U.S. patent number 3,775,987 [Application Number 05/270,736] was granted by the patent office on 1973-12-04 for method and apparatus for laying a submergible elongate structure.
This patent grant is currently assigned to Brown & Root, Inc.. Invention is credited to William R. Rochelle, Leif H. Smith.
United States Patent |
3,775,987 |
Rochelle , et al. |
December 4, 1973 |
METHOD AND APPARATUS FOR LAYING A SUBMERGIBLE ELONGATE
STRUCTURE
Abstract
A method and apparatus for laying a submergible elongate
structure upon the bed of a body of water including a floating
vessel having a generally planar deck, a first cable tensioning
system connected to the deck and selectively connectable to a
submergible elongate structure for applying an approximately
constant axial tension upon the submergible elongate structure when
the barge is being advanced along a desired laying route, and a
second cable tensioning system connected independently of the first
cable tensioning system to the deck of the floating vessel and
selectively connectable to the submergible elongate structure when
the floating vessel is maintained in a generally nonadvancing mode
with respect to the intended pipelaying route. A unitary
submergible ramp is pivotally connected to the stern of the
floating vessel and includes a plurality of vertically adjustable
supporting rollers for supporting the submergible elongate
structure within the body of water aft of the floating vessel.
Inventors: |
Rochelle; William R. (Houston,
TX), Smith; Leif H. (Houston, TX) |
Assignee: |
Brown & Root, Inc.
(Houston, TX)
|
Family
ID: |
23032579 |
Appl.
No.: |
05/270,736 |
Filed: |
July 11, 1972 |
Current U.S.
Class: |
405/166;
226/195 |
Current CPC
Class: |
F16L
1/18 (20130101); B63B 35/03 (20130101) |
Current International
Class: |
F16L
1/12 (20060101); F16L 1/20 (20060101); F16L
1/18 (20060101); B63b 035/04 (); F16l 001/00 () |
Field of
Search: |
;61/72.3,72.1
;226/195 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Shapiro; Jacob
Claims
What is claimed is:
1. An apparatus for laying a submergible elongate structure upon
the bed of a body of water comprising:
a floating vessel having a generally planar deck;
means connected to said deck for supporting a submergible elongate
structure to be laid for translation along said deck;
first cable tensioning means connected to said deck and selectively
connectable to a submergible elongate structure to be laid for
applying an approximately constant axial tension upon the
submergible elongate structure while said floating vessel is being
advanced along a desired laying route including,
a first approximately constant tension winch mounted upon the deck
of said floating vessel;
s first pair of spaced rails extending along and generally parallel
to the deck of said floating vessel;
a running assembly supported upon said rails;
a selectively actuatable clamping assembly supported for
translation along said rails by said running assembly;
second cable tensioning means connected to said deck and
selectively connectable to a submergible elongate structure for
applying an approximately constant axial tension upon the
submergible elongate structure supported upon said floating vessel
deck while said floating vessel is maintained in a generally
stationary posture with respect to the desired laying route;
and
a unitary submergible ramp pivotally connected to the stern of said
floating vessel for supporting between said floating vessel and the
bed of the body of water a portion of the submergible elongate
structure to be laid, said unitary submergible ramp including
a plurality of pontoon members to buoyantly support said
submergible elongate structure, and a plurality of selective
vertically adjustable support rollers spaced along the length
thereof to accommodate flexture of a submergible elongate structure
during the laying operation.
2. An apparatus for laying a submergible elongate structure upon
the bed of a body of water as defined in claim 1 and further
comprising:
a plurality of guide posts connected to said unitary submergible
ramp adjacent to said support rollers for maintaining a submergible
elongate structure positioned upon said support rollers.
3. An apparatus for laying a submergible elongate structure upon
the bed of a body of water as defined in claim 1 wherein said
second cable tensioning means comprises:
a second approximately constant tension winch mounted upon the deck
of said floating vessel;
a second pair of spaced rails extending along and generally
parallel to the deck of said floating vessel and in alignement with
said first pair of spaced rails;
a running assembly supported upon said second pair of spaced
rails;
a selectively actuatable clamping assembly supported for
translation along said second pair of rails by said running
assembly; and
a flexible cable connected between said second constant tension
winch and said running assembly.
4. An apparatus for laying a submergible elongate structure upon
the bed of a body of water as defined in claim 3 wherein:
said first and second pair of spaced rails are in axial alignment
with said unitary submergible ramp; and
said second pair of spaced rails is positioned intermediate said
first pair of spaced rails and said unitary submergible ramp.
5. An apparatus for laying a submergible elongate structure upon
the bed of a body of water comprising:
a floating vessel having a generally planar deck;
means connected to said deck for supporting a submergible elongate
structure to be laid for translation along said deck;
first cable tensioning means connected to said deck and selectively
connectable to a submergible elongate structure to be laid for
applying an approximately constant axial tension upon the
submergible elongate structure while said floating vessel is being
advanced along a desired laying route, including
a first approximately constant tension winch mounted upon the deck
of said floating vessel,
a first pair of spaced rails extending along and generally parallel
to the deck of said floating vessel,
a running assembly supported upon said rails,
a selectively actuatable clamping assembly supported for
translation along said rails by said carrying assembly, and
a flexible cable connected between said first approximately
constant tension winch and said running assembly;
second cable tensioning means connected to said deck independently
of said first cable tensioning means and selectively connectable to
a submergible elongate structure for applying an approximately
constant axial tension upon the submergible elongate structure
supported upon said floating vessel deck while said floating vessel
is maintained in a generally stationary posture with respect to the
desired laying route, and
a second approximately constant tension winch mounted upon the deck
of said floating vessel,
a second pair of spaced rails extending along and generally
parallel to the deck of said floating vessel and in alignment with
said first pair of spaced rails,
a running assembly supported upon said second pair of spaced
rails,
a selectively actuatable clamping assembly supported for
translation along said second pair of rails by said running
assembly, and
a flexible cable connected between said second constant tension
winch and said running assembly;
a unitary submergible ramp pivotally connected to the stern of said
floating vessel for supporting between said floating vessel and the
bed of the body of water a portion of the submergible elongate
structure to be laid.
6. An apparatus for laying a submergible elongate structure upon
the bed of a body of water comprising:
a floating vessel having a generally planar deck;
means connected to said deck for supporting a submergible elongate
structure to be laid for translation along said deck;
first cable tensioning means connected to said deck and selectively
connectable to a submergible elongate structure to be laid for
applying an approximately constant axial tension upon the
submergible elongate structure while said floating vessel is being
advanced along a desired laying route, including
a first approximately constant tension winch mounted upon the deck
of said floating vessel,
a first pair of spaced rails extending along and generally parallel
to the deck of said floating vessel,
a running assembly supported upon said rails,
a selectively actuatable clamping assembly supported for
translation along said rails by said carrying assembly, and
a flexible cable connected between said first approximately
constant tension winch and said running assembly;
second cable tensioning means connected to said deck and
selectively connectable to a submergible elongate structure for
applying an approximately constant axial tension upon the
submergible elongate structure supported upon said floating vessel
deck while said floating vessel is maintained in a generally
stationary posture with respect to the desired laying route,
and
a second approximately constant tension winch mounted upon the deck
of said floating vessel,
a second pair of spaced rails extending along and generally
parallel to the deck of said floating vessel and in alignment with
said first pair of spaced rails,
a running assembly supported upon said second pair of spaced
rails,
a selectively actuatable clamping assembly supported for
translation along said second pair of rails by said running
assembly, and
a flexible cable connected between said second constant tension
winch and said running assembly;
a unitary submergible ramp pivotally connected to the stern of said
floating vessel for supporting between said floating vessel and the
bed of a body of water a portion of the submergible elongate
structure to be laid, said unitary submergible ramp including,
a first pair of generally coextensive, mutually parallel pontoons
legs, wherein
each of said first pair of pontoon legs is fashioned with an
enlarged section at a first end thereof;
transverse members extending between and interconnecting said first
pair of pontoon legs at spaced intervals along the length
thereof;
means connected at the second end of said first pair of pontoon
legs for connecting said first pair of pontoon legs to the stern of
said floating vessel;
a second pair of coextensive, mutually parallel pontoon legs,
wherein
each of said second pair of pontoon legs is fashioned with an
enlarged section at a first end thereof;
a plurality of normally extending columns interconnecting
corresponding ones of said first and second pair of pontoon legs
along the length thereof to form at spaced intervals along the
length of said first and second pair of legs a generally U-shaped
structure, in cross section, having the sides thereof formed by
corresponding ones of said plurality of columns and the bottom
thereof formed by one of said transverse member;
a pair of supporting rollers having mutually inclined axes to
cradle therebetween a submergible elongate means to be laid upon
the water bed, said rollers being fixedly mounted upon the
transverse member interconnecting said first pair of pontoons at
the first end thereof;
a transverse bridge member normally extending between corresponding
ones of each of said columns spaced along the length of said
pontoon legs and mounted for selective adjustment with respect
thereto; and
a pair of supporting rollers having mutually inclined axes to
cradle therebetween a submergible elongate means to be laid upon
the bed of a body of water, said pair of rollers being fixedly
mounted upon each transverse member along the length of said first
pair of pontoon legs.
7. A method for laying a submergible elongate structure upon the
bed of a body of water comprising:
supporting the submergible elongate structure at the surface of the
body of water upon a floating vessel having a generally planar
deck;
advancing the floating vessel along a desired laying route;
maintaining an approximately constant axial tension on the
submergible elongate structure while the floating vessel is being
advanced along the desired laying route by tensioning the
submergible elongate structure by a cable tensioning system
connected to the deck of the floating vessel and selectively
connectable to the submergible elongate structure said step of
maintaining axial tension on the elongate structure when the vessel
is being advanced including the steps of,
actuating a first selectively actuatable clamping assembly into
frictional engagement with the submergible elongate structure to be
laid upon the bed of a body of water at a first end of a first pair
of spaced rails;
paying out a flexible cable under constant tension from a first
approximately constant tension which as the floating vessel
proceeds along a laying route and the selectively actuatable
clamping assembly travels to a second end of the first pair of
spaced rails and the pipeline is payed off of the stern of the
floating vessel; and
resetting the selectively actuatable clamping assembly upon the
submergible elongate structure at the first end of the first pair
of spaced rails;
maintaining an approximately constant axial tension on the
submergible elongate structure when the floating vessel is in a
stationary mode with respect to the intended laying route by a
cable tensioning system connected to the deck of said floating
vessel and selectively connectable to the submergible elongate
structure; and
supporting the submergible elongate structure within the body of
water aft of the floating vessel by a unitary submergible ramp
pivotally connected to the stern of the floating vessel, including
the step of:
positioning a plurality of selectively vertically adjustable
support rollers at spaced locations along the unitary submergible
ramp to accommodate for flexture of a submergible structure during
the laying operation.
8. A method for laying a submergible elongate structure upon the
bed of a body of water as defined in claim 7 wherein said step of
maintaining an axial tension on the elongate structure when the
floating vessel is stationary includes the step of:
actuating a second selectively actuatable clamping assembly into
friction engagement with the submergible elongate structure for
constant tension translation along a second pair of rails when the
first selectively actuatable clamping assembly supported for
translation along the first pair of rails reaches the second end
thereof to maintain a constant tension upon the submergible
elongate means while the first selectively actuatable clamping
assembly connected to the first pair of rails is repositioned at
the first end thereof.
9. A method for converting a conventional derrick-construction
barge to a barge for laying a submergible elongate structure upon
the bed of a body of water comprising the steps of:
connecting a first cable tensioning means to deck of the barge for
selective attachment to a submergible elongate structure to be laid
for applying an approximately constant axial tension upon a
submergible elongate structure while the barge is being advanced
along a desired laying route, said step of connecting a first cable
tensioning means for applying axial tension while the barge is
being advanced includes the step of,
providing a first approximately constant tension winch mounted upon
the deck of the floating vessel;
providing a first pair of spaced rails extending along and
generally parallel to the deck of the floating vessel;
providing a running assembly supported upon the rails;
providing a selectively actuatable clamping assembly supported for
translation along the rails by a running assembly; and
providing a flexible cable connected between the first
approximately constant tension winch and the running assembly;
connecting a second cable tensioning means to the deck of the barge
for selective attachment to a submergible elongate structure to be
laid for applying an approximately constant axial tension upon the
submergible elongate structure while the barge is maintained in a
generally stationary posture with respect to the desired laying
route; and
providing a unitary submergible ramp pivotally connectable to the
stern of the barge for supporting between the barge and the bed of
the body of water a portion of the submergible elongate structure
to be laid, including the step of
providing a plurality of selective vertically adjustable support
rollers spaced along the length of the unitary submergible ramp to
accommodate flexture of the submergible elongate structure during
the laying operation.
10. A method for converting a conventional derrick-construction
barge to a barge for laying a submergible elongate structure upon
the bed of a body of water as defined in claim 9 wherein said step
of providing a unitary ramp includes the step of:
providing a plurality of guide posts adjacent to each of the
support rollers for maintaining the submergible elongate structure
positioned upon the support rollers during the laying
operation.
11. A method for converting a conventional derrick-constructions
barge to a barge for laying a submergible elongate structure upon
the bed of a body of water as defined in claim 15 wherein said step
of connecting a second cable tensioning means to the deck of the
barge for applying axial tension while the barge is generally
stationary comprises:
providing a second approximately constant tension winch mounted
upon the deck of the barge;
providing a second pair of spaced rails extending along and
generally parallel to the deck of the barge and in alignment with
the first pair of spaced rails;
providing a running assembly supported upon the second pair of
spaced rails;
providing a selectively actuatable clamping assembly supported for
translation along the second pair of rails by the running assembly;
and
providing a flexible cable connected between the second constant
tension winch and the running assembly.
Description
BACKGROUND OF THE INVENTION
This invention relates to a method and apparatus for laying a
submergible elongate structure upon the bed of a body of water.
More particularly, the invention pertains to a method and apparatus
for laying a submergible pipeline or the like upon a water bed.
With the discovery of large oil and natural gas deposits offshore
and the subsequent successful drilling and production thereof, a
problem arose in connection with the most economical means for
transporting the crude petroleum and/or natural gas from a
producing offshore site to a collection or transfer terminal. Often
the most economical means for transporting oil and gas offshore has
been to establish submerged pipelines between the producing and the
collecting locations. In this connection U.S. Pat. No. 3,280,571 to
Hauber et al.; Lawrence U.S. Pat. Nos. 3,390,532 and 3,487,648;
Rochelle et al. U.S. Pat. No. 3,507,126 and Lochridge U.S. Pat. No.
3,606,759, all assigned to the assignee of the subject application,
disclose highly effective methods and apparatus for laying
pipelines upon the bed of a body of water.
The above noted and other previously known systems have been
specifically designed for submergible pipelaying work. Pipelaying
barges are typically designed with an inclined ramp along the
starboard side thereof to provide a gradual transition of the
pipeline from a generally horizontal posture to a generally sloping
inclination within the body of water. Moreover, often relatively
long and sometimes articulated ramp devices are connected to the
barge stern to support the pipeline within the body of water
intermediate the surface and the bed thereof, and thus minimize the
possibility of the pipeline becoming overstressed. Still further in
order to maintain an acceptable pipeline profile through the
transition zone between the deck of the lay barge and the water bed
frequently hydraulic tensioning systems are utilized to maintain an
approximately constant axial tension upon the pipeline. In this
connection, while wheel or track type tensioning units have been
preferred, elaborate and relatively expensive piston and cylinder
units have also been known.
While many of the above noted devices have achieved a singular
degree of commercial application, in some instances it may be
impractical to allocate such equipment to a particular job. More
particularly stated, in new fields, such as might exist at remote
locations, where drilling may occur in water of a few hundred feet,
the economics of the then existent field development may preclude,
from a sound management viewpoint, the utilization of a pipelaying
barge which has been specifically and advantageously designed for
deep water use. Moreover, it may be economically impractical to
transport a barge which is specifically designed to lay pipeline to
a remote location if only a short working duration is
contemplated.
Therefore, it would be highly desirable to provide a method and
apparatus for readily converting a standard derrick-construction
barge having a generally planar deck to a pipelaying barge
effective for laying pipeline in relatively shallow water. Further,
it would be desirable to provide for such a transition with a
minimum expenditure of time, effort and expense while utilizing
conventional field equipment. Additionally, it would be desirable
to retain the advantageous operating characteristics of more
sophisticated equipment.
OBJECTS AND SUMMARY OF THE INVENTION
It is a general object of the invention to provide a method and
apparatus for laying submergible elongate structures which will
obviate or minimize problems of the type previously described.
It is a particular object of the invention to provide a novel
method and apparatus for laying submergible elongate structures in
water at remote locations.
It is a further object of the invention to provide a novel method
and apparatus for laying submergible elongate structures within a
body of water by converting a conventional derrick-construction
barge, on site, into a pipelaying barge in an efficient and
economical manner.
It is another object of the invention to provide a novel method and
apparatus for converting a conventional planar deck barge for
laying a submergible elongate structure by the utilization of
generally conventional equipment that may be typically found at a
remote location with a minimum of time and effort while retaining
the desirable operating characteristics of more sophisticated
pipeline laying equipment.
It is still another object of the invention to provide a novel
pipeline cable tensioning system utilizing two independent systems
to provide reset and fail safe backup capability.
It is yet another object of the invention to provide a novel
unitary pipeline supporting ramp which will accommodate a flexture
of the pipeline through the ramp, thus eliminating the necessity of
fashioning a ramp within the deck of a construction barge.
BRIEF SUMMARY
An apparatus suitable to accomplish at least some of the foregoing
objects comprises a floating vessel having a generally planar deck
and being operable to support a submergible elongate structure to
be laid upon the bed of a body of water. A first cable tensioning
system is connected to the deck of the floating vessel and is
selectively connectable to the submergible elongate structure for
applying an approximately constant axial tension upon the
submergible elongate structure as the barge is advanced along a
desired pipelaying route. A second cable tensioning system is
connected to the deck of the floating vessel independently of the
first cable tensioning system and is selectively connectable to the
submergible elongate structure for applying an approximately
constant axial tension upon the submergible structure while the
barge is maintained in a generally stationary mode relative to the
intended laying route.
In order to support the submergible elongate structure within the
body of water at the stern of the floating vessel a unitary
submergible ramp is pivotally connected to the stern of the
floating vessel and includes a plurality of rollers for supporting
the elongate structure along the length of the submergible ramp.
The plurality of rollers are individually vertically adjustable so
that a smooth transition may be achieved from the generally
horizontal posture of the submergible elongate structure along the
deck of the floating vessel to an inclined position of the
submergible elongate structure as the structure descends within the
body of water and onto the water bed.
THE DRAWINGS
Other objects and advantages of the present invention will become
apparent from the following detailed description of a preferred
embodiment thereof taken in conjunction with the accompanying
drawings wherein:
FIG. 1 is a side elevational view of a converted
derrick-construction barge operable for laying a submergible
structure, such as a pipeline, upon the bed of a body of water;
FIG. 2 is a plan view of the converted pipelaying barge disclosed
in FIG. 1;
FIG. 3 is a detailed side elevational view of a unitary ramp
comprising one aspect of the subject invention;
FIG. 4 is a plan view of the unitary ramp;
FIG. 5 is a cross-sectional view of the submerged end of the ramp,
taken along section line 5--5 in FIG. 3, and particularly discloses
a non-adjustable roller and a lateral guide bracket combination
mounted upon the unitary ramp;
FIG. 6 is a cross-sectional view of the unitary ramp, taken along
section line 6--6 in FIG. 4, and discloses one of a plurality of
vertically adjustable roller and lateral guide combinations which
are spaced along the length of the unitary ramp structure;
FIG. 7 is a plan view of a cable tensioning system for providing an
approximately constant axial tension on a submergible elongate
structure as it is being laid from a floating vessel;
FIG. 8 is a partial cross-sectional view, taken along section line
8--8 in FIG. 7, and discloses a pair of generally constant tension
winches for use in providing a generally constant axial tension on
a submergible elongate structure as it is being laid;
FIG. 9 is a detailed side elevational view of an elongate rail
system including a clamping assembly for connection to a
submergible elongate structure to provide a continuous tension
thereon as the structure is payed off of the stern of the floating
vessel;
FIG. 10 is a cross-sectional view, taken along section line 10--10
in FIG. 9, and discloses a mounting relationship of a clamping
assembly and rail combination;
FIG. 11 is a detailed side elevational view of a clamping assembly
as generally shown in FIG. 9;
FIG. 12 is an end view of the clamping assembly disclosed in FIG.
11; and
FIGS. 13-16 comprise sequential schematic illustrations of a
process for maintaining a generally constant axial tension upon an
elongate structure as the structure is being laid from the deck of
a converted derrick-construction barge.
DETAILED DESCRIPTION
Turning now to the drawings and in particular to FIGS. 1 and 2
thereof, there will be seen a marine vessel or barge 20 floating
upon the surface 22 of a body of water 24. The barge 20 has been
converted in a manner to be discussed in detail hereinafter to
enable the barge to lay a submergible elongate structure, such as a
pipeline 26, upon the bed 28 of the body of water.
The barge 20, before conversion, may comprise a standard
derrick-construction barge which is typically provided with a
pedestal crane 30. A track mounted crane 32 may also be disposed
upon the barge and may be maneuvered about the generally planar
deck 34 thereof as desired. For a more detailed illustrative
example of a conventional derrick-construction barge to which the
subject invention may be applied, reference may be had to the
derrick-construction barge, H. A. LINDSAY, owned and operated by
Brown & Root, Inc., the assignee of the subject
application.
In order to rapidly and economically convert the
derrick-construction barge 20 into an effective pipelaying vessel a
plurality of pipeline guide shoes 36 are mounted upon the deck in
alignment along one edge thereof for slidably supporting a pipeline
through make-up stations, not shown, and a constant tensioning
cable system 40 comprising one structural aspect of the subject
invention. The shoes 36 at the stern of the barge may be vertically
adjustable to provide a gradual slope of the pipeline 26 as the
pipeline descends into the body of water. For a more detailed
description of pipeline guide shoes suitable for use with the
subject invention, reference may be had to the previously noted
Lawrence U.S. Pat. No. 3,390,532, and particularly to FIGS. 8 and 9
of the drawing, and columns 10, 11 and 12 of the specification. The
disclosure of guide shoes as set forth in the relevant portions of
the Lawrence patent are hereby incorporated by reference as though
set forth at length.
In order to support and thus facilitate a gradual bending
transition of the pipeline 26 from a horizontal posture along the
deck of the converted barge into an inclined sloping posture within
the body of water, a unitary ramp 42 is provided which is pivotally
hitched at one end 44 to the stern of the barge 20. The free end 46
of the unitary ramp is designed to slopingly extend into the body
of water. The free end, as will be more fully discussed
hereinafter, is buoyantly supported by the provision of variable
buoyancy pontoons 48.
Turning now to FIGS. 3-6 there will be seen detailed views of the
subject unitary ramp 42 comprising a further structural aspect of
the instant invention. More particularly, the unitary ramp is
composed of a first pair 50 and 52 of elongate tubular legs which
are generally coextensive and mutually parallel. A second pair of
tubular legs 54 and 56 are also provided which are in like manner
generally coextensive and mutually parallel. The first pair of legs
50 and 52 are interconnected by a plurality of normally extending
transverse members 58 disposed at spaced locations along the length
of the unitary ramp 42. Respective ones 50-54 and 52-56 of the
elongate legs are also interconnected by a plurality of columns 60
also positioned at spaced locations along the length of the unitary
ramp. In cross-section, as particularly illustrated in FIGS. 5 and
6, one of the transverse members 58 and a pair of corresponding
columns 60, in conjunction with the longitudinally extending legs,
form a generally U-shaped cradling structure for supporting a
submergible elongate structure such as a pipeline, as particularly
illustrated in FIGS. 1 and 2. To provide structural rigidity, the
pairs of the tubular legs 50-54, 50-52 and 52-56 are also
interconnected by a plurality of sloping struts 62.
At one end 44 of the unitary ramp a mounting bracket 64 is affixed
to the legs 50 and 52. The mounting bracket 64 may be readily
connected to a conventional hitch 66 mounted upon the stern of the
barge 20.
At the free end 46 of the unitary ramp each of the tubular legs may
be enlarged to form variable bouyancy pontoons 48, as previously
mentioned. The pontoons 48 may be in direct fluid communication
with the remainder of the ramp legs or preferably a bulkhead, not
shown, may be provided across the initial enlarged portion, and a
valving and actuation means, also not shown, may be connected to
each of the pontoons 48 to provide a capability for varying the
bouyancy thereof and thus selectively control the angle of
inclination assumed by the ramp within the water 24.
In order to slidably guide the pipeline 26 longitudinally through
the unitary support ramp 42 the transverse bracket 58 at the free
end 46 of the unitary ramp has coupled thereto a mounting collar 64
which carries a plurality of pivotal roller brackets 67. A pipeline
engaging roller 68 is mounted for rotation within each of the
brackets 67. The rollers 68 are mutually inclined to cradle the
pipeline as it extends within the ramp.
In order to guide and maintain the pipeline 26 upon the cradle
rollers 68, normally extending guide posts 70 are fixedly connected
to the mounting collar 65 at the outer extremities of the rollers
68. Thus, a pipeline 26, such as shown in phantom in FIG. 5, will
be generally centrally aligned within the unitary ramp at the free
end 46 thereof.
As noted in FIG. 1, in order to promote a smooth bending profile
and additionally provide firm support at spaced intervals along the
length of the ramp, a plurality of vertically adjustable roller
guide combinations are mounted along the length of the ramp. In
this connection, note FIG. 6, each of the upright columns 60 is
provided with adjustment rails 72 which longitudinally extend along
the exterior thereof and are fashioned with a plurality of
vertically spaced apertures. An opposing C-clamp 74 is mounted upon
each of the columns 60 and includes flanges interconnected by
threaded fasteners 76 which may be extended through the apertures
in the guide rails 72. The C-clamps 74 may thus be fixedly attached
at desired positions along the columns 60. A transverse arm 78
extends between the clamps 74 and carries roller mounts 80. Rollers
82 are slopingly disposed for rotation within the mounts 80 to
cradle a pipeline 26 thereupon for translation along the ramp 42,
as previously noted.
In order to minimize the possibility of misalignment of the
pipeline 26 upon the supporting rollers 82, a pair of spaced guide
bars 84 are also connected to the transverse arm 78 and normally
extend with respect thereto to bracket and maintain the pipeline in
a generally centrally disposed posture within the unitary ramp
42.
While the unitary ramp structure which extends into the body of
water is suitable for supporting the pipeline 26 in the transition
zone at the end of the barge, it will be appreciated by those
skilled in the art that the inclined pipeline 26 will tend to roll
off of the vessel unless it is constrained in some manner.
Moreover, in order to control bending stress being created in the
sag bend region 27 of the pipeline 26, it has been found to be
highly desirable to maintain an axial tension within the pipeline
26 as it is being laid. In order to provide this generally constant
axial tension in a reliable and economic manner at remote locations
where conversion of a derrick-construction barge to a laying barge
is necessary, reference may be had to FIG. 7 wherein the previously
mentioned cable tensioning system 40 is disclosed.
A plurality of pipeline guide shoes 36 are mounted in alignment
upon the deck 34 of the barge to be converted. Positioned in
alignment between adjacent guide shoes 36 is a first longitudinally
extending rail system 100 which serves to support for translation
thereupon a pipe clamping assembly 102. Connected to the pipe
clamping assembly 102 is a wire rope 104 which is guided around a
sheave 106 and passes beneath a split pipe cover 108 to a second
sheave 110 beneath another split pipe protector 112 under a sheave
114 and up to a generally constant tension winch 116 mounted upon
the barge deck. The sheaves 106, 110 and 114 serve to guide the
wire rope in a generally U-shaped manner and thus permit a compact
arrangement of the cable tensioning system. The split pipe
protectors 108 and 112 serve to enclose the wire rope 104 along the
barge deck 34 and thus minimize the possibility of the line
becoming fouled. Therefore, the pipe clamping assembly 102 is free
to translate along the rail 100 between adjacent shoes 36 under a
generally constant axial tension provided via wire rope 104 by the
deck winch 116.
A second cable tensioning unit is positioned downstream of the
first cable tensioning unit and includes a longitudinally extending
guide rail 120 positioned in alignment with adjacent shoes 36
between the rail 100 and the unitary ramp 42. A pipe clamping
assembly 122 is mounted for translation upon the rail 120. A
flexible wire rope 124 is connected to the translatable pipe
clamping assembly 122 and is guided around a pair of sheaves 126
and 128 to a constant tension winch 130 mounted upon the deck 34 of
the barge for operation independently of the deck winch 116.
Therefore, the pipe clamping assembly 122 is free to translate
along rail 120 between adjacent shoes 36 under generally constant
tension provided via wire rope 124 from the constant tension winch
130.
Turning now to FIGS. 9 and 10, there will be seen a rail system
suitable for use as either rail 100 or 120. More particularly, a
plurality of upright posts 132, which may be fashioned from channel
iron or the like, are mounted upon the barge deck 34 and extend to
an elevation so that a pipe clamping assembly 102 or 122 will be in
coaxial alignment with a pipe supported upon shoes 36. The posts
132 support an opposing pair of U-channel rails 134 and 136 which
extend generally parallel to the deck surface 34. In order to
provide structural rigidity to the rail support system, struts 138
are intermittently connected between the rails and the deck and the
posts 132 are horizontally interconnected by L-channel braces
140.
The pipe clamping assembly 102 or 122 is supported along the rails
134 and 136 by a running assembly 142 which includes a central body
member 144 mounted between spaced sets of railway trucks 146 and
148, respectively. In order to perform the dual function of guiding
the body 144 and providing a cover for the under-running railway
trucks 146 and 148, L-shaped members 150 and 152 are mounted upon
an upper surface of rails 134 and 136, respectively, and mutually
extend together to provide a slot in which the body 144 may travel
along the rail structure. A wire rope 104 is pivotally connected to
one end of the assembly 142, as at 154. The rope in turn is
connected to a constant tension winch, as previously described.
Maximum limits of travel of the running assembly 142 are maintained
by the provision of horizontally extending stop bars 156 and 158
mounted across the rails 134 and 136 at the remote ends thereof.
The stop bars serve to abut against compatible surfaces 160 and
162, respectively, fashioned within the running assembly 142 to
limit travel of the running assembly.
Turning now particularly to FIGS. 11 and 12, there will be seen
detailed side and end views of a pipe clamping assembly suitable
for use with the subject invention. More particularly, a pair of
spaced parallel mounting plates 160 and 162 are dimensioned to
intimately engage the body member 144 of the running assembly. A
plurality of threaded fasteners 166 serve to extend through the
mounting plates and the body member 144 to releasably and thus
interchangeably connect the pipe clamping assembly to the running
assembly.
Fixedly connected to the mounting plates 160 and 162 is a first
arcuate pipeline bearing segment 168 which is approximately in
cross section one-third of the arc of a circle. Interconnecting the
mounting plate 160 and one portion of the arcuate segment 168 is a
hinge 170. In a similar manner interconnecting the mounting plate
162 and another portion of the arcuate portion 168 is a hinge
assembly 172. Mounted upon the hinge plates 170 and 172 are pivotal
bracket assemblies 176 and 178, respectively. The pivotal brackets
176 and 178 have fixedly mounted thereto arcuate segments 180 and
182 which, like the base segment 168, are each composed of an arc
of approximately one-third of a circle.
The hinge mountings 176 and 178 are mutually pivotally movable
toward or away from each other by the provision of a shaft 184
having left-handed threads 186 on one end thereof and right-handed
threads 188 on an opposite end thereof. The shaft 184 extends
through internally threaded mountings 190 and 192, respectively,
which in turn are pivotally connected to the brackets 176 and 178.
The shaft 184 is further provided at the ends thereof with wrench
flats to receive in driving communication the head of a socket
wrench or the like to enable an operator to open and to close the
pipe clamping assembly.
The segments 168, 180 and 182 may be fabricated from a longitudinal
split pipe and are selected to correspond in size to the pipe to be
laid. In order to facilitate frictional engagement of the pipe
clamping assembly with a pipe extending therethrough, each of the
arcuate segments 168, 180 and 182 are laminated with a liner such
as bonded rubber neoprene or the like 194.
While the description thus far has been directed to a single
pivotal hinge assembly, it will be appreciated by those skilled in
the art that more than one hinge assembly may be conveniently
utilized with each pipe clamping assembly. In this connection, two
longitudinally spaced hinge brackets are illustrated in FIG. 11.
Both brackets are identical in structure and function as previously
described.
METHOD OF OPERATION
Turning now to FIGS. 13-16, there will be seen in a sequential
schematic array a process of utilizing the suject cable tensioning
system for maintaining an approximately constant axial tension upon
a pipeline as it is being laid.
More particularly, a pipeline 26 is made up on board the floating
vessel and is supported upon a plurality of axially aligned shoes
36 as illustrated in FIG. 13. In order to maintain an approximately
constant axial tension upon the pipeline, and thus enhance the
profile characteristics thereof, the pipe clamping assembly 102 is
intimately tightened around the pipeline at a first end 200 of the
guide rail 100. The pipe clamping assembly 122 is maintained in a
non-engagement posture in approximately the center 202 of the guide
rail 120.
Axial tension is applied to the pipe by actuation of the constant
tension winch 116 and wire rope 104 which is connected to the
clamping assembly 102 as previously described. Under such
conditions, the barge lays away along a desired pipelaying route in
a direction from left to right as viewed in FIG. 13 and as
indicated by arrow A so that the pipeline 26 relative to the barge
20 is payed off of the stern.
By reference to FIG. 14 this relative motion is reflected in the
fact that pipe clamping assembly 102 which is fixedly connected to
the pipeline 26 has moved from right to left or in the direction of
arrow B with respect to the barge as wire rope 104 is payed out
under constant tension from winch 116.
Still further, movement of the barge along the desired laying
route, as illustrated in FIG. 15, will translate the pipe clamping
assembly 102 to another end 204 of the rail 100. At this point, in
time, in order to continue to lay the pipeline, it will be
necessary to reset the clamping assembly 102 at the first end 200
of the rail 100. In order to provide for this resetting function
without losing the approximately constant tension on the pipeline,
the clamping assembly 122 is actuated into firm gripping engagement
with the surface of the pipeline 26 to thereby transmit an axial
tension to the pipeline by the provision of the constant tension
winch 130 acting through wire rope 124. Once clamping assembly 122
is firmly engaged with the pipeline, the clamping assembly 102 may
be released and the tension in line 104 will automatically
translate the assembly from left to right as viewed in FIG. 15 back
to the first end 200 of the rail 100. During this resetting of the
pipe clamping assembly 102, the barge is maintained in an
approximately stationary posture with respect to the intended pipe
laying route.
It has been found, however, that notwithstanding the intention of
remaining stationary, wave action and the like will produce a
pitching motion of the barge. In order to maintain an approximately
constant axial tension on the pipeline therefore the clamping
assembly 122 must be free to translate and in this connection, as
previously described, the clamping assembly 122 is mounted for
translation under constant tension upon rail assembly 120.
Once the pipe clamping assembly 102 is reattached to the pipeline
26 at the first end 200 of the rail 100, the pipeline clamping
assembly 122 may be released and constant axial tension will be
maintained upon the pipeline by the provision of winch 116 as
previously discussed.
The above described steps of clamping and unclamping are repeated
in an ambulatory manner as the pipeline is laid along a desired
route.
SUMMARY OF THE MAJOR ADVANTAGES
It will be appreciated that the above described method and
apparatus provides a convenient and ready means of converting a
standard derrick-construction barge to a pipelaying barge with a
minimum amount of time and effort, while the desirable operating
characteristics of ramp support plus axial tension of more
sophisticated equipment are maintained.
Further, the subject method and apparatus provides a means for
laying pipeline without the utilization of complicated and
expensive hydraulic systems which would be difficult or impractical
to fabricate in the field.
Still further, the subject system provides a smooth bend of the
pipeline at the inflection point between horizontal and inclined
postures at the stern of the barge without reshaping the deck
structure of the converted barge.
Another significant advantage of the invention is the provision of
a unitary ramp structure which is capable of firmly supporting a
curved portion of a pipeline while maintaining the pipeline in
general axial alignment with respect to the ramp.
Further, a significant advantage of the present invention pertains
to the exclusive utilization of independent cable tensioning
systems which provide a reset capability and fail safe backup
capability.
Although the invention has been described in connection with
preferred embodiments and methods, it will be appreciated by those
skilled in the art that additions, deletions, modifications and
substitutions, or other changes not specifically described, may be
made which will fall within the purview of the appended claims.
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