EP4425038A1 - Storage facility for liquefied gas - Google Patents

Abstract

The invention relates to a storage facility (1) for liquefied gas comprising a supporting structure (2) and a sealed and thermally insulating tank comprising at least one bottom wall (4), in which the bottom wall (4) comprises a sump structure (9) comprising a container (11) comprising a side wall (15), the container (11) being arranged through the thickness of the bottom wall (4) and being located at least partially in a well (8) formed in the supporting structure (2), and the sump structure (9) comprising a metal support ring (18) fixed all around the side wall (15), in which the storage facility (1) comprises at least one support beam (19) fixed to the supporting structure (2) and arranged around the well (8), the support beam (19) comprising at least one layer of mastic (20).

Description

Technical field

The invention relates to the field of sealed and thermally insulating membrane tanks. In particular, the invention relates to the field of sealed and thermally insulating tanks for storing and/or transporting liquefied gas at low temperature, such as tanks for transporting Liquefied Petroleum Gas (also called LPG) having for example a temperature between -50°C and 0°C, or for transporting Liquefied Natural Gas (LNG) at approximately -162°C at atmospheric pressure. These tanks can be installed on land or on a floating structure. In the case of a floating structure, the tank can be intended for transporting liquefied gas or for receiving liquefied gas used as fuel for the propulsion of the floating structure.

Technological background

Storage facilities for liquefied gas are known for example in the document WO2020016509 . Such a storage facility comprises a supporting structure and a sealed and thermally insulating tank located inside the supporting structure and fixed thereto. The sealed and thermally insulating tank comprises a multilayer structure comprising in a thickness direction a sealing membrane and a thermally insulating barrier arranged between the sealing membrane and the supporting structure.

Such a storage facility comprises a sump structure on the bottom wall of the tank locally interrupting the sealing membrane, the sump structure comprising a container extending through the bottom wall of the tank. The sump structure is arranged in a well made in the supporting structure so that the liquid in the container is at the lowest level of the tank. Thus, by placing a pump inside such a container, it is possible to optimize the useful volume of cargo that can be loaded into the tank and unloaded from the tank.

When loading the tank with liquefied gas such as LNG, the elements of the tank directly in contact with the fluid such as the sump structure are subjected to a strong variation in temperature which results in them contracting thermally. This is why, in WO2020016509 , it is intended to fix the sump structure to the supporting structure using a fixing device which allows contraction and expansion of the sump structure container in order to limit the stresses in the fixing device.

Although such a system is satisfactory for limiting the mechanical constraints linked to the thermal contraction of the sump structure, it has the disadvantage of being complex and requiring a lot of assembly time when fixing the sump structure to the supporting structure.

In fact, during assembly, it is necessary to check the inclination and centering of the sump structure while ensuring that the support all around the structure is sufficient. In addition, flatness defects in the supporting structure must be taken into account for these checks.

Summary of the invention

One idea behind the invention is to simplify the mounting of the sump structure in a storage facility while allowing for thermal contraction/expansion of the sump structure.

According to one embodiment, the invention provides a storage facility for liquefied gas comprising a supporting structure and a sealed and thermally insulating tank, the tank comprising at least one bottom wall fixed to the supporting structure, in which the bottom wall comprises a multilayer structure in a thickness direction including at least one sealed membrane and at least one thermally insulating barrier arranged between the sealed membrane and the supporting structure, in which the bottom wall comprises a sump structure locally interrupting the sealed membrane of the bottom wall, the sump structure comprising a container comprising a side wall, the container being arranged through the thickness of the bottom wall and being located at least partially in a well provided in the supporting structure, the well extending towards the outside of the tank along a well axis, and the sump structure comprising a metal support ring fixed all around the side wall so as to project from the container in a radial direction towards the outside of the container,
wherein the storage facility comprises at least one support beam fixed to the supporting structure and arranged around the well, the support beam comprising at least one layer of mastic extending parallel to the supporting structure, the metal support ring of the sump structure being configured to rest on the support beam.

Thanks to these characteristics, the support beam makes it possible to simplify the assembly of the sump structure. In fact, the mastic layer of the support beam makes it possible, during the assembly of the sump structure, to more easily adapt the inclination of the sump structure, the mastic layer being able to crush more or less depending on the areas to compensate in particular for defects in the supporting structure.

Preferably, the support beam is an elongated building element. The support beam may have various shapes. In the preferred embodiment of the invention, the support beam has a curved shape.

According to embodiments, such an installation may comprise one or more of the following features.

According to one embodiment, the support beam comprises, in the direction parallel to the well axis, the mastic layer, a plywood layer and a metal layer, the metal support ring of the sump structure being configured to rest on the metal layer of the support beam.

Thus, the metal layer of the support beam, in cooperation with the metal support ring, ensures a certain sliding between the sump structure and the supporting structure with metal/metal contact. Finally, the plywood layer limits heat transfer between the sump structure and the supporting structure.

The plywood layer could also be replaced by any element with insulating properties and thus be made, for example, of solid wood or composite.

According to one embodiment, the waterproof membrane is sealed to the container all around the container.

According to one embodiment, the supporting structure comprises fixing studs arranged all around the well and extending parallel to the well axis, the support beam being fixed to the supporting structure using said fixing studs.

According to one embodiment, the supporting structure comprises a flat supporting wall pierced with an opening forming an entrance to the well, the at least one support beam being fixed to the flat supporting wall around the opening.

According to one embodiment, the container and the well are cylindrical in shape with a circular section.

According to one embodiment, the storage facility comprises at least two support beams, each beam having an annular sector shape.

According to one embodiment, the at least two support beams are dimensioned such that the sum of the annular sectors of the support beams forms an annular sector of at least 180°.

According to one embodiment, the storage facility comprises a single annular-shaped support beam located all around the well.

According to one embodiment, the storage facility comprises at least one stop fixed to the supporting structure and located between two support beams in a circumferential direction around the well, the metal support ring comprising a notch in which the stop is housed, the notch having a shape configured to limit, in cooperation with the stop, the movement of the sump structure in the circumferential direction and limit the movement of the sump structure in the radial direction.

Thus, the stop makes it possible to limit the movements of the sump structure while retaining the degree of freedom useful for thermal contraction/expansion.

According to one embodiment, the storage facility comprises at least one radially offset stop so as to be arranged beyond the annular sector shape of the support beam, the metal support ring comprising a notch in which the stop is housed, the notch having a shape configured to limit, in cooperation with the stop, the movement of the sump structure in the circumferential direction and to limit the movement of the sump structure in the radial direction. In such a configuration, a portion of the support beam may be interposed between the stop and the sump structure.

According to one embodiment, the stop has a cylindrical shape with a circular section while the notch has an oblong shape.

According to one embodiment, the metal support ring comprises an annular main body and at least one offset portion, the offset portion being offset from the annular main body in a direction parallel to the well axis and towards the supporting structure, the notch being made in the offset portion.

Thus, the cooperation between the stop and the notch is achieved as close as possible to the supporting structure.

According to one embodiment, the storage facility comprises four support beams distributed regularly around the well and four stops distributed regularly around the well, the waterproof membrane comprising a first series of parallel corrugations extending in a first direction and a second series of parallel corrugations extending in a second direction, two of the four stops being aligned with the center of the container in the first direction and two other of the four stops being aligned with the center of the container in the second direction.

Thus, a greater number of support beams makes it easier to assemble the sump structure by making it easier to obtain plane/plane contact between the support beams and the metal support ring. In addition, the choice of the number four makes it possible to position stops along the main axes of the tank.

According to one embodiment, the storage facility comprises a film disposed between the mastic layer and the supporting structure in a direction parallel to the well axis, the film being configured to prevent adhesion of the mastic layer to the supporting structure.

The film thus limits the stresses experienced by the mastic layer during deformation of the supporting structure.

According to one embodiment, the film is made using a sheet of paper, for example kraft paper, or even a polyethylene film.

In one embodiment, the putty layer comprises a plurality of putty sections spaced apart from each other, with foam blocks disposed between the putty sections.

In this way, the foam blocks prevent the mastic layer from flowing too quickly during the assembly stage of the sump structure and before polymerization of the mastic layer.

According to one embodiment, the storage facility comprises at least one anti-lift plate fixed to the support beam, the metal support ring being interposed between the support beam and the at least one anti-lift plate.

Thus, the anti-lift plate makes it possible to limit any possible lifting of the sump structure in a direction parallel to the well axis, particularly in the event of pressure differences between the interior of the tank and the thermally insulating barrier.

According to one embodiment, the metal support ring and the metal layer of the support beam are made of stainless steel.

According to one embodiment, an upper surface of the metal layer and a lower surface of the metal support ring have an arithmetic mean roughness (R _a ) of between 0.2 and 3.2 µm, preferably between 0.2 and 1.6 µm.

According to one embodiment, the metal layer of the support beam has a coating made of a material whose coefficient of friction is less than 0.2, preferably between 0.05 and 0.2. In order to facilitate sliding, it is possible to add a coating of polytetrafluoroethylene (PTFE) or high-density polyethylene (HDPE) type to the metal layer, or to lubricate the metal layer.

According to one embodiment, the well axis is a well axis of revolution and the sump structure has a sump structure axis of revolution, the well axis of revolution and the sump structure axis of revolution being parallel and spaced apart from each other by a distance of between 0 and 30 mm.

Such a facility may be a land-based storage facility, for example for storing LNG, or a floating, coastal or deep-water storage facility, such as for an LNG carrier, a floating storage and regasification unit (FSRU), a floating production and remote storage unit (FPSO) and others. Such a facility may also serve as a fuel tank in any type of vessel.

• fournir la structure porteuse comportant un puits, le puits s'étendant vers l'extérieur de la cuve selon un axe de puits,
• fournir une structure de puisard comprenant un récipient comportant une paroi latérale, et la structure de puisard comprenant un anneau de support métallique fixé tout autour de la paroi latérale de sorte à faire saillie du récipient dans une direction radiale vers l'extérieur du récipient,
• fixer des pieds de supportage et au moins une poutre de support à la structure porteuse de sorte que les pieds de supportage et la poutre de support soient disposées autour du puits, la poutre de support comportant au moins une couche de mastic s'étendant parallèlement à la structure porteuse,
• descendre la structure de puisard de sorte à déposer l'anneau de support métallique sur l'au moins une poutre de support et de sorte à situer au moins partiellement le récipient dans le puits,
• régler le centrage et l'inclinaison de la structure de puisard à l'aide des pieds de supportage,
• attendre la polymérisation de la couche de mastic,
• retirer les pieds de supportage.

According to one embodiment, the invention also provides a method of mounting a sump structure of a storage facility for liquefied gas, the storage facility comprising a supporting structure and a sealed and thermally insulating tank supported by the supporting structure, in which the method comprises the following steps:

• provide the supporting structure comprising a well, the well extending outwards from the tank along a well axis,
• providing a sump structure comprising a container having a side wall, and the sump structure comprising a metal support ring secured around the side wall so as to project from the container in a radial direction outwardly of the container,
• fixing support legs and at least one support beam to the supporting structure such that the support legs and the support beam are arranged around the well, the support beam having at least one layer of mastic extending parallel to the supporting structure,
• lowering the sump structure so as to place the metal support ring on the at least one support beam and so as to at least partially locate the container in the well,
• adjust the centering and inclination of the sump structure using the support feet,
• wait for the putty layer to polymerize,
• remove the support feet.

• fournir la structure porteuse comportant un puits, le puits s'étendant vers l'extérieur de la cuve selon un axe de puits
• fournir une structure de puisard comprenant un récipient comportant une paroi latérale, et la structure de puisard comprenant un anneau de support métallique fixé tout autour de la paroi latérale de sorte à faire saillie du récipient dans une direction radiale vers l'extérieur du récipient,
• préassembler une portion d'au moins une poutre de support à l'anneau de support métallique,
• fixer des pieds de supportage à la structure porteuse de sorte que les pieds de supportage soient disposées autour du puits,
• disposer une couche de mastic appartenant à l'au moins une poutre de support autour du puits,
• descendre la structure de puisard de sorte à déposer la portion de l'au moins une poutre de support sur la couche de mastic et de sorte à situer au moins partiellement le récipient dans le puits,
• régler le centrage et l'inclinaison de la structure de puisard à l'aide des pieds de supportage,
• attendre la polymérisation de la couche de mastic,
• retirer les pieds de supportage.

According to one embodiment, the invention also provides a method for mounting a sump structure of a storage facility for liquefied gas, the storage facility comprising a supporting structure and a sealed and thermally insulating tank supported by the supporting structure, in which the method comprises the following steps:

• provide the supporting structure comprising a well, the well extending outwards from the tank along a well axis
• providing a sump structure comprising a container having a side wall, and the sump structure comprising a metal support ring secured around the side wall so as to project from the container in a radial direction outwardly of the container,
• pre-assemble a portion of at least one support beam to the metal support ring,
• attach support legs to the supporting structure so that the support legs are arranged around the well,
• place a layer of putty belonging to at least one support beam around the well,
• lower the sump structure so as to deposit the portion of the at least one support beam on the putty layer and so as to at least partially locate the container in the well,
• adjust the centering and inclination of the sump structure using the support feet,
• wait for the putty layer to polymerize,
• remove the support feet.

According to one embodiment, the portion of the at least one support beam comprises a layer of plywood and a metal layer.

According to one embodiment, the support legs comprise a first adjustment device and a second adjustment device, the first adjustment device making it possible to adjust the centering of the sump structure, and the second adjustment device making it possible to adjust the inclination of the sump structure.

According to one embodiment, the first adjustment device comprises an adjustment screw extending in the radial direction relative to the sump structure.

According to one embodiment, the second adjustment device comprises an adjustment screw extending in a direction parallel to the well axis.

According to one embodiment, the invention also relates to a ship for transporting a cold liquid product, the ship comprising a double hull and an aforementioned storage facility arranged in the double hull.

According to one embodiment, the invention also provides a transfer system for a cold liquid product, the system comprising the aforementioned vessel, insulated pipes arranged so as to connect the tank installed in the hull of the vessel to a floating or land-based storage facility and a pump for driving a flow of cold liquid product through the insulated pipes from or to the floating or land-based storage facility to or from the tank of the vessel.

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

Brief description of the figures

• La figure 1 représente en perspective une structure porteuse au niveau d'un puits réalisé dans la structure porteuse, après la pose d'une couche de mastic selon une première variante de montage.
• La figure 2 représente une vue en perspective partielle d'une structure de puisard et notamment de son anneau de support métallique monté sur une portion de poutre de support préassemblée dans la première variante de montage.
• La figure 3 représente en perspective des poutres de support fixées à la structure porteuse autour du puits selon une deuxième variante de montage.
• La figure 4 représente en perspective une structure de puisard disposée dans le puits de la structure porteuse selon un mode de réalisation, après la pose de la structure de puisard.
• La figure 5 représente une vue en perspective partielle de la structure de puisard au niveau de la liaison entre une butée de la structure porteuse et une encoche de l'anneau de support métallique selon un mode de réalisation.
• La figure 6 représente une vue en perspective partielle de la structure de puisard au niveau de la liaison entre l'anneau de support métallique et la poutre de support selon un mode de réalisation.
• La figure 7 représente une vue en coupe de la structure de puisard disposée dans le puits de la structure porteuse selon un mode de réalisation.
• La figure 8 est une représentation schématique écorchée d'un navire méthanier comportant une installation de stockage et d'un terminal de chargement/déchargement de cette installation de stockage.

The invention will be better understood, and other objects, details, features and advantages thereof will become more clearly apparent, from the following description. of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings.

• There figure 1 shows in perspective a supporting structure at the level of a well made in the supporting structure, after the installation of a layer of mastic according to a first assembly variant.
• There figure 2 represents a partial perspective view of a sump structure and in particular of its metal support ring mounted on a portion of pre-assembled support beam in the first assembly variant.
• There figure 3 shows in perspective support beams fixed to the load-bearing structure around the well according to a second assembly variant.
• There figure 4 represents in perspective a sump structure arranged in the well of the supporting structure according to one embodiment, after the installation of the sump structure.
• There figure 5 represents a partial perspective view of the sump structure at the connection between a stop of the supporting structure and a notch of the metal support ring according to one embodiment.
• There figure 6 represents a partial perspective view of the sump structure at the connection between the metal support ring and the support beam according to one embodiment.
• There figure 7 represents a sectional view of the sump structure arranged in the well of the supporting structure according to one embodiment.
• There figure 8 is a cutaway schematic representation of a LNG carrier vessel comprising a storage facility and a loading/unloading terminal for this storage facility.

Description of the embodiments

In the description below, a storage facility 1 for storing and/or transporting liquefied gas will be described, comprising a supporting structure 2 and a sealed and thermally insulating tank 71. The sealed and thermally insulating tank comprises in particular a bottom wall 3, preferably generally flat, 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. The geometries Polyhedral are the most common. Cylindrical geometry is also possible.

The bottom wall 3 is mounted on a supporting structure 2, made for example of thick steel sheet such as the internal hull of a double-hulled ship 70. The bottom wall 3 has a multilayer structure successively including a secondary thermally insulating barrier 4 fixed on the supporting structure 2, a secondary waterproof membrane 5 supported by the secondary thermally insulating barrier 4, a primary thermally insulating barrier 6 arranged on the secondary waterproof membrane 5 and a primary waterproof membrane 7 supported by the primary thermally insulating barrier 6 and intended to be in contact with the liquefied gas contained in the tank 71. The multilayer structure is in particular represented schematically in figure 7 . The primary sealed membrane 7 defines an internal space intended to receive the liquefied gas. As an example, such membrane tanks are notably described in the patent applications WO2019239048 , WO14057221 , FR2691520 And FR2877638 .

The liquefied gas intended to be stored in the tank 71 may in particular be a liquefied natural gas (LNG), i.e. a gas mixture comprising mainly methane and one or more other hydrocarbons. The liquefied gas may also be ethane or a liquefied petroleum gas (LPG), i.e. a mixture of hydrocarbons resulting from the refining of petroleum comprising mainly propane and butane.

There figure 1 represents a substantially flat load-bearing wall of the load-bearing structure 2 on which the bottom wall 3 of the tank 71 will be fixed. The load-bearing wall is pierced with an opening forming an entrance to a well 8. The well 8 extends towards the outside of the tank 71 along a well axis 39,

Well 8 is intended to receive a sump structure 9 which will be described later.

As visible in figure 7 , the sump structure 9 comprises a first container 10 in communication with the interior of the tank, and a second container 11 surrounding the lower part of the first container 10. The first container 10 is connected in a continuous and sealed manner to the primary waterproof membrane 7. Likewise, the second container 11 is connected in a continuous and sealed manner to the secondary waterproof membrane 5, which it thus completes in a sealed manner.

More specifically, the first container 10 comprises a cylindrical side wall 12 whose axis is perpendicular to the supporting wall and which has a first fixing collar 13 located on an upper part of the cylindrical side wall 12 and essentially aligned with the primary waterproof membrane 7. A lower part of the cylindrical side wall 12 is engaged in the well 8 of the supporting structure 2. A lower wall 14 parallel to the supporting structure 2 closes the cylindrical side wall 12 at its lower part. The first fixing collar 13 is fixed at the edge of the upper part of the cylindrical side wall 12 and projects radially outside the latter all around the first container 10. Thus, the fluid contained in the first container 10 is located at the lowest level of the tank 71.

Similarly, the second container 11 comprises a cylindrical side wall 15 whose axis is perpendicular to the load-bearing wall and which has a second fixing collar 16 essentially aligned with the secondary waterproof membrane 5 and a lower part engaged in the well 8 below the lower wall 14 of the first container 10. A lower wall 17 parallel to the load-bearing wall closes the cylindrical side wall 15 of the second container 11 at its lower part. The cylindrical side wall 15 of the second container 11 surrounds the cylindrical side wall 12 of the first container 10 at a distance therefrom. The second fixing collar 16 is fixed at the edge of the upper part of the cylindrical side wall 15 and projects radially outside thereof all around the second container 11.

Insulating elements 37, visible in figure 7 are arranged all around the first container 10 and the second container 11.

In service, due to its position below the primary waterproof membrane 7, the first container 10 receives by gravity any liquid residue in the tank, in the manner of a sump. The first container 10 offers sufficient capacity to keep the suction head of a pump submerged in the liquid and thus maximizes the operating efficiency of the tank.

To have good structural stability, the first container 10 and the second container 11 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.

As represented in particular in figures 2 And 7 , the sump structure 9 comprises a metal support ring 18 welded all around the cylindrical side wall 15 of the second container 11. The metal support ring 18 allows the sump structure 9 to rest on the supporting structure 2.

In the embodiment described, the sump structure 9 comprises two containers 10, 11 located one inside the other since in the example, the tank 71 is a double membrane tank. However, the invention is also applicable to single membrane tanks. In such a case, the cylindrical side wall of the single container comprises a metal support ring which allows the sump structure to rest on the supporting structure.

Other embodiments of a sump structure 9 are for example described in the document WO2016/001142 .

The storage facility further comprises a plurality of support beams 19, four in number in the example shown in figure 4 , regularly distributed around the edge of the well 8 and which are fixed to the supporting structure 2. In other embodiments not shown, the number of support beams 19 could be different, for example a single support beam 19 or even two support beams 19.

Each support beam comprises in a direction parallel to the shaft axis 39 a layer of putty 20, a layer of plywood 21 on the layer of putty 20 and a metal layer 22 fixed on the layer of plywood 21 for example by screwing or riveting. The support beams 19 have, as visible in figure 3 , a ring sector shape.

The metal support ring 18 of the sump structure 9 thus comes to rest on the metal layer 22 of the support beams 19 all around the well 8.

The sump structure 9 and its support on the supporting structure 2 will be described in more detail using the Figures 1 to 7 which illustrate the invention at different stages of assembly of the sump structure 9.

There figure 1 represents a first step of assembly of the sump structure 9 to the supporting structure 2 according to a first assembly variant.

First of all, the location of the various constituent elements of the tank 71, and in particular the insulating panels, is marked on the load-bearing wall of the load-bearing structure 2. secondary of the secondary thermally insulating barrier 4 and of the sump structure 9. Following this tracing, fixing studs 23 are welded to the supporting structure 2 at the desired fixing locations of the various elements.

All around the well 8, films 24, for example kraft paper, are arranged on the future locations of the support beams 19 in order to prevent the layer of mastic 20 of the support beams 19 from adhering to the supporting structure 2.

Support legs 25 are also attached to the supporting structure 2 around the well 8 in order to facilitate the precise positioning of the sump structure 9.

In this first variant, the mastic layer 20 is directly applied to the kraft paper 24 in the form of a plurality of mastic sections 26 spaced apart from each other. Advantageously, foam blocks (not shown) are interposed between the different mastic sections in order to prevent the mastic layer 20 from creeping too quickly.

Regarding the plywood layer 21 and the metal layer 22 of the support beams 19, these are preassembled with each other; then the portion of the support beam 19 formed by the plywood layer 21 and the metal layer 22 is temporarily fixed, for example by means of wood screws 27, to the metal support ring 18 of the sump structure 9, as visible in figure 2 . Only by positioning the sump structure 9 in the well 8 are the mastic layer 20 and the portion of the support beam fixed to the metal support ring assembled to form the support beam 19. After positioning the sump structure 9, the support beams 19 are fixed to the supporting structure 2 using the fixing studs 23, such that portions of the fixing studs 23 protrude from the support beams 19.

There figure 3 represents a first step of mounting the sump structure 9 to the supporting structure 2 in a second mounting variant.

In this variant, each support beam 19 is pre-assembled before being placed on the supporting structure 2. Thus, the metal layer 22 is screwed or riveted onto the plywood layer 21 and the mastic layer 20 is directly arranged under the plywood layer 21 in different mastic sections spaced apart from each other and advantageously separated by foam blocks (not shown).

Then after pre-assembly, each support beam 19 is fixed to the supporting structure using the fixing studs 23 located all around the well 8 so that the layer of mastic 20 rests on a sheet of kraft paper 24 placed on the supporting structure 2. Portions of the fixing studs 23 thus protrude from the support beams 19.

• dans la première variante de montage, la couche de bois contreplaqué 21 fixée temporairement à l'anneau de support métallique 18 vienne se coller à la couche de mastic 20 de sorte à former les poutres de support 19,
• dans la deuxième variante de montage, l'anneau de support métallique 18 vienne être placé au contact de la couche métallique 22 des poutres de support 19.

There figure 4 represents a second step of mounting the sump structure 9 to the supporting structure 2. In this step, the sump structure 9 is lifted and placed vertically above the well 8, for example using a winch. Then it is lowered into the well so that:

• in the first assembly variant, the layer of plywood 21 temporarily fixed to the metal support ring 18 comes to stick to the layer of mastic 20 so as to form the support beams 19,
• in the second assembly variant, the metal support ring 18 is placed in contact with the metal layer 22 of the support beams 19.

Furthermore, after being lowered, the second fixing collar 16 of the sump structure 9 is brought into contact with one end of the support feet 25. In the example shown, the support feet 25 comprise at said end a height adjustment screw 28 extending in a direction parallel to the well axis 39 and a centering screw 29 extending radially relative to the sump structure 9.

By actuating the height adjustment screws 28 of the various support feet 25 arranged all around the well 8, it is possible to adjust the inclination of the sump structure 9. Similarly, by actuating the centering screws 29 of the various support feet 25 arranged all around the well 8, it is possible to adjust the centering of the sump structure 9 relative to the well 8.

When installing the sump structure 9 and then adjusting the inclination and centering, the layer of mastic 20 of the support beams 19 is more or less crushed depending on the areas by the dead weight of the sump structure 9 in order to compensate for the flatness defects of the supporting structure 2.

When centering the sump structure 9, it is possible to center the sump structure 9 with the tracings made on the supporting structure 2 and representing the future locations of the insulating panels and/or the corrugations of the corrugated waterproof membranes. This centering with the tracings can lead to an offset 38 between the axis of revolution 39 of the well 8 and the axis of revolution 40 of the sump structure 9, as visible in figure 7 . Nevertheless, despite a possible misalignment, the support of the sump structure 9 on the supporting structure 2 is still ensured by the support beams 19.

The assembly method then provides a waiting step in which the sump structure 9 is held in position until the mastic layer has polymerized, for example for a period of 24 hours. In another embodiment not shown, for the second assembly variant, the step of crushing the mastic layer 20 could be carried out prior to the arrangement of the sump structure 9 in the well 8, for example using a lighter structure having dimensions adapted to crush all of the support beams 19 simultaneously.

Once the layer of mastic 20 has polymerized, the support feet 25 are disassembled from the supporting structure 2.

There figure 5 represents a third step of assembly of the sump structure 9 to the supporting structure 2.

As can be seen in this figure, the metal support ring 18 comprises an annular main body 30 and a plurality of offset portions 31 regularly distributed around the sump structure 9. Each offset portion 31 is offset from the annular main body 30 in the direction parallel to the well axis 39 and towards the supporting structure 2. Each offset portion 31 projects from the annular main body 31 in a radial direction of the container 11 and towards the outside of the container 11. Each offset portion 31 has a notch 32 of oblong shape.

In this step, stops 33 of cylindrical shape with circular section are arranged in each of the notches 32 of the metal support ring 18 and are welded to the supporting structure 2. The stops 33, by cooperating with the notches 32, make it possible to limit the movement of the sump structure 9 in the circumferential direction and also to limit the movement of the sump structure 9 in the radial direction in order to avoid any damage to the primary 7 or secondary 5 waterproof membranes and also any damage to the primary 6 or secondary 4 thermally insulating barriers.

By welding the stops 33 to the supporting structure 2 after positioning the sump structure 9, it is thus possible to overcome manufacturing and assembly tolerances and therefore to facilitate the assembly of the sump structure.

It may be advantageous after partial welding of the stops 33 to the supporting structure 2, to temporarily lift the sump structure 9 in order to complete the welds of the stops 33 in order to facilitate the welding operation. In this case, for the first assembly variant and before lifting the sump structure 9, the wood screws 27 are removed.

In the case of a primary waterproof membrane 7 or a corrugated secondary waterproof membrane 5 which comprises a first series of parallel corrugations extending in a first direction and a second series of parallel corrugations extending in a second direction, the installation may advantageously comprise four stops 33, two of the four stops 33 being located on either side of the sump structure and aligned with the center of the second container 11 in the first direction and two others of the four stops 33 being located on either side of the sump structure 9 and aligned with the center of the second container 11 in the second direction. In the embodiment shown, the stops 33 are arranged between two support beams 19 adjacent in the circumferential direction of the well 8. In another embodiment not shown, the stops 33 are radially offset so as to be arranged beyond the annular sector shape of the support beams 19.

Furthermore, in the case of a storage facility 1 installed on a ship 70, the first direction may advantageously be the longitudinal direction of the ship 70 while the second direction may be the transverse direction of the ship 70.

As also visible on the figure 5 , the metal support ring 18 also has cutouts 34 directly above the portions of fixing studs 23 projecting from the support beams 19. These cutouts 34 allow the metal support ring 18 to be located at a distance from the fixing studs 23 and thus to allow deformation by thermal contraction/expansion of the sump structure 9. These cutouts 34 are made at the free end of the annular main body 30.

In the case of the first assembly variant, the wood screws 27 temporarily fixing the plywood layer 21 to the metal support ring 18 are removed, for example, at the end of this assembly step.

There figure 6 represents a fourth step of assembly of the sump structure 9 to the supporting structure 2.

In this step, anti-lift plates 35 are fixed to the fixing studs 23 projecting from the support beams 19 so that the metal support ring 18 is gripped between the anti-lift plates 35 and the support beams 19. Thus, the translation in the direction parallel to the well axis 39 of the sump structure 9 is limited. The anti-lift plates 35 are not tightened on the metal support ring 18 or with relatively little tightening, so as not to prevent the sump structure 9 from thermally contracting/expanding.

The fixing of these anti-lift plates 35 can be carried out using a washer/nut assembly 36 as shown in figure 6 . The anti-lift plates 35 have, for example, the shape of a disc with a diameter greater than the diameter of the cutouts 34.

Following this step, insulating elements are arranged all around the sump structure 9 and then the secondary thermally insulating barrier 4 is assembled around the sump structure 9. The secondary waterproof membrane 5, the primary thermally insulating barrier 6 and the primary waterproof membrane 7 are then successively assembled.

In reference to the figure 8 , a cutaway view of a LNG carrier 70 shows a sealed and thermally insulating tank 71 of generally prismatic shape mounted in the double hull 72 of the ship 70. The wall of the tank 71 comprises the primary sealed membrane 7 intended to be in contact with the LNG contained in the tank, the secondary sealed membrane 5 arranged between the primary sealed membrane 7 and the double hull 72 of the ship 70, and the two thermally insulating barriers arranged respectively between the primary sealed membrane 7 and the secondary sealed membrane 5 and between the secondary sealed membrane 5 and the double hull 72.

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

There figure 8 represents an example of a marine terminal comprising a loading and unloading station 75, a subsea pipeline 76 and a land installation 77. The loading and unloading station 75 is a fixed offshore installation comprising a mobile arm 74 and a tower 78 which supports the mobile arm 74. The mobile arm 74 carries a bundle of insulated flexible pipes 79 which can be connected to the loading/unloading pipelines 73. The orientable mobile arm 74 adapts to all sizes of LNG carriers. A connecting 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. The latter 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 onshore 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 transferring the liquefied gas, pumps on board the ship 70 and/or pumps equipping the onshore installation 77 and/or pumps equipping the loading and unloading station 75 are used.

Although the invention has been described in connection with several particular embodiments, it is quite 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 invention.

The use of the verb “to comprise”, “to understand” or “to include” and its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim.

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

Claims (15)

Storage installation (1) for liquefied gas comprising a supporting structure (2) and a sealed and thermally insulating tank, the tank comprising at least one bottom wall (4) fixed to the supporting structure (2), in which the bottom wall (4) comprises a multilayer structure in a thickness direction including at least one sealed membrane (5, 7) and at least one thermally insulating barrier (4, 6) arranged between the sealed membrane (5, 7) and the supporting structure (2), wherein the bottom wall (4) comprises a sump structure (9) locally interrupting the waterproof membrane (5, 7) of the bottom wall (4), the sump structure (9) comprising a container (11) comprising a side wall (15), the container (11) being arranged through the thickness of the bottom wall (4) and being located at least partially in a well (8) formed in the supporting structure (2), the well (8) extending towards the outside of the tank (71) along a well axis (39), and the sump structure (9) comprising a metal support ring (18) fixed all around the side wall (15) so as to project from the container (11) in a radial direction towards the outside of the container (11), wherein the storage facility (1) comprises at least one support beam (19) fixed to the supporting structure (2) and arranged around the well (8), the support beam (19) comprising at least one layer of mastic (20) extending parallel to the supporting structure (2), the metal support ring (18) of the sump structure (9) being configured to rest on the support beam (19). Storage facility (1) according to claim 1, wherein the support beam (19) comprises, in the direction parallel to the well axis (39), the putty layer (20), a plywood layer (21) and a metal layer (22), the metal support ring (18) of the sump structure (9) being configured to rest on the metal layer (22) of the support beam (19). Storage facility (1) according to claim 1 or claim 2, in which the supporting structure (2) comprises a flat supporting wall pierced with an opening forming an entrance to the well (8), the at least one support beam (19) being fixed to the flat supporting wall around the opening. Storage installation (1) according to one of claims 1 to 3, in which the container (11) and the well (8) are of cylindrical shape with a cross section circular, and the storage facility (1) comprises at least two support beams (19), each beam having the shape of an annular sector. Storage facility (1) according to claim 4, wherein the at least two support beams (19) are dimensioned such that the sum of the annular sectors of the support beams (19) forms an annular sector of at least 180°. A storage facility (1) according to claim 4 or claim 5, wherein the storage facility (1) comprises at least one stop (33) fixed to the supporting structure (2) and located between two support beams (19) in a circumferential direction around the well, the metal support ring (18) comprising a notch (32) in which the stop (33) is housed, the notch (32) having a shape configured to limit, in cooperation with the stop (33), the displacement of the sump structure (9) in the circumferential direction and to limit the displacement of the sump structure (9) in the radial direction. Storage facility (1) according to claim 6, wherein the storage facility (1) comprises four support beams (19) regularly distributed around the well (8) and four stops (33) regularly distributed around the well, the waterproof membrane (5, 7) comprising a first series of parallel corrugations extending in a first direction and a second series of parallel corrugations extending in a second direction, two of the four stops (33) being aligned with the center of the container (11) in the first direction and two others of the four stops (33) being aligned with the center of the container (11) in the second direction. Storage facility (1) according to one of claims 1 to 7, wherein the storage facility (1) comprises a film (24) arranged between the mastic layer (20) and the supporting structure (2) in a direction parallel to the well axis (39), the film (24) being configured to prevent adhesion of the mastic layer (20) to the supporting structure (2). Storage facility (1) according to one of claims 1 to 8, wherein the storage facility (1) comprises at least one anti-lift plate fixed to the support beam (19), the metal support ring (18) being interposed between the support beam (19) and the at least one anti-lift plate (35). Storage facility (1) according to one of claims 1 to 9, in which the well axis (39) is a well axis of revolution (39) and the structure sump structure has a sump structure revolution axis (40), the well revolution axis (39) and the sump structure revolution axis (40) being parallel and spaced apart from each other by a distance of between 0 and 30 mm. A vessel (70) for transporting a cold liquid product, the vessel comprising a double hull (72) and a storage facility (1) according to one of claims 1 to 10 arranged in the double hull. A transfer system for a cold liquid product, the system comprising a vessel (70) according to claim 11, insulated pipes (73, 79, 76, 81) arranged to connect the tank (71) installed in the hull of the vessel to a floating or land-based storage facility (1) (77) and a pump for driving a flow of cold liquid product through the insulated pipes from or to the floating or land-based storage facility (1) to or from the vessel tank. Method for assembling a sump structure (9) of a storage installation (1) for liquefied gas, the storage installation comprising a supporting structure (2) and a sealed and thermally insulating tank (71), in which the method comprises the following steps: - providing the supporting structure (2) comprising a well (8), the well (8) extending towards the outside of the tank along a well axis (39), - providing a sump structure (9) comprising a container (11) having a side wall (15), and the sump structure (9) comprising a metal support ring (18) secured all around the side wall (15) so as to project from the container (11) in a radial direction towards the outside of the container (11), - fixing support legs (25) and at least one support beam (19) to the supporting structure (2) such that the support legs (25) and the support beam (19) are arranged around the well (8), the support beam (19) comprising at least one layer of mastic (20) extending parallel to the supporting structure (2), - lowering the sump structure (9) so as to place the metal support ring (18) on the at least one support beam (19) and so as to at least partially locate the container (11) in the well (8), - adjust the centering and inclination of the sump structure (9) using the support feet (25), - wait for the putty layer to polymerize (20), - remove the support feet (25). Method for assembling a sump structure (9) of a storage installation (1) for liquefied gas, the storage installation comprising a supporting structure (2) and a sealed and thermally insulating tank (71), in which the method comprises the following steps: - providing the supporting structure (2) comprising a well (8), the well (8) extending towards the outside of the tank along a well axis (39), - providing a sump structure (9) comprising a container (11) having a side wall (15), and the sump structure (9) comprising a metal support ring (18) secured all around the side wall (15) so as to project from the container (11) in a radial direction towards the outside of the container (11), - pre-assembling a portion of at least one support beam (19) to the metal support ring (18), - fixing support feet (25) to the supporting structure (2) so that the support feet (25) are arranged around the well (8), - placing a layer of mastic (20) belonging to the at least one support beam (19) around the well, - lowering the sump structure (9) so as to deposit the portion of the at least one support beam (19) on the layer of mastic (20) and so as to at least partially locate the container (11) in the well (8), - adjust the centering and inclination of the sump structure (9) using the support feet (25), - wait for the putty layer to polymerize (20), - remove the support feet (25). A method of loading or unloading a ship (70), in which a cold liquid product is conveyed through insulated pipes (73, 79, 76, 81) from or to a floating or land-based (77) storage facility (1) to or from the tank (71) of the ship (70) according to claim 11.

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