JOHNSTON COUPLING WITH ADDITIONAL VACUUM SLEEVE

Description

Area

[0001] The invention relates to a plug-in coupling for vacuum-insulated flexible cables, also known as a "Johnston coupling." In particular, the invention relates to a Johnston coupling with an additional vacuum envelope. background

[0002] Cryogenic liquids, also known as cryogenic fluids, are often transported on ships, in tank cars, or on tank trucks. A key example is liquefied natural gas (LNG), which has a vaporization temperature of -162 °C (111 K). Loading is typically carried out using uninsulated pipes and couplings, which freeze during loading. The lack of thermal insulation leads to the evaporation of part of the cryogenic fluid, which results in energy loss because the vaporized fluid must be reliquefied elsewhere, which requires significant energy expenditure.

[0003] When loading even colder media, such as liquid hydrogen (evaporation temperature -253 °C, 20 K) or liquid helium (evaporation temperature -269 °C, 4 K), the oxygen in the ambient air, whose evaporation temperature is comparatively higher (-183 °C; 90 K), would condense on the surface of uninsulated lines and couplings. This is highly undesirable because liquid oxygen significantly increases the potential fire hazard.

[0004] Vacuum-insulated lines, manufactured by Nexans, for example, are also known for transporting such cryogenic liquids or media. For tank and loading purposes, these vacuum-insulated lines are flexible and equipped at one end with a so-called Johnston coupling, which allows two cryogenic lines to be connected without losing thermal insulation at the connection point. This reduces icing at the connection point and losses of the cryogenic medium due to evaporation. A Johnston coupling is disclosed, for example, in EP 1 957 851 B1.

[0005] Simply put, a Johnston coupling consists of two double-walled, vacuum-insulated pipes being inserted into one another. The inner diameters of such pipes are typically between 20 mm and 150 mm. However, smaller or larger inner diameters are also possible. The male part (inner double-walled pipe) is inserted into the female part (outer double-walled pipe). The coupling is also referred to as a coupling plug and coupling socket. This provides excellent thermal insulation between the outer surface and the inner media-carrying pipe. For this to happen, both double-walled pipes must be inserted into one another over a predetermined length. Depending on the medium and the desired thermal insulation, typical pipe-in-pipe lengths range from 200 mm to 600 mm. Deviations to smaller or larger lengths are possible for individual applications.

[0006] Due to the comparatively long tube-in-tube lengths, inserting the male into the female coupling part is not easy, because the cryogenic line with the male coupling plug has a considerable weight and, in addition, the coupling plug should not drag along the interior of the coupling socket in order to avoid damage to the surface.

[0007] To address these difficulties, European patent application EP 3 670 999 A1 proposes a Johnston coupling with a linear displacement unit. The displacement unit is a mechanical aid that facilitates the insertion of the coupling plug into the coupling receptacle.

[0008] CN 102 606 821 A discloses a plug-in coupling between two vacuum-insulated cryogenic lines, with a female coupling having an annular gap to accommodate a male coupling. A media-carrying line inside the plug-in coupling is insulated from the outside by several vacuum layers. The female coupling and male coupling are connected by means of flanges, in the area of ​​which a seal is arranged.

[0009] Based on this, the present invention has the object of creating a plug-in coupling for vacuum-insulated cryogenic lines which solves or at least improves the above-mentioned problems. Summary of the invention

[0010] To achieve this object, the invention proposes, according to a first aspect, a plug-in coupling for connecting a first to a second double-walled, vacuum-insulated cryogenic line, each of which has a media-carrying inner tube (307, 336). The plug-in coupling comprises a coupling plug and a coupling socket. The coupling plug has an inner and an outer tube section as well as a first connecting flange and is connected to the first cryogenic line. The coupling socket has an inner and an outer tube section as well as a second connecting flange and is connected to the second cryogenic line. The outer tube section of the coupling socket is welded to the second connecting flange. The end of the outer tube section remote from the connecting flange is connected in a vacuum-tight manner to one end of the inner tube section of the coupling socket by means of a connecting ring.Between the inner and outer tube sections of the coupling socket, an annular gap is formed, open in the area of ​​the second connecting flange, which is surrounded by an insulating vacuum on both its inner and outer circumferences. The other end of the inner tube section is welded to a seal holder. The media-carrying inner tube of the second cryogenic line is also welded to the seal holder. The seal holder carries a seal, which, when the plug-in coupling is assembled, is in contact with the coupling plug and seals the media-carrying inner tubes of the first and second cryogenic lines.

[0011] The insulating vacuums adjacent to the inner and outer circumferences of the open annular gap improve the thermal insulation of the plug-in coupling. Simply put, the proposed design extends the path that heat penetrating the plug-in coupling from the outside must travel before the heat reaches a media-carrying line. For a given length of a plug-in coupling, this results in improved thermal insulation compared to conventional Johnston couplings known from the prior art. Conversely, the plug-in coupling according to the invention can be built shorter than a conventional Johnston coupling in order to achieve a comparable level of thermal insulation. The shorter design of the plug-in coupling offers advantages in handling, particularly when the coupling plug is to be inserted into the coupling socket.The shorter design makes it easier to insert the male into the female coupling part, saves space and makes sealing easier due to the smaller angular tolerance.

[0012] In practical application, it has therefore proven to be useful if the coupling plug is inserted into the open annular gap when the plug-in coupling is assembled.

[0013] Advantageously, the outer and inner tube sections of the coupling plug are each connected at a first end to the first connecting flange and at the second end to a connecting ring. An annular gap is formed between the inner and outer tube sections, in which an insulating vacuum exists. The insulating vacuum in the coupling plug contributes to the thermal insulation of the plug-in coupling as a whole.

[0014] In practical application, it has therefore proven to be useful if the coupling plug is inserted into the open annular gap when the plug-in coupling is assembled.

[0015] Advantageously, the outer and inner tube sections of the coupling plug are each connected at a first end to the first connecting flange and at the second end to a connecting ring. An annular gap is formed between the inner and outer tube sections, in which an insulating vacuum exists. The insulating vacuum in the coupling plug contributes to the thermal insulation of the plug-in coupling as a whole.

[0016] According to an advantageous development, the annular gap is connected to an insulating vacuum in the first cryogenic line via at least one flow channel. Typically, the insulating vacuum of the cryogenic line is pumped anyway, so no additional measures are required to generate the insulating vacuum in the coupling plug.

[0017] According to an expedient further development, the second connecting flange is connected to an outer pipe of the second cryogenic line.

[0018] The inner tube section can be connected to the outer tube section of the coupling socket by means of a connecting ring. The connecting ring closes off an annular gap between the inner and outer tube sections of the coupling socket, which is open on the other side to accommodate the coupling plug.

[0019] In a further development of the plug-in coupling according to the invention, the coupling socket and the coupling plug have complementary centering means. The centering means ensure that the coupling plug sits correctly centered in the coupling socket.

[0020] In a particularly advantageous embodiment of the plug-in coupling, the inner tubes of the first and second cryogenic lines are thermally insulated from the exterior in the area of ​​the plug-in connection by three stacked insulating vacuums. "Stacked" is to be understood as meaning that three separate spaces define the insulating vacuums. The separated spaces are located one above the other, viewed radially.

[0021] According to a second aspect of the invention, a loading device for cryogenic fluids with a plug-in coupling according to the first aspect of the invention is proposed. The loading device realizes all the advantages described in connection with the plug-in coupling. Short description of the drawing

[0022] The invention is explained in more detail below using two exemplary embodiments with reference to the accompanying figures. All figures are purely schematic and not to scale. They show: Fig. 1 a schematic cross-sectional view of a conventional plug-in coupling in the separated state; Fig. 2 the plug-in coupling from Figure 1 in the assembled state; Fig. 3 a schematic cross-sectional view of a plug-in coupling according to the invention in the separated state; and Fig. 4 the plug-in coupling from Figure 3 in assembled condition.

[0023] Identical or similar elements are provided with identical or similar reference numerals in the figures. Example

[0024] Figure 1 shows a conventional plug-in coupling, designated as a whole by the reference numeral 100. The plug-in coupling 100 includes a coupling plug 101 and a coupling socket 102, which are Figure 1before assembly and with a small distance between them.

[0025] The coupling plug 101 is connected to a first cryogenic line 103, and the coupling socket 102 is connected to a second cryogenic line 104. The first cryogenic line 103 has an outer tube 106 and an inner tube 107, which are separated from each other by a gap 108 and thermally insulated from each other by an insulating vacuum in the gap 108. The cryogenic lines 103, 104 are double-walled, vacuum-insulated cryogenic lines.

[0026] The coupling plug 101 comprises a first connecting flange 109, an outer tube section 111, and an inner tube section 112. The outer tube 106 of the first cryogenic line 103 is welded to a projection 110 of the first connecting flange 109. On the opposite main surface of the connecting flange 109, the outer tube section 111 is welded to the first connecting flange 109. A distal end 113 of the outer tube section 111, remote from the first connecting flange 109, is connected to the inner tube section 112, which extends toward the first connecting flange 109 and is connected to the inner tube 107 of the first cryogenic line 103. An annular gap 114 is formed between the outer tube section 111 and the inner tube section 112. The intermediate space 108 is fluidly connected to the annular gap 114, so that the insulating vacuum extends into the annular gap 114 and ensures good thermal insulation of the inner pipe section 112.

[0027] At the distal end 113 of the plug-in coupling 101, the outer tube section 111 is slightly longer than the inner tube section 112 and forms a projecting edge 117, which holds an annular seal 118 that rests against the distal end 113 of the plug-in coupling 101. The seal 118 is made, for example, from an electrically insulating material, for example polytetrafluoroethylene (PTFE) or Torlon®. In other embodiments, the seal 118 is made of an electrically conductive material. An annular groove 120 is cut into the first connecting flange 109, into which a seal 121 is inserted. The seal 121 in the warm area of ​​the plug-in coupling ensures that no evaporated medium escapes, even if the seal 118 does not completely seal the plug-in coupling. The distance between the seal 118 and the first connecting flange 109 is also referred to below as length L 1 of the plug-in coupling 101.

[0028] The coupling socket 102 has a second connecting flange 122, an outer tube section 123, and an inner tube section 124. The tube sections 123, 124 are each welded at one end to the second connecting flange 122, with an annular gap 126 formed between the tube sections 123, 124. The other ends of the tube sections 123, 124 are connected to the second cryogenic line 104. The second cryogenic line has an outer tube 128 and an inner tube 129. Between the outer tube 128 and the inner tube 129, an intermediate space 130 is formed, in which an insulating vacuum prevails, which thermally insulates the inner tube 129. The outer tube 128 of the second cryogenic line 104 is connected to the outer tube section 123, and the inner tube 129 is connected to the inner tube section 124 of the coupling socket 102 via a connecting ring 131. The intermediate space 130 is fluidly connected to the annular gap 126.The insulating vacuum extends into the annular gap 126 of the coupling socket 102 and ensures good thermal insulation of the inner tube section 124 of the coupling socket 102.

[0029] On the connecting ring 131, an annular seat 132 is formed for the seal 118, which rests against the seat 132 when the coupling plug 101 is fully inserted into the coupling socket 102 ( Figure 2 ).

[0030] Figure 2 shows the plug-in coupling 100 from Figure 1in an assembled state in which the first and second connecting flanges 109, 122 are pressed together by means of fastening screws 136. The distal end 113 of the coupling plug 101 presses the seal 118 onto the seat 132 of the coupling socket 102. The seal 118 seals the transition between the coupling plug 101 and the coupling socket 102. Since the seal 118 is in contact with cryogenic media during operation of the plug-in coupling, 100 percent tightness may not be guaranteed. If cryogenic medium penetrates past the seal 118 into a space between the outer tube 111 of the coupling plug 101 and the inner tube 124 of the coupling socket 102 and evaporates there, the seal 121, which is arranged in the warm area of ​​the first or second connecting flange 109, 122, prevents evaporated medium from escaping from the plug-in coupling into the environment.This is highly undesirable in the case of flammable media such as liquid natural gas or liquid hydrogen.

[0031] The media-carrying inner tubes 112, 124 of the plug-in coupling 100 are well insulated from the outer surface of the plug-in coupling by the insulating vacuum. However, heat transfer occurs particularly where the inner tube 112 is connected to the outer tube 111 of the plug-in coupling 101 and where the inner tube 124 is connected to the outer tube 123 of the coupling socket 102. Heat penetrating from the outside must travel along the length of the vacuum-insulated area of ​​the plug-in coupling 100 to reach the medium conveyed in the inner tubes of the plug-in coupling. For this reason, the thermal insulation of the plug-in coupling 100 is better the longer the plug-in coupling is designed. However, as the length of the plug-in coupling 100 increases, its handling becomes increasingly difficult. In other words: For good thermal insulation, the plug-in coupling should be as long as possible, and for ease of handling, it should be as short as possible.Plug-in couplings implemented in practice usually represent a compromise between these conflicting requirements.

[0032] In Figure 3 An embodiment of a plug-in coupling 300 according to the invention is shown schematically and in cross-section. The plug-in coupling 300 has a coupling plug 301 and a coupling socket 302, which are Figure 3 before assembly and with a small distance between them.

[0033] The coupling plug 301 is connected to a first cryogenic line 303, and the coupling socket 302 is connected to a second cryogenic line 304. The first cryogenic line 303 has an outer tube 306 and an inner tube 307, which are separated from each other by a gap 308 and thermally insulated from each other by an insulating vacuum in the gap 308. The cryogenic lines 303, 304 are double-walled, vacuum-insulated cryogenic lines.

[0034] The coupling plug comprises a first connecting flange 309, which transitions into a cylindrical connection area 311. The connection area 311 is connected to a circumferential outer connection piece 312, on the outer circumference of which a receptacle 313 is formed for the outer tube 306 of the cryogenic line 303. The outer tube 306 is welded to the connection piece 312. Furthermore, the connection area 311 has a circumferential inner connection piece 314, on the inner circumference of which a receptacle 316 is formed for the inner tube 307 of the cryogenic line 303. The inner tube 307 is also welded to the connection piece 314.

[0035] An outer pipe section 317 and an inner pipe section 318 are welded to the connection area 311 on the side opposite the cryogenic line 303, wherein the outer pipe section 317 and the inner pipe section 318 are spaced apart from one another in the radial direction, such that an annular gap 319 forms between the outer pipe section 317 and the inner pipe section 318. At the end remote from the connection area 311, the outer pipe section 317 and the inner pipe section are connected to one another in a vacuum-tight manner by means of a connecting ring 321. The annular gap 319 is fluidly connected to the intermediate space 308 of the first cryogenic line 303 via at least one flow channel 322, such that an insulating vacuum also prevails in the annular gap 319. For mounting the coupling plug 301 on the coupling socket 302, through holes 323 for fastening screws (not shown) are provided.

[0036] The coupling socket 302 has a second connecting flange 324, which transitions into a connection area 326. The connection area 326 is connected to a circumferential outer connection piece 327, on the outer circumference of which a receptacle 328 is formed for an outer tube 329 of the cryogenic line 304. The outer tube 329 is welded to the connection piece 327.

[0037] An outer tube section 330 of the coupling socket 302 is welded into a central opening 331 of the second connecting flange 324. By means of a connecting ring 332, the end of the outer tube section 330 remote from the connecting flange 324 is connected in a vacuum-tight manner to an inner tube section 333 of the coupling socket. The other end of the inner tube section 333 is welded into a receptacle on the outer circumference of a seal holder 334. An inner tube 336 of the second cryogenic line 304 is welded to an inner circumference of the seal holder 334.

[0038] The outer tube 329 and the inner tube 336 of the second cryogenic line 304 define an intermediate space 337 in which an insulating vacuum prevails. An annular gap 338 is formed between the inner tube section 333 of the coupling socket 302 and the inner tube 336 of the cryogenic line 304, which is fluidly connected to the intermediate space 337. Accordingly, an insulating vacuum also prevails in the annular gap 338. An annular gap 339 is formed between the outer tube section 330 and the inner tube section 333, which is closed off on one side by the connecting ring 332 and open on the other side in the region of the second connecting flange 324, thus forming an annular insertion opening for the coupling plug 301. An insulating vacuum also prevails in an annular space 341 extending around the annular gap 339.On an end face facing the coupling plug, a seal 342 is arranged on the seal holder 334, which, in the assembled state of the plug-in coupling 300, rests on a seat 343 in the coupling plug 301 and seals the media-carrying inner tubes 307, 336 of the first and second cryogenic lines 303, 304, respectively (. Figure 4 ).

[0039] An annular projection 344 is formed on the second connecting flange 324, which fits into a corresponding recess 346 in the first connecting flange 309 of the coupling plug 301. The distance between the connecting ring 321 and the first connecting flange 309 corresponds to the length L 2 of the coupling plug 301.

[0040] The second connecting flange 324 also has an annular groove 347 into which a seal 348 is received. The seal 348 prevents vaporized medium from escaping from the plug-in coupling 300 if the seal 342 does not completely seal the inner tubes 307, 336.

[0041] Figure 4shows the plug-in coupling 300 in an assembled state, in which the connecting flanges 309 and 324 are pressed together by means of connection fastening screws 136. The annular projection 344 is received in the recess 346 and centers the coupling plug 301 on the coupling socket 302. The annular projection 344 and the recess 346 form complementary centering means. In other embodiments, other centering means may also be provided. The coupling plug 301 is fully inserted into the coupling socket 302, so that the seal 342 rests against the seat 343 in the coupling plug and seals the inner tubes 306, 336. In the area of ​​the plug-in coupling 300, three layers of insulating vacuum thus lie one above the other. These are, viewed in the radial direction from the inside to the outside, the annular gap 338 in the coupling socket 302, the annular gap 319 in the coupling plug 301 and the annular space 341 in the coupling socket 302.In the case of the plug-in coupling 300, the path that heat penetrating from the outside has to travel is therefore approximately twice as long as the length L 2 of the plug-in coupling 301. For the same length of the plug-in coupling 300, its thermal insulation is better compared to that in . Figure 2 shown plug-in coupling 100 better.

[0042] Conversely, for a given thermal insulation effect, a plug-in coupling 300 should be shorter than a plug-in coupling 100, which is achieved by different lengths L 1 and L 2 of the Figures 1 and 3 illustrated coupling plugs 101 and 301, respectively, where L 1 is approximately 1.3 times longer than L 2. In other embodiments, the length ratios may also be different.

[0043] The shorter overall length of the plug-in coupling 300 simplifies its handling. Furthermore, the coupling 300 saves space, and sealing in the area of ​​the seal 342 is easier due to the smaller angular tolerance, because the seal 342 deviates less from its optimal position on the seat 343 if the coupling plug 301 is not inserted exactly concentrically into the coupling socket 302. List of reference symbols

[0044] 100 Plug-in coupling 306 outer tube 101 Coupling plug 307 inner tube 102 Coupling socket 308 space 103 first cryogenic line 309 first connecting flange 104 second cryogenic line 311 Connection area 106 outer tube 312 External connection piece 107 inner tube 313 Recording 108 space 314 Internal connection piece 109 first connecting flange 316 Recording 111 outer pipe section 317 Outer tube 112 inner pipe section 318 Inner tube 113 distal end 319 Annular gap 114 Annular gap 321 connecting ring 117 Overhanging edge 322 flow channel 118 seal 323 Through holes 120 Ring groove 324 second connecting flange 121 seal 326 Connection area 122 second connecting flange 327 External connection piece 123 outer pipe section 328 Recording 124 Inner pipe section 329 outer tube 330 outer tube 126 Annular gap 331 Central opening 128 outer tube 332 connecting ring 129 inner tube 333 Inner tube 130 space 334 Seal holder 131 connecting ring 336 inner tube 132 seat 337 space 338 Annular gap 300 Plug-in coupling 339 open annular gap 301 Coupling plug 340 Insertion opening 302 Coupling socket 341 Annular space 303 first cryogenic line 304 second cryogenic line 342 seal

Claims

1. The plug-in coupling for connecting a first with a second double-walled, vacuum-insulated cryogenic line (303, 304), which in each case have a media-conducting inner pipe (307, 336), wherein the plug-in coupling (300) comprises a coupling plug (301) and a coupling socket (302), - wherein the coupling plug (301) has an inner and an outer pipe section (318, 317) as well as a first connecting flange (309) and is connected to the first cryogenic line (303), - wherein the coupling socket (302) has an inner and an outer pipe section (333, 330) as well as a second connecting flange (324) and is connected to the second cryogenic line (304), - wherein the outer pipe section (330) of the coupling socket (302) is welded onto the second connecting flange (324) and the end of the outer pipe section (330) remote from the connecting flange (324) is connected in a vacuum-tight manner to one end of the inner pipe section (333) of the coupling socket by means of a connecting ring (332), - wherein between the inner and the outer pipe section (333, 330) of the coupling socket (302) an annular gap (339) open in the area of the second connecting flange (324) is formed, which is surrounded both on its inner circumference as well as its outer circumference by an insulating vacuum (338, 341), characterized in that the other end of the inner pipe section (333) is welded onto a seal holder (334), that the media-conducting inner pipe (336) of the second cryogenic line (304) is welded onto the seal holder (334) and that the seal holder (334) carries a seal (342), which is in contact with the coupling plug (301) in the assembled state of the plug-in coupling (300) and seals the media-conducting inner pipe (307, 336) of the first or second cryogenic line (303, 304).

2. A plug-in coupling according to claim 1, characterized in that the coupling plug (301) is inserted into the open annular gap (339) when the plug-in coupling (300) is assembled.

3. A plug-in coupling according to claim 1 or 2 characterized in that the outer and the inner pipe section (317, 318) of the coupling plug (301) are in each case connected at a first end to the first connecting flange (309) and are connected at the respective second end to a connecting ring (321), wherein between the inner and the outer pipe section, an annular gap is formed, in which an insulating vacuum prevails.

4. A plug-in coupling according to claim 3, characterized in that the annular gap is connected via at least one flow channel (322) to an insulating vacuum in the first cryogenic line (303).

5. A plug-in coupling according to any one of the preceding claims, characterized in that the second connecting flange (324) is connected to an outer pipe (329) of the second cryogenic line (304).

6. A plug-in coupling according to any one of the preceding claims, characterized in that the inner pipe section (333) is connected to the outer pipe section (330) of the coupling socket (302) by means of a connecting ring (332).

7. A plug-in coupling according to any one of the preceding claims, characterized in that the coupling socket (302) and the coupling plug (301) have complementary centering means (344, 346).

8. A plug-in coupling according to any one of the preceding claims, characterized in that the inner pipes (307, 336) of the first and second cryogenic line (303, 304) are thermally insulated in the area of the plug connection from the outside by three insulating vacuums layered on top of each other.

9. A loading device for cryogenic fluids with a plug-in coupling (300) according to any one of claims 1 to 8.