SEAL FOR A FLUID ASSEMBLY

Abstract

A fluid assembly comprising a first part (28) and a second part (30) which interact by relative linear movement therebetween. A groove (40) extends around the circumference of the cylindrical interacting surface (36) of the first part (38) and a seal (50) is situated within the groove (40). The seal (50) has a radial face (64) which converts from a concave profile to a flat profile flush with the groove's root side (54) upon interface with the interacting surface (38) of the second part (30). The seal (50) also has axial faces (62) which each assume a more pronounced concave profile upon such interfacing, the concave profiles forming cavities (68) which, when filled with fluid, urge the radial seal face (64) and radial seal face (66) towards the groove's root side (54) and the interacting surface (38) of the second part (30).

Description

GENERAL FIELD

A seal for a fluid assembly comprising linearly interacting parts, wherein the seal is positioned within a groove in the cylindrical interacting surface of one of the parts.

BACKGROUND

In an offshore drilling operation, a drillstring extends from the rig platform into a wellbore whereat it drills deeper and deeper into the sea floor. The drillstring extends through a riser which reaches from the rig platform to the wellhead, usually with a subsea blowout prevention (BOP) stack between it and the ocean floor. During drilling, mud removed from the wellbore is drained to the surface through the riser, and well production fluid is transferred to the rig through choke lines. To stop a well flow, high density mud can be pumped from rig tanks into the wellbore by kill lines which extend from the platform to the seafloor.

The riser may be as long as several thousand feet, and may be made of successive riser pipes whose adjacent ends are connected/disconnected on the rig to raise/lower the riser. The choke lines, the kill lines, and/or other auxiliary lines (e.g., pneumatic/hydraulic equipment-control lines and/or logging lines) can be similarly made of a series of conduits connected/disconnected along with the riser pipes.

The connection between successive choke/kill conduits can be accomplished by male/female coupling members which interact by relative linear movement therebetween whereby a radially inner surface of the female member interfaces with a radially outer surface of the male member. To seal the male/female interface, a seal is typically placed in a groove in the radially inner interfacing surface of the female coupling member. The role played by choke and kill lines results in them being subjected to high pressures, both internal and external, and continuous exposure to seawater. To add insult to injury, choke and kill lines must endure long term cyclic fatigue loading (tension, compression, bending) which rise/fall in various load combinations depending upon the riser-mounting-relationship, sea conditions, production rates and other influencing factors. Needless to say, a seal residing in a choke line or a kill line does not live a sheltered life.

SUMMARY

A seal is provided, which can be constructed to withstand the abuse imposed by life in a choke line or a kill line in an offshore drilling operation, while still providing effective (if not superior) sealing performance. The seal provides multiple sealing points, most if not all of these points constituting exceptionally large bearing areas, even against groove sides and/or corners, thereby allowing the bridging of surface imperfections in deteriorated grooves. Opposing axial fluid cavities in the seal urge radial surfaces outward/inward to further energize the seal. While this seal will be especially appreciated in the connection of choke/kill lines, it will be equally welcomed in other fluid assemblies where a seal must tolerate high pressures, high temperatures, load cycling, frequent reciprocating movement, and/or other abusive conditions.

These and other features of the fluid assembly and/or the seal are fully described and particularly pointed out in the claims. The following description and annexed drawings set forth in detail certain illustrative embodiments, these embodiments being indicative of but a few of the various ways in which the principles of the invention may be employed.

DRAWINGS

FIG. 1 is a schematic diagram of an offshore drilling operation, the operation including a riser pipe and choke/kill lines attached thereto.

FIG. 2 is a close-up view of the riser pipe and the choke/kill lines.

FIG. 3 is a closer-up view of a male/female connection between conduits forming a choke or kill line, and a seal sealing the interface therebetween.

FIG. 4A is an even closer view of the seal, the seal being shown in an installed interfacing condition between the two interfacing surfaces of the male/female parts.

FIG. 4B is a plan view of the seal in a pre-installation condition.

FIGS. 4C-4E are similar to FIG. 4B, except that the seal has been modified to include a hard heel and/or an internal expander.

FIG. 5A is a close-up view of another form of the seal, the seal being shown in an installed interfacing condition between the interfacing surfaces of the male/female parts.

FIG. 5B is a plan view of the seal of FIG. 5A in a pre-installation condition.

FIGS. 5C-5E are similar to FIG. 5B, except that the seal has been modified to include a hard heel and/or an internal expander.

FIG. 6 is a partially-plan-partially-sectional view showing a piston-cylinder assembly wherein the seal is positioned in a groove in the cylinder head to seal its reciprocating interface with the rod.

FIG. 7 is a partially-plan-partially-sectional view showing a piston-cylinder assembly wherein the seal is positioned in a groove in the piston to seal its reciprocating interface with the cylinder.

DETAILED DESCRIPTION

Turning now to the drawings, and initially to FIG. 1, an offshore drilling operation 10 is schematically shown. In this operation 10, a drillstring 12 extends from the rig 14 into a wellbore whereat it drills deeper and deeper into the sea floor. The drillstring 12 extends through a riser 16 which reaches from the rig platform to the wellhead, usually with a subsea blowout prevention (BOP) stack 18 between it and the ocean floor. During drilling, mud removed from the wellbore is drained to the surface through the riser 16, and well production fluid is transferred to the rig through choke lines 20. To stop a well flow, high density mud can be pumped from rig tanks into the wellbore by kill lines 22 which extend from the platform to the seafloor.

Turning now to FIG. 2, a portion of the riser 16 and the choke/kill lines 20/22 are illustrated in more detail. As shown, the riser 16 comprises successive riser pipes 24-26, and the choke line 20 and the kill line 22 each comprise successive conduits 28-30. The first conduit 28 (or first part) has a female coupling member 32 and the second conduit 30 (or second part) has male coupling member 34. Although the choke line 20 and the kill line 22 are shown in the illustrated embodiment as being attached to the riser 16 (as is a common practice in offshore drilling), they could instead be independently raised/lowered from rig. Also, the first part 28 and the second part 30 could instead be part of an auxiliary fluid line used, for example, for equipment control or logging purposes. Additionally or alternatively, the riser pipes 24-26 could themselves constitute the first/second parts 28/30.

As is shown more clearly in FIG. 3, the female coupling member 32 of the first conduit 28 has a cylindrical interacting surface 36 which is a radially inner surface and the male coupling member 34 of the second conduit 30 has a cylindrical interfacing surface 38 which is a radially outer surface. The first conduit 28 and the second conduit 30 interact (e.g., connect) by relative linear movement between the respective interacting surfaces 36 and 38, and the interacting surfaces 36/38 interface with each other during such interaction. The female coupling member 32 includes a groove 40 which extends radially outward from its interacting surface 36 and a seal 50 is positioned within this groove 40.

The interfacing surfaces 36 and 38, the groove 40, and the seal 50 are shown even more clearly in FIG. 4A. The groove 40, which extends around the circumference of the interacting surface 36, has two axial sides 52, a radial root side 54 spanning the root-adjacent edges of the axial sides 52, and an open radial side spanning the interface-adjacent edges of the axial sides 52. The seal 50, which likewise extends around the circumference of the interacting surface, comprises two axial faces 62, a root-adjacent radial face 64, and an interface-adjacent radial face 66.

In FIG. 4A, the seal 50 is shown in an installed interfacing condition and thus has a corresponding installed interfacing shape. In FIG. 4B, the seal 50 is shown in a pre-installation condition and has a corresponding pre-installation shape. The seal 50 will be an installed pre-interfacing condition after it is installed in the groove 40 but prior to interfacing with the interacting surface 38 of the second part 30.

When the seal 50 is in its pre-installation shape (FIG. 4B), the axial seal faces 62 each have an axially concave profile and the root-adjacent seal face 64 has a radially concave profile. When the seal 50 is in its installed interfacing shape (FIG. 4A), the interacting surface 36 of the second part 30 compresses the seal 50 direction. This results in the seal's root-adjacent face 64 assuming a flat profile flush against the groove's root side 54. A substantial portion of the face 64 will contact a substantial portion of the groove side 54, though the corner regions of the seal 50 may not contact the groove side 54.

The radial compression also causes each of the axial seal faces 62 to assume a more pronounced concave profile forming a fluid cavity 68. When the fluid cavities 68 are filled with fluid, they push the seal face 64 towards the groove's root side 54 and push the seal face 66 toward the interacting surface 38 of the second part 30. Also, root-adjacent regions of the axial seal faces 62 will be urged against root-adjacent regions of the axial groove sides 52. Thus, contact (bearing) pressure is applied in at least four primary points: against the groove's root side 54, against the interacting surface 38 of the second part 30, and against the root-adjacent regions of each of the groove's axial sides 54. Such multi-point sealing allows bridging of surface imperfections allowing the seal 50 to be used in a groove that has deteriorated over service/time.

In the illustrated embodiment, the seal's interface-adjacent face 66 does not span the distance of the groove's open side 56 when in the seal 50 is in the installed interfacing shape. The subsequent gaps from a fluid passageway to the cavities 68. The seal 50 can be designed for about 10% to 20% radial squeeze and about 5% to 15% free groove space, as such a combination may generate sufficient potential rebound energy for effective sealing with many materials.

The seal 50 can be dimensioned so that, in the pre-interfacing installed condition, its is somewhat axially compressed (e.g., 5%) within the groove 40 and/or it is placed under hoop compression. Such a design can facilitate holding the seal 50 during transportation and handling. It may also provide enough contact pressure at multiple sealing points to prevent moisture and possible corrosion of the groove 40 during storage. Additionally, rebound of the seal 50 from its installed interfacing shape to its installed-but-not-interfacing shape can be such that seal faces 62 wipe or squeegee the groove sides 52 thereby preventing moisture (e.g., seawater) from becoming trapped within the groove 40.

As shown in FIGS. 4C-4E, the seal 50 can be equipped with hard heels 70 (FIG. 4C, FIG. 4E) and/or an internal expander 72 (FIG. 4D, FIG. 4E) to enhance seal performance. The heels 70 can serve as a backup for additional pressure containment and/or increase extrusion resistance. The expander 72 can help maximize radially squeeze and/or optimize reactive rebound.

Referring now to FIGS. 5A-5E, another form of the seal 50 is shown. In this seal, the concave profile of the root-adjacent seal face 64 is sharper and more triangular when the seal 50 is in its pre-installation condition (FIG. 5B). When the seal 50 is in the interfacing condition (FIG. 5A), this face has a flat profile flush against the groove's root side 54, and tightly engages its corner regions (although a center region) may be left uncontacted. Also, the seal's interface-adjacent face 60 fully occupies the groove's open side 54. The seal 50 may include a hard heel 70 (FIGS. 5C and 5E) and/or an internal expander 72 (FIG. 5D and FIG. 5E).

The seal 50 may be conventionally molded, extruded and cut, or otherwise formed of an elastomeric material which specifically may be selected for high temperature performance, flexibility, or otherwise for compatibility with the fluid being handled. Suitable materials, which may be filled, for example, with glass or carbon, or which may be unfilled, include natural rubbers such as Hevea and thermoplastic, i.e., melt-processible, or thermosetting, i.e., vulcanizable, synthetic rubbers such as fluoropolymer, chlorosulfonate, polybutadiene, butyl, neoprene, nitrile, polyisoprene, buna-N, copolymer rubbers such as ethylene-propylene (EPR), ethylene-propylene-diene monomer (EPDM), nitrile-butadiene (NBR) and styrene-butadiene (SBR), or blends such as ethylene or propylene-EPDM, EPR, or NBR. The term “synthetic rubbers” also should be understood to encompass materials which alternatively may be classified broadly as thermoplastic or thermosetting elastomers such as polyurethanes, silicones, fluorosilicones, styrene-isoprene-styrene (SIS), and styrene-butadiene-styrene (SBS), as well as other polymers which exhibit rubber-like properties such as plasticized nylons, polyolefins, polyesters, ethylene vinyl acetates, fluoropolymers, and polyvinyl chloride. As used herein, the term “elastomeric” is ascribed its conventional meaning of exhibiting rubber-like properties of compliancy, resiliency or compression deflection, low compression set, flexibility, and an ability to recover after deformation, i.e., stress relaxation. Non-elastomeric compounds that also may be possible candidates include graphite, peek, and a wide variety of other materials including composites.

As was indicated above, the fluid assembly which incorporates the groove 40 and the seal 50 may be a choke line 20, a kill line 22, riser 16 or any other fluid-conveying line in an offshore drilling operation or, for that matter, any suitable fluid-conveying system. Moreover, the fluid assembly need not include a conventional fluid-conveying system and/or a fluid connection in such a fluid-conveying system. The present groove/seal arrangement may find application in any fluid assembly wherein cylindrical surfaces interact by relative linear movement therebetween and a fluid seal is required in the interface between the interacting surfaces. For example, as shown in FIGS. 6 and 7, the fluid assembly incorporating the seal 50 and the seal 40 can comprise piston-cylinder assembly. Specifically, as shown in FIG. 6, the first part 28 can comprise the cylinder head and the second part 30 can comprises the rod. The interacting surface 36 of the first part 28 is the radially inner surface forming the rod-receiving bore (with the groove 40 extending radially outward therefrom) and the interacting surface 38 of the second part 30 is the radially outer surface of the rod. As shown in FIG. 7, the first part 28 can comprise the piston and the second part 30 can comprise the cylinder, with the groove 40 extending radially inward from the interacting surface 36 of the piston.

Although the fluid assembly and/or seal has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In regard to the various functions performed by the above described elements (e.g., components, assemblies, systems, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function. In addition, while a particular feature may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.

Claims

1. A fluid assembly comprising a first part, a second part, and a seal positioned within a groove in the first part; the first part having a cylindrical interacting surface and the second part having a cylindrical interacting surface, one of these interfacing surfaces being a radially inner surface of the part and the other of these interacting surfaces being a radially outer surface of the part; the first part and the second part interacting by relative linear movement therebetween, the respective interacting surfaces and the interacting surfaces interfacing with each other during such interaction; the groove extending around the circumference of the interacting surface of the first part, the groove having two axial sides extending radially outward/inward from the interacting surface, and a root side spanning terminating edges of the axial sides; the seal comprising two axial faces, a root-adjacent radial face, and an interface-adjacent radial face; the seal having a pre-installation shape prior to installation into the groove, an installed pre-interfacing shape when installed in the groove but prior to the second part interfacing with the first part, and an interfacing shape when the second part interfaces with the first part; the root-adjacent radial face having a radially concave profile when the seal is in its pre-installation shape and a flat profile flush against the groove root side when the seal is in its interfacing shape, the flat profile applying surface contact pressure against the groove root side; and the axial faces each having a radially concave profile when the seal is in its pre-installation shape and a more pronounced radially concave profile when the seal is in its interfacing shape; the more pronounced radially convex profiles forming cavities which, when filled with fluid, urge the root-adjacent seal face towards the groove root side and urge the interface-adjacent seal face towards the interfacing surface of the second part.

2. A fluid assembly as set forth in claim 1, wherein the cylindrical interacting surface of the first part is the radially inner surface and the groove extend radially outward therefrom.

3. A fluid assembly as set forth in claim 1, wherein the cylindrical interfacing surface of the first part is the radially outer surface and the groove extends radially inward therefrom.

4. A fluid assembly as set forth in claim 1, wherein root-adjacent regions of the seal axial faces of the seal apply surface contact pressure against root-adjacent regions of the groove axial sides.

5. A fluid assembly as set forth in claim 1, wherein the concave profile of the root-adjacent radial face, when the seal is the relaxed pre-installation condition, is symmetrical relative to seal circumference.

6. A fluid assembly as set forth in claim 1, wherein the concave profiles of the axial seal faces are symmetrical relative to the seal circumference.

7. A fluid assembly as set forth in claim 1, wherein root-adjacent regions of the seal axial faces are axially compressed when the seal is in its installed pre-interfacing condition.

8. A fluid assembly as set forth in claim 1, wherein the seal further comprises a hard heel.

9. A fluid assembly as set forth in claim 1, wherein the seal further comprises an internal expander.

10. A fluid assembly as set forth in claim 1, wherein the seal is made from an elastomeric polymeric material.

11. A fluid assembly as set forth in claim 10, wherein the elastomeric polymeric material is selected from the group consisting of filled or unfilled natural rubbers, synthetic rubbers, and fluoropolymers.

12. A fluid assembly as set forth in claim 1, wherein the first part comprises a first conduit having a female coupling member and the second part comprises a second conduit having a male coupling member, the conduits forming a fluid line when coupled together, and wherein the interfacing surface of the first part in a radially inner surface of the female coupling member and the groove extends radially outward therefrom.

13. A fluid assembly as set forth in claim 12, wherein the fluid line is a choke line or a kill line in an offshore drilling system.

14. A fluid assembly as set forth in claim 1, wherein the first part comprises a cylinder head having a central bore and the second part comprises a rod extending through the central bore, and wherein the interfacing surface of the first part is the radially inner surface forming the central bore and the groove extends radially outward therefrom.

15. A fluid assembly as set forth in claim 1, wherein the first part comprises a piston and the second part comprises a cylinder and wherein the interfacing surface of the first part is the radially outer surface of the piston and the groove extends radially inward therefrom.