NO347960B1

NO347960B1 - Arrangement of a barrier for containing liquid gas in a hull compartement of a marine construction and a method for assembly of the arrangement

Info

Publication number: NO347960B1
Application number: NO20201028A
Authority: NO
Inventors: Fred-Olav Haug; Carsten Hagane; Miks Dorins; Dan Snops; Yezhou Yi; Hong Cheng
Original assignee: Shanghai Bluesoul Environmental Tech Co Ltd; Torgy LNG AS
Priority date: 2020-09-18
Filing date: 2020-09-18
Publication date: 2024-05-27
Also published as: NO20201028A1; WO2022057900A1

Description

ARRANGEMENT OF A BARRIER FOR CONTAINING LIQUID GAS IN A HULL COMPARTEMENT OF A MARINE CONSTRUCTION AND A METHOD FOR ASSEMBLY OF THE ARRANGEMENT.

Technical Field

The present invention relates to an arrangement for containing liquid gas in a hull compartment of a marine construction, such as vessels, etc. To be specific, the invention relates to a barrier for preventing liquid gas leaking from the compartment into the hull structure surrounding a hull compartment of the marine structure. The preferred liquid gas stored in the hull compartment is liquefied natural gas (LNG) or liquefied ethylene gas (LEG).

Background Art

Tank systems is based on commonly used containment system for liquefied petrol gas (LPG), of which is a liquid at -40⁰C.The present invention relates to containment system that is developed for media at temperatures below -55⁰C, including liquefied natural gas (LNG), liquefied ethylene gas, liquefied nitrogen gas and other liquid gas rather than LPG. These containment systems require a secondary barrier to ensure the integrity of the total system in the event of a primary barrier leakage.

Publications JPS4983017 and JPS5362215 shows examples of prior art barriers.

JPS4983017 discloses a low temperature liquefied gas storage tank having metal thin film applied to the inner surface of the tank. The metal thin film further has bent portions shaped as honeycomb structures.

JPS5362215 shows membrane plates joined by sliding the membrane onto a separate joint piece. The membrane plates form a check pattern.

A marine liquid gas containment system is a liquid tight compartment with thermal insulation. The liquid gas remains extreme low temperature in the compartment and the purpose of thermal insulation is to insulate the liquid gas from influx of heat and to protect the hull construction of the liquid gas ship from the extreme low temperature of LNG.

A membrane containment system is based on a thin barrier (primary barrier) and a collecting barrier (secondary barrier) outside the primary barrier. Both barriers are supported through thermal insulation to the adjacent ship hull structure. Such containment system is not self-supporting in that the ship hull forms the load bearing structure. Membrane containment systems are provided with a secondary barrier to ensure the integrity of the total system in the event of a primary barrier leakage.

The containment system may alternatively be an IMO Independent Type-A tank (categorized by the International Maritime Organization (IMO) in the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, normally known as the IGC Code).

The latter tanks are commonly used for transport of LPG installed in cargo hold where the hold boundaries are covered with insulation and the inner surface of the insulation is equipped with metallic (stainless steel) secondary barrier (membrane). Secondary barrier is required for handling liquid colder than -55⁰C. These barriers are not suitable for LPG storage.

The concept of the IMO A-tank requires the system to comply with the situation that a sudden and total collapse of the cargo tank occur. In the described scenario, there must be a secondary barrier that has to act as temporary containment system for the LNG for at least 15 days without letting any liquid gas leak through the secondary barrier. The temperature of liquid gas is usually far too low to be acceptable to the hull steel structure, and a substantial leak through the secondary barrier will likely cause fatal cracks in the hull steel structure.

There are number of materials to consider for low temperature applications, such as secondary barrier construction. Currently, there are membranes built from triplex foil composite, stainless steel and Invar in the market. Large operational temperature range of the product and ship motions on waves also require a high degree of flexibility of the system.

Low thermal contraction material, like invar, benefits the system with smaller thermal movement. However, it is very expensive, challenging to work with and difficult to preserve or store.

Triplex foil composite is a much lighter solution, but it has a more complex and not stable production process leading to expensive cost.

In that case, a barrier system is required, that may be used in containment systems for containment of liquid gas at low temperatures. The system is cheaper, easier to assemble and that could tolerate the forces caused by shrinking of the barrier system due to the influence of the cold liquid gas in the tank.

The barrier system is both applicable as a primary barrier in a membrane containment system or as a secondary barrier in an independent containment system with IMO-A tank.

The pattern formed by the plurality of membranes always creates a three-way corner that utilizes flexibility of the panel geometry.

Main portion of the membrane panels in the barrier are fixed at the center, which effectively separates the area into individual panels, so that each individual panel contracts around its fixation point by means of a flexible element surrounding it.

Further and other objects, features and advantage of the invention will appear from the following description and figures of preferred embodiments of the invention.

Summary of invention

The invention relates to an arrangement for containing liquid gas in a hull compartment of a marine construction. The described arrangement comprises a barrier for preventing liquid leaking from the compartment into a hull structure surrounding the hull compartment of the marine construction. The invention is distinctive in that the barrier comprises a plurality of rectangular membrane panels, each comprising surrounding edge plates extending upwardly on the periphery of the membrane panel, said edge plates of adjacently arranged membrane panels being attached together in welded connections forming a fishbone pattern formed of the plurality of membrane panels. The said plurality of membrane panels forms three-way connections, where the welded connections between adjacently arranged membrane panels extend in three distinctive directions from each three-way connection to form a T-connection between three adjacently arranged membrane panels.

The invention further relates to an assembly method of membrane panels of the barrier to prevent leakage of fluid gas from a hull compartment of a marine construction containing the fluid gas into the hull structure of the marine construction. The method comprises the following steps:

- welding two adjacent membrane panels together at the free end of the edge plates and

-form a pattern where a plurality of membrane panels form three way connections where the welded connections between adjacently arranged membrane panels extend in three distinctive directions from each three way connection.

Preferable embodiments are set of in the accompanying claims, to which reference are made.

Preferably, the liquid gas is liquefied natural gas (LNG) or liquefied ethylene gas (LEG).

Preferably, the total length of one continuous welding has a maximum length of 3000 mm. Preferably, the maximum length of a continuous welded connection is 2100 mm.

Preferably, the assembled membrane panels are equipped with reinforcement devices arranged to cover the three-point junction. There may be one reinforcement device arranged at each three-point junction.

Preferably, a majority of the plurality of membrane panels are adapted to be connected to the underlying surface through a fixation point. The fixation point is situated a distance from the welded connections so that the three-way connections are allowed to deform from an initial position. This is preferably at the center of the membrane panel.

The membrane panel for use in a barrier to prevent leakage of fluid gas from the hull compartment of the marine construction containing the fluid gas into the hull structure of the marine construction comprises a base plate and edge plates. The described edge plates form an extension of the base plate in an angled distance away from the base plate. The angled distance is more than 90°.

An arrangement for containing liquid gas in a hull compartment of a marine construction. The described arrangement comprises a barrier for preventing liquid leaking from the compartment into a hull structure surrounding the hull compartment of the marine construction. The barrier comprises a plurality of membrane panels, attached together in welded connections, said plurality of membrane panels forms a pattern, a majority of the plurality of membrane panels are adapted to be connected to the underlying surface of the membrane panel through a fixation point arranged close to the center of the respective membrane panels.

The membrane panel for use in a barrier to prevent leakage of fluid gas from a hull compartment of a marine construction containing the fluid gas into the hull structure of the marine construction comprises a base plate and edge plates, said edge plates form an extension of the base plate in an angled distance away from the base plate. The angled distance is more than 90°.

Brief description of drawings

Figure 1 shows a general arrangement of an LNG cargo system comprising a primary barrier and a secondary barrier,

Figure 2a shows a membrane panel according to an embodiment of the invention, perspective view,

Figure 2b shows a barrier comprising membrane panels according to an embodiment of the invention with welded corners,

Figure 2c shows a barrier comprising membrane panels according to an embodiment of the invention with form-fitted corners,

Figure 3 shows a detailed view of the membrane panel of figure 2a, viewed respectively from above and side,

Figure 4 shows a perspective view of a rectangular membrane panel according to the invention, viewed from different angles,

Figure 5- 8b shows examples different patterns of assembled membrane panels forming a barrier, all ending up in a three-way corner connection,

Figure 9-11 shows a detailed view of a possible flexibility of the welded connections between adjacently arranged membrane panels,

Figure 12 shows a detailed view of a corner membrane panel arranged in the hull construction,

Figure 13-14 shows an illustration of the barrier covering the hull structure of the marine vessel and the principle with support elements attached to the second membrane,

Figure 15 shows fixation points for connection to the insulation in the hull structure, and further illustrates contraction appear by thermal cool down, which allow all membrane panels to work/move independently,

Figure 16 shows an embodiment of a reinforcement device adapted to cover the three-point junction of rectangular membrane panels.

Detailed description of the invention

It is to be noted that the barrier is made up by a plurality of membrane panels according to the invention. The barrier may be a primary barrier or a secondary barrier in the containment system.

A pattern is defined as the design that the plurality of membrane panels forms when assembled together. Examples of patterns are illustrated in fig.5-8b, as fishbone pattern, honeycomb pattern, circle/triangular pattern and circle/diamond pattern.

Figure 1 shows an example arrangement where the barrier according to the invention is a secondary barrier in the cargo system.

The figure is illustrating a general arrangement of an LNG (Liquefied natural gas) cargo system 1. The system comprises a liquid tight self-supporting LNG-tank 7 with a primary barrier 3. This tank must fulfill the requirements of an IMO type A containment tanks. These types of tanks are design to transport nonpressurized LNG or other gases in liquid phase at low temperatures. The figure shows a system with a tank with a chamber for storing liquid gas. The system 1 may also comprise more than one tank with a common secondary barrier.

The system 1 further comprises a thermal insulation component 5 with a liquid tight secondary barrier 4. The primary barrier 3 and secondary barrier 4 are separated by an access inspection space 6. The LNG-tank is connected to a hull structure of the vessel 2 through support devices 8, 10, 11. The supporting devices 8, 10,11 are arranged to support the LNG tank 7 in one end and are further extending through the secondary barrier 4 and connected to the hull structure of the vessel 2.

In this embodiment of containment liquid gas system, the barrier according to the invention is arranged as a secondary barrier 4. This secondary barrier 4 is arranged in connection with the insulation member 5 in the system.

The barrier according to the invention is not limited to this arrangement. The barrier according to the invention may thus also be arranged as a primary barrier in a containment of liquid gas system (not shown).

The figures 2-15 illustrates the principle of a barrier according to the invention in greater detail. The barrier is assembled by a plurality of membrane panels 20 which will be described further in the accompanying figures.

Figure 2-4 are illustrating a membrane panel 20, which is according to an embodiment of the invention and viewed from different angles.

Figure 2a shows a perspective view of an example design of the membrane panel according to the invention. The panel 20 has a rectangular base plate 21 and four edge plates 22a, 22b at the periphery of the base plate. The edge plates 22a, 22b are arranged perpendicularly to the base plate 21. The edge plates 22a, 22b may further be welded together in all four corners 24 of the membrane panel 20 as illustrated in the figure 2b. Alternatively, a panel 20’ may be form-fitted in a molding press or similar. Each panel has continuously arranged corners 24’. This is illustrated by the figure 2c. The membrane panel 20, 20’ will thus have a box lid – shape. For simplicity, the reference number 20, 21, and 22a, 22b covers hereinafter both embodiments with welded and formfitted corners.

Figure 2a further indicates a fixation point 23. This fixation point 23 is situated in the center of the panel and is illustrating that the membrane panel 20 is intended to be attached to the isolation member 5 or the underlying surface in a single point, depending on what kind of barrier it is. Preferably, the fixation point 23 is in the center of the membrane plane 20. The fixation point 23 may however deviate some distance from the center point in some embodiments. The fixation point 23 must, however, not be arranged too close to any of the edge plates 22a, 22b of the panel 20 as this will reduce the edge plates 22a, 22b possibility to move. This will be described further in fig.9-11.

The membrane plane 20, 20’ is preferably made of stainless steel. Other material or alloy of steel may be chosen as alternative embodiments of the invention. Figure 3 shows an example dimension of the membrane panel 20. The base plate 21 may have a rectangular shape of 700 mm x 1400 mm. The edge plate 22a, 22b may further be extended a distance 70 mm from the base plate 21.

The thickness of the membrane panel 20 may be 1 mm.

These dimensions are only example measurements and not limiting for the membrane panels 20 of the invention. Other sizes of the base plate 21 are also possible as well as other heights of the edge plate 22a, 22b. A preferred ratio of the height of the edge plate 22a, 22b and the width of the panel 20 may be 1:10.

The thickness and the dimension of the rectangular plate 21 are not considered to be interrelated. There may be other dimensions of the rectangular plate 21, edge plate 22a, 22b or the thickness of material of the panel 20, which are all embodiments of the invention.

The figure 3 further discloses that there is a rounded transition 25 between the base plate 21 and respective edge plate 22a, 22b. The respective edge plate 22a, 22b thus forms an upwardly extension of the base plate 21 at the periphery of the membrane. The respective edge plate 22a, 22b is also extending upwardly from the base plate 21 in a slightly sloping angle as shown in the figure. This means that each of the edge plates 22a, 22b do not extend exactly perpendicular from the base plate 21. The angle between the base plate and the respective edge plate 22a, 22b is more than 90°. A non-limiting example for the angle may be 91,23°. A consequence of the slightly sloping edge plate 22a, 22b, is that the free end of the edge plate 22a, 22b being situated in a vertical plane B that is positioned outside of a vertical plane A through the opposite attached end 27 of the edge plate 22a, 22b as illustrated in the figure 3. There is also indicated a displacement of 1,5 mm between the free end 26 and the attached end 27 of the edge plate 22a, 22b. This is only an example displacement value, only illustrating that there is a possibility for the membrane panels 20 to compress towards each other due to the movement of the marine construction when there is no liquid gas in the compartment, ie. when the membrane panels 20 are in an initial position without exposed to any shrinking forces.

Figure 4 shows rectangular shapes of the membrane panel 20 viewed from different sides. However, the membrane panel 20 may have completely other designs.

The membrane panels may also, for instance, have hexagon shapes 30, or a circular shape 40 combined with triangular 43 or diamond shape 43’, as illustrated in fig.7, 8a and 8b.

Figure 5-8b discloses a plurality of membrane panels 20, 30, 40, 43, 43’ of different design assembled together in specific patterns as shown in the figures. All of the different designs 30, 40, 43, 43’ may have similar rounded transition and sloped edge plates 22a, 22b, 32, 42, 45, 45’ as the rectangular shaped membrane panels 20, from fig.3 and an angular distance from the base plate that is more than 90°. The example dimension described in relation to the membrane panel 20 are also applicable of the membrane panels according to fig. 5-8b.

The barrier is made up of a plurality of membrane panels 20, 30, 40, 43, 43’. In figure 5, the membrane panels 20 are attached forming a fishbone pattern. The membrane panel 20 is rectangular type as illustrated in figure 4. The fishbone pattern being formed in a way that two and two adjacent membrane panels 20, are arranged so that the longitudinal side of the membrane cover half the longitudinal side of the adjacent membrane panel 20. A length of a continuous welded connection 29 is in this embodiment maximum 2 times the longitudinal length of one membrane panel 20. Another preferred option is maximum 1.5 times the longitudinal length of the membrane panel. Two welded connections 29 are in this design adapted to meet in a three-point junction or connection 28.

The similar fishbone pattern is illustrated in figure 6. However, this design is inverted compared to the design of figure 5. In this pattern, the length of a continuous welded connection 29 are 12/3 times the longitudinal length of one membrane panel 20. Two welded connections 29 are also in this design adapted to meet in a three-point junction 28.

In both designs, the membrane panels 20 have mainly equal dimensions to form the patterns. It is preferable to use membrane panels 20 with equal shape as this makes the assembly of the respective membrane panel 20, easier and more cost efficient. However, the invention is not limited to the use of equal shaped membrane panels through the whole barrier.

Figure 7 shows a plurality of membrane panels 30 of hexagonal shape assembled in a honeycomb pattern. Each membrane panel 30 comprises a base plate 31 and an edge plate 32. The edge plate 32 is extending a distance upwardly from the base plate 31. The length of a welded connection 39 is equal the length of one of hexagonal length of the membrane panel 30. Three welded connections 39 are in this design adapted to meet in a three-point junction 38.

Figure 8a-8b shows circular membrane panels 40 combined with complementary membrane panels 43, 43’ shaped to fit between the circular membrane panels. Figure 8a has triangular shaped complementary membrane panels 43 with cut outs for the circular panels 40. Figure 8b discloses diamond shaped complementary panels with similar cut outs for the circular panels 40.

The membrane panels 40, 43, 43’ comprises a base plate 41, 44, 44’ and edge plate 42, 45, 45’ respectively. Welded connections 49a, 49b are formed between the circular panels 40 and the complementary membrane panel 43, 43’. The welded connections are thus both radially extending from the circle membrane panel 40 and following a circle sector of the circular membrane panel 40. These welded connections are referred to as radial welded connections 49a and circle welded connections 49b in both embodiments of fig.

8a and 8b. The length of a continuous welded connection is maximum the distance between two circular membrane panels 40 or the length of a circle sector between two radial welded connections 49b. The welded connections 49a, 49b are adapted to meet in a three-point junction 48 in both embodiments of figure 8a-8b.

All of the different patterns exemplified by fig 5-8b thus creates a relative short continuous length of welded connections 29, 39, 49a, 49b. These patterns create three-way junctions 28, 38, 48 between welded connections 29, 39, 49a, 49b that allows utilizing not only the flexibility of the bottom opening of the edge plate 22a, 22b, 32, 45, 45’ but also the bending flexibility on the free end of the edge plate 22a,22b, 32, 45, 45’ itself. See figure 10 and associated description below for further explanation to this. The edge plates 22a, 22b, 32, 45, 45’ in one membrane panel 20, 30, 40, 43, 45’ being continuous around the whole surface, with no interruption, but the set up and change of directions by the plurality of membrane panels 20, 30, 40, 45 provides the flexibility by the threeway junctions 28, 38, 48. As illustrated in the figures, the three -way junction 28, 38, 48 are formed by three welded connection that meets in one point, the three way junction or connection 28, 38, 48. The figure further shows that the membrane planes 20, 30, 40, 43, 43’ are assembled so that the each welded connections in one continuous direction do not extend more than the three way junction 28, 38, 48, which can adopt or flex due to thermal contraction.

The patterns allow avoiding continuous length with steel or weld, with no interruptions of the raised edge or edge plate 22a, 22b, 32, 42, 45, 45’ itself, still providing the flexibility needed.

The principle of the invention will be described in detail by reference to the accompanying figures 9-11.

Figure 9 is illustrating the two adjacent membrane panels 20, 30, 40.43, 43’ The edge plates 22a, 22b, 32, 42, 45, 45’ of the two adjacent membrane panels 20, 30, 40, 43, 43’ are welded together only at the top free end 26 of the edge plates 22a, 22b, 32, 42, 45, 45’. The remaining part of the edge plates 22a, 22b, 32, 42, 45, 45’ are thus not connected and are movable with respect to each other. The base plates 21, 31, 41, 44, 44’ are also flexible as they are not connected to the underlying surface, such as the insulation 5 near the edge plates 22a, 22b, 32, 42, 45, 45’.

As further shown in figure 10, there is a space 12 at the bottom between two adjacent membrane panels 20, 30, 40, 43, 43’ providing the flexibility when the edge plates 22a, 22b, 32, 42, 45, 45’ are bent. The welded connection 29, 39, 49a, 49b provides a rigid connection. The free end of the edge plate 26 is thus being rigid, while the bottom part provides the flexibility.

When the membrane planes 20, 30, 40, 43, 43’ of the barrier gets cold due to the cold liquid gas, the material of the membrane panels 20, 30, 40, 43, 43’ will retract. The arrangement with the three-way conjunction 28, 38, 48 will thus result in a deformation as illustrated in figure 10-11. The three-way conjunction 28 forms a T-connection in the example of the fishbone structure. The threeway connection or T-connection is moved away from an initial position as a consequence of the shrinking of the material. In the example with fishbone structure, the three-way junction moves along the perpendicular welded connection in a shrinking position as shown in the figure 10-11.

These designs having only a weld along the free end 26 of the edge plates, also provides a flexibility as the panels are allowed to move towards each other at the bottom when there is no liquid in the compartments as disclosed. This is relevant for all of the designs of figure 5-8b. The reference number 26 refers therefore also to all of the designs in fig 5, 6, 78a and 8b.

Figure 11 is further illustrating the flexibility and the movement away from the initial position by the membrane panels 20, 30, 40, 43, 43’.

The figure illustrates a slightly curved shape in the each of the three-way junctions of the barrier when exposed to cold temperature form the liquid gas. The figure uses the fishbone structure to illustrate the principle. The other designs will however have the same effect in the three-way junction.

Figure 12 shows a further embodiment of a detail of the barrier with a corner membrane panel 50. This corner membrane panel 50 differs from the remaining membrane panels in that it has a bending angle 51. The corner membrane panel 50 is particularly suitable in corners of the hull structure 2. The corner membrane panel 50 is adapted to mate with corresponding bending angle in the hull structure 2. The corner membrane panel 50 is preferably not fixated to the underlying surface. The corner membrane panel 50 is only attached to the adjacent membrane panels 20, 30, 40, 43, 43’ through the welded connections 29, 39, 49a, 49b as disclosed above.

Figure 13 discloses the A-Tank 7 from fig 1 with the primary barrier 3 that is supported by a series of thermally insulating supports elements 8, 10, 11 (figure 1). The insulation support elements 8, 10,11 accommodate vertical and horizontal tank loads as well as prevent tank from rolling, pitching and flotation scenarios. Since the support elements 8, 10, 11 are penetrating the insulation 5 and the barrier/membrane panels 20, 30, 40, 43, 43’ the interface between the secondary barrier 4 and support elements 8, 10, 11 is achieved by a support landing plate 55 welded to the support elements 8, 10, 11. The support landing plate 55 forms an integral part of the secondary barrier 4.

Fig 14 shows this landing plate 55 and connection with the support element in greater details.

Figure 15 discloses the membrane panel attached to the insulation through fixation points 23.

During the lifecycle of the membrane panel, it will undergo loads induced by thermal contraction of materials, ships accelerations and hull deformations. It is considered that the thermal loads and hull deformations will produce similar effect on the barrier and both are dealt by edge plates 22a, 22b, 32, 42, 45, 45’ formed by each of the membrane panels 20, 30, 40, 43, 43’ as discussed throughout the description.

In order to ensure controlled operation of flexible elements and keep the membrane panels 20, 30, 40, 43, 43’ in place, the respective membrane panels 20, 30, 40, 43, 43’ are fixed to the insulation at the middle of each plate. This arrangement ensures that flexible elements are working independently each covering deflections in their own region. It is not a requirement that all of the membrane panels are fixed to the underlying surface, as long as a major part of the panels are attached through the fixation points 23. The figure 15 further indicates that the membrane panels tend to shrink towards the fixation point 23. It is not necessary that all the membrane panels have a fixation point 23. It is enough that majority of membrane panels have a fixation point 23 and is adapted to be attached to the underlying surface. Some of the membrane panels, such as the corner membrane panels 50 may freely arranged without fixation point 23 and only attached to the adjacent membrane panel 20.

Figure 16 discloses a reinforcement device 60 that may be used in connection with the barrier. The reinforcement device 60 be covering the three-way junction 28 as shown in the figure. The reinforcement device 60 extends in a distance from the three-way junction 28 in each direction along each of the welded connections 29 of the edge plates 22a, 22b. This reinforcement device 60 has the purpose of diverge the forces acting on the three-way junction 28 and thus acting as a reinforcement to the three-way junction 28.

The figure 16 is illustrating the reinforcement device 60 suitable for the membrane panels 20 with rectangular shape as shown in figure 2-6. However, similar reinforcement device may be used with membrane panels with other design, such as the designs illustrated in figure 7-8b. These reinforcement devices must then be modified to mate with these designs.

Claims

Patent Claims

1. An arrangement for containing liquid gas in a hull compartment (7, 6) of a marine construction, said arrangement comprising a barrier for preventing liquid leaking from the compartment into a hull structure (2) surrounding the hull compartment of the marine construction, characterised in that the barrier comprises a plurality of rectangular membrane panels (20) each comprising surrounding edge plates (22a, 22b) extending upwardly on the periphery of the membrane panel (20), said edge plates (22a, 22b) of adjacently arranged membrane panels (20) being attached together in welded connections forming a fishbone pattern of the plurality of membrane panels (20), said plurality of membrane panels (20) form three way connections or junctions (28) where the welded connections (29) between adjacently arranged membrane panels (20) extend in three distinctive directions (29) from each three way connection or junction (28) to form a T-connection between three adjacently arranged membrane panels (20).

2. The arrangement for containing liquid gas according to claim 1, wherein the total length of one continuous welded connection (29) has a maximum a length enabling the three-way connection or junction (29) to adapt or flex due to thermal contraction without breakage of the welded connection (29).

3. The arrangement for containing a liquid gas according to claim 1 or 2, wherein each membrane panel (20) comprises a base plate (21) and edge plates (22a, 22b,), said edge plates (22a, 22b) form an extension of the base plate (21) in an angled direction away from the base plate (21) to form a raised level of the membrane panel (20) around the periphery of the base plate (21).

4. The arrangement for containing a liquid gas according to claim 3, wherein a plurality of membrane panels (20) are welded together along a free end (26) of the edge plate(s) (22a, 22b).

5. The arrangement for containing a liquid gas according to any one of the claims 1-4, wherein the majority of the plurality of membrane panels (20, ) have equal shape, such as rectangular or hexagonal.

6. The arrangement for containing a liquid gas according to any one of the claims 1-5, wherein the barrier comprises corner membrane panels (50), said corner membrane panel comprises a bending angle (51) adapted to mate with a bending angle in the hull structure (2).

7. The arrangement for containing a liquid gas according to any one of the claims 1-6, wherein a majority of the plurality of membrane panels (20,) are adapted to be connected to the underlying surface through a fixation point (23).

8. The arrangement for containing a liquid gas according to any of the claims 1-7, wherein the arrangement further comprises a self-supporting liquid tank (7) with a primary barrier (3) and an access space (6) arranged outside of the primary barrier, said plurality of membrane panels (20, ) forming a fluid tight second barrier (4) arranged in connection with an insulation member (3) surrounding the access space (6) of the hull compartment in the marine construction (2).

9. The arrangement for containing a liquid gas according to claim 8, wherein the arrangement further comprises a support device (8, 10, 11) to support the self-supporting liquid tank (7), said support device (8, 10, 11) extends through an opening in a membrane panel (20) of the plurality of membrane panels (20) said membrane panel (20) and support device (8, 10, 11) are connected through a support landing plate (55), said membrane panel (20), the support device (8, 10, 11) and the support landing plate (55) are welded together forming a fluid-tight seal.

10.The arrangement for containing a liquid gas according to any one of the claims 1-9, wherein the arrangement further comprises reinforcement devices (60) adapted to cover the three-point connection or junction (28, 38, 48).

11.A method for assembly of membrane panels according to any one of the claims 1-10 for use in a barrier to prevent leakage of fluid gas from a hull compartment (7) of a marine construction containing the fluid gas into a hull structure (2) of the marine construction, characterised in that the method comprises the following steps of

- welding two adjacent membrane panels (20, ) together and

- forming a pattern where a plurality of membrane panels (20) form three way connections or junctions (28) with welded connections between adjacently arranged membrane panels (20) extend in three distinctive directions (29) from each three-way connection or junction (28).