NO145997B - BRAKE CONSTRUCTION FOR CRYOGEN CONTAINER, LIQUID GAS - Google Patents

Description

This invention relates to a corner construction for

a gas container for cryogenic liquefied gas, where the container has a wall or walls with corners and a metal lining resistant to low temperatures within the container wall as well as a heat-insulating layer arranged between the metal lining and the container wall, where the insulation layer comprises at least a foam layer that is reinforced with fibers.

A container or tanker for the storage and/or transport of cryogenic liquids must be designed to withstand very low temperatures. Usually, rooms of this type are built with an outer, rigid wall, a heat-insulating layer arranged against the inner surface

ten of the wall as well as a membrane against the inner surface of the thermal insulation layer. Several non-metallic layers are often used, e.g. of foam plastic insulation and one or more membranes, especially an inner lining or membrane, e.g. a cladding of nickel steel which is in contact with the cryogenic liquid, and one or more secondary claddings placed between the foam insulation layers. The primary cladding, which is usually made of a thin and low-temperature resistant (low thermal expansion) material, such as nickel steel, is kept in good contact with the surface of the adjacent insulation layer and transfers the internal pressure exerted by the cold, liquid gases through the thermal insulation layers to the outer container or hull of a tanker.

It is of great importance that the container or the insulation system in it is capable of withstanding great stresses caused by the cold liquid during the transitions in the cooling and heating cycle that are obtained when loading and unloading the liquid,

as well as from the mechanically induced stresses from the ship's hull or when containers are moved during operation.

Critical parts of such cryogenic isolation systems

which will carry and support the primary cladding, is located at the corners, where the loads to which the cladding is subjected are transferred to the ship's hull. In membrane systems of the type mentioned above, which are designed to contain cryogenic liquids, the corners must be secured against movement caused by membrane contraction and bending of the support structure. Such corner constructions must be able to accommodate loads at different angles and in several different directions, but with minimal heat transfer to the cold load.

Fluid-tight and heat-insulating wall constructions

for cryogenic liquefied gas is previously known, e.g. from Norwegian patent 139 935, German official publication 26 39 862, Norwegian patent 141 483 and others. Heat-insulating corner constructions of the type mentioned are described in German official publication 27 35 015 and a corner construction of the type mentioned at the outset is also described in Norwegian design document 14 3 510.

A disadvantage of the previously known and relatively complex corner constructions is the difficulty in adapting the cryogenic insulation around the various components in the corner constructions, which for this purpose includes the use of intricately cut pieces of leather, and this greatly increases the costs of such cryogenic insulation systems , and the purpose of the invention is to provide a corner construction of the type mentioned at the outset which does not suffer from these weaknesses. The corner structure according to the invention is essentially distinguished by the fact that it comprises an angle element made of metal which is known to be resistant to low temperatures and is formed by two plate parts which meet each other at an angle at one of the corners of the container wall, and where each plate part has free ends arranged between the metal lining and the heat insulation layer, that the angle element is anchored in the container wall by means of several oblong or elongated metal strips, each of which is connected to one of the plate parts and runs substantially parallel to the plane of the plate part to which the metal strip is connected, so that the metal strips form an extension of the plate with which the strips are connected to transfer loads from the metal lining to the container wall.

The invention shall be explained in connection with the accompanying drawings where: Fig. 1 is a perspective drawing showing a container or tanker for methane (LNG) which comprises an insulation system and a corner structure according to the invention. Fig. IA shows a preferred fibre-reinforced insulation material which is here to be termed "3D" foam insulation and is used in the system in fig. 1. Fig. 2 is a section showing a transverse 90° corner construction of the tank or tanker t laid along the line 2-2 in fig. 1 and carried out according to the invention. Fig. 3 shows the corner construction according to the invention used in that in fig. 2 showed foam insulation system. Fig. 4 is a ground plan of the one in fig. 3 showed corner construction. Fig. 5 is an isometric view showing a series of bands or fingers parallel offset in relation to another series of bands in the corner structure. Fig. 6 is a section similar to that in fig. 2 and shows the use of a corner structure according to the invention at a tank corner which forms an obtuse angle. Fig. 7 is a section similar to that in fig. 2 and shows the use of a corner construction according to the invention at a tank corner which forms an acute angle and

fig. 8 is a section taken along the line 8-8 in fig. 1 and shows a corner according to the invention# where only a single row of strips or bands is used.

Reference should now be made to fig. 1 in the drawings where the reference number 10 indicates a tanker for cryogenic liquid such as LNGf with an inner hull 12 and an insulation system 13 arranged around the inner hull. Such an insulation system comprises an outer fiber-reinforced foam insulation layer 14 arranged against the inner hull and an inner fiber-reinforced foam insulation layer 16. Such fiber-reinforced foam insulation layers are preferably three-dimensional glass fiber-reinforced polyurethane foam layers. Such reinforced insulation materials comprise blocks of closed-cell polyurethane foam with glass fiber layers, where each fiber layer extends both in the horizontal direction and the transverse direction# called X- and Y-reinforcement fibers and fiber layers that extend sg in the vertical direction f called Z-reinforcement fibers.

Fig. IA shows this type of insulation material which comprises blocks 17 of polyurethane foam with closed cells in which is embedded a glass fiber layer 19 with protruding fiber ends 21 to be able to more easily connect the polyurethane blocks 17 to a construction element, e.g. a tank wall. Embedded in the polyurethane blocks 17 are other glass fibers 23 that extend vertically with protruding ends to more easily connect the blocks to each other and other layers of other fibers 27 extend horizontally and perpendicularly to the fibers 19. This type of reinforcement is known as X-Y-Z- reinforcement where the X fibers are longitudinal fibers, the Y fibers are transverse fibers and the Z fibers are vertical fibers and the resulting reinforced foam insulation is known as "3D foam". The planks in such a 3D polyurethane foam are preferably tied together as at 13 in fig. 2 with the help of a suitable binder # preferably a polyurethane binderf when producing the outer resp. inner insulation layers 14 and 16.

Reference should now be made to fig. 1 and 2( where there is shown a thin primary cladding or barrier membrane 18 which is placed in contact with the inner 3D foam insulation layer 16 and can be connected thereto in any suitable manner> eg by means of mechanical fasteners# comprising tongues 15 (see Fig. 8) which are received and held in place in tongue retaining means in the form of veneer strips 17 which are glued to the foam insulation layer. The cladding is made of a series of parallel sections or plate passages 19 which along their longitudinal edges have raised longitudinal flanges which are connected to adjacent flanges on other plate passages. The tongues 15 are placed between the flanges 21 on adjacent plate passages. The construction described above does not form any part of the present invention.

The primary membrane is preferably made of a low temperature stable (low thermal expansion) material, such as nickel steel t preferably a high nickel steel t such as the material marketed as "Invar" (registered trademark). The membrane 18 is made of a fluid impermeable material and forms an internal thin vessel which will enclose the cryogenic liquid. A secondary cladding 20 lies between the outer 3D foam insulation layer 14 and the inner 3D foam insulation layer 16. Such a cladding can be made of glass fiber cloth or a combination of a glass fiber cloth and a thin metal foil, e.g. aluminum foil or such a covering can be a resin-impregnated glass fiber cloth, e.g. impregnated with polyurethane resin> or such a resin-impregnated glass fiber cloth can be produced in combination with a polyvinyl fluoride film which is marketed as "Tedlar" (registered trademark). This secondary coating can be a dense coating which prevents cryogenic liquid from penetrating from the inner foam insulation layer 16 to the outer foam insulation layer.

Reference should now be made to fig. 2 to 5 in the drawings t where the corner construction according to the invention is fitted at a 90° corner. At this corner there is arranged an angle element 22 which, like the primary membrane 18, is made of a low-temperature stable material which has a small coefficient of thermal expansion, preferably a high-nickel steel t such as "Invar", which is attached to the primary membrane by welding at 24 or cladding 18. A support element or substrate 26 for angle element 22 is fitted into the inner foam insulation layer 16 adjacent to the angle elementf and the support element is bonded or glued to the foam layer 16 at 28. Such a support or substrate element 26 is preferably made of veneer and consists of two support or veneer elements arranged at a 90° angle to each other and in contact with the outer surfaces of each 90° angle element 22. The support or support element 26 not only serves as a support for the angle element 22f but also contributes to to stabilize the primary membrane 18 and forms the basis for welding. The angle element 22 is attached to the veneer support or sub-layer element 26 by means of screws 34.

A first series of metal bands 36 are first with the inner ones

ends welded at 38 to one face 40 of the angle member 22f and another series of number bands 42 similar to the bands 36f are then with their inner ends welded at 43 to the other face 44 of the angle member 22. The bands or fingers 36 and 42 which are produced of a high-strength and poorly heat-conducting (small coefficient of thermal expansion) material such as stainless steel # to be able to transfer loads from the primary cladding 18 to the ship's hull 12. In fig. 3, it is easy to see that the first series of bands 36 and the second series of bands 42 are arranged at an angle of 90° to each other (and the first series of bands 36 are arranged substantially in the same plane as the primary membrane 18 and the angular element 22 in one direction at the corner t and the other series of bands 42 are arranged essentially in the same plane as the primary membrane 18 and the angle element 22 in the other direction at the corner.

Reference should now be made to fig. 4 and 5 where it is easy to see that the first series of bands 36 consists of a series of parallel bands arranged at a distance from each other and that the second series of bands 42 similarly exists in the form of a series of parallel bands arranged at a distance from each other bandf in that the second series of bands is offset or arranged alternately in relation to the first series of bands at the corner. It should be noted that the inner ones end on

the respective bands 36 and 42 are placed in grooves 46 which are formed at appropriate locations 30 and 32 on the support member 26, and therefore the support member 26 functions as a base for welding the membrane 18 to the angle member 22 (as indicated by 38 and 43 The fingers 36 and 42 are dimensioned in such a way, especially in the width direction, that they accommodate and correspond to the predetermined load intensity to be transferred from the primary cladding 18 to the ship's hull 12.

The other ends of the fingers 36 are e.g. by welding at 48 attached to a metal band 50 which is again supported on a connecting piece, e.g. The "T" piece 52, which is connected to the ship's hull 12. The band 50 is thus mounted in a vertical position in a groove 54 in the upper part of the "T" piece 52 and is held in this by the angle 56 which butts against the outer surface of the fingers 36, and it is connected to the lower part of the "T" piece by means of a bolt and nut connection 58. The "T" piece 52 is by welding at 60 and by means of a pin 62 connected to the inside of the ship's hull 12 , and a metal spacer is inserted between the outer surface of the "T" piece and the adjacent container wall or ship's hull 12 .

A similar component system is used to attach the outer ends of the second series of straps 42 to the ship's hull 12, comprising members 50, 52 and 56 to 64.

A corner support plate 66 is provided and mounted on the two "T" pieces 52 at the corner by means of two tabs 62 to support the foam insulation layers 14<*> and 16<*> at the corners. It should be noted that the corner support plate 66 is preferably made of a metal, e.g. steel. Longitudinal support plates 68, preferably of veneer, are also fitted and connected by nut and screw connections 58 to "T" pieces 52 at opposite corners. These are arranged to support the main parts for the outer and inner foam insulation layers 14 and 16 along the length and width of the tank and at a distance from the inner wall surface of the ship's hull 12. The insulation support plates 66 and 68 which hold the foam insulation system at a distance from the inner wall in the container or the ship's hull 12, forms a water sump for the collection of water that may collect at the interior of the ship's hull.

As shown in fig. 2, there is also an element 70 arranged at the corners which is fitted into the foam at the ends of the primary cladding 18, and this element 70 comprises a number of gas drainage channels to remove gas that may come behind the primary cladding 18. This element 70 is supported on an element 74 which is inserted in a groove 76 arranged in a suitable place in the inner foam insulation layer 16. The support element 74 is preferably made of, for example, veneer and is glued to the adjacent foam insulation layer 16.

By a particular consideration of fig. 2 it is easy to see that the simple construction of the corner support according to the invention consists mainly of two series of bands or fingers 36 and 42, which are connected to the angle element 22 and to the "T" pieces 52. The construction thereby allows adaptation of the insulation layers 14' and 16<*> in the corners and around and between the bands or fingers 36 and 42 with minimal breaks or discontinuity in the foam insulation and without requiring the fitting of small pieces of foam around the elements, as was required in previously known designs. It is also easy to see that the bands or fingers will allow the passage of the secondary membrane 20, e.g. of glass fiber cloth, at the corners, thereby ensuring structural continuity in this membrane.

The corner structure according to the invention which consists mainly of the bands 36 and 42, one end of which is connected to the angle element 22 and the other end of which is connected to the "T" pieces 52 is specially designed to be able to absorb high tensile loads as well as compressive loads applied to the primary membrane. These bands or fingers, which are preferably made of a high-strength and low heat-conducting material, such as steel, will in particular be able to transfer membrane loads in different directions and angles to the tank wall or ship's hull with minimal disruption of the adjacent foam insulation or causing minimal damage on this.

It should be noted that both the primary membrane or cladding 18 and the angle member 22 are made of a material having a small, very small coefficient of thermal expansion, preferably a high-nickel steel, such as "Invar". In contrast, the bands or fingers have a higher coefficient of thermal expansion but a lower thermal conductivity, and are stronger than the material of the membrane 18 and the angle element 22. This has the advantage that less heat is transferred from the outer tank structure to the primary membrane, and the support structure has a greater strength to resist and transfer loads from the primary membrane to the outer tank wall or hull. Another advantage is that when bands or fingers are used as a buffer for the primary membrane at the corners instead of larger single pieces of metal, there are no stresses in the longitudinal direction of the bands, and thereby shrinking loads at the ends of the bands will be significantly reduced. Fig. 6 shows the use of a simple yet powerful corner construction according to the invention at an obtuse corner in the tank or tanker. It is thus easy to see that the angle member 78 which is connected to the primary cladding 18 in the manner described above forms an obtuse angle, and the two series of metal bands 36' and 42' are arranged at a similar obtuse angle to the angle member 78, the first series of metal bands 36<*> being substantially in the same plane as one surface 18a of the primary membrane 18 at this corner, and the second series of bands 42<*> being substantially in the same plane as the other surface 18a' on the primary membrane or cladding at this corner. The corner construction according to the embodiment in fig. 6 is otherwise the same as the corner construction shown in fig. 2 for a 90° angle. Fig. 7 shows application of the corner construction according to the invention at a corner in a tank or tanker which forms an acute angle. In this embodiment, the angle element 80 forms an acute angle at the corner in the same way as the angle element 22. The first series of bands 36" and the second series of bands 42" form a similar angle, with the bands 36" again lying substantially in the same plane as the direction of a surface 18a of the primary cladding 18, and the second series of bands 42" lies substantially in the same plane as the second face or direction 18a' of the primary cladding 18.

It should be noted that in the corner construction of fig. 2,

6 and 7 (where two series of bands or fingers are used, the upstanding, parallel plate passage flanges on the primary cladding plate passage 19 are perpendicular to the corner in both directions for the cladding at the corner, as can also be seen in fig. 1 in the section as is laid along the line 2-2 in Fig. 1.

However, when the plate passage flanges in one direction of the primary cladding at the corner are perpendicular to the corner while the plate passage flanges in the other direction at the corner are parallel to the corner, it then only becomes necessary to use a series of fingers to connect the cladding section where the plate passage flanges are perpendicular on the corner with the container wall or the ship's hull. This is shown in fig. 8 at a corner construction at a 135° corner in the tank of fig. 1. In this modification, it is easy to see that the upright plate passage flanges 21 which are connected to the plate 18a in the cladding 18 in one direction at the corner are perpendicular to the corner, while the upright plate passage flanges 21 which are connected to the plate 18a in the primary cladding 18 in the other direction at the corner, are arranged parallel to the corner, as is clear from fig. 1 at the section laid along the line 8-8.

From fig. 8, it will be seen that under the latter conditions only a series of metal bands 42", which can be compared to the bands 42, are connected to the angle member 82 and to the "T" piece 52<*>. This series of metal bands shown in Fig. 8 42" lies substantially in the same plane as the surface 18a' of the primary membrane which comprises the plate passage flanges 21 which are perpendicular to the corner. The fingers 42" in this corner construction will thus support, for example, the primary line part 18a' when it is, for example, subjected to contraction loads. The other surface or part 18a of the primary cladding at this corner and which is parallel to the corner, can, however, absorb contraction loads without some repulsion of metal fingers 42" is required at the corner, and therefore no metal fingers are used as a connection between the cladding part 18a at the corner and the container wall or the ship's hull in this modification.

The corner construction in fig. 8 is otherwise similar to that in fig.

2 showed, and essentially the same elements are used except that a veneer plate 86 is used at the corner to support the foam insulation layers 14" and 16" at the corner instead of the metal baffle plate 66 of fig. 2. Such a corner-repelling plate 86 is mounted on studs which are connected to the interior of the ship's hull 12.

From the foregoing, it can be seen that the invention provides an improved corner structure which supports the primary cladding in a cryogenic insulation system for tanks and ships and which is specially designed to be able to transfer loads in different directions from the primary membrane to the interior of the ship's hull. A simple construction is used which mainly consists of a number of parallel bands which significantly reduces the complexity of the foam insulation at the corner construction and reduces heat leakage to the cold contents of the container.

Although the cryogenic insulation system according to the invention is particularly effective for use in ships or tankers, this system can be used for any container for cryogenic liquids, including barges, storage tanks, aircraft or spacecraft. The thickness of the "3D" fibre-reinforced foam insulation in the system can be varied to limit the evaporation and adjusted according to the need and the special design.

Although particular embodiments have been described for illustration purposes, it is easy to understand that other modifications and variations will be obvious to experts in the field, and the invention must not be considered as limited by these, but lies within the scope of the appended patent claims.

Claims (9)

1. Corner construction for a gas container for cryogenic liquefied gas, where the container has a wall or walls with corners and a metal lining resistant to low temperatures within the container wall as well as a heat insulating layer arranged between the metal lining and the container wall, where the insulation layer comprises at least a foam layer which is reinforced with fibres, characterized in that the corner construction comprises an angular on familiar food element (22) of metal which is resistant to low temperatures and is formed by two plate parts which meet each other at an angle at one of the container wall (12) corners, and where each plate part has free ends arranged between the metal lining (18) and the heat insulation layer (16) ), that the angle element (22) is anchored in the container wall (12) by means of several oblong or elongated metal strips (36,4 2) each of which is connected to one of the plate parts and runs essentially parallel to the plane of the plate part which metal- the strip is connected to, so that the metal strips (36,42) form an extension of the plate with which the strips are connected to transfer loads from the metal lining to the container wall (12). 2. Construction according to claim 1, characterized in that the said number of metal strips (36,42) comprises a first row of separated essentially parallel strips and a second row of separated essentially parallel strips, where the second row of strips is essentially in the plane of the outer surface of the second of the plate parts, where at least one of the rows of parallel strips is within at least one fibre-reinforced insulation layer (14,16). 3. Construction according to claim 2, characterized in that the second row of strips is offset in relation to the first row of strips. 4. Construction according to claim 1, 2 or 3, characterized in that the metal strips (36, 4 2) are connected to the angle element by welding connections. 5. Construction according to claim 1,2,3 or 4, characterized in that the metal strips (36,42) are connected to the wall of the container with an element comprising a T-fastening piece (52) with devices for connecting the metal strips to the fastening piece (52 ), and devices that connect the T-fastening piece (52) to the wall (12) of the container. 6. The construction according to one of claims 2-5, characterized in that the corner is a 90° corner, that the angle element (22) is a 90° element, and that the first row of strips forms a 90° angle with the second row of strips. 7. Construction according to one of claims 2-5, characterized in that the corner forms an acute angle, that the angle element (22) forms a corresponding angle, and that the first row of strips forms an acute angle with the second row of strips. 8. Construction according to one of claims 2-5, characterized in that the corner forms an obtuse angle, that the angle element (22) forms a corresponding angle, and that the first row of strips is arranged at a corresponding angle with the second row of strips. 9. Construction according to one of the preceding claims, characterized in that the construction comprises a support part (74) of veneer which is connected to the insulating foam layer (16) at the corner.