U.S. patent application number 09/788667 was filed with the patent office on 2001-11-29 for circumferential-weld reinforcing device.
Invention is credited to Marchal, Philippe, Villatte, Ludovic.
Application Number | 20010045239 09/788667 |
Document ID | / |
Family ID | 8847173 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045239 |
Kind Code |
A1 |
Villatte, Ludovic ; et
al. |
November 29, 2001 |
Circumferential-weld reinforcing device
Abstract
The invention relates to a device reinforcing circumferential
welds 8 which join two contiguous pipes 6 and 7 in order to
increase the fatigue life of said welds by reducing mechanical
stresses in them when being subjected to periodic bending. The
device comprises a rigidifying element 10 which is firmly joined to
said pipes by a connection means 11, 13, said bush being made of
the same material as the pipes. The rigidifying element 10 consists
of a bush slipped over the two pipes 6, 7 opposite the weld 8. The
connection means is a hardening material 11 such as resin or cement
which is injected between bush and pipes and which is confined at
this site by shaping, in particular cold-forming, the bush's ends.
The application is to offshore hydrocarbon conveyance conduits
subjected to periodic loads.
Inventors: |
Villatte, Ludovic;
(Louveciennes, FR) ; Marchal, Philippe;
(Vaucresson, FR) |
Correspondence
Address: |
PARKHURST & WENDEL, L.L.P.
Suite 210
1421 Prince Street
Alexandria
VA
22314-2805
US
|
Family ID: |
8847173 |
Appl. No.: |
09/788667 |
Filed: |
February 21, 2001 |
Current U.S.
Class: |
138/172 ;
138/155; 138/175 |
Current CPC
Class: |
F16L 13/0272 20130101;
F16L 1/123 20130101; F16L 58/181 20130101; F16L 57/02 20130101;
F16L 13/04 20130101 |
Class at
Publication: |
138/172 ;
138/175; 138/155 |
International
Class: |
F16L 009/22 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2000 |
FR |
00.02078 |
Claims
1. A device reinforcing a circumferential weld (8) of two
contiguous pipes (6, 7) constituting a conduit for transporting
hydrocarbons at sea and comprising a rigidifying element (10) which
is firmly joined to said pipes by a connecting means (11), said
rigidifying element being slipped over the two pipes substantially
to be opposite the weld, characterized in that the connecting means
is mechanical and is implemented by shaping all or part (18, 19,
20) of the rigidifying element (10) onto the two pipes (6, 7).
2. Circumferential-weld reinforcing device as claimed in claim 1,
characterized in that said shaping is implemented substantially
near the ends and the middle portion of the rigidifying element
(10).
3. Circumferential-weld reinforcing device (8) as claimed in either
of claims 1 and 2, characterized in that an elastoplastic
interposed material (21) is inserted either linewise/spotwise or
continuously between the rigidifying element (10) and the pipes (6,
7) before shaping takes place in order to limit point stresses on
the pipes.
4. Reinforcing device as claimed in claim 3, characterized in that
the interposed material (21) is polypropylene or polyethylene or
soft steel.
5. Weld-reinforcing device as claimed in any of the above claims,
characterized in that the rigidifying element (10) is a
hollow-cylindrical element or bush.
6. A device reinforcing a circumferential weld (8) of two
contiguous pipes (6, 7) constituting a conduit for transporting
hydrocarbons at sea and comprising an anti-bending rigidifying
element (10) which is firmly joined to said pipes by a connection
means (11), said rigidifying element being slipped over the two
pipes substantially above each weld, characterized in that the
connection means is a filler material (11) inserted into the play
between the pipes (6, 7) and said rigidifying element (10) in order
to reduce the stresses caused by periodic bending of the
conduit.
7. Reinforcing device for a circumferential weld (8) as claimed in
claim 6, characterized in that the rigidifying element consists of
a bush (10) preferably made of the same material as the pipes (6,
7).
8. Reinforcing device for a circumferential weld (8) as claimed in
claim 7, characterized in that the filler material (11) is a
hardening material such as resin or cement.
9. Reinforcing device as claimed in either of claim 7 and 8,
characterized in that the filling material (11) is trapped in place
by shaping (16, 17) the ends of the bush (10).
Description
[0001] The technical field of the present invention applies to
hydrocarbon-carrying sea pipes and in particular to pipes being
periodically bent.
[0002] For water depths of several hundred meters, the pipe
material is selected from those allowing flexible pipes which well
withstand the dynamic loads resulting from ocean swells and
currents at the oil extraction site. However, at lower depths, this
design is more expensive on account of the unit-length cost of
flexible pipe.
[0003] The exhaustion of the offshore hydrocarbon reserves of
conventional operation has led to searches at great depths (of the
order of a kilometer). In this case oil conveyance very often is
assured by steel pipes used at every stage of extraction and in
particular by vertical pipes between the bottom and the sea's
surface: in English such pipes are called "risers". The
conventional architecture of such a complex is a floating platform
into which issue the risers of which the dynamic portion has a
length from several hundred meters to a few km. Technically and
economically these pipes must not be connected to a rigid structure
and must be dimensioned to withstand repetitive loads of large
amplitudes. In this geometry and in practice, the steel conduit is
considered flexible and therefore is able to withstand dynamic
loads at a lesser cost. However this technology is degraded by the
short fatigue life of the pipe welds: This conduit is constituted
of intermediate pipes about 12 m long each and for instance joined
end to end by circumferential welds
[0004] The life of a circumferential weld depends mainly on its
quality and on the periodic and dynamic loads it is subjected
to.
[0005] It is known that the fatigue life of the steel constituting
the pipes of a conduit is much higher than that of the welds: the
welds are susceptible to micro-cracks and then potentially may
rupture.
[0006] Accordingly it is the objective of the present invention to
create local reinforcements for the welded pipes to increase their
rigidity and decrease their shapes. Therefore the pipe conduit's
flexibility will be provided by its weld-free portions which are
much more fatigue-resistant.
[0007] Thus the invention relates to a device reinforcing a
circumferential weld of two contiguous pipes which are part of a
conduit which shall convey hydrocarbons at sea and comprising a
rigidifying element firmly joined by a connection means to said
pipes, said rigidifying element being slipped over the two pipes
substantially opposite the weld, said reinforcing device being
characterized in that the connection means is a mechanical one and
is implemented by part or all of the rigidifying element being
shaped directly onto the two pipes.
[0008] In one feature of the invention, said shape is implemented
substantially near the ends and median portion of the rigidifying
element.
[0009] In another feature of the invention, an elastoplastic
material is inserted prior to shaping between the rigidifying
element and the pipes either in localized or in continuous manner
to limit point stresses on the pipes.
[0010] In still another feature of the invention, the inserted
material consists of polypropylene or polyethylene or soft
steel.
[0011] In yet another feature of the invention, the rigidifying
element is a hollow element, or a sleeve.
[0012] In one embodiment variation of the invention, the invention
also relates to a rigidifying device for a two-pipe circumferential
weld which comprises a rigidifying element firmly joined by a
connection means to said pipes, where said rigidifying element is
slipped over the two pipes substantially above each weld, and said
reinforcing device is characterized in that the connection means
consists of a filler inserted into the play between the pipes and
said rigidifying element in order to reduce the stresses arising
from the periodic bending of the conduit.
[0013] Advantageously the reinforcing element consists of a bush
preferably of the same material as the pipes'.
[0014] Advantageously again, the filler is a hardening material
such as resin or cement.
[0015] Advantageously again, the filler is kept in place by shaping
the ends of the bush.
[0016] The invention offers the foremost advantage of improving the
pipe's fatigue life at the weld site.
[0017] Another advantage of the device of the invention is a
significant drop in the danger of rupture and hence danger of
production losses.
[0018] Another advantage is the increase in service life of the
conduits and hence lowering production costs.
[0019] Lastly the invention provides a simple and economic
design.
[0020] Other features and advantages of the invention are
elucidated in the following illustrative description relating to
the attached drawings.
[0021] FIG. 1 shows a deep hydrocarbon production site and the
hydrocarbon conveyance, FIG. 2 is a cross-section of a welded joint
of a conventional two-pipe assembly,
[0022] FIG. 3 is a cross-section of the reinforcing device of a
first embodiment of the invention,
[0023] FIG. 4 is a cross-section of the reinforcing device of a
second embodiment of the invention, and
[0024] FIGS. 5a, 5b show another embodiment variation of the
connection.
[0025] As indicated above, the invention only relates to improving
the fatigue strength of the welded joints while the static problem
does not arise. Therefore any action requiring welding the
rigidifying element or bush directly onto one of the pipes
(generally speaking a lap joint weld) must be avoided because
entailing substantial fatigue degradation: lap joint welds generate
micro-cracks and geometric stress concentrations substantially
reducing the pipes' fatigue life at these very sites.
[0026] The invention in particular applies to offshore hydrocarbon
conveyance conduits subjected to periodic loads.
[0027] FIG. 1 shows the application of the reinforcing device of
the invention to the offshore hydrocarbon conveyance conduit
subjected to periodic loads. Illustratively the conduit 5 is
mounted between a platform 4 and a well 1 on the sea's floor 2.
[0028] FIG. 2 shows two inner pipes 6 and 7 of the conduit 5 which
are joined end to end by a weld 8. As described above, the weld 8
is the seat of micro-cracks 9. The objective of the invention is
precisely to delay the propagation of these microcracks by
providing a reinforcing element that shall reduce the bending
stresses thanks to spreading the bending torque between the joint
and the bush.
[0029] FIG. 3 shows the conduit 5 fitted with a rigidification
device of a first embodiment mode and mounted opposite the weld 8
joining two contiguous pipes 6 and 7. This rigidifying device in
this case consists of a substantially cylindrical and hollow
element 10 called the "bush". This bush 10 is made of a material
offering mechanical properties substantially equivalent to those of
the inner pipe (steel as a rule) and its length is about 3 to
6-fold its diameter. Accordingly metallic materials exhibiting a
substantially similar Young's modulus may be used without affecting
the bush's behavior. The inside diameter must be adequate to allow
sliding the bush 10 opposite the weld 8. The expression "opposite
the weld" denotes positioning the two ends 14 and 15 of the bush 10
substantially symmetrically to the weld 8. The residual play 16
between the bush 10 and the inner pipes 6 and 7 is filled for
instance by injecting a hardening filler such as a resin or cement
or any other suitable material that shall assure a rigid connection
between the bush 10 and the inner pipes 6 and 7 and thereby
providing a high-performance mechanical link. It was found that
this connection assures shunting a large part of the bending torque
into the bush.
[0030] FIG. 4 shows the connection of a second embodiment mode in
its final shape. This configuration of the bush 10 and its general
characteristics are the same as those of the above embodiment. In
this mode however the ends 14 and 15 of the bush 10 are transformed
into a shape 16 preferably by cold shaping (crimping) to establish
contact between the bush and the inner pipes 6 and 7 over the
bush's full circumference. In this design the filler 11 then will
be confined between the bush and the pipes.
[0031] FIGS. 5a and 5b show two other embodiments of the connection
means which illustrate the mechanical connection between the bush
and the pipes. In these embodiment variations, the bush 10 is
shaped to be directly applied at three different sites on the two
pipes 6 and 7: at its free ends 18 and 20 and at its middle 19 to
establish a strictly mechanical connection by interposing a
material 21 between bush and pipes. The play between bush and pipes
therefore is eliminated at said three sites. The Figure shows that
this middle part is located exactly where the weld is. There may be
a requirement to clad beforehand the inner pipes 6 and 7 with an
interposing elastoplastic material 21 allowing locally spreading
the pressure at the critical points 18, 19 and 20 to lower the
danger of point stresses to the pipes. In FIG. 5a, the interposed
material 21a is applied discretely at three spots and in FIG. 5b
the material 21b is substantially spread out. In the same manner as
above, this design assures shunting much of the bending torque into
the bush. Illustratively this interposed material may be
polypropylene or polyethylene or soft steel.
[0032] Obviously the invention may be implemented also by combining
the above embodiment modes. The objective of the invention, namely
to rigidify the weld, therefore has been attained. Clearly as well,
regardless of a particular embodiment mode, the connection between
the mutually opposite bush 10 and pipes 6 and 7 may be improved by
surface treatment of said pipes.
* * * * *