FR3112588A1 - Wall of a liquefied gas storage tank - Google Patents

Abstract

The invention relates to a wall (1) of a storage tank for a liquefied gas comprising a secondary thermally insulating barrier (2) comprising secondary panels (3) which are anchored to a supporting structure (4), a membrane of secondary sealing (5) carried by the secondary thermally insulating barrier (2), a primary thermally insulating barrier (6) comprising primary panels (7) which have the shape of a rectangular parallelepiped and are anchored to the secondary thermally insulating barrier (2 ) by primary anchoring devices (29) and a primary sealing membrane (8) carried by the primary thermally insulating barrier (6) and intended to be in contact with the liquefied gas contained in the tank; wherein at least one of the primary panels (7) is anchored to the secondary thermal insulation barrier by means of four primary anchors (29) which are each positioned at a corner (30, 31, 32, 33 ) of said primary panel (7), said primary panel (7) comprising a centering orifice (42) which is formed in a central portion of said primary panel (7) and in which is fitted a primary centering device (41) fixed to one of the secondary panels (3). Figure for the abstract: Fig. 2

Description

Wall of a liquefied gas storage tank

The invention relates to the field of sealed and thermally insulating tanks for the storage and/or transport of a liquefied gas, such as tanks for the transport of Liquefied Petroleum Gas (also called LPG) having for example a temperature between between -50°C and 0°C, or for transporting Liquefied Natural Gas (LNG) at approximately -162°C at atmospheric pressure.

These tanks can be installed on land or on a floating structure. In the case of a floating structure, the tank may be intended for the transport of liquefied gas or to receive liquefied gas used as fuel for the propulsion of the floating structure.

Technology background

The document KR20190065864 discloses a sealed and thermally insulating liquefied natural gas storage tank arranged in a supporting structure and whose walls have a multilayer structure, namely from the outside towards the inside of the tank, a secondary thermally insulating barrier which comprises secondary panels which are anchored against the supporting structure, a secondary waterproofing membrane which is supported by the secondary thermally insulating barrier, a primary thermally insulating barrier which comprises primary panels which are anchored on the secondary thermally insulating barrier and a membrane primary sealing which is supported by the primary thermally insulating barrier and which is intended to be in contact with the liquefied natural gas stored in the tank.

The primary panels are fixed to the secondary panels by primary anchoring devices which each cooperate with four support zones belonging respectively to the corners of four adjacent primary panels. Such an arrangement of the primary anchoring devices is advantageous in that it holds the corners of the primary panels and thus makes it possible to prevent the primary panels from bending due to stresses caused by phenomena of differential expansion of the various components of the panels. primary when subjected to a thermal gradient. Furthermore, by using the same primary anchoring device to cooperate with the corners of four adjacent primary panels, the number of primary anchoring devices and, consequently, the number of watertight crossings of the secondary sealing are limited.

However, it has been found that such an arrangement does not ensure precise positioning of the primary panels relative to the secondary panels. In fact, when the primary panels are anchored at their corner, there is necessarily a clearance in the positioning of the primary panels with respect to the primary anchoring devices, making it possible in particular to take into account the manufacturing tolerances of the primary panels as well as the tolerances of relative positioning of the secondary panels and therefore of the primary anchoring devices.

However, this has the effect of creating disparities in the behavior of the primary membrane, in particular when it is subjected to the phenomena of thermal contraction and elongation of the hull of the ship when the tank is placed in the hull of a ship. . This also leads to stressing the undulations of the primary membrane in a heterogeneous manner when the latter comprises any.

Summary

One idea underlying the invention is to propose a vessel wall having an aforementioned multilayer structure and making it possible to ensure satisfactory anchoring and relative positioning of the primary panels on the secondary thermally insulating barrier.

According to one embodiment, the invention provides a wall of a liquefied gas storage tank comprising a secondary thermally insulating barrier comprising secondary panels which have the shape of a rectangular parallelepiped, are juxtaposed in parallel secondary rows and are anchored to a load-bearing structure, a secondary sealing membrane carried by the secondary thermally insulating barrier, a primary thermally insulating barrier comprising primary panels which have the shape of a rectangular parallelepiped, are arranged in parallel primary rows and are anchored to the barrier thermally insulating secondary by primary anchoring devices and a primary sealing membrane carried by the primary thermally insulating barrier and intended to be in contact with the liquefied gas contained in the tank; wherein at least one of the primary panels is anchored to the secondary thermal insulation barrier by means of four primary anchors which are each positioned at a corner of said primary panel, said primary panel having a centering hole which is formed in a central portion of said primary panel and in which is fitted a primary centering device fixed to one of the secondary panels.

Thus, the relative positioning of said primary panel with respect to the thermally insulating barrier can be ensured precisely thanks to the primary centering device while the primary anchoring devices which are positioned at each of the four corners of the primary panel ensure an anchoring allowing to prevent the corners of said primary panel from rising under the effect of the thermal contraction of the primary panels and the accelerations due to the movements of the vessel. Thus, the primary centering device provides restraint of the primary panel for forces exerted perpendicular to the direction of thickness of the vessel wall, while the primary anchoring devices provide restraint of the primary panel for forces exerted exerting along the thickness direction of the vessel wall.

According to embodiments, such a vessel wall may comprise one or more of the following characteristics.

According to one embodiment, each of the four primary anchoring devices also cooperates with a corner of four adjacent primary panels so as to anchor them to the secondary thermally insulating barrier. This limits the number of primary anchoring devices used to anchor the primary panels.

According to one embodiment, the secondary panels are anchored to the load-bearing structure by secondary anchoring devices and/or by adhesive mastic cords.

According to one embodiment, the secondary panel on which the primary centering device is fixed comprises four cylindrical wells which are each formed at a corner of said secondary panel and have a change in section providing a bearing surface for a bearing plate one of the secondary anchors. This makes it possible to ensure the anchoring of said secondary panel with respect to the supporting structure while limiting the uncertainty of positioning of the secondary panel with respect to the supporting structure.

According to one embodiment, each secondary panel comprises four cylindrical wells which are each formed at one of the four corners of said secondary panel and have a change in section providing a bearing surface for a bearing plate of one of the secondary anchor devices.

According to one embodiment, the secondary panels have internal and external faces, which are orthogonal to a thickness direction of the tank, said internal and external faces having a square shape defined by four sides of the secondary panels.

According to one embodiment, the primary panels have internal and external faces, which are orthogonal to a thickness direction of the tank, said internal and external faces having a square shape defined by four sides of the primary panels.

According to one embodiment, the primary rows are oriented parallel to a diagonal of the internal face of the secondary panels and each primary panel is arranged astride at least five secondary panels.

According to one embodiment, the centering device which is fitted into the centering hole of the primary panel is fixed to the center of one of the secondary panels and the corners of the primary panel each face one of the devices. primary anchor which is fixed in the center of one of the secondary panels.

According to one embodiment, the four sides of the secondary panels have a length a and the four sides of the primary panels have a length b such that the length a and the length b satisfy the relationship , with n an integer, for example equal to 1 or 2.

According to one embodiment, the secondary waterproofing membrane comprises a continuous sheet of parallel metal strakes each having two raised edges, the raised edges of the welds being welded to weld supports which are housed in grooves formed in an internal face of the secondary panels.

According to one embodiment, the continuous layer of strakes has strakes traversed by primary centering devices and strakes traversed by primary anchoring devices which are placed alternately.

According to one embodiment, the grooves formed in the internal face of the secondary panels are arranged parallel to the primary rows.

According to one embodiment, the grooves formed in the internal face of the secondary panels are arranged parallel to a diagonal of the internal face of the secondary panels, on either side of said diagonal.

According to one embodiment, the primary waterproofing membrane comprises a plurality of corrugated metal sheets welded to each other and fixed to anchor strips fixed to the primary panels.

According to one embodiment, the primary anchoring devices each comprise a base fixed to one of the secondary panels, a stud fixed to said base and developing along a direction of thickness of the wall from said base towards the membrane of primary sealing and passing in a sealed manner through an orifice of the secondary sealing membrane and a support element mounted on the stud and resting on a support surface formed at one of the corners of the primary panel so as to retain at the secondary thermally insulating barrier.

According to one embodiment, the primary anchoring devices further comprise a sealing washer which is engaged on the stud and comprises a flange fixed in leaktight manner to the secondary sealing membrane around the orifice of the sealing membrane. secondary seal and a deformable gasket sealingly connecting the sealing washer to the stud so as to allow relative movement between the sealing washer and the stud.

According to one embodiment, the primary centering devices comprise a bell covering the deformable seal.

According to one embodiment, the deformable seal comprises a deformable bellows, said deformable bellows being hollow and developing around and axially along the stud.

According to one embodiment, the primary centering device comprises:
- a base fixed to one of the secondary panels,
- a stud fixed to said base and developing along a thickness direction of the vessel wall from said base towards the primary sealing membrane and passing through an orifice of the secondary sealing membrane,
- a bell partially covering the stud.

According to one embodiment, the primary centering device comprises:
- a base fixed to one of the secondary panels,
- a stud fixed to said base and developing along a thickness direction of the vessel wall from said base towards the primary sealing membrane and passing through an orifice of the secondary sealing membrane,
- a sealing washer engaged on the stud and comprising a flange fixed in leaktight manner to the secondary sealing membrane around the orifice of the secondary sealing membrane;
- A deformable gasket sealingly connecting the sealing washer to the stud so as to allow relative movement between the sealing washer and the stud; And
- a bell covering the deformable seal.

According to one embodiment, the bell has a cylindrical shape, said bell and the centering orifice having diameters which are adjusted to each other.

According to another embodiment, the primary centering device comprises:
- a base fixed to one of the secondary panels,
- a stud fixed to said base and developing along a thickness direction of the vessel wall from said base towards the primary sealing membrane and passing through an orifice of the secondary sealing membrane, said stud fitting into the primary panel centering hole.

According to one embodiment, the invention relates to a sealed and thermally insulating tank comprising an aforementioned wall.

A tank according to one of the aforementioned embodiments can be part of an onshore storage installation, for example for storing LNG or be installed in a floating, coastal or deep-water structure, in particular an ethane or LNG carrier, a floating storage and regasification unit (FSRU), floating production and remote storage unit (FPSO) and others. In the case of a floating structure, the tank may be intended to receive liquefied natural gas serving as fuel for the propulsion of the floating structure.

According to one embodiment, a vessel for transporting a fluid comprises a hull, such as a double hull, and a aforementioned tank disposed in the hull.

According to one embodiment, the invention also provides a method for loading or unloading such a ship, in which a fluid is routed through insulated pipes from or to a floating or terrestrial storage installation to or from the tank of the ship.

According to one embodiment, the invention also provides a transfer system for a fluid, the system comprising the aforementioned vessel, insulated pipes arranged so as to connect the tank installed in the hull of the vessel to a floating or terrestrial storage installation and a pump for driving a flow of fluid through the insulated pipes from or to the floating or onshore storage facility to or from the vessel's tank.

Brief description of figures

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

Figure 1 is a schematic sectional view of the multilayer structure of a vessel wall.

Figure 2 is a partial cutaway view of a vessel wall.

Figure 3 is a perspective view of a corrugated metal sheet of a primary waterproofing membrane.

Figure 4 is a top view of the secondary thermally insulating barrier.

Figure 5 is a detailed view of a secondary anchor device according to one embodiment.

FIG. 6 is a partial perspective view of the vessel wall illustrating in particular primary anchoring devices and primary centering devices intended to anchor the primary panels to the secondary panels while ensuring relative positioning accuracy.

Figure 7 is a partial view, in section, of a primary anchoring device according to one embodiment.

Figure 8 is a sectional view of the vessel wall in a plane passing through a primary centering device.

FIG. 9 is a cutaway schematic representation of a ship comprising a liquefied natural gas storage tank and a loading/unloading terminal for this tank.

FIG. 10 is a partial view, in section, of a primary centering device according to another embodiment.

By convention, the terms “external” and “internal” are used to define the relative position of one element in relation to another, by reference to the exterior and the interior of the tank. Furthermore, the longitudinal direction L of the tank, represented by an arrow in FIGS. 2 and 4, corresponds to the largest dimension of the tank. When the tank is intended to be placed in the hull of a ship, the longitudinal direction L of the tank is oriented parallel to the longitudinal direction of the ship, that is to say the direction which is oriented from the front towards the back of the ship.

In Figure 1, there is shown schematically the multilayer structure of a wall 1 of a sealed and thermally insulating tank for storing a liquefied gas, such as liquefied natural gas (LNG). Each wall 1 comprises, from the outside towards the inside of the tank, a secondary thermally insulating barrier 2 comprising secondary panels 3 anchored to a supporting structure 4, a secondary sealing membrane 5 resting against the secondary thermally insulating barrier 2 , a primary thermally insulating barrier 6 comprising primary panels 7 resting against the secondary sealing membrane 5 and anchored to the secondary panels 3 and a primary sealing membrane 8 which rests against the primary thermally insulating barrier 6 and which is intended to be in contact with the liquefied gas contained in the tank.

The load-bearing structure 4 can in particular be formed by the hull or the double hull of a ship. The support structure 4 comprises a plurality of walls defining the general shape of the tank, usually a polyhedral shape.

In relation to FIG. 2, it can be seen that the secondary thermally insulating barrier 2 comprises a plurality of secondary panels 3. The secondary panels 2 are anchored to the load-bearing structure 4 by means of cords of mastic 19 and/or anchoring devices secondary 9 which will be described in detail below in relation to Figure 5. The secondary panels 3 have a generally parallelepipedic shape and are arranged in secondary rows parallel to each other. In addition, in the embodiment shown, the internal and external faces of the secondary panels 3, that is to say the faces orthogonal to the direction of thickness of the wall 1 are square in shape. In other words, the four sides 10, 11, 12, 13 of the secondary panels 3 are equal. In addition, the secondary panels 3 are arranged such that the diagonals 14, 15 of the internal and external faces of said secondary panels 3 are arranged respectively parallel and perpendicular to the longitudinal direction L of the tank.

In the embodiment illustrated in Figure 5, the secondary panels 3 have a layer of insulating polymer foam 16 sandwiched between an outer plate 17 and an inner plate 18. The outer plate 17 and the inner plate 18 are, for example , plywood and glued to the insulating polymer foam layer 16. The insulating polymer foam 16 may in particular be a polyurethane-based foam, optionally reinforced with glass fibers.

The structure of the secondary panel 3 is described above by way of example. Also, in another embodiment, the secondary panels 3 are likely to have another general structure, for example that described in document WO2012/127141. In another embodiment, the secondary thermally insulating barrier 2 comprises secondary panels 3 having at least two different types of structure, for example the two aforementioned structures, depending on their location in the tank.

Advantageously, beads of mastic 19 are interposed between the secondary panels 3 and the supporting structure 4 to compensate for the deviations of the supporting structure 4 with respect to a flat reference surface.

Furthermore, in the embodiment shown, the secondary panels 3 are fixed to the load-bearing structure 4 by means of secondary anchoring devices 9, shown in FIG. 5. The secondary anchoring devices 9 each comprise a stud 20 welded to the support structure 4 and projecting from the support structure 4 towards the inside of the tank and a support plate 21 which is fixed to the end of the pin 20 and which bears against a support zone 22 of the secondary panel 3 so as to retain it against the support structure 4. In the embodiment shown, the secondary panels 3 are provided with cylindrical wells 23 which pass through them over their entire thickness. Furthermore, the cylindrical wells 23 have a change in section, the section of the cylindrical wells 23 being wider at the level of the layer of insulating polymer foam 16 and of the internal plate 18 than at the level of the external plate 17. Thus, the support plate 21 which is fixed to the end of the stud 20 bears against the outer plate 17. The support plate 21 is, for example, an annular plate which has an orifice threaded onto the stud 20. A nut 24 cooperates with a threaded end of the stud 20 so as to ensure the fixing of the support plate 21 on the stud 20.

In addition, according to one embodiment, Belleville washers 25 can be threaded onto the stud 20, between the nut 24 and the support plate 21, which makes it possible to ensure an elastic anchoring of the secondary panels 3 on the structure. carrier 4. Advantageously, an insulating plug 26 made of insulating polymer foam is arranged in each cylindrical well 23 in order to ensure continuity of the thermal insulation of the secondary thermally insulating barrier 2.

According to a variant embodiment, the secondary panels 3 are fixed to the bearing structure by means of mastic cords 19, described above, which adhere to the bearing structure 4 and to the secondary panels 3. In such a variant embodiment, the secondary anchoring devices 9 are optional.

In Figures 2 and 4, it is observed that each secondary panel 3 advantageously has four cylindrical wells 23 each arranged near one of the four corners of said secondary panel 3.

In addition, the secondary sealing membrane 5, partially illustrated in Figure 2, comprises a continuous layer of strakes 27, metal, having two raised edges, parallel. The strakes 27 are welded by their raised edges to parallel welding supports which are housed in grooves 28 formed in the internal plate 18 of the secondary panels 3. The grooves 28 are oriented parallel to the longitudinal direction L. To do this, the internal plate 18 of each secondary panel 3 is equipped with two grooves 28 parallel to the longitudinal direction L of the tank and therefore parallel to one of the diagonals 14 of the internal face of the secondary panels 3. The two grooves 28 of each plate internal 18 are arranged on either side of the diagonal 14. The strakes 27 are, for example, made of Invar ®: that is to say an alloy of iron and nickel whose expansion coefficient is typically included between 1.2.10-6 and 2.10-6 K-1. It is also possible to use alloys of iron and manganese whose expansion coefficient is typically around 7 to 9.10-6 K-1.

Furthermore, the primary thermally insulating barrier 6 comprises a plurality of primary panels 7 which are anchored to the secondary thermally insulating barrier 2 by means of primary anchoring devices 29, described in more detail below. The primary panels 7 have a generally parallelepipedal shape and are arranged in primary rows which are parallel to each other and parallel to the longitudinal direction L of the tank.

In the embodiment shown, the internal and external faces of the primary panels 7, that is to say the faces orthogonal to the direction of thickness of the wall 1, are square in shape. Each primary panel 7 straddles five secondary panels 3 so that the four corners 30, 31, 32, 33 of each primary panel 7 as well as the center 34 of said primary panel 7 coincide with the center of one of the secondary panels 3. To do this, the primary rows of primary panels 7 are oriented parallel to the longitudinal direction L of the ship. In other words, a pair of opposite sides 35, 36 of each primary panel 7 is parallel to one of the diagonals 14 of each secondary panel 3 and the other pair of opposite sides 37, 38 of each primary panel 7 is parallel to one of the diagonals 15 of each secondary panel 3. In addition, the dimension of the secondary panels 3 is such that the diagonals 14, 15 of the inner and outer faces of the secondary panels 3 have a length equal or substantially equal to the length of the sides 35, 36, 37, 38 of the primary panels 7. In other words, there is a relationship between the length a of the sides 10, 11, 12, 13 of the secondary panels 3 and the length b of the sides 35, 36 , 37, 38 of the primary panels 7 as .

Thus, given the aforementioned arrangement, each primary panel 7 is anchored by means of four primary anchoring devices 29 which are each positioned at one of the corners 30, 31, 32, 33 of said primary panel 7 and are each fixed to the center 34 of one of the secondary panels 3. In addition, the primary panel 7 is also centered with respect to the secondary thermally insulating barrier 2 by means of a primary centering device 41 which passes through a centering orifice 42 formed in the center of the outer face of the primary panel 7 and which is fixed to the center of the inner face of one of the secondary panels 3. It is also noted that the secondary membrane comprises an alternation of strakes through which devices primary centering 41 and strakes traversed by primary anchoring devices 29.

According to another alternative embodiment not shown, the length a of the sides 10, 11, 12, 13 of the secondary panels 3 and the length b of the sides 35, 36, 37, 38 of the primary panels 7 are such that . In this case, each primary panel 7 straddles 13 secondary panels 3.

The primary panels 7 may have a multilayer structure analogous to the structure of the secondary panels 3. Thus, according to the embodiment represented for example in FIG. 8, the primary panels 7 comprise successively, along the thickness direction of the wall 1, tank an outer plate 43, for example plywood, a layer of insulating polymer foam 44 and an inner plate 45, for example plywood. The insulating polymer foam layer 44 is for example a polyurethane-based foam, optionally reinforced with glass fibers.

The structure of the primary panel 7 is described above by way of example. Also, in another embodiment, the primary panels 7 are likely to have another general structure, for example that described in document WO2012/127141. In another embodiment, the primary thermally insulating barrier 6 comprises primary panels 7 having at least two different types of structure, for example the two aforementioned structures, depending on their location in the tank.

As illustrated in Figure 8, the outer plate 43 of the primary panels 7 has grooves 46 which receive the raised edges of the strakes 27 of the secondary sealing membrane 5. The grooves 46 are oriented parallel to the longitudinal direction L of the tank and, therefore, parallel to two opposite sides 35, 36 of said primary panel 7.

Furthermore, the internal plate 45 comprises anchoring strips 47, illustrated in FIGS. 2, 6 and 8, to anchor the primary sealing membrane 8. These anchoring strips 47 are housed in counterbores formed in the plate internal 45.

The primary sealing membrane 8 is obtained by assembling a plurality of corrugated metal sheets 48, for example by welding, one of which is shown in Figure 3. Each corrugated metal sheet 48 has two series of mutually perpendicular corrugations . The corrugations protrude inward from the tank. Adjacent corrugated metal sheets 48 are lap welded together along their edges. In addition, the corrugated metal sheets 48 are attached to the anchor strips 47, for example by spot welds. The corrugated metal sheets 48 are, for example, made of stainless steel or aluminum. The corrugated metal sheets 48 are rectangular, and preferably have width and length dimensions which are whole multiples of a spacing between corrugations and also whole multiples of the dimensions of the primary panels 7.

As shown in Figure 6, each primary panel 7 has recesses at its corners 30, 31, 32, 33 so that the outer plate 43 projects beyond the layer of insulating polymer foam 44 and the plate. internal 45. Thus, the outer plate 43 forms at the corners of the primary panel 7 a support zone intended to cooperate directly or indirectly with a support plate 49 of a primary anchoring device 29. In addition, in the embodiment shown, a wedge 50 is added to the outer plate 43, said wedge 50 having a shape similar to that of the support zone and cooperating with the support plate 49 to anchor the primary panel 7.

Each primary anchoring device 29 cooperates with four support zones belonging respectively to the corners 30, 31, 32, 33 of four adjacent primary panels 7. Each primary anchor 29 has a pin 51 which projects from the center of one of the secondary panels 3, a backing plate 49 which is attached to the end of the pin 51 and bears against the four support zones of the four adjacent primary panels 7 so as to retain them against the secondary thermally insulating barrier 2. The support plate 49 comprises a bore threaded onto the stud 51. A nut 52 cooperates with a threaded end of the stud 51 of so as to ensure the fixing of the support plate 49. In addition, according to an advantageous embodiment, Belleville washers are threaded onto the stud 51, between the nut 52 and the support plate 49, which allows ensure elastic anchoring of the primary panels 7 on the secondary thermally insulating barrier 2.

As illustrated in Figure 7, the stud 51 is fixed to a base 53 which is itself fixed to the internal plate of the secondary panels 3. To do this, the base 53 comprises, for example, a thread which cooperates with one end threaded complementary to stud 51. Furthermore, internal plate 18 of secondary panels 3 has a recess in which base 53 is housed. diameter so as to provide a shoulder 54. The base 53 has a shape complementary to that of the recess. Thus, the internal face of the base 53 is flush with the internal face of the internal plate 18 of the secondary panels 3 so as to form a flat support surface for the secondary sealing membrane 5. In addition, the base 53 has a section external having a larger diameter than its internal section so that the external section of said base 53 is in abutment against the shoulder 54 of the recess. The base 53 is also glued to the secondary panel 3.

Furthermore, the stud 51 passes through in leaktight manner an orifice made in the secondary sealing membrane 5. In the embodiment shown, the primary anchoring device 29 comprises a sealing washer 55 in order to ensure the sealing of the secondary sealing membrane 5 at the level of its orifice through which the stud 51 passes. The sealing washer 55 has a flange developing radially with respect to the axis of the stud 51 and a central orifice in which the stud is engaged 51 with a clearance allowing relative movement between the sealing washer 55 and the stud 51. The flange is fixed in a sealed manner to the secondary sealing membrane 5 around the orifice of said secondary sealing membrane 5. This sealed attachment is, for example, made by welding. Furthermore, stud 51 has an anchoring shoulder 56 projecting radially outwards from stud 51. In addition, a deformable joint 57 is welded in a sealed manner, on the one hand, to sealing washer 55 and , on the other hand, to the anchoring shoulder 56 of the stud 51, which makes it possible to seal the passage of the stud 51 through the secondary sealing membrane 5. In the embodiment shown, the deformable seal 57 is a bellows, for example made of stainless steel. Thus, the sealed connection between the secondary sealing membrane 5 and the stud 51 is flexible, which allows relative movements of the primary panels 7 and/or secondary panels 3 with respect to the secondary sealing membrane 5 and thus makes it possible to limit the risks of degradation of the sealing of said secondary sealing membrane 5.

In order to protect the deformable joint, the primary anchoring device 29 is also equipped with a bell 58 which has an orifice in which the stud 51 is threaded and which covers the said deformable joint 57. In the embodiment shown, the bell 58 has a generally cylindrical shape.

In relation to FIG. 8, a description is given below of a primary centering device 41 making it possible to ensure precise relative positioning of the primary panels 7 with respect to the secondary thermally insulating barrier 2. In the embodiment shown, the primary centering device 41 has a structure identical to that of the primary anchoring device 29, described above, with the exception of the bearing plate 49, the nut 52 and the Belleville washers of the primary anchoring devices 29 which are not necessary for the primary centering device 41 since that is only intended to ensure relative positioning and not anchoring on the secondary thermally insulating barrier 2. The primary panels 7 include a centering orifice 42 which is formed in the center of the primary panels 7 and opens at the outer face of the primary panels 7. Each primary centering device 41 is fitted inside said centering hole 42 d e so as to ensure the relative positioning of the primary panels 7 with respect to the secondary panels 3. In the embodiment shown, the diameter of the bell 58 of the primary centering device 41 and the diameter of the centering orifice 42 are adjusted l to each other, ensuring relative positioning accuracy.

Figure 10 illustrates a primary centering device 41 according to an alternative embodiment. This embodiment differs in particular from that described above with reference to FIGS. 7 and 8 in that the primary centering device 41 comprises neither a deformable seal 57 nor a bell 58. In this embodiment, it is the pin 51 which fits into the centering hole 42, in order to perform the relative positioning function. As in the previous embodiment, the primary centering device 41 comprises a stud 51 which passes through an orifice made in the secondary sealing membrane 5. The stud 51 is fixed to a base 53 which is itself fixed to the plate internal secondary panels 3. To do this, the base 53 comprises, for example, a thread which cooperates with a complementary threaded end of the stud 51. According to one embodiment, the sealing of the crossing of the primary centering device 41 to the through the secondary sealing membrane 5 can be ensured by welding the secondary sealing membrane 5 on the base 53 all around the orifice through which the stud 51 passes. In the embodiment shown, the stud 51 has a collar 59 which extends radially with respect to the axis of the stud 51 and is arranged towards the inside of the tank with respect to the secondary sealing membrane 5. In addition or alternatively to the sealed welding of the membrane e secondary waterproofing membrane 5 on the base 53, the flange 59 can be welded in a leaktight manner to the secondary waterproofing membrane 5.

The stud 51 has a larger diameter than the stud 51 of the embodiment of FIG. 8. In addition, the diameter of the stud 51 is adjusted to that of the centering orifice 42, which makes it possible to ensure the precision of the relative positioning.

Referring to Figure 9, a cutaway view of an LNG carrier 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary sealing membrane intended to be in contact with the LNG contained in the tank, a secondary sealing membrane arranged between the primary sealing membrane and the double hull 72 of the ship, and two thermally insulating barriers arranged respectively between the primary sealing membrane and the secondary sealing membrane and between the secondary sealing membrane and the double shell 72.

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

FIG. 9 also represents an example of a maritime terminal comprising a loading and unloading station 75, an underwater pipe 76 and an installation on land 77. The loading and unloading station 75 is a fixed off-shore installation comprising a movable arm 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 which can be connected to the loading/unloading pipes 73. The adjustable movable arm 74 adapts to all sizes of LNG carriers. A connecting pipe, not shown, extends inside the tower 78. The loading and unloading station 75 allows the loading and unloading of the LNG carrier 70 from or to the shore installation 77. This comprises liquefied gas storage tanks 80 and connecting pipes 81 connected by the underwater pipe 76 to the loading or unloading station 75. The underwater pipe 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the shore installation 77 over a great distance, for example 5 km, which makes it possible to keep the LNG carrier 70 at a great distance from the coast during loading and unloading operations.

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

Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the claimed invention.

In particular if, in the embodiments described, the primary panels are anchored by means of four primary anchoring devices, it is not excluded that a higher quantity of primary anchoring devices is used to anchor each primary panel .

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

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

Claims (21)

Wall (1) of a storage tank for a liquefied gas comprising a secondary thermally insulating barrier (2) comprising secondary panels (3) which have the shape of a rectangular parallelepiped, are juxtaposed in parallel secondary rows, and are anchored to a supporting structure (4), a secondary sealing membrane (5) carried by the secondary thermally insulating barrier (2), a primary thermally insulating barrier (6) comprising primary panels (7) which have the shape of a rectangular parallelepiped , are juxtaposed in parallel primary rows and are anchored to the secondary thermally insulating barrier (2) by primary anchoring devices (29) and a primary sealing membrane (8) carried by the primary thermally insulating barrier (6) and intended to be in contact with the liquefied gas contained in the tank; wherein at least one of the primary panels (7) is anchored to the secondary thermal insulation barrier by means of four primary anchors (29) which are each positioned at a corner (30, 31, 32, 33 ) of said primary panel (7), said primary panel (7) comprising a centering orifice (42) which is provided in a central portion of said primary panel (7) and in which is fitted a primary centering device (41) fixed to one of the secondary panels (3). Wall (1) according to Claim 1, in which each of the four primary anchoring devices (29) also cooperates with a corner (30, 31, 32, 33) of four adjacent primary panels (7) so as to anchor them to the secondary thermally insulating barrier (2). Wall according to Claim 1 or 2, in which the secondary panels (3) are anchored to the load-bearing structure (4) by secondary anchoring devices (9) and/or by adhesive cords of mastic (19). Wall (1) according to Claim 3, in which the secondary panel (3) on which the primary centering device (41) is fixed comprises four cylindrical wells (23) which are each formed at a corner of the said secondary panel (3) and have a change in section providing a bearing surface (22) for a bearing plate (21) of one of the secondary anchoring devices (9). Wall (1) according to any one of Claims 1 to 4, in which the secondary panels (3) have internal and external faces, which are orthogonal to a direction of thickness of the tank, the said internal and external faces presenting a square shape defined by four sides (10, 11, 12, 13) of the secondary panels (3). Wall (1) according to Claim 1 to 5, in which the primary panels (7) have internal and external faces, which are orthogonal to a direction of thickness of the tank, the said internal and external faces having a square shape defined by four sides (35, 36, 37, 38) of the primary panels (7). Wall (1) according to Claims 5 and 6 taken in combination, in which the primary rows are oriented parallel to a diagonal (14) of the internal face of the secondary panels (3) and each primary panel (7) is arranged astride five secondary panels (3). Wall (1) according to Claim 7, in which the primary centering device (41) which is fitted into the centering hole (42) of the primary panel (7) is fixed to the center of one of the secondary panels (3 ) and in which the corners (30, 31, 32, 33) of the primary panel (7) each face one of the primary anchoring devices (29) which is fixed to the center of one of the secondary panels (3). Wall (1) according to Claim 8, in which the four sides (10, 11, 12, 13) of the secondary panels (3) have a length a and the four sides (35, 36, 37, 38) of the primary panels ( 7) have a length b such that the length a and the length b satisfy the relation . Wall (1) according to any one of claims 1 to 9, in which the secondary sealing membrane (5) comprises a continuous layer of parallel metal strakes (27) each having two raised edges, the raised edges of the welds being welded on welding supports which are housed in grooves (28) formed in an internal face of the secondary panels (3). Wall (1) according to Claim 10, in which the continuous sheet of strakes (27) has strakes traversed by primary centering devices (41) and strakes traversed by primary anchoring devices (29) which are placed in alternation. Wall (1) according to Claim 10 or 11, in which the grooves (28) formed in the internal face of the secondary panels (3) are arranged parallel to the primary rows. Wall (1) according to any one of Claims 1 to 12, in which the primary anchoring devices (29) each comprise a base (53) fixed to one of the secondary panels (3), a dowel (51) fixed to said base (53) and developing along a direction of thickness of the wall (1) from said base (53) towards the primary sealing membrane (8) and passing through in sealed manner an orifice of the secondary sealing (5) and a support element (49) mounted on the stud (51) and resting on a support surface formed at one of the corners (30, 31, 32, 33) of the primary panel ( 7) so as to hold it to the secondary thermally insulating barrier (2). Wall (1) according to any one of Claims 1 to 13, in which the primary anchoring devices (29) further comprise a sealing washer (55) which is engaged on the stud (51) and comprises a flange sealed to the secondary sealing membrane (5) around the orifice of the secondary sealing membrane (5) and a deformable seal (57) sealingly connecting the sealing washer (55) to the stud (51) so as to allow relative movement between the sealing washer (55) and the pin (51). Wall (1) according to any one of Claims 1 to 14, in which the primary centering device (41) comprises:
- a base (53) fixed to one of the secondary panels (3),
- a stud (51) fixed to said base (53) and developing along a direction of thickness of the wall (1) of the tank from said base (53) towards the primary sealing membrane (8) and passing through an orifice the secondary sealing membrane (5),
- a sealing washer (55) engaged on the stud and comprising a flange fixed in leaktight manner to the secondary sealing membrane (5) around the orifice of the secondary sealing membrane (5);
- a deformable seal (57) sealingly connecting the sealing washer (55) to the stud (51) so as to allow relative movement between the sealing washer (55) and the stud (51); And
- a bell (58) covering the deformable seal (57). Wall (1) according to claim 15, in which the bell (58) has a cylindrical shape, said bell (58) and the centering orifice (42) having diameters which are adjusted to each other. Wall (1) according to any one of Claims 1 to 16, in which the primary centering device (41) comprises:
- a base (53) fixed to one of the secondary panels (3),
- a stud (51) fixed to said base (53) and developing along a direction of thickness of the wall (1) of the tank from said base (53) towards the primary sealing membrane (8) and passing through an orifice of the secondary sealing membrane (5), said stud (51) fitting into the centering hole (42) of the primary panel (7). Sealed and thermally insulating tank comprising a wall (1) according to any one of claims 1 to 17. Vessel (70) for the transport of a fluid, the vessel comprising a hull (72) and a tank (71) according to claim 18 disposed in the hull. Transfer system for a fluid, the system comprising a ship (70) according to claim 19, insulated pipes (73, 79, 76, 81) arranged to connect the tank (71) installed in the hull of the ship to a floating or onshore storage facility (77) and a pump for driving fluid through the insulated pipelines from or to the floating or onshore storage facility to or from the vessel's tank. Method of loading or unloading a ship (70) according to claim 19, 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 ship's tank (71).