AU2012228180B2

AU2012228180B2 - Insulating block for producing a tight wall of a tank

Info

Publication number: AU2012228180B2
Application number: AU2012228180A
Authority: AU
Inventors: Jean-Francois Auboin
Original assignee: Gaztransport et Technigaz SA
Current assignee: Gaztransport et Technigaz SA
Priority date: 2011-03-15
Filing date: 2012-02-16
Publication date: 2016-06-09
Anticipated expiration: 2032-02-16
Also published as: CN103443526A; FR2972719B1; AU2012228180A1; FR2972719A1; KR20140015474A; WO2012123656A1; CN103443526B; KR101919869B1

Abstract

The invention relates to an insulating block (7) to be arranged in a repeat pattern on a secondary tight membrane (5), said block comprising a free-standing casing (20) filled with a heat-insulated lining. A base panel (21) of the free-standing casing extends continuously over the entire surface of the casing facing away from the cover panel. A layer of insulating material (30) is fixed to the outer surface of the base panel of the free-standing casing, the thickness of the layer of insulating material being higher than the height of the raised lateral edges (13) and welding supports (11) for the secondary tight membrane, parallel grooves (31) being formed in the layer of insulating material (30) in order to receive raised lateral edges (13) and welding supports (11) for the secondary tight membrane. The invention is applicable to liquefied natural gas reservoirs.

Description

INSULATING BLOCK FOR THE FABRICATION OF A SEALED TANK

WALL

The invention relates to the field of the fabrication of sealed and insulating tanks, in particular for containing cold or hot liquids, and more particularly to tanks for storing and/or transporting liquefied gas.

In the field of the maritime transportation of liquefied gases, notably gases with a high methane content, there is known a membrane tank intended to contain a cold liquid and constituted of tank walls secured to the supporting structure of a ship, the tank walls including, in the direction of the thickness from the exterior toward the interior of said tank, an insulating secondary barrier secured to the supporting structure, a sealed secondary membrane secured to the insulating secondary barrier, an insulating primary barrier secured to the sealed secondary membrane, and a sealed primary membrane secured to the insulating primary barrier. In the document FR-A-2867831, among others, there has been described a tank of this type in which the two sealed membranes include a continuous layer of strips made of steel with a low coefficient of expansion that are welded in sealed manner by their lateral raised edges to parallel weld supports and the two insulating barriers are produced with the aid of self-supporting wooden boxes filled with a thermally insulative packing and juxtaposed in accordance with a repeated pattern.

In service, the boxes of the tank wall are subjected to compression forces caused by static pressure and dynamic impacts of the fluid contained in the tank, which is moved notably by the rolling and pitching of the ship. The boxes must resist these forces over a long service life, given the risks of the membrane rupturing if an underlying box collapses and the cost of replacing a box.

However, in the aforementioned tank, the production of notches in the bottom panel and in the internal partitions of the box forming the insulating primary barrier to accommodate the projecting portions of the sealed secondary membrane has the effect of weakening the box by forming in these partitions potential starting points for cracks. FR-A-2781557 discloses a sealed and insulated tank in which a foam panel is disposed on the hull of a ship. A sealing primary barrier on which no insulating material rests includes weld supports and strips with lateral raised edges welded to these weld supports.

In accordance with one embodiment, the invention provides an insulating block for the fabrication of a sealed and insulating tank wall, the insulating block being intended to be disposed in accordance with a repeated pattern on a sealed secondary membrane of the tank wall to form an insulating primary barrier of the tank wall, the insulating block including a self-supporting box filled with a thermally insulative packing, the self-supporting box including a cover panel adapted to form a support surface for a sealed primary membrane of the tank wall, a bottom wall arranged opposite the cover panel, and lateral walls extending between the bottom panel and the cover panel to define an interior space of the box filled with the thermally insulative packing, wherein the bottom panel of the self-supporting box extends continuously over all the surface of the box facing away from the cover panel, and the insulating block includes a layer of insulating material, for example synthetic material, fixed to the exterior surface of the bottom panel of the selfsupporting box, the thickness of the layer of insulating material being greater than the height of the lateral raised edges and the weld supports of the sealed secondary membrane, parallel grooves being formed in the layer of insulating material to receive lateral raised edges and weld supports of the sealed secondary membrane .

In accordance with embodiments, such an insulating block may have one or more of the following features: - the insulating block has the overall shape of a rectangular parallelepiped. - the self-supporting box includes parallel spacers arranged in the interior space of the box to compartmentalize the interior space of the box, the longitudinal ends of the spacers being fixed to the lateral walls. - the parallel spacers have a constant thickness. - the thickness of the parallel spacers is less than or equal to 15 mm. - the layer of insulating material includes a polyurethane foam. - the layer of insulating material has a thickness greater than or equal to 35 mm. - an overall thickness of the insulating block is between 10 and 50 cm, preferably between 20 and 30 cm. - the layer of insulating material is stuck to the bottom panel.

In accordance with one embodiment, the invention also provides a sealed and insulating tank including a tank wall secured to a supporting structure, the tank wall including, in the direction of the thickness from the exterior toward the interior of the tank, an insulating secondary barrier secured to the supporting structure, a sealed secondary membrane secured to the insulating secondary barrier, an insulating primary barrier secured to the sealed secondary membrane, and a sealed primary membrane secured to the insulating primary barrier, each of the sealed membranes including a continuous layer of strips made of steel having a low coefficient of expansion that are welded in sealed manner by their lateral raised edges to parallel weld supports, wherein the insulating primary barrier is essentially constituted of a plurality of insulating elements juxtaposed in accordance with a repeated pattern, an insulating element including each time: a self-supporting box filled with a thermally insulative packing, the self-supporting box including a cover panel adapted to form a support surface for the sealed primary membrane of the tank wall, a bottom panel arranged opposite the cover panel, and lateral walls extending between the bottom panel and the cover panel to define an interior space of the box filled with the thermally insulative packing, the bottom panel of the self-supporting box extending continuously over all the surface of the box facing away from the cover panel, and a layer of insulating material arranged between the exterior surface of the bottom panel of the selfsupporting box and the sealed secondary membrane of the tank wall, the thickness of the layer of insulating material being greater than the height of the lateral raised edges and the weld supports of the sealed secondary membrane, parallel grooves being formed in the layer of insulating material to receive lateral raised edges and weld supports of the sealed secondary membrane.

In accordance with embodiments, the layer of insulating material may be fixed to the bottom panel of the selfsupporting box or not. If it is not fixed to this bottom panel, the layer of insulating material my simply be retained by clamping it between the bottom panel of the self-supporting box and the sealed secondary membrane of the tank wall.

In accordance with one embodiment, a slippage layer is arranged between the layer of insulating material and the sealed secondary membrane. Such a slippage layer that aims to reduce wear and the risk of deterioration of the sealed secondary membrane may be made of Kraft paper or wooden boards, for example.

Such a tank may be part of a terrestrial storage installation, for example for storing LNG, or installed in a coastal or deep-water floating structure, notably a methane tanker ship, a floating storage and regasification unit (FSRU), a floating production and storage and offloading (FPSO) unit, etc.

In accordance with one embodiment, a ship for transporting a cold liquid product includes a double hull and a tank as referred to above disposed in the double hull.

In accordance with one embodiment, the invention also provides a method of loading or offloading such a ship in which a cold liquid product is fed through insulated pipes from or to a floating or terrestrial storage installation to or from the tank of the ship.

In accordance with one embodiment, the invention also provides a transfer system for a cold liquid product, the system including the aforementioned ship, insulated pipes arranged so as to connect the tank installed in the hull of the ship to a floating or terrestrial storage installation, and a pump for driving a flow of cold liquid product through the insulated pipes from or to the floating or terrestrial storage installation to or from the tank of the ship.

One idea behind the invention is to provide a stronger self-supporting box that is easier to fabricate, notably at the level of its bottom panel, by eliminating the necessity to provide notches intended to receive projecting portions of the underlying sealed membrane .

Some aspects of the invention start from the idea of disposing a layer of insulating material between the self-supporting box and the underlying sealed membrane to accommodate projecting portions of the membrane in this layer of material. Some aspects of the invention start from the idea of producing this layer of material in modular fashion with the same dimensions as the self-supporting box so as to be able to prefabricate an insulating block incorporating both the self-supporting box and the layer of insulating material.

The invention will be better understood and other objects, details, features and advantages thereof will become more clearly apparent in the course of the following description of a plurality of particular embodiments of the invention given by way of illustrative and nonlimiting example only and with reference to the appended drawings.

In the drawings :

Figure 1 is a cutaway perspective view of a sealed and insulating tank wall in accordance with one embodiment.

Figure 2 is a view in section taken along the line II-II of an element of the insulating primary barrier of the tank wall from figure 1.

Figure 3 is a cutaway diagrammatic representation of a methane tanker ship tank and a terminal for loading/offloading this tank.

Referring to figure 1, there is seen an area of the double hull of a ship designated by the digit 1. The tank wall is composed successively in its thickness of an insulating secondary barrier 2 that is formed of parallelepiped-shaped insulating elements 3 juxtaposed on the double hull 1 and secured to the latter by secondary retaining members 4, then a sealed secondary membrane 5 carried by the insulating secondary elements 3, then an insulating primary barrier 6 formed of parallelepiped-shaped insulating elements 7 juxtaposed and secured to the sealed secondary membrane 5 by primary retaining members 8 themselves fixed to the secondary retaining members 4, and, finally, a sealed primary membrane 9 carried by the insulating primary elements 7.

The membranes 5 and 9 are identically constituted of a continuous layer of strips made of steel with a high nickel content, for example 36%, known as invar, which are welded in sealed manner by their lateral raised edges to parallel weld supports fixed each time to the cover panels of the insulating elements 3 and 7, respectively, as in the prior art.

For example, the insulating secondary elements 3 are produced in the form of plywood boxes filled with perlite or in other forms known to the person skilled in the art.

The insulating primary elements 7 are described next with reference to figure 2.

The insulating primary element 7 represented in figure 2 rests on the sealed secondary membrane 5, which is supported by an underlying insulating secondary element 2 of which only the cover panel 10 is represented. The weld supports 11 of the sealed secondary membrane 5 are secured to the cover panel 10 by virtue of being accommodated in parallel grooves 12 as in the prior art. The emergent portion of the weld support 11 and the raised edges 13 that are welded to it on either side form the projecting parts 14 of the sealed secondary membrane 5.

The insulating primary element 7 has the general shape of a rectangular parallelepiped with a length of approximately 1.2m, a width of approximately 1 m and a height of approximately 200 mm, for example. It includes a box 20 and a slab of insulating material 3 0 stuck or clipped or attached in any other way under the bottom panel 21 of the box 20. The box 20 is formed of plywood sheets clipped together. Four lateral webs 23 are fixed perpendicularly to the periphery of the bottom panel 21 and extend as far as the interior surface of the cover panel 22 so as to close off the interior space of the box 20 of parallelepiped shape. The cover panel 22 is preferably formed of two superposed sheets of equal thickness joined together. Fixing tenons 24 are stuck and stapled against the lateral webs 23. The fixing tenons 24 serve as bearing surfaces for the primary retaining members 8.

The box 20 includes parallel internal partitions 25 that are fixed perpendicularly to the bottom panel 21 and extend parallel to the two lateral webs 23 represented in figure 2 between the other two lateral webs not represented in figure 2, to which they are also fixed at both their ends. The partitions 25 are disposed at regular intervals along the lengthwise direction of the box 20. These internal partitions 25 divide the interior space of the box 20 into identical compartments 26 that are filled with a thermally insulative packing such as expanded perlite or any other appropriate material. Alternatively, it is possible to provide thicker and/or more dense internal partitions near the edges to reinforce the box.

The box 2 0 may also include a locating comb, not represented, arranged perpendicularly to the internal partitions 25 mid-way along their length, as in the prior art.

The slab 30 of insulating material has substantially the same length and the same width as the bottom panel 21 to which it is stuck or attached in some other way so as to cover completely the bottom panel 21 and the edge surface of the lateral webs 23. It may be made of polyurethane foam, optionally reinforced with glass fibers, or other synthetic materials, for example polystyrene, or natural materials, for example balsa wood. A criterion for selection of the insulating material is its good compression strength to prevent deterioration of the slab of insulating material or the box when in service.

The thickness of the slab 30 is greater than the height of the projecting portions 14 of the sealed secondary membrane 5. For example, the weld supports of the sealed secondary membrane 5 may have a nominal height of approximately 35 mm. Notches 31 are produced within its thickness so as to be able to accommodate these projecting portions 14 when the insulating element 7 is put into place on the sealed secondary membrane 5. In this way, these projecting portions 14 do not interfere with the bottom panel 21. The notches 31 do not necessarily extend the full thickness of the slab 30.

This design of the insulating primary element 7 has a number of advantages. Thanks to the continuous structure of the bottom panel 21, which may be made in one piece, the box 2 0 is stronger than prior art boxes of the same size. The internal partitions 25 that do not include notches are less liable to crack. For equivalent strength, they can therefore be made thinner than in prior art boxes.

Notches 31 may be produced very easily in the slab 30 at any required location. The positioning of the insulating primary elements 7 relative to the projecting portions 14 of the secondary membrane 5 can therefore be flexibly designed and adapted according to the requirements of the target application.

Moreover, for a given thickness of the insulating primary barrier 6, the box 20 of the insulating primary element 7 has lower internal partitions 25 and lateral webs 23, which increases their resistance to buckling. For the same strength, these webs and partitions can therefore be made thinner than in prior art boxes.

Generally speaking, the simple structure of the box 20 enables simplified fabrication. Table I gives dimensions of the components of the box 20 in a preferred embodiment. These values may be modified according to the requirements of the target application.

Table I

The thickness of the slab 3 0 may be increased within limits imposed essentially by the mechanical strength in compression and the overall thermal conductivity of the insulating primary barrier.

Other materials may be used to produce the box 20, notably synthetic resins.

With a combination of plywood for the box 2 0 and polyurethane foam for the slab 30, it has been found that with the same dimensions the insulating primary element 7 has thermal insulation characteristics similar to those of a prior art box of perlite.

The sealed primary membrane 9 may be fixed into grooves 32 of the cover panel 22 as in the prior art. The grooves 3 2 of the insulating primary elements 7 may be aligned with the grooves 12 of the insulating secondary elements 3 or not.

In figure 2 there are represented grooves 12 and 3 2 having an L-shaped section adapted to receive weld supports also having an L-shaped section. Alternatively, it is possible to use weld supports having a J-shaped section, which are compatible with thinner covers. In this variant, it is preferable for some internal partitions 25 of the box 2 0 to have a greater thickness, for example 24 mm.

The insulating primary element 7 described above has the advantage that it can be installed in one step thanks to the pre-assembly of the insulating slab 3 0 and the box 20. In a variant embodiment, the insulating slab 30 and the box 20 are supplied and installed separately. In this case, the insulating slab 30 is held in position in the tank wall by the clamping effect exerted by the primary retaining members 8 on the box 20 in the direction of the secondary membrane 5. The weld supports housed in the grooves 31 and the adjacent elements also contribute to immobilizing the insulating slab 30 laterally in this case.

Depending on the material of the insulating slab 30, a slippage layer that is not shown may be disposed between the slab and the secondary membrane 5 to limit abrasion.

The technique described above for producing a sealed and insulated tank wall may be used in different types of tank, for example to constitute an LNG tank in a terrestrial installation or in a floating structure such as a methane tanker ship, etc.

Referring to figure 3, a cutaway view of a methane tanker ship 7 0 shows a sealed and insulated tank 71 of prismatic general shape mounted in the double hull 72 of the ship. The wall of the tank 71 includes a sealed primary barrier intended to be in contact with the LNG contained in the tank, a sealed secondary barrier arranged between the sealed primary barrier and the double hull 72 of the ship, and two insulating barriers arranged between the sealed primary barrier and the sealed secondary barrier and between the sealed secondary barrier and the double hull 72, respectively.

In a manner known in itself, loading/offloading pipes 73 disposed on the top deck of the ship may be connected by means of appropriate couplings to a maritime or harbor terminal to transfer a cargo of LNG from or to the tank 71.

Figure 3 represents an example of a maritime terminal including a loading and offloading station 75, an underwater pipe 76 and a land installation 77. The loading and offloading station 75 is a fixed offshore installation including a mobile arm 74 and a tower 78 that supports the mobile arm 74. The mobile arm 74 carries a bundle of flexible insulated tubes 79 that can be connected to the loading/offloading pipes 73. The orientable mobile arm 74 adapts to all methane tanker ship loading gauges. A connecting pipe that is not represented extends inside the tower 78. The loading and offloading station 75 enables loading and offloading of the methane tanker ship 70 from or to the land installation 77. The latter includes liquefied gas storage tanks 80 and connecting pipes 81 connected by the underwater pipe 76 to the loading or offloading station 75. The underwater pipe 76 enables transfer of the liquefied gas between the loading or offloading station 75 and the land installation 77 over a great distance, for example 5 km, which enables the methane tanker ship 70 to remain far from the shore during loading and offloading operations.

Pumps on board the ship 7 0 and/or pumps equipping the land installation 77 and/or pumps equipping the loading and offloading station 75 are used to generate the pressure necessary to transfer the liquefied gas.

Although the invention has been described in connection with one particular embodiment, it is clear that it is no way limited thereto and that it encompasses all technical equivalents of the means described and combinations thereof if they fall within the scope of the invention.

The use of the verb "include" or "comprise" and its conjugate forms does not exclude the presence of elements or steps other than those stated in a claim. The use of the indefinite article "a" or "an" for an element or a step does not exclude the presence of a plurality of such elements or steps unless otherwise stated.

In the claims, any reference sign between parentheses should not be interpreted as a limitation of the claim.

Claims

1. An insulating block (7) for the fabrication of a sealed and insulating tank wall, the insulating block being intended to be disposed in accordance with a repeated pattern on a sealed secondary membrane (5) of the tank wall to form an insulating primary barrier (6) of the tank wall, the insulating block including a self-supporting box (20) filled with a thermally insulative packing, the self-supporting box including a cover panel (22) adapted to form a support surface for a sealed primary membrane (9) of the tank wall, a bottom wall (21) arranged opposite the cover panel, and lateral walls (23) extending between the bottom panel and the cover panel to define an interior space (26) of the box filled with the thermally insulative packing, characterized in that the bottom panel (21) of the self-supporting box extends continuously over all the surface of the box facing away from the cover panel, and the insulating block includes a layer (30) of insulating material fixed to the exterior surface of the bottom panel of the self-supporting box, the thickness of the layer of insulating material being greater than the height of the lateral raised edges (13) and the weld supports (11) of the sealed secondary membrane, parallel grooves (31) being formed in the layer (30) of insulating material to receive lateral raised edges (13) and weld supports (11) of the sealed secondary membrane .

2. An insulating block (7) as claimed in claim 1, having the overall shape of a rectangular parallelepiped.

3. The insulating block as claimed in claim 1 or 2, wherein the self-supporting box (20) includes parallel spacers (25) arranged in the interior space of the box to compartmentalize the interior space (26) of the box, the longitudinal ends of the spacers being fixed to the lateral walls (23).

4,. The insulating block as claimed in claim 3, wherein the parallel spacers (25) have a constant thickness . S, The insulating block as claimed in claim 4, wherein the thickness of the parallel spacers (25) is less than or equal to 15 mm. β. The insulating block as claimed in any one of claims 1 to 5, wherein the layer (30) of insulating material includes a polyurethane foam. ?, The insulating block as claimed in any one of claims 1 to 6, wherein the layer (30) of insulating material has a thickness greater than or equal to 35 mm.

1, The insulating block as claimed in any one of claim 1 to 7, having an overall thickness between 20 and 30 cm.

9, A sealed and insulating tank including a tank wall secured to a supporting structure, the tank wall including, in the direction of the thickness from the exterior toward the interior of the tank, an insulating secondary barrier secured to the supporting structure, a sealed secondary membrane secured to the insulating secondary barrier, an insulating primary barrier secured to the sealed secondary membrane, and a sealed primary membrane secured to the insulating primary barrier, each of the sealed membranes including a continuous layer of strips made of steel having a low coefficient of expansion that are welded in sealed manner by their lateral raised edges to parallel weld supports, characterized in that the insulating primary barrier is essentially constituted of a plurality of insulating elements juxtaposed in accordance with a repeated pattern, an insulating element including each time: a self-supporting box (20) filled with a thermally insulative packing, the self-supporting box including a cover panel (22) adapted to form a support surface for the sealed primary membrane (9) of the tank wall, a bottom panel (21) arranged opposite the cover panel, and lateral walls (23) extending between the bottom panel and the cover panel to define an interior space (26) of the box filled with the thermally insulative packing, the bottom panel (21) of the self-supporting box extending continuously over all the surface of the box facing away from the cover panel, and a layer (30) of insulating material arranged between the exterior surface of the bottom panel of the self-supporting box and the sealed secondary membrane (5) of the tank wall, the thickness of the layer of insulating material being greater than the height of the lateral raised edges (13) and the weld supports (11) of the sealed secondary membrane, parallel grooves (31) being formed in the layer (30) of insulating material to receive lateral raised edges (13) and weld supports (11) of the sealed secondary membrane .

10. The tank as claimed in claim 9, wherein the layer (30) of insulating material is retained by clamping it between the bottom panel of the selfsupporting box and the sealed secondary membrane (5) of the tank wall.

11. The tank as claimed in claim 9, wherein the layer (30) of insulating material is fixed to the bottom panel of the self-supporting box.

12. The tank as claimed in any one of claims 9 to 11, wherein a slippage layer is arranged between the layer (30) of insulating material and the sealed secondary membrane (5).

13. A ship (70) for transporting a cold liquid product, the ship including a double hull (72) and a tank (71) as claimed in any one of claims 9 to 12 disposed in the double hull.

14. A method of loading or offloading a ship (70) as claimed in claim 13, wherein a cold liquid product is fed through insulated pipes (73, 79, 76, 81) from or to a floating or terrestrial storage installation (77) to or from the tank (71) of the ship.

15. A transfer system for a cold liquid product, the system including a ship (70) as claimed in claim 13, insulated pipes (73, 79, 76, 81) arranged so as to connect the tank (71) installed in the hull of the ship to a floating or terrestrial storage installation (77) and a pump for driving a flow of cold liquid product through the insulated pipes from or to the floating or terrestrial storage installation to or from the tank of the ship.