초록 ▼

Combined metal-to-metal/compliant material stem sealing means for high pressure, balanced, rising stem gate valve includes at least one seal set at each of the actuator and balance stems. Each seal set comprises a pair of frustoconical metal ring gaskets between which are disposed two make-up rings

Combined metal-to-metal/compliant material stem sealing means for high pressure, balanced, rising stem gate valve includes at least one seal set at each of the actuator and balance stems. Each seal set comprises a pair of frustoconical metal ring gaskets between which are disposed two make-up rings of compliant, tough material of high lubricity, e.g. tetrafluoroethylene polymer. One make-up ring is adjacent to one gasket, and the other make-up ring is adjacent to the other gasket. A core ring of material that expands substantially less volumetrically upon heating than the make-up rings, e.g. compacted graphite, is disposed between the make-up rings. Around the inner periphery of the core ring adjacent the respective actuator or balance stem is disposed a bearing ring of material like that used for the make-up rings, e.g. tetrafluoroethylene polymer. The seal set is compressed by a packing retainer such that the metal gaskets are coined into metal-to-metal sealing engagement with the stems and adjacent valve body parts. The sandwich stack, consisting of the core ring and bearing ring disposed between the make-up rings, is deformed to conform to the shape of, and fills substantially all of the space between, the compressed metal ring gaskets. The volume of the core ring is approximately one-third of the total volume of the sandwich stack.

대표청구항 ▼

1. Apparatus for sealing in high pressure, temperature cycled applications between the walls of an axially movable valve stem and a stuffing box around the valve stem, the stuffing box having a port in its bottom and the valve stem extending through the port and out of the stuffing box, such sealing

1. Apparatus for sealing in high pressure, temperature cycled applications between the walls of an axially movable valve stem and a stuffing box around the valve stem, the stuffing box having a port in its bottom and the valve stem extending through the port and out of the stuffing box, such sealing apparatus being preloaded to a stress higher than the stress expected to be encountered in service, comprising: first and second elastic metal ring gaskets disposed in such stuffing box around such valve stem, each gasket being compressed into metal-to-metal sealing engagement with both of such walls, and annular compliant seal means disposed in such stuffing box around such valve stem and sandwiched between said gaskets, said seal means including first and second annular portions of tough, compliant material adjacent said first and second gaskets, respectively, each annular portion being compressed into sealing engagement with both of such walls, and a core portion disposed between said first and second portions and composed of a material having a lower coefficient of thermal expansion than said material of said first and second annular portions, the relative volume of said core portion with respect to said first and second annular portions being such that upon such temperature cycling, the thermal expansion of said annular compliant seal means is less than that which would cause loss of such preload stress. 2. Apparatus of claim 1, wherein said material of said first and second annular portions has a low coefficient of friction. 3. Apparatus of claim 2, wherein said material of said first and second annular portions comprises tetrafluoroethylene polymer, and said material of said core portion comprises compacted graphite. 4. Apparatus of claim 3, wherein said material of said first and second annular portions further comprises up to about fifteen percent molybdenum disulfide. 5. Apparatus for sealing in high pressure, temperature cycled applications between the walls of an axially movable valve stem and a stuffing box around the valve stem, the stuffing box having a port in its bottom and the valve stem extending through the port and out of the stuffing box, comprising: first and second elastic metal ring gaskets disposed in such stuffing box around such valve stem, and annular compliant seal means disposed in such stuffing box around such valve stem and sandwiched between said gaskets, said seal means including first and second annular portions of tough, compliant material having a low coefficient of friction comprising tetrafluoroethylene polymer with up to about fifteen percent molybdenum disulfide adjacent said first and second gaskets, respectively, and a core portion disposed between said first and second portions and composed of a material comprising compacted graphite having a lower coefficient of thermal expansion than said material of said first and second annular portions, said first and second annular portions comprising make-up rings in sealing engagement with such stem and such stuffing box and said core portion comprising a core ring having an inner diameter larger than the outer diameter of such stem, and further including a bearing ring of tough, compliant material disposed around the inner periphery of said core ring between said core ring and such stem. 6. Apparatus of claim 5, wherein said material of said bearing ring is the same as that of said make-up rings. 7. Apparatus of claim 6, wherein said core ring and said bearing ring together occupy substantially all of the space between said make-up rings, in the axial direction, and between such stem and such stuffing box, in the radial direction. 8. Apparatus of claim 7, wherein the volume of said core ring is about one-half the combined volumes of the make-up rings and bearing ring. 9. Apparatus of claim 1, wherein the coefficient of thermal expansion of said core portion material is less than one-fourth that of said material of said first and second annular portions. 10. Apparatus for sealing in high pressure, temperature cycled applications between the walls of an axially movable valve stem and a stuffing box around the valve stem, the stuffing box having a port in its bottom and the valve stem extending through the port and out of the stuffing box, comprising: first and second elastic metal ring gaskets disposed in such stuffing box around such valve stem, annular compliant seal means disposed in such stuffing box around such valve stem and sandwiched between said gaskets, said seal means including first and second annular portions of tough, compliant material adjacent said first and second gaskets, respectively, and a core portion disposed between said first and second portions and composed of a material having a lower coefficient of thermal expansion than said material of said first and second annular portions, and including means for compressing said first and second gaskets such that said gaskets are partially flattened and their inner and outer peripheral edges are coined into metal-to-metal sealing engagement with such stem and such stuffing box, and for urging said first and second annular portions of said seal means into sealing engagement with such stem and such stuffing box. 11. Apparatus for sealing in high pressure, temperature cycled applications between the walls of an axially movable valve stem and a stuffing box around the valve stem, the stuffing box having a port in its bottom and the valve stem extending through the port and out of the stuffing box, comprising: first and second elastic metal ring gaskets disposed in such stuffing box around such valve stem, annular compliant seal means disposed in such stuffing box around such valve stem and sandwiched between said gaskets, said seal means including first and second annular portions of tough, compliant material adjacent said first and second gaskets, respectively, and a core portion disposed between said first and second portions and composed of a material having a lower coefficient of thermal expansion than said material of said first and second annular portions, and means for compressing said first and second gaskets such that said gaskets are partially flattened and their inner and outer peripheral edges are coined into metal-to-metal sealing engagement with such stem and such stuffing box, and for urging said first and second annular portions of said seal means into sealing engagement with such stem and such stuffing box, said core portion being annular in configuration with its outer radial periphery adjacent such stuffing box and having an inner diameter greater than the outer diameter of such stem, said seal means including a third annular portion of tough, compliant material disposed between said core portion and such stem. 12. Apparatus of claim 11, said first, second and third annular portions being composed of tetrafluoroethylene polymer, and said core portion being composed of compacted graphite. 13. Apparatus of claim 11, said first, second and third annular portions being composed of a material consisting of ninety-five percent tetrafluoroethylene polymer and five percent molybdenum disulfide, said core portion being composed of compacted graphite, and wherein said first, second and third annular portions and said core portion occupy substantially all of the space between said metal ring gaskets, the stem and the stuffing box when said gaskets are compressed, said core portion having a volume equal to about one-third the total volume of said space. 14. Apparatus for sealing in extremely high pressure, temperature cycled applications between a fixed cylindrical wall and a cylindrical wall of a moving component for preventing fluid flow from the fluid side of the apparatus to the atmospheric side of the apparatus, such sealing apparatus being preloaded to a stress higher than the stress resulting from said extremely high pressure, comprising: first and second metal ring gaskets disposed between such fixed wall and such wall of such moving component, each gasket being compressed such that its peripheral edges are coined into metal-to-metal sealing engagement with both of such walls, and annular compliant seal means sandwiched between said gaskets, said seal means including first and second annular portions of compliant material adjacent said first and second gaskets, respectively, each annular portion being compressed into sealing engagement with both of such walls, and a core portion disposed between said first and second portions and composed of a material having a lower coefficient of thermal expansion than said material of said first and second annular portions, said core portion comprising means for limiting thermal expansion of said annular compliant seal means to an amount which maintains such preload on said sealing apparatus before, during, and after such temperature cycling. 15. Apparatus of claim 14, wherein said material of said first and second annular portions comprises tetrafluoroethylene polymer, and said material of said core portion comprises compacted graphite. 16. Apparatus for sealing in high pressure, temperature cycled applications between a fixed cylindrical wall and a cylindrical wall of a moving component for preventing fluid flow from the fluid side of the apparatus to the atmospheric side of the apparatus, comprising: first and second metal ring gaskets disposed between such fixed wall and such wall of such moving component, and annular compliant seal means sandwiched between said gaskets, said seal means including first and second portions of compliant material comprising tetrafluoroethylene polymer adjacent said first and second gaskets, respectively, and a core portion disposed between said first and second portions and composed of a material comprising compacted graphite having a lower coefficient of thermal expansion than said material of said first and second annular portions, said first and second annular portions comprising make-up rings in sealing engagement with such fixed wall and such wall of such moving component, said core portion being spaced from such wall of such moving component and there being included a bearing ring disposed in such space between said core portion and such wall of such moving component. 17. Apparatus of claim 16, wherein said bearing ring is composed of tetrafluoroethylene polymer. 18. Apparatus of claim 17, wherein said core portion and said bearing ring together occupy substantially all of the space between said make-up rings and between such fixed wall and such wall of such moving component. 19. Apparatus of claim 18, wherein the volume of said core portion is about one-half the combined volumes of the make-up rings and bearing ring. 20. Apparatus for sealing between a first cylindrical wall and a second cylindrical wall, the walls being substantially parallel to one another, in extremely high pressure, temperature cycled applications wherein such extremely high pressure is of the order of 30,000 psi or greater and the temperature to which such apparatus and walls are exposed is cycled from ambient temperature up to about 300° F. and back to ambient temperature, comprising: first and second metal ring gaskets disposed between such first and second walls for providing primary metal-to-metal seals therebetween against such extremely high pressure, and annular compliant seal means sandwiched between said gaskets for providing secondary seals between such walls, said seal means including first and second compliant make-up rings adjacent said first and second gaskets, respectively, and a core ring disposed between said make-up rings and composed of a material having a lower coefficient of thermal expansion than the material of which said make-up rings are made, the relative volume of said core ring as compared to said first and second make-up rings being predetermined such that upon such temperature cycling, said core ring comprises means for preventing loss of said primary and secondary seals resulting from thermal expansion of said annular compliant seal means.