Pipe supporting system
The invention relates to a holding system for holding at least one pipe
and, in particular, a pipe subjected to forces tending to cause its
5 displacement with respect to the structure to which it is attached. Such
forces may be caused in particular by acceleration of this structure, and/or
by thermal expansions or contractions which the pipe and/or the structure
undergo (undergoes) and by turbulence in gas flow.
In this document, the present invention will be described essentially
10 by referring to one (single) pipe; it must be well understood, however, that
the invention is also applicable in a holding system serving to hold several
pipes distinct from one another.
One important application of the invention relates to a heat exchanger
for rocket engine. This exchanger consists principally of a pipe called a coil,
15 coiled so as to form helical turns, attached inside a cylindrical tube (of
circular section), the diameter whereof is only slightly larger than that of the
turns of the coil.
This heat exchanger, called a heater, is used to heat the hydrogen
used as a fuel by the rocket engine by drawing heat from the exhaust gases
20 of the rocket engine. Thus, the liquid hydrogen is injected into the coil at a
temperature of approximately 40K; it leaves the coil at a temperature of
approximately 400K. The hydrogen is heated by the exhaust gases
circulating in the cylindrical tube, which have a temperature near 700K.
It is understood that the coil tends to undergo considerably
25 differential thermal expansions due to the very high differences in
temperature to which it is subjected. These' differences in temperature
tend to cause deformations of the coil, allowed in particular by the small
thickness thereof (only 1 mm, for a coil diameter near 250 mm).
The system for holding the coil must be capable of limiting to
30 acceptable values the displacements of the coil due to these thermal
expansions and contractions.
On the other hand, being carried on board a rocket, the coil is
subjected to very strong vibrations and accelerations, as well as to the
turbulence of the gases. It must therefore also be held in the radial and
35 axial directions so as to resist these stresses.
Conversely, mechanical holding of the coil, which is indispensable
for the foregoing reasons, must be provided while still maintaining a level
of mechanical stresses as low as possible in the coil. In fact, such
2
stresses are likely to cause deteriorations in the coil, and in particular a
deterioration of the welds formed at the ends of the coil by its connection
to the upstream and downstream portions of the hydrogen distribution
circuit of the rocket engine, and thus to cause hydrogen leaks in the
5 engine. Such leaks are naturally unacceptable.
The objective of a first aspect of the invention is therefore to propose
a holding system for holding at least one pipe, capable of holding this or
these pipe(s) despite the stresses to which it is subjected or to which they
are subjected, whether these stresses are related to thermal expansions or
10 contractions, and/or due to vibrations or to accelerations undergone by the
pipe(s), and/or by a structure to which the pipe(s) are attached, while
maintaining a minimal level of mechanical stresses in the pipe(s), and at a
moderate cost.
This goal is attained thanks to the fact that the holding system
15 comprises a comb including a bar and a plurality of parallel teeth
perpendicular to the bar, and a blocking device capable of preventing a pipe
passing between two of said teeth to move away from the bar.
In the foregoing sentence, the pipe is assumed to have a cylindrical
shape; thus, so that the blocking device is able to prevent a pipe passing
20 between two teeth from moving away from the bar, it is enough that the
passage formed between the two considered teeth be at least partially
obstructed by said blocking device (placed in/and or facing said passage),
the blocking device being moreover held at a fixed distance from the bar.
The comb may have in particular, between the two considered teeth, a free
25 passage which includes the volume of a pipe segment, with an axis generally
perpendicular to the bar and to the teeth, and the blocking device includes a
wall or an obstacle positioned in such a manner that this wall or this obstacle
is necessarily encountered or struck by this pipe segment during a
displacement of this segment between the considered comb teeth in the
30 direction moving the segment away from the comb to remove it from the
comb.
Advantageously, thanks to the invention, when one or more pipes are
positioned in parallel so as to pass between the teeth of the comb, the
blocking device holds this or these pipe(s) in position and consequently
35 allows the holding system to definitely provide for the holding of this or these
pipe(s).
Holding of one or more pipes by the blocking device is preferably
accomplished in a relatively loose manner, to avoid applying useless stresses
3
to the pipe(s). The holding system may in particular allow displacement of
the pipes along the axial direction of the free passages between the teeth of
the comb, i.e. in the axial direction of the pipe(s).
The pipe generally has the shape of a coil which is intended to be held
5 in a tube. In this case, the relatively loose holding of the different turns of
the coil in the tube by the blocking device allows expansion of the turns of
the coil and consequently, possible rotation of one or more turns of the coil
with respect to the tube.
In the holding system, the following arrangements are preferably
10 adopted, alone or in combination:
- The blocking device may be supported on at least two teeth of the
bar, and in particular on two end teeth located at the ends of the bar.
- The blocking device may be supported on at least one intermediate
tooth remote from the ends of the bar.
15 -The blocking device may consist essentially of a pin. A pin designates
here a part with an elongated shape, particularly a rod. The rod may possibly
be hollow, and/or split.
- at least one tooth of the comb may have a hole, and the pin may be
configured to (and capable of) pass into it.
20 - this pin may comprise a shell of a generally cylindrical shape split
along an axis of the shell. This shape allows, in fact, radial elastic
deformation of the pin.
- The blocking device may have at least one pipe support notch,
particularly in a substantially cylindrical or toroidal shape.
25 - The pipe support notch may allow support of the same over an area
along an axis of the pipe (or of the passage provided for the pipe) at least
equal to a maximum diameter of passage in the pipe.
- At least one passage in the comb between two adjacent teeth may
have an inclination with respect to an axis of the bar.
30 - At least one passage in the comb between two adjacent teeth may
have a cylindrical or toroidal shape.
- The system may further comprise two supports positioned at the
ends of the comb. These supports may be configured to hold the comb so as
to allow a rotation thereof around an axis of the bar.
35 - these supports may possibly hold or contribute to holding the
blocking device. The blocking device may thus be supported on at least one
support, or possibly on both supports.
4
Each of the supports may be configured to be attached to a wall, for
example the wall of a tube, to which the pipe(s) is/are to be attached.
The invention also allows obtaining an assembly including a
plurality of holding systems attached to an interior wall of a cylindrical
5 tube, positioned axisymmetrically about an axis of said tube. Such an
assembly is adapted to maintain a pipe helically coiled in the tube, called
a coil. Preferably, the holding systems are placed axially (along the axis
of the tube) in regularly staggered positions, so as to support the turns
of the coil while deforming it minimally.
10 The invention also relates to a heat exchanger including at least
15
one holding system and/or an assembly as defined previously.
The invention relates, finally, more generally to a rocket engine, or
also to an industrial production unit, including at least one system and/or
an assembly and/or a heat exchanger as defined previously.
A second aspect of the invention relates to a method for mounting
a heat exchanges consisting primarily of a coil including a plurality of
turns, arranged inside a tube. In conformity with this second aspect of
the invention, the heat exchanger is mounted thanks to the following
20 operations:
a) there are provided:
the tube, the coil and a pin;
a comb including a bar and a plurality of parallel teeth, perpendicular
to the bar; and
25 two supports, capable of being positioned at the ends of the comb and
to hold the comb so as to allow a rotation thereof around an axis of the bar;
b) a first of the two supports is positioned and attached to the inner wall of
the tube;
c) the comb is positioned in the tube by holding the comb in such a manner
30 that it is folded against said wall;
d) the coil is put in place (i.e., inside the tube and generally positioned
coaxially with respect to the tube);
e) after steps b) and c), the comb is pivoted so that its teeth are radially
oriented in the tube and axially block turns of the coil (at least one turn,
35 possibly all the turns);
g) the second of the supports is positioned and is attached to the inner wall of
the tube; and
5
h) the pin is attached to the comb and/or to the supports so as to constitute a
blocking device (30) preventing all the turns or a portion of the turns passing
between said teeth to move away from the bar.
In the method defined above, steps c) and d) may be carried out in
5 any order (step c) before step d) or step d) before step c)).
In fact, as long as the comb is positioned in a position folded against
the wall (meaning that the axis of the teeth is locally substantially parallel to
the wall), the comb and the coil may be placed or displaced in the tube
independently of one another.
10 In one embodiment, the pin provided in step a) is chosen to be
capable of passing through at least one hole in a tooth of the comb.
In this case, the method may in particular comprise a step f) prior to
step g), during which the pin is put in place by having it pass into said at
least one hole in a tooth of the comb.
15 In one embodiment, steps g) and h) are accomplished simultaneously or
substantially simultaneously by positioning the second support on the inner
wall of the tube and by attaching the pin to this at least so as to block the pin
and thus constitute the blocking device.
In one alternative embodiment, the method is implemented by using
20 an elastic pin (at least in its longitudinal direction).
Step h) is then accomplished after step g) in the following manner:
the pin is compressed in its longitudinal direction;
it is placed or put in position between the supports; then
it is released or slackened in such a manner that it is blocked between
25 the supports.
In step g), after having attached the second support, or after having
slackened the pin in the above case, all the degrees of freedom of the pin
are generally blocked, with the exception of rotation of the pin around its
longitudinal axis, which may remain possible.
30 After this blocking of the pin, those of the turns of the coil which are
positioned between the teeth of the comb are blocked by the pin and
prevented from moving away from the bar of the comb. As was indicated
earlier, these spires generally retain, however, the possibility of moving with
respect to the wall of the tube (and the comb) in their circumferential
35 direction.
The invention will be well understood and its advantages will appear
more clearly upon reading the detailed description that follows, of
6
embodiments shown by way of non-limiting examples. The description refers
to the appended drawings, on which:
- Figure 1 is a schematic view in perspective of a heater for a rocket
engine, comprising three holding systems according to the invention;
5 - Figure 2 is a schematic view in perspective of one of the holding
systems shown in Figure 1;
- Figure 3 is a partial schematic section, perpendicular to a holding
system, of the heater of Figure 1; and
- Figure 4 is a schematic view in perspective of a mounting step of the
10 heater shown in Figure 1.
As may be seen in Figure 1, a heater 100 comprises a coil 50, a
cylindrical tube 60 and three identical holding systems 101, 102, 103 used to
attach the coil 50 in the tube 60.
The coil includes four substantially identical turns 51, 52, 53 and 54
15 (Fig. 3) offset two by two at a constant pitch P along the axis A of the tube
60. The ends of the coil pass through the wall of the tube 60 and are
attached by means of connectors 55A, 55B, to upstream and downstream
portions (not shown) of the hydrogen distribution circuit.
The heater 100 is part of a rocket engine 1000 of which only the
20 heater is shown.
Alternatively, it is possible to consider that reference symbol 1000
designates an industrial unit, of which the heater 100 would be a part.
Hydrogen is injected at a temperature of approximately 40K into the
coil, through the connector 55A, and leaves via the connector 55b of the coil
25 at a temperature of approximately 400K.
The holding systems 101, 102 and 103 are identical; thus, only the
system 101 will now be described, with reference to Figure 2.
The system 101 includes a comb 20 and a blocking device 30
consisting essentially of a pin 32.
30 The comb 20 includes a bar 22 and five parallel teeth 24A, 24B, 24C,
24D and 24E, perpendicular to the bar. The teeth 24A to 24E are designated
collectively with the reference symbol 24.
Between the teeth, passages 26A, 26B, 26C and 26D are arranged,
designated collectively as the passages 26.
35 When the coil 50 is in the holding position by the holding system 101,
the different turns 51 to 54 pass respectively in the different passages 26A to
26D, each turn passing between two adjacent teeth.
7
Each of the turns 51-54 is prevented by the pin 32 from moving away
from the bar 22 and shifting itself radially toward the interior/ i.e.
approaching the axis A. Each of the turns is moreover axially held by the
walls of the passage through which it passes/ which are surfaces of the
5 different teeth 26A to 26E.
The passages 26 have a cylindrical shape/ i.e. the shape of a portion
of a cylinder (this form would possibly be toroidal)/ and more precisely the
shape of a cylinder the radius whereof is equal to the radius R of the
transverse section of the turns or very slightly greater (Fig. 3). Thus each
10 turn may have distributed1 rather than point-wise support/ in the bottom of
the passage 26 in which it is placed. The passage 26 provides for axial
holding of the turn1 and further limits radial movements of the turn in the
direction tending to move it away from or toward the axis A.
Moreover/ the axes of the cylindrical surfaces of the different passages
15 26 are not perpendicular to the axis A. These axes (called "axes of the
passagesu) are in fact slightly inclined with respect to the axis of the bar 221
the inclination angle (angle a) being equal to that formed by the turns of the
coil with respect to the axis A of the tube 60. It follows that when the combs
20 are mounted inside the tube 601 the axes of their bars 22 then being
20 parallel to the axis A1 the axes of the passages 26 are locally parallel to the
axes of the turns of the coil1 at the point where these turns are supported in
the different passages 26.
Holding and attachment of the blocking device 30 (the pin 32) with
respect to the comb 20 are provided by the teeth of the comb 20.
25 To this end1 the teeth located at the ends of the bar 22 or end teeth
(24A and 24E)1 as well as the median tooth 24C1 are more elongated than
the intermediate teeth 24B and 24D. In fact1 the teeth 24A1 24C and 24E are
elongated and each include a flattened end/ in which is formed a through
hole (one hole for each of these teeth)1 the three holes thus formed being
30 aligned with an axis parallel with the axis of the bar 22 of the comb 20.
The diameter of these holes is selected so as to allow the passage and
free rotation of the pin 32 in these holes. In passing through the three holes
thus formed/ the pin 32 is supported on the three teeth 24A1 24C and 24E1
which blocks its displacements in the plane perpendicular to the axis of the
35 bar 221 and thus allows it to carry out its function of preventing all
movement of the turns tending to move them away from the bar 22.
The pin 32 has the general shape of a straight bar. However/ the pin
is in fact hollow/ and consists of a shell with a generally tubular overall
8
shape. This envelope is split along an axis of the shell over the entire length
of the pin, this in such a manner that when the pin is unstressed, the edges
of the slot are slightly separated from one another. This shape allows the pin
to compress elastically (and not plastically) when the turns press on the pin,
5 as will be clarified later.
The pin further has four turn support notches 32A, 328, 32C and 32D
(Fig. 3). These notches are shaped substantially as portions of cylinders;
they allow, when one of the turns is supported by the pin, providing an
extended rather than point-wise support surface to the turn, which means
10 that the stress level in the turn remains moderate and the appearance of a
local stress peak is avoided.
The support surface extends, in the axis of the pipe, over an extent
along the axis of the pipe at least equal to the diameter of the pipe.
The notches are spaced two by two by a pitch P, and placed on the
15 same side of the pin 32.
The holding system 101 further includes two supports 40A and 408,
positioned at the ends of the comb 22. These supports are used to prevent
any translation and any rotation of the comb 20, with the exception of its
rotation around the axis of the bar 22, which remains allowed particularly to
20 allow mounting of the system, as will now be described.
The supports 40A and 408 are also used to hold the pin 32 in the axial
direction of the heater 100. To this end, the supports 40A and 408 are
arranged with a wall perpendicular to the axis of the pin 32, which blocks it
in translation and forces it to remain axially (with respect to the axis A of the
25 bar) in the position in which the notches are axially at the same level as the
turns 51 to 54 and as the different passages 26.
To mount the heater 100, the operations to be carried out are the
following:
a) the cylindrical tube 60, the coil 50, and the necessary components for
30 producing three holding systems are provided, to wit: three combs 20, three
pins 32 and three pairs of supports 40A, 408.
b) the three supports 40a are then positioned and attached to the inner wall
of the tube (each support 40A is a lower support for the holding system of
which it is a part).
35 d) the coil 50 is put in place.
c) the combs 20 are positioned while holding them in such a manner that
they are folded against the wall. To this end, the combs are slid between the
wall of the tube and the turns of the coil.
9
e) the combs 20 are pivoted so that their teeth are oriented radially in the
tube 60 and axially block the turns 51-54 of the coil 50.
f) for each holding system, a pin 32 is placed by having it pass into the holes
in the teeth 24A, 24C and 24E of the comb 20 (the pins 32 are compressed
5 without plastic deformation);
g) the supports 40B are positioned (each support 40B is a second support or
upper support for the holding system of which it is a part) and they are
attached to the wall of the tube 60 so as to finish the blocking of the pins 32
and consequently of the turns of the coil 50.
10 More specifically, the mounting operations to be carried out are the
following:
b) the three supports 40A are positioned and attached to the wall of the tube
60• I
d) the coil 50 is put in place,
15 c) the combs 20 are then positioned, holding them in such a manner that
they are folded against the wall;
e) the combs 20 are then pivoted so that their teeth are radially oriented in
the tube 60 and axially block the turns 51-54 of the coil 50;
f) the elastic pins 32 are placed, which are compressed without having them
20 undergo plastic deformation, by having them pass into the holes in the teeth
24A, 24C and 24E (while making sure not to damage the coil 50);
g) the supports 40B are positioned and they are attached to the wall of the
tube 60, which finishes blocking the pins 32 and consequently, the turns of
the coil 50.
25 It will be noted that during step c), the combs 20 are positioned on
the supports 40A in such a manner that the axes of the bars 22 are directed
along the axis A, and the teeth of the comb are directed in a non-radial
direction in the tube 60, which corresponds to the "folded" position of the
comb 20. In this folded position of the comb 20, the teeth of the comb are
30 preferably oriented in a circumferential, or at least substantially
circumferential direction. In this position, the combs 20 are sufficiently thin
to be able to pass around the turns 51-54, between the tube and the coil.
Once the combs 20 are placed on the supports 40A, and are therefore axially
(with respect to the axis A) in the desired position, in step e) they are
35 pivoted around the axis of the bars 22, which brings the combs into the
position shown in Figure 1, with the teeth radially oriented in the tube 60.
10
Once operations a) and g) are carried out, the coil 50 is connected to
the hydrogen distribution circuit through the wall of the tube 60 using the
connectors 55A and 55B (Fig. 1).
Moreover, it will also be noted that the three holding systems 101,
5 102 and 103 are not axially positioned at the same level in the tube 60. They
are in fact axially shifted two by two, so that the position of the holding
system axially corresponds to the position of the turns that it must hold.
Thus, with three holding systems angularly spaced by 120°, it is suitable to
shift the systems two by two by a pitch equal to one third of the pitch P of
10 the turns of the coil 50. This arrangement is illustrated in Figure 3, in which
is shown a circle C with axis A passing through the top of the system 101.
Due to the inclination of the turns of the coil, the system 102 is shifted
axially by a distance D1 equal to P/3, and the system 103 by a distance D2
equal to 2P/3.
15
During operation of the rocket engine 1000, the heater behaves in the
following manner:
The hydrogen injected into the coil 50 via the connector 55A is at a
temperature of approximately 40K. This hydrogen is heated by passing
20 through the coil and as a result, tends to cool the wall of the coil.
It follows that the turn 51 contracts very slightly (not insignificantly,
however) and that the turn 52 tends to contract rather quite considerably.
Due to .this contraction, the turn 52 presses on the pin 32, in the notch 328.
As the pin 32 is split, it locally deforms, elastically, to allow a slight radial
25 displacement of the turn 52 toward the axis A.
The turns 53 and 54, on the other hand, have a tendency to dilate
and increase in diameter (measured with respect to the axis A) because the
temperature of the hydrogen contained in these turns is considerably greater
than that of the hydrogen contained in the turns 51 and 52.
30 The pin 32 and the comb 20 are arranged in such a manner that,
when the engine 1000 operates, all the turns preferably press on the pin 32,
causing radial deformations thereof of a greater or lesser degree (Fig. 3).
These radial deformations are elastic deformations. This allows that,
no matter the variations in temperature in the heater 100, the pins maintain
35 an elastic support on the turns of the coil 50, thus avoiding the appearance
of clearances, which are potential vibration generators.
As shown in Figure 3, at the time the heater 100 is started up, the
turns undergo slight radial deformations, which are contained by the holding
11
systems 101, 102 and 103. These radial deformations may be accompanied
by slight displacements of the turns along the circumferential direction of the
tube 60, As the combs 20 are free to rotate around the axis of the bars 22,
and the pins 32 are also free to rotate around their own axis, these
5 displacements along the circumferential direction of the turns 51-54 may be
to some degree accompanied by a rotation of the combs 20 and/or the pins
32 in question, which also contributes to limiting the stress level attained in
the turns.
In addition, the slight inclination of the passages 26 (angle a), their
10 cylindrical shape which takes on the shape of the turns 51, the notches
arranged in the pins, allow the turns 51 to 54 to have distributed, and not
point-wise, supports, on the holding systems 101 and 103.
These different features make it possible for the holding systems 101,
102, 103 to hold the coil 50 in position while limiting the level of mechanical
15 stresses therein to a minimum level.
The embodiment presented comprises three holding systems and four
turns. The invention is naturally applicable to any number of holding systems
and turns of the coil. The holding systems are also usable in rectilinear tubes
or others.
20 Moreover, a holding system conforming to the invention may be used
in the space industry. It may also relate more broadly to all industries in
which coil exchangers are used subjected to strong thermal stresses.

CLAIMS
1. A method for mounting a heat exchanger (100) consisting primarily of a
coil (50) including a plurality of turns (51-54), arranged inside a tube (60),
5 the method including the following steps:
a) there are provided:
the tube (60), the coil (50) and a pin;
a comb (20) including a bar (22) and a plurality of parallel teeth (24),
perpendicular to the bar;
10 two supports (40A, 408), capable of being positioned at the ends of
the comb and to hold the comb so as to allow a rotation thereof around an
axis of the bar;
b) a first ( 40A) of said two supports is positioned and attached to an inner
wall of the tube (60);
15 c) the comb (20) is positioned in the tube by holding the comb (20) in such a
manner that it is folded against said wall;
d) the coil (50) is put in place;
e) after steps b) and c), the comb (20) is pivoted so that its teeth (24) are
radially oriented in the tube (60) and axially block turns of the coil (50);
20 g) the second ( 408) of said supports is positioned and is attached to the inner
wall of the tube (60);
25
30
h) the pin is attached to the comb and/or to the supports so as to constitute
a blocking device (30) preventing all the turns or a portion of the turns
passing between said teeth to move away from the bar.
2. The mounting method according to claim 1, characterized in that steps g)
and h) are accomplished simultaneously by positioning the second support
( 408) on the inner wall of the tube and by attaching the pin to this at least so
as to block the pin and thus constitute the blocking device.
3. The mounting method according to claim 2, wherein the pin (32) is
capable of passing through at least one hole in a tooth of the comb (20); and
the method further includes a step f), prior to step g), and during which the
pin is put in place by having it pass into said at least one hole in a tooth of the
35 comb.
13
4. A holding system (101, 102, 103) for holding at least one pipe,
comprising
a comb (20) including a bar (22) and a plurality of parallel teeth (24),
perpendicular to the bar, and
5 a blocking device (30) capable of preventing a pipe passing between two of
said teeth to move away from the bar,
the blocking system consisting essentially of a pin (32);
the system being characterized in that it further comprises two supports
( 40A, 408) positioned at the ends of the comb, and holding the comb in such
10 a manner as to allow rotation thereof around an axis of the bar.
5. The system according to claim 4, wherein the blocking device is
supported on at least two teeth (24A, 24C, 24E) of the bar.
15 6. The system according to claim 4 or 5, wherein the pin (32) comprises a
shell of a generally cylindrical shape split along an axis of the shell.
20
7. The system according to any one of claims 4 to 6, wherein the blocking
device has at least one pipe support notch (32A-32D).
8. The system according to any one of claims 4 to 7, wherein at least one
tooth of the comb has a hole, and the pin is configured to pass into it.
9. The system according to any one of claims 4 to 8, wherein at least one
25 passage (26) in the comb between two adjacent teeth has an inclination with
respect to an axis of the bar.
10. The system according to any one of claims 4 to 9, wherein at least one
passage (26) in the comb between two adjacent teeth has a cylindrical or
30 toroidal shape.
11. An assembly comprising a plurality of holding systems (101, 102, 103)
attached to an inner wall of a cylindrical tube (60), axisymmetrically
positioned around an axis (A) of said tube, each of said holding systems
35 being a system according to any one of claims 4 to 10.
14
12. A heat exchanger (100), including at least one system according to any
one of claims 4 to 10, and/or an assembly according to claim 11.
13. An industrial production unit (1000) including at least one system
5 according to any one of claims 4 to 10, and/or an assembly according to
claim 11, and/or a heat exchanger according to claim 12.
14. A rocket engine (1000), including at least one system according to any
one of claims 4 to 10, and/or an assembly according to claim 11, and/or a
10 heat exchanger according to claim 12.