NO119745B - - Google Patents

Description

Container for cold liquids.

The present invention relates to containers in which a membrane tank is supported in an insulated housing, and the invention relates more particularly to containers for storing cold liquids,

f.ke.'s liquefied gases as liquefied "natural gas".

Containers for very cold liquids have been proposed where the tank containing the liquid is of the so-called membrane type, i.e. it is supported by an outer housing or a surrounding mantle and is not self-supporting. It has been proposed to supply such membrane tanks with a large excess of metal in all directions (such as corrugations extending in the transverse direction), which excess is taken up when the tank contracts from the ambient temperature to the low temperature of the liquid. Such tanks generally have a rather complicated construction and precautions must be taken to prevent excessive stresses occurring at the points where the corrugations intersect and to prevent inadmissible stretching (with resulting possible deformations or breaks) as a result of the hydrostatic load.

It has now been found that by making use of different metals for which the ratio between elastic stress and elastic stress over the temperature range to which the metals are exposed, and especially at low temperatures, is equal to or greater than one, can the construction of the tank is simplified to a considerable extent because it then only becomes necessary to arrange excess metal in the form of corrugations in one direction in each of the tank's walls.

The present invention relates to a container of the aforementioned type, i.e. a container comprising an outer housing of heat-insulating material in which a membrane tank is arranged and fully supported, the walls of which are lined with a plurality of corrugations which do not intersect each other and each of which extends continuously from one edge of a wall to the opposite edge. The characteristic feature of the container according to the invention is that the walls of the tank are lined with a material in which the ratio between elastic stress and thermal stress over the temperature range to which the tank is exposed is at least equal to one, and in that each corrugation butts together with a corrugation in the adjacent wall and is connected to this by means of a transverse corrugation in an angular strdaiimel which is tightly fixed to the inside of the tank where the adjacent walls butt together.

By elastic tension, here is meant the maximum tension to which the material can be subjected when, when the tension ceases, it will approximately return to its original dimensions. In practice, this is very close to the yield point, i.e. the stress at which the material is permanently deformed. Thermal stress is to be understood as the stress that occurs at a specific temperature if the material's dimensions are maintained unchanged when the material is subjected to cooling from the ambient temperature to the relevant low temperature. For some materials, the ratio between elastic stress and thermal stress is less than one at the outer limits of the temperature range, and it is an essential feature of the invention that this is greater than one, e.g. 1.2.

Examples of suitable metals that have a ratio between elastic stress and thermal stress of at least 1.2 are most stainless steels, Invar { J& fc Ni-steel), 9# Ni-steel, Inconel-X, K-Monel,

and certain aluminum alloys. A typical thickness for the walls is between 0.5 and 1.0 mm.

The membrane tank, i.e. a tank made of a material which does not have sufficient strength to bear loads ..to which it is subjected, preferably has the shape of a hexahedron or a hexahedron in which the lower parts of a pair of opposite side walls are tapered towards the bottom wall. However, the idea can have other forms and can e.g. be cylindrical but cannot be spherical.

The outer housing can be made of wood, e.g. balsa wood or quippo;

or of plastic, e.g. rigid or semi-rigid foam plastic with essentially closed cells, such as e.g. polyurethane, polystyrene, polyethylene, polyvinyl chloride or foamed epoxy plastic.

The tank must be completely supported in the insulating material

house, e.g. against hydrostatic loads. This can be achieved

by means of attachment means to the housing or to or near the edges

of the tank walls. These bodies can e.g. be made of wood or metal, and preferably a plurality of bodies should be arranged with spaces between them near or along the edges of the walls. If the organs are made of a material that has a relatively high coefficient of thermal expansion, the organs must not have too large dimensions so that they do not undergo significant changes in shape when the tank is in use. If the organs are wooden, small bolts or screws can be welded or otherwise attached to or threaded through the membrane tank, which bolts or screws can in turn be attached to the organs. If the organs are made of metal, they can be welded or soldered directly to the membrane tank and can e.g. have the form of angle brackets. The organs can easily be attached to the outer haaj\ by means of screws or bolts, or by means of other methods depending on the nature of the house.

Another method for supporting the rr.ernbrantanken

in the house, which can possibly be used in addition to the aforementioned, involves extending parts of adjacent tank walls past the corners so that the tongues formed by the extended wall sections can be fixed between fastening devices or so that the said tongues extend into slots arranged in the outer house. If desired*, the whole of one of two walls that butt together can extend past

the corner" as this wall is made with slots at intervals near the extended edge of the wall to permit the piercing of tongues from the other plates. In order to reduce varsae overlining, it is desirable that the extended parts of the walls are thermally insulated. If therefore they. extended parts are retained between fastening means, these means can be suitably made of heat-insulating material, e.g. wood* If, however, the extended parts of the walls stick into slots in the insulated house, the extended parts of the walls between the tank and the house must be thermally insulated , e.g. in that they are surrounded by wooden blocks.

If the depth of the tank is relatively large, e.g. more than 6 metres, it is desirable to support the walls, especially the side walls, in addition to the support they receive near the edges of the walls. Thus, e.g., the outer house can be. executed down a plurality of mounting blocks in which there are Inskcgdd bolts or screws which are passed through holes in the middle parts of the tank walls. The holes in the tank walls can be sealed by attaching or soldering a cover over the head of the bolt or by using a bolt with a flange, the edge of which is welded or soldered to the wall. The arrangement of mounting blocks for supporting the inner parts of the walls is particularly desirable if it is necessary to mount various objects [fom e.g. pumps in the tank.. The bolt or fastening device can appropriately in such a case* form a seat for the pump.

A plurality of corrugations which do not intersect extend across the tank walls so that they essentially cover the walls. In practice, this will mean that the corrugations on each tank wall are approximately parallel. These walls are not made with rows of transverse corrugations, i.e. at right angles to each other, as previously suggested. In any case, the bridge corrugations will not be limited to one part of the wall. In some cases, e.g. if the wall is not square or rectangular, it may be desirable to arrange the corrugations at a small angle in relation to each other, so that they e.g. proceeds somewhat divergently.

The corrugations can have any desired profile, i.e. they can be symmetrical (e.g. simple folds or waves) or asymmetrical (e.g. V-shaped in that one slanted surface is wider than the other slanted surface in the corrugation ). Preferably, the corrugations protrude into the tank, but in a car trap it would possibly be desirable to let the corrugations protrude from the tank, provided that the clearance between the tank walls and the housing is large enough.

In order for the corrugations in one wall to butt together with the corrugations in adjacent walls, at least one of the walls, e.g. the bottom wall of the tank preferably has corrugated rings which end at all edges of this wall. If this wall is square or rectangular, the corrugations must be arranged at an angle to the edges and all corrugations cannot be parallel to e<»>n of the edges of the wall. If the wall has another ferm, e.g. pentagonal or hexagonal, the corrugations will also have to be

arranged at an angle with at least one of the edges and in some cases slightly divergent.

If one or more of the walls is made with corrugations which are arranged so that they enclose all edges of the wall or walls, it is not necessary that the walls abutting this or these walls have such a special arrangement. In these adjacent walls, the corrugations can often be parallel to a pair of opposite edges of the wall.

A corrugation should preferably not form a corner in any of the walls where three sides meet, i.e. none of the corrugations in any wall should be diagonal. The reason for this is that in such a case the corner must necessarily be corrugated and this makes it difficult to secure the tank in this insulated house.

When manufacturing the membrane tank, the walls can be put together so that separate plates are connected to each other along their corrugations. A series of plates with upturned edges along a pair of opposite side edges can be connected to each other so that the corrugations are formed by raised edges which are welded together along the edges. If desired, such plates can of course already be made with one or more corrugations that extend across the plate between the upwardly bent edges. Alternatively, plates with one or more corrugations can be connected to each other along their edges so that the joints in the composite wall run across the corrugations or run between adjacent corrugations.

The angular strips are preferably made of metal and are attached to the inside of the tank to adjacent bearings ± hjcrr.^r.a.

These strips are preferably attached by welding or soldering.'

It is only necessary to arrange angle strips jlpngs the corners where corrugations in adjacent walls collide: Preferably, however, angle strips are attached to the tank walls at all corners as this makes fixing the tank in the house much easier. To ensure that the angle strip can form a liquid-tight seal and to prevent inadmissible stresses from occurring, the strips at the corners where corrugations in adjacent plates collide must be provided with transverse corrugations that match the corrugations in the walls.

So that the stresses that occur when the angle strips expand

and pull together must be minimal, and likewise to facilitate production, the transverse corrugations must run without lallar with minimal deflection in the direction across the strip. As the strip itself is bent at an angle, generally 90°, the corrugations must of course be bent in a corresponding way. It is therefore desirable when drawing the tank that the inclination of the corrugations in adjacent walls is carried out so that the corrugations, when they extend from one wall to the next, change their direction as little as possible. In some cases this will mean that the corrugations in one of a pair of adjacent walls must run at right angles to the longitudinal axis of the common corner and in other cases at an acute or obtuse angle in relation to the said longitudinal axis.

To ensure that the corrugations are maintained during welding or soldering, especially when the angle strips are attached to the edges of adjacent walls, it is recommended that a strip of non-fusible material is inserted, e.g. asbestos on the inside of the corrugations in the place where the welding is to take place before the foot icing or soldering is carried out. This will prevent the entire wall around the corrugation from melting together and rendering the corrugation ineffective.

If it is desired, the top wall of the membrane tank should not be flush with the side walls of the tank and can e.g. consist of a wall of a completely different construction. In such cases, it is necessary that the corrugations in the side walls end in the walls because they reach the upper edges of the walls. In these cases too, it is desirable that the bottom wall has corrugations that end at all edges of the bottom wall.

In other cases, one can e.g. when the tank is made with a trunk, the corrugations can, if desired, end in the top wall near the bottom of the trunk and the trunk itself can have one or more peripheral corrugations. The other walls in such a tank will of course have non-intersecting corrugations which extend across each wall and meet the corrugations in an adjacent wall.

The container according to the invention is very suitable for storing liquefied gases, i.e. gases that boil at a temperature below the ambient temperature at atmospheric pressure. Examples of such liquefied gases are liquefied butane, propane, ethylene, metal, oxygen, nitrogen and ammonia.

In the following, the invention will be described in more detail in connection with the drawings (where

Fig. 1 shows a perspective view of part of the interior of

a container according to the invention.

Fig. 2 shows a section along the line 2-2 in fig. 1.

Fig. 3 shows a perspective view of the interior of a container which differs from that shown in fig. 1 and

Fig. 4 shows a perspective view^, of the interior of a part of

a large container differing from those shown in Figures 1 and 3"

According to fig. 1 and 2, the outer housing of heat-insulating material comprises blocks of polypropylene with essentially closed cells. The tank 2 has walls made of 0.5 cm thick invar and is supported in the house 1 by means of wooden blocks 3 attached to the house and the tank. The blocks are bolted to the housing and screws (not shown) are fast through the tank walls and into the blocks 3" The heads of the screws are welded to the tank to achieve a tight connection. These blocks are fixed at intervals only along the edges of the tank walls.

On the inside of the tank, there are arranged along all edges of the walls angle strips and 5 which are welded to the walls and completely cover the screws which are fast through the plates and into the blocks 3. The angle strips 4 are provided with transverse corrugations 6 which run flush with the corrugations in the adjacent walls. In the vertically arranged angle strips 5, there are no transverse corrugations, as these strips do not come into contact with the corrugations in the walls.

The bottom wall 7 of the tank is lined with parallel corrugations

8 which runs at an angle across the wall and abuts the corrugations 6 in the angle strips 4* The side walls have parallel vertically arranged corrugations 10 which likewise abut the transverse corrugations 6 in the angle strips 4*

The corrugations are formed by strips with raised edges being welded together along their edges. In this way, corrugations with a V-shaped profile are formed along the edges of adjacent plate strips.

According to fig. 2, the tank is provided from above with a trunk 11 made with a circumferential corrugation 12 in the side wall. Through the top of the trunk there are cables and gas valves (not

. shown) so that the tank can be used for storage and liquefied

In fig. 3 denotes corresponding reference numbers corresponding to parts as shown in the drawing's fig. 1. Parts of the tank and an angle strip1 have been broken away to show the procedure for attaching the tank to the housing.

According to this embodiment, the tank is attached to the housing 1 in a different way than that described in connection with fig. 1

and 2. Angle brackets 20 are welded together with mutual spaces along the edges of the tank walls 7 and 9. These brackets are greased in slots 21 in the housing. As further support, the ends of the walls are elongated in the form of tongues that fit into slots in the house 1.

The figure shows tongues 22 where one of these tongues 22 is shown inserted into the slot 23 in the housing 1. Dashed lines show an extension of a tongue 24 which extends across the bottom wall 8. This tongue 24 enters the slot 25 in housing 1. Blocks of heat-insulating material 26 are arranged around the brackets 20. Similar insulating blocks surround the tongues 22 and 24, but for the sake of clarity these blocks are omitted from the drawing.

In fig. 4 shows corresponding reference numbers accordingly

move as in fig. 3"

According to this embodiment, the side walls of the tank are made with corrugations 31 s°m extending obliquely in relation to vertical lines. These corrugations and the corrugations 30 in the bottom wall 7 differ somewhat from those shown in fig. 1 to 3 ^ the profile of the corrugations is arc-shaped and not V-shaped. The vertical angled ice strip 33 has one transverse corrugation 32. Further support of the tank walls is achieved by means of bolts 35. These bolts 35 are passed through a hole in the wall and are fixed in threads in a mounting block (not shown) which is attached to the outer house 1 behind walls 7 and 9. To seal the wall, the bolts are made with flanges 34 nvis edges are welded to the wall. In order to reduce thermal stresses, the bolts 35 are placed at the center of the various plates from which the tank walls are built.

Claims (2)

1.. Container comprising an outer housing of heat-insulating material in which is arranged and fully supported a membrane tank, the walls of which are lined with a plurality of non-intersecting corrugations each extending continuously from one edge of a wall to the opposite edge , characterized in that the tank's (2) ye*gl%|]( 7 > 9) is executed by a matlsr? iale in which the ratio between elastic stress and thermal stress over the temperature range to which the tank is exposed is at least equal to one, and in that each corrugation abuts a corrugation in the adjacent wall and is connected to this by means of a transverse corrugation in an angular strip which is tightly attached to the inside of the tank where the adjacent walls collide• 2. Container as stated in claim 1, characterized in that the corrugations in all walls are at an angle in relation to the edges of the walls, with at least some corrugations extending from one edge of the wall at an angle to the adjacent edge of a wall.