Note: Descriptions are shown in the official language in which they were submitted.
~2~
-1- 25-~E-0117
TUBULAR ASSEMBLY F~R TRANSFERRING FI,UIDS
This invention relates in general to tubular
assemblies for the transport of fluid therethrough and
in particular to a multiple-section conduit assembly
adapted to carry a fluid in relative isolation from
its ambient environment.
Background of the Invention
Prior art tubular assemblies for the transfer
of hot or cold fluids use inner.and outer pipes with
1~ insulation in the annular space therebetween. These
assemblies are utilized in many ways, such as for the
enhanced recovery of oil from an oil well by the
injection of steam. The conduit sections of prior art
assemblies isolate the fluid passing thrGugh their
inner pipes from the ambient environment and thus
provide a relatively effective thermal barrier
therebetween.
However, the joints between successive
conduit sections provide paths that allow a relatively
high degree of heat transfer between the inner pipe,
which is normally at the temperature of the fluid, and
the outer pipe which is near the temperature of the
ambient environment. The term "joint", as used herein
is intended to include the immediate coupling as well
as those portions of each conduit section which are
proximate thereto.
~ .i P
2--
When fluids, which are at a high temperature
and pressure relative -to the ambient environment, are
transferred through the conduit assembly, the joint
between successive conduit sections is required not
only to contain the fluid within the assembly, but must
also withstand the thermal expansion and/or contraction
of the inner pipe relative to -the outer pipe. Still
further requirements must be complied with as the
situation dictates. Thus, each joint area of a
multiple-section conduit assembly for the enhanced
recovering of oil by steam injection must (1) thermally
isolate the steam from the surrounding environment; (2)
prevent leakage and maintain the steam pressure at an
acceptable level; (3) allow for the expansion of the
inner pipes relative to each other and relative to the
cooler outer pipes; (4) support the hanging weight of
substantially all the conduit sections strung vertically
below the joint; and (5~ be rugged enough to withstand
repeated assembly and disassembly operations. Similar
problems are presented when fluids are transferred at
very low temperatures and pressures relative to the
ambient environment.
Typically, the joints of prior art assemblies
provide a poorer thermal barrier than the remainder of
the conduit section through which the fluid passes.
For example, the joints shown in United States Patent
No. 3,275,345, include fursto-conical members, one being
affixed to the corresponding ends of the pipes at each
end of a conduit section. Each pair of members supports
the inner and outer pipes in a spaced, coaxial relationship
and~ further, it transfers the expansion and contraction
forces developed by the heating and cooling of the inner
pipe relative to the outer pipe. As shown in the Patent,
successive conduit sections are joined together by bolts
passed through flanges affixed to the exterior of the
~216Ql~
outer pipe. The ~langes maintain a space or gap between
the inner pipes of the conduit sections. The frusto-
conical members form a wedge-shaped space at the joint
which communicates with the interior of the inner pipes
through the aforementioned gap. The fluid in the inner
pipe is allowed to fill this wedge-shaped space through
the gap and come into contact with the surfaces of the
frusto-conical members and the outer pipe.
Although the frusto-conical members transfer
the expansion/contraction forces developed in the inner
pipe to the outer pipe efficient7y, a relatively poor
thermal barrier exists at each joint resulting from
contact of the fluid with the outer pipes, the frusto-
conical members, and the flange of the joint. Thus,
the thermal efficiency of the entire assembly is
diminished.
Still~ other prior art assemblies include
joints in which two conforming frusto-conical surfaces
mate in the manner of a bayonet type joint. In the
latter assembly, the inner pipes of the respective conduit
sections are sealed together by a liquid seal between
the end surfaces of each inner pipe. An expansion
mechanism is provided near the inner pipe joint to
allow for the expansion/contraction of the inner pipe
relative to the outer pipe. The conical surfaces of
the mated pair of frusto-conical members in the afore-
mentioned assembly are closely fitted together and
sealed to each other. Hence~ fluid carried by the
assembly is isolated within the inner pipes and away
from the outer pipes as well as from any further joining
means attached thereto. The repeated assembly and
disassembly of the latter prior art structure is
difficult and expensive.
Objects of the- Invention
An object of this invention is to provide an
improved conduit section in a multiple-section conduit
assembly for the transport of fluid in relative isolation
~6~3~
from the ambient environment which is not subject to the
foregoing disadvantages and limitations.
A further object of this invention is to
provide a multiple-section conduit assembly having
improved joints which are easier and hence less
expensive to manufactuer than prior art devices.
An additional object of this invention is to
provide a relatively long heat transfer path at the
joints between the fluid in the interior of the inner
pipe and the ambient environment.
Another object of this invention is to provide
a multiple-section conduit assembly having joints
capable of utilizing the condensate of the fluid as a
thermal barrier when the assembly is operating in a
substantially vertical position.
Still a further object of this invention is
to provide a jointed multiple-section conduit assembly
which is able to undergo multiple assembly and disassembly
operations/ yet maintain its thermal insulative qualities.
Summary~of the Invention
One embodiment of a jointed multiple-section
conduit assembly is disclosed wherein each conduit
section includes an inner pipe, for carrying a fluid,
and an outer pipe which coaxially surrounds the inner
pipe to define an annular space therebetween The pipes
are axially displaced with respect to each oth~r such
that the first and second ends of the inner pipe lead
and lag respectively. A pair of frusto-conical structures,
each connecting corresponding pipe ends, is adapted to
support the pipes in substantially coaxial, radially
spaced relationship, as well as to provide a fluid-tight
seal for the annular space between the inner and outer
pipes.
The multiple-section conduit assen~ly includes
conduit sections successi~ely joined together in axial
alignment by appropriate joining means. The joining means
~216C~13
5 _
positions conforming Erusto-conical surfaces of the respective
structures in mutually confronted, spaced xelationship. This
mutual spacing establishes an interspace of substantially
frusto-conical shape, which communicates with the interior
of the inner pipes. In one mode of operation when the
assembly is vertically positioned and the frusto-conical
surfaces slope downwardly and outwardly from the common axis
of the assembly, the interspace serves as a trap for condensate
of the fluid flowing through the inner pipes.
In accordance with the present invention there is
provided a multiple-section conduit assembly for transporting
fluid downwardly in relative thermal isolation with respect to
the ambient environment, said conduit assembly comprising, in
combination:
at least a pair of adjacent conduit sections arranged
in vertical, end-to-end relation, each said conduit section
including
an inner pipe adapted to carry said fluid and having
first and second ends,
an outer pipe having first and second ends, said
outer pipe surrounding said inner pipe in each conduit
section in substantially coaxial relationship to define an
annular space therebetween and being axially displaced with
respect to said inner pipe such that said first and second
ends of said inner pipe lead and lag respectively the
corresponding ends of said outer pipe,
a frusto-conical structure connection each pair of
corresponding axially displaced pipe ends in each of said
conduit sections, a pair of said structures of each coaxial
30 section being adapted to support said coaxial pipes in
radially spaced relationship and to provide a fluid tight
g3
~2~ 3
- 5a -
seal of said annular space, each of said structures including
at least one substantially frusto-conical surface adapted to
confront a corresponding surface of the adjacent conduit
section, said confronting frusto-conical surfaces deflning
therebetween an interspace of substantially frusto-conical
configuration sloping downwardly and outwardly from an open
inner end defined between the ends of said inner pipes of the
adjacent conduit sections to an ou-ter end defined between the
ends of said outer pipes of the adjacent conduit sections,
whereby said interspace is in unobstructed, free f]owing
communication with the fluid-carrying interior of said inner
pipes of the adjacent conduit sections and therefore adapted
to fill with liquid in the presence of fluid in said inner
pipe to provide a thermal barrier trap between the interior
of said inner pipes and the ambient environment; and
means for joining the adjacent conduit sections and
sealing off said outer end of said interspace.
In accordance with the present invention there is
further provided a conduit section for use in a multiple-
section conduit assembly for transporting a fluid therethrough
in substantial thermal isolation from the surrounding
environment, said conduit section having ends which are
contoured such that, when joined to a similar conduit section
to form an assembly/ they form a thermal barrier trap open
to said fluid, said trap being oriented at an acute angle
with respect to the direction of fluid flow to capture fluid
condensate and to inhibit the flow of heat between the fluid
to be transported within the conduit section and the
surrounding environment.
In accordance with the present invention there is
further provided a conduit section for use in a multiple-
section conduit assembly for transporting a fluid therethrough
B
- 5b -
in substantial thermal isolation from the surrounding
environment, said conduit section having contoured ends
and means for joining successive sections such that conforming
contoured ends form a thermal barrier trap open to said fluid,
said trap being oriented at an acute angle with respect
to the direction of fluid flow to capture fluid condensate and
to inhibit the flow of heat between the fluid to be transported
within the conduit section and the surrounding environment.
In accordance with the present invention there is
further provided a multiple-section conduit assembly for
transporting a fluid in substantial thermal isolation from
the surrounding environment, said conduit assembly comprising
at least two conduit sections attached together end-to-end
at a joint, and means for forming a thermal barrier trap
open to said fluid, said trap being oriented at an acute angle
with respect to the direction of fluid flow to capture fluid
condensate at the joint and to inhibit the flow of heat
between the fluid to be transported within the conduit
assembly and the surrounding environment.
Brief Description of the Drawings
Figure 1 is a cross-sectional view of a single
conduit section in accordance with the principals of this
invention;
Figure 2 is a cross-sectional view of a jointed
conduit assembly using conduit sections as shown in Figure 1;
Figure 3 is a detailed cut-away view of the joint
between successive conduit sections; and
Figure 4 is a detailed cut-away view of another
embodiment of the joint between successive conduit sections.
B
12~013
-5c -
De-tailed Description of the Invention
Figure 1 is a cross-sectional view of an embodiment
of a conduit section constructed in accordance witn the
principles of the present invention. As outer pipe 14
coaxially surrounds an inner pipe 12, the common axis being
designated by the reference numeral 75. A substantially
annular space 16, formed between the inner and outer pipes, is
filled with insulation, as indicated by suitable cross-hatching
in the various Figures of the drawings.
Pipes 12 and 14 are axially displaced with respect to
each other, such that a first pipe end 18 of inner pipe 12
extends a predetermined distance beyond the corresponding
first pipe end 20 and outer pipe 14,
B
66~3
--6--
i.e., end 18 ]eads end 20. A second pipe end 22 of pipe
12 lags the corresponding pipe end 24 of pipe 14. Ends
20, 24 of pipe 14 have externally threaded portions 26
and 28, respectively.
A pair of frusto-conical structures 30 and 32
support the pipes in coaxial 7 radially spaced relation-
ship. Structure 30 connects end 18 of the inner pipe
to end 20 of the outer pipe. Similarly, structure 32
connects end 22 of the inner pipe with end 24 of the
outer pipe. In one embodiment of the invention, frusto-
conical structures may be integral with pipe 12, each
taking the form of a swaged pipe flange. In the latter
arrangement, flange 30 is bent outward by approximately
270, while flange 32 is bent outward about 30. Thus,
both flanges have a 30 angle of inclination relative
to the axis 75. Where structures 30 and 32 constitute
flanges integral with pipe 12, they are welded at
locations 34 and 36 to ends 20 and 24 of pipe 14
respectively, to provide fluid-tight sealing of annular
space 16. Alternatively, structures 30 and 32 may be
fabricated by swaging end portions of outer pipe 14 to
be welded to the ends of pipe 12 to provide the
aforesaid fluid-tight seal. The fabrication method
selected will largely be determined by the material
from which the pipes are fabricated.
In one embodiment of this invention, the
inner pipe is prestressed in tension and the outer
pipe is prestressed in compression. This prestressed
coniguration is illustrated by ~nited States Patent
No~ 2,924,245
In still another embodiment of the inv~ntion,
structures 30 and 32 may be manufactured as separate
and distinct members and each member may be welded to
one pair of corresponding, axially displaced pipe
ends. In the latter case~ four welds are required to
seal off annular space 16 and make is fluid-tight.
--7--
Figure 2 illustrates a cross-sectional view of
the join~ between a first conduit section 42 and a second
conduit section 44. The reference numerals used to
designate the various parts described in connection with
Figure 1 have been carried forward. However, since condui-t
sections 42 and 44 are substantially identical, the
suffixes "a" and "b" designate parts belonging to conduit
sections 42 and 44; respectively, whenever clarity in
the following discussion demands that a distinction be
maintained.
In order to join two or more conduit sections
into a conduit assembly/ an internally threaded coupling
40 or sleeve is adapted to engage external threads 26
and 28 on the outer surface of pipe 14 and to form a
substantially fluid tight seal therewith. Further,
coupling 40 holds conduit section 42 in axial alignment
with conduit section 44. Structures 30 and 32 have
first and second conforming frusto-conical surfaces 52
and 54 of conduit sections 42 and 44 respectively. When
assembled,surfaces 52 and 54 are held in mutually
confronting, spaced relationship such tha-t the contoured
ends are fit together. The spacing established by
coupling 40 between the two frusto-conical surfaces is
small compared to the inside diameter of the inner
pipes 12a and 12b. Further, this spacing defines a
frusto-conical interspace which is designated by the
reference numeral 60 in Figures 2 and 3, Figure 3
illustrating in greater detail the joint between
conduit sections 42 and 44.
Edge surfaces 56 and 58 of pipe ends 24 and
20 respectively are similarly spaced. Thus, coupling
40 is effective to establish peripheral gap 53 between
the latter surfaces. This, gap, together with interspace
60l constitutes a volume of space which communicates
with the interior 76 of axially aligned inner pipes
12a and 12b.
~6~1~3
--8--
Figure 4 is a detailed cut-away view of an
alternative embodiment of the jo:int between successive
conduit sections. Applicable reference numerals have
been carried forward from Figure 3 since the parts are
substantially identical. In this embodiment, edge
surfaces 56 and 58 of pipe ends 24 and 20 respectively,
abut each other.
Each joint of the conduit assembly described
hereinabove can be easily assembled and disassembled
13 because the coupling is removably threaded onto the
exterior surfaces of the outer pipes. Since the
spacing between mutually confron-ting frusto-conical
surfaces 5~ and 54 may be such that these surfaces
converge in a downward direction, as shown in Figure 4,
edge surfaces 56 and 58 of outer pipes 14a and 14b of
the successive conduit sections may actually abut each
other.
In operation, the multiple-section conduit
assembly is preferably positioned with its common axis 75
substantially vertical. As illustrated in Figure 3,
frusto-conical interspace 60 slopes in a downward
direction and away from the common axis. Fluid ~low,
which may be liquid or gas flow, is assumed to be from
top to bottom. In the position shown, gap 53 and
interspace 60 is at an acute angle with respect to the
direction of the fluid flow and serve as a trap to
catch or capture a condensate of such gaseous fluid
as it flows in an axial direction from top to bottom
through the inner pipes. The pressure of the fluid
and/or the force of gravity serves to guide the
condensate into the interspace such that it remains
trapped there.
For purp~ses of illustration, let it be
assumed that the fluid constitutes live steam which
flows in a downward direction from conduit section 42
to conduit section 44 ln the assembly illustrated by
~.21~13
- 9 -
Figures 3 and 4. In normal operation, condensate will
form on the coolest parts of the assembly. Hence in
the assembly shown in Figure 3, -the condensate will
begin to form on the inner coupling surface 57 since
the outside of coupling 40 is in contact with the
cooler ambient environment. The residue of the steam
continues to condense. Gravity traps the condensate
in peripheral gap 53. As condensate continues to form
and accumulate~ the liquid rises and ultimately
reaches level 61 in interspace 60, as shown in Fiyure 3.
Any further accumulation drains into interior 76 and
is carried away with the axially directed fluid flow.
Thus, gap 53 and interspace 60 together form a thermal
barrier trap in which the condensate resides.
The joint between successive conduit sections
must also provide the multiple-section conduit assembly
with relief ~rom thermal stress, in addition to
providing an acceptable degree of thermal insulation.
Specifically by transferring the expansion/contraction
forces generated by the inner pipe to the outer pipes
of each conduit section through the agency of
structures 30 and 32, the outer pipe serves to partially
relieve the thermal stress and strain forces developed
in the inner pipe. Further, when the condensate is at
level 61, the steam flowing through interior 76 is
thermally isolated from the ambient environment by
coupling 40 and by a relatively long path through the
interspace. The latter is filled with condensate
whose temperature will vary from the temperature of
the steam at interior 76 to near the temperature at
coupling 40 thereby creating a thermal barrier. Further
in each conduit section thermal insulation is provided
by the sealed annular space 16 between the inner and
outer pipes/ which space preferably contains a thermal
insulative material.
~2 ~ 9~
--10--
To minimize heat loss through the joint in a
preferred em~odiment of the invention, frusto-conical
surfaces 52 and 54 are both at a 30 angle of
inclination relative to common axis 75. In such an
arrangement, -the insulation, which is contained in
annular spaces 16a and 16b immediately adjacent to the
joint, presents an effective thermal barrier against
any appreciable transfer of heat therethrough. Further~
at this particular angle of inclination, structures 30
and 32 are of sufficient length to limit an appreciable
transfer of heat through the structures. Together with
the accumulated condensate liquid trapped in gap 53
and interspace 60, an efficient thermal barrier is
presented by the joint, between the ambient environment
surrounding coupling 40 and the live steam in interior
76. Since the spacing between surfaces 52 and 54 is
relatively small compared to the inside diameter of the
inner pipes~ fluid flow through the interior of the
inner pipes will have not created any appreciable
currents in the condensate which would affect the
thermal gradient therein and the insulation of the joint.
At inclination angles greater than 30, the
physical length of structures 30 and 32, as well as the
length of interspace 60, are decreased and the ~oint
becomes thermally less efficient. However~ such an
arrangement may nevertheless be desirable because
thicker structures 30 and 32 and greater angles may
enhance the ability of the structures to transfer the
expansion/contraction forces. As stated above, these
forces result from the flow of fluids at relatively
high temperatures and pressures in the inner pipe
relative to the outer pipe. Angles of inclination less
than 30 are not as thermally efficient, because less
insulative material is disposed proximate the joint in
annular space 16. This smaller amount of insulative
material and the smaller physical distance between
inner pipe end 18 and structure 30 through annular
space 16b, allows an appreciable amount of heat to
3LZ~
flow therethrough. However, a smaller angle of
inclination may be desirable due to the transportation
of the aforementioned forces acting on the inner and
the outer pipes.
The multiple-section conduit assembly
disclosed herein performs optimally when its common
axis 75 is positioned substantially vertical and the
frusto-conicalsurfaces slope downward toward gap 53
and outward from axis 75, as shown in Figure 3.
However, thc invention is not so limited and the
assembly can also operate in different positions, e.g.,
horizontally. In all such instancesl the direction of
the fluid flow must be such that gap 53 is positioned
downstream with respect to the point where interspace
60 communicates with pipe interior 76. Since gravity
is only partially, or not at all, relied upon in such
an arrangement~ the pressure in pipe 12 must be such
that the fluid condensate is forced into the gap and
interspace and remains trapped there.
The conduit assembly described herein may be
modified in structure without departing from the
principles of the present invention. For example, the
conduit assembly may be used to transport fluids which
are colder than the ambient environment. It is also
possible to substitute other suitable joining means for
coupling 40~i.e., flanges attached to the outer pipes
with bolts therethrough. Further, the coupling may be
welded to the outer pipes in lieu of the use of
threads. Both welding and threading may be used to
joint the conduit sections together.
From the foregoing discussion it will be
clear that the present invention is not limited to the
apparatus specifically disclosed herein, but that
numerous modifications, partial ~nd complete
substitutions, e~uivalents and changes will now occur
to those skilled in the art, all of which fall within
the scope of the invention. Accordingly, it is
6~
-12-
intended that the invention disclosed herein be limited
only by the spirit and scope of the appended claims.
