Liquefied gas storage facility

Abstract

The invention relates to a storage installation comprising a load-bearing structure including an upper load-bearing wall and the tank including a ceiling wall fixed to the upper load-bearing wall, the load-bearing structure including a dome structure including dome walls projecting from the upper load-bearing wall and each including an upper end, the dome structure including a seat wall fixed to the upper ends, the dome structure including a cover that covers the passage and is hermetically welded to the seat wall, the cover including a peripheral edge having a bevel oriented such that the cover narrows from an upper face of the cover to an lower face of the cover, the peripheral edge being welded to an intermediate frame by a lap weld located in a space between the bevel of the peripheral edge and an upper face of the intermediate frame. Figure for the abstract: 4.

Description

Title of the invention: Liquefied gas storage installation technical field

[0001] The invention relates to a liquefied gas storage installation comprising a sealed and thermally insulated tank arranged in a load-bearing structure.

[0002] In particular, the invention relates to the field of sealed and thermally insulated tanks for the storage and / or transport of liquefied gases at low temperatures, such as tanks for transporting Liquefied Petroleum Gas (also called LPG) at temperatures ranging, for example, from -50°C to 0°C, or for transporting Liquefied Natural Gas (LNG) at approximately -162°C. These tanks can be installed on land or on a floating structure. In the case of a floating structure, the tank can be used for transporting liquefied gas or for receiving liquefied gas to serve as fuel for the propulsion of the floating structure.

[0003] The invention relates more particularly to a storage installation of the aforementioned type comprising a dome structure projecting upwards from an upper load-bearing wall of the load-bearing structure and intended to be crossed by at least one pipe intended for loading or unloading the tank. Technological background

[0004] Document WO2022 / 253615 discloses a liquefied gas storage installation comprising a supporting structure, consisting of the double hull of a ship, and a sealed and thermally insulated tank arranged within the supporting structure. The installation includes a dome structure, shown in [Fig. 1] of the aforementioned document, which serves as an entry point for various tank equipment, such as lines for loading or unloading the tank. The dome structure includes a vertical load-bearing wall, projecting upwards from an upper load-bearing wall of the supporting structure, and a horizontal wall positioned on top of the vertical load-bearing wall as shown in [Fig. 7] of the aforementioned document. The horizontal wall comprises a seat wall and a metal lid wall welded tightly to the seat wall.

[0005] To secure the horizontal wall of the dome structure and the metal lid wall and ensure the dome structure is watertight, it is known to secure the metal lid wall to an intermediate frame by means of a weld line and to weld said intermediate frame to the horizontal wall of the dome structure by means of one or more other weld lines. When the pressure inside the tank is greater than atmospheric pressure, this pressure differential exerts an outward force on the lid. The tank puts bending stress on the metal lid wall. Such stresses are likely to degrade the aforementioned weld lines and thus lead to sealing problems in the dome structure, particularly when the tank is intended to store gas at pressures higher than those of traditional membrane tanks.

[0006] Such a dome structure arrangement is therefore not entirely satisfactory. Summary

[0007] One idea at the heart of the invention is therefore to propose a liquefied gas storage installation comprising a dome structure which offers better pressure resistance.

[0008] To this end, according to one embodiment, the invention provides a liquefied gas storage installation comprising a load-bearing structure and a sealed and thermally insulated tank arranged in the load-bearing structure, the load-bearing structure comprising an upper load-bearing wall and the tank comprising a ceiling wall fixed to the upper load-bearing wall, the upper load-bearing wall and the ceiling wall being locally interrupted so as to delimit an opening, the load-bearing structure comprising a dome structure projecting vertically outwards from the upper load-bearing wall around the opening and defining a passage intended to be traversed by at least one pipe for loading or unloading liquefied gas from the tank, the dome structure comprising: dome walls projecting from the upper load-bearing wall and each comprising an upper end,a seat wall fixed at the upper ends and extending horizontally, a cover that covers the passage, and includes a peripheral edge, an intermediate frame situated between the seat wall and the peripheral edge, the peripheral edge having a first bevel oriented such that the cover narrows from an upper face of the cover to a lower face of the cover, the peripheral edge being welded to the intermediate frame by a weld situated in a space between the first bevel and an upper face of the intermediate frame, the intermediate frame being welded to the seat wall, the intermediate frame having an external peripheral end that is welded to the seat wall by a second weld.

[0009] Thus, thanks to the bevel, with a constant dimension between the peripheral edge of the cover and the external peripheral end of the intermediate frame, the throat depth of the first weld can be greater, which improves its holding power.

[0010] For example, one or all of the welds are lap welds. In particular, the weld between the bevel and an upper face of the intermediate frame is a lap weld in a particular embodiment.

[0011] Furthermore, the bevel allows the lid to be positioned on the intermediate frame with greater flexibility in adjustment.

[0012] Furthermore, for a constant actual throat depth of the first weld, the horizontal dimension of said weld is reduced. Thus, while maintaining a sufficient gap between the first and second welds to prevent them from merging during welding operations, the majority of the volume of the first lap weld is closer to the second weld. The inventors have observed that bringing the aforementioned welds closer together allows for a better distribution of stresses within said welds, thereby improving their strength and, ultimately, improving the attachment of the cover to the dome.

[0013] According to embodiments, such an installation may include one or more of the following characteristics.

[0014] According to one embodiment, the intermediate frame has a second bevel oriented such that the intermediate frame narrows from the upper face of the intermediate frame to a lower face of the intermediate frame, the second weld being located in a space between the bevel and an upper face of the seat wall.

[0015] According to one embodiment, a distance between an external peripheral end of a top face of the intermediate frame and an upper end of the peripheral edge of the cover is between 5 and 40 mm, for example between 10 and 20 mm.

[0016] According to one embodiment, an angle of the first bevel is between 45 and 90° excluding bounds, the angle being located between the upper face of the cover and a face of the first bevel connecting the upper face of the cover to the lower face of the cover and / or the angle being located between the upper face of the intermediate plate and a face of the first bevel connecting the upper face of the cover to the lower face of the cover.

[0017] According to one embodiment, the first weld has an actual throat depth of between 5 and 25 mm.

[0018] According to one embodiment, a distance between an external end of the first weld and the peripheral external end of an upper face of the intermediate frame is between 1 and 20 mm; the distance being measured in a plane of the intermediate frame.

[0019] This allows the first and second welds to be positioned close enough to each other without the risk of them amalgamating, which would significantly degrade their strength.

[0020] According to one embodiment, a distance between an external end of the lower face of the cover and the peripheral external end of an upper face of the intermediate frame is between 5 and 25 mm.

[0021] Similarly, this allows the first and second welds to be positioned sufficiently close to each other without risk of them amalgamating, which would have which has the effect of significantly degrading their strength, while allowing the stress to be distributed in such a way that the welds work together.

[0022] According to one embodiment, the dome structure comprises a frame formed by frame walls that are welded against the upper face of the lid and reinforcing gussets that are each positioned to bear against an external face of a frame wall and against the upper face of the lid.

[0023] Thus, the frame and the gussets make it possible to reinforce the rigidity of the cover, which makes it possible to limit its flexing and thus improve the resistance to pressure of the welds ensuring the attachment of the cover to the seat wall.

[0024] According to one embodiment, the reinforcing gussets comprise a body disposed perpendicular to the frame wall, the body having a heel by which said body rests against the upper face of the cover and a chamfered portion extending from the heel, the reinforcing gusset further comprising a reinforcing plate positioned on the chamfered portion perpendicular to a plane of the body.

[0025] According to one embodiment, a lower end of the reinforcement plate extends to an upper end of the heel.

[0026] According to one embodiment, the dome structure further comprises a plurality of horizontal stiffeners positioned in support against an upper face of the cover, each horizontal stiffener being aligned with a reinforcing gusset in the same plane normal to the cover.

[0027] According to one embodiment, the dome structure further comprises a plurality of vertical stiffeners positioned in support against an external face of a frame wall and against an underside of the seat wall, each vertical stiffener being aligned with a reinforcing gusset in the same plane.

[0028] According to one embodiment, a distance between a lower end of the reinforcement plate and the upper face of the cover is between 10 and 100 mm.

[0029] In one embodiment, the reinforcement plate is generally rectangular in shape and includes upper corners, each with a chamfer. In this embodiment, the rectangle forming the general rectangular shape has sides measuring 400 mm or less. The chamfered corners facilitate handling operations. For example, they facilitate the passage of a welding torch.

[0030] It is also possible to provide a general shape that is not rectangular. For example, the reinforcing plate can be of general elliptical, square, triangular, or trapezoidal shape.

[0031] Moreover, here too, the dimensions of the general shape - whatever it may be - are less than 200 mm; the dimensions being measured from a neutral fiber of the chamfered portion.

[0032] According to one embodiment, a distance between the heel and an upper end the peripheral edge of the lid is between 10 and 75mm.

[0033] According to one embodiment, the thickness of the intermediate frame is between 5 and 40 mm and / or the thickness of the cover is between 15 and 40 mm.

[0034] According to one embodiment, the invention relates to a vessel for the transport of a fluid which includes an installation of the aforementioned type.

[0035] According to one embodiment, the ship comprises a double hull which forms the load-bearing structure.

[0036] According to one embodiment, the invention also provides a transfer system for a fluid, the system comprising the aforementioned vessel, insulated pipes arranged to connect the vessel's tank to a floating or land-based storage facility and a pump to drive a flow of fluid through the insulated pipes from or to the floating or land-based storage facility to or from the vessel's tank.

[0037] According to one embodiment, the invention also provides a method for loading or unloading such a vessel, in which a fluid is conveyed through insulated pipes from or to a floating or land-based storage facility to or from the vessel's tank. Brief description of the figures

[0038] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from 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.

[0039] [Fig-1] Fig. 1 is a schematic perspective view of a load-bearing structure designed to support a sealed and thermally insulated tank for storing a liquefied gas.

[0040] [Fig.2] Fig.2 is a schematic view of the multilayer structure of the walls of the tank.

[0041] [Fig.3] The [Fig.3] is a top perspective view of the dome structure.

[0042] [Fig.4] Fig.4 is a schematic cross-sectional view illustrating the attachment of the cover of the dome structure on the seat wall via the intermediate frame.

[0043] [Fig. 5] Fig. 5 is a perspective view of the dome structure frame and the Reinforcing gussets.

[0044] [Fig.6] Fig.6 is a top perspective view of the dome structure (the Reinforcing gussets are not shown).

[0045] [Fig.7] [Fig.7] is a diagram of the geometry of the weld of the cover without bevel on the intermediate frame.

[0046] [Fig.8] Fig.8 is a diagram illustrating, for comparison purposes, the geometry of the welding when the bevel of the cover presents an angle of 45°, on the one hand, and when the bevel presents an angle of 60°, on the other hand.

[0047] [Fig.9] The [Fig.9] is a diagram illustrating an alternative embodiment in which the intermediate frame has a bevel.

[0048] [Fig. 10] [Fig. 10] is a schematic cutaway representation of a tank of an LNG carrier and a loading / unloading terminal for this tank. Description of embodiments

[0049] In relation to [Fig. 1], a load-bearing structure 1 is described against which a sealed and thermally insulated liquefied gas storage tank 2 is intended to be fixed. The load-bearing structure 1 is, for example, formed by the double hull of a ship. The load-bearing structure 1 has a generally polyhedral shape. It has two forward and aft load-bearing walls 120, here octagonal in shape, of which only the aft load-bearing wall is shown in [Fig. 1]. The forward and aft walls 120 are, for example, cofferdam walls of the ship that extend transversely to the longitudinal direction of the ship. The load-bearing structure 1 also includes an upper load-bearing wall 3 to which a ceiling wall of the tank 2 is fixed, a lower load-bearing wall 40, and lateral load-bearing walls 50, 60, 110, 180, 90, 100.

[0050] The sealed and thermally insulated liquefied gas storage tank comprises a plurality of tank walls which are each anchored against one of the load-bearing walls 120, 3, 50, 60, 110, 180, 90, 100 of the load-bearing structure 1.

[0051] As shown in [Fig.2], each wall of the tank 2 presents successively, from the outside to the inside, according to the thickness direction of the wall, a secondary thermally insulating barrier 12 comprising insulating elements 13 fixed to the supporting structure 1, a secondary sealing membrane 14 anchored to the insulating elements 13 of the secondary thermally insulating barrier 12, a primary thermally insulating barrier 15 comprising insulating elements 16 fixed to the insulating elements 13 of the secondary thermally insulating barrier 12 or to the supporting structure 1 and resting against the secondary sealing membrane 14 and a primary sealing membrane 17 anchored to the insulating elements 16 of the primary thermally insulating barrier 15 and intended to be in contact with the liquefied gas contained in the tank 2.

[0052] As shown in Figures 1 and 6, the upper load-bearing wall 3 and the ceiling wall are locally interrupted so as to delimit an opening 18. The load-bearing structure 1 includes a dome structure 19 which projects upwards from the upper load-bearing wall 3 around the opening and which defines a passage 24 intended to be traversed by one or more conduits 20, 21, 47 intended for the loading or unloading of the tank 2.

[0053] The dome structure 19 comprises vertical dome walls 22. For example, there are four dome walls 22 when the dome structure 19 has a square or rectangular cross-section. The dome walls 22 project upwards from the upper load-bearing wall 3 and rise above the ship's deck. The dome structure 19 also comprises, at the top of the dome walls 22, a seat wall 23 that extends horizontally around the passage 24 formed by the dome walls 22 and thus forms, together with the dome walls 22, a raised platform. The seat wall 23 supports a cover 25 through which passes the pipe(s) 20, 21 intended for loading or unloading the tank 2. As illustrated in Figures 3 and 6, according to one embodiment, the cover 25 comprises a network of stiffeners 48, each of which is formed by metal plates welded against the upper face of the metal cover plate 25.

[0054] Furthermore, the supporting structure 1 also includes stiffeners 49 which are fixed under the seat wall 23 and are supported against the seat wall 23 and against the dome walls 22.

[0055] The multilayer structure of the tank 2, described above in relation to [Fig.2], is also present against the walls of dome 22 but is not present at the level of the lid 25 of the dome structure 19.

[0056] According to one embodiment, each of the conduits 20, 21, 47 is hollow, passes through the lid 25 of the dome structure 19 and forms: - a pipe intended for loading tank 2 with liquefied gas, - a pipe intended for the discharge of liquefied gas from tank 2 and which is therefore associated with a discharge pump fixed to the lower end of said pipe, or - a relief well allowing the descent of a relief pump and a discharge line in case of failure of a discharge pump.

[0057] In relation to [Fig.4], the fixing of the cover 25, and more particularly of its metal plate, to the seat wall 23 is described below.

[0058] The cover 25 is hermetically fixed to the seat wall 23. To achieve this, the cover 25 is hermetically welded to a metallic intermediate frame 28, which is itself previously hermetically welded to the seat wall 23. Advantageously, the intermediate frame 28 is hermetically welded to the seat wall 23 by means of two continuous lap weld lines 29, 30 extending respectively along the inner peripheral edge of the intermediate frame 28 and along the outer peripheral edge of the intermediate frame 28. The actual throat depth of the weld 30 is between 5 and 25 mm. For example, the actual throat depth of the weld 30 is 16.5 mm.

[0059] Furthermore, the cover 25 rests against the upper face of the intermediate frame 28 and is welded, in a watertight manner, by means of a continuous lap weld 8, to the upper face of the intermediate frame 28. To achieve this, a peripheral end 282 of the intermediate frame 28 projects, in the plane of the intermediate frame 28, beyond an upper end of the peripheral edge 33 in order to accommodate the lap weld 8. In one embodiment, a distance d6 between the peripheral end 282 of the intermediate frame 28 and the upper end of the peripheral edge 33 of the cover 25 is between 10 and 20 mm. For example, the distance d6 is 15 mm.

[0060] In the embodiment shown, the intermediate frame 28 rests at least partially against an outer area 32 of the seat wall 23, that is, an area which is positioned, relative to the passage 24, outside the dome walls 22. This outer area 32 also projects, in the plane of the intermediate frame 28, beyond the intermediate frame 28 to accommodate the weld 30. A distance d3 between the peripheral end 282 of the intermediate frame 28 and an end of an outer area 32 of the seat wall 23 is at least 5 mm. For example, the distance d3 is 55 mm. This distance d3 is located in the plane of the seat plate 23.

[0061] Furthermore, as illustrated in [Fig. 4], the peripheral edge 33 is beveled, i.e., it has a bevel 6 oriented so that the cover 25 narrows from its upper face 331 to its lower face 332. The bevel 6 is characterized by an angle α between the upper face 331 of the cover 25 and a face of the bevel 6. The angle α is between 45° and 90°, not including the upper limit. For example, it could be 60° or 70°.

[0062] This bevel 6 forms a space 5 between the peripheral edge 33 of the cover 25 and an upper face 281 of the intermediate frame 28. A distance between the bottom of the space 5 - i.e. the point of contact between the lower face 332 of the peripheral edge 33 and the upper face 281 of the intermediate frame 28 - and an end of the peripheral edge 33 is greater than this same distance measured in the absence of bevel 6.

[0063] The bevel 6 allows, for a constant actual throat depth of the weld 8 between the cover 25 and the intermediate frame 28, the distance d6 between the peripheral end 282 of the intermediate frame 28 and the upper end of the peripheral edge 33 of the cover 25 to be reduced. The actual throat depth of the weld 8 is advantageously between 5 and 25 mm and for example 16.5 mm.

[0064] Since, in general, chamfered plates, i.e., those with a bevel at their end, offer better weld strength, the bevel 6 makes it possible to reduce a distance d5 between an external end of the lower face 332 of the cover 25 and the external peripheral end 282 of the intermediate frame 28. Generally, the distance d5 is greater than 25 mm. Thanks to the bevel 6, the distance d5 is less than or equal to 25 mm, preferably less than or equal to 20 mm.

[0065] The bevel 6 also makes it possible to reduce the distance dl between an external end of the first weld 8 and the external peripheral end 282 of an upper face 281 of the intermediate frame 28 (the distance being measured in a plane of the intermediate frame). Generally, the distance dl is 10 mm.

[0066] Figures 7 to 9 illustrate the reduction of the distance d6 thanks to the bevel 6 according to different values ​​of the angle a according to a first illustrative example.

[0067] An angle α of 90 degrees corresponds to the absence of a bevel 6 and thus serves as a reference to illustrate the reduction of the distance d5. In [Fig. 7], a weld 8, having an actual weld throat G and weld toe P, is shown. The actual throat depth G is 16.5 mm in this illustrative example. The weld toe P, i.e., the weld width, is approximately 23.3 mm.

[0068] In [Fig. 8], a distance d6 defined by a bevel 6 with an angle α of 45 degrees is compared with a distance d6 defined by a bevel 6 with an angle α of 60 degrees. It is observed that, at a constant throat depth (for example, 16.5 mm), the horizontal weld foot P located on the upper face 281 of the intermediate frame 28 decreases as the angle α decreases. For example, the horizontal weld foot P is 23.3 mm with an angle α of 90 degrees, 19 mm with an angle α of 60 degrees, 20 mm for an angle α of 70°, and 17.9 mm for an angle α of 45 degrees.

[0069] Furthermore, in [Fig. 8], a chamfer angle [3], complementary to angle a, is shown. This angle [3] is defined by the normal to the intermediate frame 28 passing through the upper end of the peripheral edge 33 and the face of the bevel 6. It is also possible to define the bevel 6 with the angle [3]. Thus, it can be seen that, at a constant throat depth (for example 16.5 mm), the horizontal weld foot P located on the upper face of the intermediate frame 8 is reduced as the angle [3] increases.

[0070] It is thus observed that there is a decrease in the distances d5, d6 and of the weld foot P when the chamfer angle [3 = (90°- a) increases and this for an identical throat depth.

[0071] By reducing the horizontal weld foot P, it is then possible to reduce the distance d6 and ultimately to bring the inner end of weld 8 closer to weld 30.

[0072] This allows for a better distribution of stresses along the two weld lines 8 and 30. Indeed, the two welds 8 and 30 being closer to each other, without actually joining, they cooperate with each other in order to offer better flexural resistance to the stresses acting on the metal wall of the cover 25.

[0073] Furthermore, the bevel 6 and the resulting space 5 also allow the cover 25 to be positioned on the intermediate frame 28 with greater adjustment latitude. Indeed, thanks to the geometry of the bevel, a gain in flexibility due to the tolerance clearance is observed. during editing.

[0074] According to an embodiment illustrated in [Fig.9], the intermediate frame 28 has a bevel 61 oriented so that the intermediate frame 28 narrows from the upper face 281 of the intermediate frame 28 to a lower face 283 of the intermediate frame 28, the second weld 30 being located in a space 51 between the second bevel 61 and an upper face of the seat wall 23.

[0075] The bevel 61 is characterized by an angle a2 located between the upper face 281 of the intermediate frame 28 and a face of the bevel 61. The angle a2 is between 45° and 90°, not including the upper limit. For example, it can be 60° or 70°. In [Fig. 9], the angle a2 is approximately 45°, just like the angle a. However, the angle a2 is not necessarily equal to the angle a.

[0076] Furthermore, as shown in Figures 3 and 5, the dome structure 19 includes a profiled frame 9. The profiled frame 9 is welded to the upper face 331 of the cover 25, continuously all around it in order to stiffen it.

[0077] As shown in [Fig.5], the frame 9 has an I-shaped section, that is to say, it has a wing 91 which is perpendicular to the cover 25. The wing 91 extends vertically, relative to the cover 25.

[0078] According to an alternative embodiment shown in figures 4 and 5, the dome structure 9 includes reinforcing gussets 10 which each have a first edge bearing against the wing 91 of the frame 9 and a second edge bearing against the cover 25.

[0079] As illustrated in [Fig.5], the reinforcing gussets 10 comprise a body arranged perpendicular to the frame wall 9. The body having a heel 102 by which it rests against the upper face 331 of the cover 25 and a chamfered portion 101 extending from the heel 102.

[0080] In addition, the reinforcing gussets 10 include a reinforcing plate 103 positioned on the chamfered portion 101 perpendicular to a plane of the body.

[0081] The heel 102 of the body of a reinforcing gusset 10 corresponds to the unchamfered portion of the body. As illustrated in [Fig. 4], the heel 102 has a height d2 between the lower end of the reinforcing plate 103 and the upper face 331 of the cover 25. The height d2 of the heel 102 is between 10 and 100. The height of the heel 102 determines, or determines, the chamfer angle of the body of the reinforcing plate 103 and thus the inclination of the reinforcing plate 103 relative to the frame 9 and the reinforcing gusset 10.

[0082] As illustrated in [Fig. 5], the reinforcing plate 103 is generally rectangular in shape. It extends along the entire length of the chamfered portion 101 so that a lower end of the reinforcing plate 103 extends to an upper end of the heel 102.

[0083] The reinforcement plate 103 has dimensions less than or equal to 200 mm; the dimensions being measured from a neutral fiber of the chamfered portion.

[0084] It is also possible to provide for a general shape of the reinforcement plate 103 that is not rectangular. For example, the reinforcement plate 103 can be of general shape elliptical, square, triangular, trapezoidal.

[0085] In these cases too, the dimensions of the general shape - whatever it may be - are less than 200 mm; the dimensions being measured from a neutral fiber of the chamfered portion.

[0086] The reinforcement plate 103 also includes a chamfer at each of its upper corners. In other words, the upper corners of the reinforcement plate 103 each have a chamfer. These chamfered corners facilitate the welding of the reinforcement gusset 10 and the reinforcement plate 103 to the frame 9.

[0087] Furthermore, a distance d4 between a peripheral end of the heel 102 and the peripheral edge 33 of the cover 25 is between 10 and 75 mm. For example, the distance d4 is 25 mm. Thus, the body of the reinforcing gusset 10 does not reach the peripheral edge 33, which allows the welding operations to be carried out.

[0088] The reinforcing gussets 10 together with the frame 9 contribute to strengthening the rigidity of the lid 25.

[0089] The reinforcing gussets 10 are located in line with the horizontal stiffeners 48. The horizontal stiffeners 48 are aligned with the reinforcing gussets 10 in the same plane, called the alignment plane. This alignment plane is normal to the cover 25.

[0090] Furthermore, the reinforcing gussets 10 are aligned with the vertical stiffeners 49. In other words, each vertical stiffener 49 which is positioned bearing against an external face of the wall 22 of the frame 9 and against the lower face 231 of the seat wall 23 is aligned with a reinforcing gusset 10 in the same plane perpendicular to the cover 25. In other words, the vertical stiffeners 49 are positioned in line with the reinforcing gussets 10.

[0091] With the stiffeners 49 bearing against the lower face of the seat wall 23 and the reinforcing gussets 10 bearing against the upper face of the cover 25, the stiffeners 49 are located under the reinforcing gussets 10.

[0092] For better visibility of the figures, the reinforcing gussets 10 are not shown in [Fig.6] and the stiffeners 49 are not shown in [Fig.4].

[0093] The reinforcement plate 103 improves the reinforcement provided by the reinforcement gusset 10 to the frame 9 and thus improves the rigidity of the cover 25, without increasing the thickness of the body of the gusset 10. Indeed, it increases the moment of inertia of the reinforcement gusset 10 when taking up the bending forces exerted on the cover 25 and the frame 9.

[0094] Furthermore, according to a variant of the invention, the intermediate frame 28 can also present a bevel (as shown in [Fig.9]), similar to bevel 6, at its outer peripheral end 282.

[0095] As a reminder, the intermediate frame 28 is welded, in a sealed manner, to the seat wall 23 by means of two continuous clinker weld lines 29, 30 which extend respectively along the inner peripheral edge of the intermediate frame 28 and along the outer peripheral edge of the intermediate frame 28.

[0096] Thus, the weld 30 located along the peripheral end 282 can then benefit from the same advantages conferred by the bevel 6 to the weld 8 presented above.

[0097] According to one embodiment, the portion of the lower face 281 of the cover 25 which rests against the intermediate frame 28 is pre-machined to ensure the flatness of the contact between the cover 25 and the intermediate frame 28. In such a case, said portion of the cover 25 has a step.

[0098] To create such a recess, operators machine a thicker plate. However, it has been observed that it can be difficult to meet the required flatness and the specified thickness of the recess. Therefore, greater thicknesses are often accepted. Nevertheless, it is sometimes difficult to determine the correct throat size for the weld 8 between the cover 25 and the intermediate frame 28 due to variations in thickness observed on the edge of the cover 25. As explained previously, this weld 8 plays a crucial role in securely attaching the cover 25 to the dome structure. Furthermore, the machining area of ​​the thicker plate is often complex to machine.

[0099] Thus, according to another embodiment, said portion of the cover 25 is not pre-machined and therefore does not have a step.

[0100] Thus, in the absence of a machining step for the cover 25, the following advantages are obtained: - Sheet metal thickness of the cover plate: 25 constant; and - No machining.

[0101] The liquefied gas intended to be stored in the tank may, in particular, be liquefied natural gas (LNG), that is to say, a gaseous mixture consisting mainly of methane and one or more other hydrocarbons. The liquefied gas may also be ethane or liquefied petroleum gas (LPG), that is to say, a mixture of hydrocarbons obtained from petroleum refining consisting essentially of propane and butane.

[0102] With reference to [Fig. 7], a cutaway view of an LNG carrier 70 shows the sealed and insulated tank 2, generally prismatic in shape, mounted in the double hull 72 of the vessel. The wall of the tank 71 comprises a primary watertight barrier intended to be in contact with the LNG contained in the tank, and a secondary watertight barrier arranged between the primary watertight barrier and the double hull 72 of the ship, and two insulating barriers arranged respectively between the primary watertight barrier and the secondary watertight barrier and between the secondary watertight barrier and the double hull 72.

[0103] In a manner known per se, loading / unloading pipelines 73 arranged on the upper deck of the ship can be connected, by means of suitable connectors, to a marine or port terminal to transfer a cargo of LNG from or to tank 2.

[0104] Figure 10 shows an example of a marine terminal comprising a loading and unloading berth 75, a subsea pipeline 76 and an onshore facility 77. The loading and unloading berth 75 is a fixed offshore facility 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 pipelines 73. The steerable movable arm 74 is suitable for all LNG carrier sizes. An unshown connecting pipeline extends inside tower 78. The loading and unloading station 75 allows the loading and unloading of the LNG carrier 70 from or to the onshore facility 77. This facility includes liquefied gas storage tanks and connecting pipelines 81 linked by the subsea pipeline 76 to the loading or unloading station 75.The subsea pipeline 76 allows the transfer of liquefied gas between the loading or unloading station 75 and the onshore facility 77 over a long distance, for example 5 km, which allows the LNG carrier 70 to be kept a long distance from the coast during loading and unloading operations.

[0105] To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps equipping the land installation 77 and / or pumps equipping the loading and unloading station 75 are used.

[0106] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention, as defined by the claims.

[0107] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0108] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. A liquefied gas storage installation comprising a load-bearing structure (1) and a sealed and thermally insulated tank (2) arranged within the load-bearing structure (1), the load-bearing structure (1) comprising an upper load-bearing wall (3) and the tank (2) comprising a ceiling wall attached to the upper load-bearing wall (3), the upper load-bearing wall (3) and the ceiling wall being locally interrupted to define an opening (18), the load-bearing structure (1) comprising a dome structure (19) projecting vertically outward from the tank (2) from the upper load-bearing wall (3) around the opening (18) and defining a passage (24) intended to be traversed by at least one pipe (20, 21, 47) for loading or unloading liquefied gas from the tank (2), the dome structure (19) comprising: - dome walls (22) projecting from the upper load-bearing wall (3) and each comprising an upper end, - a seat wall (23) fixed to the upper ends and extending horizontally, - a cover (25) which covers the passage (24), and has a peripheral edge (33), and - an intermediate frame (28) situated between the seat wall (23) and the peripheral edge (33), the peripheral edge (33) having a first bevel (6) oriented so that the cover (25) narrows from an upper face (331) of the cover (25) to an lower face (332) of the cover (25), the peripheral edge (33) being welded to the intermediate frame (28) by a first weld (8) situated in a space (5) between the first bevel (6) and an upper face (281) of the intermediate frame (28), the intermediate frame (28) being welded to the seat wall (23); the intermediate frame (28) having an external peripheral end (282) which is welded to the seat wall (23) by a second weld.

2. An installation according to claim 2, wherein the intermediate frame (28) has a second bevel (61) oriented such that the intermediate frame (28) narrows from the upper face (281) of the in- frame termedial (28) towards a lower face (283) of the intermediate frame (28), the second weld (30) being located in a space (51) between the second bevel (61) and a higher face of the seat wall (23).

3. Installation according to claim 1, wherein a distance (d6) between the outer peripheral end (282) of an upper face of the intermediate frame (28) and an upper end of the peripheral edge (33) of the cover (25) is between 5 and 40 mm.

4. Installation according to any one of claims 1 to 3, wherein an angle (a) of the first bevel (6) is between 45° and 90°, upper limit not included, the angle being located between the upper face (331) of the cover (25) and a face of the first bevel (6) connecting the upper face (331) of the cover (25) to the lower face (332) of the cover (25).

5. Installation according to any one of claims 1 to 4, wherein the first weld (8) has an actual throat depth of between 5 and 25 mm.

6. Installation according to any one of claims 1 to 5, wherein a distance (dl) between an outer end of the first weld (8) and the outer peripheral end (282) of an upper face (281) of the intermediate frame (28) is between 1 and 20 mm; the distance being measured in a plane of the intermediate frame (28).

7. Installation according to any one of claims 1 to 6, wherein a distance (d5) between an outer end of the lower face (332) of the cover (25) and the outer peripheral end (282) of an upper face of the intermediate frame (28) is between 5 and 25 mm.

8. Installation according to any one of claims 1 to 7, wherein the dome structure (19) comprises a frame (9) formed by frame walls that are welded against the upper face (331) of the cover (25) and reinforcing gussets (10) that are each positioned to bear against an external face of a frame wall and against the upper face (331) of the cover (9).

9. An installation according to claim 8, wherein the reinforcing gussets (10) comprise a body disposed perpendicular to the frame wall, the body having a heel (102) by which said body bears against the upper face (331) of the cover (25) and a chamfered portion (101) extending from the heel (102), the reinforcing gussets (10) further comprising a reinforcing plate (103) po- positioned on the chamfered portion (101) perpendicular to a plane of the body.

10. Installation according to claim 9, wherein a lower end of the reinforcing plate (103) extends to an upper end of the heel (102).

11. Installation according to claim 9 or 10, wherein a distance (d2) between a lower end of the reinforcing plate (103) and the upper face (331) of the cover (25) is between 10 and 100 mm.

12. Installation according to any one of claims 9 to 11, wherein the reinforcing plate (103) is generally rectangular in shape and includes upper corners each having a chamfer.

13. Installation according to any one of claims 9 to 12, wherein a distance (d4) between the heel (102) and an upper end of the peripheral edge (33) of the cover (25) is between 10 and 75mm.

14. Installation according to any one of claims 8 to 13, wherein the dome structure (19) further comprises a plurality of horizontal stiffeners (48) positioned in support against an upper face (331) of the cover (25), each horizontal stiffener being aligned with a reinforcing gusset (10) in the same plane normal to the cover (25).

15. Vessel (70) for the transport of a fluid, the vessel (70) comprising an installation according to any one of claims 1 to 14.

16. Transfer system for a fluid, the system comprising a vessel (70) according to claim 15, insulated pipes (73, 79, 76, 81) arranged to connect the vessel's tank (2) to a floating or land-based storage facility (77) and a pump for conveying a fluid through the insulated pipes (73, 79, 76, 81) from or to the floating or land-based storage facility (77) to or from the vessel's tank (2).

17. A method of loading or unloading a ship (70) according to claim 15, wherein a fluid is conveyed through insulated pipes (73, 79, 76, 81) from or to a floating or land-based storage facility (77) to or from the ship's tank (2).

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