multiple products.

[0024] Thus, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results.

Claims

1. A high-pressure valve, a valve bonnet defining a packing box having an interior surface roughness average (Ra) of 0.15 or less; a plurality of polytetrafluoroethylene (PTFE) packing rings in a packing stack; a packer bolted to the bonnet and extending into the packing box, the packer configured to apply a packing pressure to the packing, the packing pressure being between 100 megapascals (MPa) and 200 MPa.

2. 10. The high pressure valve of claim 1, further comprising an anti-extrusion ring within the packing stack.

3. 3. The high-pressure valve of claim 2, wherein the anti-extrusion ring comprises a material harder than PTFE.

4. 3. The high pressure valve of claim 2, wherein the anti-extrusion rings are at opposite ends of the packing stack.

5. a valve body attached to the valve bonnet; a valve stem extending through the valve bonnet and into the valve body, the valve stem defining an outer surface having an Ra of 0.15 or less; 10. The high-pressure valve of claim 1, further comprising a metal gasket between the valve bonnet and the valve body.

6. The high-pressure valve of claim 5 , wherein the metal gasket comprises a substantially T-shaped profile.

7. 6. The high pressure valve of claim 5, configured to hold a pressure of 10,000 pounds per square inch.

8. A high-pressure valve, a valve bonnet defining a packing box having an interior surface roughness average (Ra) of 0.10 to 0.15; a plurality of polytetrafluoroethylene (PTFE) packing rings in a packing stack; a packer bolted to the bonnet and extending into the packing box and configured to apply pressure to the packing; A valve body; a valve stem extending through the valve bonnet and into the valve body, the valve stem defining an outer surface having an Ra of 0.15 or less; a metal gasket between the valve bonnet and the valve body, A high pressure valve configured to hold a pressure of at least 10,000 pounds per square inch.

9. 9. The high-pressure valve according to claim 8, wherein the packing pressure is between 100 megapascals (MPa) and 200 MPa.

10. 9. The high pressure valve of claim 8, further comprising an anti-extrusion ring within the packing stack.

11. 11. The high pressure valve of claim 10, wherein the anti-extrusion ring comprises carbon and inconel.

12. 11. The high pressure valve of claim 10, wherein the anti-extrusion rings are at opposite ends of the packing stack.

13. 9. The high pressure valve of claim 8, wherein the metal gasket comprises a self-energizing or pressure-energizing gasket.

14. 9. The high pressure valve of claim 8, configured to hold a pressure of 15,000 pounds per square inch.

15. 1. A method comprising: providing a valve packing including a packing ring of polytetrafluoroethylene (PTFE); inserting the provided valve packing into a packing box having an inner surface roughness of 0.15 or less Roughness Average (Ra); applying 100 megapascals (MPa) to 200 MPa to the valve packing with a packer.

16. 16. The method of claim 15, wherein a valve stem extends through the valve, the valve stem defining an outer surface having an Ra of 0.15 or less.

17. The packing box is attached to a valve, and the method comprises:

16. The method of claim 15, further comprising maintaining pressure within the valve with the valve packing.

18. 18. The method of claim 17, wherein the pressure is 10,000 PSI.

19. Providing an anti-extrusion ring; 16. The method of claim 15, further comprising inserting the anti-extrusion ring into the packing box.

20. 20. The method of claim 19, further comprising placing anti-extrusion rings on either side of the PTFE packing ring before inserting the valve packing into the packing box.

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