WO2021228751A1

WO2021228751A1 - Liquid dome of a storage tank for liquefied gas comprising an opening provided with an additional hatch

Info

Publication number: WO2021228751A1
Application number: PCT/EP2021/062294
Authority: WO
Inventors: Julien COUTEAU; Edouard DUCLOY
Original assignee: Gaztransport Et Technigaz
Priority date: 2020-05-11
Filing date: 2021-05-10
Publication date: 2021-11-18
Also published as: FR3109978B1; CN115552166A; KR20230009428A; FR3109978A1

Abstract

The invention relates to a storage installation (1) for liquefied gas and to a sealed and thermally insulating tank (71) having a charging and discharging opening (10) comprising at least a first and a second through-access (20, 30) having an internal and external end, the external end being provided with an external removable wall, the installation (1) comprising at least a first sealed enclosure (41) enveloping the external end of the first access (20), the external removable wall of the first access (20) forming a wall of said first enclosure (41), and the first enclosure (41) being filled with a gas referred to as a neutral gas.

Description

Title of the invention: Liquid dome of a storage tank for liquefied gas comprising an opening with an additional hatch

The invention relates to the field of storage facilities for liquefied gas comprising a sealed and thermally insulating tank, with membranes. In particular, the invention relates to the field of sealed and thermally insulating tanks for the storage and / or transport of liquefied gas at low temperature, such as tanks for the transport of Liquefied Petroleum Gas (also called LPG) exhibiting by example a temperature between -50 ° C and 0 ° C, or for the transport of 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 may be intended for the transport of liquefied gas or to receive liquefied gas serving as fuel for the propulsion of the floating structure.

[0002] Document FR2991430 describes a storage installation for liquefied gas comprising a sealed and thermally insulating tank integrated into a supporting structure formed by the double hull of a ship. Each wall of the tank includes a secondary thermally insulating barrier, a secondary waterproofing membrane, a primary thermally insulating barrier and a primary waterproofing membrane.

In an area located at the top of the tank, the tank has a protruding portion in the form of a chimney called a liquid dome. In this zone, the supporting structure is locally interrupted so as to delimit a loading / unloading opening intended to be crossed by fluid loading / unloading pipes. This loading / unloading opening, known as the Liquid Dome, comprises an insulation or thermally insulating barrier as well as an element forming a primary waterproofing membrane.

[0004] However, there is no secondary sealing membrane at this loading / unloading opening, unlike the rest of the tank for which there is a primary insulation membrane and then a secondary thermal insulation barrier and finally the walls of the supporting structure. In fact, in this zone of the tank, it is considered that the outer wall of the liquid dome, the free outer face of which opens onto the upper deck or even the inner deck (also called “inner deck”), in itself forms the secondary waterproofing membrane.

[0005] After various experiments and tests, the Applicant has found that there are areas of weakness in the loading / unloading opening in terms of physical (risk of leakage) and thermal insulation of the contents of the tank. Such areas of weakness can lead to heat exchanges unfavorable to the function of the tank (the "Boil-off Rate" of the latter must be minimal) or even to leaks of the fluid contained in the tank.

[0006] The Applicant intends to remedy these observed deficiencies by proposing a solution that is at the same time simple, inexpensive and above all making it possible to ensure perfect sealing, both physical and thermal, of the extremely cold fluid contained in the tank.

[0007] Thus, the present invention relates to a storage installation for liquefied gas comprising a supporting structure and a sealed and thermally insulating tank arranged in the supporting structure, the sealed and thermally insulating tank comprising a main structure formed by a plurality of walls of tank connected to each other and fixed to the supporting structure, the main structure defining an internal storage space, the main structure comprising at least one waterproofing membrane and at least one thermally insulating barrier, the thermally insulating barrier being placed between the waterproofing membrane and the supporting structure, the supporting structure comprising a substantially planar upper supporting wall, the waterproofing membrane, the thermally insulating barrier of the main structure and the upper supporting wall being interrupted locally so as to delimit a loading opening / unloading comprising at least a first and a second removable through access having an inner and outer end, the outer end being provided with a removable outer wall.

The invention is characterized in that the installation comprises at least a first sealed enclosure enveloping the outer end of the first access, the external removable wall of the first access forming a wall of said first enclosure, and in that the first enclosure is filled with a so-called neutral gas.

[0009] Thus, the Applicant has observed after multiple tests and analyzes that the access (s) passing through the loading / unloading opening of the liquid dome presents (s) a weakness in the insulation of the tank or of the storage installation liquefied gas. These accesses are known to those skilled in the art as "man access", also referred to in English as "Man Hole", and "material access", also referred to in English as "Material Hole".

On the basis of these analyzes, the applicant proposes a simple, efficient and inexpensive system for completely securing and sealing these particular areas. The enclosure then forms a second sealing membrane, the primary membrane being provided by the side and outer walls of each of the two through accesses.

The expression “through access” is understood to mean the fact that the orifices, that is to say the human access and the material access, pass through the internal cover of the loading / unloading opening. and are formed by a barrel, conventionally metallic, of cylinder, rectangular or even square section.

[0012] By convention, the terms "external" and "internal" are used to define the relative position of an element with respect to another, by reference to the interior and exterior of the tank.

The expression "neutral gas" is understood to mean the fact that it is the non-flammable gas used in the thermal insulation space of the tank, namely conventionally molecular nitrogen N2 which is usually found in admixture with residual gases from polymer foams and glues used to form the thermal insulation barrier of the tank, the latter being present in small quantity compared to the quantity of dinitrogen. Of course, provision can be made to replace all or part of this molecular nitrogen N2 by another non-flammable gas, preferably exhibiting qualities of satisfactory thermal non-conductivity. Monitoring the quantity of this neutral gas in the thermal insulation space of the tank, and therefore in particular at the level of the liquid dome, makes it possible in particular to detect the appearance of a leak of liquefied or gaseous gas. Preferably, the two through access conventionally present at the level of the liquid dome are provided with such an insulation enclosure, filled with a neutral gas. Thus, preferably, the installation comprises a second sealed enclosure enveloping the outer end of the second access, the external removable wall of the second access forming a wall of said second enclosure, the second enclosure being filled with the so-called neutral gas.

[0015] Other advantageous features of the invention are presented succinctly below:

Advantageously, the first and / or the second enclosure is / are fixed (s) by sealed welding on the external surface of the storage installation.

According to one possibility offered by the invention, the first and second enclosures are isolated by thermal insulation means such as for example glass wool, polyurethane foam or other material suitable for being housed in said enclosures and exhibiting a very low coefficient of thermal conduction.

According to a preferred embodiment, the first and the second enclosures respectively comprise a first and second removable enclosure walls having dimensions substantially greater than those respectively of the aforesaid first and of the aforesaid second external removable walls of the first and from the second crossing access.

According to a preferred embodiment, the external removable walls of the first and second through access, preferably as well as the first and second removable enclosure walls, are fixed in a sealed manner by mechanical means, for example screws or bolts. Of course, in order to ensure a perfect seal, at least one seal is added to this mechanical means.

[0020] Furthermore, according to a possible variant, the fixing of the external removable walls of the first and of the second through access, possibly as well as the first and the second removable enclosure walls, is carried out by welding, even if this solution can be less convenient for disassembling these fixed elements. Thus, the external removable walls of the enclosures are fixed respectively to the two respective outer ends of the barrel constituting the through access while the removable enclosure walls are fixed to the fixed casing of each enclosure, respectively.

Preferably, the inner and outer walls of the first and second access are fixed to the end periphery of said first or second access respectively by mechanical means, for example screws or bolts, and by welding. Thus, the removable outer wall of the first and second access are sealed by mechanical means, possibly supplemented for example by a seal while the inner wall of the first and second access are sealed by welding.

According to a preferred embodiment, the loading / unloading opening comprises a cover forming a primary sealing membrane, the first and second access passing through said cover of the loading / unloading opening and being fixed in a sealed manner, preferably by welding, to said cover.

Advantageously, the first and / or the second enclosure has at least one passage for communication with the thermally insulating barrier of the main structure. Thus, the neutral gas in one of the enclosures is in direct communication with the neutral gas, preferably identical, located in the insulation space of the tank so as to form a single insulation space. Preferably, each enclosure has a plurality of passages for communication with the thermally insulating barrier of the main structure.

Advantageously, the first and / or the second aforesaid enclosure is / are made of steel. This steel is preferably a stainless steel or Invar ^®.

Advantageously, the so-called neutral gas consists of dinitrogen.

Advantageously, the cover of the loading / unloading opening is attached directly or indirectly to the primary membrane of the main structure.

According to one embodiment, when said cover is attached directly to the primary membrane of the main structure, the attachment is made by welding. According to another embodiment, when said cover is indirectly fixed to the primary membrane, the fixing is provided by means of a connecting piece welded in a sealed manner to the waterproofing membrane of the main structure and the lid.

Advantageously, the cover consists of:

- a plurality of flat metal plates, the flat metal plates being assembled to each other, in an iron and nickel alloy having a thermal expansion coefficient of between 0.5.10 ⁶ and 2.10 ⁶ K ¹ , or

a plurality of corrugated metal sheets, the corrugated metal sheets being juxtaposed in a repeated pattern and welded together in a sealed manner, the metal sheets being made of stainless steel. Here, it is noted that these corrugated metal sheets can consist of a high manganese steel, the term "stainless steel" comprising such an alloy.

The invention relates to a ship for the transport of a cold liquid product, the ship comprising a double hull and a storage facility as described above arranged in the double hull.

The invention also relates to a transfer system for a cold liquid product, the system comprising a vessel as described above, insulated pipes arranged so as to connect the tank installed in the hull of the vessel to an external installation floating or terrestrial storage and a pump for driving a flow of cold liquid product through the insulated pipes from or to the external floating or terrestrial storage installation to or from the vessel's tank.

Finally, the present invention relates to a method for loading or unloading a ship as described above, in which a cold liquid product is conveyed through insulated pipes from or to an external floating storage installation or land to or from the vessel's tank.

The invention will be better understood, and other aims, details, characteristics and advantages thereof will emerge more clearly during the description. following several particular embodiments of the invention, given purely by way of illustration and not by way of limitation, with reference to the accompanying drawings.

[0035] [Fig.1] Figure 1 is a schematic sectional view of a liquid dome according to one embodiment of the invention.

[0036] [fig.2] Figure 2 is a schematic sectional view of a conventional human access, according to the state of the art, fitted to a liquid dome.

[0037] [Fig.3] Figure 3 shows, in section, a very first sequence of placing the human access in a liquid dome according to the invention.

[0038] [Fig.4] Figure 4 shows, in section, a sequence subsequent to that shown in Figure 3, with the establishment of a sealed enclosure covering the external removable wall of the man's access.

[0039] [Fig.5] Figure 5 is a sectional view of a man's access and its sealed enclosure according to the invention, following the sequences shown in Figures 3 and 4.

[0040] [Fig.6] Figure 6 is a schematic sectional view of a conventional hardware access, according to the state of the art, equipping a liquid dome.

[0041] [Fig.7] Figure 7 shows, in section, a very first sequence of setting up a hardware access in a liquid dome according to the invention.

[0042] [Fig.8] Figure 8 shows, in section, a sequence subsequent to that shown in Figure 6, with the establishment of an enclosure covering the external removable wall of the hardware access.

[0043] [fig.9] Figure 9 is a sectional view of a hardware access and its enclosure according to the invention, following the sequences shown in Figures 7 and 8.

[0044] [Fig.10] Figure 10 is a cutaway schematic representation of an LNG vessel storage facility and a loading / unloading terminal of this tank.

The term "vertical" here means extending in the direction of the earth's gravity field. The term "horizontal" here means extending in a direction perpendicular to the vertical direction. In Figure 1, there is schematically shown a storage installation 1 comprising a double supporting structure composed of an internal supporting structure 2 and an external supporting structure 3 flanking the internal supporting structure 2. At the inside the internal supporting structure 2, the storage installation 1 comprises a sealed and thermally insulating tank 71 which will be described below.

The internal supporting structure 2 and the external supporting structure 3 comprises a plurality of walls connected to each other and in particular an inner upper bearing wall 4 and an outer upper bearing wall 5 respectively, which are located, as can be seen in figure 1, at the top of the storage installation 1.

When the storage facility 1 is positioned on a ship such as an LNG carrier, the supporting structure 2, 3 is formed by the double hull of the ship. The upper internal load-bearing wall 4 is thus called the internal deck 4 of the ship while the upper external load-bearing wall 5 is called the external deck 5 of the ship.

The tank 71 comprises a main structure formed of a bottom wall (not shown), a ceiling wall 7, two cofferdam walls 8 connecting the bottom wall to the ceiling wall 7 and located at the front and at the rear when the storage installation 1 is located on a ship, two side walls (not shown) and optionally two to four chamfer walls (not shown) connecting the side walls to the bottom wall or to the wall ceiling 7. The walls of the tank 71 are thus connected to each other so as to form a polyhedral structure and to define an internal storage space.

In order to load and unload the tank 71 with liquefied gas, the storage installation 1 comprises a loading / unloading opening 10 locally interrupting the upper outer bearing wall 5, the upper inner bearing wall 4 and the ceiling wall 7 of the tank 71 so as to allow the loading / unloading pipes, not shown in the appended figures, to reach the bottom of the tank 71 by passing through this opening 10.

The storage installation 1 also comprises a loading / unloading tower, not shown in the accompanying figures, located at right of the opening 10 and inside the tank 71 forming a support structure for the loading / unloading pipes, not visible in the appended figures, over the entire height of the tank 71 as well as for the pumps, not shown in the accompanying figures.

In addition, the storage installation 1 comprises a cover 12 disposed in the loading / unloading opening 10 in order to close the internal storage space at the level of said opening 10. The cover 12 includes access allowing the loading / unloading lines to pass through the cover 12 as well as two through accesses 20, 30, one called the man access 20 and the other called the material access 30.

The tank 71 also comprises a chimney 15 located on the main structure at the level of the opening 10 and allowing the tank walls to extend continuously from the internal bridge 4 to the external bridge 5 at the level where they are. interrupted by the loading / unloading opening 10. For liquefied gas storage tanks such a chimney 15 provided in particular with said cover 12 is called: the liquid dome.

The loading / unloading opening 10 as well as the chimney 15 has a rectangular or square outline. The chimney 15 thus comprises four walls, one being the extension of the rear cofferdam wall 8, as visible in FIG. 1, while the other three are connected to the ceiling wall 7 and form an angle of 90 ° with this one.

The tank 71 is a membrane tank for storing liquefied gas. The main structure of the tank 71 comprises a multilayer structure comprising, from the outside to the inside, a secondary thermally insulating barrier 16 comprising insulating elements, resting against the supporting structure, a secondary waterproofing membrane 17 resting against the barrier. secondary thermally insulating 16, a primary thermally insulating barrier 18 comprising insulating elements, resting against the secondary waterproofing membrane 17 and a primary waterproofing membrane 19 intended to be in contact with the liquefied gas contained in the tank 71. [0056] According to one embodiment, the main structure of the tank 71 is conducted using the technology Mark III ^®, which is described especially in document FR-A-2691520.

In such a main structure, the secondary thermally insulating barrier 16, the primary thermally insulating barrier and the secondary waterproofing membrane 17 essentially consist of panels juxtaposed on the supporting structure, which may be the internal supporting structure 2 or the structure connecting the upper internal load-bearing wall 4 to the upper external load-bearing wall 5 at the level of the opening 10. The secondary waterproofing membrane 17 is formed of a composite material comprising an aluminum sheet sandwiched between two sheets of fiberglass fabric. The primary waterproofing membrane 19 is for its part obtained by assembling a plurality of metal plates, welded to each other along their edges, and comprising corrugations, not visible in the appended figures, extending in two directions. perpendicular directions. The metal plates are, for example, made of stainless steel or aluminum sheets, shaped by bending or by stamping.

[0058] Other details of such a corrugated metal membrane are described in particular in FR-A-2861060.

In the chimney 15, the secondary waterproofing membrane 17 is fixed at its end to the supporting structure by means of a connecting ring 21 projecting from the internal surface of the supporting wall of the chimney being in this area a wall connecting the internal bridge 4 to the external bridge 5.

The cover 12 has, in the upper part, a multilayer structure comprising an upper cover wall 22 and a thermal insulation structure 24. The opening 10 also includes stiffeners 25 located on the upper cover wall 22.

The upper wall of the cover 22 is fixed in a sealed manner to the outer bridge 5 all around the opening 10 so that it is the upper wall of the cover 22 which acts as a secondary sealing membrane 17. The top wall of cover 22 is made using a metallic material, for example stainless steel. The cover 12 is sealed to the primary waterproofing membrane 19 of the chimney 15, here using a connecting piece 26. It is also possible to provide that the cover 12 is welded directly to the waterproofing membrane 19 of the chimney 15.

The thermal insulation structure 24 and in the upper part of the chimney 15, at the level of the cover 12 and the opening 10, comprises a plurality of insulating elements juxtaposed to each other which may be of similar or different constitution. . These may be so-called "structural" insulating elements essentially having properties or mechanical strength characteristics that are superior, or even much superior, to so-called "non-structural" insulating elements. The structural insulating elements can be high density polymer foam blocks optionally reinforced with fibers or plywood or composite boxes filled with insulating padding such as glass wool, polymer foam or perlite. The non-structural insulating elements can be low density polymer foam blocks or glass wool.

As can be seen in Figure 1, the man access 20 and the hardware access 30 comprises according to the invention respectively a first sealed enclosure 41 and a second sealed enclosure 42. The outer ends 46, 47 respectively of the first and of the second access 20, 30 open, in the upper part, outside the tank 71 while the internal ends 48, 49 respectively of the first and of the second access 20, 30 open, in the lower part, into the tank 71.

The human access 20 and the hardware access 30 as well as their respective sealed enclosures 41, 42, are described in more detail in the following figures.

[0066] Figure 2 shows a human access according to the state of the art. Such a man's access 20 is provided with an outer end 46 and an inner end 48, the outer end 46 being closed or closed off by a removable sealed outer wall 50. Thermal insulation 52, for example of polymeric foam, or glass wool, is provided between the outer 46 and inner 48 ends of the manhole 20.

As can be seen in Figure 3, the human access 20 consists of a block, or a unitary assembly, insertable into the dedicated space in the upper part of the chimney 15 forming the liquid dome. Thus, when it is necessary or useful to allow an operator to enter the tank 71, this block forming the man's access 20 is removed, by first removing the mechanical fasteners from its removable external part 50, to allow its passage. in the tank 71.

In Figure 3, in addition to the stiffeners 25 conventionally present on the outer face of the liquid dome, it is apparent a fixed wall 55 (semi) circular having a greater diameter of at least several centimeters, or even several tens of centimeters. , to the diameter of the access 20. This wall 55 is added to the external face of the liquid dome, for example by welding, to form a connection part of the fixed wall of the first sealed enclosure 41.

As is apparent in Figures 4 and 5, a removable enclosure wall 56, forming a cover, is placed on the upper end, in other words the periphery, of the wall 55, possibly extended by a fixed wall 57 of the first enclosure 41, as visible in Figure 5. The external removable enclosure wall 56 is sealed by screws or bolts, preferably by adding at least one seal, to the fixed wall 55, 56 also forming the sealed enclosure 20. The diameter of the removable enclosure wall 56 is at least 10% greater than the diameter of the removable outer wall 50 of the manhole 20 so that a operator can enter the tank 71, first by removing the removable enclosure wall 56 and then by removing or removing the fasteners from the removable external wall 50 so as to remove the block forming the man access 20.

The fixed wall 55 as well as the external removable enclosure wall 56 of the first enclosure 41 are advantageously made of stainless steel.

The sealed enclosure 41 comprises at least one communication passage 58 allowing communication of the neutral gas present in the enclosure 41 to communicate with the gas present in the thermal insulation space formed by the primary thermally insulating barriers 18 and secondary 16 of the main structure of the tank 71. The section of the communication passage 58 may be circular, rectangular or else oblong.

Preferably, the neutral gas initially present in the enclosure 41 is the same as that filling the thermal insulation space formed by the barriers. thermally insulating primary 18 and secondary 16 of the tank. Given the presence of this or these communication passages 58, once the storage installation 1 has been mounted in a structure such as a ship 70, the thermal insulation space formed by the primary thermally insulating barriers 18 is filled. and secondary 16 of the tank 71 with the neutral gas so that the chamber 41 is filled with neutral gas via the communication passage or passages 58.

Like Figure 2, Figure 6 shows conventional hardware access 30 according to the state of the art. The hardware access 30 consists of a block, otherwise a unitary assembly, insertable into the dedicated space in the upper part of the chimney 15 forming the liquid dome. Thus, when it is necessary or useful to make material penetrate into the tank 71, this block forming the material access 30 is removed to allow its passage into the tank 71.

The hardware access 30 has a rectangular cross section and an external removable sealed wall 60 forming a cover for this hardware access 30. The removable external wall 60 of the hardware access 30 is fixed in a sealed manner using bolts or screws to a protruding portion issuing from the outer face of the liquid dome and has a cross section of shape identical to that of the outer removable wall 60. When it is desired to remove the material access 30, the fasteners of the external removable waterproof wall 60 so that the block can be removed, as can be seen in Figure 7.

Furthermore in Figure 7 is visible a fixed wall 61 belonging to the second sealed enclosure 42 extending in height beyond the external removable outer wall 60 of the hardware access 30. This fixed wall 61 may consist of at least in part, like the fixed wall 55 of the first enclosure 20, in a stiffener 25 conventionally present on the upper or external face of the liquid dome. As is apparent in Figure 8, this wall 61 is intended to receive the removable enclosure wall 65, the latter 65 being sealed by means of screws or bolts, possibly with an additional sealing gasket.

The fixed wall 61 as well as the external removable enclosure wall 65 of the second enclosure 42 are advantageously made of stainless steel. The dimensions - here considering only the width and the length - of the removable enclosure wall 65 are greater by at least 10% than those of the removable outer wall 60 of the hardware access 30 so that material can easily enter the tank 71, first by removing the removable enclosure wall 65 and then by removing the fasteners from the removable outer wall 60 to remove the block forming the material access 30.

As is apparent in Figures 8 and 9, the second sealed enclosure 42 for hardware access 30 comprises at least two communication passages 66 allowing communication of the neutral gas present in the enclosure 42 with the space d thermal insulation of the main structure formed by the primary 18 and secondary 16 thermally insulating barriers of the tank 71 so that the neutral gas of the chamber 42 and that of the main structure mix. The characteristics relating to this neutral gas in the sealed enclosure 42 are advantageously identical to those of the neutral gas present in the sealed enclosure 41.

FIG. 10 represents an example of a maritime terminal comprising a loading and unloading station 75, an underwater pipe 76 and an onshore installation 77. The loading and unloading station 75 is a fixed off-shore 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 swiveled and adapts to all types of equipment. LNG carrier templates. 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 underwater pipe 76 to the loading or unloading station 75. The underwater 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 loading and unloading operations.

To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the vessel 70 and / or pumps fitted to the vessel are used. the shore installation 77 and / or the pumps fitted to the loading and unloading station 75.

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 come within the scope of the invention.

The use of the verb "to include", "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 between parentheses cannot be interpreted as a limitation of the claim.

Claims

[Claim 1] Storage installation (1) for liquefied gas comprising a supporting structure (2, 3) and a sealed and thermally insulating tank (71) arranged in the supporting structure (2, 3), the tank (71) sealed and thermally insulating comprising a main structure formed by a plurality of tank walls connected to each other and fixed to the supporting structure (2, 3), the main structure defining an internal storage space, the main structure comprising at least one membrane of 'sealing (17, 19) and at least one thermally insulating barrier (16, 18), the thermally insulating barrier (16, 18) being placed between the waterproofing membrane (17, 19) and the supporting structure (2, 3) ); the supporting structure (2, 3) comprising a substantially planar upper supporting wall (4, 5); the waterproofing membrane (17, 19), the thermally insulating barrier (16, 18) of the main structure and the upper load-bearing wall (4, 5) being interrupted locally so as to define a loading / unloading opening (10) comprising at least a first and a second removable through access (20, 30) having an internal (48, 49) and external (46, 47) end, the external end (46, 47) being provided with an external removable wall (50), characterized in that the installation (1) comprises at least a first sealed enclosure (41) enveloping the outer end (46) of the first access (20), the external removable wall (50) of the first access ( 20) forming a wall of said first enclosure (41), and in that the first enclosure (41) is filled with a so-called neutral gas.

[Claim 2] Storage installation (1) according to claim 1, wherein the installation comprises a second sealed enclosure (42) enveloping the outer end (47) of the second access (30), the outer removable wall (60). of the second access (30) forming a wall of said second enclosure (42), the second enclosure (42) being filled with the so-called neutral gas.

[Claim 3] A storage installation (1) according to claim 2, in which the first and / or the second enclosure (41, 42) is / are fixed (s) by sealed welding on the external surface of the storage installation. (1).

[Claim 4] A storage installation (1) according to claim 2 or 3, wherein the first and second enclosures (41, 42) respectively comprise a first and second removable enclosure walls (56, 65) having substantially dimensions. greater than those respectively of the aforesaid first and of the aforesaid second external removable walls (50, 60) of the first and of the second access (20, 30).

[Claim 5] Storage installation (1) according to one of claims 2, 3 or 4, wherein the external removable walls (50, 60) of the first and second access (20, 30), preferably as well as the first and second removable enclosure walls (56, 65), are fixed in a sealed manner by mechanical means, for example screws or bolts.

[Claim 6] Storage installation (1) according to one of claims 2, 3, 4 or 5, wherein the loading / unloading opening (10) comprises a cover (12) forming a primary sealing membrane, the first and second access (20, 30) passing through said cover (12) of the loading / unloading opening (10) and being sealed, preferably by welding, to said cover (12).

[Claim 7] Storage installation (1) according to one of claims 2 to 6, in which the first and / or the second enclosure (41, 42) has at least one communication passage (58, 66) with the barrier thermally insulating (16, 18) of the main structure.

[Claim s] Storage facility (1) according to any one of the preceding claims, in which the so-called neutral gas consists of dinitrogen.

[Claim 9] A storage facility (1) according to claim 6, wherein the cover of the loading / unloading opening (10) is attached directly or indirectly to the primary membrane (19) of the main structure.

[Claim 10] A storage facility (1) according to claim 9, wherein, when said cover is attached directly to the primary membrane of the main structure, the attachment is made by welding.

[Claim 11] Storage installation (1) according to claim 9, wherein, when said cover (12) is indirectly fixed to the primary membrane (19), the fixing is provided by means of a connecting piece ( 26) sealed to the waterproofing membrane (19) of the main structure and to the cover (12).

[Claim 12] A storage facility (1) according to any one of claims 9 to 11, wherein the cover (12) consists of:

a plurality of corrugated metal sheets, the corrugated metal sheets being juxtaposed in a repeated pattern and welded together in a sealed manner, the metal sheets being made of stainless steel.

[Claim 13] Ship (70) for transporting a cold liquid product, the ship comprising a double hull (72) and a storage facility (1) according to one of claims 1 to 12 arranged in the double hull.

[Claim 14] A transfer system for a cold liquid product, the system comprising a vessel (70) according to claim 13, insulated pipes (73, 79, 76, 81) arranged so as to connect the vessel (71) installed in the hull of the ship to an external floating or onshore storage facility (77) and a pump for driving a flow of cold liquid product through insulated pipelines from or to the external floating or onshore storage facility to or from the vessel of the vessel. ship.

[Claim 15] A method of loading or unloading a ship (70) according to claim 13, in which a cold liquid product is conveyed through insulated pipes (73, 79, 76, 81) from or to an external installation of floating or terrestrial storage (77) to or from the vessel of the vessel 71;