Pipeline branch arrangements

Abstract: A pipeline branch arrangement (30) forms a piggable-Y intersection (18) at the intersection with a trunkline (16) and is oriented vertically relative to the trunkline (16). The approach piping to all legs of the piggable-Y (18) are configured to incorporate 3D bends (36) or larger radii as required. This arrangement permits the passage of foam pigs, hard pigs, and smart pigs. Orientation of the piggable-Y (18) in the vertical plane configures all of the branch piping in the vertical plane, which permits the support sled (40) width for pipe laying to be kept to a minimum. The arrangement of the 3D bends fore and aft of the piggable-Y (18) aligns the trunkline ends in a colinear manner. This permits the configuration to be installed by conventional S-Lay techniques.

Description: This invention relates to pipeline connections, and in particular to pipeline branch arrangements which may allow a pig to be passed through a pipeline. For marine pipelines, it is sometimes necessary to move a cleaning or inspection tool commonly known in the industry as a "pig" through the entire length of the pipeline. The need may occur upon completion of the pipeline before it is put into service or after the pipeline has been in service for a period of time. A marine pipeline system may consist of a number of branch or tributary pipelines feeding product into a common main or trunkline. When it is necessary to pump an intelligent or "smart" pig downstream through a branch line, special considerations in the design of the trunkline-branch connection are necessary. One of the special considerations is inclusion of a "piggable-Y" branch connection in the trunkline to allow the "smart" pig to pass unimpeded from the branch pipeline into the trunkline. The design arrangement of the piggable-Y-shaped connector in the trunkline will impact the methods of installation of the trunkline portion containing the piggable-Y-shaped connector. The present state-of-the-art technology for design of trunkline piggable-Y-shaped connections does not allow for the most direct and low cost installation method; installing the piggable-Y-shaped connector directly in the trunkline during pipe laying of the trunkline. Particularly for pipe laying operations on the bottom of a body of water, pipeline branch assemblies present a unique set of problems that are interrelated between the insertion and removal of pigs, the pipe laying operation itself, and the installation of the branch connections. These problems involve limitations on the type of pigs that may be used, the limitations and requirements for pipe laying equipment, and the need for the use of divers. These problems will be discussed further in the detailed description with reference to drawings to more clearly illustrate the problems involved. US Patent US 3,116,503 provides an automatic line selector for scraper operations in a pipeline. The automatic line selector comprises a housing having a fluid-tight interior construction. The housing contains a sleeve pivoted near its upstream end so that the sleeve can swing horizontally within the housing to make a fluid connection between an upstream pipe and a downstream pipe. US 3,116,503 illustrates the use of three pipes, the ends of which protrude into the housing: two downstream and one upstream. Connecting the sleeve to the upstream pipe and one of the downstream pipes allows a scraper or pig to pass through that pipe combination. To direct the scraper or pig through the other downstream pipe requires the scraper or pig to be located upstream of the housing before moving the sleeve into fluid communication with the other downstream pipe. The present state of the art does not address the problems outlined above and leaves a need for pipeline branch connections that are less restrictive on the type of pigs that may be used, the pipe laying operation, and the need for divers. According to the invention, there is provided a pipeline comprising a trunkline, a branch line and a branch arrangement, wherein the branch arrangement has a piggable connector incorporated in the trunkline, characterised in that: the piggable connector is Y-shaped, which piggable-Y-shaped connector forms an intersection between the trunkline and the branch line; the piggable-Y-shaped connector is positioned such that two legs thereof are in the same vertical plane; and the trunkline has vertical bends having radii of 3 diameters or larger of the trunkline on each side of said piggable-Y-shaped connector, such that the trunkline pipe ends are collinear. A preferred embodiment of the invention provides a pipeline branch arrangement that forms a piggable-Y at the intersection with the trunkline and which is oriented vertically relative to the seabed. The approach piping to all legs of the piggable-Y-shaped connector is configured to incorporate long radii bends; 3D bend radii, or larger as required. This arrangement permits the passage of foam pigs, hard pigs, and smart pigs. Rotation or orientation of the piggable-Y to the vertical plane configures all of the branch piping in the vertical plane, which permits the support sled width for pipe laying to be kept to a minimum. The arrangement of the long radii bends fore and aft of the piggable-Y-shaped connector aligns the trunkline pipe ends; i.e., they are collinear. This permits the configuration to be installed by conventional S-Lay techniques, minimizing special or unique installation procedures. The preferred connection device is a diverless horizontal type collet connector. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: Fig. 1 is an elevation view of a previously proposed, typical valve assembly for diver assisted tie-in; Fig. 2 is an isometric view of a lateral hot tap clamp on a pipeline; Fig. 3 illustrates a sled with a pre-installed lateral piggable-Y and branch connection; Fig. 4 is an elevation view of an embodiment of the invention; and Fig. 5 is an end cross section view of the arrangement shown in Fig. 4 on a pipeline stinger during pipe laying. Referring to the drawings, Fig. 1 illustrates a typical branch valve assembly 10 common to pipelay operations in shallow water. This arrangement is directly layable by S-lay methods. It requires diver assistance when making the connection (flanged) but could be converted to diverless operation by replacement of the flange with a diverless connector hub type connection. It employs a standard pipe tee fitting 12, which means that the tributary pipe joins the trunkline pipe at a ninety degree intersection. This type of intersection is limiting to pigging operations. It is piggable only by spherical pigs (typically round liquid-inflated rubber type pigs). Fig. 2 illustrates a diver-installed hot tap clamp 14. The assembly is fitted and sealed around the pipeline 16 and a penetration is drilled into the pipeline. The ninety degree intersection also limits the types of pigs that may be used, as described above. Fig. 3 illustrates a piggable-Y-shaped connector 18 branch assembly that has been used and the sled required to support the configuration for this arrangement. The piggable-Y-shaped connector 18 has an included angle of thirty degrees. By various industry testing, this arrangement has been determined to be piggable and to be "hard" piggable (includes both cylindrical foam pigs, and pigs with a hard steel structural core member, and semi-rigid plastic cups). It is diverless in that the connection to the tributary line is by a vertically oriented, connector configuration 20 specifically designed for use with a diverless collet connector. This arrangement is limiting in that it requires a large surface area sled 22, typically fifty feet square or larger. Such a sled 22 requires time consuming, special surface handling installation techniques, and is not generally installable by direct pipe laying methods. The invention is illustrated in Fig. 4 and 5. The branch arrangement 30 is generally comprised of a piggable-Y-shaped connector 18 placed in the trunkline 16, tributary pipe line or branch line 32, isolation ball valve 34, a hub for connection to a horizontal collet connector 44, and vertical bends 36 in the trunkline 16. The piggable-Y-shaped connector 18 is placed in the trunkline 16 at the desired location with the orientation of the piggable-Y-shaped connector 18 being such that at the open Y end, both legs of the piggable-Y-shaped connector 18 will lie in the same vertical plane. This results in both legs of the piggable-Y-shaped connector 18 being positioned in a common vertical plane with the trunkline 16 during pipe laying operations, and when the trunkline 16 is installed on the sea floor. This is illustrated in Fig. 4. This arrangement contrasts with the prior configuration shown in Fig. 3 where the legs of the piggable-Y-shaped connector 18 are placed in the horizontal plane. In Fig. 3, the trunkline 16 is connected to the downstream stub of the piggable-Y-shaped connector 18 and one upstream leg of the piggable-Y-shaped connector 18, while the future branch line 32 will be connected to the upstream stub of the Y. A support 38 may be provided between branch line 32 and trunkline 16. Vertical bends 36, of at least 3D radii, are provided in the approach section of the trunkline 16 to both ends of the piggable-Y-shaped connector 18. This bend radius may be increased, as required. The arrangement of the invention permits the passage of foam pigs, hard pigs, and "smart pigs". Smart pigs are typically inspection-related, and incorporate a linked train of pigs which require larger bend radii to assure passage. Rotation of the piggable-Y-shaped connector 18 to the vertical plane configures all of the branch connection piping in the vertical plane, which permits the support sled 40 to be designed with a much narrower width than the prior art. Fig. 5 illustrates the invention and support sled 40 as they travel through a pipelay stinger 42 during pipe laying. Also, the arrangement of the 3D bends fore and aft of the piggable Y-shaped connector 18 aligns the trunkline 16 ends; i.e., they are collinear. This results in the ability to use conventional direct S-lay techniques, which minimizes special, unique, and more costly installation procedures. The horizontal collet connector 44 may be operated by a remotely operated vehicle (ROV) and does not require the presence of a diver. Eliminating the need for diver interaction with the connector eliminates water depth limitations, other than the ability to support the sled weight during the pipe laying operation. it should be noted that the invention is not necessarily limited by radius; the radius can be as small as available in the piping. The only limitation presented by a smaller radius bend is the ability to pig the pipe, especially by intelligent pig. Collet connector 44 is illustrated as being in the horizontal position. If necessary, it may be configured in the vertical position, perpendicular with the trunkline 16 in the installed position. Also, other types of connections may be used to suit the operator. Because many varying and differing embodiments may be made within the scope of the inventive concept herein taught and because many modifications may be made in the embodiment herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.

Claims: A pipeline comprising a trunkline (16), a branch line (32) and a branch arrangement (30), wherein the branch arrangement (30) has a piggable connector (18) incorporated in the trunkline (16), characterised in that : the piggable connector (18) is Y-shaped, which piggable-Y-shaped connector (18) forms an intersection between the trunkline (16) and the branch line (32); the piggable-Y-shaped connector (18) is positioned such that two legs thereof are in the same vertical plane; and the trunkline (16) has vertical bends (36) having radii of 3 diameters or larger of the trunkline (16) on each side of said piggable-Y-shaped connector (18), such that the trunkline pipe ends are collinear. A pipeline according to claim 1, wherein the branch line (32) is received in the upper leg of said piggable-Y-shaped connector (18). A pipeline according to claim 2, comprising a connector (44) received on the end of said branch line (32).

Inventors: GRAY DAVID ARTHUR, HARRISON GARY EDWARD, MCCOY STEPHEN TALBOT, GRAY, DAVID ARTHUR, HARRISON, GARY EDWARD, MCCOY, STEPHEN TALBOT
Applicants: MCDERMOTT SA J RAY, J RAY MCDERMOTT, S.A.
Application year: 1998
Main classification: F16L55
IPC codes: F16L55