WO2022263481A1

WO2022263481A1 - An improved membrane plate for a membrane cargo tank

Info

Publication number: WO2022263481A1
Application number: PCT/EP2022/066245
Authority: WO
Inventors: Erlend Langsrud
Original assignee: Ic Technology As
Priority date: 2021-06-14
Filing date: 2022-06-14
Publication date: 2022-12-22

Abstract

The present invention is related to a membrane plate that can be utilized in a membrane cargo tank. The membrane plate as a corrugation pattern arranged in a zigzag pattern across a surface of the membrane plate. Thermal forces can be mitigated in two dimensions due to the folding properties of the corrugated membrane plate. The membrane plate is substantially planar and comprises a corrugation pattern created by a plurality of zigzag shaped protrusions running in parallel across a surface of the membrane plate from a first edge of the membrane plate to an opposing second edge of the surface. The plurality of the zigzag shaped protrusions is arranged such that an increase or decrease in a first in-plane dimension of the membrane plate results in a respective increase or decrease of a second in-plane dimension of the membrane plate, the second dimension being orthogonal to the first dimension.

Description

AN IMPROVED MEMBRANE PLATE FOR A MEMBRANE CARGO TANK

The present invention in one of its aspects is related to a membrane cargo tank system comprising at least one membrane plate comprising a corrugation pattern providing compensation of thermal induced contraction and expansion of the membrane in two dimensions, and a membrane plate therefor.

BACKGROUND OF THE INVENTION

Membrane tanks are a well-known principle used for transport of liquified gases like liquid natural gas (LNG) and liquid hydrogen (LH) onboard ships.

A typical membrane tank is not a self-supported cargo tank structure. Parts of the structure of the membrane tank may be the ship hull itself. Common designs may comprise a double hull ship structure being part of a sandwich construction comprising a thin layer of metal denoted the primary membrane followed by insulation materials, a secondary membrane barrier and further insulation materials.

A challenge regarding membrane tanks is the effect of thermal expansion and thermal contraction of for example a steel membrane. The technical problem is to compensate for thermal expansions and respective thermal contractions while mitigating stressing of the membrane, which may weaken the mechanical integrity of the membrane over time.

Further problems may be related to sloshing of liquid gasses inside the storage space of a storage tank on board a ship traveling in harsh weather conditions. The impact of stored liquid gases being thrown onto the internal membrane surface, i.e., sloshing, requires a strong mechanical membrane system preventing rupture of the tank wall.

When it comes to transporting hydrogen, liquified hydrogen (LH) has some unique properties that differs substantially from other liquids. One issue is for example the swelling phenomenon. The high energy content of LH makes it also necessary with security systems, for example monitoring of possible leakage from a cargo tank.

All the above problems and other issues should be solved when providing a safe transport system of liquid gasses like hydrogen on ships. Onshore storage tanks for LH shares some of the same issues as for cargo tanks on ships. Onshore membrane tanks may for example have a concrete outer shell serving the same purpose for the tank structure as the ship hull does for membrane tanks on board ships

RU 2588920 C2 disclose a storage and transportation tank for liquefied natural gas. The tank (71) comprises a heat insulation comprising multiple adjacent insulating units (28) supported by a structure, and a seal, which includes multiple sealing metal sheets (25) located on the insulating units (28) and welded to each other. Mechanical connection elements (11) pass through the heat insulation at a level of edges of the insulating units (28).

EP 3662195 A1 disclose a Liquid Natural Storage (LNG) tank comprising an outer mechanical support structure (20) providing a closed space housing a membrane wall of the cryogenic tank, wherein spacer elements (21) support the membrane wall made of a mixture of steel plates, steel rods, wooden beams, and plywood plates. The membrane itself comprises a first corrugated steel plate welded to a second corrugated steel plate.

US 5,292,027 describes a liner for a primary vessel comprising sheets of membrane material having a herringbone pattern of repetitive parallelogram-like elements.

Steel plates used in membrane cargo tanks are supported by a support structure and are welded together forming a leakage free membrane. When two steel plates are welded together, they are mechanically stiffer compared to each separate steel plate. This influences how stress due to thermal induces forces act on the membrane plates. It is also significant how the geometrical shape of the cargo tank is made. For example, a cylinder shaped tank has some advantages with respect to thermal induced forces since any thermal induced expansion or reduction of a surface section of a membrane of the cylinder may result in a change of radius of the cylinder, which may result in a distribution of the change across the whole circumference of the cylinder. However, installing a cylinder-shaped tank inside a hull of a ship is not optimal with respect of utilizing as much as possible of available space inside the hull of the ship.

More box like or square like geometries of a cargo tank makes it easier to utilize the available capacity of a ship hull. In such circumstances a membrane section will be arranged orthogonal to another when joined into a box design. This may make the membrane stiffer even if there are corrugations present on the membrane surface.

Therefore, there is a need for an improved membrane tank design.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an alternative to the prior art.

In particular, it may be seen as an object of the present invention to provide a cargo tank membrane comprising a corrugation pattern compensating thermal induced forces in two dimensions.

Thus, the above-described object and several other objects are intended to be obtained in a first aspect of the invention by providing a membrane plate with a corrugation pattern having some of the same properties as of a Miura-Ori folding pattern. Such properties may be a negative Poisson ratio and/or may be auxetic structures.

According to a first aspect of the invention, there is provided a membrane plate (10) for a membrane cargo tank providing transport or storage of a cryogenic fluid such as liquified hydrogen (LH), wherein the membrane plate (10) is substantially planar and comprises a corrugation pattern created by a plurality of zigzag shaped protrusions (14) running in parallel across a surface of the membrane plate from a first edge of the membrane plate to an opposing second edge of the surface, wherein the plurality of the zigzag shaped protrusions is arranged such that an increase or decrease in a first in-plane dimension of the membrane plate results in a respective increase or decrease of a second in-plane dimension of the membrane plate, the second dimension being orthogonal to the first dimension.

According to a second aspect of the invention, there is provided a membrane cargo tank comprising at least one membrane plate according to the first aspect of the invention.

According to a third aspect of the invention, there is provided a membrane tank assembly comprising the membrane tank of the second aspect of the invention, and an outer support structure arranged on an outside of the membrane tank. The invention is particularly, but not exclusively, advantageous for obtaining a membrane plate of a membrane cargo tank providing transport or storage of liquified hydrogen, wherein the membrane plate (10) comprises a corrugation pattern created by a plurality of zigzag shaped protrusion (14) running in parallel across a surface of the membrane plate from one end of a surface of the membrane plate to an opposite located end of the surface, wherein the respective plurality of the zigzag shaped protrusions is arranged with an equal distance in between them.

The membrane plate may comprise two membrane plates spot welded together such that a space in between the two membrane plates is created by the zigzag shaped protrusions facing away from each other on each respective membrane plate.

The membrane plate may be rectangular shaped and may comprise: an end area on a first side of the rectangular shaped membrane plate is arranged with a first corrugation pattern, a second end area on a second end of the rectangular shaped membrane plate is arranged with a second corrugation pattern, an end area of a third side of the rectangular shaped membrane plate running in parallel with the fist side is arranged with the first corrugation pattern, an end area of a fourth side of the rectangular shaped membrane plate running in parallel with the second side is arranged with the second corrugation pattern.

According to an aspect of the invention, a membrane cargo tank may comprise at least one membrane plate according to a previous aspect. The membrane cargo tank may comprise a first membrane plate joinable to a second membrane plate via a half cylinder shaped member, wherein a first longitudinal side end surface of the half cylinder shaped member is connected to a first end side of the membrane plate having the first corrugation pattern while a second longitudinal end surface of the half cylinder shaped member is connected to the second membrane plate on a second end of the second membrane plate having the second corrugation pattern.

The half cylinder shaped member may be arranged with straight parallel running protrusions on an outside surface, wherein the parallel protrusions are orthogonal to a height direction of the half cylinder shaped member, wherein the number of parallel running protrusions equals the number of parallel running zigzag protrusions on the membrane plate, and the distance between the parallel running protrusions on the half cylinder shaped member surface equals the distance between the parallel running zigzag protrusions on the membrane plate.

The membrane cargo tank may comprise a bracket with a first side surface is arranged orthogonal to a second side surface, wherein a plurality of protruding fingers is arranged on each respective first and second side surface of the bracket, wherein the bracket is mountable across the half cylinder shaped member on an outside of the half cylinder shaped member.

Optionally, the protruding fingers on the first side surface is connected to a first membrane plate while the protruding fingers on the second side surface is connected to a second membrane plate joined to the first membrane plate via the half cylinder shaped member.

Optionally, a number of protruding fingers on the first and second side surfaces equals the number of parallel zigzag protrusions on the membrane plate, and the distance between the respective fingers equals the distance between the respective zigzag protrusions.

Optionally, the direction of the parallel zigzag protrusions on the first membrane plate is arranged orthogonal to the direction of the zigzag protrusions on the second membrane plate when they are joined together via the half cylinder shaped membrane.

Optionally, the direction of the parallel zigzag protrusions on the first membrane plate is arranged in a same direction to as the zigzag protrusions on the second membrane plate when they are joined together via the half cylinder shaped membrane.

Optionally, the membrane plate is a double plated membrane, wherein a space in between the two membranes plate is circulated with a cooling agent capable of cooling LH that is deposit-able into the membrane tank to be cooled to a temperature below -253 degrees Celsius.

Optionally, an outer support structure of plywood is arranged on an outside of the membrane tank. Optionally, a second membrane is arranged as part of the plywood support structure, wherein the second membrane comprises horizontal and vertical indents crossing each other on a surface of the second membrane and thereby creating a rectangular shaped pattern on the surface of the second membrane, wherein a cup shaped indent is arranged in all crossing points between the horizontal and vertical running indents on the surface of the second membrane.

Optionally, a plurality of distal rods are arranged in between the membrane tank and the plywood support structure thereby creating an empty space in between the membrane of the membrane tank and the plywood support structure.

Optionally, the created empty space is used for insulation purposes.

Respective aspects of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be disclosed and elucidated with reference to the embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which:

Figure 1 disclose an example of an embodiment of the present invention.

Figure 2 illustrates a principle of a corrugation pattern used in the example illustrated in Figure 1.

Figure 3 illustrates a perspective view of the example of embodiment illustrated in Figure 1. Figure 4 illustrates an example of assembling an embodiment of the present invention. Figure 5 illustrates a further assembling of the example illustrated in Figure 4.

Figure 6 illustrates a further assembling of the example illustrated in Figure 5. Figure 7 illustrates a perspective view of an example of embodiment of the present invention.

Figure 8 illustrates another example of embodiment of the present invention.

Figure 9 illustrates an exploded perspective view of an example of embodiment of the present invention.

Figure 10 depicts the example of embodiment illustrated in Figure 9 seen from a different view angle.

Figure 11 illustrates another example of embodiment of the present invention.

Figure 12 illustrates another example of embodiment of the present invention.

Figure 13A is a representation of a part of a membrane tank wall according an embodiment of the invention.

Figure 13B is an enlarged view of a part of the membrane tank wall of Figure 13A.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Although the present invention is disclosed in connection with specific examples of embodiments, it should not be construed as being in any way limited to the presented examples. The accompanying claim set defines the scope of protection of the present invention. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Further, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention.

Furthermore, combining individual features mentioned in different claims may possibly be advantageous, and the mentioning of these features in different claims does not preclude that combinations of those features may be possible and advantageous. Figure 1 illustrates an example of a membrane plate 10 according to an embodiment of the present invention. In this example the membrane plate is rectangular flat plate with a special corrugation pattern.

The corrugation pattern illustrated in Figure 1 is a pattern which stems from a known origami technique called Miura-Ori folding.

Figure 2 illustrates an example of a Miura-Ori folding of a sheet of paper. An unfolded sheet of paper can be folded such that a series of rectangles are created by the folding lines. Folding lines following for example vertical lines 15, 16 and then in a horizontal direction following for example the lines 20, 20a. The stippled lines 17a, 17b represent folding lines when pushing the sheet of paper together or is stretching the paper in a direction of the width of the paper. The folding lines 19a, 19b represent folding lines when the sheet of paper is pushed together or is stretched in a direction along the height of the sheet of paper. This pattern allows a two-dimensional folding and stretching of the sheet of paper. When folded in both directions, the sheet of paper will be less in area in two dimensions since parts of the paper surface along the line 15 16 will protrude upwards like a mountain ridge while the folding lines 20, 20a will form valleys between the protruding parts of the sheet of paper.

The Miura-Ori fold has the property that when expanded in a longitudinal direction of the plane of the sheet, the sheet expands in a transverse direction (i.e. orthogonally to the longitudinal direction). Similarly, when contracted in a longitudinal direction of the plane of the sheet, the sheet contracts in a transverse direction. In other words, the sheet has a negative Poisson ratio, or is an auxetic structure, meaning that when stretched, the dimension in a direction perpendicular to the applied force also increases.

With reference to Figure 1 , the corrugation pattern has a protruding corrugation in a form like a mountain ridge 13a following a zigzag pattern across the surface of the membrane plate in the x-direction. On both sides of the zigzag shaped protrusions there are indents 13b, 13b forming valleys following the zigzag shaped protrusion 13a. Transition portions 14 between the ridges 13a and valleys 13b slope from the ridges to the valleys in the y- direction. This corrugation configuration has similar folding properties as discussed with respect to Figure 2. In particular, when the length of the plate 10 increases in length in the y- direction, the width of the plate also increases in the x-direction. Therefore, the corrugation pattern illustrated in Figure 1 provides a two-dimensional compensation of thermal induced forces.

The zigzag shapes are continuous across the plate and comprise straight portions 115a, 115b, separated by curved portions 116a, 116b, which reverse the direction of the zigzag in a smooth and continuous manner without a discontinuity that would be caused by a sharp corner, fold or change in direction. In this embodiment, the angle between the straight portions 115a, 115b is 90 degrees, but other angles (and therefore non-equal angles) may be selected according to material properties, expected thermal cycling, and resulting anticipated stresses amongst other factors. Alternatively, or in addition, the radius of curvature of the curved portions 116a, 116b, and/or the spacing between the zigzag protrusions, may be selected according to material properties, expected thermal cycling, and resulting anticipated stresses amongst other factors.

Figure 1 illustrates further that the example of membrane plate 10 is arranged with edge areas with special corrugation patterns. The corrugation pattern 12a arranged on a first side 10w of the membrane plate 10 corresponds to a corrugation pattern 12b arranged on an opposite second side 10x of the membrane plate 10 running in paralell with the first side 10w.

On an edge area of a third side 10y of the membrane plate 10 there is a special corrugation pattern 12c which is also arranged on an edge area on a fourth opposite located side 10z of the membrane plate 10 (see reference numeral 12d). The edge area of the fourth side 10z runs in parallel with the edge surface of the third side 10y.

Further corrugation patterns 11a, 11b, 11c, 11 d are arranged in corner areas of the membrane plate 10.

The special corrugation patterns in the edge areas of the membrane plate 10 are arranged to facilitate connections of elements that bind for example two membrane plates as disclosed in Figure 1 together. An effect of the two-dimensional corrugation pattern is that the surface area of a membrane plate like the one illustrated in Figure 1 may increase or decrease from an initial state related to a relaxed state (for example defined at room temperature). This area change will induce stresses in a membrane. Therefore, there are some special elements according to embodiments of the present invention that may be used when interconnecting for example respective side walls, bottom sections, corner sections etc. and roof sections of a complete cargo tank according to embodiments of the present invention.

For example, if two adjacent membrane plates 10 are welded together orthogonal to each other, the welded joining line would make both membrane plates stiffer and would experience increased stress when a respective surface area of one of the two membrane plates changes due to thermal induced forces, for example.

Figure 3 is a perspective view of the example of membrane plate 10 illustrated in Figure 1.

The membrane plate 10 illustrated in Figure 1 and 3 is an example of a membrane plate 10 used when assembling a membrane tank according to the present invention.

Figure 4 illustrates how a first membrane plate 10a can be arranged to be connected to a second membrane plate 10b. The membrane plate 10a is oriented orthogonal to the membrane plate 10b. The joining of the respective membrane plates is done via a part- cylinder shaped member 21. Figure 7 provides a fuller view of the arrangement.

The part-cylinder shaped member 21 is a quarter-cylinder, so that the orientation planes of membrane plates 10a, 10b joined by the part-cylinder shaped member are perpendicular to one another.

The part-cylinder shaped member 21 has a corrugation pattern comprising parallel protrusions running in a direction around the surface of the part-cylinder shaped member 21. The two straight end surfaces (see reference numerals 21a, 21b of Figure 7) of the part- cylinder shaped member 21 are respectively welded to the first membrane plate 10a and the second membrane plate 10b.

In addition, a right-angled bracket 22 is arranged on the outside of the part-cylinder shaped member 21. The right-angled bracket 22 (Figure 4) is arranged with a set of finger-like protrusions 23 that are welded respectively to the membrane plate 0a on a first side of the bracket 22 and to the membrane plate 10b on a second side of the bracket 22. The fingers 23 on the first side of the bracket 22 are illustrated welded to the corrugations on for example the edge area on the fourth side 10z of the membrane plate 10a as illustrated in Figure 1. The fingers on the second side of the bracket 22 is welded to for example the corrugations on the end area 10w on the membrane plate 10b.

An aspect of the finger arrangement of the bracket 22 is that the fingers do not influence (or do not substantially influence) the stiffness of the respective connected membrane plates. However, the bracket 22 increases the mechanical stability of the part-cylinder shaped member 21 bridging two adjacent membrane plates 10a, 10b. In-plane forces induced in the membrane plates 10 are transferred to the brackets 22 and transferred to a support structure (not shown) as will be described below.

It is also a feature of the part-cylinder shaped member 21 that any dimensional change of an attached membrane plate 10, due to thermal induced forces, may for example reduce or increase the opening of the open side of the part-cylinder member, while the parallel protrusions on the closed side of the part-cylinder member 21 will mitigate any length increase or decrease due to thermal induced forces.

In this regard, the curvature of the part-cylinder shaped member enables it to flex about an axis parallel to the cylinder axis, so that the opening defined by the respective parallel edges 21a and 21b is able to open or close due to the effect of thermally induced expansion or contraction forces from attached membrane plates, when those forces have a component in a direction perpendicular to the edges 21a and 21b.

In addition, the parallel protrusions formed by the corrugations oriented circumferentially on the part-cylinder shaped member in-planes perpendicular to the cylinder axis enable expansion and contraction of the part-cylinder member in the direction of the cylinder axis, due to the effect of thermally induced expansion or contraction forces from attached membrane plates, when those forces have a component in a direction parallel to the edges 21a and 21b. Thus the part-cylindrical shaped member is able to stretch and contract along its length, and flex about its axis.

Figure 5 illustrates an example of assembly of three different membrane plates 10a, 10b and 10c. The principles of the assembly are as discussed above with reference to Figure 4. The plates 10a and 10b are joined by a part-cylindrical member 21 ab, the plates 10a and 10c are joined by a part-cylindrical member 21ac, and the plates 10b and 10c are joined by a part-cylindrical member 21 be. Brackets 22a and 22b are associated with part- cylinder members 21 ac and 21 be respectively.

An aspect of the arrangement disclosed in Figure 4 and Figure 5 is that the direction of the zigzag protrusions on two connected membrane plates may be orthogonal to each other. This aspect is more clearly illustrated in Figure 5 and in Figure 6.

In another example of embodiment of the present invention, the zigzag patterns on two joined membrane plates can have the same orientation, as shown in Figure 12.

When there is a thermal induced stretching of a membrane plate 10 in a direction along the direction of the zigzag protrusions, the width of the membrane plate 10, viewed in an orthogonal direction to the direction of the zigzag protrusions, will also increase. If a thermal induced stretching happens in a direction orthogonal to the direction of the zigzag protrusions, the membrane plate length will increase in a direction parallel to the direction of the zigzag protrusions.

With reference to Figure 6, a situation wherein for example membrane plate 10a is stretched, due to thermal induced forces, in a direction along the zigzag protrusions, the height of the membrane plane along the zigzag protrusion direction (i.e in direction y) increases, while the width of the membrane plate 10a, viewed in an orthogonal direction to the direction of the zigzag protrusions (i.e. the direction x), will also increase. In-plane forces due to the expansion of the membrane plate 10a may be transferred to the adjacent part-cylinder shaped member 21 ac, which is able to stretch and flex as described above, to mitigate stresses on the interface between the edges of the plates and the part-cylinder shaped members. In-plane forces are also transferred to the bracket 22c, and on to the support structure (described below). In this manner the protrusions (corrugations) will mitigate the effect of the thermal induced forces on respective membrane plates 10a, 10c.

In Figure 6 there is a third membrane plate 10d arranged as a roof on the membrane tank in the x-z plane. The direction of the zigzag protrusions on the membrane plate 10d is on one side oriented in the x-direction. This is orthogonal to the direction of the zigzag protrusions on the membrane plate 10a (the y-direction) connected along one edge via part- cylinder member 21 ad, and on another edge facing connected to the membrane plate 10c via part-cylinder member 21 cd, the zigzag protrusions of 10d are oriented in the x-direction orthogonal to the zigzag protrusions in the z-direction on the membrane plate 10c.

Figure 6 also depicts a corner member 24 which is shaped as a triangular cut out from a ball shaped element. In other words, the corner member 24 is a substantially triangular section of a surface of a sphere. The diameter of the ball is adapted to the radius of the part-cylinder shaped member 21. The three edges of the triangular shaped member 24 are therefore adapted to the (curved) end edges of the part-cylinder members 21 ac, 21 cd and 21ad facing the triangular shaped member 24. The outer surface of the triangular shaped member 24 has also arranged triangular shaped corrugations. The triangular-shaped corrugations have rounded apex shapes.

In Figure 6 there is a bracket 22c arranged over a part-cylinder shaped member 21 cd arranged between the membrane plates 10c and 10d. Another bracket 22d is arranged over a part-cylinder shaped number 21 ad arranged between the membrane plate 10a and 10d. The two part-cylinder shaped members 21 cd and 21ad meet in an upper corner located adjacent to a corner of the upper membrane plate 10d. With reference to Figure 1 , in such corners there are special corrugation patterns 11a, 11b, 11c and 11 d. The triangular shaped member 24 has a corner of the triangle shape that will be welded to such a special corrugation pattern, for example 11c as illustrated in Figure 6.

The triangular-shaped corrugations enable the corner member 24 to flex between the respective open edges of the corner member 24, and enable expansion and contraction of the corner member in directions between respective apexes and their opposing edges.

An aspect of the present invention is that the number of fingers 23 on both the first and second sides of a bracket 22 (not shown) corresponds to the number of parallel zigzag protrusions on a membrane plate the fingers are connected to. As illustrated in Figure 6, a respective finger of the fingers 23 on the first side of the bracket (not shown) may be connected to a top surface section of an end of a ridge 13a of a zigzag protrusion on a side 10w (defined by the corrugation pattern 12a, 12b shown in Figure 1). A respective finger of the finger on the second side of the bracket 22 may be connected to a top surface of a ridge protrusion of the corrugations arranged on a side 10y of the membrane plate 10. Figure 7 depicts the example in Figure 6 from another viewing angle and without the brackets 22 mounted. Figure 7 discloses a further aspect of the present invention.

Another aspect is that the number of parallel protrusions on the closed side of a part- cylinder shaped member 21 is equal to the number of zigzag protrusions on a surface of a membrane plate 10 the part-cylinder shaped member 21 is connected to. A first side end of the part-cylinder shaped member 21 may be connected to a side 10y of a membrane plate 10 while the opposite located side end surface of the part-cylinder shaped member 21 may be connected to a side 10z of a membrane plate 10, as illustrated in Figure 1 , Figure 6 and Figure 7.

Figure 8 illustrates details of an example of embodiment of the present invention. A membrane tank assembly 80 includes a membrane tank 10 and a structure 27, which may be made of plywood or another suitable material such as a polymer or a composite, can support a tank membrane wall as illustrated. In this example embodiment there are arranged a set of rods 26 on each of the surfaces of the membrane tank. These rods are at one end attached to the brackets 22 and at the opposite end to the plywood structure 27. In-plane forces from the membrane plates 10 are transferred to the support structure 27 via the brackets 22 and the rods 26.

Figure 9 depicts an exploded view of an example of a sandwiched membrane tank assembly design according to an embodiment of the present invention. A membrane plate 10 is attached to a surface of a plywood plate wherein distal elements 28 creates a space or void 36 between the membrane plate 10 and a second plywood plate 29. There is a cut out pattern on the plywood plate 29 which is adapted to a surface of a secondary membrane plate 30. The secondary membrane is arranged with a regular pattern of straight corrugations in a horizontal and vertical direction. In points where the horizontal and vertical corrugations intersect there is arranged a cup shaped corrugation 38.

The protruding cups 35 are facing inwards towards the surface of the plywood plate 29.

A final plywood plate 31 or outer is arranged with parallel distal elements 32 of plywood wherein an end surface of the distal elements is arranged with a metal bracket 33 enabling fastening of the sandwiched design to for example an inside surface of a ship hull. In an alternative embodiment, one or more plywood components may be substituted for another suitable material such as a polymer or a composite.

Figure 10 illustrates the same exploded sandwich design as illustrated in Figure 9 but viewed from a different angle.

Figure 11 illustrates a complete secondary membrane according to the present invention comprising corrugations made of indents 35 running in parallel in a direction and orthogonal in second direction orthogonal to the first direction.

Figure 12 illustrates components as detailed above of a membrane tank according to the present invention.

Another aspect of a membrane tank according to the present invention is that insulation can be arranged in different manners around assembled membrane plates 10. For example, the rectangular shaped voids in the plywood construction 27 can be made to support insulation materials. The space between the plywood construction 27 and the assembled membrane tank created by the distal rods 26 can also be used for insulation purposes. For example, the created space may be contain a vacuum that will insulate the membrane tank.

With reference to Figure 4 and Figure 5, it is illustrated that the membrane plate 10a and 10b may consist of two membrane plates 10 of Figure 1 that are welded together (for example by spot- welding) leaving a space 10i in between the two membrane plates created by the respective protrusions on the respective membrane plates.

In an example of embodiment of the present invention, this space 10i may be used to circulate a gas or liquid such as a cooling agent inside the membrane space created by the double plated membrane. This may be advantageous in some very low temperature applications, for example holding LH at a temperature below -253 degrees Celsius at atmospheric pressure.

Referring to Figures 13A and 13B, there is shown another example embodiment of the invention in which multiple membrane plates are joined together to form a membrane tank. Figure 13A shows four membrane plates 1310a to 1310d (together 1310), forming a part of a wall 1300 of a membrane tank. Each membrane plate 1310 is a double plated membrane formed from a pair of corresponding single membrane sheets joined together on their major surfaces. As with the previous embodiments, each single membrane sheet has an arrangement of zigzag corrugations arranged in the plane of the membrane sheet, and extending parallel to one another in a first direction (y-di recti on) in the x-y plane of the plate. Each single membrane sheet - and thus the double plated membrane - have some of the properties of a Miuri-Ori fold: the membrane plate has a negative Poisson ratio, and exhibits auxetic properties. For example, when the double plate 1310 is stretched in the x- direction, it increases in width in the y-direction.

The pairs of sheets are joined such that outward facing ridges of the corrugations coincide to create a space between the sheets (analogous to the space 10i shown in Figures 4 or 5). The space of this embodiment forms a channel 1312 that is continuous from a first position at one corner 1313 of the plate to a second position at an adjacent corner 1314 of the plate, and passes around the majority of the plate under its surface. The channel may be used for insulation of the tank, or may be used to circulate a gas or liquid such as a cooling agent inside the membrane space.

The plates 1310a-d are shaped to tesselate with one another and in this embodiment are identical to one another. The plates are configured to be joined together to form a membrane wall 1300, and the modular nature of the plates provides a scalable tank construction system suitable for forming small or very large tanks (or sized in between) of a variety of shapes. Adjacent plates may be welded to one another, for example by laser welding methods known in the art. To enable fluid communication between the respective intra-membrane channels formed in respective plates, pipes may be incorporated into the structure to provide inlets and outlets to the channels. An example of a pipe is shown schematically at reference numeral 1320 in Figures 13A and in the enlarged view of area B in Figure 13B. Pipes 1320 join horizontally adjacent plates 1310a and 1310b, and 1310c and 1310d to enable fluid communication between the respective channels. In alternative embodiments, fluid communication can be established between vertically adjacent plates 1310a and 1310c, and/or 1310b and 1310d. All or some of the intra membrane spaces may be horizontally and/or vertically connected, and configurations which connect the spaces through rows and/or columns of joined plates or subsets of plates in series or in parallel are within the scope of the invention. Incorporating pipes is a convenient way of establishing and/or maintaining fluid communication between plates which are welded together. However, other approaches to providing respective outlets and inlets to the intra-membrane spaces to facilitate fluid communication may be used in other embodiments of the invention, including for example bespoke welding techniques and/or the use of inserts.

Variations to the above-described embodiments fall within the scope of the invention. For example, although the drawings show zigzag formations with regular repeating angles between the straight portions of the zigzag, embodiments of the invention may have varying angles along the length of zigzag, to account for uneven stresses anticipated in the thermal cycling of the membrane. Alternatively, or in addition, the zigzag may be formed as a continuous curve (e.g. sinuisoidal) pattern, without the straight portions 115a, 115b as depicted in earlier embodiments.

Transporting and storing LH at atmospheric pressure inside a membrane tank is facilitated according to the present invention. At this condition the LH has a higher density which allows larger LH volumes to be transported or stored.

The problem with swelling of hydrogen is also avoided under such conditions.

The double-plated membrane plate as discussed above provides also a higher mechanical strength to the membrane plate while at the same time the double plated membrane still has some capability to expand and contract due to the corrugations. These features also provide resilience and enable a membrane tank according to the present invention to withstand damage due to sloshing.

When embodied onboard a ship the strength and elasticity of the double plated membrane provides also improved protection if there is a collision involving the ship.

According to an example of embodiment of the present invention a membrane plate of a membrane cargo tank may provide transport or storage of liquified hydrogen (LH), wherein the membrane plate (10) comprises a corrugation pattern created by a plurality of zigzag shaped protrusion (14) running in parallel across a surface of the membrane plate from one end of a surface of the membrane plate to an opposite located end of the surface, wherein the respective plurality of the zigzag shaped protrusions is arranged with an equal distance in between them.

According to another example of embodiment of the present invention a membrane cargo tank comprising at least one membrane plate according to the present invention.

Various modifications to the above-described embodiments may be made within the scope of the invention, and the invention extends to combinations of features other than those expressly claimed herein.

Claims

1. A membrane plate (10) for a membrane cargo tank providing transport or storage of a cryogenic fluid such as liquified hydrogen (LH), wherein the membrane plate (10) is substantially planar and comprises a corrugation pattern created by a plurality of zigzag shaped protrusions (14) running in parallel across a surface of the membrane plate from a first edge of the membrane plate to an opposing second edge of the surface, wherein the plurality of the zigzag shaped protrusions is arranged such that an increase or decrease in a first in-plane dimension of the membrane plate results in a respective increase or decrease of a second in-plane dimension of the membrane plate, the second dimension being orthogonal to the first dimension.

2. The membrane plate of claim 1, wherein the zigzag shaped protrusions are arranged with an equal distance in between them at the first edge and/or the second edge of the membrane plate.

3. The membrane plate of claim 1 or claim 2, wherein the membrane plate comprises two membrane sheets welded together such that a space in between the two membrane sheets is created by the zigzag shaped protrusions facing away from each other on each respective membrane sheet.

4. The membrane plate of claim any of claims 1 to 3, wherein the membrane plate is rectangular shaped and opposing edges of the membrane plate are provided with corresponding corrugation patterns.

5. The membrane plate of any of claims 1 to 4, wherein the membrane plate is substantially rectangular shaped and: an end area on a first side of the membrane plate is arranged with a first corrugation pattern, a second end area on a second end of the membrane plate is arranged with a second corrugation pattern, an end area of a third side of the membrane plate running in parallel with the first side is arranged with the first corrugation pattern, an end area of a fourth side of the membrane plate running in parallel with the second side is arranged with the second corrugation pattern.

6. The membrane plate of any of claims 1 to 5, wherein the zigzag shaped protrusions create zigzag shaped ridges and/or zigzag shaped valleys between the first edge of the membrane plate and the second edge of the membrane plate, the heights of the ridges being substantially constant and/or the depths of the valleys being substantially constant along their respective paths between the first and second edges.

7. A membrane cargo tank comprising at least one membrane plate according to any of claim 1 to claim 6.

8. The membrane cargo tank of claim 7, comprising a first membrane plate joined to a second membrane plate via a part-cylinder shaped member.

9. The membrane cargo tank of claim 8, wherein a first longitudinal edge of the part- cylinder shaped member is connected to a first edge of the first membrane plate having a first corrugation pattern, and a second longitudinal edge of the part- cylinder shaped member is connected to the second membrane plate on a second edge of the second membrane plate having a second corrugation pattern.

10. The membrane cargo tank of claim 8 or claim 9, wherein the part-cylinder shaped member is arranged with parallel running protrusions, wherein the parallel protrusions are orthogonal to a longitudinal direction of the part-cylinder shaped member.

11. The membrane cargo tank of claim 10, wherein the number of parallel running protrusions equals the number of parallel running zigzag protrusions on the membrane plate.

12. The membrane cargo tank of claim 10 or claim 11, wherein the distances between the parallel running protrusions on the part-cylinder shaped member surface equals the distances between the parallel running zigzag protrusions on the membrane plate at an edge of the membrane plate.

13. The membrane cargo tank of any of claims 7 to 12, comprising a bracket having a first side surface and a second side surface arranged orthogonally to the first side surface, wherein a plurality of protruding fingers is arranged on each respective first and second side surface of the bracket.

14. The membrane cargo tank of claim 13, wherein the protruding fingers on the first side surface are connected to a first membrane plate, and the protruding fingers on the second side surface are connected to a second membrane plate.

15. The membrane cargo tank of claim 13 and any of claims 8 to 12, wherein the bracket is mounted across the part-cylinder shaped member on an outside of the part-cylinder shaped member.

16. The membrane cargo tank of any of claims 13 to 15, wherein a number of protruding fingers on each of the first and second side surfaces equals the number of parallel zigzag protrusions on the membrane plate

17. The membrane cargo tank of any of claims 13 to 16, wherein the distance between the respective fingers equals the distance between the respective zigzag protrusions at an edge of the membrane plate.

18. The membrane tank of any of claims 8 to 17, wherein the direction of the parallel zigzag protrusions on the first membrane plate is orthogonal to the direction of the zigzag protrusions on the second membrane plate when they are joined together via the part-cylinder shaped member.

19. The membrane tank of any of claims 8 to 17, wherein the direction of the parallel zigzag protrusions on the first membrane plate is arranged in a same direction to as the zigzag protrusions on the second membrane plate when they are joined together via the part-cylinder shaped member.

20. The membrane tank of claim any of claims 7 to 19, wherein the membrane plate is a double-plated membrane formed from two membrane sheets to define a space therebetween.

21. The membrane tank of claim 20, wherein the space is used for insulating the tank.

22. The membrane tank of claim 20, wherein the space contains a fluid.

23. The membrane tank of claim 20, wherein the space contains a cooling agent.

24. The membrane tank of any of claims 13 to 23, comprising a plurality of double- plated membrane plates formed from two membrane sheets to define a space therebetween, wherein the respective spaces of at least two of the plurality of double-plated membrane plates are fluidly connected.

25. The membrane tank of claim 24, wherein the respective spaces of at least two of the plurality of double-plated membrane plates are fluidly connected via pipes or inserts.

26. The membrane tank of any of claims 7 to 25, comprising a plurality of membrane plates joined together in the same plane.

27. The membrane tank of claim 26, wherein plurality of membrane plates are substantially identical.

28. A membrane tank assembly comprising the membrane tank of any of claims 7 to 27, and an outer support structure arranged on an outside of the membrane tank.

29. The membrane tank assembly of claim 28, wherein a further membrane is arranged as part of the support structure.

30. The membrane tank assembly of claim 28 or claim 29, wherein a plurality of rods is arranged in between the membrane tank and the support structure thereby creating a void between the membrane tank and the support structure.