GB2138551A

GB2138551A - Container for Storage or Transport of Liquefied Gases

Info

Publication number: GB2138551A
Application number: GB8310573A
Authority: GB
Inventors: Terence Cotgreave
Original assignee: SHELL INT RESEARCH; Shell Internationale Research Maatschappij BV
Current assignee: SHELL INT RESEARCH; Shell Internationale Research Maatschappij BV
Priority date: 1983-04-19
Filing date: 1983-04-19
Publication date: 1984-10-24
Also published as: GB8310573D0

Abstract

The invention relates to a container for storage or transport of liquefied gases of which the heat- insulating lining comprises a plurality of discrete elements 2, 3 made of heat-insulating material arranged in a number of layers along the rigid outer shell 1, wherein the adjacent faces of the elements of at least the inner layer and the elements of the layer adjacent thereto are interconnected by means of a mastic which forms a continuous barrier 8 between said adjacent layers of elements, and wherein the remaining faces of at least the elements of the inner layer are not interconnected. The mastic includes a cured epoxy resin reinforced with milled glass fibre material. <IMAGE>

Description

SPECIFICATION Container for Storage or Transport of Liquefied Gases The invention relates to a container for storage or transport of liquefied gases having a rigid outer shell internally lined with a heat-insulating lining.

It is the.object of the invention to provide a container for storage-or transport of liquefied gases having a rigid outer shell internally lined with a heat-insulating lining which can be applied in a simple manner, wherein the heat-insulating lining is able to contain liquefied gas.

For this purpose the container for storage or transport of liquefied gases according to the invention has a rigid outer shell internally lined with a.heat-insulating lining, which lining comprises a plurality of discrete elements made of heat-insulating material arranged in a number of layers along the rigid outer shell, wherein the adjacent faces of the elements of at least the inner layer and the elements of the layer adjacent thereto are interconnected by means of a mastic in such a manner that the mastic forms a continuous barrier between said adjacent layers of elements, and wherein the remaining faces of at least the elements of the inner layer are not interconnected.

The advantage of using such elements of heat- insulating material is that the said elements can be prefabricated under controlled conditions, so that the elements are of constant quality.

The invention will now be described by way of example in more detail with reference to the drawings, wherein: Figure 1 shows a perspective view of a fragment of a heat-insulated rigid outer shell of a container for storage of liquefied gas according to the invention; Figure 2 shows a horizontal cross-section of a fragment of the heat-insulated rigid outer shell according to Figure 1 and indicates the deformation of the heat-insulating lining at cryogenic conditions; Figure 3 shows a perspective view of an element of heat-insulating material provided with a piece of woven glass fibre cloth; and Figure 4 shows a horizontal cross-section of a fragment of a heat-insulated rigid outer shell of a container for storage of liquefied gas according to an alternative embodiment of the invention.

Figure 5 shows a vertical cross-section of a fragment of a heat-insulated rigid outer shell of a container for storage of liquefied gas according to another alternative embodiment of the invention.

In Figure 1 reference numeral 1 refers to a fragment of a steel rigid outer shell of a container for the storage of liquefied gas, for example liquefied natural gas. The outer shell 1 is internally lined with a heat-insulating lining. The heatinsulating lining comprises an outer layer of discrete elements 2 and an inner layer of discrete elements 3, wherein the layers are arranged along the outer shell 1. The discrete elements 2 and 3 are blocks of polyurethane foam. During normal use of the container, the elements 3 of the inner layer are in.direct contact with the liquefied gas which is stored in the container at cryogenic conditions at about atmospheric pressure.In the case of natural gas the temperature of the liquefied gas is about 600C, and the temperature in the heat-insulating lining ranges from -1 600C at the inner faces of the elements 3 to little below ambient temperature near the outer shell 1.

The elements 2 of the outer layer are connected tp the inner face of the rigid outer shell 1 by a continuous layer 5 of mastic. Moreover the elements 2 are connected to each other by layers 6 of mastic, applied on the faces of the elements 2 which are perpendicular to the outer shell 1.

The elements 3 of the inner layer are connected to the inner faces 7 (see Figure 2) of the elements 2 of the outer layer by a continuous layer 8 of mastic. However, the faces of the elements 3 which are perpendicular to the rigid outer shell 1 are not interconnected. This is done to allow deformation of the elements 3 when the elements are cooled down as the cold liquefied gas enters into the container.

The deformation of the elements 3 at cryogenic conditions is shown in Figure 2 wherein the dotted lines indicate the situation at ambient temperature. For the sake of clarity, Figure 2 has been drawn to a scale which is larger than the scale of Figure 1, and the deformation of the elements 3 has been exaggerated.

The deformation of the elements 3 of the inner layer will prevent the thermal stress in the elements 3, arising when such an element is cooled down, from exceeding the limit above which the elements will fracture. It will be appreciated that fracturing of an element 3 of the inner layer should be prevented as this leads to disintegration of that element which in its turn may lead to fracture of the layers 8 and 2 and may cause a cold spot on the outer shell 1 of the container and subsequently rupture of the outer shell 1.

Since the elements 3 of the inner layer are not connected to each other, the inner layer cannot contain the liquefied gas stored in the container.

To contain the liquefied gas, the layer 8 of mastic should be a continuous barrier which is liquidand vapour-tight at temperatures of about -1600C.

For this purpose, the mastic is formed by a mastic base composition, including an epoxy resin and milled glass fibre material, which is blended prior to the application of the mastic with a curing composition, so that thereafter the mastic will harden or cure. An example of a suitable mastic will be described with reference to the Table.

TABLE

Amount in Component Kg epoxy resin 67 flexibilizer 33 mastic base milled glass fibre composition material 40 surfactant 1 thixotropic agent 3 curing curing agent 31 composition thixotropic agent 3 The epoxy resin is Epikote 828 (registered trademark), a condensate of bisphenol A and epichlorohydrin. The flexibilizer, included to improve the flexibility of the cured mastic, is Flexibilizer 151 (registered trademark), a high molecular weight aliphatic glycidyl ether, or an equivalent material to wit Heloxy WC-84 (registered trademark).The milled glass fibre material comprises glass fibres having lengths in the range of from 0.2 mm to 2.0 mm;-the preferred lengths are in the range of from 0.5 mm to 0.7 mm. Preferably the fibres have been treated with a resin compatible size. In order to improve the fracture toughness of the layer of mastic, the amount of milled glass fibre material in the mastic base composition, wherein the amount of epoxy resin and flexibilizer equals 100 kg, is selected in the range of from 20 kg to 90 kg; the preferred amount is in the range of from 30 kg to 60 kg. The mastic base composition preferably includes a surfactant, for example Borchigol E2 (registered trademark) which is a resin modified mineral oil. The amount of surfactant in the mastic base composition, wherein the amount of epoxy resin and flexibilizer equals 100 kg, is at most 3 kg.The mastic composition can be prepared in advance and it can be stored until it is to be used. To stabilise the mastic base composition when it is stored, in order to avoid segregation of the milled glass fibre material from the mastic base composition, the thixotropic agent is added to the mastic base composition. The thixotropic agent is Aerosil 380 (registered trademark), a colloidal, amorphous silicon dioxide, and the amount of thixotropic agent in the mastic base composition, wherein the amount of epoxy resin and flexibilizer equals 100 kg, is at most 10 kg; the preferred amount is in the range of from 1 kg to 5 kg.

The curing composition includes a curing agent, Epikure 114 (registered trademark), based on cycloaliphatic amines, and a thixotropic agent, to wit the above-mentioned Aerosil 380 (registered trademark). The function of the thixotropic agent is to alter the viscosity of the curing composition in such a manner that it matches the viscosity of the viscous mastic base composition. The amount of thixotropic agent in 'the curing operation, wherein the amount of curing agent equals 31 kg, is at most 5 kg; the preferred amount is in the range of from 1 kg to 4 kg. The curing composition can be prepared in advance and stored until it is to be used.

If required, a small amount of water can be included in the curing composition.

Pigments can be included in the mastic base composition and in the curing composition in sufficient quantities to generate readily seen colours that merge to, for example, a green colour on mixing the mastic base composition and the curing composition.

To avoid cracks arising in the elements 2 of the outer layer and the layer 8 of mastic, the inner faces 7 of the elements 2 can be provided with pieces of woven glass fibre cloth 11 (see Figure 3), wherein the size of each piece preferably equals the size of the corresponding inner face 7.

The pieces of woven glass fibre cloth 11 are attached to the inner faces 7 by a cured epoxy resin which is suitable for being used at cryogenic conditions. A suitable epoxy resin comprises 67 kg epoxy resin, 33 kg flexibilizer, 31 kg curing agent and 3 kg thixotropic agent, wherein the components have been described hereinabove.

It will be appreciated that the pieces of fibre cloth can as well be attached to the outer faces 12 (see Figure 2) of the elements 3 of the inner layer.

An alternative embodiment of the invention is shown in Figure 4. In this embodiment the layer 8 of mastic is reinforced with a continuous laminate 1 3 comprising one or more layers of glass fibre material. The continuous laminate 13 is applied to the inner faces 7 of the elements 2 prior to the application of the layer 8 of mastic. The continuous laminate 1 3 can either comprise woven glass fibre cloth joined to the inner faces 7 by a cured epoxy resin, or a layer of cured epoxy resin reinforced with chopped glass fibre material.

In the latter case, the layer of resin is sprayed on the inner faces 7 and the chopped glass fibre material is blown on this layer in such a manner that the chopped glass fibre material becomes fuliy incorporated in the resin before the resin is cured. The chopped glass fibre material comprises fibres having lengths in the range of from 10 mm to 100 mm and which have been treated with a resin compatible size. A suitable resin is the resin as described hereinabove with reference to Figure 3.

In an alternative embodiment of the invention the faces of the elements 2 perpendicular to the outer shell 1 are not interconnected.

The invention is not restricted to an outer shell 1 internally lined with elements of heat-insulating material arranged in two layers as described with reference to Figures 1, 2 and 4. Instead the heatinsulating lining may comprise three layers, or if required four or five layers. When there are three or more layers, the layer of elements which is in direct contact with the liquefied gas is referred to as inner layer, in order to distinguish this layer from the other layers of elements which are not in direct contact with the liquefied gas. The latter layers are referred to as outer layers.

When the heat-insulating lining comprises three or more layers of elements, each pair of adjacent layers of elements can be provided with a continuous barrier of mastic joining the elements of the layers.

In order to protect the elements of polyurethane foam from catching fire during the construction phase of the container, for example as a result of welding, at least the inner faces of the elements of at least the inner layer can be provided with a layer of fire protection coating material. The fire protection coating material can be an intumescent coating material, such as Firec (registered trademark), or a sublimatory coating material, such as Thermolag (registered trademark).

The rigid outer shell of the container may be flat or curved, for example cylindrical, or spherical.

It will be appreciated that in that case the shape of the elements should be selected in such a manner that the elements conform to the curved outer shell.

The invention is not restricted to block-shaped elements as described with reference to Figures 1, 2, 3 and 4. Instead any suitable prismatic shape can be used. An example of an heatinsulating lining comprising prismatic elements of heat-insulating material is shown in Figure 5. The rigid outer shell 21 of a container for the storage of liquefied gas is internally lined with a heatinsulating lining comprising an outer layer of elements 22 and an inner layer of elements 23.

The elements 22 and 23 are prismatic elements of which the cross-section parallel to the plane of the drawing of Figure 5 is a parallelogram and of which the cross-section parallel to the rigid outer shell 21 is rectangular or square. The elements 22 of the outer layer are connected to the inner face of the rigid outer shell 21 by a layer 25 of mastic and the elements 23 of the inner layer are connected to the inner faces 27 of the elements 22 by a continuous layer 28 of mastic.

In a further embodiment of the invention horizontal baffles, preferably in the form of aluminium sheets are arranged on each horizontal row of elements of the inner layer. The baffles will prevent the liquefied gas stored in the container from moving in a vertical direction through vertical conduits formed by the V-shaped gaps between the vertical faces of the elements which are perpendicular to the rigid outer shell.

It will be appreciated that when the elements are small arranging the baffles on every second or third row of elements of the inner layer will suffice, provided that the horizontal baffles are arranged at least one horizontal row of elements of the inner layer. Moreover the invention is not restricted to baffles in the form of aluminium sheets, also sheets of other suitable metals can be used or foils of these metals. Instead it is also possible to use laminates of polyurethane glass cloth or epoxy glass cloth, or woven fabric of polyester or of cellulose fibres can be applied.

The invention is not restricted to prismatic elements having a rectangular or square crosssection as-described with reference to Figure 5.

Instead the elements may be of any suitable shape, for example the prismatic elements may be triangular or polygonal prisms.

The invention is not restricted to an outer shell made of steel; if desired the outer shell can be made of any other suitable material, for example concrete.

The invention can be used as well in containers in which the liquefied gas is stored in an inner tank within the rigid outer shell, and wherein the liquefied gas is only in direct contact with the heat-insulating lining in case of a failure or leakage of the inner tank.

By not interconnecting the faces of the elements of the inner layer to each other, the thermal stresses in these elements are kept below the limit above which the element will fracture. To reduce the thermal stresses in the elements of the inner layer even further, the ratio of the length of an element over its thickness is selected in the range up to 4, preferably this ratio is in the range of from 1 to 2. In the claims, this ratio is referred to as "aspect ratio".

The invention is not restricted to elements made of polyurethane foam. The elements can be made of other suitable heat-insulating materials, for example gas expanded polymer foam, syntactic foam or foam glass, as well.

A suitable size of the elements is such that the elements can be handled easily by the workmen fitting the elements, for example elements having a length of 150 mm, a width of 150 mm and a thickness of 75 mm.

Claims

1. Container for storage or transport of liquefied gases having a rigid outer shell internally lined with a heat-insulating lining, which lining comprises a plurality of discrete elements made of heat-insulating material arranged in a number of layers along the rigid outer shell, wherein the adjacent faces of the elements of at least the inner layer and the elements of the layer adjacent thereto are interconnected by means of a mastic in such a manner that the mastic forms a continuous barrier between said adjacent layers of elements, and wherein the remaining faces of at least the elements of the inner layer are not interconnected.

2. Container as claimed in claim 1, wherein each pair of adjacent layers of elements is provided with a continuous barrier of mastic interconnecting the elements of the layers.

3. Container as claimed in claim 1 or 2, wherein the elements of adjacent layers are arranged in a staggered fashion relative to each other.

4. Container as claimed in any one of the claims 1-3, wherein the elements are made of gas expanded polymer foam.

5. Container as claimed in any one of the claims 1-4, wherein the elements are made of polyurethane foam.

6. Container as claimed in any one of the claims 1-5, wherein the mastic includes a cured epoxy resin reinforced with milled glass fibre material.

7. Container as claimed in any one of the claims 1-6, wherein the inner face of each of the elements of at least the outer layer adjacent to the rigid outer shell is provided with a piece of woven glass fibre cloth joined to the inner face by a cured epoxy resin.

8. Container as claimed in any one of the claims 1-7, wherein the outer face of each of the elements of the inner layer is provided with a piece of woven glass fibre cloth joined to the outer face by a cured epoxy resin.

9. Container as claimed in any one of the claims 1-8, wherein a continuous laminate of glass fibre material is applied to the inner faces of the elements of at least the outer layer adjacent to the rigid outer shell.

10. Container as claimed in claim 9, wherein the continuous laminate comprises one or more layers of woven glass fibre cloth joined to the inner faces of the elements by a cured epoxy resin.

11. Container as claimed in claim 9, wherein the continuous laminate comprises a layer of a cured epoxy resin having chopped glass fibre material incorporated therein.

12. Container as claimed in any one of the claims 1-11, wherein at least the inner faces of at least the elements of the inner layer are provided with a layer of fire protection coating material.

13. Container as claimed in any one of the claims 1-12, wherein the elements are prismatic.

14. Container as claimed in claim 13, wherein the elements are blocks.

15. Container as-claimed in any one of the claims 1-14, wherein the dimensions of the elements of the inner layer are selected such that the aspect ratio is in the range up to 4.

1 6. Container as claimed in claim 15, wherein the aspect ratio is in the range of from 1 to 2.

17. Container as claimed in any one of the claims 1-15, wherein a horizontal baffle is arranged on at least one horizontal row of elements of the inner layer.

1 8. Container as claimed in claim 17, wherein.

the baffie is made of aluminium foil.

19. Container substantially as described with particular reference to the accompanying drawings.