WO2000000380A2

WO2000000380A2 - Connector for connecting a fluid pipe within a swivel stack

Info

Publication number: WO2000000380A2
Application number: PCT/US1999/014449
Authority: WO
Inventors: Malcolm E. Turner; Malcolm J. Perschke
Original assignee: Fmc Corporation
Priority date: 1998-06-29
Filing date: 1999-06-24
Publication date: 2000-01-06
Also published as: BR9911994A; WO2000000380A3; CA2333002A1; AU4833599A

Abstract

An improved product swivel (12) is disclosed which includes a connection which connects a product pipeline (16) to an internal elbow line (34) of the internal housing (13) of the swivel (12). A connector female or box half (42) is welded or machined to the swivel elbow (34). The other half of the connector pair, a pin member (46), is welded to the end of the product pipeline (16). An installation tool and clamp (44) about the connector pair pulls the pin (46) and box (42) together, radially expands the box (42), and then shrinks the box (42) onto the pin (46) so that non-helical engaging teeth (43) wedge together to produce axial tensions in the connection (40). The connection (40) is of minimum outside diameter which advantageously reduces the space requirement inside the swivel stack.

Description

TITLE: CONNECTOR FOR CONNECTING A FLUID PIPE WITHIN A

SWIVEL STACK

BACKGROUND OF THE INVENTION

Cross Reference to Related Application

This application claims priority from Provisional Application 60/091,098 filed June

29, 1998.

Field of the Invention

This invention relates to a fluid swivel stack capable of transferring fluids to and from ships, tankers, and other sea-going vessels. In particular, it relates to a connector for connecting fluid pipes or risers within the fluid swivel stack for the transfer of product to and from the sea-going vessels to and from subsea wells.

Description of the Prior Art

A swivel stack for a floating, production, storage and offloading (FPSO) vessel normally has a plurality of generally vertical product risers or pipes extending to the central body of the swivel stack from the sea floor. A swivel on the stack is normally provided for

each fluid pipe. Generally horizontal outlet pipes or conduits extend from the swivels to storage areas of the FPSO vessel. The vessel weathervanes about a turret to which the stack body and risers are connected, and the swivels move with the vessel relative to the swivel stack body and risers extending within the body. The stack body which receives the vertical risers is of a generally cylindrical shape. It is desirable to have the body of minimal dimensions. Elbows extend between the product pipes and annular passages in the swivels.

Hubs and bolted flanges have commonly been employed to connect the product pipe to the elbows. Such hubs or flanges require space within the cylindrical body of the swivel stack.

Summary of the Invention

The present invention is directed to a swivel stack having an inner cylindrical body with a plurality of swivels thereon and a plurality of vertically extending risers or pipes extending from subsea wells within the inner cylindrical body. Elbows extend between the vertical risers and swivels. An improved vertically extending connector is provided between each vertical riser and its associated elbow. The vertically extending connector includes mating female and male end portions welded to the elbow and vertical riser. The mating female and male end portions have non-helical, interlocking circumferential teeth and are assembled with a hydraulic tool which includes a hydraulic clamp and a hydraulic pump. After stabbing of the male and female end portions, the clamp is fitted about the connector, and hydraulic pressure is injected between the mating end portions which form a pin and box connection. The pressure expands the female (box) end portion, while the clamp pulls the two end portions together resulting in a wedging action of the teeth. The wedging action of the teeth converts radial preload into a high axial preload to maintain connector stiffness. A specific connector that has been found to be satisfactory may be purchased as a "Merlin" connector from Oil States Industries (UK) Ltd. of Aberdeen, Scotland.

The connector of this invention (1) utilizes a minimum diameter which minimizes the space requirement within the swivel stack from the multiple pipes or risers and avoids the use of hubs or bolted flanges as common heretofore, (2) utilizes a minimum number of connector parts, and (3) may be assembled in minimal time as compared to a flanged connection.

Other features and advantages of this invention will be apparent from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic of a swivel stack showing a plurality of fluid pipes or risers extending within the stack from subsea wells with fluid product lines extending from outer swivels to storage areas on the storage vessel;

Figure 2 is an enlarged sectional view of a vertical portion of the swivel stack showing a pair of adjacent stacked modules, each having a swivel thereon; and

Figures 3A, 3B, and 3C illustrate stages in the creation of a connection between a product inlet pipe and an inlet end of an elbow of a product swivel.

DESCRD7TION OF THE INVENTION Referring to the drawings, a swivel stack is shown generally at 10 having a generally cylindrical body 11 formed by a plurality of modules or sections 12 vertically stacked on one another with each section 12 having a body portion or inner housing 13 with a swivel outer housing 14 mounted thereon. A suitable product line 16 extends from each swivel outer housing 14 to a storage area or hold in the storage vessel. The vessel and the swivel 14 are designed and arranged to weathervane about the stacked inner housing 13. Cylindrical body outer housings 11 comprise internal interconnected housings 13 on which swivel outer housings 14 are rotatively mounted. The cylindrical body 26, secured to inner housings 13, is connected to a turret about which the vessel can rotate due to weatherwaning. As a result, swivel outer housings 14 rotate with the vessel relative to stacked body 11 upon weathervaning of the vessel about stacked body 11.

As shown particularly in Figure 2, vertical stack 10 includes a pair of stacked sections or swivels 12 stacked on one another. Of course, more than two swivels 12 may be provided for stack 10. Each body portion 11 of each swivel 12 is connected to a female end portion 22 and a lower male end portion 24. Adjacent swivels 12 are connected to each other. Body 11 which includes a plurality of connected body portions 13 has an inner peripheral surface 26 of a predetermined internal diameter to provide space to receive vertically extending product pipes or risers 28 which extend downwardly to subsea wells. Bearing assemblies 29 mount each outer swivel housing 14 for rotation relative to an associated body portion 13 to permit weathervaning of the vessel and body 11. An annular fluid passage 30 is provided for each swivel 14 and is in fluid communication with an associated product pipe 16 extending to a suitable storage area in the storage vessel. If desired, each body portion 11 could be provided with end flanges mating with opposed end flanges on adjacent body portions 11. The body portions are preferably connected together by a "Merlin" connector or alternatively mating flanges may be bolted together to provide a plurality of stacked swivels 12.

Elbows generally indicated at 34 are connected between risers 28 and product pipes 16. Each elbow 34 has a horizontal portion 36 in fluid communication with annular passage 30 and a vertical portion 38 turning at right angles to horizontal portion 36. Vertical riser or pipe 28 is connected to vertical portion 38 of elbow 34 by a connector generally indicated at 40 which forms an important part of this invention. Connector 40 has a female end portion 42 welded at 44 to vertical portion 38 and a male end portion 46 welded at 48 to vertical pipe 28. If desired, the end portions could be reversed. A connector which has been found to be advantageous is sold as a "Merlin" connector by Oil States Industries (UK), Ltd., of Aberdeen, Scotland.

Figures 3 A, 3B, and 3C illustrate the steps in assembling female (box) end portion 42 and male (pin) end portion 46. The connector 40 is not fully made up in the illustration of connector 40 of Figure 3 A. The interlocking teeth 43 are non- helical interlocking teeth, which because of design geometry, can mesh only when the pin and box are in the fully made-up position. Figure 3B shows the connection after stabbing of pin end portion 46 into box portion 42. A tool 44 extends about the outer periphery of connector 40. A hose 48 is connected to a port in the box connector 42 for application of hydraulic pressure between the pin 46 and the box 42. The tool pulls the pin and box, illustrated by arrows A-A into a fully made-up relationship as hydraulic pressure via passage 48 expands the box 42. When pressure is relieved, the box 42 "shrinks" onto the pin 46. Figure 3C illustrates the connection after the tool 44 has been removed.

The wedging action of the teeth 43 converts radial preload of the connection into a high axial preload to maintain the stiffness of the connector. Connector 40 presents a minimum outside diameter, thereby minimizing the space requirement within swivel stack 10 defined by the inner peripheral surface 26 of stack body or housing 11. The connector 40 has a minimal number of connector parts and is easily connected or disconnected in a minimum of time. The assembly as shown in Figure 3 A, 3B, and 3C is accomplished in an effective, uncomplicated manner.

While a preferred embodiment of the present invention has been illustrated in detail, it is apparent that modifications and adaptations of the preferred embodiment will occur to those skilled in the art.

Claims

WHAT IS CLAIMED IS: 1. An improved product swivel which includes a cylindrical internal housing having a longitudinal axis and a rotative swivel outer housing which is rotatively coupled about the outer perimeter of said internal housing, said internal housing and said swivel outer housing having a fluid flow path provided from said internal housing to said swivel outer housing, said swivel outer housing having an outlet product line which communicates with said fluid flow path and extends outwardly of said swivel outer housing, said internal housing having an inlet line which communicates at one end with said fluid flow path and extends inwardly into said internal housing with an elbow turn in a direction parallel to said longitudinal axis to a second end; wherein the improvement comprises an internal product pipe having an outlet end which extends parallel to said longitudinal axis of said internal housing, with said outlet end of said internal product pipe facing said second end of said inlet line, a connector having mating box and pin end portions, with one portion secured to said second end of said inlet line and the other portion secured to said outlet end of said internal product pipe, said mating box and pin end portions having non-helical, interlocking circumferential teeth which are arranged and designed to mesh only when fully made up and with said box end portion being shrunk onto said pin end portion, wherein said circumferential teeth are wedged together thereby producing a high axial preload between said box and pin end portions that maintains stiffness and enhances fatigue characteristics of said connector.

2. The improved product swivel wherein said box end portion is shrunk onto said pin end portion by placing a clamp around said pin end and box end portions, injecting hydraulic pressure between said pin and box end portions through a port, thereby radially expanding said box end portion while axially pulling said pin and box end portions to a fully made up position, and releasing said hydraulic pressure thereby shrinking said box end portion onto said pin end portion while wedging said circumferential teeth together and converting radial preload to high axial preload.