U.S. patent application number 12/065548 was filed with the patent office on 2009-09-03 for strake systems and methods.
Invention is credited to Donald Wayne Allen, Stephen Paul Armstrong, Dean Leroy Henning, Damon Michael McMillan, David Wayne McMillan, Christopher Steven West.
Application Number | 20090220307 12/065548 |
Document ID | / |
Family ID | 37684976 |
Filed Date | 2009-09-03 |
United States Patent
Application |
20090220307 |
Kind Code |
A1 |
Allen; Donald Wayne ; et
al. |
September 3, 2009 |
STRAKE SYSTEMS AND METHODS
Abstract
There is disclosed 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.
Inventors: |
Allen; Donald Wayne;
(Richmond, TX) ; Armstrong; Stephen Paul;
(Houston, TX) ; Henning; Dean Leroy; (Needville,
TX) ; McMillan; Damon Michael; (Humble, TX) ;
McMillan; David Wayne; (Deer Park, TX) ; West;
Christopher Steven; (Pearland, TX) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
37684976 |
Appl. No.: |
12/065548 |
Filed: |
August 30, 2006 |
PCT Filed: |
August 30, 2006 |
PCT NO: |
PCT/US06/33872 |
371 Date: |
December 17, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60713981 |
Sep 2, 2005 |
|
|
|
Current U.S.
Class: |
405/216 |
Current CPC
Class: |
F16L 9/006 20130101;
E21B 17/01 20130101; B63B 35/03 20130101; F16L 1/123 20130101; B63B
2021/504 20130101; B63B 21/00 20130101; B63B 21/04 20130101; B63B
21/502 20130101 |
Class at
Publication: |
405/216 |
International
Class: |
E02D 5/60 20060101
E02D005/60 |
Claims
1. 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, the at least one ramp aligned along a longitudinal axis of
the structural element.
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 to each other.
4. The system of claim 1, wherein the structural element comprises
a plurality of sections threaded to each other.
5. The system of claim 1, wherein the at least one helical strake
about the structural element comprises at least three helical
strakes about the structural element.
6. The system of claim 1, wherein the at least one ramp comprises a
plurality of ramps aligned along a longitudinal axis of the
structural element, the ramps adapted to interface with a stinger
and/or a roller.
7. The system of claim 1, wherein the at least one ramp comprises a
first set of ramps and a second set of ramps, the first set and the
second set aligned along a longitudinal axis of the structural
element, the first set adapted to interface with a first roller,
and the second set adapted to interface with a second roller
azimuthally spaced apart from the first roller.
8. The system of claim 1, wherein a first end of the at least one
helical strake is attached to a first collar, and a second end of
the at least one helical strake 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 helical strake about the
structural element; attaching at least one ramp to the structural
element and/or the at least one helical strake, the at least one
ramp to provide a transition from the structural element to the
helical strake, the at least one ramp aligned along a longitudinal
axis of the structural element; and moving the structural element,
the ramp, and the strake over a roller, so that the at least one
ramp provides a transition from the structural element to the
helical strake where the roller interfaces with the structural
element, the ramp, and the strake.
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 the at least one ramp comprises
a plurality of ramps aligned along a longitudinal axis of the
structural element, where the roller interfaces with the structural
element.
15. The method of claim 9, wherein the at least one ramp comprises
a first set of ramps and a second set of ramps, the first set and
the second set aligned along a longitudinal axis of the structural
element, the first set adapted to interface with a first roller,
and the second set adapted to interface with a second roller
azimuthally spaced apart from the first roller.
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.
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. The vibrations may be larger in the
transverse (to flow) direction; however, in-line vibrations can
also cause stresses, which may sometimes be larger than those in
the transverse direction.
[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. Currently available strake
elements and fairings cover an entire circumference of a
cylindrical element or may be clamshell shaped to be installed
about the circumference.
[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 may be 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] There is a need in the art for an improved apparatus and
method for suppressing vibration. There is another need in the art
of apparatus for and new and improved methods of installing strake
elements for suppressing vibration in a flowing fluid environment.
There is another need in the art of apparatus for and 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 of apparatus for and 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.
[0013] 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
[0014] One aspect of the invention provides 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.
[0015] Another aspect of the invention provides a method of
installing a structural element in a body of water comprising
attaching at least one helical strake about the structural element,
attaching at least one ramp to the structural element and/or the at
least one helical strake, the at least one ramp to provide a
transition from the structural element to the helical strake, and
moving the structural element, the ramp, and the strake over a
roller, so that the at least one ramp provides a transition from
the structural element to the helical strake where the roller
interfaces with the structural element, the ramp, and the
strake.
[0016] Advantages of the invention include one or more of the
following:
[0017] improved apparatuses and methods for suppressing
vibration;
[0018] improved methods of installing strake elements for
suppressing vibration in a flowing fluid environment;
[0019] 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; and
[0020] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 illustrates a system for installing a structural
element in a body of water in an S-lay configuration.
[0022] FIG. 2 illustrates a system for installing a structural
element in a body of water in an S-lay configuration.
[0023] FIGS. 3a and 3b illustrate a structural element with
strakes.
[0024] FIGS. 4a-4c illustrate a structural element with strakes and
ramps traveling over a stinger.
[0025] FIGS. 4d and 4e illustrate a structural element with strakes
and ramps.
DETAILED DESCRIPTION OF THE INVENTION
[0026] In one embodiment, there is disclosed 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. 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,
the at least one helical strake about the structural element
comprises at least three helical strakes about the structural
element. In some embodiments, the at least one ramp comprises a
plurality of ramps aligned along a longitudinal axis of the
structural element, the ramps adapted to interface with a stinger
and/or a roller. In some embodiments, the at least one ramp
comprises a first set of ramps and a second set of ramps, the first
set and the second set aligned along a longitudinal axis of the
structural element, the first set adapted to interface with a first
roller, and the second set adapted to interface with a second
roller azimuthally spaced apart from the first roller. In some
embodiments, a first end of the at least one helical strake is
attached to a first collar, and a second end of the at least one
helical strake is attached to a second collar, the first collar and
the second collar attached about the structural element.
[0027] In one embodiment, there is disclosed a method of installing
a structural element in a body of water comprising attaching at
least one helical strake about the structural element, attaching at
least one ramp to the structural element and/or the at least one
helical strake, the at least one ramp to provide a transition from
the structural element to the helical strake, and moving the
structural element, the ramp, and the strake over a roller, so that
the at least one ramp provides a transition from the structural
element to the helical strake where the roller interfaces with the
structural element, the ramp, and the strake. 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, the at least one ramp comprises a
plurality of ramps aligned along a longitudinal axis of the
structural element, where the roller interfaces with the structural
element. In some embodiments, the at least one ramp comprises a
first set of ramps and a second set of ramps, the first set and the
second set aligned along a longitudinal axis of the structural
element, the first set adapted to interface with a first roller,
and the second set adapted to interface with a second roller
azimuthally spaced apart from the first roller. 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.
[0028] 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. Strakes 206 are
attached to structural element 204 to dampen any vortex induced
vibration of structural element 204.
[0029] Referring now to FIGS. 3a-3b, in some embodiments of the
invention, structural element 304 is illustrated. Structural
element 304 encloses passage 302. Strake elements 306a, 306b, and
306c may be mounted about the circumference of structural element
304. Strake elements 306a-306c serve to inhibit vortex induced
vibration when structural element 304 is in a flowing fluid
stream.
[0030] Structural element 304 has outside diameter D 328. Strake
elements 306a-306c 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 1
D to about 10 D. In some embodiments of the invention, pitch L 332
may be from about 10 to about 500 cm.
[0031] 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.
[0032] In some embodiments of the invention, strakes 306a-306c may
be made of a polymer, such as a thermoplastic polymer or a
thermosetting polymer, for example polypropylene, polyethylene,
other polyolefins, or co-polymers of olefins. In some embodiments
of the invention, strakes 306a-306c may be made of a composite,
such as fiberglass or carbon fiber composite. In some embodiments
of the invention, strakes 306a-306c may be made of a metal, such as
steel or aluminum.
[0033] In some embodiments of the invention, strakes 306a-306c may
be attached to a collar, pipe, shell, or other support apparatus.
The support apparatus and strakes 306a-306c may then be installed
about structural element 304.
[0034] 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.
[0035] 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 strakes 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.
[0036] Referring now to FIG. 4c, in some embodiments of the
invention, structural element 404 of FIG. 4b has moved further
along so that strake 406b is interfacing with roller 419b, and
strake 406c is interfacing with roller 419a. Ramps 408b are
provided adjacent strake 406b, and ramps 408c are provided adjacent
strake 406c. Ramps 408b and 408c are adapted to interface with
rollers 419a and 419b to lift structural element 404 and provide a
smooth transition from the outside surface of structural element
404 to the height of strakes 406b and 406c, so that the strakes are
not damaged when they encounter the rollers.
[0037] Referring now to FIG. 4d, in some embodiments of the
invention, a side view of structural element 404 is illustrated.
Line 405 indicates where roller 419b encounters structural element
404. Ramps 408a, 408b, 408c, and 408d are provided along line 405,
to provide a smooth transition of lifting and lowering structural
element when it encounters roller 419b, so that strakes 406a, 406b,
and 406c are not damaged. Similar ramps may be provided on the
opposite side of structural element 404 where roller 419a
encounters structural element 404.
[0038] Referring now to FIG. 4e, in some embodiments of the
invention, a different side view of the structural element 404
illustrated in FIG. 4d is shown. In this view, line 405 where
roller 419b encounters the structural element is at the top, so
that the tapering of ramps 408a, 408b, 408c, and 408d may be seen.
The ramps provide a smooth transition from the outside surface of
structural element 404 to the height of each of the strakes, and
then back to the outside surface of the structural element 404 to
the roller 419b, so that the strakes are not damaged when they
encounter the roller.
[0039] In some embodiments of the invention, strakes 406a-406c may
be attached to a collar, pipe, shell, or other support apparatus.
The support apparatus and strakes 406a-406c may then be installed
about structural element 404. The ramps provide a smooth transition
from the outside surface of the support apparatus to the height of
each of the strakes, and then back to the outside surface of the
support apparatus to the roller 419b, so that the strakes are not
damaged when they encounter the roller.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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
10 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.
[0047] 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.
* * * * *