U.S. patent application number 09/846014 was filed with the patent office on 2001-10-25 for pipe weld alignment system.
Invention is credited to Baugh, Benton F..
Application Number | 20010033773 09/846014 |
Document ID | / |
Family ID | 26769972 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010033773 |
Kind Code |
A1 |
Baugh, Benton F. |
October 25, 2001 |
Pipe weld alignment system
Abstract
An apparatus for deploying pipe string is disclosed. The
apparatus comprises a mast; an articulated stationary table to
which the mast is affixed; a stinger affixed to the stationary
table to articulate with the mast; and a pipe erector operatively
connected to the mast.
Inventors: |
Baugh, Benton F.; (Houston,
TX) |
Correspondence
Address: |
Richard C. Auchterlonie
Howrey Simon Arnold & White, LLP
750 Bering Drive
Houston
TX
77057-2198
US
|
Family ID: |
26769972 |
Appl. No.: |
09/846014 |
Filed: |
April 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09846014 |
Apr 30, 2001 |
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09301751 |
Apr 29, 1999 |
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6273643 |
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60083964 |
May 1, 1998 |
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Current U.S.
Class: |
405/166 ;
405/168.1; 405/170; 405/177 |
Current CPC
Class: |
F16L 1/19 20130101; F16L
1/207 20130101; F16L 1/225 20130101; F16L 1/235 20130101; B63B
35/03 20130101 |
Class at
Publication: |
405/166 ;
405/170; 405/168.1; 405/177 |
International
Class: |
F16L 001/12 |
Claims
What is claimed:
1. An apparatus for deploying pipe string, the apparatus
comprising: a mast; an articulated stationary table to which the
mast is affixed; a stinger affixed to the stationary table to
articulate with the mast; and a pipe erector operatively connected
to the mast.
2. The apparatus of claim 1, further comprising: a main skid frame
defining with the stationary table an articulated joint; a
traveling table providing freedom of movement in at least one
direction.
3. The apparatus of claim 2, wherein the articulated joint provides
freedom of movement in three degrees.
4. The apparatus of claim 2, wherein the articulated joint
includes: a spherical bearing rotatable about three primary axes,
and translatable vertically at its outer diameter within a
cylindrical tube rigidly connected to the main skid frame, the
inner diameter of the bearing encircling and reciprocating on the
outer diameter of the stinger base tube, which is rigidly fixed to
the bottom surface of the stationary table; and a plurality of
jacks spaced apart about the stinger base tube between the skid
frame and the stationary table.
5. The apparatus of claim 4, wherein the jacks mechanically convert
rotary motion of a gear drive into linear vertical translation of
the jack center post to tilt the stationary table to the desired
angular orientation.
6. The apparatus of claim 2, wherein the mast includes hydraulic
means for articulating the mast.
7. The apparatus of claim 2, wherein the at least one direction is
along a central axis of the mast.
8. The apparatus of claim 2, wherein the traveling table is
actuated by at least one hydraulic means for actuating the
traveling table.
9. The apparatus of claim 2, wherein the traveling table includes a
clamp for gripping the pipe string.
10. The apparatus of claim 1, wherein the stinger includes a base
tube affixed to the stationary table and an extension affixed to
the base tube.
11. The apparatus of claim 1, wherein the pipe erector is hinged to
the stationary table to form the operative connection.
12. The apparatus of claim 2, wherein the pipe erector is
rotationally attached to the stationary table through one degree of
freedom of movement such that the pipe erector 25 tracks the mast's
movement.
13. The apparatus of claim 1, farther including a bootstrap
mechanism for assembling the apparatus.
14. The apparatus of claim 1, further comprising a pipe weld
alignment mechanism.
15. An articulated joint for use in deploying a pipe string,
comprising: a stationary table; a plurality of means for moving the
stationary table; a stinger.
16. A pipe string, comprising: at least one pipe joint; a J-lay
collar; and a double collar.
17. An articulated apparatus for laying a pipeline on the seabed,
the apparatus comprising: a main skid frame; a stationary table
attached to the main skid frame via an articulated joint with at
least four degrees of freedom; a mast erected upon, and rigidly
attached to, the top surface of the stationary table; a traveling
table with one degree of freedom actuated by hydraulic means and
equipped with a pipe clamp device for gripping the riser (via a
double collar) during alignment, assembly and deployment
operations; a hydraulic means integrated into the mast structure
and interposed between the stationary table and the traveling
table; a stinger rigidly attached to the bottom surface of the
stationary table; and a pipe erector hinged to the stationary table
at the foot of the mast.
18. The articulated joint of claim 17, further comprising the
mechanical means necessary to allow the stationary table to rotate
azimuthally and angularly to meet the preferred lay angle of the
pipe string being deployed.
19. The articulated joint of claim 18, wherein the mechanical means
consisting of: a spherical bearing rotatable about three primary
axes and translatable vertically at its outer diameter within a
cylindrical tube rigidly connected to the main skid frame, the
inner diameter of the bearing encircling and reciprocating on the
outer diameter of the stinger base tube, which is rigidly fixed to
the bottom surface of the stationary table; and a plurality of
jacks spaced apart about the stinger base tube between the skid
frame and the stationary table.
20. The apparatus of claim 19, wherein the jacks mechanically
convert rotary motion of a gear drive into linear vertical
translation of the jack center post to tilt the stationary table to
the desired angular orientation.
21. The apparatus of claim 17, wherein the four degrees of freedom
include at least one of rotation about all three primary axes and
translation along the mast centerline.
22. The apparatus of claim 17, wherein the one degree of freedom is
along the central axis of the mast.
23. The apparatus of claim 17, wherein the stinger further
comprises: a base tube and an extension.
24. A pipe joint for assembly into a pipe string, the pipe joint
comprising: a pipe length including weld preparations at both ends;
a J-Lay collar affixed to one end of the pipe joint, the J-Lay
collar configured to interface with the interior surface of a
double collar during assembly.
25. A split double collar, hinged on one side and pinned on the
other; for gripping and bearing loads at the upper and lower ends
of a pipe joint during integration into a pipe string, wherein: the
interior surface of the collar interfaces with a J-Lay collar on
the pipe joint; and the exterior surface of the collar provides
multiple landing surfaces at different radii interfacing with the
clamp of a traveling table and a split bushing at a stationary
table.
26. A pipe erector actuated by cable and pneumatic means in one
plane with one degree of freedom and rotationally attached to the
stationary table, the erector automatically following a mast to
deliver a pipe joint to the mast center line regardless of the mast
orientation relative to the horizontal.
27. The pipe erector of claim 26, wherein the erector is hinged to
the same surface to which the mast is rigidly affixed.
28. A pipe weld alignment system acting in conjunction with a pipe
clamp at a traveling table to accurately align the weld prep
surfaces of a pipe joint for assembly, the weld alignment system
comprising two sets of hydraulically actuated rollers.
29. The pipe weld alignment system of claim 28, wherein one of the
rollers is near the middle of the pipe and the other near the
bottom.
30. The pipe weld alignment system of claim 28, wherein the rollers
are manually controlled by an operator standing on the stationary
table.
31. The pipe weld alignment system of claim 28, wherein set
includes four rollers, each with its own hydraulic cylinder.
32. A swivel bearing for hanging a pipe string during operations,
the swivel bearing comprising: a non-turning body affixed to the
pipe string: a turning body; a plurality of means for bearing
forces between the non-turning body and the turning body.
33. The swivel bearing of claim 32, wherein the means for bearing
forces is a plurality of zylan coated bearing rings interposed
between the non-turning body and the turning as body.
34. A swivel bearing for hanging a pipe string to permit a pipe lay
vessel to maneuver about the pipe string without inducing torque
thereon.
35. The swivel bearing of claim 34, wherein the swivel bearing
comprises: a non-turning body affixed to the pipe string: a turning
body; a plurality of means for bearing forces between the
non-turning body and the turning body.
36. The swivel bearing of claim 35, wherein the means for bearing
forces is a plurality of zylan coated bearing rings interposed
between the non-turning body and the turning body.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of provisional
application 60/083,964 filed May 1, 1998, incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to laying underwater pipe
and, more particularly, to installing underwater pipelines on the
seabed and/or connecting the same to floating terminals at the
surface.
[0004] 2. Description of the Related Art
[0005] Floating production facilities require risers to provide
fluid conduits between subsea equipment and the surface facility
(or platform). The floating structure responds dynamically to the
forces of the environment to which it is exposed. This means that
the conduit connecting the structure and subsea equipment must be
connected in a manner that accommodates relative motions. The
conduit, of course, requires top and bottom interfaces to establish
functional connections. At one time, flexible pipe was considered
as the only feasible means of providing flowline connections from
equipment on the sea bed to a floating production vessel. However,
flexible pipe is very expensive, much more so than standard steel
pipe. As a result, the use of steel pipe in deep water risers was
developed as an alternative means of achieving the sea bed
connection. This presented the practical problem of how to deploy a
steel pipe string vertically from a starting point on the ocean
floor to a hand-off and terminus at a floating production system;
thereby leading to the development and use of J-Lay towers for this
purpose.
[0006] The assembly and deployment of subsea steel pipelines from
floating vessels usually employs a J-Lay tower, especially in deep
water. The J-Lay tower provides a vertical, or nearly vertical,
platform for welding lengths of pipe into a pipe string. The J-Lay
tower tension feeds the pipe string from an anchor on the seabed.
Prepared lengths of pipe, known as "pipe joints," are fed one at a
time into the J-Lay tower and welded together to form the pipe
string. The angle at which the assembled pipe string leaves the
vessel to enter the water is controlled by the angle and azimuth of
the tower mast and "stinger," which is an inverted structure
pointing down into the water underneath the J-Lay tower, relative
to the pipe string being deployed.
[0007] Previous J-Lay tower installations have employed vertical
masts rigidly installed on pipe lay vessels. These installations
utilized pipe tensioners integrated into the mast for control of
the pipe string during deployment and hand-off operations. J-Lay
towers have been manufactured with the ability to lower pipe
straight down, or with an angle provided by a cone shaped stinger.
Other towers have been installed at a fixed angle to allow a
departure from the base at an approximation of the best average
departure direction. Any angular departure of the pipeline from
purely vertical in the first case or from the preset pipe angle in
the second case would cause the pipeline to be bent around the
stinger. Also, most current stingers employ a static, fixed
structure that imposes either cylindrical or conical shaped
excursion boundaries on the emerging pipe string.
[0008] Rigidly installed, vertical towers engender a number of
problems caused by an inability to respond in real time to the
dynamic forces encountered during pipe laying operations. For
instance, welding and assembly operations are performed at the
working floor on pipe with a substantial imposed moment. Other
deficiencies include the fact that they do not allow: 1) control of
the bending stress and tension within the pipe string as it is
deployed in an arc to the sea bed; 2) the laying vessel to weather
vane or rotate about the pipe and thereby prevent torsional wind-up
of the pipe string; and 3) precise control of the pipe lay
envelope. Further, current J-Lay tower designs omit any means for
precise and accurate alignment of the pipe string and new pipe
joints during the welding process. Current methods for deploying
pipe also encounter problems not directly associated with the use
of rigidly installed, vertical towers. None efficiently and/or
automatically feed pipe joints into the tower or align the pipe
joints with the tower center line to facilitate assembling the pipe
string 12.
[0009] Current stinger designs have a problem in that the internal
geometry of the stinger is usually fixed at the diameter of the
pipe string being deployed. In order to allow the passage of large
diameter packages integrated into the pipe string, the stinger must
be dismantled or removed from around the hanging pipe string.
Additionally, such stingers only act as guide conduits for the pipe
and do not stabilize, i.e., control the alignment of, the pipe as
it emerges from the weld floor.
[0010] The present invention is directed to overcoming, or at least
reducing the effects of, one or more of the problems set forth
above.
SUMMARY OF THE INVENTION
[0011] An apparatus for deploying pipe string is disclosed. The
apparatus comprises a mast; an articulated stationary table to
which the mast is affixed; a stinger affixed to the stationary
table to articulate with the mast; and a pipe erector operatively
connected to the mast.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Other objects and advantages of the invention will become
apparent upon reading the following detailed description and upon
reference to the drawings in which:
[0013] FIG. 1 illustrates one embodiment of an apparatus for
assembling and deploying pipe string underwater, the apparatus
constructed and operated in accordance with the present
invention;
[0014] FIGS. 2-5 illustrate an individual pipe joint and parts used
to prepare the pipe joint to be incorporated into a pipe string as
may be deployed by the embodiment of FIG. 1;
[0015] FIG. 6 is a conceptualized perspective view of part of the
tower system 10 of the embodiment in FIG. 1;
[0016] FIG. 7 is a partial cross-sectional, side view of part of
the tower system 10 of the embodiment in FIG. 1;
[0017] FIG. 8 is a partial cross-sectional view of a part of the
embodiment of FIG. 1;
[0018] FIGS. 9-12 illustrate, in various views, the clamping system
of the embodiment of FIG. 1;
[0019] FIGS. 13A-13B illustrate the swivel bearing of the
embodiment in FIG. 1;
[0020] FIG. 14 is a partial cross-sectional, side view of a screw
jack as employed in the articulating joint of FIG. 1;
[0021] FIG. 15 illustrates the stinger of the embodiment of FIG.
1;
[0022] FIGS. 16A-C illustrate the erector system of the embodiment
of FIG. 1;
[0023] FIGS. 17A-B illustrate the weld alignment and placement
system in the embodiment of FIG. 1;
[0024] FIGS. 18-20 illustrate a bootstrap mechanism as may be used
in some alternative embodiments to erect the articulated tower in
FIG. 1;
[0025] FIG. 21 illustrates how the stinger of FIG. 1 controls the
deployment of the pipe string; and
[0026] FIGS. 22-25 illustrate how the invention may be employed in
several pipe laying operations.
[0027] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof have been shown
by way of example in the drawings and are herein described in
detail. It should be understood, however, that the description
herein of specific embodiments is not intended to limit the
invention to the particular forms disclosed, but on the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0028] Illustrative embodiments of the invention are described
below. In the interest of clarity, not all features of an actual
implementation are described in this specification. It will of
course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions must be made
to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which will vary
from one implementation to another. Moreover, it will be
appreciated that such a development effort, even if complex and
time-consuming, would be a routine undertaking for those of
ordinary skill in the art having the benefit of this
disclosure.
[0029] FIG. 1 illustrates an apparatus 10 as may be used in various
embodiments to deploy a pipe string 12 beneath the surface of a
body of water 14 from a vessel 16. Note that, although this
disclosure is frequently in terms of subsea operations, it is to be
understood that the invention is not limited to oceanic or maritime
applications. The invention may be employed with any large body of
water including, but not limited to, oceans, seas, gulfs, and
lakes. The apparatus 10 is articulated as set forth in more detail
below and may be used to deploy the pipe string 12 for a variety of
purposes. Exemplary purposes include installing pipelines on the
seabed (not shown) and deploying risers between a pipe string 12
(also not shown) on the seabed and the vessel 16. As those in the
art will recognize, the term "pipe string 12" refers to a plurality
of pipe joints 17, or pieces of pipe, affixed together and, thus,
may generically be used to refer to pipelines and risers.
[0030] The particular embodiment of the apparatus 10 illustrated in
FIG. 1 is a tower system 10 and generally comprises an mast 15, a
stinger 20, and a pipe erector 25, all of which are articulated.
Generally, a prepared pipe joint 17 is loaded onto a pipe erector
25, which then loads it into the mast 15. Once loaded, the pipe
joint 17 is then affixed to the end of the pipe string 12,
whereupon it becomes a constituent part of the pipe string 12. The
pipe string 12 can then be further deployed through the stinger 20
and the mast 15. The pipe joints 17, apparatus 10, and the method
of using the apparatus 10 just now generally described are set
forth in greater detail below.
[0031] The pipe string 12 comprises a plurality of pipe joints 17.
Each pipe joint 17 comprises an individual pipe length 36, shown in
FIG. 2, which will be assembled (via welding) into the deployed
pipe string 12. Each pipe length 36 is prepared for assembly by
machining weld prep surfaces 35 at each end of the pipe length 36.
A J-Lay collar 38, such as that shown in cross-section in FIG. 3,
is welded to the upper end 40 of each pipe length 36. The pipe
joints 17 are then painted with a corrosion protection system in a
manner commonly known in the art. A double collar 42, shown in
FIGS. 4-5, is then affixed to the pipe joint 17 around the J-lay
collar 38 as shown in FIG. 8. The double collar 42 is a temporary
split collar with multiple landing surfaces at differing diameters.
It is used to secure the individual pipe joints 17 and the pipe
string 12 at various stages in the assembly and deployment sequence
as set forth below.
[0032] Turning now to FIG. 6 and to FIG. 7, a part of one
particular embodiment for the mast 15 of FIG. 1 is shown. The
embodiment includes a mast 15 joined to a main skid frame 22
through an articulated joint 24. The tower mast 15 includes a
traveling table 26, a pair of hydraulic cylinders 28, and a
stationary table 30. The mast 15 and stationary table 30 also rest
upon and are connected to a plurality of screwjacks 32.
[0033] The mast 15 is a three-part, welded, steel truss structure
18 mounted to the top surface 21 of the stationary table 30. It
supports two very large, hydraulic lifting cylinders 28 (with
500,000 lbs. lift capacity each), the traveling table 26, the pipe
clamping system 44 shown in FIGS. 10-12, and the weld alignment
system 46 shown in FIGS. 17A-17B. Returning to FIG. 2 and to FIG.
3, the hydraulic cylinders 28 provide the vertical lift and
tensioning capability on the pipe string 12. Multiple wire ropes
(not shown) tied to the base of the cylinders 28 at the stationary
table 30 run over sheaves (also not shown) mounted at the top of
the hydraulic cylinders 28 to the traveling table 26. This
arrangement effectively multiplies the cylinder stroke and doubles
the vertical movement of the traveling table 26. The mast 15 acts
as the guide mechanism for vertical movement of the traveling table
26. It also mounts the two centralizing units 48 discussed below
that center the pipe joint 17 and straighten it prior to welding at
the lower end as discussed further below.
[0034] The main skid frame 22 is a welded plate structure designed
to support the entire tower system 10 via the stationary table 30
and all associated equipment. It provides the interface with the
deck 34 of the vessel 16 and distributes the system loads over a
large area of the deck 34.
[0035] Referring now to FIG. 7 and to FIG. 8, the stationary table
30 is a welded steel plate structure with a 62.0" diameter hole 52
at its center for riser deployment. The stationary table 30
provides a common rigid interface for the mast 15, stinger 20, and
erector 25. It is supported by three screw jacks 54 and a gimbaled
bearing 50 which are installed on the main skid frame 22. A 62.0"
bowl 58 is permanently installed in the riser hole 52 of the
stationary table 30. A 62.0" split bushing 60 is nested inside the
bowl 58. A 26.0" bushing 62 is, in turn, installed in the 62.0"
bushing 60. The 26.0" bushing 62 supports the pipe string 12 (via
the temporary double collar 48 on the last pipe joint 17 in the
pipe string 12) while the next pipe joint 17 is being welded in
place.
[0036] Turning now to FIGS. 9-12, the traveling table 26 is a
welded steel plate structure powered by the twin lifting cylinders
28 (shown in FIG. 2). It receives the top ends of the pipe joints
17 as they are lifted from the horizontal by the erector 25. A
split clamp 44 installed on the traveling table 26 secures the end
of the pipe joint 17 (around a temporary double collar 42) and
holds it in place while the pipe joint 17 is aligned by the mast 15
centralizing units 48 in preparation for welding at the lower end.
The traveling table 26 supports the swivel bearing 65, shown in
FIGS. 13A-13B, when in use, the swivel bearing 65 being inserted
between the double collar 42 and the split clamp 44. Note that FIG.
13B is a split view drawing, presenting View A wherein the swivel
bearing 65 is inserted into the traveling table 26 and View B
wherein the traveling table 26 is shown without the swivel bearing
65.
[0037] Referring now to FIG. 13A, the swivel bearing 65 is a
mechanical bearing consisting of a turning body 66 and a
non-turning body 68 with multiple, compression loaded, zylan
coated, shear rings 70 interposed between them. The turning body 66
interfaces and supports the double collar 42; the non-turning body
68 interfaces with the split clamp 44 on the floor of the traveling
table 26. The shear rings 70 shear relative to one another in order
to accommodate the differential motion between the turning body 66
and the non-turning body 68.
[0038] When needed, the swivel bearing 65 is inserted at the
traveling table 26 as shown in FIG. 13B and carries the weight of
the pipe string 12 during vessel 16 turning operations and heading
adjustments. The bearing swivel 65 provides a rotating interface
between the pipe string 12 and the mast 15. The bearing swivel 65
also has numerous applications other than that disclosed above. For
instance, the bearing swivel 65 might be used in many other
applications requiring torsional isolation within a system without
interrupting load path continuity and a high load capacity.
[0039] Referring once again to FIG. 7, the stationary table 30 and
the main skid frame 22 define the articulated joint 24 employing a
spherical bearing 72 and a plurality of screw jacks 54. The
interface between the stationary table 30 and the main skid frame
22 consists of the 62.0" spherical metal bearing 72 that is free to
move up and down within a cylindrical bore 74. Thus, the
articulated joint 24 in this embodiment is a ball joint. The
spherical bearing 72 encircles (and is welded to) the stinger base
tube 76, which is, in turn, bolted to the stationary table 30. This
articulated interface reacts all radial loads within the system.
Three screw jacks 54 are arrayed at 120.degree. intervals about the
articulated joint 24 and tilt the mast 15 up to 15.degree. off
vertical on any azimuth. The screw jacks 54 react all vertical
loads in the system.
[0040] FIG. 14 illustrates a representative one of the screw jacks
54. The screw jack 54 is a mechanical jack driven by a hydraulic
motor 78 via a worm gear 80. The nested inner and outer members 82,
84 of the jack 54 have a common threaded interface. Rotation of the
inner member 82 in either direction causes the outer member 84 to
reciprocate along the common central axis 86. The top of each jack
54 is capped with a secondary articulated joint 90 consisting of a
spherical surface 88 and a lateral slide plate 92 arranged
back-to-back within a common housing 94. These secondary
articulated joints 90 provide compensation for radial adjustments
caused by tilting the mast 15, and their position below the
articulated joint 24 protects the jacks 54 from side loads.
[0041] Thus, changes in deployment angle may be made during pipe
laying operations responsive to changing conditions. This is
accomplished by actuating the screw jacks 54, which are controlled
from the operator's panel on the stationary table 30. The spherical
ball joint 90, which is held captive radially by the cylindrical
housing 93, is free to pivot and to reciprocate responsive to the
changing angular orientation of the stinger base tube 76.
Conversely, the base tube 76, as discussed below, is rigidly
affixed to the stationary table 30 and, hence, moves in response to
angular change in the orientation of the stationary table 30.
[0042] The stinger 20, as illustrated in FIG. 15, is a welded steel
structure attached to the bottom of the stationary table 30 on the
same central axis as the mast 15. It is flanged and bolted together
in two sections; the base tube 76 and the extension 96. The stinger
extension 96 houses a series of hydraulically driven rollers 98. In
the particular embodiment illustrated, there are rollers 98 at six
different locations 100, with four rollers 98 per location. The
rollers 98 secure the pipe string 12 and assure that it does not
violate the predetermined minimum bend radius during pipe lay
operations. The bore 102 of the stinger 20 and the stationary table
30 above are large enough to allow passage of a flexible joint or
other package (not shown) for deployment or retrieval. Cameras and
lights 104 for monitoring the pipe string 12 are deployed at the
bottom of the stinger 20. The hydraulically driven rollers 98 of
the stinger 20 are hinged at the outer diameter of the stinger
frame, i.e., the stinger extension 96. This feature allows the
rollers 98 to be folded up out of the way, thereby allowing the
passage of large diameter packages that are sometimes integrated
into the pipe string 12 during deployment.
[0043] Also, the stinger 20 features two top roller stabilizer
stations 140 that stabilize the pipe string 12 as it emerges from
the underneath the weld floor, which in the particular embodiment
illustrated is the stationary table 30. The rollers 98 of the riser
stabilizer stations 140 keep the top pipe joint 17 of the pipe
string 12 aligned with the weld position to help prevent the
introduction of bending moments at the weld site. The subsequent
curvature of the pipe string 12 is controlled by the bottom four
riser curvature stations 142, which permit gradually wider
excursions from the installation center line as described
below.
[0044] Although the stinger 20 is disclosed herein in conjunction
with the mast 15, this aspect of the present invention is not so
limited. The stinger 20 may be used in virtually all subsea pipe
laying activities to control critical bending stress in the pipe
string 12 both as to the weld floor above and in the deployed pipe
string 12 below. The stinger 20 may also be employed for a large
range of pipe diameters without the need for reconfiguration or
removal.
[0045] The pipe erector 25, shown best in FIG. 16A, is fastened to
the stationary table 30 by a hinge 27 at the base of the mast 15 as
shown in FIG. 6 and is actuated by a cable 106 and hydraulic winch
(not shown). Returning to FIG. 16A, the pipe erector 25 is shown in
a horizontal position 108, an intermediate position 110, and a
vertical position 112. It receives the prepped pipe joints 17 one
at a time as they are off-loaded from the pipe rack (not shown) by
the jib crane 112 while the pipe erector 25 is in the horizontal
position 108. Bi-axial rollers (not shown) are incorporated into
the erector 25 to allow orientation of the pipe ends and match
marks as required. Hydraulically operated clamps 114 secure the
pipe joint 17 to the pipe erector 25 as it lifts them through the
intermediate position 110 to the vertical position 112 over the
pipe string 12 for insertion into the pipe alignment system 46
prior to make-up with the pipe string 12.
[0046] The pipe alignment system 46 includes two centralizing units
48, best shown in FIG. 17, mounted in the mast 15 of the mast 15.
Each centralizing unit 48 consists of four hydraulic cylinders 116,
each driving a pinned cam 118 with a flat face 120. The flat face
120 on each cam 118 interfaces with the pipe joint 17 and applies
the force of the corresponding cylinder thereto (multiplied by the
eccentric geometry of the pinned cam 118). The centralizing units
48 are mounted in the mast 15 located at two different positions
along the length of the pipe joint 17. The hydraulic cylinders 116
are manually activated by an operator (standing at the stationary
table 30) in order to visually align the weld preps 40 of the pipe
joint 17 for welding. The lower centralizing unit 48 aligns the
pipe joint 17 radially and the upper centralizing unit 48,
nominally located at the middle of the pipe joint 17, is used to
correct angular mismatch of the weld preparations 40.
[0047] The pipe erector system is therefore capable of
automatically feeding pipe into the mast 15. The erector 25 assures
that the pipe joint 17 is aligned with the centerline of the mast
15 regardless of the angle of the mast 15 relative to the deck 34
of the vessel 16. This is principally accomplished by centering the
erector 25 on the mast 15 and hinging it at the base thereof. Since
the mast 15 and the erector 25 are attached to the same surface,
i.e., the stationary table 30, correct angular alignment of the
erector 25 is assured.
[0048] Thus, in the particular embodiment illustrated, the
apparatus 10 comprises the mast 15, the stinger 20 affixed to the
stationary table 30 to articulate therewith, and the pipe erector
25 operatively connected to the stationary table 30 and the mast
15. The mast 15 includes the main skid frame 22; a stationary table
30, the stationary table 30 defining with the main skid frame 22
the articulated joint 24; the mast 15 rigidly affixed to and
extending upwardly from the stationary table 30; and the traveling
table 26, which provides freedom of movement in at least one
direction, that being along the central axis of the mast 15. The
articulated tower 10 provides freedom of movement in four degrees,
including rotation about three primary axes and translation along a
centerline of the mast 15.
[0049] The tower system 10 may be assembled at the site where the
pipe string 12 is to be deployed. The main skid frame 22, mast 15
components, stinger 20 components, and all other parts are shipped
as separate pieces. At the installation site on the vessel 16 of
choice, they are reassembled and erected for operation. First, all
components and support items (power skid, welding pallet, etc.) are
laid out on the deck 34 of the vessel 16 in the order of assembly
and use. Next, the main skid assembly including the main skid frame
22, stationary table 30, jacks 54, and articulated joint 24 are
landed in the position for laying the flowlines. The stinger 20 is
keelhauled to a position below the main skid 22 and bolted to the
bottom of the bearing swivel into 54, which is rigidly attached to
the bottom of the stationary table 30 as discussed above. The
stationary table 30 is rotated to the full stop position to the
rear to allow a stop shoulder (not shown) to be engaged in the
articulated section against the frame.
[0050] Mast support jigs (also not shown) are then attached to the
top of the main skid 22 and the pieces of the mast 15 are assembled
to the stationary table 30 on the jigs. Returning to FIG. 1, the
lower section 122 of the mast 15 will be in three pieces--two
sides, a cylinder, and a center (or back) section. The middle
section 124 of the mast 15 will include three similar pieces,
without the cylinders. The top section 126 of the mast 15 will be
installed as a single piece.
[0051] In order to facilitate erection and take-down of the mast
15, a mast erector system, or bootstrap mechanism, 128, best shown
in FIGS. 18-20, may be used. The assembly of a tower system, such
as the mast 15, is frequently hampered by the lack of a crane tall
enough to lift and move the tower on board the vessel. The boot
strap mechanism 128 addresses this problem. The boot strap
mechanism 128 includes a steel radius frame 130 with multiple chain
guides 131 is, in this particular embodiment, temporarily installed
on the stationary table 30. A heavy duty link chain 132, shown in
FIG. 20, running over the radius frame 130 is attached to the
traveling table 26 and, via the radius frame 130, to the stationary
table 30.
[0052] The mast 15 is then erected using the boot strap mechanism
128. Pressurization of the two main mast cylinders 28 actuates the
traveling table 26 which, in turn, tensions the chains 132 and
pulls the assembled mast 15 erect (the mast 15 rotates around the
hinge line at the front legs). The back legs of the mast 15 and the
base of the cylinders 28 are then bolted in place on the stationary
table 30. The jacks are then used to bring the mast 15 to the
vertical position.
[0053] Next, the pipe erector 25 is installed on its hinge line
(not shown) on the stationary table 30 in front of the mast 15. The
erector 25 is then connected to its actuation cable 106 and winch
(not shown) and the hold back winch (also not shown). All
peripheral facilities such as the pipe rack (not shown) and skids
(not shown) containing the coating equipment and QC/QA equipment
are positioned. All electrical, pneumatic and hydraulic hook-ups
are completed and tested.
[0054] Once assembly is complete, prepped pipe joints 17 are
arranged on the pipe rack (not shown) in the order of installation.
A temporary double collar 42 is installed around the J-Lay collar
38 on each pipe joint 17 either prior to placement in the pipe
erector 25 or while in the erector 25, at the operator's
discretion.
[0055] Next, the pipe joint 17 is placed in the cradle with a jib
crane 112 using hydraulic tongs 113, shown in FIGS. 16B-C, designed
to handle the pipe joints 17. The pipe joints 17 are positioned by
the jib crane 112 within the clamps 114 of the erector 25 and
between the position markings (not shown) on the erector 25. Once
the pipe joint 17 is properly positioned and secured in the erector
25, the erector 25 is activated and rotates upward towards the mast
15 to the vertical position 112, at whatever angle the mast 15 is
presently positioned.
[0056] As the top of the pipe joint 17 arrives at the vertical
position 110, the upper end with the double collar 42 is gripped in
the split clamp 44 on the traveling table 26 and the lower length
is gripped by two the pipe centralizing units 48. The split clamp
44 grips the upper landing surface 134 of the double collar 42; the
lower landing surface 136 being reserved for use when the pipe
joint 17 is lowered to the second position at the stationary table
30. The erector clamps 114 are then released and the erector 25 is
retracted back down to the horizontal position 108 beside the pipe
rack.
[0057] The hydraulic cylinders 118 of the centralizing units 48 are
then manually activated by an operator standing at the stationary
table 30 to align the pipe joint 17 weld preps for welding. The
lower centralizing unit 48 aligns the pipe joint 17 radially and
the upper centralizing unit 48, at the middle of the pipe joint 17,
corrects any angular mismatch of the weld preparations. The pipe
joint 17 is then welded onto the pipe string 12 and the weld
inspected in accord with techniques well known in the art.
[0058] After welding and inspection, the mast cylinders 28 lift the
pipe string 12 slightly so that the double collar 42 on the lower
pipe joint 17 (at the stationary table 30) can be removed. Once the
double collar 42 is removed from the lower pipe joint 17, the
traveling table 26 is lowered and the double collar 42 on the top
pipe joint 17 is seated at its bottom landing surface 136 in the
nested bushings 60, 62 and split bowl 58 installed in the riser
hole 52.
[0059] As the pipe string 12 descends below the stationary table
30, it passes through base tube 76 and the extension 96 of the
stinger 20, the extension 96 being swivel mounted via the swivel
bearing 65. The stinger 20, as earlier mentioned, is equipped with
six stages 100 of hydraulically actuated rollers 98. The top two
sets 140 of rollers 98 keep the pipe string 12 aligned with the
centerline of the pipe joint 17 currently being installed. The
subsequent curvature of the descending pipe string 12 is controlled
by the bottom four sets 142 of rollers 98, which permit gradually
wider excursions from the installation center line as shown in FIG.
21.
[0060] These steps may be repeated to lay a pipeline and establish
a riser from the pipe string 12. FIGS. 22-24 illustrate several
operations associated with a riser 145. More particularly, FIG. 22
illustrates transfer of the riser 145, FIG. 23 illustrates
termination of the riser 145, and FIG. 24 illustrates abandonment
of the riser 145.
[0061] Turning now to FIG. 22, after completing the riser 145 and a
flexible joint 147 is integrated into the riser string, a fishplate
148 is attached to the top of the flexible joint 147. An overhead
crane 150 on the lay vessel 16 is then connected via cable and
shackle (not shown) through the mast 15 to the fishplate
148/flexible joint 147 termination. The weight of the riser 145 is
then assumed by the crane 150. FIG. 25 illustrates the set-up of
the flexible joint 147 for these operations in greater detail.
[0062] Returning to FIG. 22, the crane 150 lowers the end of the
riser 145 to a location below the stinger 20 where a line 152 from
the receiving vessel 155 can be attached to the fishplate 148.
After attachment of the pull-in line 152 from the receiving vessel
155, the riser 145 is lowered to a depth which will allow it to be
safely traversed under the lay vessel 16. While the line from the
crane 150 is played out, the riser 145 is simultaneously reeled in
by the recipient vessel 155 as shown in FIG. 23. After clearing the
lay vessel 16, the riser string is pulled upward to a point where
the flexible joint 147 is above the receptacle (not shown) on the
recipient vessel 155. The flexible joint 147 is then lowered into
the receptacle until it is fully seated.
[0063] If the need for temporary riser abandonment occurs, then a
pipe string 158 of smaller dimensions (composed of standard
threaded drill pipe) will be attached to the riser 145 via a
special swiveling head 160 welded to the end of the riser 145. The
pipe string 158 is deployed through the mast 15 as was the pipe
string 12 in the manner described above. The drill pipe string 158
is played out so as to gradually lower the riser 145 to the seabed.
Once the riser 145 is laid on the seabed, the pipe string 158 is
disconnected and recovered.
[0064] The riser 145 may subsequently be recovered, as well.
Recovery of the riser 145 requires locating the end of the riser
145 via sonar and a remotely operated vehicle ("ROV") mounted TV
162, shown in FIG. 22 and reattaching the pipe string 158. The pipe
string 158 is then retrieved, pulling the end of the riser 145 up
from the seabed into the mast 15.
[0065] Thus, in the particular embodiment illustrated, the tower
system 10 provides the capability to lay both a welded pipeline and
a steel catenary riser ("SCR") off the side of a vessel 16 of
opportunity. To this end, the tower system 10 incorporates an
articulating joint in the mast 15 system 10 itself, interposes a
swiveling interface between the pipe string 12 and the mast 15, and
permits the mast 15 to articulate in response to varying current,
wind, and tidal forces encountered during pipe laying operations.
The mast 15 system 10 consequently permits rotation of the
stationary table 30 and, hence, the mast 15, stinger 20, and
erector 25, about all three primary axes and is capable of (1)
aligning itself both angularly and azimuthally with the pipe string
12 as it is deployed in order to attack the pipeline path, wind,
and current at the most favorable conditions; (2) maintaining riser
tension within a specified envelope: (3) permitting the laying
vessel 16 to rotate about the pipe string 12 as weather and
operational considerations dictate; and (4) allowing precise
control of the riser lay envelope.
[0066] The particular embodiments disclosed above are illustrative
only, as the invention may be modified and practiced in different
but equivalent manners apparent to those skilled in the art having
the benefit of the teachings herein. Furthermore, no limitations
are intended to the details of construction or design herein shown,
other than as described in the claims below. It is therefore
evident that the particular embodiments disclosed above may be
altered or modified and all such variations are considered within
the scope and spirit of the invention. Accordingly, the protection
sought herein is as set forth in the claims below.
* * * * *