Cryogenic fluid storage tank

Abstract

The invention relates to a cryogenic fluid storage tank comprising a sealed inner casing (2) delimiting the storage volume for the cryogenic fluid and a sealed outer casing (3) arranged around the inner casing (2) with a thermally insulated spacing, the inner casing (2) being connected to the outer casing (3) via at least one tubular neck (4) extending in a longitudinal direction, the neck (4) having, in the longitudinal direction, a portion (5) of relatively thinned thickness. Abstract figure: Fig. 1

Description

Title of the invention: Cryogenic fluid storage tank

[0001] The invention relates to a cryogenic fluid storage tank.

[0002] The invention relates more particularly to a cryogenic fluid storage tank comprising a sealed internal envelope delimiting the storage volume for the cryogenic fluid and a sealed external envelope arranged around the internal envelope with a thermally insulated spacing, the internal envelope being connected to the external envelope via at least one tubular neck extending in a longitudinal direction.

[0003] It is known to provide cryogenic tanks having one or more tubular necks made of more or less conductive materials. The internal envelope can also be held in the external envelope via a set of tie rods or any other arrangement.

[0004] Such tanks must satisfy mechanical constraints of mechanical strength while limiting thermal inputs.

[0005] An aim of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

[0006] To this end, the reservoir according to the invention, moreover conforming to the generic definition given in the preamble above, is essentially characterized in that the neck has, in the longitudinal direction, a portion of relatively thinned thickness.

[0007] Furthermore, embodiments of the invention may include one or more of the following features: - the internal diameter of the neck is constant, the portion of thickness relatively thinned in the longitudinal direction being formed by a variation in the external diameter of the neck, - the portion of relatively thinned thickness is formed by a progressive reduction in the thickness of the neck in the longitudinal direction, - the progressive reduction in the thickness of the neck in the longitudinal direction is between 0.5 and 2mm of thinning for a progression of 100mm in the longitudinal direction, - the neck has a thickness of between 0.5 and 5 mm and preferably between 1 and 3 mm, the thinned portion having a thickness reduced by 5% to 70% compared to the unthinned thickness, - the neck is of the fixed type, the two longitudinal ends of which are rigidly connected to fixed points located respectively at the level of the internal envelope and at the level of the external envelope, the portion of relative thickness tively thinned being located between the two longitudinal ends of the neck, for example in the middle part of the neck, - the neck is of the movable type and has a first longitudinal end rigidly connected to a fixed point, for example the external envelope and a second longitudinal end connected to a point having freedom of movement, for example the internal envelope, the portion of relatively thinned thickness being located at the level of the second longitudinal end, - the tank has two necks located respectively at two ends of the tank, - the internal envelope and / or the external envelope is made of at least one of: carbon steel, stainless steel, aluminum, titanium, - the neck is made of at least one of: carbon steel, stainless steel, aluminum, titanium.

[0008] The invention may also relate to any alternative device or method comprising any combination of the above or below features within the scope of the claims.

[0009] Other features and advantages will appear on reading the description below, given with reference to the figures in which: Brief description of the figures

[0010] 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:

[0011] [Fig-1] is a schematic view in longitudinal section of an example of a tank according to an exemplary embodiment of the invention,

[0012] [Fig.2] a schematic sectional view of a first example of a tubular neck according to the invention,

[0013] [Fig.3] a schematic sectional view of a second example of a tubular neck according to the invention. Detailed description

[0014] In all the figures, the same references refer to the same elements.

[0015] In this detailed description, the following embodiments are examples. that 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.

[0016] The illustrated cryogenic fluid storage tank 1 comprises a sealed internal casing 2, for example of generally cylindrical shape, delimiting the storage volume for the cryogenic fluid. The tank 1 further comprises a casing 3 outer sealed jacket disposed around the inner jacket 2 with a thermally insulated spacing. For example, the spacing between the outer jacket 3 and the inner jacket 2 is vacuum and contains a multi-layer insulation (“MLI”).

[0017] The internal envelope 2 and / or the external envelope 3 may be made of at least one of the materials among: carbon steel, stainless steel, aluminum, titanium.

[0018] The inner casing 2 is mounted (or supported) in the outer casing 3 via at least one tubular neck 4 (two necks 4 in this example). The necks 4 extend in a longitudinal direction (horizontal in the configuration of [Fig.l]).

[0019] The neck 4 may be made of at least one of the materials among: carbon steel, stainless steel, aluminum, titanium, composite material.

[0020] According to an advantageous feature, at least one of the necks 4 has, in the longitudinal direction, a portion 5 of relatively thinned or reduced thickness.

[0021] The inventors have in fact found that the thickness of the neck(s) 4 can be reduced locally, particularly in areas subject to less mechanical stress, without harming the mechanical strength of the tank and its thermal performance.

[0022] The relative reduction in thickness also reduces heat transfer by conduction.

[0023] The correlation between the variation in thickness and the thermal gain is difficult to detail because the thickness of a neck is a quantity dependent on various parameters, such as its diameter, itself dependent on the diameter of the tank, the weight of the latter or even the load cases to which it is subjected. However, a thermal gain of 30 to 40% can in particular be achieved via this localized reduction in the thickness of the neck.

[0024] This thermal gain of up to 30 to 40% can be achieved in particular for a tank with a diameter of less than 1 m allowing a neck with a diameter of less than 200 mm, for an internal tank mass of less than 500 kg subjected to relatively low load cases (corresponding for example to static use of the tank: for example at most a force of 4 g in the 3 directions x, y, z).

[0025] As illustrated in [Fig.l] and [Fig.2], the internal diameter of the neck 4 can be constant along its length, the portion 5 of relatively thinned thickness in the longitudinal direction being formed by a variation in the external diameter of the neck 4. This makes it possible to maintain cylindrical guidance in the internal part and facilitates the machining of the neck.

[0026] Preferably, the localized reduction in thickness is formed by a progressive (continuous) reduction in the thickness of the neck 4 in the longitudinal direction.

[0027] For example, the progressive reduction in the thickness of the neck 4 in the longitudinal direction can be between 0.5 and 2 mm of thinning for a progression of 100 mm in the longitudinal direction, for example 1 mm less thickness every 100 mm. This limits the stress concentrations at the level of the changes in thickness.

[0028] The neck(s) 4 have for example a thickness of between 0.5 and 5 mm and preferably between 1 and 3 mm, the thinned portion 5 having for example a thickness reduced by 5% to 70% compared to the non-thinned thickness.

[0029] For example, the thickness of the neck 4 in the unthinned portion may be 3mm while the smallest thinned thickness may be of the order of 1mm.

[0030] The neck 4 (when the tank has a single neck) or at least one of the two necks (when the tank has two necks as shown) may be of the fixed type, i.e. the two longitudinal ends of which are rigidly connected to fixed points located respectively at the level of the internal envelope 2 and at the level of the external envelope 3. In this case, the portion 5 of relatively thinned thickness is preferably located between the two longitudinal ends of the neck 4, for example in the middle part of the neck 4 cf. [Fig.2].

[0031] Indeed, for a fixed neck 4, the tube is constrained in displacement and rotation at its two longitudinal ends. The distribution of the stresses is therefore symmetrical over the length. If we only consider half of the tube (in the length) we can easily assimilate it to a beam in bending. The stress concentration is therefore greater near the ends. A greater thickness is therefore necessary at the ends of the neck with a reduction in thickness symmetrically over the length of the neck

[0032] The neck or one of the necks may be of the movable type, that is to say may have a first longitudinal end rigidly connected to a fixed point, for example the external casing 3 and a second longitudinal end connected to a point having freedom of movement, for example the internal casing 2, to allow relative movement to absorb thermal expansions for example. In this case, the portion 5 of relatively thinned thickness is preferably located at the level of the second longitudinal (movable) end cf. [Fig.3].

[0033] Indeed, a movable neck 4 is constrained in displacement and rotation at a single longitudinal end. It can therefore also be likened to a beam in bending but over its entire length. The zone where the constraint is the least important is therefore its free end, which will therefore be the zone with the smallest thickness. The reduction in thickness is preferably carried out continuously over the length.

[0034] The inventors have determined that the distribution of mechanical stresses is non-uniform over the length of the neck 4, the parts in the vicinity of the mechanically "blocked" zones being subjected to greater stress than the parts which are far from them.

[0035] The neck(s) 4 may be manufactured using several known manufacturing methods depending on the dimensions of the neck, in particular its diameter, its length and the thickness reduction to be achieved: for example by machining, spinning or hydroforming.

[0036] Although the illustrated embodiment relates to a tank 1 arranged horizontally in the usage configuration (horizontal longitudinal axis), the invention can also be applied to vertical tanks (neck for example arranged vertically at the upper end).

Claims

Claims

1. Cryogenic fluid storage tank comprising a sealed inner casing (2) delimiting the storage volume for the cryogenic fluid and a sealed outer casing (3) arranged around the inner casing (2) with a thermally insulated spacing, the inner casing (2) being connected to the outer casing (3) via at least one tubular neck (4) extending in a longitudinal direction, characterized in that the neck (4) has, in the longitudinal direction, a portion (5) of relatively thinned thickness, characterized in that the portion (5) of relatively thinned thickness is formed by a progressive and continuous reduction in the thickness of the neck (4) in the longitudinal direction.

2. Tank according to claim 1, characterized in that the internal diameter of the neck (4) is constant, the portion (5) of relatively thinned thickness in the longitudinal direction being formed by a variation in the external diameter of the neck (4).

3. Tank according to claim 1 or 2, characterized in that the progressive reduction in the thickness of the neck (4) in the longitudinal direction is between 0.5 and 2 mm of thinning for a progression of 100 mm in the longitudinal direction.

4. Tank according to any one of claims 1 to 3, characterized in that the neck (4) has a thickness of between 0.5 and 5 mm and preferably between 1 and 3 mm, the thinned portion (5) having a thickness reduced by 5% to 70% compared to the unthinned thickness.

5. Tank according to any one of claims 1 to 4, characterized in that the neck (4) is of the fixed type whose two longitudinal ends are rigidly connected to fixed points located respectively at the level of the internal envelope (2) and at the level of the external envelope (3), and in that the portion (5) of relatively thinned thickness is located between the two longitudinal ends of the neck (4), for example in the middle part of the neck (4).

6. Tank according to any one of claims 1 to 5, characterized in that the neck (4) is of the movable type and has a first longitudinal end rigidly connected to a fixed point, for example the external envelope (3) and a second longitudinal end connected to a point having freedom of movement, for example the internal envelope (2), and in that the portion (5) of relatively thinned thickness is located at the second longitudinal end.

7. Tank according to any one of claims 1 to 6, characterized in that it comprises two necks (4) located respectively at two ends of the tank (1).

8. Tank according to any one of claims 1 to 7, characterized in that the internal casing (2) and / or the external casing is made of at least one of: carbon steel, stainless steel, aluminum, titanium.

9. Tank according to any one of claims 1 to 8, characterized in that the neck (4) is made of at least one of: carbon steel, stainless steel, aluminum, titanium.

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