U.S. patent application number 12/282473 was filed with the patent office on 2009-10-01 for strake systems and methods.
This patent application is currently assigned to SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.. Invention is credited to Donald Wayne Allen, Stephen Paul Armstrong, Dean Leroy Henning, Damon Michael McMillan, Janet K. McMillan, David Wayne, Christopher Steven West.
Application Number | 20090242207 12/282473 |
Document ID | / |
Family ID | 38510183 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090242207 |
Kind Code |
A1 |
Allen; Donald Wayne ; et
al. |
October 1, 2009 |
STRAKE SYSTEMS AND METHODS
Abstract
There is disclosed a system comprising a structural element; at
least one strake holder connected to the structural element; and at
least one flexible helical strake connected to the at least one
strake holder.
Inventors: |
Allen; Donald Wayne;
(Richmond, TX) ; Armstrong; Stephen Paul;
(Houston, TX) ; Henning; Dean Leroy; (Needville,
TX) ; McMillan; Damon Michael; (Humble, TX) ;
Wayne; David; (Deer Park, TX) ; McMillan; Janet
K.; (Deer Park, TX) ; West; Christopher Steven;
(Pearland, TX) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Assignee: |
SHELL INTERNATIONALE RESEARCH
MAATSCHAPPIJ B.V.
The Hague
NL
|
Family ID: |
38510183 |
Appl. No.: |
12/282473 |
Filed: |
March 9, 2007 |
PCT Filed: |
March 9, 2007 |
PCT NO: |
PCT/US2007/063659 |
371 Date: |
January 20, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60781846 |
Mar 13, 2006 |
|
|
|
Current U.S.
Class: |
166/367 ;
405/224 |
Current CPC
Class: |
F16L 1/18 20130101; E21B
17/017 20130101; F16L 1/123 20130101; F16L 9/045 20130101; E21B
17/015 20130101 |
Class at
Publication: |
166/367 ;
405/224 |
International
Class: |
E21B 17/01 20060101
E21B017/01; E02D 5/74 20060101 E02D005/74 |
Claims
1. A system comprising: a structural element; at least one strake
holder connected to the structural element; and at least one
flexible helical strake connected to the at least one strake
holder.
2. The system of claim 1, wherein the structural element is
selected from the group consisting of a shell, a collar, an oil
flowline, a pipeline, a drilling riser, a production riser, a steel
tubular, import and export risers, subsea pipelines, tendons for
tension leg platforms, legs for traditional fixed and for compliant
platforms, space-frame members for platforms, cables, umbilicals,
mooring elements for deepwater platforms, hull structures for
tension leg platforms and for spar type structures, and column
structures for tension leg platforms and for spar type
structures.
3. The system of claim 1, wherein the structural element comprises
a plurality of sections welded or threaded to each other.
4. The system of claim 1, wherein the at least one flexible helical
strake comprises a flexible material having a Young's Modulus E
from 0.01 to 0.5 GPa.
5. The system of claim 1, wherein the at least one flexible helical
strake comprises at least three flexible helical strakes.
6. The system of claim 1, wherein the at least one strake holder
comprises a high strength material having a Young's Modulus E from
0.5 to 500 GPa.
7. The system of claim 1, wherein the at least one flexible helical
strake comprises a rubber strake having a t-shaped cross section,
at least a portion of the strake extending out of the strake
holder.
8. The system of claim 1, wherein a first end of the at least one
strake holder is attached to a first collar, and a second end of
the at least one strake holder is attached to a second collar, the
first collar and the second collar attached about the structural
element.
9. A method of installing a structural element in a body of water
comprising: attaching at least one flexible helical strake about
the structural element; and moving the structural element and the
flexible strake over a roller, so that the flexible strake is
temporarily deformed when the flexible strake interfaces with the
roller.
10. The method of claim 9, wherein the structural element is
selected from the group consisting of a shell, a collar, an oil
flowline, a pipeline, a drilling riser, a production riser, a steel
tubular, import and export risers, subsea pipelines, tendons for
tension leg platforms, legs for traditional fixed and for compliant
platforms, space-frame members for platforms, cables, umbilicals,
mooring elements for deepwater platforms, hull structures for
tension leg platforms and for spar type structures, and column
structures for tension leg platforms and for spar type
structures.
11. The method of claim 9, wherein the structural element comprises
a plurality of sections welded to each other.
12. The method of claim 9, wherein the structural element comprises
a plurality of sections threaded to each other.
13. The method of claim 9, wherein attaching at least one helical
strake about the structural element comprises attaching at least
three helical strakes about the structural element.
14. The method of claim 9, wherein attaching at least one helical
strake about the structural element comprises attaching a plurality
of flexible sheets to each other.
15. The method of claim 9, wherein attaching at least one helical
strake about the structural element comprises attaching a plurality
of flexible sheets to each other with an adhesive.
16. The method of claim 9, wherein the first roller is azimuthally
spaced apart from the second roller by 90 to 150 degrees measured
as an arc angle of the structural element.
17. A system comprising: a structural element; at least one strake
sheet connected to at least one other strake sheet about the
structural element to form at least two strakes.
18. The system of claim 17, wherein the at least one strake sheet
comprises a flexible material having a Young's Modulus E from
0.00001 to 0.5 GPa.
19. The system of claim 17, wherein the at least one strake sheet
comprises a rubber strake sheet.
20. The system of claim 17, comprising at least three strakes.
Description
FIELD OF INVENTION
[0001] The present disclosure relates to strake systems and
methods.
BACKGROUND
[0002] Structural elements can be installed at sea from a floating
vessel using a J-lay configuration where the structural element is
held vertically on the vessel and dropped vertically into the water
and then when it reaches the bottom of the body of water, it lays
horizontal, or alternatively structural elements can be installed
in a S-lay configuration where the structural element is held
horizontally on the vessel, drops to vertical through the body of
water, and then rests on the bottom of the body of water in a
horizontal configuration. Other configurations for installing a
structural element from a vessel in a body of water are also
known.
[0003] Referring now to FIG. 1, system 100 for installing
structural element 114 on bottom 116 of body of water 112 is
illustrated. System 100 includes vessel 110 with tensioner 120 and
stinger 118. Tensioner 120 holds structural element 114 in a
horizontal configuration as it enters water, and then structural
element 114 rolls down stinger 118, then drops to a vertical
configuration, and then back to a horizontal configuration as it
lays on bottom 116. Tensioner 120 and vessel 110 have a sufficient
capacity to support structural element 114 as it is being
installed.
[0004] Currents in body of water 112 may cause vortexes to shed
from the sides of structural element 114. When these types of
structural elements, such as a cylinder, experience a current in a
flowing fluid environment, it is possible for the structural
element to experience vortex-induced vibrations (VIV). These
vibrations may be caused by oscillating dynamic forces on the
surface which can cause substantial vibrations of the structural
element, especially if the forcing frequency is at or near a
structural natural frequency.
[0005] The magnitude of the stresses on a structural element is
generally a function of and increases with the velocity of the
water current passing these structural elements and the length of
the structural element.
[0006] There are generally two kinds of current-induced stresses in
flowing fluid environments. The first kind of stress is caused by
vortex-induced alternating forces that vibrate the structural
element ("vortex-induced vibrations") in a direction perpendicular
to the direction of the current. When fluid flows past the
structural element, vortices may be alternately shed from each side
of the structural element. This produces a fluctuating force on the
structural element transverse to the current. If the frequency of
this harmonic load is near the resonant frequency of the structural
element, large vibrations transverse to the current can occur.
These vibrations can, depending on the stiffness and the strength
of the structural element and any welds, lead to unacceptably short
fatigue lives. In fact, stresses caused by high current conditions
in marine environments have been known to cause structural elements
such as risers to break apart and fall to the ocean floor.
[0007] The second type of stress is caused by drag forces which
push the structural element in the direction of the current due to
the structural element's resistance to fluid flow. The drag forces
may be amplified by vortex induced vibrations of the structural
element. For instance, a riser pipe that is vibrating due to vortex
shedding will disrupt the flow of water around it more than a
stationary riser. This may result in more energy transfer from the
current to the riser, and hence more drag.
[0008] Some devices used to reduce vibrations caused by vortex
shedding from sub-sea structural elements operate by modifying the
boundary layer of the flow around the structural element to prevent
the correlation of vortex shedding along the length of the
structural element. Examples of such devices include sleeve-like
devices such as helical strake elements, shrouds, fairings and
substantially cylindrical sleeves.
[0009] Some VIV and drag reduction devices can be installed on
risers and similar structural elements before those structural
elements may be deployed underwater. Alternatively, VIV and drag
reduction devices can be installed on structural elements after
those structural elements have been deployed underwater.
[0010] When installing a structural element in an S-lay
configuration, the structural element may travel over a stinger and
encounter one or more rollers on the stinger. A pre-installed
strake may be damaged if it passes over the stinger. One
alternative is to install the strakes on the structural element
after it passes over the rollers and the stinger. Another
alternative is to protect the strakes as they are passed over the
rollers and the stinger.
[0011] U.S. Pat. No. 6,896,447 discloses a vortex induced vibration
suppressor and method. The apparatus includes a body that is a
flexible member of a polymeric (e.g., polyurethane) construction. A
plurality of helical vanes on the body extend longitudinally along
and helically about the body. Each vane has one or more openings
extending transversely there through. A longitudinal slot enables
the body to be spread apart for placing the body upon a riser, pipe
or pipeline. Tensile members that encircle the body and pass
through the vane openings enable the body to be secured to the
pipe, pipeline or riser. U.S. Pat. No. 6,896,447 is herein
incorporated by reference in its entirety.
[0012] Copending U.S. patent application having Ser. No. 11/468,690
and Attorney Docket number TH2926 was filed on Aug. 30, 2006, and
discloses a system comprising a structural element, at least one
helical strake about the structural element, and at least one ramp
to provide a transition from the structural element to the helical
strake. Copending U.S. patent application having Ser. No.
11/468,690 is herein incorporated by reference in its entirety.
[0013] There is a need in the art for an improved apparatus and
method for suppressing vibration. There is another need in the art
for apparatus for new and improved methods of installing strake
elements for suppressing vibration in a flowing fluid environment.
There is another need in the art for new and improved methods of
installing strake elements for suppressing vibration in a flowing
fluid environment on a structural element before the structural
element is installed over a ramp or roller. There is another need
in the art for new and improved methods of installing strake
elements for suppressing vibration in a flowing fluid environment
on a structural element before the structural element is installed
in the flowing fluid environment which does not require
intervention or adjustment of the strake elements once the
structural element is in the flowing fluid environment.
[0014] These and other needs of the present disclosure will become
apparent to those of skill in the art upon review of this
specification, including its drawings and claims.
SUMMARY OF THE INVENTION
[0015] One aspect of the invention provides a system comprising a
structural element; at least one strake holder connected to the
structural element; and at least one flexible helical strake
connected to the at least one strake holder.
[0016] Another aspect of the invention provides a method of
installing a structural element in a body of water comprising
attaching at least one flexible helical strake about the structural
element; and moving the structural element and the flexible strake
over a roller, so that the flexible strake is temporarily deformed
when the flexible strake interfaces with the roller.
[0017] Advantages of the invention include one or more of the
following:
[0018] improved apparatuses and methods for suppressing
vibration;
[0019] improved systems and methods of installing strake elements
for suppressing vibration in a flowing fluid environment;
[0020] improved systems and methods of installing strake elements
for suppressing vibration in a flowing fluid environment on a
structural element before the structural element is installed over
a ramp or roller; and
[0021] improved systems and methods of installing strake elements
for suppressing vibration in a flowing fluid environment on a
structural element before the structural element is installed in
the flowing fluid environment which does not require intervention
or adjustment of the strake elements once the structural element is
in the flowing fluid environment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 illustrates a system for installing a structural
element in a body of water in an S-lay configuration.
[0023] FIG. 2 illustrates a system for installing a structural
element in a body of water in an S-lay configuration.
[0024] FIGS. 3a and 3b illustrate a structural element with
strakes.
[0025] FIGS. 4a-4c illustrate a structural element with strakes
traveling over a stinger.
[0026] FIGS. 5a-5b illustrates a structural element with
strakes
DETAILED DESCRIPTION OF THE INVENTION
[0027] In one embodiment, there is disclosed a system comprising a
structural element; at least one strake holder connected to the
structural element; and at least one flexible helical strake
connected to the at least one strake holder. In some embodiments,
the structural element is selected from the group consisting of a
shell, a collar, an oil flowline, a pipeline, a drilling riser, a
production riser, a steel tubular, import and export risers, subsea
pipelines, tendons for tension leg platforms, legs for traditional
fixed and for compliant platforms, space-frame members for
platforms, cables, umbilicals, mooring elements for deepwater
platforms, hull structures for tension leg platforms and for spar
type structures, and column structures for tension leg platforms
and for spar type structures. In some embodiments, the structural
element comprises a plurality of sections welded or threaded to
each other. In some embodiments, the at least one flexible helical
strake comprises a flexible material having a Young's Modulus E
from 0.01 to 0.5 GPa. In some embodiments, the at least one
flexible helical strake comprises at least three flexible helical
strakes. In some embodiments, the at least one strake holder
comprises a high strength material having a Young's Modulus E from
0.5 to 500 GPa. In some embodiments, the at least one flexible
helical strake comprises a rubber strake having a t-shaped cross
section, at least a portion of the strake extending out of the
strake holder. In some embodiments, a first end of the at least one
strake holder is attached to a first collar, and a second end of
the at least one strake holder is attached to a second collar, the
first collar and the second collar attached about the structural
element.
[0028] In one embodiment, there is disclosed a method of installing
a structural element in a body of water comprising attaching at
least one flexible helical strake about the structural element; and
moving the structural element and the flexible strake over a
roller, so that the flexible strake is temporarily deformed when
the flexible strake interfaces with the roller. In some
embodiments, the structural element is selected from the group
consisting of a shell, a collar, an oil flowline, a pipeline, a
drilling riser, a production riser, a steel tubular, import and
export risers, subsea pipelines, tendons for tension leg platforms,
legs for traditional fixed and for compliant platforms, space-frame
members for platforms, cables, umbilicals, mooring elements for
deepwater platforms, hull structures for tension leg platforms and
for spar type structures, and column structures for tension leg
platforms and for spar type structures. In some embodiments, the
structural element comprises a plurality of sections welded to each
other. In some embodiments, the structural element comprises a
plurality of sections threaded to each other. In some embodiments,
attaching at least one helical strake about the structural element
comprises attaching at least three helical strakes about the
structural element. In some embodiments, attaching at least one
helical strake about the structural element comprises attaching a
plurality of flexible sheets to each other. In some embodiments,
attaching at least one helical strake about the structural element
comprises attaching a plurality of flexible sheets to each other
with an adhesive. In some embodiments, the first roller is
azimuthally spaced apart from the second roller by 90 to 150
degrees measured as an arc angle of the structural element.
[0029] In one embodiment, there is disclosed a system comprising a
structural element; at least one strake sheet connected to at least
one other strake sheet about the structural element to form at
least two strakes. In some embodiments, the at least one strake
sheet comprises a flexible material having a Young's Modulus E from
0.00001 to 0.5 GPa. In some embodiments, the at least one strake
sheet comprises a rubber strake sheet. In some embodiments, the
system also includes at least three strakes.
[0030] Referring now to FIG. 2, in one embodiment of the invention,
system 200 is illustrated. System 200 includes vessel 210 in body
of water 212, installing structural element 204 in body of water
212 and resting a portion of structural element 204 on bottom 216.
Vessel 210 may include tensioner 220 to keep tension on structural
element 204 so that it does not sink in water 212. Flexible strakes
206 are attached about structural element 204 to dampen any vortex
induced vibration of structural element 204.
[0031] Referring now to FIGS. 3a-3b, in some embodiments of the
invention, structural element 304 is illustrated. Structural
element 304 encloses passage 302. Strake holders 306a, 306b, and
306c may be mounted about the circumference of structural element
304. Flexible strake elements 308a, 308b, and 308c are inserted
into strake holders 306a-306c, respectively. Strake holders 306a,
306b, and 306c provide a high strength structure attached to
structural element 304 to retain flexible strake elements
308a-308c. Flexible strake elements 308a-308c serve to inhibit
vortex induced vibration when structural element 304 is in a
flowing fluid stream.
[0032] In some embodiments, flexible strake elements 308a, 308b,
and 308c fit fully inside the strake holders 306a, 306b, and 306c.
In some embodiments, flexible strake elements 308a, 308b, and 308c
are of the same cross section as the inside of the strake holders
306a, 306b, and 306c. In some embodiments, flexible strake elements
308a, 308b, and 308c extend out of the strake holders 306a, 306b,
and 306c as shown in FIG. 3a. In some embodiments, flexible strake
elements 308a, 308b, and 308c may alternately fit inside the strake
holders 306a, 306b, and 306c when compressed, for example by a
roller, and extend out of the strake holders 306a, 306b, and 306c
as shown in FIG. 3a when not compressed. In some embodiments,
flexible strake elements 308a, 308b, and 308c may comprise an
elastic material that can be compressed into strake holders 306a,
306b, and 306c, and then regain shape outside of strake holders
306a, 306b, and 306c when not under compression.
[0033] In some embodiments, strake holders 306a, 306b, and 306c may
be cut along their longitudinal axis to reduce their effective
stiffness or to allow the flexible strake elements 308a, 308b, and
308c to extend outside of the strake holders. These cuts may vary
in length and density along the strake holder.
[0034] Structural element 304 has outside diameter D 328. Strake
elements 308a-308c have height H 330. Adjacent strake elements may
be spaced apart by a pitch L 332. In some embodiments of the
invention, outside diameter D 328 may be from about 2 to 60 cm. In
some embodiments of the invention, height H 330 may be from about
5% to about 50% of outside diameter D 328. In some embodiments of
the invention, height H 330 may be from about 1 to about 15 cm. In
some embodiments of the invention, pitch L 332 may be from about 1D
to about 10D. In some embodiments of the invention, pitch L 332 may
be from about 10 to about 500 cm.
[0035] In some embodiments, strake elements 308a-308c may comprise
a flexible material, for example rubber, polybutadiene, or
polyurethane. In some embodiments, strake elements 308a-308c may
have a Young's Modulus E from about 0.01 to about 0.5 giga-pascals
(GPa), for example from about 0.1 to about 0.4 giga-pascals (GPa),
or for example from about 0.001 to about 0.05 giga-pascals
(GPa).
[0036] In some embodiments, strake holders 306a-306c may comprise a
high strength material, for example aluminum, steel, stainless
steel, copper, nylon, polyethylene, polypropylene, a thermoset
polymer, and polyvinyl chloride. In some embodiments, strake
holders 306a-306c may have a Young's Modulus E from about 0.6 to
about 400 giga-pascals (GPa), for example from about 0.75 to about
200 giga-pascals (GPa), or for example from about 1 to about 50
giga-pascals (GPa).
[0037] In some embodiments of the invention, there may be about 1
to about 10 helical strake starts about a circumference of
structural element 304. In some embodiments of the invention, there
may be about 2 to about 6 helical strake starts about a
circumference of structural element 304. In some embodiments of the
invention, there may be about 3 helical strake starts about a
circumference of structural element 304.
[0038] In some embodiments of the invention, strakes 308a-308c may
be made of a flexible material, such as a polymer, for example a
thermoplastic polymer: polypropylene, polyethylene, polybutylene,
other polyolefins, or co-polymers of olefins. In some embodiments
of the invention, strakes 308a-308c may be made of a composite,
such as fiberglass or carbon fiber composite. In some embodiments
of the invention, strakes 308a-308c may be made of a metal, such as
steel or aluminum.
[0039] In some embodiments of the invention, strakes 308a-308c may
be attached to a support apparatus. The support apparatus and
strakes 308a-308c may then be installed into strake holders
306a-306c about structural element 304.
[0040] Referring now to FIGS. 4a-4c, in some embodiments of the
invention, stinger 418 and structural element 404 are illustrated.
Stinger 418 includes roller 419a and roller 419b which are adapted
to transport structural element 404. Structural element 404 is able
to roll down stinger 418 while resting on rollers 419a and 419b. In
some embodiments of the invention, rollers 419a and 419b may be
azimuthally spaced from about 90 to about 150 degrees apart,
measured as an arc-angle of structural element 404.
[0041] Referring now to FIG. 4b, structural element 404 is shown in
cross-section moving along stinger 418. Structural element 404
encloses passage 402 and has attached to its exterior strake
holders 406a, 406b, and 406c. Flexible strakes 408a, 408b, and 408c
are attached to strake holders 406a, 406b, and 406c. Stinger has
rollers 419a and 419b, which interface with an exterior of
structural element 404 to support structural element 404 and allow
structural element to roll along stinger 418. Flexible strake 408c
is bent as it is interfacing with stinger 418. In some embodiments,
flexible strakes 408a, 408b, and 408c are made of an elastic
material that is able to deform when it encounters other structures
and then return to its original shape.
[0042] Referring now to FIG. 4c, in some embodiments of the
invention, structural element 404 of FIG. 4b has moved further
along so that strake 408b is interfacing with roller 419b, and
strake 408c is interfacing with roller 419a. Strake 408b has
temporarily deformed and strake 408c has temporarily deformed, so
that the strakes are not damaged when they encounter the
rollers.
[0043] In some embodiments of the invention, strakes 408a-408c may
be attached to a collar, pipe, shell, or other support apparatus.
The support apparatus and strakes 408a-408c may then be installed
about structural element 404.
[0044] Referring now to FIGS. 5a and 5b, in some embodiments of the
invention, structural element 504 is illustrated. Structural
element 504 encloses passage 502. Flexible sheets 506a, 506b, and
506c may be mounted about the circumference of structural element
504. Connector 508a holds together a portion of flexible sheets
506a and 506b, to form flexible strake element 510a. Connector 508b
holds together a portion of flexible sheets 506b and 506c, to form
flexible strake element 510b. Connector 508c holds together a
portion of flexible sheets 506c and 506a, to form flexible strake
element 510c. Flexible strake elements 510a-510c serve to inhibit
vortex induced vibration when structural element 504 is in a
flowing fluid stream.
[0045] Structural element 504 has an outside diameter D 528. Strake
elements 510a-510c have height H 530. Adjacent strake elements may
be spaced apart by a pitch L 532. In some embodiments of the
invention, outside diameter D 528 may be from about 2 to 60 cm. In
some embodiments of the invention, height H 530 may be from about
5% to about 50% of outside diameter D 528. In some embodiments of
the invention, height H 530 may be from about 1 to about 15 cm. In
some embodiments of the invention, pitch L 532 may be from about 1D
to about 10D. In some embodiments of the invention, pitch L 532 may
be from about 10 to about 500 cm.
[0046] In some embodiments of the invention, there may be about 1
to about 10 helical strake starts about a circumference of
structural element 504. In some embodiments of the invention, there
may be about 2 to about 6 helical strake starts about a
circumference of structural element 504. In some embodiments of the
invention, there may be about 3 helical strake starts about a
circumference of structural element 504.
[0047] In some embodiments of the invention, flexible sheets 506a,
506b, and 506c may be made of a flexible material, such as a
polymer, for example a thermoplastic polymer: polypropylene,
polyethylene, polybutylene, other polyolefins, or co-polymers of
olefins. In some embodiments of the invention, connectors 508a-508c
may be an adhesive, a staple, a bolt and a nut, a rivet, a weld, or
other suitable connection for holding together flexible sheets
506a, 506b, and 506c.
[0048] In some embodiments of the invention, flexible sheets 506a,
506b, and 506c may comprise a flexible material having a Young's
Modulus E from about 0.01 to about 0.5 giga-pascals (GPa), for
example from about 0.01 to about 0.3 giga-pascals (GPa), or for
example from about 0.01 to about 0.1 giga-pascals (GPa).
[0049] In one embodiment, reinforced rubber sheet having a
thickness from about a 0.02 diameter to about a 0.10 diameter
thickness (measured as outside diameter D 528) is provided. The
reinforced rubber sheet is cut in long strips to form flexible
sheets 506a, 506b, and 506c. These flexible sheets 506a, 506b, and
506c are formed into a U shaped cross sections. The U shaped
sections are placed on structural element 504 with a pitch from
about 4 to about 30 times outside diameter D 528. The height of
strake elements 510a-510c that are formed with the adjacent U
shaped sections is from about 0.1 to about 0.3 times outside
diameter D 528. The adjacent U shaped sections are coated with a
vulcanizing adhesive. The structural element 504 with the strakes
attached is placed in an oven and heated to obtain rubber cure.
[0050] In some embodiments of the invention, clamshell type strake
elements may be mounted around a structural element according to
the method disclosed in U.S. Pat. No. 6,695,539, which is herein
incorporated by reference in its entirety.
[0051] In some embodiments of the invention, strake elements may be
installed about a structural element according to the method
disclosed in U.S. Pat. No. 6,561,734, which is herein incorporated
by reference in its entirety.
[0052] In some embodiments of the invention, strake elements may be
installed about a structural element according to the method
disclosed in United States Patent Application Publication No.
2003/0213113, which is herein incorporated by reference in its
entirety.
[0053] In some embodiments of the invention, the outside diameter
of a structural element to which strake elements can be attached
may be from about 10 to about 50 cm. In some embodiments of the
invention, the height of strake elements may be from about 5% to
about 50% of the structural element's outside diameter. In some
embodiments of the invention, the height of strake elements may be
from about 5 to about 20 cm.
[0054] In some embodiments of the invention, the structural element
may be cylindrical, or have an elliptical, oval, or polygonal
cross-section, for example a square, pentagon, hexagon, or
octagon.
[0055] In some embodiments, portions of structural element 204 may
be lowered onto bottom 216 of water 212. In some embodiments, water
212 has a depth of at least about 1000 meters, at least about 2000
meters, at least about 3000 meters, or at least about 4000 meters.
In some embodiments, water 212 has a depth up to about 10,000
meters.
[0056] In some embodiments of the invention, structural element 204
may be a pipeline, a crude oil flowline, a mooring line, a riser, a
tubular, or any other structural element installed in a body of
water. In some embodiments, structural element 204 may have a
diameter from about 0.1 to about 5 meters, and a length from about
1 to about 200 kilometers (km). In some embodiments, structural
element 204 may have a length to diameter ratio from about 100 to
about 100,000. In some embodiments, structural element 204 may be
composed from about 50 to about 30,000 tubular sections, each with
a diameter from about 10 cm to about 60 cm and a length from about
5 m to about 50 m, and a wall thickness from about 0.5 cm to about
5 cm.
[0057] Those of skill in the art will appreciate that many
modifications and variations are possible in terms of the disclosed
embodiments, configurations, materials and methods without
departing from their spirit and scope. Accordingly, the scope of
the claims appended hereafter and their functional equivalents
should not be limited by particular embodiments described and
illustrated herein, as these are merely exemplary in nature.
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