EP3164636B1 - Sealed and insulating tank disposed in a floating double hull - Google Patents

Description

Technical area

The invention relates to the field of watertight and insulating membrane tanks arranged in floating structures, in particular for the storage and / or transport of a cold product, in particular a liquefied gas, for example liquefied natural gas (LNG) which contains a high content of methane and which has a liquid state at around -162 ° C at atmospheric pressure.

Technological background

In the membrane tank technique, the internal surfaces of a load-bearing structure such as the internal hull of a double-hull ship are upholstered with a multilayer structure comprising two thin waterproofing membranes alternated with two layers of thermal insulation which serve both to limit the flow of heat through the vessel wall and to structurally support the waterproof membranes.

In order to maximize the operating efficiency of such a tank, it is desirable to optimize the useful volume of cargo that it is possible to load into the tank and unload from the tank. However, the use of an unloading pump sucking the liquid towards the top of the tank means that a certain height of liquid has to be kept at the bottom of the tank, failing which the suction member of the pump enters into communication with the gas phase, which deactivates and / or degrades the pump. Given the swelling of the cargo by the swell, the height of liquid required can hardly be minimized.

The publication FR-A-2832783 envisages the creation of a sump in the cryogenic insulation of the tank as an expensive and ineffective solution.

The publication KR-10-2010-0092748 discloses a sump obtained by making a concave stepped portion in the bottom wall of a membrane tank. This stepped portion, however, presents difficulties in implementation given the need to deflect the entire multilayer structure of the tank wall in the concave stepped portion.

FR1318891 describes a self-supporting metal tank for liquefied gas arranged in a ship with the interposition of a thick layer of thermal insulation between the self-supporting metal tank and the interior hull of the ship. In one embodiment, a side wall of the metal tank is pierced with an exhaust orifice opening into a pipe connecting the metal tank to a pump sump by means of a collecting pipe and of valves or control taps . In another embodiment, a bottom wall of the metal tank is pierced with an orifice opening into a pipe connecting the metal tank to a pump sump via a manifold pipe and control valves or taps. A centrifugal pump placed in the pump sump makes it possible to move the liquid by passing it through a riser intended to be connected to an onshore installation. The pump sump, the centrifugal pump and the riser are arranged outside the metal tank, in particular between two walls of a transverse partition of the ship where they are easily accessible.

summary

One idea underlying the invention is to provide a reliable sump structure which is relatively simple to manufacture in the bottom wall of a membrane tank.

According to one embodiment, the invention provides a sealed and insulating tank arranged in a double floating shell, the tank comprising tank walls fixed to internal walls of the double floating shell, in which a tank wall has a structure with multiple layers superimposed in a thickness direction including a primary waterproof membrane intended to be in contact with a product contained in the tank, a secondary waterproof membrane disposed between the primary waterproof membrane and the internal wall of the double shell, a barrier of secondary thermal insulation disposed between the secondary waterproof membrane and the internal wall of the double shell and supporting the secondary waterproof membrane, and a primary thermal insulation barrier disposed between the primary waterproof membrane and the secondary waterproof membrane and supporting the primary waterproof membrane,
wherein an inner bottom wall of the double shell carries a bottom wall of the tank and a sump structure locally interrupting the primary waterproof membrane of the bottom wall of the tank, the sump structure comprising a rigid container arranged through the thickness of the bottom wall of the tank and intended to receive a suction member of a pump,
wherein the rigid container has a bottom wall located at a level more external than the secondary waterproof membrane of the bottom wall of the tank in the thickness direction of the bottom wall of the tank and a peripheral side wall linked by sealingly at the bottom wall of the container and extending towards the inside of the tank from the bottom wall of the container at least to the primary waterproof membrane of the bottom wall of the tank, the peripheral side wall having an opening situated opposite the bottom wall of the container and opening into the interior of the tank,
wherein the sump structure comprises a primary connection plate surrounding the container, the primary connection plate having a connection surface extending parallel to the primary waterproof membrane of the bottom wall of the tank, the primary waterproof membrane of the bottom wall of the tank being tightly attached to the connection surface all around the sump structure.

Thanks to these characteristics, it is possible to locally interrupt the primary membrane by the sump structure and connect the primary waterproof membrane flat on the primary connection plate. In addition, a relatively large container can be obtained thanks to the position of its bottom wall.

According to embodiments, such a tank may include one or more of the following characteristics.

According to one embodiment, the sump structure further comprises a support foot for supporting equipment in the sealed tank, the support foot comprising a hollow envelope having a longitudinal axis substantially perpendicular to the inner bottom wall of the double shell , a first longitudinal end of the hollow casing bearing against the internal bottom wall of the double shell and a second longitudinal end of the hollow casing projecting into the tank to support the equipment at a distance from the primary waterproof membrane,
the container of the sump structure being fixed inside the hollow envelope, the primary connection plate being disposed between the first longitudinal end and the second longitudinal end of the hollow envelope and having an edge internal tightly bonded to the hollow casing all around the hollow casing.

The side wall of the container can be produced in different ways, for example partially or entirely distinct from the hollow envelope and / or partially or entirely merged with the hollow envelope.

According to corresponding embodiments, the peripheral lateral wall of the container is housed in the hollow envelope on at least one lower part of the container and / or the peripheral lateral wall of the container is formed by the hollow envelope on at least one upper part of the container.

According to one embodiment, the sump structure further comprises a secondary connection plate disposed between the primary connection plate and the first longitudinal end of the hollow envelope and having an internal edge tightly connected to the hollow envelope while around the hollow casing, the secondary connection plate having a connection surface extending parallel to the secondary waterproof membrane of the bottom wall of the tank, the secondary waterproof membrane of the bottom wall of the tank being attached tightly on the bonding surface all around the sump structure.

Thanks to these characteristics, it is possible to locally interrupt the secondary waterproof membrane by the sump structure and connect the secondary waterproof membrane flat on the secondary connection plate.

According to one embodiment, the sump structure further comprises a secondary sealed wall fixed inside the hollow envelope outside the container and delimiting a primary space inside the hollow envelope between the container and the secondary sealing wall, and a porous insulating lining arranged in the primary space inside the hollow envelope.

According to one embodiment, the secondary sealed wall forms a second container having an interior space in which is disposed a lower portion of the first container of the sump structure.

According to one embodiment, the primary connection plate has an internal edge tightly connected to the peripheral side wall of the container all around the container.

According to one embodiment, the sump structure further comprises a secondary connection plate disposed between the primary connection plate and the bottom wall of the container and having an internal edge tightly connected to the peripheral lateral wall of the container all around of the container, the secondary connection plate having a connection surface extending parallel to the secondary waterproof membrane of the bottom wall of the tank, the secondary waterproof membrane of the bottom wall of the tank being tightly attached to the bonding surface all around the sump structure.

According to one embodiment, the sump structure further comprises a second container having an interior space in which is disposed a lower portion of the container of the sump structure, the second container having a bottom wall disposed at the same level as the wall bottom of the first container in the thickness direction of the bottom wall of the tank or at a level more external than the bottom wall of the first container, the second container having a peripheral lateral wall tightly connected to the wall of bottom of the second container and extending towards the inside of the tank from the bottom wall of the second container at least to the secondary waterproof membrane of the bottom wall of the tank,
and in which the sump structure further comprises a secondary connection plate disposed between the primary connection plate and the bottom wall of the second container and having an internal edge tightly connected to the peripheral lateral wall of the second container all around the second container, the secondary connection plate having a connection surface extending parallel to the secondary waterproof membrane of the bottom wall of the tank, the secondary waterproof membrane of the bottom wall of the tank being tightly attached to the bonding surface all around the sump structure.

According to one embodiment, the bottom wall of the first container and the bottom wall of the second container are formed by a single sealed plate to which the peripheral side wall of the first container and the peripheral side wall of the second container surrounding the wall are linked. peripheral side of the first container.

According to another embodiment, the bottom wall of the second container is spaced from the bottom wall of the first container in the thickness direction of the bottom wall of the tank.

Preferably in this case, a support element can be arranged between the bottom walls of the two containers to increase the support of the first container. According to a corresponding embodiment, the lateral peripheral wall of the first container extends beyond the bottom wall of the first container in the thickness direction of the bottom wall of the tank and is supported on the bottom wall of the second container.

According to one embodiment, a porous insulating lining is disposed in a primary space delimited between the first container and the second container, in particular between their peripheral side walls.

According to one embodiment, a block of insulating material is disposed on the inner bottom wall of the double shell, the block of insulating material having an upper surface opposite to the inner bottom wall of the double shell, the bottom wall d 'at least one of the first and second containers being supported on the upper surface of the block of insulating material.

According to one embodiment, the sump structure further comprises a hollow extension structure fixed projecting on an external surface of the inner bottom wall of the double shell,
the inner bottom wall of the double shell further comprising an opening opening into an internal space of the hollow extension structure, said opening being traversed by the container of the sump structure, so that the bottom wall of the container is located in the internal space of the extension structure at a level more external than the internal bottom wall of the double shell in the thickness direction of the bottom wall of the tank.

Preferably, thermally insulating materials are housed in the internal space of the hollow extension structure around the first and, if necessary, the second container. Several possibilities exist for this.

According to one embodiment, a block of insulating material is disposed on a bottom wall of the extension structure, the block of insulating material having an upper surface opposite to the bottom wall of the extension structure, the wall of bottom of at least one of the first and second containers being in abutment on the upper surface of the block of insulating material.

According to one embodiment, support legs extend the lateral peripheral wall of the second container beyond the bottom wall of the second container in the thickness direction of the bottom wall of the tank and rest on a bottom wall of the extension structure.

According to one embodiment, a porous insulating lining is disposed in a secondary space delimited between the peripheral side wall of the second container and a peripheral side wall of the extension structure.

According to one embodiment, the peripheral side wall of the container of the sump structure has an upper flared portion projecting above the primary waterproof membrane of the bottom wall of the tank.

According to one embodiment, the upper flared portion is provided with a through orifice and a non-return valve associated with the orifice and having a direction of opening oriented towards the interior of the container.

The containers and the extension structure can be produced in different forms, depending in particular on the desired capacity and the available space or on space constraints. According to one embodiment, at least one or each of the bottom wall of the first container, the bottom wall of the second container and the bottom wall of the extension structure is parallel to the internal bottom wall of the double hull.

The capacity of the sump container can be selected according to various criteria, in particular the flow rate of the pump and the specifics of the application concerned, in particular the presence or not of swell, whether or not to empty the tank completely in order to be able to load cargo having a different chemical composition (for abuse of language we speak of multi-gas or mono-gas application when the chemical compounds are transported in the liquid state at their liquefaction temperatures). By way of example, a typical swell period is of the order of 15 s, so that a sizing criterion applicable to the sump applicable in this case is to contain a sufficient volume of liquid to support the flow rate of the pump. during this period, at least 62.5 liters for a flow rate of around 15 m3 / hour, as well as a liquid heel in the sump to guarantee the proper functioning of the pump. This value varies depending on the application case and the specifics of the pump.

Many possibilities exist for producing the multilayer structure of the vessel wall.

According to one embodiment, the primary thermal insulation barrier and the secondary thermal insulation barrier essentially consist of parallelepipedal blocks of polyurethane foam, the secondary waterproof membrane is produced by waterproof composite sheets assembled by bonding and the waterproof membrane primary is carried out by embossed sheet metal plates assembled by welding. Other details on the realization of such a multilayer structure can be found for example in the publication FR-A-2781557 .

According to one embodiment, the primary thermal insulation barrier and the secondary thermal insulation barrier essentially consist of parallelepipedal blocks of polyurethane foam, the secondary waterproof membrane is produced by embossed sheet metal plates assembled by welding and the membrane primary waterproofing is carried out by embossed sheet metal plates assembled by welding. Other details on the realization of such a multilayer structure can be found for example in the publication FR-A-2996520 .

According to one embodiment, the primary thermal insulation barrier and the secondary thermal insulation barrier essentially consist of wooden parallelepiped boxes filled with an insulating lining, and the primary and secondary waterproof membranes are made by alloy strakes with low expansion coefficient assembled by welding parallel to each other at raised edges forming expansion bellows. Other details on the realization of such a multilayer structure can be found for example in the publication FR-A-2798902 .

Such a tank can be installed in a floating structure, coastal or in deep water, in particular an LNG tanker, a floating storage and regasification unit (FSRU), a floating production and remote storage unit (FPSO) and others.

According to one embodiment, a vessel for transporting a cold liquid product comprises a double hull and aforementioned tank arranged in the double hull.

According to one embodiment, the invention also provides a method of loading or unloading such a ship, in which a product is conveyed cold liquid through insulated pipes from or to a floating or land-based storage facility to or from the vessel's tank.

According to one embodiment, the invention also provides a transfer system for a cold liquid product, the system comprising the aforementioned ship, isolated pipes arranged so as to connect the tank installed in the hull of the ship to a floating storage installation. or terrestrial and a pump to drive a flow of cold liquid product through the isolated pipes from or to the floating or terrestrial storage facility to or from the vessel of the ship.

Brief description of the figures

• La figure 1 est une vue schématique plane en coupe d'une paroi de fond d'une cuve munie d'une structure de puisard selon un premier mode de réalisation.
• La figure 2 est une vue schématique en perspective et en coupe d'une paroi de fond d'une cuve munie d'une structure de puisard selon un deuxième mode de réalisation, dans laquelle une garniture isolante est omise pour laisser voir l'espace interne de la structure d'extension.
• La figure 3 est une vue schématique en perspective et en coupe d'une paroi de fond d'une cuve munie d'une structure de puisard selon un troisième mode de réalisation.
• La figure 4 est une vue schématique en perspective et en coupe d'une paroi de fond d'une cuve munie d'une structure de puisard selon un quatrième mode de réalisation.
• La figure 5 est une vue schématique en perspective et en coupe d'une paroi de fond d'une cuve munie d'une structure de puisard selon un cinquième mode de réalisation.
• La figure 6 est une vue schématique plane en coupe d'une structure de puisard selon un sixième mode de réalisation.
• La figure 7 est une vue analogue à la figure 6, dans laquelle la structure de puisard est montrée à l'état assemblé avec la paroi de fond de la cuve.
• La figure 8 est une vue schématique plane en coupe d'une paroi de fond d'une cuve munie d'une structure de puisard selon un septième mode de réalisation.
• La figure 9 est une vue schématique plane en coupe d'une paroi de fond d'une cuve munie d'une structure de puisard selon un huitième mode de réalisation.
• La figure 10 est une vue analogue à la figure 9, dans laquelle la structure de puisard est munie en outre d'une collerette évasée.
• La figure 11 est une vue schématique plane en coupe d'une zone de fond d'une cuve située à la base d'une tour de déchargement et dans laquelle des structures de puisard peuvent être employées.
• La figure 12 est une représentation schématique écorchée d'une cuve de navire méthanier et d'un terminal de chargement/déchargement de cette cuve.

The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely by way of illustration and without limitation. , with reference to the accompanying drawings.

• The figure 1 is a schematic plan view in section of a bottom wall of a tank provided with a sump structure according to a first embodiment.
• The figure 2 is a schematic perspective view in section of a bottom wall of a tank provided with a sump structure according to a second embodiment, in which an insulating lining is omitted to reveal the internal space of the structure extension.
• The figure 3 is a schematic perspective view in section of a bottom wall of a tank provided with a sump structure according to a third embodiment.
• The figure 4 is a schematic perspective view in section of a bottom wall of a tank provided with a sump structure according to a fourth embodiment.
• The figure 5 is a schematic perspective view in section of a bottom wall of a tank provided with a sump structure according to a fifth embodiment.
• The figure 6 is a schematic plan view in section of a sump structure according to a sixth embodiment.
• The figure 7 is a view analogous to the figure 6 , in which the sump structure is shown in the assembled state with the bottom wall of the tank.
• The figure 8 is a schematic plan view in section of a bottom wall of a tank provided with a sump structure according to a seventh embodiment.
• The figure 9 is a schematic plan view in section of a bottom wall of a tank provided with a sump structure according to an eighth embodiment.
• The figure 10 is a view analogous to the figure 9 , in which the sump structure is further provided with a flared collar.
• The figure 11 is a schematic plan view in section of a bottom zone of a tank located at the base of an unloading tower and in which sump structures can be used.
• The figure 12 is a cutaway schematic representation of an LNG tank and a loading / unloading terminal for this tank.

Detailed description of embodiments

In the description below, we will describe several sump structures that can be used in the bottom wall of an LNG storage and / or transport tank. The bottom wall designates a wall, preferably generally planar, located at the bottom of the tank relative to the earth's gravity field. The general geometry of the tank can also be of different types. Polyhedral geometries are the most common. Cylindrical, spherical or other geometry is also possible.

The walls of the tank are formed by a multilayer structure fixed on load-bearing walls and including two waterproof membranes alternating with two thermally insulating barriers. Since there are many known techniques for producing these multilayer structures, the description below will be limited to the sump structure and the wall area located in the immediate vicinity of the sump structure.

With reference to the figure 1 , a suction head of a pump shown schematically in figure 1 is received in a sump structure 10 arranged in a tank wall 2 located at the bottom of the tank.

The tank wall 2 is mounted on a flat load-bearing wall 3, made for example from thick sheet steel such as the inner hull of a double-hull ship. The tank wall 2 has a multilayer structure successively including a secondary insulating barrier 4 fixed on the supporting wall 3, for example by means of mastic beads 8, a secondary waterproof membrane 5 supported by the secondary insulating barrier 4, a primary insulating barrier 6 covering the secondary waterproof membrane 5 and a primary waterproof membrane 7 supported by the primary insulating barrier 6.

At the location of the sump structure 10, the support wall 3 has a circular opening 9 through which the sump structure 10 is engaged and which allows the sump structure 10 to protrude outside of the support wall 3 in the thickness direction of the tank wall 2.

A hollow cylindrical bowl 20 is fixed to the support wall 3 around the opening 9 and projects outwards from the support wall 3 to form an extension structure which provides additional space for housing the sump structure 10. More specifically, the hollow cylindrical bowl 20 has a cylindrical side wall 21, for example circular or other, an upper edge of which is welded to the carrier wall 3 all around the opening 9 and a flat bottom wall 22, for example circular or other, welded to a lower edge of the cylindrical side wall 21 and arranged parallel to the load-bearing wall 3. The hollow cylindrical cup 20 can be made of materials similar to the load-bearing wall 3.

To prevent the hollow cylindrical bowl 20 from tending to collect liquids accidentally present in the secondary insulating barrier 4, such as water of condensation or water from leaks at the ballast , there is preferably provided a rim 26 projecting towards the inside of the tank on the carrier wall 3 all around the opening 9.

The sump structure 10 includes a primary cylindrical bowl 11, which provides a first container in communication with the interior of the tank, and a secondary cylindrical bowl 16, which provides a second container surrounding the bottom of the first container. The primary cylindrical bowl 11 is connected continuously to the primary membrane 7, which it thus completes in a sealed manner. Likewise, the secondary cylindrical bowl 16 is connected continuously to the secondary membrane 5, which it thus completes in a sealed manner.

More specifically, the primary cylindrical bowl 11 has a cylindrical side wall 12 whose axis is perpendicular to the carrier wall 3 and which has an upper edge essentially aligned with the waterproof membrane 7 and a lower edge engaged in the hollow cylindrical bowl 20 in below the carrier wall 3. A bottom wall 13 parallel to the carrier wall 3 closes the cylindrical side wall 12 at its lower edge. A planar annular rim 14 is fixed at the level of the upper edge of the cylindrical side wall 12 and projects radially outside of the latter all around the primary cylindrical bowl 11.

The primary membrane 7 thus has an interruption in the form of a window, for example a circular or square window, the edge 15 of which surrounds the sump structure 10 and is sealingly connected to the upper surface of the flat edge 14, for example by welding or gluing.

Similarly, the secondary cylindrical bowl 16 has a cylindrical side wall 17 whose axis is perpendicular to the support wall 3 and which has an upper edge essentially aligned with the secondary waterproof membrane 5 and a lower edge engaged in the hollow cylindrical bowl 20 in below the bottom wall 13. A bottom wall 18 parallel to the carrier wall 3 closes the cylindrical side wall 17 at its lower edge. The cylindrical side wall 17 surrounds the cylindrical side wall 12 at a distance from the latter. A planar annular rim 19 is fixed at the level of the upper edge of the cylindrical lateral wall 17 and projects radially outside of the latter all around the secondary cylindrical bowl 16.

The secondary membrane 5 also has an interruption in the form of a window, for example a circular or square window, the edge 25 of which surrounds the sump structure 10 and is sealingly connected to the upper surface of the flat edge 19, for example by welding or gluing.

In the tank wall 2, the space between the carrier wall 3 and the secondary membrane 5 is a secondary space containing the secondary insulating barrier 4 and in which it is possible to circulate a flow of nitrogen as a safety measure. In the sump structure 10, the space between the secondary cylindrical bowl 16 and the hollow cylindrical bowl 20 is also a secondary space 27 which communicates with the secondary space of the tank wall 2 in order to be able to receive this nitrogen sweep.

The secondary insulating barrier 4 is for example formed of juxtaposed modular blocks for lining the load-bearing wall 3 relatively uniformly. These modular blocks stop at a certain distance from the sump structure 10, as indicated by the edge 28. Blocks insulators of suitable shape can be designed to approach relatively close to the sump structure 10 or fit into it and thus limit the gap remaining to be filled in the secondary insulation. Insulating materials are housed in the gap 29 between the edge 28 of the secondary insulating barrier 4 and the secondary cylindrical bowl 16, as well as in the secondary space 27 of the sump structure 10 to complete the thermal insulation around the secondary cylindrical bowl 16. In fact, the secondary membrane 5 and the secondary cylindrical bowl 16 are liable to be in contact with the LNG in the event of an accidental leak in the primary membrane 7.

Different insulating materials may be suitable to thus complete the secondary thermal insulation, for example glass or rock wool, polymer foams, in particular polyurethane or PVC, balsa, plywood, aerogels, and others.

Preferably, the insulating materials housed between the bottom wall 22 and the bottom wall 18 also have sufficient rigidity to structurally support the secondary cylindrical bowl 16 and the primary cylindrical bowl 11. For this, on the figure 1 , a relatively rigid insulating panel 30 is housed between the bottom wall 22 and the bottom wall 18, produced for example in the form of a block of polyurethane foam sandwiched between two plywood plates. The insulating panel 30 is fixed to the bottom wall 22, for example by fastening devices 31 comprising threaded studs projecting from the bottom wall 22 and engaged in holes made in a peripheral zone of the lower plywood plate. as well as nuts screwed onto the studs.

The bottom wall 18 is fixed on top of the insulating panel 30, for example by similar fixing devices cooperating with a peripheral rim 32 of the bottom wall 18 which protrudes radially from the side wall 17.

Similarly, in the tank wall 2, the space between the secondary membrane 5 and the primary membrane 7 is a primary space containing the primary insulating barrier 6 and in which it is possible to circulate a flow of nitrogen by measuring security. In the sump structure 10, the space between the primary cylindrical bowl 11 and the secondary cylindrical bowl 16 is also a primary space 33 which communicates with the primary space of the tank wall 2 to be able to receive this nitrogen sweep .

The primary insulating barrier 6 is for example formed of juxtaposed modular blocks for lining the load-bearing wall 3 relatively uniformly. These modular blocks stop at a certain distance from the sump structure 10, as indicated by the edge 34. Blocks insulators of suitable shape can be designed to approach relatively close to the sump structure 10 or fit into it and thus limit the gap remaining to be filled in the primary insulation. Insulating materials are housed in the gap 35 between the edge 34 of the primary insulating barrier 6 and the primary cylindrical bowl 11, as well as in the primary space 33 of the sump structure 10 to complete the thermal insulation around the primary cylindrical bowl 11. In fact, the primary membrane 7 and the primary cylindrical bowl 11 are in contact with the LNG during use.

Different insulating materials may be suitable to thus complete the primary thermal insulation, for example glass or rock wool, polymer foams, in particular polyurethane or PVC, balsa wood, plywood, aerogels, and others.

Preferably, the insulating materials housed between the bottom wall 18 and the bottom wall 13 also have sufficient rigidity to structurally support the primary cylindrical bowl 11. For this, on the figure 1 , a relatively rigid insulating panel 36 is housed between the bottom wall 18 and the bottom wall 13, produced for example in the form of a block of plywood. The insulating panel 36 is fixed to the bottom wall 18, for example by fastening devices 37 comprising threaded studs fixed projecting on the bottom wall 18 and engaged in holes made in a peripheral zone of the plywood block thus only nuts screwed onto the studs.

The bottom wall 13 is fixed on top of the insulating panel 36 by the fixing devices 37 cooperating with a peripheral rim 38 of the bottom wall 13 which protrudes radially from the side wall 12.

In service, because of its position below the primary membrane 7, the primary bowl 11 receives by gravity any liquid residue present in the tank, in the manner of a sump. The primary bowl 11 has sufficient capacity to keep the suction head of the pump 1 immersed in the liquid for a certain period, for example of the order of 15 s or more.

To have good structural stability, the primary bowl 11 and the secondary bowl 16 are made of a more rigid material than the waterproof membranes, for example with a metal sheet of the order of 6 to 20 mm thick.

With reference to figures 2 to 4 , other embodiments of the sump structure will now be described, which are more particularly suitable for a tank wall produced according to the technology described in the publications. FR-A-2781557 or FR-A-2961580 . Elements analogous or identical to those of the figure 1 have the same reference number and are only described to the extent that they differ from the figure 1 .

In this case, the primary insulation barrier 6 essentially consists of blocks of polyurethane foam covered with plywood plates 40 forming the support surface of the primary membrane. The primary membrane, which is omitted on the figures 2 to 4 , is made by means of thin plates of embossed sheet known elsewhere. To fix the embossed sheet plates on the plywood plates 40, these are provided with metal plates 41, 42 fixed in countersinks on the top of the plywood plates 40.

The structure of the primary membrane in the immediate vicinity of the sump structure can be produced in the same way as the connection between the primary membrane and the support leg as taught in the publication FR-A-2961580 .

More specifically, metal plates 42 fixed to the plywood plates 40 surround the planar annular rim 14 of the sump structure at a short distance from it, for example by forming a square contour by measuring simplicity. Closing plates (not shown) are arranged around the planar annular rim 14 and welded in a sealed manner to the latter over its entire periphery. For this, the closure plates are cut in a semicircle at their inner edge, while their outer edge delimits a square and is superimposed on the metal plates 42 all around the sump structure to be fixed by welding on the metal plates 42. The primary waterproof barrier in the sump area 10 is completed, on the one hand by welding the edges of watertight plates of embossed sheet on the closure plates, and on the other hand by sealing any ends of the undulations interrupted at this point.

The structure of the secondary membrane in the immediate vicinity of the sump structure can be carried out in the same way as the connection between the secondary membrane and the support leg as taught in the publication FR-A-2961580 by forming the rim 19 with a square outline. In particular, the secondary membrane consists of a waterproof composite sheet 5 bonded to the modular blocks of polyurethane foam constituting the secondary insulating barrier 4. To achieve the continuity of the secondary waterproof barrier around the sump structure, four strips 43 d a waterproof composite material made of aluminum foil and glass fiber are bonded to the flat edge 19 and to the waterproof composite sheet 5. A strip 43 is positioned each time so as to overlap one side of the edge 19 and the edge of the waterproof composite sheet 5.

Alternatively, the flat edge 19 can be formed with a circular outline. In this case, the structure of the secondary membrane in the immediate vicinity of the sump structure can be produced in an identical manner to the connection between the secondary membrane and the support leg as taught in the French application. FR3002515 filed February 22, 2013 under the deposit number 1351584 .

The embodiment of the figure 2 also shows special arrangements for supporting the primary bowl 11 and the secondary bowl 16. In particular, support legs 45 extend the side wall 17 of the secondary bowl 16, so as to come to bear on the bottom wall 22. As a result, the insulating materials housed in the secondary space 27, not shown on the figure 2 , do not need to offer a structural rigidity as high as the insulating panel 30 and can be made of flexible materials.

Similarly, a support wall 46 extends the side wall 12 of the primary bowl 11, so as to come to bear on the bottom wall 18. As a result, the insulating materials housed in the primary space 33, not shown on the figure 2 , do not need to offer a structural rigidity as high as the insulating panel 36 and can be made of flexible materials. Ports 47 in the support wall 46 allow the circulation of a gas phase in the primary space.

Furthermore, an annular rim 48 is positioned around the side wall 17 to provide an additional support surface in alignment with the load-bearing wall 3, in particular for supporting small insulating blocks 49 having a shape adapted to come tightly surround the wall lateral 17. The annular flange 48 can be fixed to the supporting wall 3 and / or to the lateral wall 17.

The embodiment of the figure 3 is similar to that of the figure 2 , but it includes the lower insulating block 30 in place of, or in combination with, the support feet 45.

In a variant not shown, for the sake of simplification, the same wall 18 can form the bottom of the primary bowl 11 and of the secondary bowl 16. For this, relative to the figure 3 , the wall 13 and the insulating panel 36 are eliminated and the orifices 47 are blocked. A secondary bowl is obtained which no longer passes below the primary bowl 11 but which only goes around it.

An additional degree of simplification is obtained in the embodiment of the figure 4 where the secondary bowl is completely removed. The flat edge 19 is fixed directly around the side wall 12 of the primary bowl 11, for example by welding.

The embodiment of the figure 5 differs from the figure 3 by two aspects.

On the one hand, the hollow cylindrical bowl 20 is shallower to limit the size of the sump structure outside the bearing wall 3. Thus, the bottom wall 18 of the secondary bowl 16 is here on the inside of the supporting wall 3.

On the other hand, the sump structure 10 is used here in combination with a tank wall produced according to the technology described in the publication FR-A-2798902 . Elements analogous or identical to those of the figure 1 have the same reference number and are only described to the extent that they differ from the figure 1 .

In this case, the primary insulation barrier 6 and the secondary insulation barrier 4 essentially consist of plywood boxes 50 filled with an insulating lining, for example made of perlite, glass wool or the like. The primary membrane 7 and the secondary membrane 5 are produced by means of parallel strakes with raised edges in steel with low coefficient of expansion known as invar® which are retained on the cover panels of the plywood boxes 50 by means of elongated welding support.

Around the primary bowl 11 the strakes of the primary membrane 7 are cut so as to form a square window 51. The continuity of the primary membrane 7 between the edge of the window 51 and the flat edge 14 can be achieved by means of plates closing as previously described.

The embodiments of figures 6 to 8 relate to a sump structure which jointly makes a support leg 110. Elements similar or identical to those of the figure 1 bear the same reference figure increased by 100 and are only described to the extent that they differ from the figure 1 .

For clarity, the tank wall is omitted on the figure 6 . The support foot 110 has a hollow shape of revolution with a frustoconical lower part 52 flaring downwards for stability measurement and bearing on the load-bearing wall 3, and a right upper part 53. The opening 9 is deleted in the embodiment of the figure 6 . The primary bowl 111 has a diameter similar to the upper right part 53 and is fixed in the extension of the latter inside the frustoconical lower part 52. More specifically, an upper edge of the side wall 112 is fixed so tight to the inner surface of the frustoconical lower part 52 all around the support leg 110. The secondary bowl 116 has a larger diameter and is fixed below the primary bowl 111 inside the frustoconical lower part 52. More specifically, an upper edge of the side wall 117 is tightly fixed on the inner surface of the frustoconical lower part 52 all around the support leg 110.

On its outer surface, the support foot 110 carries the planar rim 114 at about the same level as the upper edge of the primary bowl 111 and the planar rim 119 at about the same level as the upper edge of the secondary bowl 116 As before, the flat edges 114 and 119 serve to seal the primary and secondary waterproof membranes (not shown) around the support leg 110.

Inlet openings 54 are formed through the wall of the support leg 110 slightly above the rim 114, so as to be slightly above the primary waterproof membrane. They make it possible to collect the liquid in the primary bowl 111 by gravity even when the filling level of the tank is below the top 55 of the support leg 110.

Similarly, circulation orifices 56 and 57 are formed through the wall of the support leg 110 between the flanges 114 and 119 and under the flange 119, so as to allow the passage of the gas phase between the primary space of the wall of the tank and the primary space 133 of the support foot 110, and respectively between the secondary space of the tank wall and the secondary space 127 of the support foot 110.

The production of connections between a support leg and the primary membrane and the secondary membrane of a vessel wall have been described in the publication. FR-A-2961580 . These connections are applicable to the support base 110.

The figure 7 schematically illustrates another way of making these connections. In this embodiment, the vessel wall has a structure similar to the figure 2 . Elements analogous or identical to those of the figure 2 bear the same reference number increased by 100. In this case, the edges of the sheet metal plates forming the primary waterproof membrane 7 are welded directly to the flat edge 114 all around the support leg 110. Furthermore waterproof composite strips 143 are glued astride the flat rim 119 and the waterproof sheet 5 of the adjacent modular blocks all around the support leg 110.

In the figures 6 and 7 , between the upper edge of the side wall 112 and the inlet orifices 54, the wall of the support leg 110 thus extends the wall of the primary bowl 111 in a sealed manner. Primary bowl 111 and this portion of the wall of the support leg 110 thus jointly form a sealed container, the wall of the support leg 110 of which forms the upper part.

To increase the capacity of the primary bowl 111, it is possible to combine the support leg 110 with a hollow cylindrical bowl 120 extending outside the bearing wall 103. This combination is illustrated diagrammatically on the figure 8 . Thus, the bottom wall of the primary bowl 111 can be moved away from the outside of the carrier wall 103 to increase the capacity of the bowl.

Another way to adjust the capacity of the primary bowl 111 is to vary the diameter of the support leg 110. In preferred embodiments, this diameter is between 0.4 m and 1 m.

Furthermore, although the bowls 111 and 116 have been shown to be entirely separate from the support leg 110, it is clear that the side wall of the support leg 110 could alternately constitute the side wall of the bowl 111 or 116 on at least one part of its height. For this, it suffices to provide a bottom wall 113 or 118 closing off the section of the support leg 110 at the desired level.

The embodiments of Figures 9 and 10 relate to a sump structure which remains inside the carrying wall 203 to limit the size of the tank. Elements analogous or identical to those of the figure 1 bear the same reference figure increased by 200 and are only described to the extent that they differ from the figure 1 . The primary waterproof membrane is omitted.

In the embodiment of the figure 9 , the primary bowl 211 and the secondary bowl 216 are not fixed to each other. The flat edge 214 of the primary bowl 211 is supported in a counterbore on the top of the modular blocks 206 forming the primary insulating barrier where it is fixed. Likewise, the flat rim 219 of the secondary bowl 216 is supported in a counterbore on the top of the modular blocks 204 forming the secondary insulating barrier where it is fixed. Between the load-bearing wall 203 and the bottom 218 of the secondary bowl 216, the insulating block 230 of relatively small thickness is preferably made of material with very high insulation power, for example in aerogels or in insulating panel under vacuum. Optionally, a relatively rigid block, not shown, can be installed between the bottom 218 and the bottom 213 to improve the support of the primary bowl 211.

The secondary waterproof membrane 205 is tightly linked to the flat edge 219. Preferably, circulation grooves are formed in the bottom plate 59 of the modular blocks 206, so as to allow the passage of the gas phase between the primary space of the tank wall and the primary space 233 of the sump structure.

The embodiment of the figure 10 differs from the figure 9 only by the addition of a frustoconical upper end 58 above the primary cup 211. This end piece is provided at its base, just above the primary waterproof membrane not shown, with inlet holes 61 controlled by non-return valves not shown, which make it possible to capture, in the frusto-conical upper end 58, the residues of liquid present at the bottom of the tank.

The techniques described above for producing a sump structure can be used in different types of tanks, for example an LNG tank in a floating structure such as an LNG tanker or other.

The figure 11 schematically illustrates the installation of a sump structure, corresponding here to the sump structure 210 of the figure 9 , at the base of a loading / unloading tower 60 in an LNG tank, namely vertical to the liquid dome of the tank. The loading / unloading tower 60 is supported by a support leg 63 bearing on the load-bearing wall 3 which is the internal bottom wall of the double hull of the ship. The loading / unloading tower 60 comprises in particular a main pump 62 and an auxiliary pump 1 of smaller flow rate than the main pump 62. The sump structure 210 is arranged to receive the suction input of the auxiliary pump 1. By moreover, by virtue of the integration of the sump structure into the thickness of the tank wall, the tank walls 65 can be produced according to the usual planar multilayer structure, both at the bottom wall 3 and at the transverse cofferdam 64, and the connection to the sump structure 210 is obtained without significantly deviating the waterproof membranes from their usual plane geometry.

With reference to the figure 12 , a cutaway view of an LNG tanker 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 includes a primary waterproof barrier intended to be in contact with the LNG contained in the tank, a barrier secondary watertight arranged between the primary watertight barrier and the double hull 72 of the ship, and two insulating barriers arranged respectively between the primary watertight barrier and the secondary watertight barrier and between the secondary watertight barrier and the double hull 72.

In a manner known per se, loading / unloading lines 73 arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a maritime or port terminal for transferring a cargo of LNG from or to the tank 71.

The figure 12 represents an example of a maritime terminal comprising a loading and unloading station 75, an underwater pipe 76 and a shore installation 77. The loading and unloading station 75 is a fixed offshore installation comprising a movable arm 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 which can be connected to the loading / unloading pipes 73. The movable arm 74 can be adjusted to suit all sizes of LNG carriers. A connection pipe, not shown, extends inside the tower 78. The loading and unloading station 75 allows the loading and unloading of the LNG carrier 70 from or to the onshore installation 77. This comprises liquefied gas storage tanks 80 and connecting pipes 81 connected by the subsea pipe 76 to the loading or unloading station 75. The subsea pipe 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the shore installation 77 over a long distance, for example 5 km, which makes it possible to keep the LNG carrier 70 at a great distance from the coast during the loading and unloading operations.

To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps fitted to the shore installation 77 and / or pumps fitted to the loading and unloading station 75 are used. unloading the tank, one can use in particular the auxiliary pump 1 and / or the main pump 62 arranged in the tank.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the claims.

The use of the verb "to include", "to understand" or "to include" and of its conjugated forms does not exclude the presence of elements or other stages than those stated in a claim. The use of the indefinite article "a" or "an" for an element or a stage does not exclude, unless otherwise stated, the presence of a plurality of such elements or stages.

In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims (24)

1. A sealed and insulated tank equipped with an unloading pump and arranged in a floating double hull, the tank comprising tank walls which are fixed to internal walls of the floating double hull, in which a tank wall (2, 65) comprises a multilayer structure with multiple layers superposed in a thickness direction including a primary sealing membrane (7, 107) intended to be in contact with a product contained in the tank,
   in which an internal bottom wall (3, 103, 203) of the double hull bears a bottom wall of the tank and a sump structure (10, 110, 210) locally interrupting the primary sealing membrane of the bottom wall of the tank, the sump structure comprising a rigid container (11, 111,211) arranged through the thickness of the bottom wall of the tank,
   said rigid container comprising a peripheral lateral wall (12, 112, 212), the peripheral lateral wall extending toward the inside of the tank at least as far as the primary sealing membrane (7, 107) of the bottom wall of the tank, the peripheral lateral wall having an opening which opens to the inside of the tank,
   in which the sump structure comprises a primary connecting plate (14, 114, 214) surrounding the container and having an internal edge connected in a sealed manner, directly or indirectly, to the peripheral lateral wall (12, 112, 212) of the container all around the container, the primary connecting plate having a connecting surface extending parallel to the primary sealing membrane of the bottom wall of the tank, the primary sealing membrane of the bottom wall of the tank being attached in a sealed manner to the connecting surface all around the sump structure characterized in that the multilayer structure of the tank wall further comprises a secondary sealing membrane (5, 105) arranged between the primary sealing membrane and the internal wall of the double hull, a secondary thermal insulation barrier (4, 104, 204) arranged between the secondary sealing membrane and the internal wall of the double hull and supporting the secondary sealing membrane, and a primary thermal insulation barrier (6, 106, 206) arranged between the primary sealing membrane and the secondary sealing membrane and supporting the primary sealing membrane,
   the unloading pump being arranged in the tank so that it draws up the product contained in the tank toward the top of the tank, the unloading pump comprising a suction member (1, 101, 201) housed in said rigid container,
   in which the rigid container comprises a bottom wall (13, 113, 213) situated at a more exterior level than the secondary sealing membrane (5, 105, 205) of the bottom wall of the tank in the thickness direction of the bottom wall of the tank, the peripheral lateral wall (12, 112, 212) of the rigid container being connected in a sealed manner to the bottom wall of the container so as to be closed by the bottom wall (13, 113, 213) of the container, the peripheral lateral wall extending toward the inside of the tank from the bottom wall of the container, the opening of the peripheral lateral wall opening to the inside of the tank being situated opposite to the bottom wall of the container.
2. The tank as claimed in claim 1, in which the sump structure further comprises a support base to support equipment in the sealed tank, the support base comprising a hollow shell (110) having a longitudinal axis substantially perpendicular to the internal bottom wall (103) of the double hull, a first longitudinal end of the hollow shell bearing against the internal bottom wall of the double hull and a second longitudinal end of the hollow shell projecting into the tank to support the equipment some distance away from the primary sealing membrane,
   the container(111) of the sump structure being fixed inside the hollow shell (110), the primary connecting plate (114) being arranged between the first longitudinal end and the second longitudinal end of the hollow shell and having an internal edge connected in a sealed manner to the hollow shell all around the hollow shell.
3. The tank as claimed in claim 2, in which the peripheral lateral wall (112) of the container (111) is housed in the hollow shell (110) over at least a lower part of the container.
4. The tank as claimed in claim 2 or 3, in which the peripheral lateral wall of the container is made up of the hollow shell (110) over at least an upper part of the container.
5. The tank as claimed in claim 2, in which the sump structure further comprises a secondary connecting plate (119) arranged between the primary connecting plate and the first longitudinal end of the hollow shell (110) and having an internal edge connected in a sealed manner to the hollow shell all around the hollow shell, the secondary connecting plate having a connecting surface running parallel to the secondary sealing membrane of the bottom wall of the tank, the secondary sealing member (105) of the bottom wall of the tank being attached in a sealed manner to the connecting surface all around the sump structure.
6. The tank as claimed in claim 5, in which the sump structure additionally comprises a secondary sealing wall (116) fixed inside the hollow shell (110) on the outside of the container (111) and delimiting a primary space (133) inside the hollow shell between the container (111) and the secondary sealing wall (116), and a porous insulating packing arranged inside the primary space inside the hollow shell.
7. The tank as claimed in claim 6, in which the secondary sealing wall forms a second container (116) having an interior space in which a lower portion of the first container (111) of the sump structure is arranged.
8. The tank as claimed in claim 1, in which the sump structure further comprises a secondary connecting plate (19) arranged between the primary connecting plate (14) and the bottom wall (18) of the container and having an internal edge connected in a sealed manner to the peripheral lateral wall (12) of the container all around the container, the secondary connecting plate having a connecting surface running parallel to the secondary sealing membrane of the bottom wall of the tank, the secondary sealing membrane (5) of the bottom wall of the tank being attached in a sealed manner to the connecting surface all around the sump structure.
9. The tank as claimed in claim 1, in which the sump structure further comprises a second container (16, 216) having an interior space in which a lower portion of the container (11, 211) of the sump structure is arranged, the second container comprising a bottom wall (18, 218) arranged at the same level as the bottom wall (18) of the first container in the thickness direction of the bottom wall of the tank or at a level further toward the outside than the bottom wall (13, 213) of the first container, the second container comprising a peripheral lateral wall (17, 217) connected in a sealed manner to the bottom wall of the second container and extending toward the inside of the tank from the bottom wall of the second container at least as far as the secondary sealing membrane of the bottom wall of the tank, and in which the sump structure further comprises a secondary connecting plate (19, 219) arranged between the primary connecting plate and the bottom wall (18, 218) of the second container and having an internal edge connected in a sealed manner to the peripheral lateral wall of the second container all around the second container, the secondary connecting plate having a connecting surface extending parallel to the secondary sealing membrane (5, 205) of the bottom wall of the tank, the secondary sealing membrane of the bottom wall of the tank being attached in a sealed manner to the connecting surface all around the sump structure.
10. The tank as claimed in claim 9, in which the bottom wall of the first container and the bottom wall of the second container are formed by a single sealed plate (18) to which the peripheral lateral wall of the first container and the peripheral lateral wall of the second container surrounding the peripheral lateral wall of the first container are connected.
11. The tank as claimed in claim 9, in which the bottom wall (18, 218) of the second container is spaced away from the bottom wall (13, 213) of the first container in the thickness direction of the bottom wall of the tank.
12. The tank as claimed in claim 11, in which the lateral peripheral wall (46) of the first container is extended beyond the bottom wall of the first container in the thickness direction of the bottom wall of the tank and bears against the bottom wall (18) of the second container.
13. The tank as claimed in one of claims 9 to 12, further comprising a porous insulating packing arranged in a primary space delimited between the first container and the second container.
14. The tank as claimed in one of claims 8 to 13, further comprising a block of insulating material (230) arranged on the internal bottom wall of the double hull, the block of insulating material comprising an upper surface opposite to the internal bottom wall of the double hull, the bottom wall (213) of at least one of the first and second containers bearing against the upper surface of the block of insulating material.
15. The tank as claimed in one of claims 1 to 14, in which the sump structure further comprises a hollow extension structure (20, 120) fixed as a projection on an exterior surface of the internal bottom wall (3, 103) of the double hull, the internal bottom wall of the double hull further comprising an opening (9, 109) opening into an internal space of the hollow extension structure, said opening having the container (11, 111) of the sump structure passing through it such that the bottom wall of the container is situated in the internal space of the extension structure at a level that is further toward the outside than the internal bottom wall of the double hull in the thickness direction of the bottom wall of the tank.
16. The tank as claimed in claim 15, considered in combination with one of claims 8 to 14, further comprising a block of insulating material (30) arranged on a bottom wall (22, 122) of the extension structure, the block of insulating material comprising an upper surface opposite to the bottom wall of the extension structure, the bottom wall (18) of at least one of the first and second containers (11, 16) bearing against the upper surface of the block of insulating material.
17. The tank as claimed in claim 15 or 16 considered in combination with claim 11, further comprising support bases (45) extending the lateral peripheral wall (17) of the second container beyond the bottom wall of the second container in the thickness direction of the bottom wall of the tank and bearing against a bottom wall (22) of the extension structure.
18. The tank as claimed in one of claims 16 and 17, further comprising a porous insulating packing arranged in a secondary space (27, 127) delimited between the peripheral lateral wall of the second container and a peripheral lateral wall of the extension structure.
19. The tank as claimed in one of claims 15 to 18, in which the bottom wall of the extension structure is parallel to the internal bottom wall of the double hull.
20. The tank as claimed in one of claims 1 to 19, in which the peripheral lateral wall of the container of the sump structure comprises a flared upper portion (58) projecting above the primary sealing membrane of the bottom wall of the tank, the flared upper portion being equipped with a through-orifice (61) and with a nonreturn valve associated with the orifice and having a direction of opening oriented in the direction of the inside of the container.
21. The tank as claimed in one of claims 1 to 20, in which the bottom wall of the or each container is parallel to the internal bottom wall of the double hull.
22. A ship (70) for transporting a cold liquid product, the ship comprising a double hull (72) and a tank (71) as claimed in one of claims 1 to 21 arranged in the double hull.
23. A method for loading or unloading a ship (70) as claimed in claim 22, in which a cold liquid product is conveyed through insulated pipes (73, 79, 76, 81) from or to a floating or on-shore storage facility (77) to or from the tank of the ship (71).
24. A transfer system for transferring a cold liquid product, the system comprising a ship (70) as claimed in claim 22, insulated pipes (73, 79, 76, 81) arranged in such a way as to connect the tank (71) installed in the hull of the ship to a floating or on-shore storage facility (77), said unloading pump being able to drive a stream of cold liquid product through the insulated pipes toward the floating or on-shore storage facility from the tank of the ship.

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