U.S. patent application number 15/307795 was filed with the patent office on 2017-02-16 for subsea cooler.
The applicant listed for this patent is FMC Kongsberg Subsea AS. Invention is credited to Erik BAGGERUD, Idun Bente TILLER.
Application Number | 20170045315 15/307795 |
Document ID | / |
Family ID | 53052846 |
Filed Date | 2017-02-16 |
United States Patent
Application |
20170045315 |
Kind Code |
A1 |
BAGGERUD; Erik ; et
al. |
February 16, 2017 |
SUBSEA COOLER
Abstract
A subsea cooler has at least one pipe (1) and a housing (4). The
pipe has an inlet (2) and an outlet (3) for a fluid to be cooled
and comprises straight sections (5) connected by bend sections (6).
The housing (4) encloses at least a part of the pipe and comprises
an inner surface forming a flow channel (8) extending along and
surrounding the pipe. The flow channel (8) is fluidly connected to
an inlet (9) and an outlet (10) for a cooling fluid and a pumping
element for driving the cooling fluid through the flow channel (8).
At least one sacrificial anode (11) is positioned in the flow
channel (8) such that the sacrificial anode is in electrical
contact with the pipe (1).
Inventors: |
BAGGERUD; Erik; (Jar,
NO) ; TILLER; Idun Bente; (Asker, NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FMC Kongsberg Subsea AS |
Kongsberg |
|
NO |
|
|
Family ID: |
53052846 |
Appl. No.: |
15/307795 |
Filed: |
April 29, 2015 |
PCT Filed: |
April 29, 2015 |
PCT NO: |
PCT/EP2015/059343 |
371 Date: |
October 28, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 19/004 20130101;
F28D 7/106 20130101; F28D 7/14 20130101; F28D 7/10 20130101; E21B
36/001 20130101; E21B 41/0007 20130101 |
International
Class: |
F28F 19/00 20060101
F28F019/00; F28D 7/14 20060101 F28D007/14; F28D 7/10 20060101
F28D007/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 2014 |
NO |
20140561 |
Claims
1: A subsea cooler comprising: at least one pipe for a fluid to be
cooled, the pipe comprising a pipe inlet and a pipe outlet and
being formed of a number of straight sections connected by bend
sections; a housing which encloses at least a part of the pipe and
which comprises an inner surface that together with an outer
surface of the pipe forms a flow channel extending along and
surrounding the pipe; the flow channel being fluidly connected to
an inlet and an outlet for a cooling fluid and to a pumping element
for driving the cooling fluid through the flow channel; at least
one sacrificial anode which is positioned in the flow channel in
electrical contact with the pipe; wherein the flow channel
comprises at least one cavity which is configured to receive
corrosion products from the sacrificial anode.
2: A subsea cooler according to claim 1, wherein the flow channel
is formed by at least a first and second inner surfaces of the
housing, wherein the first inner surface extends along a straight
section of the pipe and the second inner surface extends along at
least part of a bend section on the outside of the bend section,
and wherein said sacrificial anode is arranged at the second inner
surface.
3: A subsea cooler according to claim 1, wherein the flow channel
is formed by at least first and second inner surfaces of the
housing, wherein the first inner surface extends along a straight
section of the pipe and the second inner surface extends along at
least part of a bend section on the outside of the bend section,
and wherein said sacrificial anode is arranged at the first inner
surface.
4: A subsea cooler according to claim 1, wherein each bend section
of the pipe is in electrical contact with a sacrificial anode.
5: A subsea cooler according to claim 1, wherein the at least one
sacrificial anode is electrically connected to the pipe.
6: A subsea cooler according to claim 5, wherein the at least one
sacrificial anode is electrically connected to the pipe via the
housing.
7: A subsea cooler according to claim 1, wherein the cavity is
arranged below a bend section.
8: A subsea cooler according to claim 1, further comprising a
number of longitudinally extending fins which are positioned
between the straight sections and the housing to thereby support
the pipe against the housing.
9: A subsea cooler according to claim 3, wherein said anode is at
least partly embedded in the first inner surface.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to compact cooler designs for
subsea applications.
BACKGROUND
[0002] Subsea coolers are well-known. Due to the environment in
which they are used, several challenges not commonly encountered in
non-subsea coolers must be addressed. Examples of subsea coolers,
for cooling a well flow such as a hydrocarbon flow, are disclosed
in for example the applicant's own published application WO
2011008101 A1, which is hereby incorporated by reference in its
whole, or in Norwegian patent NO 330761 B1. Other known subsea
coolers are described in WO 2010110674 A2 and WO 2010110676 A2.
[0003] A common solution for subsea coolers is the use of passive
coolers. In these solutions the fluid to be cooled, e.g. a well
flow, is led through multiple pipes arranged in a large common
volume of cooling fluid, i.e. seawater. Large amounts of seawater
pass through the common volume at a relatively slow rate due to
natural convection, i.e. the seawater rises through the cooler
since it is heated by the fluid to be cooled. Thus, it is difficult
to regulate or control the cooling effect of passive coolers.
Further, the design of passive coolers makes it difficult to obtain
a compact cooler due to restraints caused by the rate of heat
transfer, the required distance between the cooling fluid pipes
etc.
[0004] A potential solution to at least some of the disadvantages
of a passive cooler solution is the use of active coolers having a
"pipe-in-pipe" solution. In these coolers, a first pipe containing
the fluid to be cooled is surrounded by a second pipe (or an
element having a channel through which the first pipe is arranged).
The inner wall of the second pipe (or element channel) and the
outer wall of the first pipe delimit a flow channel through which
the cooling fluid is passed. In a "pipe-in-pipe" solution, the rate
of the cooling fluid is controlled by a pump. The advantages of a
"pipe-in-pipe" solution are the increased temperature control (i.e.
increased control of cooling effect) and, as a consequence of being
an active cooler, the possibility of designing a more compact
cooler.
[0005] However, the use of a "pipe-in-pipe" solution with seawater
as the cooling fluid presents corrosion problems not present in
passive coolers. First of all, it is difficult to protect the inner
pipes against corrosion due to the restricted flow channels, and
secondly, corrosion may have detrimental effects since corrosion
products may obstruct the flow channel.
[0006] Based on the prior art, there is a need for a compact subsea
cooler providing increased temperature control.
[0007] The present invention provides a subsea cooler design which
alleviates at least some of the disadvantages related to the use of
"pipe-in-pipe" coolers subsea.
SUMMARY OF THE INVENTION
[0008] The present invention provides a subsea cooler design which
alleviates at least some of the disadvantages of the prior art
coolers.
[0009] The invention is defined in the attached claims, and in the
following:
[0010] In a main embodiment, the invention provides a subsea cooler
comprising at least one pipe and a housing, wherein [0011] the pipe
have an inlet and an outlet for a fluid to be cooled, and comprises
straight sections connected by bend sections; [0012] the housing
encloses at least a part of the pipe, and comprises an inner
surface forming a flow channel extending along and surrounding the
pipe; and [0013] the flow channel is fluidly connected to an inlet
and an outlet for a cooling fluid and a pumping element for driving
the cooling fluid through the flow channel, wherein at least one
sacrificial anode is positioned in the flow channel such that said
sacrificial anode is in electrical contact with the pipe.
[0014] In the context of the present application, the term fluidly
connected in relation to the flow channel is intended to mean a
connection, such as a conduit, which ensures that cooling fluid is
transferred from the inlet to the flow channel and from the flow
channel to the outlet.
[0015] In another embodiment of the subsea cooler according to the
invention, the flow channel is formed by at least a first inner
surface and at least a second inner surface of the housing, and
where the first inner surface extend along a straight section of
the pipe, and the second inner surface extend along at least parts
of a bend section, wherein a sacrificial anode is arranged at the
second inner surface.
[0016] The second inner surface may form at least parts of a flow
channel along, and surrounding, a bend section. The second inner
surface may be provided at the outside of a bend to form at least
parts of the flow channel around the bend. The first and second
inner surfaces may form a continuous flow channel for a fluid at
the outside of the connected straight and bend sections of the
pipe.
[0017] The second inner surface may also be described as being
situated on the outside of a bend section. The term "outside of a
bend section" is intended to mean that the second inner surface of
the housing is situated at a distance to the bend section pipe and
also being arranged at the outside of the bend of said bend
section. At least parts of the second inner surface may
advantageously be perpendicular to the first inner surface.
[0018] In yet another embodiment of the subsea cooler according to
the invention, the flow channel is formed by at least a first inner
surface and at least a second inner surface of the housing, and
where the first inner surface extend along a straight section of
the pipe, and the second inner surface extend along at least parts
of a bend section, wherein a sacrificial anode is arranged at the
first inner surface, preferably the anode is partly embedded in the
first inner surface such that a substantially unobstructed flow
channel is obtained.
[0019] In yet another embodiment of the subsea cooler according to
the invention, each bend section of the pipe is in electrical
contact with a sacrificial anode.
[0020] In yet another embodiment of the subsea cooler according to
the invention, the at least one sacrificial anode is in electrical
contact with the pipe via an electrical conductor, such as a
wire.
[0021] In yet another embodiment of the subsea cooler according to
the invention, at least a part of at least one of the inner
surfaces of the housing is made in a non-metallic material.
[0022] In yet another embodiment of the subsea cooler according to
the invention, a further electrical conductor connects the at least
one sacrificial anode to the pipe, such that a closed circuit is
formed between the pipe and the anode.
[0023] In yet another embodiment of the subsea cooler according to
the invention, the cross-sectional area of the flow channel is
larger at the bend sections than at the straight sections, said
cross-section in a plane perpendicular to a centerline of the
pipe.
[0024] In yet another embodiment of the subsea cooler according to
the invention, the flow channel comprises at least one cavity
arranged such that, during use, corrosion products from the
sacrificial anode may accumulate in said cavity by gravitation
and/or by being pushed to said cavity by a cooling fluid flow.
[0025] In yet another embodiment of the subsea cooler according to
the invention, the cavity is arranged below a bend section.
[0026] In yet another embodiment of the subsea cooler according to
the invention, the straight sections of the pipe comprises multiple
fins in the longitudinal direction of the corresponding straight
section, preferably the height (h) of the fins is such that the
fins are able to support the pipe against the first inner
surface.
[0027] In yet another embodiment of the subsea cooler according to
the invention, the subsea cooler comprises multiple parallel
arranged pipes, wherein the outlets of the pipes are connected to a
common outlet header pipe and the inlets of the pipes are connected
to a common inlet header pipe.
[0028] In yet another embodiment of the subsea cooler according to
the invention, the housing have multiple housing elements
comprising at least a first housing element which include the first
inner surface and at least a second housing element which include
at least one of the second inner surfaces.
[0029] In yet another embodiment of the subsea cooler according to
the invention, the first housing element comprises a block having
multiple through-bores, each bore comprising a first inner
surface.
[0030] Preferably, the second housing element is arranged to
enclose multiple parallel bend sections.
[0031] In yet another embodiment of the subsea cooler according to
the invention, the second housing element comprises at least one
cavity arranged such that, during use, corrosion products from the
sacrificial anode may accumulate in said cavity by gravitation.
SHORT DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 shows a longitudinal and a transverse cross-section
of a typical pipe-in-pipe arrangement.
[0033] FIG. 2 shows the transverse cross-sections of two
alternative pipe-in-pipe arrangements.
[0034] FIGS. 3a and 3b is a cross-sectional view of a subsea cooler
according to the invention.
[0035] FIGS. 4a-4d show different sectional views of the subsea
cooler illustrated in FIGS. 3a and 3b.
[0036] FIG. 5 is a cross-sectional view of an alternative
embodiment of a subsea cooler according to the invention.
[0037] FIGS. 6a-6e show different sectional views of a subsea
cooler according to the invention having an alternative housing
solution.
[0038] FIG. 7 is a cross-sectional view of a flow channel
comprising a cavity for corrosion products.
[0039] FIG. 8 is a transverse cross-sectional view of two
alternatives of pipe-in-pipe solutions comprising longitudinal
fins.
DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION
[0040] The principle of pipe-in-pipe cooler solutions is shown in
FIG. 1, wherein a first pipe 1 is surrounded by a second pipe, or
housing 4. A flow channel 8 is formed between an inner surface 7 of
the housing and the first pipe. In use, a cooling fluid is
transported through the flow channel 8, while a fluid to be cooled
(e.g. a process fluid such as gas and/or oil) is transported
through the first pipe 1. Commonly, the direction of the two
separate fluid flows is opposite the other, i.e. the flows are
counter-current. As shown in FIG. 2, the design of the inner
surface of the housing 4 may be varied to obtain different
transverse cross-sections of the flow channel 8.
[0041] A cross-section of a subsea cooler according to the
invention is shown in FIG. 3a. The cooler comprises a pipe 1
surrounded by a housing 4. The pipe comprises both straight
sections 5 and bend sections 6. A flow channel 8 is formed between
an inner surface 7,13 of the housing and the pipe. The pipe 1
includes an inlet 2 and an outlet 3 for a fluid to be cooled, e.g.
a process fluid, and the flow channel comprises an inlet 9 and an
outlet 10 for a cooling fluid, e.g. seawater. The inlet 9 of the
flow channel is connected to a pumping element 20. In cooler
solutions for subsea applications corrosion is a common problem,
especially when the cooler fluid is seawater. In a cooler according
to the invention, i.e. a pipe-in-pipe solution, corrosion of the
pipe is especially important to avoid since clogging of the flow
channel may easily occur due to the restricted cross-sectional area
of the flow channel 8. In this embodiment, to alleviate or solve
this problem, sacrificial anodes 11 are arranged outside of each
bend section 6, and connected to the pipe via an electrical
conductor 12. In addition, sacrificial anodes are arranged near the
inlet 2 and the outlet 3 of the pipe. A magnified view of a bend
section 6 connected to a sacrificial anode 11 outside of said
section is shown in FIG. 3b. The anode is connected to the pipe via
an electrical conductor (e.g. a wire) and a clamp 23. The
electrical conductor may be any connection or contact allowing an
electrical current to pass between the pipe 1 and the sacrificial
anode. For instance if the pipe 1 at some point is in contact with
the housing 4 (e.g. pipes having fins 15, FIG. 8), the housing is
made of a metal, and the anode 11 is in contact with the housing 4,
a separate connection between the anode and pipe is redundant since
electrical current may pass from the pipe via the housing to the
anode.
[0042] Sectional views of the cooler in FIG. 3 are shown in FIG.
4a-4d. A top section, a mid section and a bottom section is
outlined in FIG. 4a. The sectional views of FIGS. 4b-4d are shown
in a horizontal plane perpendicular to the vertical plane of the
cross-section in FIG. 4a. The use of the terms vertical and
horizontal are only for illustrative purposes and does not imply
any required direction for arranging the cooler during use. The
cooler comprises multiple parallel pipes 1. The outlet 3 of each
pipe is connected to a common outlet header pipe 16, and the inlet
2 of each pipe is connected to a common inlet header pipe 17. The
flow channels 8 are fluidly connected to the flow channel inlet 9
via a common inlet header 21, and to the flow channel outlet 10 via
a common outlet header 22.
[0043] An alternative embodiment of a cooler according to the
invention is shown in FIG. 5. In this embodiment, the sacrificial
anodes 11 are arranged along the straight sections 5 of the pipe 1,
in addition to sacrificial anodes arranged near the inlet 2 and the
outlet 3 of the pipe. When the anodes 11 are arranged in the flow
channel 8 at the straight sections 5 it is preferred that the
anodes are partly embedded in the inner surface 7 of the housing.
By having the anodes partly embedded, preferably such that only one
surface of the anode is exposed to the flow channel 8 (i.e. the
surface is flush with the inner surface of the housing), the flow
channel is not substantially restricted by the anodes.
[0044] A further embodiment of a cooler according to the invention
is shown in FIG. 6a-e. A top section, a mid section, a bottom
section and an A-A cross-section are outlined in FIG. 6a. The
sectional views of FIGS. 6b-6d are shown in a horizontal plane
perpendicular to the vertical plane of the cross-section in FIG.
6a. The use of the terms vertical and horizontal are only for
illustrative purposes and does not imply any required direction for
arranging the cooler during use. In this cooler the housing is made
up of multiple housing elements 18,24. The first housing element is
a block 18 comprising multiple through-bores 19. The through-bores
are for accommodating at least parts of the straight section of
each pipe. A second housing element comprises longitudinal boxes
24. The boxes cover multiple parallel bend sections 6, and form
fluid tight connections with the block 18, thereby forming multiple
flow channels 8 surrounding the pipes 1. In this embodiment,
sacrificial anodes 11 are arranged at an inner surface of the
boxes.
[0045] When the sacrificial anodes 11 (i.e. galvanic anodes) are
corroded, a corrosion product is formed (e.g. Al.sub.2O.sub.3, ZnO
or Mg(OH).sub.2). The corrosion products are commonly not water
soluble and may pose a potential clogging problem in the flow
channel 8. To avoid clogging due to these corrosion products, the
cooler may advantageously comprise cavities 14 in the flow channel
8. The cavities 14 are arranged such that at least some of the
corrosion products, if/when they separate from the sacrificial
anode 11, are accumulated in the cavities 14 due to gravity. A
cross-sectional view of a bend section 6 comprising a cavity 14 in
the surrounding housing element 4, or flow channel 8, is shown in
FIG. 7. A significant part of the corrosion products formed at the
sacrificial anode 11 will accumulate in the cavity 14 due to
gravity. Such a cavity 14 will also be beneficial when the
sacrificial anode 11 is arranged along a straight section 5 of the
pipe 1. Corrosion products will then be pushed or led in the
direction of the flow, and finally accumulate in the cavity 14 in a
similar manner as when the sacrificial anode 11 is outside the bend
section 6. The design of the cavity may also include an element
which reduces turbulence in the cavity. Such element may for
instance be a lip at the edge of the cavity.
[0046] In pipe-in-pipe coolers, the inner pipe 1 must be supported
to keep its position in the flow channel 8. A solution for
obtaining such support is to provide the straight sections 5 of the
pipe(s) with fins 15, see FIG. 8. The fins 15 extend in the
longitudinal direction of the pipe, and have a height (h) such that
the fins 15 are able to support the pipe 1 against an inner surface
of the outer pipe (or housing 4). A further advantage of fins is an
increased heat transfer area.
* * * * *