GB2543860A

GB2543860A - Pipeline coupling

Info

Publication number: GB2543860A
Application number: GB1521172.5A
Authority: GB
Inventors: Nigel Smith Keith
Original assignee: DESTEC ENG Ltd
Current assignee: DESTEC ENG Ltd
Priority date: 2015-12-01
Filing date: 2015-12-01
Publication date: 2017-05-03
Anticipated expiration: 2035-12-01
Also published as: GB2543860B; GB201521172D0

Abstract

A pipeline coupling comprises a first generally tubular body 1 having providing on the internal surface thereof a segment of a spherical surface, a second body 8 in the form of a tubular spigot mounted within the first body 1 and having at one end thereof a segment 7 of a spherical surface engaging the spherical internal surface of the first body, a flanged tubular coupling 2 attachable to the first body, and a tubular seal 11 extending from the tubular coupling 2 and engaging a segment 12 of a spherical surface on the bore through the second body 8, the internal diameters of the seal 11, the second body 8 and the flanged tubular coupling 2 being equal.

Description

PIPELINE COUPLING

Field of the Invention

This invention relates to a pipeline coupling, for example for underwater oil pipelines.

Background to the Invention

Oil pipelines may be run along the seabed to bring oil ashore from production platforms or subsea wellheads. A pipeline may be buried in a trench cut into the seabed, but this adds considerably to the cost. An alternative is to lay the pipeline on the surface of the seabed, but this requires some ability of the pipeline to follow the variable contours of the seabed. In view of the high pressures involved, oil pipelines are formed of lengths of steel pipe typically connected together by flanged couplings containing a high-pressure seal. Conventional flanged couplings do not offer any ability to accommodate misalignment.

Various proposals have been made for pipeline couplings that provide some swivel capability. For example, US4530526A discloses a ball coupling in which a flanged coupling contains a segmental spherical surface to receive a corresponding part-spherical external surface of a connector member which can then be welded to a further pipe member to provide a swivel connection in the pipeline lockable in its desired position by tightening the flanged coupling. In order to accommodate the different alignment angles of the internal bore, the bore within the connector member is flared outwardly at its opening within the connector to direct the flow into the next section of the pipeline. Seals are provided between the co-operating spherical surfaces.

This arrangement has some disadvantages. Firstly, the flared section means that there is a discontinuity in the internal bore of the pipeline, which can make pigging of the pipeline (i.e. the passage of a pig through the pipeline to perform maintenance operations, such as cleaning or inspection) difficult because there is a risk that the pig will get stuck at the discontinuity, the risk being greater in one direction of travel. Secondly, a metal seating ring as a fluid seal is required between the face of the coupling and the flanged coupling attached to the end of the next pipe section. These seals act on the external diameter of the spherical surface and hence seal at a much larger diameter than the bore of the pipe. This considerably increases the hydrostatic end load on the coupling, requiring a larger and heavier coupling construction. Costs are thus high, not only the capital cost of the coupling, but also the installation costs, as well as having an impact on the dimensions of the connected pipework and fittings. Summary of the Invention

Accordingly, the present invention provides a pipeline coupling comprising: a first generally tubular body providing on the internal surface thereof a segment of a spherical surface; a second body in the form of a tubular spigot mounted within the first body and having at one end thereof a segment of a spherical surface engaging the spherical surface on the internal surface of the first body; a flanged tubular coupling attachable to the first body; and a tubular seal extending from the tubular coupling and engaging a segment of a spherical surface on the bore through the second body, the internal diameters of the seal, the second body and the flanged tubular coupling being equal.

The first body is preferably formed as two parts with part of the segment of a spherical sur-face on each of said two parts, the two parts being secured together with resiliently-compressible means therebetween, whereby when the two parts are clamped together to compress the resiliently-compressible means, the second body is locked against deflection relative to the first. The resiliently-compressible means are suitably compression springs.

The tubular seal is suitably formed of metal, more preferably of a nickel-chromium alloy such as Inconel (RTM).

In one embodiment of the invention, the first body and the second body are each provided with circumferential flanges securable one to the other by an external clamp engageable with the flanges.

The external surface of the seal in contact with the spherical surface in the bore of the second body is preferably a corresponding spherical surface.

The pipeline coupling of the invention can be made more compact and lighter than other swivel couplings and can be supplied as a complete unit for attachment to an existing part of a flange coupling, simplifying assembly of a pipeline, especially where assembly is required to be carried out under water by a diver. The coupling can readily be scaled for a range of pipe diameters. Because there is no significant discontinuity of the pipeline internal diameter at the coupling, a pipeline pig may readily be passed through it.

Brief Description of the Drawings

In the drawings, which illustrate an exemplary embodiment of the coupling of the invention:

Figure 1 is a cross-sectional elevation of the coupling with the two parts aligned on the same axis; and

Figure 2 is a corresponding view but with the two parts misaligned. Detailed Description of the Illustrated Embodiment A pipeline swivel coupling comprises two principal components, an adjustable component 1 for welding to a first pipe and a fixed component 2 for welding to a second pipe, the two components being coupled together with through bolts and nuts 3 and 4. It will be appreciated that as an alternative arrangement studs may be threaded into one component, suitably the adjustable component 1, and nuts used to secure the other component to it. The adjustable component 1 comprises an outer tubular body formed from two parts 5 and 6 having on the internal surfaces thereof a segment of a spherical surface which receives an external spherical surface 7 formed at one end of a short tubular spigot 8 adjustably mounted within the outer tubular body, the interaction of the spherical surfaces permitting the spigot to be swivelled relative to the outer tubular body by a small angle, for example up to 5°. The two parts 5 and 6 are held together by screws with spring washers between the two parts located so as to separate the parts one from another by a very small distance, for example 1mm or less. The inner body can thus swivel within the outer body until the coupling is clamped together by tightening the main bolts and nuts 3 and 4, causing the two parts 5 and 6 to move together. In so doing, the clearance between the their internal spherical surfaces and the external spherical surface 7 is reduced, thereby clamping the spigot at its adjusted angular position relative to the outer tubular body.

An annular seal retainer plate 9 is screwed to the end face of the part 5 of the outer tubular body, the inner edge of the plate abutting an external ridge 10 on a tubular seal 11 located within a gently flared internal surface leading into a spherical seal area 12 within the portion of external spherical surface 7 at the inner end of the spigot 8. The tubular seal 11, which is suitably formed of Inconel (RTM) alloy, has a spherical external surface at the end thereof remote from the ridge 10, the spherical surface bearing against the internal spherical surface 12 to form a fluid seal therewith.

The fixed component 2 is suitably one half of our Compact Flange connector, having an annular flange 13 at one end of a short spigot 14 for welding to a pipe, the inner edge of the annular face of the flange 13 having a tapered recess 15 therearound to receive a correspondingly-shaped outer end face 16 of the seal 11. When the flange 13 is clamped to the adjustable component 1, the seal is urged into sealing contact with the flared internal surface 12 of the spigot 8. The tubular seal 11 has an internal diameter which corresponds to the internal diameters of the adjustable and fixed components 1 and 2.

In use, the adjustable component 1 is welded to the end of a first pipe section, while the fixed component 2 is welded to the end of a second pipe section. When the pipeline is to be installed on the sea bed, the adjustable and fixed sections are coupled together and the nuts are rotated to hold the components together, but are not fully tightened, so that, when the pipeline is positioned on the sea bed, the small degree of adjustability permits the sections to adopt an alignment which more closely follows the surface variations of the sea bed, thereby avoiding unduly stressing the pipeline. When the pipeline has settled into position, a diver can then tighten the nuts to their desired operating torque, locking and sealing the coupling.

The gentle flare of the surface 12, together with the elongated tubular seal whose internal diameter is the same as that of the pipeline, means that the passage of a pipeline pig is not inhibited by the change in alignment in the coupling. The seal 11 is provided with a slight chamfer on its internal surface at its end remote from the fixed component to assist is guiding a pig through the change in alignment without presenting a discontinuity against which the pig could become trapped. A recess 17 around the mouth of the flared internal surface within the spherical surface end of the spigot 8 receives a portion of the ridge 10 when the spigot 8 is fully deflected from its aligned position within the component 1. It will be seen from the Figures that the external shape of the seal 11 conforms with the internal shape of the flared internal surface when these are in contact.

While the coupling has been described as being secured together with nuts and bolts or studs, in an alternative embodiment an external clamping ring engages external flanges around the adjustable component and the fixed component to clamp them together. The clamping ring has a single clamping bolt to hold it in place, thus facilitating its tightening, to clamp and fix the coupling, by remotely operated vehicle (ROV), allowing installation in water deeper than that at which divers can operate, typically limited to about 1000 feet (305m).

Claims

1. A pipeline coupling comprising: a first generally tubular body providing on the internal surface thereof a segment of a spherical surface; a second body in the form of a tubular spigot mounted within the first body and having at one end thereof a segment of a spherical surface engaging the spherical surface on the internal surface of the first body; a flanged tubular coupling attachable to the first body; and a tubular seal extending from the tubular coupling and engaging a segment of a spherical surface on the bore through the second body, the internal diameters of the seal, the second body and the flanged tubular coupling being equal.

2. A pipeline coupling according to Claim 1, wherein the first body is formed as two parts with part of the segment of a spherical surface on each of said two parts, the two parts being secured together with resiliently-compressible means therebetween, whereby when the two parts are clamped together to compress the resiliently-compressible means, the second body is locked against deflection relative to the first.

3. A pipeline coupling according to Claim 2, wherein the resiliently-compressible means are compression springs.

4. A pipeline coupling according to Claim 1,2 or 3, wherein the tubular seal is formed of metal.

5. A pipeline coupling according to Claim 4, wherein the metal is a nickel-chromium alloy.

6. A pipeline coupling according to any preceding claim, wherein the tubular seal is mounted in an annular plate attached to a face of the first body.

7. A pipeline coupling according to Claim 2 or 3, wherein the first body and the second body are each provided with circumferential flanges se-curable one to the other by an external clamp engageable with the flanges.

8. A pipeline coupling, substantially as described with reference to, and/or as shown in, the drawings.

8. A pipeline coupling according to any preceding claim, wherein the external surface of the seal in contact with the spherical surface in the bore of the second body is a corresponding spherical surface.