WO2017216477A1

WO2017216477A1 - Gas dome structure for a sealed, thermally insulated vessel

Info

Publication number: WO2017216477A1
Application number: PCT/FR2017/051525
Authority: WO
Inventors: Mohammed OULALITE; Bruno Deletre
Original assignee: Gaztransport Et Technigaz
Priority date: 2016-06-15
Filing date: 2017-06-13
Publication date: 2017-12-21
Also published as: SG11201811056XA; FR3052843A1; CN109416150B; ES2827553T3; KR20190020317A; FR3052843B1; KR102332825B1; EP3472509B1; MY193201A; EP3472509A1; CN109416150A

Abstract

The invention relates to a gas dome structure (1) for a sealed, thermally insulating vessel arranged inside a double shell defined by an inner shell (5) and an outer shell (4), said gas dome structure (1) comprising: - an outer drum (20) that fits through two openings (18, 19), one each in the outer shell (4) and the inner shell (5); - an inner drum (23) that extends inside the outer drum (20), is secured to the outer drum (20) and is to be sealingly connected to the sealing membrane (9); - an insulating gap (24) between the inner drum (23) and the outer drum (20); - the outer drum (20) comprises a first collar (21) and a second collar (22) that radially protrude outwards from the outer drum (20) and can be welded to the outer shell (4) around the opening (18) in the outer shell (4) and to the inner shell (5) around the opening (19) in the inner shell (5), respectively.

Description

GAS DOME STRUCTURE FOR A SEALED TANK AND

THERMALLY INSULATING

Technical area

The invention relates to the field of tanks, sealed and thermally insulating, for the storage and / or transport of fluid, such as a cryogenic fluid.

Sealed and thermally insulating vessels are used in particular for the storage of liquefied natural gas (LNG), which is stored at atmospheric pressure at about -162 ° C.

The invention relates more particularly to a gas dome structure which is intended to define a steam circulation path between the internal space of the vessel and a steam manifold disposed outside the vessel.

Technological background

Document KR20140088975 discloses a sealed and thermally insulating tank which is housed inside a double hull of a ship and comprising a gas dome structure intended to define a steam circulation path between the interior space of the tank and two steam collectors arranged outside the tank.

The gas dome structure has an outer barrel that passes through the outer shell of the double shell and is welded to the inner shell of the double shell, an inner barrel that extends inside the outer barrel and is sealingly connected to the primary sealing membrane of the tank and an insulating intermediate space disposed between the inner and outer barrel. The outer barrel has at its upper end an assembly flange consisting of an outwardly folded flange and receiving a removable cover with the interposition of a seal. The inner barrel and the insulating gap do not extend to the upper end of the inner barrel and two vapor phase gas collection pipes radially pass through the outer barrel into an upper zone of the outer barrel. above the inner shaft and the insulating gap. Such a gas dome structure is not fully satisfactory. Indeed, given its layout, such a gas dome structure is necessarily assembled in-situ on the ship, which complicates and lengthens the assembly maneuvers.

In addition, the seal interposed between the removable cover is directly in contact with the vapor phase in the inner drum. However, when the fluid stored in the tank is a cryogenic fluid, such as liquefied gas, the steam is likely to have low temperatures, up to - 160 ° C. Thus, the seal is likely to be subjected to relatively low temperatures, which is likely to damage it and cause leaks at the gas dome. The reliability of such a gas dome is therefore not fully satisfactory.

summary

An idea underlying the invention is to provide a gas dome structure that is simple to assemble.

According to one embodiment, the invention provides a gas dome structure for a sealed and thermally insulating tank disposed within a double shell defined by an inner shell and an outer shell; said gas dome structure being intended to pass through the double shell and a ceiling wall of the tank including at least one thermally insulating barrier resting against the inner shell and a sealing membrane intended to be in contact with the fluid contained in the tank so as to provide a steam circulation path between an interior space of the vessel and at least one vapor manifold disposed outside the vessel; the gas dome structure comprising:

- An outer barrel adapted to pass through two openings respectively formed in the outer shell and the inner shell;

- an inner shaft which extends inside the outer shaft, is fixed to said outer shaft, is open to communicate with the interior space of the vessel and has a peripheral wall to be connected in a sealed manner to the waterproofing membrane ;

an insulating intermediate space disposed between the inner and the outer barrel;

the outer barrel having a first and a second collar projecting radially outwardly from the outer barrel and which are respectively suitable for being welded to the outer shell, the periphery of the opening in the outer shell, and the inner shell periphery of the opening on the inner shell.

Thus, thanks to the two aforementioned collars, the gas dome structure can be partially or fully pre-assembled in the workshop and the assembly of the gas dome structure on the double shell can be easily achieved.

According to embodiments, such a gas dome structure may include one or more of the following features.

According to one embodiment, the gas dome structure is a pre-assembled structure.

According to one embodiment, the second collar intended to be welded in a sealed manner on the inner shell has a diameter smaller than that of the first collar.

According to one embodiment, the outer barrel and the inner barrel each have an upper end; said upper ends stopping in the same horizontal plane and being connected to each other sealingly by an assembly flange; the gas dome structure further comprising a lid which is secured to said assembly flange by fasteners and an annular seal which is compressed between the lid and the assembly flange. Thus, in such an arrangement, the insulating intermediate space extends to the assembly flange, which further thermally isolates the seal and limits the risk of leakage.

According to one embodiment, the assembly flange comprises an outer portion projecting radially outwardly of the outer barrel; said fasteners passing through orifices in said outer portion of the assembly flange.

According to one embodiment, the lid has an inner face facing the inside of the inner barrel; said inner face being provided with a projection of insulating material engaging in the inner shaft. This also contributes to the thermal insulation of the seal.

According to one embodiment, the gas dome structure further comprises a vapor collection duct capable of driving steam between the inside of the barrel interior and the vapor collector disposed outside the tank; said vapor collection duct radially and sealingly passing through the outer barrel, the insulating interspace and the inner barrel to open into the inner barrel.

According to one embodiment, the gas dome structure comprises an insulating sleeve traversing radially and sealingly the outer barrel, the insulating intermediate space and the inner barrel and the vapor collection duct sealingly crosses said insulating sleeve.

According to one embodiment, the insulating sleeve comprises two concentric cylindrical walls connected to each other in a sealed manner and separated from each other by an annular space; said insulating sleeve having a closable connector which opens into the annular space and which is adapted to be connected to a vacuum pump so as to place the annular space in depression.

According to one embodiment, the steam collection duct has a bent portion disposed inside the inner barrel and has a lower portion directed parallel to the inner barrel towards the interior space of the tank.

According to one embodiment, the gas dome structure further comprises a support device supporting the lower portion of the vapor collection conduit and arranged to distribute the forces exerted on said lower portion on the inner periphery of the inner drum.

According to one embodiment, the support device comprises a first annular plate fixed to the inner barrel and projecting radially inwardly of the inner barrel, a second annular plate fixed to the lower portion of the vapor collection duct and projecting radially. to the outside of said lower portion of the vapor collection duct and a plurality of support arms regularly distributed around the lower portion of the vapor collection duct and each having a first end attached to the first annular plate and a second end attached to the second annular plate.

According to one embodiment, the lower portion of the steam collection duct is equipped with a filter. According to one embodiment, the steam collection duct is connected to a three-way connection disposed outside the outer cask.

According to one embodiment, the inner and outer barrels each have bellows zones allowing their contraction or expansion under the effect of temperature differentials.

According to one embodiment, the insulating intermediate space is filled with a gaseous phase placed under vacuum and / or with an insulating lining. Advantageously, the insulating lining comprises one or more insulating materials chosen from glass wool, rockwool, wadding, fibrous materials, perlite, expanded perlite, polymeric foams and aerogels.

According to one embodiment, the insulating intermediate space has a lower end sealingly closed by an annular flange.

According to one embodiment, the invention also provides a fluid storage device comprising a double shell defined by an inner shell and an outer shell and a sealed and thermally insulating tank disposed in the double shell; the tank comprising:

a thermally insulating barrier resting against the inner shell;

a sealing membrane intended to be in contact with the fluid contained in the tank; and

a aforementioned gas dome structure which passes through the outer shell, the inner shell, the thermally insulating barrier and the sealing membrane so as to provide a steam circulation path between an interior space of the tank; and a vapor collector disposed outside the vessel; the first flange of the gas dome structure being welded to the outer shell at the periphery of an opening in the outer shell, the second flange of the gas dome structure being welded to the inner shell at the periphery of an opening in the inner shell and the inner drum being sealingly connected to the sealing membrane.

According to embodiments, such a fluid storage device may include one or more of the following features.

According to one embodiment, the opening formed in the inner shell has a smaller diameter than the opening formed in the outer shell and the second flange has a diameter smaller than that of the opening in the outer shell and greater than that of the opening in the inner shell. Such an arrangement makes it possible to easily pass the gas dome structure through the double shell and to ensure easy installation of the gas dome structure.

According to one embodiment, the thermally insulating barrier is a secondary thermally insulating barrier and the waterproofing membrane is a primary waterproofing membrane, the tank further comprising a secondary sealing membrane resting against the secondary thermally insulating barrier and a primary thermally insulating barrier disposed between the secondary waterproofing membrane and the primary waterproofing membrane.

According to one embodiment, the outer barrel comprises a third flange projecting radially outwardly from the outer barrel and sealingly connected to the secondary sealing membrane.

According to one embodiment, the gas dome structure further comprises an additional barrel which extends radially outside the outer barrel and which has an upper end welded to the first flange and a lower end welded to the second flange and an insulating gasket disposed between the additional shaft and the outer shaft.

According to one embodiment, the insulating intermediate space disposed between the inner and the outer barrel is divided into a primary compartment and a secondary compartment, sealed with respect to each other.

According to one embodiment, the primary compartment and the secondary compartment are separated by a sealed annular partition fixed on the one hand to the outer shaft and on the other hand to the inner shaft.

According to one embodiment, the primary compartment is equipped with one or more orifices provided in the outer casing and intended to put the primary compartment in communication with a primary thermally insulating barrier.

Such a fluid storage device can be part of an onshore storage facility, for example to store LNG or be installed in a floating structure, coastal or deepwater, including a tanker or LNG tanker, a floating storage unit and regasification (FSRU), a unit floating production and remote storage (FPSO) and others. In the case of a floating structure, the tank may be intended to receive liquefied natural gas as a fuel for the propulsion of the floating structure.

According to one embodiment, the fluid storage device is configured in the form of a ship.

According to one embodiment, the invention also provides a method of loading or unloading such a storage device, in which a fluid is conveyed through isolated pipes from or to a floating or land storage facility to or from the tank of the storage device.

According to one embodiment, the invention also provides a transfer system for a fluid, the system comprising the aforementioned storage device, insulated pipes arranged to connect the tank to a floating or land storage installation and a pump for driving a flow of fluid through the isolated pipes from or to the floating or land storage facility to or from the tank.

Another idea underlying the invention is to provide a gas dome structure that is particularly reliable, especially in that it allows to limit steam leakage.

To do this, according to one embodiment, the invention provides a gas dome structure for a sealed and thermally insulating tank disposed within a double shell defined by an inner shell and an outer shell; said gas dome structure being intended to pass through the double shell and a ceiling wall of the tank including at least one thermally insulating barrier resting against the inner shell and a sealing membrane intended to be in contact with the fluid contained in the tank so as to provide a steam circulation path between an interior space of the vessel and at least one vapor manifold disposed outside the vessel; the gas dome structure comprising:

- an inner shaft which extends inside the outer shaft, is fixed to said inner shaft and is adapted to be sealingly connected to the sealing membrane;

an insulating intermediate space disposed between the inner and the outer barrel; The outer end and the inner end each have an upper end a vapor collection duct radially and sealingly passing through the outer barrel, the insulating interspace and the inner barrel to open into the inner barrel;

said upper ends stopping in the same horizontal plane, and being sealed to each other by an assembly flange; the insulating intermediate space extending to the upper ends of the inner and outer barrels; the gas dome structure further comprising a lid which is secured to said assembly flange by fasteners and an annular seal which is compressed between the lid and the assembly flange.

Thus, thanks to such an arrangement, the insulating intermediate space extends to the assembly flange, which further thermally isolates the seal and limits the risk of leakage.

Brief description of the figures

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

- Figure 1 is a perspective view of a gas dome structure passing through the double hull of a ship and a ceiling wall of a sealed and thermally insulating tank resting against the inner shell of the double shell.

- Figure 2 is a sectional view of the gas dome structure of Figure 1.

- Figure 3 is a sectional view illustrating in detail the area in which the vapor phase gas collection line passes through the outer shaft, the inner shaft and the insulating gap.

- Figure 4 is a perspective sectional view illustrating the gas dome structure of Figure 1 during its passage through the openings in the inner shell and the outer shell.

FIG. 5 is a perspective sectional view illustrating in detail the filter equipping the vapor phase gas collection pipe as well as the device for supporting said gas vapor collection line on the inner shaft of the gas dome structure.

- Figure 6 is a schematic cutaway representation of a tank of LNG tanker and a loading / unloading terminal of this tank.

- Figure 7 is a partial cutaway perspective view of a sealed and thermally insulating tank wall.

- Figure 8 is a partial sectional view of a gas dome structure according to a second embodiment.

- Figure 9 is a partial sectional view of a gas dome structure according to a third embodiment.

Detailed description of embodiments

In relation to FIG. 1, a gas dome structure 1 is observed for a sealed and thermally insulating tank for storing a liquefied gas, such as Liquefied Natural Gas (LNG) or Liquefied Petroleum Gas (LPG). . The gas dome structure 1 defines a steam circulation path between the interior space 2 of the vessel and one or more steam manifolds 3, 48 located outside the vessel.

The tank is disposed inside the double hull of a vessel comprising an outer shell 4 and an inner shell 5. The inner shell 5 constitutes the carrying structure of the vessel. The tank has a general polyhedral shape.

In relation to FIG. 7, the multilayer structure of a wall of a sealed and thermally insulating tank according to one embodiment is described. Each wall of the tank comprises, in the thickness direction of the tank, from the outside to the inside, a secondary heat-insulating barrier 6 resting against the inner shell 5, a secondary membrane 7 sealed, a primary heat-insulating barrier 8 and a sealed primary membrane 9 intended to be in contact with the fluid stored in the tank.

The primary heat-insulating barrier 8 and the secondary heat-insulating barrier 6 each consist of heat-insulating element and more particularly of parallelepiped heat-insulated casings which are juxtaposed in a regular pattern. Each insulating box 10 has a bottom panel 11 and a cover panel 12. Side panels 13 and internal sails 14 extend between the bottom panel 11 and the cover panel 12 in the thickness direction of the vessel wall. The panels, bottom 11 and cover 12, and the internal webs 14 define spaces in which is placed a heat insulating pad, for example expanded perlite. Each heat insulating box 10 is held on the inner shell 5 by means of anchoring members. The heat-insulated casings 10 of the primary thermally insulating barrier 8 and of the secondary thermally insulating barrier 6 carry respectively the primary membrane 9 and the secondary membrane 7.

The membranes, secondary 7 and primary 9, each consist of a series of parallel Invar® strakes 15 with folded edges, which are alternately arranged with elongated welding supports 16, also in Invar®. The strakes 15 comprise, in the width direction, a flat central strip resting against the cover panels 12 of the heat insulating boxes 10 and folded lateral edges. The folded edges extend substantially perpendicular to the flat central band. The folded edges of the crimped strands are welded at each end to the heat-insulating barrier 6, 8 underlying, e.g. being housed in inverted T-shaped grooves formed in the cover panels 12 of the heat insulating boxes 10.

At an angle between two walls, the membranes, secondary 7 and primary 9, of the two walls are connected by a connecting ring 17 in the form of a square section tube. The connecting ring 17 forms a structure which makes it possible to take up the tension forces resulting from the thermal contraction of the secondary and primary membranes 9, the deformation of the shell and the movements of the cargo.

Referring to FIGS. 2 and 4, a gas dome structure 1 will now be described which passes through two openings 18, 19 formed respectively in the outer shell 4 and in the inner shell 5. The gas dome structure 1 comprises an outer barrel 20, of cylindrical shape, which passes through the opening 18 of the outer shell 4 and the opening 19 of the inner shell 5. The outer barrel 20 is open at each of its two ends. The outer barrel 20 is equipped with two flanges 21, 22 which are respectively able to ensure the attachment of the gas dome structure 1 on the outer shell 4 and the inner shell 5. The flanges 21, 22 are welded to the outer barrel 20 and protrude radially outwardly relative to the axis of the outer shaft 20. As shown in Figure 4, the collar 22, intended to be fixed on the inner shell 5 has an outer diameter smaller than that of the opening 18 in the the outer shell 4 so as to allow its passage through the opening 18 of the outer shell 4 during the installation of the gas dome structure 1. The outer diameter of the collar 22 is however greater than that of the opening 19 formed in the inner shell 5. Thus, the flange 22 may be sealingly welded to the inner shell 5 at the periphery of the opening 19. The other flange 21 is intended to be welded in a sealed manner on the outer shell 4, at the periphery of the opening 18 formed in the outer shell 4, and to this end has an outer diameter which is greater than that of the opening 18.

The gas dome structure 1 further comprises an inner shaft 23 fixed to the outer shaft 20. The inner shaft 23 is formed of a cylindrical peripheral wall open at both ends thereof. The inner shaft 23 is concentric with the outer shaft 20 and extends inside thereof. An insulating intermediate space 24 is thus formed between the outer barrel 20 and the inner barrel 23. The inner barrel 23 extends to the upper end of the outer barrel 20 and the upper ends of the outer barrels 23 and inner 20 are connected. to one another in a sealed manner by a substantially horizontal assembly flange 25. The assembly flange 25 has an inner portion which connects the ends of the outer and inner barrels 20 and an outer portion which projects radially outwardly of the outer barrel 20.

As represented in particular in FIGS. 2 and 4, the outer barrel 20 and the inner barrel 23 are each equipped with at least one bellows zone 31, 32 allowing their expansion or contraction depending on whether liquefied gas vapor resides or not. in the gas dome structure 1.

In one embodiment, for practical questions of positioning the flanges 21 and 22 relative to the shells 4 and 5 and / or catching the relative positioning tolerances of the shells 4, 5, one and / or the other of flanges 21 and 22, and in particular the flange 21, may be welded on wedges in the form of half-moon previously welded to the shell 4, 5 respectively periphery of the opening 18, 19. The thickness of the spacers is then dimensioned so as to ensure contact between the flange 21, 22 and the respective shims, on the one hand, and between the shims and the shell 4, 5, on the other hand. Alternatively, the bellows zones 31, 32 each have an excess length allowing compression of the dome structure, and in particular the inner and outer barrels 23 during its installation, this compression effect being reduced or even eliminated during the thermal contraction generated by the cooling of the tank 2. To do this, a compression tool can be used to press the collar 21 against the shell 4 and compress the bellows zones 31, 32 during the welding of the collar 21 on the hull 4.

The gas dome structure 1 is furthermore equipped with a removable cover 26 so as to allow access to the inside of the tank via the gas dome structure 1, in particular for tank maintenance and inspection operations. The cover 26 has on its upper face a fastening member 27 for handling by means of a handling tool. The lid 26 rests against the assembly flange 25 and is fixed thereto by means of a plurality of fasteners 28, in particular represented in FIGS. 1 and 4, which each pass through a orifice formed at the periphery of the lid and an orifice formed in the outer portion of the assembly flange 25. The fasteners 28 are for example constituted by a bolt having a threaded rod and a nut cooperating with said threaded rod.

A seal, not shown, is compressed between the cover 26 and the assembly flange 25 and thus provides a seal between the outside and the inside of the inner barrel 23. The seal is example positioned on a diameter smaller than the implantation diameter of the fasteners, that is to say between the inner portion of the assembly flange 25 and the cover 26. According to alternative embodiments not shown, the ) seal (s) is placed in a recess formed in the cover 26 or in the assembly flange 25. The seal may be flat or O-ring.

The seal is made of polymer, such as polytetrafluoroethylene (PTFE), butadiene acrylonitrile (NBR) reinforced with glass fibers and / or aramid, and / or carbon, for example Klingersil ® brand. Thanks to the arrangement described above and in particular that the insulating intermediate space 24 extends to the assembly flange 25, the thermal insulation of the seal is satisfactorily provided, which allows the limit the risk of degradation of said seal and the risk of leakage. Moreover, as shown in FIGS. 2 and 4, the lid 26 has, on its inner face turned towards the inside of the inner barrel 23, a protrusion 33 of insulating material engaging in the inner barrel 23. The projection 33 in Insulating material has a diameter slightly less than that of the inner shaft 23. Such an arrangement also contributes to the thermal insulation of the seal. The projection 33 of insulating material is in particular made of rigid or flexible insulating foam for example polyurethane foam or melamine.

In the lower part, the inner shaft 23 and the outer shaft 20 are also connected to each other in a sealed manner so that the insulating intermediate space 24 formed between the inner shaft 23 and the outer shaft 23 is sealed. To do this, an annular flange 29 is sealingly welded between the lower edges of the outer shaft 20 and the inner shaft 23.

The outer barrel 20 and the inner barrel 23 pass through the ceiling wall of the tank, that is to say the thermally insulating, secondary 6 and primary 8 barriers, as well as the membranes, secondary 7 and primary 9, to lead to the inside of the tank. As schematically shown in Figure 2, the inner shaft 23 and the outer shaft 20 extend to the primary membrane 9 of the ceiling wall of the vessel. The primary membrane 9 is sealingly connected to said annular flange 29 so as to ensure continuity of the sealing of the primary membrane 9. Moreover, the secondary membrane 7 is sealingly welded to the outer drum 20 so as to ensure a continuity of the sealing of the secondary membrane 7, between the thermally insulating barriers, primary 8 and secondary 6. To do this, according to one embodiment, the outer shaft 20 is equipped with a third annular flange 30, schematized in FIG. 2, which protrudes radially outwards from the outer barrel 20 and which thus constitutes a support adapted to ensure the welding of the secondary membrane 7 on the outer barrel 20. In a mode not shown, the inner barrel 23 and the outer barrel 20 extend beyond the primary membrane 9 of the ceiling wall of the tank and the primary membrane 9 is sealed on a glue additional annular head, not shown, projecting radially outwardly of the outer shaft 23.

In the embodiment shown, the insulating intermediate space 24 is filled with an insulating lining 34 which is distributed uniformly over the inner bearing surface of the outer shank 20, between said outer shank 20 and the inner shank 23. insulating liner 34 comprises one or more insulating materials selected from glass wool, rockwool, wadding, fibrous materials, perlite, expanded perlite, polymeric foams and aerogels. In the embodiment shown, the insulating lining 34 has, in an area corresponding to the zone of bellows 32 of the inner barrel 23, a recess 46 allowing the housing of said zone of bellows 32 to be accommodated.

In another embodiment, the insulating intermediate space 24 is placed in depression. In such an embodiment, the gas dome structure 1 is equipped with a closable connection which, on the one hand, passes through the inner barrel 23 or outer barrel 20 to open into the insulating intermediate space 24 and which, on the other hand, is adapted to be connected to a vacuum pump for extracting the gas present in the insulating space 24 in order to place it in a vacuum. In another embodiment, the two embodiments described above are combined so that the insulating space 24 is both filled with an insulating lining 34 and put under vacuum.

The gas dome structure 1 further comprises at least one vapor collection duct 35 which passes radially and in a sealed manner between the outer barrel 20, the inner barrel 23 and the insulating intermediate space 24 in order to conduct steam between the inner barrel 23 and the steam collectors 3, 48 located outside the tank. The vapor collection duct 35 therefore does not pass through the lid 26, which simplifies the removal and placement of the lid 26 when an operator must access the inside of the tank.

More particularly, the vapor collection duct 35 passes sealingly through an insulating sleeve 37, shown in detail in FIG. 3, which itself passes radially through the outer barrel 20, the inner barrel 23 and the insulating intermediate space 24. The insulating sleeve 37 comprises two concentric cylindrical walls sealingly connected to one another and separated from each other by an annular space placed in depression. To do this, the insulating sleeve 37 comprises a closable connection 38 opening inside the annular space and intended to be connected to a vacuum pump so as to place the annular space in depression.

If in the preferred embodiment shown, a single vapor collection conduit 35 passes radially and tightly through the drums. outside 23 and inside 20, the gas dome structure may also include a plurality of vapor collection conduits 35 passing radially and sealingly outer and inner barrels 23 and 20.

In FIGS. 2 and 4, it can be seen that the steam collection duct 35 has a bent portion such that the said vapor collection duct 35 has a lower portion 36 which is directed parallel to the shafts of the barrels, inside 23 and outside 20, towards the interior space of the tank. The bent portion and the lower portion 36 are removably attached to the remainder of the vapor collection conduit 35, for example by means of bolted joint flanges. The bent portion and the lower portion 36 are thus removable in order to allow the passage of a man or material by this gas dome structure 1.

The gas dome structure 1 is furthermore equipped with a support device 39, in particular represented in FIGS. 2, 4 and 5, which supports the lower portion 36 of the vapor collection duct 35 and which is arranged to distribute the forces acting on said lower portion 36 on the inner periphery of the inner barrel 23. To do this, the support device 39 has a first annular plate 40 fixed to the inner barrel 23 and projecting radially inwards from the inner barrel 23, a second annular plate 41 fixed to the lower portion 36 of the vapor collection duct 35 protruding radially outwardly of the vapor collection duct 35 and a plurality of arms 42 regularly distributed around the lower portion 36 of the collection duct steamers 35 which are each fixed between the first annular plate 40 and the second annular plate 41, for example bolted. Furthermore, as shown in FIGS. 2 and 5, the first annular plate 40 is advantageously supported by support brackets 43 made of sheet metal which are welded on the one hand against the inner shaft 23 and on the other hand against the lower face of the first annular plate 40.

In an alternative embodiment shown in FIG. 2, the gas dome structure 1 comprises anchoring lugs 49 which are arranged in the insulating intermediate space 24 and welded between the inner and outer shanks 23 in the zones of fixing of the support brackets 43. Such anchoring tabs 49 are intended to partly take up the support forces of the steam collection conduit 35 on the outer drum 20, in particular when the inner drum 20 has a thickness that does not provide it with sufficient strength. sufficient mechanical strength. Furthermore, the lower portion 36 of the vapor collection duct 35 is equipped with a filter 44 producing a pressure drop and thus making it possible to prevent the gas in the liquid phase from rising back into the vapor collector 3 and exit the tank.

The gas dome structure 1 further comprises at least one liquefied gas supply duct 45, in particular represented in FIGS. 2 and 4, which passes through the outer casing 20, the insulating intermediate space 24 and the inside casing 23. above the outer shell 4, and down along the inner shaft 23 so as to open into the interior space of the tank. In the interior of the vessel, the conduit 45 has a plurality of injection nozzles for spraying liquefied gas to cool the vapor phase of the gas stored in the vessel and thus limit the increase in vapor pressure in the vessel. interior space of the tank.

As shown in FIG. 1, the steam collection duct 35 is connected, outside the gas dome structure 1, to a three-way connection 47 leading to two separate steam collectors 3, 48. One of the steam collectors 48 is equipped with a safety valve, not shown. The safety valve is tared so as to ensure evacuation of the gas vapor phase of the tank when the vapor pressure in the tank is greater than a threshold pressure of between 0 and 2 bar, for example between 0.2 and 0.4 bar. Given the pressure losses due in particular to the bent zone and the filter 44, the calibration of the safety valve is slightly lower than the threshold pressure beyond which the vapor pressure in the tank must not go. This vapor collector 48 makes it possible to extract steam from the tank in the event of overpressure and aims to control the pressure inside the tank so as to avoid overpressures that could damage the tank.

This vapor collector 48 for example conducts the steam to a degassing mast, to a burner, to a vessel propulsion device or to a liquefaction device in which the vapor phase gas is reliquefied and then reintroduced into the liquid phase tank. . The other vapor collector 3 is intended to allow the circulation of steam during the loading and unloading operations of the tank. Indeed, during loading operations, when liquefied gas is transferred from a supply terminal to a tank, gas in the gas phase is simultaneously transferred from the tank to the terminal, through the gas dome structure 1 and the steam manifold 3, in order to maintain substantially constant the pressure prevailing in the gaseous sky of the tank. Conversely, during the unloading operations during which liquefied gas is transferred from the tank to a terminal, gas in the gas phase is simultaneously transferred from the terminal to the tank to prevent a pressure decrease in the tank.

The outer barrel 20, the inner barrel 23, the flanges 21, 22, the support device 39 and the vapor collection duct 35 are made of a metallic material, such as stainless steel, an iron-based alloy. containing nickel or manganese for example.

In relation to FIG. 8, a gas dome structure 1 according to a second embodiment is observed. This gas dome structure 1 differs from the gas dome structure described above in that it further comprises an additional insulating barrier 50, between the two flanges 21, 22. To do this, the gas dome structure 1 comprises a barrel additional 51 which extends radially outside the outer shaft 20, all around it. The additional barrel 51 has a lower end which is welded to the flange 22 and an upper end which is welded to the flange 21. The additional barrel 51 has a smaller diameter than the flanges 21, 22. More particularly, the diameter of the barrel additional 51 is dimensioned so that each of the flanges 21, 22 has, at its outer periphery, an annular surface for welding on one of the shells, which has a sufficient size to obtain a satisfactory welding.

In the embodiment shown, the additional barrel 51 is equipped with a bellows zone 52 allowing expansion or contraction of the additional barrel 51. Furthermore, the space between the outer barrel 20 and the additional barrel 51 is filled an insulating liner 53 which comprises one or more insulating materials selected from glass wool, rockwool, wadding, fibrous materials, perlite, expanded perlite, polymeric foams and aerogels. The additional drum 51 and the insulating lining 53 are pre-assembled to the gas dome structure 1 in the workshop before it is assembled on the double hull of the ship. Such an arrangement makes it possible to increase the thermal insulation capabilities of the structure of the gas dome 1, especially in the space between the two shells 4, 5. In addition, the additional shaft 51 is sealed to the flanges 21 , 22 so that said additional barrel 51 forms a watertight barrier additional protection against invasion by natural gas from the area between the two hulls 4, 5.

In relation to FIG. 9, a gas dome structure 1 according to a third embodiment is observed. This embodiment differs from the embodiment of FIG. 8 described above in that the insulating intermediate space 24 disposed between the inner barrel 23 and the outer barrel 20 is divided into two compartments, primary 24a and secondary 24b, sealed. relative to each other. Such an arrangement provides an additional level of sealing in the gas dome structure. To do this, the gas dome structure 1 comprises an annular partition 54, for example of metal, having an inner periphery which is sealingly welded to the inner barrel 23 and an outer periphery which is sealingly welded to a portion of the barrel outside 20 located between the level of the shell 5 and the secondary sealing membrane 7. In the embodiment shown, the annular partition 54 extends at the level of the secondary sealing membrane 7. The secondary compartment 24b is filled with an insulating liner which includes one or more insulating materials selected from glasswool, rockwool, wadding, fibrous materials, perlite, expanded perlite, polymeric foams and aerogels and / or is able to be connected to a vacuum pump so as to be placed in depression. The primary compartment 24a is also filled with an insulating lining comprising one or more of the abovementioned insulating materials.

In addition, in the embodiment shown, the outer barrel 20 has one or more orifices 55 for communicating the primary compartment 24a and the primary thermally insulating barrier 8. Thus, the primary compartment 24a is able to be swept by an inert gas simultaneously with the primary thermally insulating barrier 8 and be connected to a detection device which analyzes the gas present in the primary thermally insulating barrier so as to detect the presence of any leakage of the primary and / or secondary membranes.

The technique described above for producing a gas dome structure can be used in various types of membrane tanks, in a land installation or in a floating structure such as a LNG tank or other.

Referring to Figure 6, a cutaway view of a LNG tanker 70 shows a sealed and insulated tank 71 of general prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary membrane intended to be in contact with the LNG contained in the tank, a secondary membrane arranged between the primary membrane and the double hull 72 of the ship, and two thermally insulating barriers arranged respectively between the primary membrane. and the secondary membrane and between the secondary membrane and the double shell 72.

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

FIG. 6 represents an example of a marine 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 an arm mobile 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 that can connect to the loading / unloading pipes 73. The movable arm 74 can be adapted to all gauges of LNG carriers . A connection pipe (not shown) extends inside the tower 78. The loading and unloading station 75 enables the loading and unloading of the LNG tank 70 from or to the shore facility 77. liquefied gas storage tanks 80 and connecting lines 81 connected by the underwater line 76 to the loading or unloading station 75. The underwater line 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the onshore installation 77 over a large distance, for example 5 km, which makes it possible to keep the tanker vessel 70 at great distance from the coast during the loading and unloading operations.

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

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it is comprises all the technical equivalents of the means described and their combinations if they fall 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 steps other than those set out in a claim.

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

Claims

1. Gas dome structure (1) for a waterproof and thermally insulating tank arranged inside a double shell defined by an internal shell (5) and an external shell (4); said gas dome structure (1) being intended to pass through the double shell and a ceiling wall of the tank comprising at least one thermally insulating barrier (6) resting against the internal shell (5) and a sealing membrane (9) intended to be in contact with the fluid contained in the tank, so as to provide a steam circulation path between an interior space of the tank and at least one steam collector (3, 48) arranged outside the tank ; the gas dome structure (1) comprising:

- an outer barrel (20) capable of passing through two openings (18, 19) respectively provided in the outer shell (4) and in the inner shell (5);

- an inner barrel (23) which extends inside the outer barrel (20), is fixed to said outer barrel (20), is open so as to communicate with the interior space of the tank and has a peripheral wall intended to be connected in a watertight manner to the sealing membrane (9);

- an insulating intermediate space (24) arranged between the inner barrel (23) and the outer barrel (20);

- the outer barrel (20) comprising a first and a second collar (21, 22) which project radially towards the outside of the outer barrel (20) and which are respectively capable of being welded to the outer shell (4), in periphery of the opening (18) made in the outer shell (4), and on the inner shell (5) at the periphery of the opening (19) made on the inner shell (5).

2. Gas dome structure (1) according to claim 1, in which the second flange (22) intended to be welded in a sealed manner to the internal shell (5) has a diameter smaller than that of the first flange (21).

3. Gas dome structure (1) according to claim 1 or 2, in which the outer barrel (20) and the inner barrel (23) each have an upper end; said upper ends stopping in the same horizontal plane and being connected to each other in a watertight manner by an assembly flange (25); the gas dome structure (1) further comprising a cover (26) which is fixed to said assembly flange (25) by fixing members (28) and an annular seal which is compressed between the cover (26) and the assembly flange (25).

4. Gas dome structure (1) according to claim 3, in which the assembly flange (25) comprises an external portion projecting radially outside the outer barrel (20); said fixing members (28) passing through orifices provided in said external portion of the assembly flange (25).

5. Gas dome structure (1) according to claim 3 or 4, in which the cover (26) has an internal face facing the interior of the internal barrel (23); said internal face being provided with a projection (33) of insulating material engaging in the internal barrel (23).

6. Gas dome structure (1) according to any one of claims 1 to 5, further comprising a steam collection conduit (35) capable of conducting steam between the interior of the inner barrel (23) and the steam collector (3, 47); said steam collection conduit (35) passing radially and in a sealed manner through the outer barrel (20), the insulating intermediate space (24) and the inner barrel (23) to open inside the inner barrel (23).

7. Gas dome structure (1) according to claim 6, comprising an insulating sleeve (37) passing radially and in a sealed manner through the outer barrel (20), the insulating intermediate space (24) and the inner barrel (23) and wherein the steam collection conduit (35) passes through said insulating sleeve (37) in a sealed manner.

8. Gas dome structure (1) according to claim 7, in which the insulating sleeve (37) comprises two concentric cylindrical walls connected to each other in a sealed manner and separated from each other by a space annular; said insulating sleeve (37) comprising a closable connection (38) which opens into the interior of the annular space and which is capable of being connected to a vacuum pump so as to place the annular space in depression.

9. Gas dome structure (1) according to any one of claims 6 to 8, in which the steam collection conduit (35) has a bent portion disposed inside the inner barrel (23) and comprises a portion lower (36) directed parallel to the inner barrel (23) towards the interior space of the tank.

10. Gas dome structure (1) according to claim 9, further comprising a support device (39) supporting the lower portion (36) of the steam collection conduit (35) and arranged to distribute the forces exerted on said lower portion (36) on the inner periphery of the inner barrel (23).

11. Gas dome structure (1) according to claim 10, in which the support device (39) comprises a first annular plate (40) fixed to the inner barrel (23) and projecting radially towards the inside of the inner barrel ( 23), a second annular plate (41) fixed to the lower portion of the steam collection conduit (35) and projecting radially outwards from said lower portion (36) of the steam collection conduit (35) and a plurality of support arms (42) regularly distributed around the lower portion (36) of the steam collection conduit (35) and each comprising a first end fixed to the first annular plate (40) and a second end fixed to the second annular plate (41).

12. Gas dome structure (1) according to any one of claims 9 to 11, wherein the lower portion (36) of the steam collection conduit (35) is equipped with a filter (44).

13. Gas dome structure according to any one of claims 4 to 9, in which the steam collection conduit (38) is connected to a three-way connection (47) disposed outside the outer barrel (23).

14. Gas dome structure (1) according to any one of claims 1 to 13, in which the inner barrel (23) and the outer barrel (20) each comprise bellows zones (31, 32).

15. Gas dome structure (1) according to any one of claims 1 to 14, in which the insulating intermediate space (24) is filled with a gas phase placed in depression and/or with an insulating lining (34). ).

16. Gas dome structure (1) according to any one of claims 1 to 15, in which the insulating intermediate space (24) has a lower end closed in a sealed manner by an annular flange (29).

17. Gas dome structure (1) according to any one of claims 1 to 16, further comprising an additional barrel (51) which extends radially outside the outer barrel (20) and which has an end upper welded to the first flange (21) and a lower end welded to the second flange (22) and an insulating gasket (53) placed between the additional barrel (51) and the outer barrel (20).

18. Gas dome structure (1) according to any one of claims 1 to 17, in which the insulating intermediate space (24) disposed between the inner barrel (23) and the outer barrel (20) is divided into a compartment primary (24a) and a secondary compartment (24b) sealed relative to each other.

19. Gas dome structure according to claim 18, in which the primary compartment is equipped with one or more orifices formed in the external barrel and intended to put the primary compartment in communication with a primary thermally insulating barrier.

20. Fluid storage device comprising a double shell defined by an internal shell (4) and an external shell (5) and a sealed and thermally insulating tank arranged in the double shell; the tank comprising:

- a thermally insulating barrier (6) resting against the internal shell (5);

- a sealing membrane (9) intended to be in contact with the fluid contained in the tank; And

- a gas dome structure (1) according to any one of claims 1 to 19 which passes through the outer shell (4), the inner shell (5), the thermally insulating barrier (6) and the sealing membrane (9) so as to provide a steam circulation path between an interior space of the tank and at least one steam collector (3) arranged outside the tank; the first flange (21) of the gas dome structure (1) being welded to the outer shell (4) at the periphery of an opening (18) formed in the outer shell (4), the second flange (22) of the gas dome structure (1) being welded to the internal shell (5) at the periphery of an opening (19) provided in the internal shell (5) and the internal barrel (23) being connected in a sealed manner to the membrane of sealing (9).

21. Fluid storage device according to claim 20, in which the opening (18) formed in the internal shell (4) has a diameter less than that of the opening (19) formed in the external shell (5) and in which the second flange (22) has a diameter less than that of the opening (19) made in the outer shell (5) and greater than that of the opening (18) made in the inner shell (4).

22. Fluid storage device according to claim 20 or 21, in which the thermally insulating barrier is a secondary thermally insulating barrier (6) and the sealing membrane is a primary sealing membrane (9), the tank comprising in in addition to a secondary sealing membrane (7) resting against the secondary thermally insulating barrier (6) and a primary thermally insulating barrier (9) disposed between the secondary sealing membrane (7) and the primary sealing membrane (9) ; the outer barrel comprising a third flange (30) projecting radially outwards from the outer barrel (20) and connected in a sealed manner to the secondary sealing membrane (7).

23. Fluid storage device according to any one of claims 20 to 22 configured in the form of a vessel.

24. Method of loading or unloading a fluid storage device according to any one of claims 20 to 23, in which a fluid is conveyed through insulated pipes (73, 79, 76, 81) from or to a floating or terrestrial storage installation (77) to or from the tank of the storage device.

25. Transfer system for a fluid, the system comprising a fluid storage device according to any one of claims 20 to 23, insulated pipes (73, 79, 76, 81) arranged so as to connect the tank (71 ) to a floating or land-based storage facility (77) and a pump for driving fluid through the insulated pipes to or from the floating or land-based storage facility to or from the tank.