U.S. patent application number 11/575532 was filed with the patent office on 2009-03-26 for bend stiffener.
This patent application is currently assigned to MARINE SUBSEA GROUP A.S.. Invention is credited to Jan Egeland, Erik Godoy.
Application Number | 20090080982 11/575532 |
Document ID | / |
Family ID | 35057635 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090080982 |
Kind Code |
A9 |
Godoy; Erik ; et
al. |
March 26, 2009 |
Bend Stiffener
Abstract
A bend stiffener (7) is described, which surrounds the end
portion of an elongate, essentially cylindrical object, as for
instance a flexible pipe (2) or a cable, extending from a subsea
installation to a surface vessel, and is connected to an end piece
(1) or end flange of the pipe (2) at a connection to the vessel,
wherein the bend stiffener (7) is provided by a plurality of inner,
essentially cylindrical clamps (5) made having a longitudinal
groove (8) for receiving spring rods (3) in their outer surface,
which clamps (5) surround the pipe (2), and there is provided a
plurality of outer, essentially cylindrical clamps (6) which in
their inner surface are made having longitudinal grooves (8) for
receiving the spring rods (3), the grooves (8) in the inner and
outer clamps (5, 6) corresponding to each other when the outer
clamp (6) is mounted around the inner clamp (5), and a plurality of
clamp sets (5, 6) are arranged spaced apart from each other in
vicinity of the end piece (1), the spring rods (3) being secured
(4) in the end piece (1) or the flange of the pipe (2), or an
adapted arrangement on the cable, and extending longitudinally
along the pipe (2) or the cable, through the grooves (8) in the
inner and outer clamps (5, 6), and the outer clamps (6) are secured
to the inner clamps (5) and lock the spring rods (3) relative to
the inner clamps (5) and the pipe (2) or the cable.
Inventors: |
Godoy; Erik; (Lillesand,
NO) ; Egeland; Jan; (Stavanger, NO) |
Correspondence
Address: |
VOLPE AND KOENIG, P.C.
UNITED PLAZA, SUITE 1600
30 SOUTH 17TH STREET
PHILADELPHIA
PA
19103
US
|
Assignee: |
MARINE SUBSEA GROUP A.S.
Strandgaten 3
Andalsnes
NO
N-6300
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20070292214 A1 |
December 20, 2007 |
|
|
Family ID: |
35057635 |
Appl. No.: |
11/575532 |
Filed: |
September 19, 2005 |
PCT Filed: |
September 19, 2005 |
PCT NO: |
PCT/NO05/00345 |
371 Date: |
August 29, 2007 |
Current U.S.
Class: |
405/224.2 |
Current CPC
Class: |
E21B 17/017
20130101 |
Class at
Publication: |
405/224.2 |
International
Class: |
E02D 5/62 20060101
E02D005/62 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 23, 2004 |
NO |
20043980 |
Claims
1. A bend stiffener which surrounds the end portion of an elongate,
essentially cylindrical object, as for instance a flexible pipe or
a cable, extending from a subsea installation to a surface vessel,
and is connected to an end piece or end flange of the pipe at a
connection to the vessel, characterised in that the bend stiffener
is provided by a plurality of inner, essentially cylindrical clamps
made having a longitudinal groove for receiving spring rods in
their outer surface, which clamps surround the pipe, and there is
provided a plurality of outer, essentially cylindrical clamps which
in their inner surface are made having longitudinal grooves for
receiving the spring rods, the grooves in the inner and outer
clamps corresponding to each other when the outer clamp is mounted
around the inner clamp, and a plurality of clamp sets are arranged
spaced apart from each other in vicinity of the end piece, the
spring rods being secured in the end piece or the flange of the
pipe, or an adapted arrangement on the cable, and extending
longitudinally along the pipe or the cable, through the grooves in
the inner and outer clamps, and the outer clamps (6) are secured to
the inner clamps and lock the spring rods relative to the inner
clamps and the pipe or the cable.
2. A bend stiffener as disclosed in claim 1, characterised in that
the spring rods are made of an elastic material of a suitable
metal, metal alloy, or a composite material or fibre-reinforced
plastic.
3. A bend stiffener as disclosed in claim 2, characterised in that
the metal is titanium, or that the material is a carbon fibre or
glass fibre reinforced plastic.
4. A bend stiffener as disclosed in claim 1, characterised in that
at a distance from the end piece there is provided a rear section
or end cone which surrounds the pipe or the cable, which end cone
in a cylindrical edge area facing the end piece is provided with
openings for receiving the end portions of freely projecting spring
rods.
5. A bend stiffener as disclosed in claim 1, characterised in the
inner and/or the outer clamp being provided by segments which are
assembled so as to surround an object.
6. A bend stiffener as disclosed in claim 1, characterised in that
the end cone consists of segments.
7. A bend stiffener as disclosed in claim 1, characterised in that
sensors are provided on one or more of the spring rods to monitor
motions and angular displacement of the bend stiffener.
8. A bend stiffener as disclosed in claim 9, characterised in that
the sensor is a strain gauge, or a fibre optic element that is
integral with the spring rod itself.
9. A bend stiffener as disclosed in claim 1, characterised in that
the outer clamp is secured by a suitable retaining device, for
example a retaining band or locking band.
10. A bend stiffener as disclosed in claim 1, characterised in that
the spring rods have the same or different lengths, and/or that the
same or different materials are used in the spring rods in one and
the same bend stiffener.
Description
[0001] The invention relates to a bend stiffener which surrounds
the end portion of an elongate, essentially cylindrical object, as
for instance a flexible pipe or a cable, extending from a subsea
installation to a surface vessel, and is connected to an end piece
or end flange of a pipe at a connection to the vessel, as disclosed
in the preamble of independent claim 1.
[0002] As examples of related art, reference can be made to U.S.
Pat. Nos. 3,252,192, 5,161,828 and 5,439,323, of which the '828
patent seems to be closest to the invention. This document
describes a structure for stiffening a connection under water.
However, the stiffened elements are secured in fixed flanges on
each respective coupling part, and this structure does not have any
clamps as in the invention.
[0003] Today, in offshore petroleum production at great ocean
depths, flexible pipes and cables/umbilical lines, generally
referred to respectively as risers and umbilicals, are often used
for transport of liquids and gas and for energy supply and signal
transmission. Such flexible pipes and umbilicals typically connect
a surface vessel such as an FPSO (Floating Production Storage
Offloading), production platform, rig or buoy to wellheads or other
installations on the seabed.
[0004] Because of the motions of the vessel and ocean currents, the
pipes and umbilicals will be subjected to mechanical stresses which
may result in fatigue fractures. It is especially the area in the
immediate vicinity of the connection to the surface vessel that is
the weak point. To avoid damage and failure of the connection, it
is usual to install a bend stiffener immediately behind the
connection point at the end of the pipe or umbilical. These bend
stiffeners are traditionally constructed as a slightly conical,
cylindrically shaped tube. The material as a rule is an elastic
material such as polyurethane. Bend stiffeners of this type
undoubtedly have limitations and disadvantages: [0005] The bend
stiffener must be mounted on the pipe or umbilical before the end
flange (end connector) can be mounted. This is a disadvantage both
as regards logistics and transport. [0006] The pipe or umbilical
must be cut if the bend stiffener has to be replaced. This involves
extra work and substantial costs. [0007] A compact bend stiffener
which surrounds a pipe carrying a liquid (oil) of high temperature
will have a thermally insulating effect. This may result in local
high temperatures which could be detrimental to both the materials
of the pipe and the materials of the bend stiffener itself.
[0008] The object of the invention is to remedy the problems of the
prior art, and this is achieved with a bend stiffener of the type
mentioned above which is characterised in that the bend stiffener
is provided by a plurality of inner, essentially cylindrical clamps
made having longitudinal grooves for receiving spring rods in their
outer surface, which clamps surround the pipe, and there is
provided a plurality of outer, essentially cylindrical clamps which
in their inner surface are made having longitudinal grooves for
receiving the spring rods, the grooves in the inner and the outer
clamps corresponding to each other when the outer clamp is mounted
around the inner clamp, and a plurality of clamp sets are arranged
spaced apart from each other in vicinity of the end piece, the
spring rods being secured in the end piece or flange of the pipe,
or an adapted arrangement on the cable, and extending
longitudinally along the pipe or cable, through the grooves in the
inner and outer clamps, and the outer clamps are secured to the
inner clamps and lock the spring rods relative to the inner clamps
and the pipe or cable.
[0009] Advantageous embodiments of the invention are disclosed in
the dependent claims.
[0010] In the bend stiffener according to the invention, elastic
spring rods of a suitable material such as titanium or
fibre-reinforced plastic are used. This gives the following
advantages: [0011] The bend stiffener can be mounted after the end
flange (end connector) has been mounted. [0012] It is possible to
remove the bend stiffener or replace components thereof without
having to cut the pipe or the umbilical. [0013] The bend stiffener
will not form a thermally insulating sheath around the pipe. [0014]
The stiffness or characteristic of the bend- stiffener can be
adjusted by altering the number of spring rods, the diameter of the
rods, the material or the length of the rods.
[0015] The invention will now be described with reference to the
drawings, wherein:
[0016] FIG. 1 is a perspective view of a bend stiffener according
to the invention mounted on a flexible pipe;
[0017] FIGS. 2-5 are perspective views of, respectively, an inner
clamp, an outer clamp, spring rods arranged on inner clamps which
surround a flexible pipe and the bend stiffener fully mounted with
the aid of the outer clamps.
[0018] Although the exemplary embodiment of the invention refers to
a bend stiffener for a flexible pipe, the concept for an umbilical
will basically be identical, except that the connector at the end
(the end flange) will be different.
[0019] In FIG. 1 the reference numeral 1 indicates an end piece or
end flange of a flexible pipe 2, for example, a riser. The
reference numeral 3 indicates a spring rod, 4 a fastening of the
spring rods 3, 5 an inner clamp, 6 an outer clamp, 7 the bend
stiffener itself and 12 a rear section or end cone. FIGS. 2 and 3
indicate respectively the outer grooves 8 for the spring rods on
the inner clamp 5 and inner grooves 8 for the spring rods 3 on the
outer clamp 6.
[0020] When providing a bend stiffener 7, an end piece 1 must be
mounted on a pipe 2 that is to be protected by the bend stiffener
7. The end piece 1 is fastened to the pipe 2 in a conventional
manner. A rear section or end cone 12 is mounted on the pipe 2,
preferably at a distance from the end piece 1. This rear section 12
may consist of cone segments which, in a cylindrical edge area
facing the end piece 1, are provided with openings to
receive/surround the end portions of spring rods 3 which project
beyond the mounting clamps 5 and 6 of the bend stiffener 7 on the
pipe 2 that are furthest from the end piece 1. The rear section
thus functions primarily as a guard or shield for these end
portions so that they do not protrude and potentially cause
problems in that rope or other items become caught or that the ends
of the rods 3 hit and damage other objects such as other pipes or
the like, but it also gives the bend stiffener 7 a more streamlined
termination. An integral fastening 4 for the spring rods 3 is
provided in the end piece 1. The spring rods are preferably round
rods made of titanium or fibre-reinforced plastic such as carbon
fibre or glass fibre reinforced plastic, or another suitable
material or alloy. The fastening 4 may be provided by providing
holes in the end piece 1 for receiving the spring rods 3 that may
be formed having a conical portion which rests against the end
piece 1 and a threaded portion that is arranged through the holes
so that the threads can engage with locking nuts, indicated by the
reference numeral 4. If fibre-reinforced plastic or the like is
used for the spring rods 3, it may be expedient to provide the rod
ends with a steel sleeve or the like to be able to provide the
desired fastening to the end piece 1. A plurality of essentially
cylindrical inner clamps 5 with outer longitudinal grooves 8 for
receiving spring rods 3 are placed around the pipe 2. Over these
inner clamps are likewise arranged essentially cylindrical outer
clamps 6 with corresponding inner longitudinal grooves 8 for
receiving spring rods 3. The clamps 5 and 6 may be produced of any
suitable material, and consist preferably of two or more segments
that are assembled so as to provide the cylindrical shape. The
inner clamps 5 are installed first. After they have been installed,
the spring rods 3 are mounted. The outer clamps 6 are secured on
the outside of the inner clamps 5, which locks the spring rods 3
relative to the inner clamps 5 and the pipe 2. The outer clamps 6
are provided with a suitable retaining device, in FIG. 3 indicated
as a retaining band 11, so that they are held securely fastened in
place.
[0021] When the pipe 2 bends with the bend stiffener 7, the spring
rods 3 will slide axially relative to the clamps 5 and 6. To ensure
minimal frictional force between the spring rods 3 and the clamps 5
and 6, liners of a suitable material may be used (not shown) which
are mounted between the clamps 5 and 6 and the spring rods 3.
[0022] The stiffness of the bend stiffener 7 can be adjusted by
altering the number of spring rods 3. Furthermore, the diameter of
the rods 3, materials selection and the length of the rods 3 will
be of importance. Similarly, the longitudinal distance between
respective sets of clamps 5, 6 can be altered and the stiffness can
also be decreased, for example, towards the end of the bend
stiffener 7 by having some rods shorter than others. The
characteristic or stiffness of the bend stiffener 7 can also be
affected by using rods 3 of different materials in the same
unit.
[0023] It may be desirable to monitor motions and angular
displacement of the bend stiffener 7. This can, for example, be
used to obtain an indication of the pipes 2 (or cables) themselves,
to estimate or predict service life of the bend stiffener 7 and to
register extreme loads such as accident loads. For monitoring of
this kind, it is necessary to mount sensors on some of the spring
rods 3. Strain gauges could be used on spring rods 3 of metal,
whilst fibre optic elements that are integral with the actual
spring rods 3 could be used on spring rods 3 of fibre-reinforced
plastic or composite material. Signals from the sensors are sent to
the surface vessel via telemetry cables.
[0024] The bend stiffener 7 according to the invention can be
provided in any suitable length, but the spring rods 3 typically
have a length in the range of 4 to 10 metres. The clamps 5 and 6
can be provided in any suitable material, in different dimensions
depending on the diameter of the object they are to surround, and
the number of rods that are used can also be chosen as
required.
* * * * *