Device for connecting vacuum-insulated double-walled tubes

Abstract

The invention relates to a device for connecting first and second vacuum-insulated double-walled tubes (1a, 1b, 1c, 1d; 2a, 2b, 2c, 2d), the ends of which are in the form of flanges (14a, 14b) and lie opposite each other, said tubes having a flow cross-section (6) in which a gaseous or liquid cryogenic medium flows. Each of the end regions (30, 31) of the first and second vacuum-insulated double-walled tubes (1a, 1b, 1c, 1d; 2a, 2b, 2c, 2d) is surrounded by another, third, vacuum-insulated double-walled tube (3, 3a, 3b). The third double-walled tube can be axially pushed onto the first and second vacuum-insulated double-walled tubes (1a, 1b, 1c, 1d; 2a, 2b, 2c, 2d) such that the flanges (14a, 14b) lying opposite each other are freely accessible. The invention additionally relates to the use of the device in order to connect vacuum-insulated double-walled tubes (1a, 1b, 1c, 1d; 2a, 2b, 2c, 2d) in a duct system in which cryogenic gaseous or liquid media flow, in particular in aircraft.

Description

[0001] Device for connecting double-walled vacuum-insulated pipes

[0002] Technical area

[0003] The invention relates to a device for connecting vacuum-insulated first and second double-walled pipes, the pipe ends of which are arranged opposite one another as flanges and through whose flow cross-section a gaseous or liquid cryogenic, cryogenic medium flows. Furthermore, the invention relates to the use of the device in an aircraft for conveying liquid or gaseous cryogenic media, in particular hydrogen.

[0004] State of the art

[0005] The most well-known coupling for cryogenic liquids and gases is the so-called Johnston coupling, also known as a bayonet coupling. This is a plug-in connection in which a vacuum-insulated inner tube is pushed into a vacuum-insulated outer tube. The overlapping area of ​​the two nested tubes extends the path that heat must travel to reach the cryogenic medium from the outside, thus contributing to the insulation. Since the vacuum space in these double-walled tubes must usually be surrounded by a metallic wall that is closed on all sides to permanently maintain the vacuum, the tubes in the overlapping area are also metallic and therefore conduct heat along their surface in an axial direction, but not in a radial direction, through the vacuum space.Since the inner pipe must be metallically connected to the outer pipe at the ends of the respective pipes in order to seal off the vacuum space, heat conduction in a radial direction also occurs here. The two ends of the pipes connected via the bayonet coupling must therefore be separated from each other by an overlap as long as possible in order to avoid direct heat flow through the end connections. The longer the overlap area, the better the insulation effect. However, this overlap area means that a significant axial insertion movement is necessary to close or open the bayonet coupling. In a piping system, this can mean that in order to assemble or replace a pipe segment at a certain point, many pipes attached upstream or downstream would have to be moved with it, or can only be assembled or disassembled sequentially.Particularly in complex piping systems, such as those found in aircraft, this can lead to far-reaching restrictions in assembly capabilities. In the event of maintenance, replacing a single pipe segment would require the disassembly and subsequent reassembly of entire pipelines. In addition to the Johnston coupling, there are numerous modified forms of cryogenic couplings, all of which, however, require the necessary axial insertion movement in almost all cases. Solutions that require no or only very slight insertion movement generally feature fairly direct, poorly insulated connections between the inner and outer pipes and are therefore usually only used in cryogenic applications with lower requirements, such as liquefied natural gas (LNG), whose temperature does not fall below the condensation temperature of atmospheric oxygen.However, these couplings are generally unsuitable for colder gases, such as liquid hydrogen, where atmospheric oxygen could condense at strong thermal bridges. Liquid oxygen is highly flammable, can cause fires, and therefore poses a high safety risk.

[0006] Previous connecting elements with thermal decoupling for use in conveying cryogenic media, such as liquid hydrogen, require a large installation dimension in the direction of the pipe axis. This is necessary because the heat transfer between the cryogenic inner pipe and the warm outer pipe must be minimized as much as possible over a long distance. Previous solutions create a maximally extended path in the space between the inner and outer pipes, which are usually each highly vacuum insulated, which prolongs the heat transfer via the material. This solution requires that the two coupling elements be pushed axially into one another over a length that is many times the pipe diameter. Typical lengths for this are between 300 mm and 600 mm for diameters in the range of approximately 25 mm.Solutions that better address the problem of axial mounting dimensions usually do not have a sufficiently dimensioned heat transfer for satisfactory thermal decoupling.

[0007] US 2023 / 0139421 A1 relates to a connecting arrangement for two sections of a conveying pipe for a cryogenic fluid, including an additional thermal insulation chamber and a fluid expansion chamber. The disclosed arrangement comprises one end that can be at least partially inserted into a complementarily shaped end, creating a sealed mechanical connection extending over several centimeters. Furthermore, a thermal insulation chamber is provided for two pipe sections and another thermal insulation chamber that thermally insulates the connecting zone of the two interconnected sections. Finally, an expansion chamber for the cryogenic fluid is provided, which is designed to be equipped with a detection-sensitive sensor for cryogenic fluids, which is located in the connecting zone between the two tubular sections.This allows two pipe sections carrying a cryogenic fluid to be represented.

[0008] Disclosure of the invention

[0009] A device is proposed for connecting vacuum-insulated first and second double-walled pipes, the pipe ends of which are arranged opposite one another as flanges, and in whose flow cross-section a gaseous or liquid cryogenic, deep-cold medium flows. The first and second vacuum-insulated double-walled pipes are each enclosed in their end regions by a further, third vacuum-insulated double-walled pipe, which is axially displaceable on the first and second vacuum-insulated double-walled pipes such that opposing flanges become accessible. The solution proposed according to the invention advantageously makes it possible to achieve a butt connection between pipe ends that does not require any axial disassembly or assembly path, since after an axial movement of the vacuum-insulated double-walled pipe into one of the end regions, a radial movement of the adjacent first and second vacuum-insulated double-walled pipes is possible.Advantageously, the solution proposed by the invention is designed such that the third vacuum-insulated double-wall pipe covers a joint between the first and second flanges. Therefore, only a slight axial displacement of the third vacuum-insulated double-wall pipe is required to expose this joint.

[0010] The device proposed according to the invention is further characterized in that the connecting joint between the first and second vacuum-insulated double-wall pipes is closed and held together by means of a clamping device, in particular a V-band clamping ring. The connecting joint is sealed by means of a sealing element, in particular a first inner sealing ring.

[0011] In an advantageous development of the device proposed according to the invention, the third vacuum-insulated double-walled pipe contains several layers of a multi-layer insulation material, comprising alternating layers of a heat-reflecting foil and a spacer layer. This solution significantly reduces heat absorption by the third vacuum-insulated double-walled pipe covering the joint, and ideally eliminates it entirely.

[0012] Advantageously, the device proposed according to the invention provides that the V-band clamping ring is made of a material with a higher coefficient of thermal expansion than the material from which the flanges at the end regions are made, so that the V-band clamping ring contracts more strongly than the flanges during cooling. This ensures that the clamping effect of the V-band clamping ring is maintained under all operating conditions.

[0013] Advantageously, the device proposed according to the invention is designed such that sliding rings made of a PTFE material or PTFE foam are arranged on an outer shell of the first and second vacuum-insulated, double-walled pipes, in particular their outer pipes, which enable the axial movement of the third vacuum-insulated double-walled pipe. The vacuum-insulated double-walled pipe serving as a connecting sleeve can thus be moved more easily within its axial displacement range. Advantageously, the device proposed according to the invention is designed such that the outer pipes are integrally joined to the inner pipes of the double-walled pipes in order to hermetically seal a vacuum space inside the double-walled pipes.

[0014] Furthermore, the device proposed according to the invention is characterized in that a closure mechanism of the V-band clamping ring extends into the tapers of the first and second outer tubes of the first and second vacuum-insulated double-walled tubes to be connected. Thus, the closure mechanism extending into these tapers does not prevent the axial displacement of the third vacuum-insulated double-walled tube.

[0015] Advantageously, the device proposed according to the invention provides that the tapers in the outer tubes have a removable volume filler piece which is made of a material with lower thermal conductivity.

[0016] Advantageously, the device proposed according to the invention further provides that, in the region of the connecting joint, circular rings between the outer tubes of the first and second vacuum-insulated, double-walled tubes and the inner tube of the third vacuum-insulated, double-walled tube are sealed by means of at least two outer sealing rings. This provides redundancy in the event of failure of the internally arranged sealing ring.

[0017] Advantageously, the device proposed according to the invention provides that an axial displacement range of the third vacuum-insulated, double-walled pipe is delimited by at least one L-shaped profile ring. The vacuum-insulated third double-walled pipe, designed as a sliding sleeve, is fixed by means of a holding mechanism, and the first and second vacuum-insulated double-walled pipes are held therein. An external fixation is achieved by means of a clamping piece, a profile ring, and an annular groove, or a removable clamping piece and an additional clamp engage on one side of the profile ring and the connecting sleeve.Furthermore, the device proposed according to the invention is designed such that the inner tube of the third vacuum-insulated, double-walled pipe serving as a sliding sleeve is provided with a first metallic bellows, and the outer tubes of the first and second vacuum-insulated double-walled pipes are provided with a second metallic bellows. The first and second metallic bellows can significantly extend the path for heat flow.

[0018] The device proposed according to the invention further provides that an air volume between the first metallic bellows and the second metallic bellows is filled with a filling material with low thermal conductivity. This improves the insulation effect in the area of ​​the connecting joint, covered by the metallic bellows.

[0019] In an advantageous development of the device proposed according to the invention, it is provided that, in the region of the first metallic bellows in the inner pipe, third metallic bellows are located in the outer pipe. These third metallic bellows impart flexibility to the third double-wall pipe in the form of the sliding sleeve in these regions, enabling the sliding sleeve to be displaced over curved regions of the vacuum-insulated first and second double-wall pipes, in particular by the bellows being located in the region of one or both ends of the sliding sleeve or extending substantially over its entire length. As a result, the device proposed according to the invention, in particular the third vacuum-insulated double-wall pipe serving as the sliding sleeve, can be further improved in terms of its insulating effect.

[0020] In the device proposed according to the invention, it is further advantageously provided that the first metallic bellows in the inner tube of the third vacuum-insulated double-walled tube is enclosed by a reinforcing mesh. When higher pressures occur, the reinforcing mesh further improves the mechanical properties of the inner tube.

[0021] The device proposed according to the invention comprises inserts covering the second outer sealing rings in the end regions of the first and second vacuum-insulated double-walled pipes. These inserts are made of a material with lower thermal expansion than the surrounding pipe material, in particular of INVAR, CFRP (if the surrounding material is steel), or steel (if the surrounding material is aluminum). In an advantageous development of the device proposed according to the invention, additional walls forming annular insulation layers are formed in the first and second vacuum-insulated double-walled pipes to shorten the axial displacement path, which walls significantly extend the heat flow path along the additional metallic walls. This design variant also advantageously influences heat losses and the maintenance of a cryogenic temperature level.

[0022] In the device proposed according to the invention, it is further provided that the annular insulation layers are filled with annular insulation inserts made of a material with low thermal conductivity.

[0023] Advantageously, in the device proposed according to the invention, a displaceable ring is arranged in the region of the connecting joint above the two outer sealing rings, which is positioned by at least one annularly divisible insulation layer and is made of a material which has a higher thermal volume expansion compared to the material of the vacuum-insulated double-wall pipes.

[0024] In one embodiment, the device proposed according to the invention can also be designed such that a number of concentrically arranged, annular insulation layers are arranged between the inner and outer tubes of the first and second vacuum-insulated double-walled tubes. Depending on the space available, this embodiment can further improve the thermal insulation effect.

[0025] Furthermore, the invention relates to the use of the device in an aircraft for conveying liquid or gaseous deep-cold, cryogenic media, in particular hydrogen.

[0026] Advantages of the invention

[0027] According to the invention, several coupling connections are proposed for connecting vacuum-insulated double-walled pipes carrying a gaseous or liquid cryogenic medium. These allow a single pipe to be inserted laterally between other, already assembled pipes and their butt joint to be closed without significantly moving the adjacent pipes in the axial direction. Only a pipe serving as a sleeve, in particular a vacuum-insulated and double-walled pipe, which covers a joint from the outside, is moved in the axial direction. This connection can also be released again in a similar manner during maintenance, allowing only one pipe segment to be replaced without significantly moving or removing the adjacent pipe segments.This advantageously prevents axial movement of a pipe, allowing assembly and disassembly work to be carried out on adjacent pipes with extremely low assembly and disassembly effort. In the solution proposed by the invention, the double-walled, vacuum-insulated pipes are not inserted into one another, but rather abut one another in the area of ​​their flanges at the end faces. To prevent extreme heat conduction to the outside within this connecting joint, the vacuum-insulated double-walled pipes are enclosed by a third, also double-walled, vacuum-insulated pipe, which covers the inner pipes like a sleeve on both sides of the joint. When closed, a clamping ring and a stop prevent displacement of this sleeve-like, third vacuum-insulated double-walled pipe, which serves as insulation.If the clamping ring is opened, the vacuum-insulated third double-wall pipe, which serves as an insulation sleeve, can be moved in the axial direction on one side onto one of the end areas of the two pipes covered by it, so that the end of the sleeve-like, vacuum-insulated double-wall pipe no longer protrudes beyond the end of one of the internally mounted, vacuum-insulated double-wall pipes, so that the first and second vacuum-insulated double-wall pipes can be moved radially towards each other and a lateral assembly or disassembly of these pipes is possible.

[0028] In the closed state, the first and second vacuum-insulated double-walled pipes are also secured against lateral displacement, either by the clamping ring, possibly also together with another part, also securing the first and second vacuum-insulated double-walled pipes against displacement in both directions, or by the first and second vacuum-insulated double-walled pipes each having a flange at their connecting joint, which is connected to the adjacent flange via a separate connecting mechanism, for example in the form of a V-band clamping ring.

[0029] The overlap length between the first and second vacuum-insulated double-walled pipes and the third pipe, which is also double-walled and vacuum-insulated and serves as an insulation sleeve, extends the path that heat must flow along a metal wall to create an insulating effect.

[0030] The solution proposed according to the invention provides examples of how the heat flow path can be extended without requiring a further extension of the overlap length in order to use the coupling connections proposed according to the invention in their embodiments even with reduced axial installation space.

[0031] Furthermore, it should be emphasized that according to an embodiment of the present invention, the area around the coupling in which straight pipes run is shortened, since the sliding sleeve can also be moved to a certain extent around bends in the pipeline of double-walled pipes.

[0032] Short description of the drawings

[0033] The invention is described in more detail below with reference to the drawings.

[0034] They show:

[0035] Figure 1 shows a first embodiment of the device according to the invention for connecting vacuum-insulated first and second double-walled pipes,

[0036] Figure 2 shows a variant of the device according to the invention with bellows made of metallic material on an inner pipe of the third vacuum-insulated double-wall pipe serving as a sliding sleeve, Figure 3 shows the representation of the third vacuum-insulated double-wall pipe serving as a sliding sleeve over the entire axial length,

[0037] Figure 4 shows a variant of the device according to the invention with insulating inserts arranged in the area of ​​the two outer sealing rings,

[0038] Figure 5 shows a variant of the inserts according to Figure 4,

[0039] Figure 6 shows the arrangement of insulation layers between the inner pipe and the outer pipe when the pipes are designed with additional walls and

[0040] Figure 7 shows an arrangement of concentrically arranged insulation layers in the area of ​​a connecting joint between two vacuum insulated

[0041] Double-wall pipes.

[0042] Embodiments of the invention

[0043] In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0044] Figure 1 shows a design with a V-band clamping ring 5 and matching flanges 14a, 14b at the connecting joint 32 of the inner pipes 1a, 2a. An inner pipe 1a and an outer pipe 2b represent a first double-walled pipe 1, an inner pipe 2a and an outer pipe 2b represent a second double-walled pipe, and an inner pipe 3a and an outer pipe 3b form a third double-walled pipe as a connecting sleeve 3. All double-walled pipes and the double-walled pipe serving as a displacement sleeve 3 are vacuum-insulated.

[0045] On the end face of the connecting joint 32 there is a first inner seal 4a, which serves as the primary seal against the escape of the cryogenic medium from the interior of the inner tubes 1a, 2a. The first inner seal 4a is pressed against the opposite flanges 14a, 14b by closing the V-band clamping ring 5. The V-band clamping ring 5 is dimensioned such that after assembly at room temperature when the connecting joint 32 cools down as a result of the inner tubes 1a, 2a being filled with cryogenic medium, it does not loosen, but rather tightens, for example by making the V-band clamping ring 5 from a material with a slightly higher coefficient of thermal expansion than the flanges 14a, 14b of the inner tubes 1a, 2a, thus contracting more than them when cooling down. The two vacuum-insulated double-walled pipes each consist of an inner pipe 1 a or 2a and an outer pipe 1 b or 2b, which are connected at the pipe ends (e.g.at the flanges 14a, 14b under the V-band clamping ring 5) are connected to each other in an airtight manner, for example, welded, and evacuated, i.e., a vacuum exists in the annular space between the vacuum-insulated double-walled tubes. To minimize the heat flow caused by thermal radiation from the outside to the inside into the cryogenic medium, a multilayer insulation material (MLI) 12 is located within the vacuum space. This material consists of several alternating layers of a heat-reflecting foil and a spacer layer between the foils.

[0046] When the connection is closed, a sliding sleeve 3 is located around the connecting joint 32 of the inner pipes 1a, 2a. This sleeve consists of a short piece of a similarly vacuum-insulated pipe, with the inner pipe 3a and outer pipe 3b connected hermetically at both ends, multi-layer insulation material 12 (MLI), and a vacuum in between. The V-band clamping ring 5, like other V-band clamps, has a locking mechanism that allows it to be folded open when opened and tightened when closed. Since this mechanism takes up some space, the outer pipes 1b and 2b must have tapers 34, 35 in this area so that the V-band clamping ring 5 can be attached far enough inward that the sliding sleeve 3 can be slid over it without dragging.

[0047] This creates a gap between the outer pipes 1b, 2b, the V-band clamping ring 5, and the inner pipe 3a of the connecting sleeve 3, the temperature of which drops during operation with a cryogenic medium due to a cold bridge in the area of ​​the flange connection. To prevent or at least significantly reduce the formation of ice or the condensation of air components in this gap, this gap is filled with a volume filler 9, which, for example, consists of a material with comparatively low thermal conductivity, but is also suitable for cryogenic temperatures, and is not prone to ignition in the presence of liquefied atmospheric oxygen, such as PTFE in various variants, optionally also in foam form.The volume filler piece 9 is designed in such a way that it can be mounted and removed again after the V-band clamping ring 5 has been closed, for example by being designed to be divisible or hinged, either by means of precisely fitting plug-in connections, by means of sufficient inherent flexibility of the material or by means of flexible, joint-like areas of the volume filler piece 9.

[0048] In addition to the volume filler 9, a second outer seal 4b is located on the outer sides of each of the two outer pipes 1b and 2b in a sealing groove, which seals the annular rings between the inner pipes 1a, 2a and the inner pipe 3a of the sliding sleeve 3 on both sides of the connecting joint 32. These sealing rings 4b represent the secondary sealing level against the escape of the cryogenic medium, but also prevent the penetration of outside air into the cold area of ​​the connection, where it could condense or freeze. Outside the second outer sealing rings 4b are several sliding rings 10, for example made of PTFE, which can also have a sealing function, also to reduce the penetration of water vapor and ice formation, but whose further function is also to improve the sliding of the sliding sleeve 3 on the outer pipes 1b, 2b.

[0049] An axial displacement range 36 of the sliding sleeve 3 is limited by two profile rings 11, for example, L-shaped, welded to the outer pipes 1b, 2b. These rings are positioned such that one of the profile rings 11 serves as a stop for the closed position, and the other profile ring 11, attached to the opposite pipe, serves as a stop for the open position. In the closed position, the sliding sleeve 3 is positioned such that the heat flow resistance from both ends of the sliding sleeve 3 to the inner connection is almost equal. With a nearly symmetrical connection and identical pipe wall thicknesses, an inner coupling is located centrally in the sliding sleeve 3.In the open position, the sliding sleeve 3 is pushed to the side far enough that the inner connection is accessible from the outside and the volume filler piece 9 and the V-band clamping ring 5 can be opened, whereupon the two inner pipes 1a, 2a can be moved radially relative to each other. This enables lateral assembly or disassembly of the connection without the inner pipes 1a, 2a having to be moved in the longitudinal direction of the pipe, which in turn enables assembly or disassembly of individual pipe components without the need to move or disassemble adjacent pipes of the line.

[0050] Figure 2 shows a modified version of the illustration according to Figure 1, wherein the inner pipe 3a of the sliding sleeve 3 and the outer pipes 1b, 2b of the vacuum-insulated pipes are provided with metallic first and second bellows 15, 16, which are hermetically welded or soldered to the respective walls in order to maintain the vacuum therein. The purpose of these first and second bellows 15, 16 in this case is to extend the path that heat has to travel along the respective metal walls in order to reach the cryogenic medium from the outside, either to improve the insulating effect of the connection or to shorten the installation space of the sliding sleeve 3 in the longitudinal direction of the pipe while maintaining the same insulating effect, which thus also shortens the distance required for displacement.Since the vacuum insulated double-wall pipes are straight in the area of ​​the connection and in the axial displacement area 36, ​​this shortens the required distance to the next bend or branch of the vacuum insulated double-wall pipes.

[0051] Similar to the volume filler 9, the air volume in the first and second bellows 15, 16 is optionally filled with a filling material 17 with low thermal conductivity, which ideally also improves the sliding of the sliding sleeve 3 and has a certain degree of flexibility, such as PTFE or PTFE foam.

[0052] Furthermore, the first and second bellows 15, 16 increase the flexibility of the vacuum-insulated double-wall pipes in the connection area. For this purpose, additional bellows can be inserted into the inner pipes 1a, 2a and the outer pipe 3b of the sliding sleeve 3. These do not extend the heat flow path and therefore do not affect the insulation effect, but may be necessary for sufficient flexibility of the connection or to compensate for thermal expansion when switching between cryogenic temperatures and normal temperatures.

[0053] Figure 3 shows a further embodiment of the illustration according to Figure 2, wherein the outer tube 3b of the vacuum-insulated sliding sleeve 3 is also designed as a third metallic bellows 20 over almost its entire length. However, it can also be provided that the third bellows 20 does not run over the entire length, but is formed, for example, only on one half of the sliding sleeve 3, for example, if a bend is formed on this side in the axial displacement region 36, or if, for example, the axial displacement region 36 between the seals 4b is designed as a straight tube and consists of bellows outside the seals because only the outer ends of the sliding sleeve 3 run on bends, for example. The third bellows 20 on the inner tube 3a of the vacuum-insulated sliding sleeve 3 also cover the largest possible portion, only the areas of the seal seats are excluded.In this design, the entire vacuum-insulated sliding sleeve 3 exhibits greater flexibility, allowing it to be moved even when the connected vacuum-insulated double-wall pipes exhibit a bend, for example, a bend in the area of ​​a removable clamping piece 13. In this case, this removable clamping piece 13 must also be precisely designed to fit the bent pipe. This bend is not shown in Figure 3 for reasons of clarity.

[0054] To ensure a stable fit in the event of vibrations when closed due to the greater flexibility of the sliding sleeve 3, the removable clamping piece 13 is also shaped in this case to prevent displacement of the sleeve end there in both directions. To similarly secure the other end of the sliding sleeve 3, an additional clamp 19 is provided on the opposite side.

[0055] A further addition to the designs shown in Figures 2 and 3 could be that bellows, which may have to withstand higher internal pressures in the event of a failure for redundancy reasons, are wrapped with a reinforcing braid. This increases resistance to the internal pressure while still ensuring flexibility. This could be particularly useful for the first bellows 15 on the inner pipe 3a of the sliding sleeve 3, with the braids then being positioned in the vacuum space of the sliding sleeve 3, beneath the multi-layer insulation material 12 (MLI). There, they would not interfere with the sliding of the sliding sleeve 3, but at the same time would also prevent bulging of the second bellows 16, which are located further inside, since the failure of increased internal pressure should only occur during operation, in the closed state, and opening the connection without prior pressure relief should not be carried out anyway.

[0056] Figure 4 shows a further embodiment of the solution proposed according to the invention, wherein the removable clamping piece 13 here has an alternative design 23 and is clamped over the sliding sleeve 3. It also engages over the stop for the closed state and thus fixes the sliding sleeve 3 against displacement in either direction relative to the first vacuum-insulated double-walled pipe. In order to simultaneously achieve axial displacement of the sliding sleeve 3 relative to the second vacuum-insulated double-walled pipe, an annular groove 24 is located in the outer pipe 2b of the second vacuum-insulated double-walled pipe, into which the alternative design of the clamping piece 23 engages when folded in. This simultaneously protects the second vacuum-insulated double-walled pipe from slipping out due to the internal pressure in the pipe.This type of clamp can also be combined with the previously described embodiments, which include the V-band clamping ring 5, providing additional fixation. However, in the embodiment shown in Figure 4, the clamping piece 23 and the annular groove 24 eliminate the need for further connection of the vacuum-insulated double-walled pipes in the sliding sleeve 3, thus providing a simpler solution, especially in the case of lower internal pressures in the cryogenic medium.

[0057] A further aspect of the illustration according to Figure 4, which can also be combined with the previous embodiments, are inserts 22 made of a material with lower thermal expansion than the surrounding pipes (e.g. Invar, CFRP, alternatively steel for surrounding pipes made of aluminum). These inserts 22, which are primarily located in the area of ​​the second outer sealing rings 4b, reduce thermal shrinkage of the vacuum-insulated double-walled pipes 1, 2 with respect to the sliding sleeve 3. Since the two inner pipes 1a, 2a, when filled with cryogenic medium, become colder in the connection area than the sliding sleeve 3 located further out, this prevents the second outer sealing rings 4b from experiencing less contact pressure due to thermal shrinkage and thus from having greater leakage.A similar principle is used in so-called Johnston couplings or bayonet couplings with the so-called ShrinkFit sealing principle, but in conjunction with another coupling that cannot be connected or disconnected without axial movement of the pipes.

[0058] Figure 5 shows a further embodiment of the illustration according to Figure 4 with a different seal at the connecting joint 32 of the outer tubes (1b, 2b?). Even though "spring-loaded PTFE" sealing rings are shown in Figures 1 to 3, the invention is not limited to this sealing principle; other seal forms are also possible. The seal at the connecting joint 32 must withstand preload during assembly, especially without an additional V-band clamping ring 5 in this area, so that despite the flexibility of the outer clamping piece 23 and the shortening of the vacuum-insulated double-walled tubes when filled with cryogenic medium, sufficient contact pressure is still present between the profile rings 11 and the annular groove 24 for sealing.

[0059] Figure 6 shows a further embodiment of the connection, wherein, to shorten the axial displacement range 36 of the sliding sleeve 3, first and second annular insulation layers 25, 26 are formed, which extend the path of the heat flow in the radial direction. The path of the heat flow along the highly conductive metal walls of the vacuum-insulated double-walled pipes is extended. Although the direct radial path through the insulation material is not significantly longer, it has a significantly higher heat flow resistance. The first and second annular insulation layers 25, 26 comprise additional annular walls 1c, 1d, 2c, 2d in the vacuum-insulated double-walled pipes, which form an annular cavity filled with filler pieces made of a material with low thermal conductivity (e.g., PTFE, PTFE foam, other foam, aerogel).While the filler pieces are generally not moved during assembly in the aircraft, a further filler piece in the form of an annular, divisible insulation layer 27 made of the same or a similar material is provided in the central region of the connection. This filler piece is designed so that it can be removed, for example by being divisible or hinged, either through precisely fitting plug-in connections, through sufficient inherent flexibility of the material, or through flexible, hinged areas of the filler piece. Alternatively, the volumes of the insulation layers 25, 26, and 27 could also be filled with an inert gas that does not explode upon contact with hydrogen and ideally does not condense in the operating temperature range. Figure 6 also shows a further movable seal 28, against which the second outer sealing rings 4b seal.When closed, this movable seal 28 covers the two outer sealing rings 4b on both sides of the connecting joint 32 and is held in position by a flange at one end through the insulation layer 27. If the insulation layer 27 is removed for disassembly after the sliding sleeve 3 has been opened, the movable sealing ring 28 can be pushed laterally into a designated cavity in the first annular insulation layer 25, so that this connection is also opened and the vacuum-insulated double-wall pipes can be separated from each other by lateral displacement.In order to ensure sufficient contact pressure between the movable sealing ring 28 and the two outer sealing rings 4b even after cooling by the cryogenic medium, the movable sealing ring 28 is ideally made of a material with higher thermal expansion than that of the vacuum-insulated double-walled pipes, for example aluminum or a steel alloy with high thermal expansion (for example manganese steel).

[0060] The annular insulation layers 25, 26, 27, formed by the additional walls 1c, 1d, 2c, 2d, can also be combined with the V-band clamping ring 5 described in Figures 1 to 3 and the flanges 14a, 14b instead of the movable sealing ring 28. Likewise, in the embodiment according to Figure 6, additional seals can be inserted between the inner pipe 3a of the sliding sleeve 3 and the outer pipes 1b, 2b, as is also the case in the embodiments according to Figures 1 to 5.

[0061] Figure 7 shows a further embodiment of the solution proposed according to the invention, in which several radial, concentrically arranged insulation layers 25, 26, 27 connected in series are provided in order to further improve the thermal insulation effect. The intermediate space for the annular, divisible insulation layer 27 is omitted in this case. This design allows the installation space along the pipe direction to be further shortened, but the installation space in the radial direction is increased. Depending on the specific spatial conditions in the installation space, such a design variant can be advantageous in some cases. In Figure 7, a double bellows 29a, 29b is shown on both sides at the transitions between the connection area and the vacuum-insulated double-wall pipes, each with an inner bellows 29a and an outer bellows 29b of the vacuum-insulated double-wall pipes.Such bellows 29a, 29b in vacuum-insulated double-wall pipes may be necessary here (and also in the variants shown in Figures 1 to 6) to compensate for tolerances in the connection area and, if necessary, to allow for compressive preload on the first inner seal 4a so that it still experiences sufficient contact pressure even after cooling in the cold state. The bellows 29a, 29b can be covered with braided hoses to withstand higher internal pressure.

[0062] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art.

[0063] List of reference symbols

[0064] 1a inner pipe, first double-wall pipe

[0065] 1 b Outer pipe, first double-wall pipe

[0066] 1c Additional wall, first double-wall pipe

[0067] 1d Additional wall, first double-wall pipe

[0068] 2a inner pipe, second double-wall pipe

[0069] 2b Outer pipe, second double-wall pipe

[0070] 2c Additional wall, second double-wall pipe

[0071] 2d Additional wall, second double-wall pipe

[0072] 3a inner pipe, third double-wall pipe

[0073] 3b Outer pipe, third double-wall pipe

[0074] 3 sliding sleeve

[0075] 4a First inner seal

[0076] 4b Second, outer sealing rings

[0077] 5 V-band clamping ring

[0078] 6 Flow cross-section

[0079] 7 Surroundings

[0080] 9 Volume filler with lower thermal conductivity

[0081] 10 sliding ring (PTFE, PTFE foam)

[0082] 11 professional ice rings

[0083] 12 Multi-layer insulation material (MLI)

[0084] 13 Removable clamping piece

[0085] 14a First flange

[0086] 14b Second flange

[0087] 15 First metallic bellows

[0088] 16 Second metallic bellows

[0089] 17, Filling material for cavities

[0090] 18

[0091] 19 Additional terminal

[0092] 20 Third metallic bellows

[0093] 22 Insert

[0094] 23 Alternative design of the clamping piece 13

[0095] 24 ring groove

[0096] 25 First annular insulation layer

[0097] 26 Second annular insulation layer Ring-shaped, divisible insulation layer

[0098] Movable ring (sealing) a Inner bellows b Outer bellows

[0099] End area of ​​the first double-walled pipe

[0100] End area of ​​second double-wall pipe

[0101] connecting joint

[0102] Outer jacket

[0103] First rejuvenation

[0104] Second rejuvenation

[0105] Axial displacement range

[0106] Concentrically arranged insulation layers 25

Claims

Patent claims 1. Device for connecting vacuum insulated first and second Double-walled pipes (1a, 1b, 1c, 1d; 2a, 2b, 2c, 2d), the pipe ends of which are opposite one another as flanges (14a, 14b) and in whose Flow cross-section (6) a gaseous or a liquid cryogenic medium flows, characterized in that the vacuum-insulated double-walled pipes (1 a, - 2d) are each enclosed at their end regions (30, 31) by a further, third vacuum-insulated double-walled pipe (3a, 3b) as a sliding sleeve (3), which is axially displaceable on the first and second vacuum-insulated double-walled pipes (1 a - 2d) in such a way that the opposing flanges (14a, 14b) become accessible.

2. Device according to claim 1, characterized in that the vacuum-insulated third double-walled pipe (3a, 3b) covers a connecting joint (32) between the first flange (14a) and the second flange (14b) as a sliding sleeve (3).

3. Device according to claims 1 and 2, characterized in that the connecting joint (32) between the first and second vacuum-insulated, double-walled pipes (1 a - 2 d) is closed and held together by means of a clamping device, in particular a V-band clamping ring (5).

4. Device according to claims 1 to 3, characterized in that the connecting joint (32) is sealed by a seal, in particular a first inner seal (4a).

5. Device according to one of claims 1 to 4, characterized in that in the vacuum-insulated third double-walled tube (3, 3a, 3b) several layers of a multi-layer insulation material (12) are accommodated, which comprise alternately arranged layers of a heat-reflecting film and a spacer layer.

6. Device according to one of claims 1 to 3, characterized in that the V-band clamping ring (5) is made of a material which has a higher thermal expansion coefficient than the material from which the flanges (14a, 14b) in the end regions (30, 31) are made, so that the V-band clamping ring (5) contracts more strongly than the flanges (14a, 14b) during cooling.

7. Device according to one of claims 1 to 6, characterized in that on an outer jacket (33) of the first and second vacuum-insulated double-walled tubes (1 a - 2 d), in particular their outer tubes (1 b, 2 b), sliding rings (10) made of a PTFE material or PTFE foam are arranged, which allow an axial movement of the vacuum-insulated third double-walled tube (3, 3a, 3b).

8. Device according to one of claims 1 to 7, characterized in that in the region of the flanges (14a, 14b) the outer tubes (1b, 2b) are joined by a material fit to the inner tubes (1a, 2a) of the double-walled tubes in order to hermetically seal off a vacuum space inside the double-walled tubes.

9. Device according to one of claims 1 to 8, characterized in that a closure mechanism of the V-band clamping ring (5) is immersed in tapers (34, 35) of the first and second outer tubes (1b, 2b).

10. Device according to one of claims 1 to 9, characterized in that a removable volume filler (9) made of a material with lower thermal conductivity is embedded in the tapers (34, 35) of the outer tubes (1b, 2b) of the vacuum-insulated double-walled tubes.

11. Device according to one of claims 1 to 10, characterized in that in the region of the connecting joint (32) circular rings between the outer tubes (1b, 2b) of the vacuum-insulated double-walled tubes and the inner tube (3a) of the vacuum-insulated third double-walled tube (3, 3a, 3b) are sealed by means of at least two outer sealing rings (4b).

12. Device according to one of claims 1 to 11, characterized in that a holding mechanism designed as a sliding sleeve (3), vacuum-insulated third double-wall pipe is fixed and the first and second double-wall pipes are held therein, wherein an external fixation by means of a clamping piece (23) fixes a profile ring (11) and an annular groove (24) or a removable clamping piece (13) and an additional clamp (19) each engage on one side of the profile ring (11) in the latter and in the sliding sleeve (3).

13. Device according to one of claims 1 to 12, characterized in that the inner tube (3a) of the vacuum-insulated, third double-walled tube (3a, 3b) serving as a sliding sleeve (3) is provided with a first metallic bellows (15) and the outer tubes (1b, 2b) of the first and second vacuum-insulated double-walled tubes (1a - 2d) are provided with a second metallic bellows (16).

14. Device according to claim 13, characterized in that an air volume between the first metallic bellows (15) and the second metallic bellows (16) is filled with a filling material (17) with low thermal conductivity.

15. Device according to claims 1 to 13, characterized in that in the region of first metallic bellows (15) in the inner pipe (3a), third metallic bellows (20) are connected in the outer pipe (3b), which give the third double-walled pipe, in particular the sliding sleeve (3), a flexibility in these regions, which enables the sliding sleeve (3) to be moved over curved regions of the first and second vacuum-insulated double-walled pipes, in particular in that the bellows (15, 20) are located in the region of one end or both ends of the sliding sleeve (3) or extend substantially over its entire axial length.

16. Device according to one of claims 13 to 15, characterized in that the first metallic bellows (15) in the inner tube (3a) of the double-walled third double-walled tube (3, 3a, 3b) is enclosed by a reinforcing mesh.

17. Device according to claims 1 to 16, characterized in that in end regions (30, 31) of the first and second vacuum-insulated, double-walled tubes (1 a - 2d) the second outer sealing rings (4b) surrounding Inserts (22) are arranged which are made of a material with lower thermal expansion than that of the surrounding pipe material, in particular of INVAR, CFRP (if the surrounding material is steel) or of steel (if the surrounding material is aluminum).

18. Device according to one of claims 1 to 17, characterized in that in order to shorten the axial displacement region (36) necessary for an insulating effect, additional walls (1 c, 1 d, 2 c, 2 d) forming annular insulation layers (25, 26) are formed in the first and second vacuum-insulated double-walled tubes (1 a - 2 d), which extend the path of the heat flow along the additional metallic walls (1 c, 1 d, 2 c, 2 d).

19. Device according to claims 1 to 18, characterized in that the annular insulation layers (25, 26) are filled with a material with low thermal conductivity.

20. Device according to one of claims 1 to 19, characterized in that in the region of the connecting joint (32) above the two outer sealing rings (4b) a displaceable ring (28) is arranged, which is positioned by means of an annularly divisible insulation layer (27) and is made of a material with higher thermal expansion compared to the material of the vacuum-insulated double-walled pipes.

21. Device according to one of claims 1 to 20, characterized in that a number of concentrically arranged, annular insulation layers (39) are arranged between the inner tubes (1a, 1b) and the outer tubes (2a, 2b) of the first and second vacuum-insulated double-walled tubes (1a - 2d).

22. Use of the device according to one or more of claims 1 to 21 in an aircraft for conveying liquid or gaseous deep-cold cryogenic media, in particular hydrogen.

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