FR3109978A1 - Liquid dome of a liquefied gas storage tank with an opening with an additional hatch - Google Patents

Abstract

Liquid dome of a storage tank for liquefied gas comprising an opening fitted with an additional hatch. The invention relates to a storage installation (1) for liquefied gas and a sealed and thermally insulating tank (71) comprising a loading/unloading 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) comprises at least one first sealed enclosure (41) enveloping the external end of the first access (20), the removable wall external 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. Figure for abstract: Fig. 1

Description

Liquid dome of a storage tank for liquefied gas comprising an opening fitted 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) having for example a temperature between -50°C and 0°C, or for the transport of Liquefied Natural Gas (LNG) at around -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 used as fuel for the propulsion of the floating structure.

The document FR2991430 describes a storage facility for liquefied gas comprising a sealed and thermally insulating tank integrated into a supporting structure consisting of the double hull of a ship. Each wall of the tank comprises a secondary thermally insulating barrier, a secondary sealing membrane, a primary thermally insulating barrier and a primary sealing 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 support structure is locally interrupted so as to delimit a loading/unloading opening intended to be traversed by fluid loading/unloading pipes. This loading/unloading opening, called Liquid Dome, comprises an insulation or thermally insulating barrier as well as an element forming a primary sealing membrane.

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 then a secondary thermal insulation barrier and finally the walls of the supporting structure. Indeed, in this zone of the tank, it is considered that the outer wall of the liquid dome, whose free outer face opens onto the upper deck or even the inner deck (also called "inner deck"), forms in itself the secondary waterproofing membrane.

After various experiments and tests, the applicant has observed that there are areas of weakness at the level of 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 that are 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.

The applicant intends to remedy these shortcomings observed by proposing a solution that is simple, inexpensive and above all makes it possible to ensure perfect sealing, both physical and thermal, of the extremely cold fluid contained in the tank.

Thus, the present invention relates to a storage installation for liquefied gas comprising a support structure and a leaktight and thermally insulating tank arranged in the support structure, the leaktight and thermally insulating tank comprising a main structure formed by a plurality of tank walls 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 sealing membrane and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing and the load-bearing structure, the load-bearing structure comprising a substantially planar upper load-bearing wall, the waterproofing membrane, the thermally insulating barrier of the main structure and the upper load-bearing wall being locally interrupted so as to delimit a loading/unloading opening comprising at least one first first and a second removable through access having an internal and external end, the external end being provided with an external removable 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 removable outer 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.

Thus, the applicant has found after multiple tests and analyzes that the access or accesses passing through the loading/unloading opening of the liquid dome present(s) a weakness in the insulation of the tank or of the liquefied gas storage installation. . These accesses are known to those skilled in the art as “man access”, also designated in English as “Man Hole”, and “material access”, also designated in English as “Material Hole”.

Based on these analyses, the applicant proposes a simple, effective and inexpensive system for securing and totally sealing these particular areas. The containment 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 term "through access" is understood to mean that the orifices, that is to say the man's 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.

By convention, the terms "external" and "internal" are used to define the relative position of one element in relation to another, with reference to the inside and outside of the tank.

The expression "neutral gas" means that it is the non-flammable gas used in the thermal insulation space of the tank, namely conventionally molecular nitrogen N ₂ which is usually found mixed with residual gases from the polymer foams and adhesives used to form the thermal insulation barrier of the tank, the latter being present in small quantities compared to the quantity of nitrogen. Of course, it is possible to replace all or part of this molecular nitrogen N ₂ with another non-flammable gas, preferably having qualities of satisfactory thermal non-conductivity. Monitoring the quantity of this neutral gas in the thermal insulation space of the vessel, 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 accesses conventionally present at the level of the liquid dome are provided with such an isolation enclosure, filled with an inert gas. Thus, preferably, the installation comprises a second sealed enclosure enveloping the outer end of the second access, the removable outer wall of the second access forming a wall of said second enclosure, the second enclosure being filled with the so-called neutral gas.

Other advantageous features of the invention are briefly presented below:

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

According to a possibility offered by the invention, the first and second enclosures are insulated by a thermal insulation means such as for example glass wool, polyurethane foam or other material adapted to be housed in said enclosures and having 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 aforementioned first and of the aforementioned second external removable walls of the first and of the second access crossing.

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

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 may prove to be less convenient for the dismantling of these fixed elements.

Thus, the external removable walls of the enclosures are fixed respectively to the two respective external ends of the barrel constituting the through access while the removable enclosure walls are fixed to the fixed envelope of each enclosure, respectively.

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

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

Advantageously, the first and/or the second enclosure has at least one communication passage 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 communication passages with the thermally insulating barrier of the main structure.

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

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

Advantageously, the cover of the loading/unloading opening is fixed 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 fixed indirectly to the primary membrane, the fixing is ensured by means of a connecting piece welded in a leaktight manner to the sealing membrane of the main structure and to the cover. .

• une pluralité de plaques métalliques planes, les plaques métalliques planes étant assemblées les unes aux autres, en un alliage de fer et de nickel présentant un coefficient de dilatation thermique compris entre 0,5.10^-6et 2.10^-6K^-1, ou
• une pluralité de tôles métalliques ondulées, les tôles métalliques ondulées étant juxtaposées selon un motif répété et soudées ensemble de manière étanche, les tôles métalliques étant réalisées en acier inoxydable. Ici, on note que ces tôles métalliques ondulées peuvent consister en un acier haut manganèse, le terme « acier inoxydable » comprenant un tel alliage.

Advantageously, the lid consists of:

• a plurality of flat metal plates, the flat metal plates being assembled together, made of an alloy of iron and nickel 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 repeating pattern and sealed together, 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 transporting a cold liquid product, the ship comprising a double hull and a storage installation 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 ship as described above, insulated pipes arranged so as to connect the tank installed in the hull of the ship to an external floating storage installation or land and a pump to drive a flow of cold liquid product through the insulated pipes from or to the external floating or land storage installation to or from the tank of the ship.

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 or terrestrial storage installation towards or from the vessel's tank.

The invention will be better understood, and other aims, 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 not limitation. , with reference to the accompanying drawings.

Figure 1 is a schematic sectional view of a liquid dome according to an embodiment of the invention.

Figure 2 is a schematic sectional view of a conventional manhole, according to the state of the art, equipping a liquid dome.

FIG. 3 shows, in section, a very first sequence for setting up the man's access in a liquid dome according to the invention.

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

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 then 4.

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

FIG. 7 shows, in section, a very first sequence for setting up a hardware access in a liquid dome according to the invention.

FIG. 8 presents, in section, a sequence subsequent to that presented in FIG. 6, with the establishment of an enclosure covering the external removable wall of the hardware access.

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

FIG. 10 is a cutaway schematic representation of an LNG tanker storage facility and a loading/unloading terminal for 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 shown schematically a storage facility 1 comprising a double support structure composed of an internal support structure 2 and an external support structure 3 framing the internal support structure 2. Inside the internal support structure 2, the storage facility 1 comprises a sealed and thermally insulating tank 71 which will be described later.

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

When the storage facility 1 is positioned on a ship such as an LNG carrier, the load-bearing structure 2, 3 is formed by the double hull of the ship. The inner upper load-bearing wall 4 is thus called the inner deck 4 of the ship while the outer upper load-bearing wall 5 is called the outer 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 bevel walls (not shown) connecting the side walls to the bottom wall or to the ceiling wall 7 The walls of the tank 71 are thus connected to each other so as to form a polyhedral structure and to delimit 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 outer upper load-bearing wall 5, the inner upper load-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 crossing this opening 10.

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

In addition, the storage installation 1 comprises a cover 12 arranged in the loading/unloading opening 10 in order to close off the internal storage space at the level of said opening 10. The cover 12 comprises accesses allowing the loading pipes / unloading to cross the lid 12 as well as two crossing accesses 20, 30, one called the man access 20 and the other called the material access 30.

The tank 71 also includes a chimney 15 located on the main structure at the level of the opening 10 and allowing the walls of the tank to extend continuously from the internal bridge 4 towards the external bridge 5 at the level where these 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.

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 inwards, a secondary thermally insulating barrier 16 comprising insulating elements, resting against the load-bearing structure, a secondary sealing membrane 17 resting against the barrier thermally insulating secondary barrier 16, a primary thermally insulating barrier 18 comprising insulating elements, resting against the secondary sealing membrane 17 and a primary sealing membrane 19 intended to be in contact with the liquefied gas contained in the tank 71.

According to one embodiment, the main structure of the tank 71 is made using Mark III ^® technology which is described in particular in the document FR-A-2691520.

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

Other details of such a corrugated metallic membrane are in particular described in FR-A-2861060.

In the chimney 15, the secondary sealing membrane 17 is fixed at its end to the load-bearing structure by means of a connection ring 21 protruding from the internal surface of the chimney bearing wall being in this zone a wall connecting internal bridge 4 to 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 comprises stiffeners 25 located on the upper cover wall 22.

The lid top wall 22 is tightly fixed to the outer bridge 5 all around the opening 10 so that it is the lid top wall 22 which acts as the secondary sealing membrane 17. The top wall of the lid cover 22 is made using a metallic material, for example stainless steel.

The cover 12 is welded in a sealed manner to the primary sealing membrane 19 of the stack 15, here using a connecting piece 26. It is also possible to provide that the cover 12 is welded directly to the sealing 19 of chimney 15.

The thermal insulation structure 24 and in the upper part of the chimney 15, at the level of the lid 12 and the opening 10, comprises a plurality of insulating elements juxtaposed to each other which may be of similar or different constitution. They may be so-called “structural” insulating elements essentially having properties or mechanical strength characteristics that are superior, or even much superior, to the 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 filling such as glass wool, polymer foam or perlite. The non-structural insulating elements can be low density polymer foam blocks or even glass wool.

As can be seen in Figure 1, the man access 20 and the material access 30 comprises respectively according to the invention 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 second access 20, 30 open, in the lower part, in the tank 71 .

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

Figure 2 shows a man's 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 polymer 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 man 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 have an operator 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 tank 71.

In FIG. 3, in addition to the stiffeners 25 conventionally present on the outer face of the liquid dome, a fixed (semi-)circular wall 55 is apparent, having a diameter greater by at least several centimeters, or even several tens of centimeters, than the diameter access 20. This wall 55 is added to the outer face of the liquid dome, for example by welding, to form a connecting 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 an additional fixed wall 57 of the first enclosure 41, as seen in Figure 5. The external removable enclosure wall 56 is sealed by screws or bolts, preferably by adding at least one seal thereto, to the fixed wall 55, 56 also forming the sealed enclosure 20. The diameter of the removable enclosure wall 56 is greater by at least 10% than the diameter of the removable outer wall 50 of the man's access 20 so that an operator can enter in the tank 71, first by removing the removable enclosure wall 56 then by removing or removing the fasteners from the removable outer wall 50 so as to remove the block forming the manhole 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 18 and secondary 16 thermally insulating barriers. of the main structure of the tank 71. The section of the communication passage 58 can be circular, rectangular or even oblong.

Preferably, the neutral gas initially present in enclosure 41 is the same as that filling the thermal insulation space formed by the primary 18 and secondary 16 thermally insulating barriers of the vessel. 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 tank 71 with neutral gas so that enclosure 41 is filled with neutral gas via communication passage(s) 58.

Like FIG. 2, FIG. 6 represents a conventional hardware access 30 according to the state of the art. The material 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 introduce material 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 screw to a protruding portion coming from the outer face of the liquid dome and has a 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 outer removable waterproof wall 60 so that the block can be removed, as can be seen in Figure 7.

Furthermore in FIG. 7 is visible a fixed wall 61 belonging to the second sealed enclosure 42 extending in height beyond the external removable external wall 60 of the material access 30. This fixed wall 61 can consist of at least part, like the fixed wall 55 of the first enclosure 20, in a stiffener 25 conventionally present on the upper or outer 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 mounted tightly by means of screws or bolts, possibly an additional seal.

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 external wall 60 of the material access 30 so that material can penetrate easily in the tank 71, first by removing the removable enclosure wall 65 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 material access 30 comprises at least two communication passages 66 allowing communication of the neutral gas present in the enclosure 42 with the thermal insulation space 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 enclosure 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 pipeline 76 and an onshore installation 77. The loading and unloading station 75 is a fixed off-shore installation comprising an 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 pipes 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 shore installation 77. This 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 great 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 ship 70 and/or pumps fitted to the shore installation 77 and/or pumps fitted to the loading and unloading station 75 are used.

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 invention.

The use of the verb "to comprise", "to understand" or "to include" and of 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 support structure (2, 3) and a sealed and thermally insulating tank (71) arranged in the support structure (2, 3),
the sealed and thermally insulating tank (71) comprising a main structure formed by a plurality of tank walls connected to each other and fixed to the support structure (2, 3), the main structure defining an internal storage space, the structure main comprising at least one sealing membrane (17, 19) and at least one thermally insulating barrier (16, 18), the thermally insulating barrier (16, 18) being placed between the sealing membrane (17, 19) and the support structure (2, 3);
the load-bearing structure (2, 3) comprising an upper load-bearing wall (4, 5) which is substantially planar;
the sealing 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 delimit 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 one first sealed enclosure (41) enveloping the outer end (46) of the first access (20), the removable outer 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. Storage installation (1) according to claim 1, in which the installation comprises a second sealed enclosure (42) enveloping the external end (47) of the second access (30), the external 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. Storage installation (1) according to claim 2, in which the first and/or the second enclosure (41, 42) is/are fixed by tight welding on the external surface of the storage installation (1). Storage installation (1) according to Claim 2 or 3, in which the first and the second enclosures (41, 42) respectively comprise a first and second removable enclosure walls (56, 65) having dimensions substantially greater than those respectively of the aforementioned first and of the aforementioned second external removable walls (50, 60) of the first and of the second access (20, 30). Storage installation (1) according to one of Claims 2, 3 or 4, in which the external removable walls (50, 60) of the first and of the second access (20, 30), preferably as well as the first and second removable enclosure walls (56, 65), are fixed tightly by mechanical means, for example screws or bolts. Storage installation (1) according to one of Claims 2, 3, 4 or 5, in which the loading/unloading opening (10) comprises a cover (12) forming a primary sealing membrane, the first and second accesses (20, 30) passing through said lid (12) of the loading/unloading opening (10) and being fixed in a sealed manner, preferably by welding, to said lid (12). 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 thermally insulating barrier (16 , 18) of the main structure. Storage installation (1) according to any one of the preceding claims, in which the so-called neutral gas consists of nitrogen. Storage facility (1) according to claim 6, in which the cover of the loading/unloading opening (10) is fixed directly or indirectly to the primary membrane (19) of the main structure. Storage installation (1) according to Claim 9, in which, when the said cover is fixed directly to the primary membrane of the main structure, the fixing is carried out by welding. Storage installation (1) according to Claim 9, in which, when the said cover (12) is fixed indirectly to the primary membrane (19), the fixing is ensured by means of a connecting piece (26) welded to tightly to the sealing membrane (19) of the main structure and to the cover (12). Storage installation (1) according to any one of claims 9 to 11, in which the cover (12) consists of:

• a plurality of flat metal plates, the flat metal plates being assembled together, made of an alloy of iron and nickel 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 repeating pattern and sealed together, the metal sheets being made of stainless steel.

Vessel (70) for transporting a cold liquid product, the vessel comprising a double hull (72) and a storage installation (1) according to one of Claims 1 to 12 arranged in the double hull. Transfer system for a cold liquid product, the system comprising a vessel (70) according to claim 13, insulated pipes (73, 79, 76, 81) arranged to connect the tank (71) installed in the hull of the vessel to an external floating or onshore storage facility (77) and a pump for driving a flow of cold liquid product through the insulated pipes from or to the external floating or onshore storage facility to or from the ship's tank. 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 floating or terrestrial storage installation (77) to or from the ship's tank (71).