GB2207724A - Flowline connector seal - Google Patents

Abstract

A seal for connecting two flowlines comprising a U-shaped annular metal seal and an expander load ring which engages the U-shaped seal upon relative movement to expand and to plastically deform the seal to thereby provide a fluid tight seal between flowlines. Connectors incorporating the seals can be between production risers and a marine riser base. <IMAGE>

Description

FLOWLINE CONNECTOR SEAL The present invention relates to a seal for flowline connections and more particularly relates to a U-cup seal which is set by expansion to effect a high pressure seal at a connection between two flowline sections.

A critical consideration in the production of fluid hydrocarbons from marine deposits lies in providing a fluid communication system from the marine bottom to the surface after production has been estalished. Such a system, commonly called a production riser, usually includes multiple conduits through which various fluids are transported to and from the surface and includes individual oil and gas production lines, hydraulic. control lines, and the like.

In installing a typical production riser system, a base is preset on the marine bottom and submerged flowlines are completed from subsea production facilities, e.g. individual wells, production manifolds, etc., to individual connector heads on the base. The riser is then lowered from the surface and flowline conduits, carried by the riser, are connected to their respective connector heads on the base to provide individual flowlines to the surface.

Due to the water depths in which such risers are normally installed, the use of divers to make the necessary connections at oronear the marine bottom is impractical. Accordingly, these connections must be capable of being made and released remotely.

Further, since these flowlines normally carry hydrocarbon fluids, sometime at very high pressures, it is imperative that the remote connections between flowlines be properly sealed so that they do not leak during operation. This requires a sealing means that can be carried by a remote connector on the flowline which is set as the connection ts made between flowline sections to provide a highly reliable seal therebetween. Most known seals for such connections rely on compression to effect the desired sealing action and while many such seals have proved adequate, there has remained a need for a seal which will better withstand the rigorous requirements demanded for prolonged use in such environments.

Accordingly, the present invention provides a sealing means for sealing a connection between a box member on a first flowline and a pin member on a second flowline, the sealing means comprising an annular metal seal adapted to be positioned around the pin member and within the box member and having an annular groove in and around the upper surface thereof to thereby provide a seal having a base and two legs which define a seal having a U-shaped cross-section wherein the inner portions of the upper surfaces of the legs taper inwardly and downwardly at an angle; and an adapter load ring having a nose section adapted to slidably and snuggly fit into the annular groove with the lower end of the nose section almost in contact with the base of the seal within the groove wherein the upper, outer surfaces of the nose section of the expander load ring taper upward and outward at substantially the same angle as that of the upper surfaces of the legs whereby the tapered surfaces mate with each other when the nose section is in the groove whereby movement of the expander ring into the groove expands one of the legs outwardly against the box member and the other of the legs inwardly against the pin member and the bottom of the nose section contacts the base to plastically deform the seal between the pin and box members.

The actual construction, operation, and apparent advantages of the present invention will be better understood by referring to the drawings in which like numerals identify like parts and in which: Fig. 1 is a sectional view of a typical marine riser base and flowline connector in which the present invention may be incorporated; Fig. 2A is a sectional view of the flowline connector of Fig. I in an open or unlocked position; Fig. 28 is a sectional view of the flowline connector of Fig. 2A in a closed or locked position; Fig. 3 is an exploded sectional view of the metal U-cup seal and the expander load ring of the present invention; and Fig. 4 is a partial, sectional view of the expander load ring and the metal seal of Fig. 3 in an assembled but unset position.

To better understand the advantages of the present invention, a brief description of a typical environment in which the sealing means of the present invention is likely to find widespread use will first be set forth. Referring more particularly to the drawings, Fig. 1 discloses marine rise base 15 which is preset on a marine bottom 16. As illustrated, base 15 is comprised of a template 22 having a mandrel 23 embedded in bottom 16 and extending upward through template 22 and is adapted to receive a hydraulic connector 24 carried on the lower end of riser core conduit 25 for securing the riser core to base 15. As will be-understood, riser core 25 extends upward towards the surface and supports a plurality of peripheral or first flowlines 21 therearound (only one shown) by means of spaced guides or the like (not shown).An inverted, cone-shaped cover plate 26 is attached to mandrel 23 and extends out over a plurality of connector heads 27 (only one shown) on template 22. Each connector head 27 is adapted to be completed to a subsea production or second flowline (not shown) leading to a subsea production source or to a subsea control or supply system as the case may be. An oriented, inverted funnel 28 depends from connector 24 to mate with coverplate 26 when the riser is assembled on base 15 and posts 29 on template 22 cooperate ith guides 30 on funnel 28 to aid in final orientation. Flowline guides 31 and openings 32 in funnel 28 and cover plate 26, respectively, are vertically aligned to permit peripheral flowline 21 to be passed downward therethrough and to be connected to head 27 on template 22 by flowline connection 33 in which the sealing means of the present invention is mounted.

For additional details of base 15 and the riser connector means shown in Fig. 1 and the operation thereof, see U.S. Patent 4,673,313.

It will be understood that the connection between flowline 21 and connector head 27 must be tightly sealed to prevent leaking therebetween when flow is commenced. To accomplish this, flowline connector 33 must include a sealing means that will provide a reliable fluid-tight seal between the connector and head 27 when connector 33 is set.

Referring now to Figs. 2A and 28, a typical flowline connector 33 which incorporates the sealing means of the present invention is illustrated and is comprised of a box member 34 and pin member 35 having a bore 35a therethrough. Pin member 35 forms part of connector head-27 on base 15. Box member 34 is comprised of a hollow housing 36 which is adapted to be affixed to the lower end of a first flowline 21. Positioned within the bore 36a of housing 36 is lockdown ring 37 which is made of spring steel or the like. Ring 37 is inherently biased toward an expanded or open position as shown in Fig. 2A, but is split in one place so that it can be compressed to a locked or closed position (Fig. 28) as will be further explained below.Lockdown ring 37 has a plurality of dogs 38 thereon which cooperate with a pluralty of annular grooves 39 in pin member 35 when ring 37 is moved to a locked position.

Slidably positioned in bore 36a of housing 36 above lockdown ring 37 is actuator sleeve SO which, in turn, has a wedge section 51 adapted to cooperate with the outer surface of ring 37 to move ring 37 inwardly as sleeve 50 is moved downward. Sleeve 50 is threaded at its upper end to collet body 52. The upper portion of said collet body being sawcut into individual collets 53 which, in turn, are inherently biased outward but have sufficient flexibility to permit inward movement toward the longitudinal axis of bore 36a.

Each collet 53 has a detent shoulder 54 at the upper, outer periphery thereof which cooperates with an annular detent groove 55 in housing 36 to hold actuator sleeve 50 in its open or upward position until connector 33 is to be set and locked. Each collet 53 also has ratchet shoulders 56 on its outer periphery and spaced below detent shoulder 55, said ratchet shoulders 56 being adapted to cooperate with one of a plurality of annular ratchet grooves 57 which are provided in bore 36a of housing 36 for a purpose described below.

Each collet 53 also has an inner, downward and inwardly sloping release surface 58 for engaging an upward and outwardly sloping surface 62 on shifting sleeve 60 to release ratchet shoulder 56 from grooves 57 when sleeve 60 is moved upward with respect to collet body 52 during the release of connector 33. Manipulator nut 41 is threaded into the lower end of box member 34 and carries seal means 70 within annular groove 42 in the upper surface thereof.

To set connector 33, a removable tool (not shown) is placed in the bore of box member 34 and fluid pressure is applied thereto to move actuator sleeve 50 downward to cam detent shoulders 54 on collets 53 out of grooves 57. This allows wedge 51 to move downward to force lockdown ring 37 inward to engage dogs 38 into grooves 39 on pin member 35. As collets 53 move downward, ratchet shoulders 56 engage ratchet grooves to lock actuator sleeve 50 in its downmost position. The details of connector 33 and the operation thereof as described to this point are basically the same as fully described in U.S. Patent 4,661,016. The only exception lies in the present seal means 70 which will now be explained in detail.

Sealing means 70 of the present invention is comprised of an annular metal, U-cup seal 72 and an expander load ring 71. U-cup seal 72 is comrised of a relatively soft metal ring 75; e.g. 316 stainless steel, 160 BHN (Brinell Hardness Number) Max. having a inner diameter slightly larger but substantially equal to the external diameter of the tubular element to be sealed, e.g. pin member 35. Annular groove 76 is formed into and around the upper surface of ring 75 and extends inward to a depth approximately equal to one-half of the total length of ring 75 to thereby produce a U-shaped, cross-sectional configuration having a base 77 and two legs" 78. The upper surfaces 79 of both legs 78 are tapered inwardly and downwardly at an angle alpha, e.g. 300.Preferably, an annular groove 80 is provided in the outer wall of ring 75 to provide an outer lip 81 and the inner wall of ring 75 is machined to provide an inner lip 82 thereon. A single narrow, radial groove 83 (dotted lines in Fig. 3) is provided in the lower surface of ring 75 for a purpose explained later.

Expander ring 71 is comprised of a metal ring 84 having integral nose section 85, intermediate stepped section 86, and an upper section 87. Both the inner and outer walls 88 of ring 84 are tapered upward and outward between nose section 85 and intermediate section 86 at the same angle alpha as are surfaces 79 of U-cup seal 72. The width of nose section 85 is only slightly less than the width of groove 76 in ring 75 so that it will slidably but snuggly fit therein. A single, radial passage 89 is provided through intermediate section 86 and connects with vertical passage 90 through nose section 85 for a purpose explained later. A single radial groove 91 is provided across the lower surface of nose section 85 and in communication with vertical passage 90.

As illustrated in Fig. 2A, sealing means is assembled in connector 33 with expander load ring 71 below and in contact with lock ring 37. U-cup seal 72 is positioned in groove 42 of nut 41 which, in turn, is threaded in the lower end of box member 34. When assembled, the nose section 85 of expander load ring 71 is positioned within groove 76 of U-cup seal 72 with tapered surfaces 88 of expander load ring 71 resting on tapered surfaces 79 on U-cup seal 72 (Fig. 4). When in this position, there is a very small clearance, e.g. 0.75 mm (0.030 inches) between the bottom of nose section 85 and the top of groove 76.

As explained above, as connector 33 is set, wedge 51 moves downward thereby forcing lock ring 37 inward and expander load ring 71 downward. As ring 71 moves downward under load, surfaces 88 on ring 71 react with surfaces 79 on U-cup seal 72 to force inner and outer legs 78 outward against pin member 35 and box member 34, respectively. Also, due to the construction of U-cup seal 72, in addition to the expansive forces, the downward movement of expander ring 71 will also develop a compressional downward force in legs 78 and against the base 77 of seal 72 thereby causing plastic deformation and brinelling of the metal seal between the seal and its adjacent surfaces.Since downward movement of the expander ring 71 is limited, a very high loading force is continuously applied downward through legs 78 and base 77 of U-cup seal 72 which, in turn, transmits these forces parallel to the centerline of the flowline. Further, since the seal 72 is plastically deformed when set, it will maintain its sealing efficiency even if conditions tend to back-off expander ring 71 upwardly from U-cup seal 72.

As expander ring 71 moves downward into groove 76 of seal 72, any fluids that may be present in the groove below nose section 85 will flow through groove 91 and passages 90, 89 and exit above seal 72 and around intermediate section 86 of expander ring 71. Further, radial groove 83 in the lower surface of seal 72 acts to vent fluids trapped below seal ring to allow solid, metal-to-metal contact between seal ring 72 and groove 42 of manipulator nut 41.

While the present sealing means 70 has been described in relation to use in a subsea environment and as a part of connector 33, it should be understood sealing means 70 can be used with connectors having constructions different from that of connector 33 and can be used anywhere a flowline connection, similar to that illustrated, is needed.

Claims (12)

CLAIMS:

1. A sealing means for sealing a connection between a box member on a first flowline and a pin member on a second flowline, the sealing means comprising: an annular metal seal adapted to be positioned around the pin member and within the box member and having an annular groove in and around the upper surface thereof to thereby provide a seal having a base and two legs which define a seal having a U-shaped cross-section wherein the inner portions of the upper surfaces of the legs taper inwardly and downwardly at an angle; and an adapter load ring having a nose section adapted to slidably and snuggly fit into the annular groove with the lower end of the nose section almost in contact with the base of the seal within the groove wherein the upper, outer surfaces of the nose section of the expander load ring taper upward and outward at substantially the same angle as that of the upper surfaces of the legs whereby the tapered surfaces mate with each other when the nose section is in the groove whereby movement of the expander ring into the groove expands one of the legs outwardly against the box member and the other of the legs inwardly against the pin member and the bottom of the nose section contacts the base to plastically deform the seal between the pin and box members

2. The sealing means of claim 1 wherein the angle equals approximately 300.

3. The sealing means of claims 1 or 2 wherein the seal is comprised of metal.

4. The sealing means of claim 3 wherein the metal is 316 stainless steel, 160 BHN Max.

5. The sealing means of any preceding claim wherein the expander ring has a radial passage therethrough at a point above the nose section and a vertical passage through the nose section in fluid communication with the radial passage.

6. The sealing means of claim 5 including: a radial groove in the lower surface of the expander ring extending in fluid communication with the vertical passacr through the nose section.

7. A connection means for connecting flowlines comprising: a pin member on one of the flowlines; a box member on the other the flowlines, the box member comprising: a housing adapted to fit over the pin member; sealing means carried by the housing and comprising; an annular metal seal having an internal diameter slightly larger than the external diameter of the pin member when the box member is in position on the pin member; the seal having an annular groove in and around the upper surface wherein the seal has a base and two legs which define a U-shaped cross-sectional area wherein the inner portions of the upper surfaces of the legs taper inwardly and downwardly at an angle; an expander load ring having a nose section adapted to slidably and snuggly fit into the annular groove with the lower end of the nose section almost in contact with the base of the seal within the groove and wherein the upper, outer surfaces of the nose section of the expander load ring taper upward and outward at substantially the same angle as that of the upper surfaces of the legs whereby the tapered surfaces mate with each other; and means for moving the expander ring into the groove in the seal to expand one of the legs outwardly against the box member and the other of the legs inwardly against the pin member to engage the base within the groove to plastically deform the seal between the pin and box members.

8. The connection of claim 7 wherein the angle equals 300.

9. The connection means of claims 7 or 8 wherein the depth of the groove in the seal is equal to approximately one-half of the length of the seal.

10. The connection means any of claims 7 to 9 including: a manipulator nut threaded into the lower end of the housing of the box member and having an annular groove in the upper surface thereof for mounting the annular metal seal therein.

11. The connection means any of claims 7 to 10 wherein the expander load ring has a radial passage therethrough at a point above the nose section and a vertical passage through the nose section in fluid communication with the radial passage.

12. The connection of means of claim 11 including: a radial groove in the lower surface of the expander load ring in fluid communication with the vertical passage through the nose section.