KRYOGENER TANK

Description

[0001] The invention relates to a cryogenic tank.

[0002] The invention relates more particularly to a cryogenic tank, in particular for the transport of cryogenic fluid, for example liquefied hydrogen or helium, comprising an internal envelope made of metallic or alloy material and intended to contain the cryogenic fluid, an external envelope made of metallic or alloy material and arranged around the internal envelope and delimiting a spacing between the two envelopes, said spacing being under vacuum, the external envelope extending in a longitudinal direction and comprising a plurality of reinforcing ribs distributed in planes perpendicular to the longitudinal direction, the ribs being formed by deformations, for example by knurling, of the same wall of the external envelope, an example of which is disclosed in document US 2018 / 224064.

[0003] Cryogenic tanks typically use a vacuum-insulated double-jacket structure to ensure storage autonomy when transporting cryogenic liquid.

[0004] These metal or alloy casings are made by boilermaking and are therefore subject to boilermaking construction codes (e.g. ASME VIII). These casings must withstand external pressure due to their vacuum and must not impact the mass of the tank (or container that houses it).

[0005] Vacuum tanks are primarily designed to withstand external pressure. This mechanical resistance is ensured by a suitable shell thickness (welded sheet metal forming the cylindrical shell) and / or stiffening elements.

[0006] In the case of transportable tanks made of metallic material, mass optimization is an important issue; the solution of thickening the shell wall does not allow for achieving a suitable tank mass. One solution would be to use metallic materials such as aluminum alloy, but the low Young's modulus of this material requires increasing the thickness.

[0007] A known solution therefore consists of adding stiffening (ribs) to the wall: either by adding rings: either welded or formed by deformation of the ferrule in order to stiffen it (knurling for example).

[0008] Welded ring reinforcement can pose space problems, and these rings must go all the way around the shell to ensure their effectiveness. These rings are generally thicker than the shell and add mass to the equipment.

[0009] Reinforcement by ribs formed by deformation of the sheet metal (knurling process) does not add any mass to the tank but causes problems of low axial stiffness of the casing ("accordion" effect). This effect is even more marked on aluminum casings.

[0010] An aim of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

[0011] To this end, the tank according to the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that the tank further comprises at least one element for reinforcing at least part of at least one of the ribs, the reinforcing element comprising a strip rigidly connected at the level of the two portions of the wall located at the base and on either side of the rib.

[0012] Furthermore, embodiments of the invention may include one or more of the following features: the strip is made of metallic material or alloy and is welded to the outer casing, the ribs extend over all or part of the circumference of the outer casing, at least part of the ribs being provided with at least one strip, at least part of the ribs is provided with several discrete strips distributed over part of the circumference of the casing, for example three strips, the strips extend in a plane perpendicular to the longitudinal direction over 40 to 80 and preferably 50 to 70% of the circumference of the outer casing, the strip(s) have a width measured in a direction parallel to the longitudinal direction of between one and three times the width of the rib, the first casing and the second casing have a generally cylindrical shape of circular section and extending in the longitudinal direction and a circular section,the longitudinal axis being oriented horizontally in the transport or use configuration of the tank, the ribs protrude from the outer surface of the external casing.

[0013] The invention may also relate to any alternative device comprising any combination of the above or below characteristics within the scope of the claims. Other features and advantages will appear on reading the description below, made with reference to the figures in which: Brief description of the figures

[0014] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which: [ Fig. 1 ] is a perspective, schematic and partial view of an example of a tank according to the invention, [ Fig. 2 ] is a schematic and partial longitudinal sectional view of a detail of the tank, [ Fig. 3] is a schematic and partial perspective and sectional view of a detail of the tank. Detailed description

[0015] In all figures, the same references refer to the same elements.

[0016] In this detailed description, the following embodiments are examples. Although the description refers to one or more embodiments, this does not mean that the features apply only to a single embodiment. Single features of different embodiments may also be combined and / or interchanged to provide other embodiments.

[0017] Tank 1 shown is a cryogenic tank, for example for the storage and transport of cryogenic fluid, for example liquefied hydrogen or helium.

[0018] This tank 1 comprises an internal envelope 2 made of metallic or alloy material and intended to contain the cryogenic fluid. The tank 1 also comprises an external envelope 3 made of metallic or alloy material arranged around the internal envelope 2 and delimiting a space between the two envelopes 2, 3. This space is under vacuum and preferably contains a thermal insulator, for example of the multi-layer type (“MLI”).

[0019] The tank 1 and in particular the external envelope 3 extends in a longitudinal direction A.

[0020] As illustrated, the first casing 2 and the second casing 3 preferably have a generally cylindrical shape with a circular section which extends in the longitudinal direction A. That is to say that each casing has a central cylindrical portion formed by a sheet or shell whose ends are closed by respective domes.

[0021] Preferably, the longitudinal axis A is oriented horizontally in the transport or use configuration of the tank 1. The external casing 3 comprises a plurality of reinforcing ribs 4 distributed in planes perpendicular to the longitudinal direction A. The ribs 4 are formed by deformations, for example by knurling, of the same wall of the external casing 3 (central cylindrical portion).

[0022] As illustrated, these ribs 4 preferably protrude from the outer surface of the outer casing 3. Preferably, the ribs 4 are formed over the entire circumference of the outer casing 3. For example, the ribs 4 are formed on the cylindrical wall spaced apart along the longitudinal direction A by a distance of between 50 and 200 mm, for example of the order of 100 mm.

[0023] Preferably, the ribs 4 are distributed regularly along the longitudinal direction A on the cylindrical portion (shell), for example according to the following formula: d = L / (n+2) With: d = distance between two adjacent ribs, L = length of shell, n = number of ribs. The distance d can vary depending on the other assembly elements (such as, for example, the position of the feet on the tank) but preferably the distance d is constant between each rib to distribute the stiffness of the shell.

[0024] Thus, the ferrule (cylindrical portion of a part) comprises several ribs 4 obtained by mechanical deformation.

[0025] In addition, at least one and preferably all of the ribs 4 comprise at least one reinforcing element 5. The reinforcing element 5 comprises a strip 5, for example metallic or alloy, rigidly connected (fixed) at the two portions of the wall which are located at the base and on either side of the rib 4.

[0026] The strip 5 is preferably welded to the outer casing 3 on either side of the rib 4.

[0027] The ribs 4 extend in planes perpendicular to the longitudinal direction A over all or part of the circumference of the external envelope 3.

[0028] For example, one or more or all of the ribs 4 are provided with several discrete strips 5 distributed around the circumference of the casing 3, for example three strips 5. The strips are preferably distributed uniformly around the circumference of the tank 1.

[0029] For example, the strips 5 extend in a plane perpendicular to the longitudinal direction A over at least half of the circumference of the external envelope 3 (and are welded / fixed) therefore over at least half of the circumference of the envelope 3.

[0030] Preferably, the strip(s) 5 have a width L5 measured in a direction parallel to the longitudinal direction A of between one and three times the width L4 of the rib 4.

[0031] The proposed solution makes it possible to improve the axial stiffness of the tank 1 by limiting or preventing the accordion effect. These strips 5 can be fixed on the internal face of the external casing 3.

[0032] These strips 5 increase the axial rigidity of the tank 1 and, in addition, act as force transmission elements. The strips 5 are preferably composed of the same material as the casing 3 to be stiffened. They make it possible to maintain the vacuum resistance of the tank 1. In the case of forces passing through the support, the strips are preferably positioned at the right angle to the supports (tie rods / necks, etc.).

[0033] As described above, these strips 5 can be fixed only at certain locations of the external envelope 3 (it is in fact not necessary to provide this reinforcement 5 around the entire perimeter of each rib 4). This limits the impact on the total mass of the tank 1.

Claims

1. Cryogenic tank, in particular for transporting cryogenic fluid, for example liquefied helium or hydrogen, comprising an inner shell (2) made of a metal material or alloy and intended to contain the cryogenic fluid, an outer shell (3) made of a metal material or alloy, arranged around the inner shell (2) and delimiting a space between the two shells (2, 3), said space being under vacuum, the outer shell (3) extending in a longitudinal direction (A) and comprising a plurality of reinforcing ribs (4) distributed in planes that are perpendicular to the longitudinal direction (A), the ribs (4) being formed by deformations, for example by knurling, on one and the same wall of the outer shell (3), characterized in that the tank (1) also comprises at least one reinforcing element (5) for reinforcing at least part of at least one of the ribs (4), the reinforcing element (5) comprising a strip (5) rigidly connected to the two portions of the wall situated at the base and on either side of the rib (4).

2. Tank according to Claim 1, characterized in that the strip (5) is made of a metal material or alloy and is welded to the outer shell (3).

3. Tank according to Claim 1 or 2, characterized in that the ribs (4) extend over all or part of the circumference of the outer shell (3) and in that at least part of the ribs (4) is provided with at least one strip (5).

4. Tank according to any one of Claims 1 to 3, characterized in that at least part of the ribs (4) is provided with a plurality of discrete strips (5) distributed over part of the circumference of the shell (3), for example three strips (5).

5. Tank according to Claim 4, characterized in that said strips (5) extend in a plane that is perpendicular to the longitudinal direction (A) over 40 to 80%, and preferably 50 to 70%, of the circumference of the outer shell (3).

6. Tank according to any one of Claims 1 to 5, characterized in that the one or more strips (5) have a width (L5), measured in a direction that is parallel to the longitudinal direction (A), of between one and three times the width (L4) of the rib (4).

7. Tank according to any one of Claims 1 to 6, characterized in that the first shell (2) and the second shell (3) have a cylindrical general shape with a circular cross section and extending in the longitudinal direction (A) and a circular cross section, the longitudinal axis (A) being oriented horizontally when the tank (1) is in the transport or use configuration.

8. Tank according to any one of Claims 1 to 7, characterized in that the ribs (4) protrude from the exterior surface of the outer shell (3).