U.S. patent number RE30,846 [Application Number 05/944,979] was granted by the patent office on 1982-01-12 for submarine pipeline laying vessel.
This patent grant is currently assigned to Santa Fe International Corporation. Invention is credited to Alexander C. Lang, Peter A. Lunde.
United States Patent |
RE30,846 |
Lang , et al. |
January 12, 1982 |
**Please see images for:
( Certificate of Correction ) ** |
Submarine pipeline laying vessel
Abstract
This invention relates to a method and to an apparatus for use
in laying a submarine pipeline from a pipe-laying vessel. According
to one aspect of the present invention, there is provided a reel
pipe-laying method for continuously laying a pipeline of up to
24-inch diameter without a stinger by (1) aligning a pipe portion
as it is being paid out from the reel, (2) straightening the
aligned pipe portion, (3) tensioning the pipe, (4) discharging the
straightened pipe under tension into the body of water, and (5)
changing for different water depths and pipe conditions the lift
off angle of the pipe relative to the horizontal by pivoting a
diverter about a horizontal pivot, the diverter supporting at least
the straightener and the tensioner and extending from the
horizontal pivot mounted near the aft end of the vessel, upwardly
toward the reel.
Inventors: |
Lang; Alexander C. (Henly on
Thames, GB2), Lunde; Peter A. (Houston, TX) |
Assignee: |
Santa Fe International
Corporation (Orange, CA)
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Family
ID: |
27076386 |
Appl.
No.: |
05/944,979 |
Filed: |
September 22, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
574433 |
May 5, 1975 |
03982402 |
Sep 28, 1976 |
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Current U.S.
Class: |
405/168.3;
405/168.4 |
Current CPC
Class: |
F16L
1/203 (20130101); B63B 35/03 (20130101) |
Current International
Class: |
B63B
35/00 (20060101); B63B 35/04 (20060101); F16L
1/12 (20060101); F16L 1/20 (20060101); F16L
001/00 (); B63B 035/04 (); B65H 075/00 () |
Field of
Search: |
;405/168,166,167,170,164
;72/161 ;247/78.7,54,157.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Taylor; Dennis L.
Attorney, Agent or Firm: LeBlanc, Nolan, Shur & Nies
Claims
What is claimed is:
1. A vessel for continuously laying a pipeline on the bed
underlying a body of water, comprising:
a pipe supply reel mounted for rotation on said vessel about .[.its
horizontal.]. .Iadd.a predetermined .Iaddend.axis;
drive means for rotating said reel .[.thereby unwinding a pipe
section.].;
a diverter structure having one end coupled to one end of said
vessel and having the other end extending upwardly in the direction
of said reel and at an acute angle relative to the deck of said
vessel; and pipe-conditioning means mounted on said diverter
structure for conditioning said pipe section and discharging the
conditioned pipe section into said body of water.
2. The vessel of claim 1 and further including:
pivot means mounted near said one end of said vessel for pivotably
mounting said one end of said diverter structure, and extensible
means mounted on said vessel and being operably coupled to said
diverter structure for pivoting said diverter structure about said
pivot means, whereby said pipe is discharged directly from said one
end of said vessel into said body of water.
3. The vessel of claim 2 and further including:
force-producing means positioned between said reel and said
diverter structure for maintaining the unwound pipe section in a
fixed vertical plane prior to and during the pipe conditioning.
4. The vessel of claim 3 wherein,
said reel comprises a hollow hub and a pair of vertically-disposed
side flanges secured to the opposite ends of said hub; and
drive means angularly disposed under at least one of said flanges
for rotating said reel.
5. A vessel for continuously laying a pipeline on the seabed
underlying a body of water, comprising:
a pipe supply reel mounted for rotation on said vessel about its
horizontal axis;
drive means for rotating the reel;
level winding means for level winding a pipe section as it is being
pulled from the reel;
aligning means for aligning the pipe into a desired single vertical
center plane;
straightening means for straightening the aligned pipe section;
diverter means;
said aligning means and said straightening means being mounted on
said diverter means, and said diverter means being pivotably
mounted on said vessel for changing the lift-off angle of the pipe
relative to the horizontal, whereby said aligning and straightening
means are positioned on and over the deck of said vessel; and
means for discharging the straightened pipe under tension into said
body of water at a desired lift-off angle.
6. The vessel of claim 5 wherein said aligning means are mounted on
said diverter means between said straightening means and said
reel.
7. The vessel of claim 6 and further including level-winding means
mounted near the reel to guide the pipe laterally across the reel
as the pipe is wound on and unwound from the reel.
8. The vessel of claim 7 and further including adjustable,
horizontal-force-producing means positioned near the aligning means
for maintaining the pipe in said vertical center plane prior to and
during the straightening of the pipe by said straightening means.
.Iadd. 9. A vessel for laying a pipeline on the bed underlying a
body of water, comprising:
a reel for carrying a continuous length of pipe spooled thereon
mounted on said vessel for rotation about a predetermined
rotational axis;
a diverter structure having one end portion mounted to said vessel
and its other end portion extending upwardly at an acute angle
relative to the deck of the vessel;
pipe conditioning means mounted on said diverter structure for
conditioning pipe after it is unspooled from said reel and for
discharging the conditioned pipe into said body of water; and
drive means for adjusting said diverter structure about its pivot
axis to thereby selectively control the angle of discharge of said
conditioned pipe into said body of water. .Iaddend..Iadd. 10. A
vessel according to claim 9, wherein said pipe conditioning means
comprises straightening means for bending the unspooled pipe to a
bending radius whose value is selected to substantially straighten
the pipe prior to its being discharged into the body of water.
.Iaddend..Iadd. 11. A vessel according to claim 10, further
including:
level winding means for guiding the pipe laterally across the reel
as the pipe is unwound from the reel to said pipe conditioning
means. .Iaddend. .Iadd. 12. A vessel according to claim 11, wherein
said level winding means is movable in a plane substantially normal
to the rotational axis of the reel as pipe is unwound from the
reel. .Iaddend..Iadd. 13. A vessel according to claim 9, wherein
said diverter structure is pivotably mounted adjacent one end
portion of said vessel; and said drive means comprises extensible
means mounted on said vessel and operably coupled to said diverter
structure for pivoting said diverter structure about said pivot
means to a desired elevation as determined by the depth of the body
of water and the diameter and size of the pipe. .Iaddend..Iadd. 14.
A vessel according to claim 13, wherein:
said reel comprises a hollow hub and a pair of vertically-disposed
side flanges secured to the opposite ends of said hub; and
further drive means are provided to cooperate with at least one of
said flanges for rotating said reel. .Iaddend..Iadd. 15. A vessel
according to claim 9, wherein said pipe conditioning means
comprises:
aligning means for aligning the pipe in a desired substantially
vertical plane; and
straightening means for straightening the aligned pipe section.
.Iaddend..Iadd. 16. A vessel according to claim 15, wherein said
diverter structure is pivotably mounted adjacent one end portion of
said vessel; and said drive means comprises extensible means
mounted on said vessel and operably coupled to said diverter
structure for pivoting said diverter structure about said pivot
means to a desired elevation as determined by the depth of the body
of water and the diameter and size of the pipe. .Iaddend..Iadd. 17.
A vessel according to claim 16, wherein said aligning means are
mounted on said diverter means between said straightening means and
said reel. .Iaddend..Iadd. 18. A vessel according to claim 17,
further including:
level-winding means for guiding the pipe laterally across the reel
as the pipe is wound on and unwound from the reel through said pipe
conditioning means. .Iaddend..Iadd. 19. A vessel for laying a
pipeline on the bed underlying a body of water, comprising:
a reel for carrying a continuous length of pipe spooled thereon
mounted on said vessel for rotating about a predetermined
rotational axis;
a diverter structure pivotably mounted to said vessel;
pipe conditioning means mounted on said diverter structure for
conditioning pipe after it is unspooled from said reel and for
discharging the conditioned pipe into said body of water, said pipe
conditioning means including aligning means for aligning the
unspooled pipe in desired plane, and straightening means for
plastically bending the unspooled pipe to a bending radius whose
value is selected to substantially straighten the pipe prior to its
being discharged into the body of water;
level-winding means for guiding the pipe laterally across the reel
as the pipe is unwound from the reel; and
drive means for pivoting said diverter structure about its pivot
axis to thereby selectively control the angle of discharge of said
conditioned pipe into said body of water. .Iaddend..Iadd. 20. A
vessel according to claim 19, wherein said level-winding means is
movable in a plane substantially normal to the rotational axis of
the reel as pipe is unwound from the reel. .Iaddend..Iadd. 21. A
vessel according to claim 19, wherein said diverter structure is
pivotably mounted adjacent one end portion of said vessel; and said
drive means comprises extensible means mounted on said vessel and
operably coupled to said diverter structure for pivoting said
diverter structure about said pivot means to a desired elevation as
determined by the depth of the body of water and the diameter and
size of the pipe. .Iaddend..Iadd. 22. A vessel according to claim
19, wherein said aligning means are mounted on said diverter means
between said straightening means and said reel. .Iaddend. .Iadd.
23. A vessel for laying a pipeline on the bed underlying a body of
water, comprising:
a reel for carrying a continuous length of pipe spooled thereon
mounted on said vessel for rotation about a predetermined
rotational axis;
a diverter structure pivotably mounted to said vessel;
pipe conditioning means mounted on said diverter structure for
conditioning pipe after it is unspooled from said reel and for
discharging the conditioned pipe into said body of water, said pipe
conditioning means including aligning means for aligning the
unspooled pipe in a desired plane, and straightening means for
plastically bending the unspooled pipe to a bending radius whose
value is selected to substantially straighten the pipe prior to its
being discharged into the body of water; and
drive means for pivoting said diverter structure about its pivot
axis to thereby selectively control the angle of discharge of said
conditioned pipe into said body of water. .Iaddend..Iadd. 24. A
vessel according to claim 23, wherein said diverter structure is
pivotably mounted adjacent one end portion of said vessel; and said
drive means comprises extensible means mounted on said vessel and
operably coupled to said diverter structure for pivoting said
diverter structure about said pivot means to a desired elevation as
determined by the depth of the body of water and the diameter and
size of the pipe. .Iaddend..Iadd. 25. A vessel according to claim
23, wherein said aligning means are mounted on said diverter means
between said straightening means and said reel. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The laying of long lines of metal pipe on the floor of deep waters
from a lay barge is gaining increasing commercial importance for
the transport of fluids, particularly petroleum and petroleum
products.
In one conventional, pipe-laying method, known as "stove-piping", a
pipeline is fabricated on the deck of a lay barge by welding
together individual lengths of pipe. Each length of pipe is about
40 feet long. In another conventional method, known as "the reel
pipe-laying technique" for laying relatively smaller diameter pipe,
a pipeline is wound on the hub of a large reel which is rotatably
mounted on the deck of the lay barge. The lay barge is then moved
to an offshore pipe-laying location and the pipeline is unwound
from the reel. The unwinding portion of the pipeline is
straightened prior to being lowered into the body of water. In both
of these techniques the departure angle of the pipe relative to the
barge is limited primarily due to the fixed location of the pipe
handling machinery mounted on the deck of the barge.
In either of these known pipe-laying methods, the lay barge is
required to have a long equipment ramp in a position fixed relative
to the barge. In one procedure there are mounted on the ramp a
plurality of longitudinally-spaced pipe supports, commonly known as
stanchions. The position of each stanchion is adjustable within a
small range to provide a desired pipe-descent trajectory which
gradually slopes downwardly. A particular trajectory is selected
for each diameter size of pipe, weight of pipe, pipe tension, and
depth of water. In another procedure the means of supporting the
pipe is what is commonly known as a "stinger", which is attached to
the aft end of the lay barge at the end of the long ramp. The
stinger supports the descending pipe span from the aft end of the
barge to a lift-off point on the stinger. From this lift-off point
the pipe span can safely sag to the seabed. The primary purpose of
the stinger is to avoid excessive concentrations of curvature
stress in the descending pipe span. These concentrations could
buckle or permanently bend the pipeline. Various types of pipe
stingers are known; some are straight and others have articulated
joints.
A straight stinger is usually a long, stiff structure. It comprises
two buoyant pontoons interconnected by numerous crossovers on which
are mounted horizontally and vertically disposed rollers. The
rollers support the pipe span as it moves from the barge's aft end
to the lift-off point. However, straight stingers have several
disadvantages, for example, significantly different water depths
require stingers of different lengths. The changing of stingers is
time-consuming. The length of a straight stinger is generally from
four to six times the water depth in which the pipeline is laid. In
practice, however, stingers have an upper length limit of about 600
feet. Such long stingers must be capable of withstanding high loads
caused by water currents and relative movement between the stinger
and the lay-barge. Stingers are therefore generally constructed
from high-strength materials, for example high-strength steel.
Some of the disadvantages of a straight stinger are avoided by
using a freely-articulated stinger consisting of several segments
connected in series by hinge joints. While a freely-articulated
stinger is designed to follow the curvature of the descending pipe
span, destructive concentrations of pipe curvature stress can occur
along the stinger, if the buoyancy of the segments is not correctly
distributed. Wave motions and pitching motions of the lay barge
tend to cause the stinger to rise and fall in high seas, thereby
making a pipe which extends between any two stinger segments very
vulnerable to buckling.
A semi-articulated stinger has been proposed as a compromise
between a freely-articulated stinger and a straight stinger. In the
semi-articulated stinger, the segments are connected with hinge
joints which permit a limited degree of vertical, lateral, and
torsional intersegment movement.
Stingers usually require a significant amount of time to install,
operate, and remove, especially during an impending storm or other
adverse operating conditions. If a stinger fails during
pipe-laying, the barge's down time can be great and the ensuing
financial loss considerable.
In practicing the conventional pipe-laying methods hereinbefore
described the pipeline moves over the deck of the lay barge in a
substantially horizontal plane. Long ramps are required on the lay
barges and frequently these ramps do not provide adequate space for
inspecting, testing and, if necessary, repairing the descending
pipeline. Also, workers find it difficult to maintain their
equilibrium on the ramp, especially in rough sea.
Proposals have been made to solve the "stinger problem" by
eliminating the stinger. But these proposals, as far as is known,
have been limited to the reel pipe-laying technique for up to 12
inch pipe, as described in U.S. Pat. No. 3,641,778, assigned to the
same assignee.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided
a reel pipe-laying method for continuously laying a pipeline
without a stinger by aligning a pipe section as it is being paid
out from the reel, straightening the aligned pipe, tensioning the
pipe, discharging the straightened pipe under tension into the body
of water, and changing the lift off angle of the pipe relative to
the horizontal by pivoting a diverter structure operably supporting
at least the straightener and tensioner, but preferably the aligner
as well. The diverter extends from a horizontal pivot, near the aft
end of the vessel, upwardly and inwardly toward the reel.
Generally, the lift-off angle of the straightened pipe relative to
the horizontal, i.e., the deck of the ship, and the tension applied
thereon are adjusted according to the depth of the body water into
which the pipeline is discharged, and to the size, strength and
weight of the pipe.
The present invention has the unique advantage for both small and
large diameter pipe in that lift off angles of up to 90.degree. can
be easily achieved under continuous pipe-laying operation.
The pipe-laying vessel has a pipe supply reel which is rotatably
mounted about a horizontal axis oriented athwartships. The reel is
comprised of a hollow hub, mounted on the ship for rotation about
its horizontal axis, and of vertically disposed side flanges
secured respectively about the opposite ends of the hub. Bearing
means are provided for rotatably supporting and centering the hub.
Drive means are circumferentially mounted about the bottom portions
of a flange for rotating the reel clockwise or
counterclockwise.
A diverter is provided for guiding a pipe section from its
orientation as it unwinds from the reel toward a downwardly
extending orientation, as the pipe is being guided between the reel
and the body of water. The diverter is pivotably mounted on and
preferably near the aft end of the vessel about a horizontal pivot
whereupon it extends over the vessel's deck in an upward direction
inclined toward the reel.
The diverter preferably comprises near its upper end a curved
aligner for changing the orientation of the pipe from its
orientation as it unwinds from the reel into a
downwardly-extending, vertical trajectory toward the body of water.
The aligner is followed by bending means for plastically
reverse-bending the pipe to a desired, preferably linear,
configuration after the pipe leaves the bending means. The bending
means may include or be followed by tension means for applying
tension to the pipe.
Advantageously, the aligner, the straightener, and the tensioner
are mounted on the diverter structure for pivotal movement
therewith. The straightener and tensioner can employ common
elements, all of which are preferably arranged to permit adjustable
angular and reciprocating movements therebetween.
A reel with the largest pipe storage capacity is ordinarily
employed. This requires a reel having a hub with a minimum outer
diameter determined so as not to adversely affect the largest
diameter pipe which will be coiled on the reel. The pipe is bent
around the reel's hub so that the maximum stress in at least a
portion of the pipe's metal wall exceeds the yield stress.
When a straight metal pipe is bent to a bending radius known as the
critical radius, the pipe is said to be at the limit between its
elastic or linear range and its plastic or non-linear range.
If a straight pipe is bent elastically, that is, so as not to
exceed its elastic range, no residual deformation or curvature
remains in the pipe after the applied bending moment is removed. A
straight pipe therefore is a pipe with zero curvature, or a pipe
bent to an infinite radius. For each steel grade and diameter size
pipe, there corresponds a critical bending radius whose value marks
the boundary between the pipe's elastic and plastic ranges.
In the pipe's plastic range, the stress-strain relationship is
non-linear. For a relatively small increase in bending moment
applied to the pipe, there is now obtained a relatively large
increase in curvature. A permanent residual curvature will now
remain after the release of an applied bending moment. If such a
permanent deformation is not objectionable, the pipe can be bent
plastically to a limit of the ultimate bending radius. If now the
bending radius is made smaller than the pipe's ultimate bending
radius, the pipe is likely to buckle and collapse.
For example, for a typical 8-inch diameter steel pipe whose steel
has a yield strength of 35,000 psi, the critical elastic bending
radius is about 308 feet. That is, if the pipe is bent to a radius
larger than 308 feet, there will remain no appreciable residual
curvature in the pipe upon the release of the bending moment. If it
is necessary to bend the same pipe to a radius considerably shorter
than 308 feet, the pipe's steel can be bent plastically, without
exceeding its ultimate bending moment, down to a radius of about 12
feet. If now the plastic bending moment is released, the pipe will
remain with a permanent residual curvature.
For each grade of steel and diameter size, the values of the
critical bending radius and of the ultimate plastic bending radius
can be experimentally and theoretically determined. Accordingly,
from a knowledge of such values, the necessary elements which are
to be mounted on the pivotable diverter structure can be designed
and controlled.
For a better understanding of the present invention and to show how
the same may be carried into effect, reference will now be made, by
way of example, to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view in elevation of a preferred embodiment
of an apparatus in accordance with the present invention; and
FIG. 2 is a plan view of the apparatus shown in FIG. 1.
Referring to the drawings, there is shown a pipe-laying ship 10
which supports a reel, generally designated as 12, on its deck 13.
The hub 15 of reel 12 is shown disposed for rotation about its
horizontal axis 11. Reel 12 stores a very long pipeline 14 which is
wound into a multi-layer coil 28. Each layer of pipe 30 in the
multilayer coil 28 has many windings. The reel is driven clockwise
or counterclockwise by a series of drive motors 19 operatively
coupled for applying a driving force to one of the flanges 21 of
the reel. When reel 12 is rotated clockwise, as viewed in FIG. 1,
there is obtained an unwound pipe section 16.
The pipe section 16, when emerging from the outermost layer 32, has
a relatively large radius of curvature and, conversely, when
emerging from the innermost layer 34 has a smaller radius of
curvature.
It has been found, contrary to what might be expected, that neither
the pipe nor its plastic coating, if any, generally become damaged
by the consecutive bending and reverse bending operations
contemplated by the method of this invention.
It is desired for reel 12 to have a maximum pipe storage capacity.
Hence, the diameter of hub 15 is selected so that even the largest
diameter, say 24 inch, pipe wound thereon will not be bent to a
radius shorter than its ultimate plastic bending radius, as
previously defined.
The unwound pipe section 16 therefore contains a permanent residual
curvature whose magnitude varies with the diameter of the layer in
the multi-layer coil 28 from which pipe section 16 emerges; with
the diameter, size, weight and strength of the pipe; with pipe
tension; and with the angle to which a pipe diverter structure 24
has been elevated.
An aligner, generally designated as 18, bends pipe 16 from a
generally horizontal direction to the desired downwardly extending
orientation. Aligner 18 has a sufficiently small uniform or
uniformly varying curvature to avoid buckling or damaging the pipe
and is mounted near the top end of the diverter structure 24 whose
bottom end is pivotably mounted for rotation about an athwartships
horizontal pivot 26. The diverter can be rotated in a clockwise or
counterclockwise direction and is supported at any selected angle
by conventional extensible means 27 in order to set the lift-off
angle A which is the angle between the descend trajectory of the
pipe and the horizontal.
The diverter 24 also includes a pipe straightener which is
generally designated as 20. Pipe section 16 enters the straightener
at a variable angle with respect to the horizontal and with a
variable residual curvature depending on the diameter of the layer
in the multilayer coil 28 from which pipe section 16 emerges. The
variable residual curvature also depends on the diameter, size,
weight and strength of the pipe, upon pipe tension, and upon the
angle A which the diverter has been elevated. Pipe straightener 20
plastically bends the pipe to a bending radius whose value is
selected so as to straighten the pipe.
The required diverter elevation is determined by the depth of the
body of water, the diameter and size of the pipe, the weight of the
pipe, and the tension in the pipe at the water surface.
Pipe 16 after it leaves aligner 18 at a point 48, has a non-uniform
residual stress distribution pattern relative to its longitudinal
axis and, hence, a variable residual curvature.
To remove this variable residual curvature from pipe 16,
straightener 20 is provided, for example, with a bending shoe 42
and a reaction shoe 44. Aligner 18 may serve as the other reaction
shoe. The bending shoe 42, the reaction shoe 44, and the aligner 18
form a "three-wheeled straightener" whose operation is well known
to those skilled in the art. The three-wheeled straightener
plastically reverse bends the pipe by an amount sufficient to allow
pipe section 16 to leave reaction shoe 44 at a point 54 with a very
large radius of curvature which approaches infinity. A straight
pipe is thus obtained.
From reaction shoe 44 pipe section 16 is discharged downwardly
along a descent trajectory 50 and at the selected lift-off angle A
with respect to the horizontal. Angle A may have a value from a few
degrees up to 90.degree., which is an important advantage of this
invention.
A level winding mechanism 35 is employed to guide pipe section 16
from the reel 12 as it uncoils across a pipe layer 30 to the center
line of the diverter 24. The level winding force may be reacted
against the reel's flanges 21. The pipe should be held straight in
a vertical plane passing through the longitudinal axis of the
diverter prior to its entering, and while passing across, the
bending shoe 42. This is accomplished by a horizontal bending means
36 which can be adjusted to apply the necessary forces to the pipe
normal to the vertical plane.
To assist in maintaining the descending pipe span under proper
tension and to establish the proper catenary for the pipe in the
body of water, there is additionally provided a pipe tensioner 51.
While the tensioner can have independent elements 52, 53, the
desired tension may be conveniently obtained by mounting only one
tensioning shoe 52 (shown in dotted lines), face-to-face with the
reaction shoe 44, with pipe 16 passing between the pipe-engaging
peripheries of the opposite shoes 52 and 44. The tensioner shoes 52
and 44 or 52 53 firmly grip the pipe by the friction force between
the shoe pads and pipe surface. Pipe tension is controlled by
driving the shoes in the forward or reverse direction.
The various shoes are mounted at spaced locations on the diverter
structure 24 and may be mounted for reciprocating and rotational
movements relative to each other. The pipe-engaging periphery of
each shoe preferably has a movable chain (not shown) made up of
pipe-engaging pads that may be arcuately shaped to receive and
closely engage against the wall of the moving pipe. The chains in
the straightening and tensioning shoes move in directions indicated
by the arrows.
The tensioner may be assisted by the ship's propulsion during the
pipe-laying operation and/or by the reel's driving means 19.
* * * * *