WO2021053055A1

WO2021053055A1 - Sealed and thermally insulating tank

Info

Publication number: WO2021053055A1
Application number: PCT/EP2020/075937
Authority: WO
Inventors: Amaury Mange
Original assignee: Gaztransport Et Technigaz
Priority date: 2019-09-18
Filing date: 2020-09-17
Publication date: 2021-03-25
Also published as: FR3100860B1; KR20220062405A; CN114423986B; EP4031798A1; FR3100860A1; CN114423986A

Abstract

The invention concerns a sealed and thermally insulating tank (1) for storing a liquefied gas, the tank (1) comprising: - a plurality of walls defining an internal space (3) intended for storing the liquefied gas, the plurality of walls comprising a top wall (10); and - a collection line (2) intended to extract liquefied gas in the vapour phase, which protrudes downwards beyond the top wall (10) r h; and - at least one first pipe (22) intended to convey liquefied gas in the vapour phase from the internal space (3) of the tank (1) towards the collection line (2), the first pipe (22) further comprising a diverted section (25) that passes below the lower end (15) of the collection line (2) in order to connect the first and second ends (23, 24) of the first pipe (22).

Description

Title of the invention: Tight and thermally insulating tank

Technical area

The invention relates to the field of tanks, sealed and thermally insulating 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 -50 ° C and 0 ° C, or for the transport of Liquefied Natural Gas (LNG) at approximately -162 ° C at atmospheric pressure.

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

Technological background

[0003] Document WO2013093261 discloses a sealed and thermally insulating tank for the storage of a liquefied gas in a state of liquid-vapor equilibrium. Due to the phenomena of heat transfer between the inside and the outside of the tank, the liquefied gas stored in the tank absorbs heat, which causes it to evaporate. Also, the vessel is equipped with a collecting pipe which passes through a wall of the vessel and which is intended to extract steam from the gas overhead of the vessel. The collecting pipe opens into the internal space of the tank to define a passage between the internal space of the tank and a vapor collector which is arranged outside the tank and which is connected for example to a degassing mast. . The collecting pipe is connected to the vapor manifold via a safety valve which is calibrated in order to ensure evacuation of the gas in the vapor phase of the vessel, when the vapor pressure in the gas overhead of the vessel is greater than a threshold pressure. This allows the pressure inside the tank to be controlled so as to avoid overpressures that could damage the tank.

The walls of the sealed tank have a multilayer structure, that is to say comprise successively, from the outside to the inside of the tank, a secondary thermally insulating barrier, a secondary waterproof membrane, a thermally barrier primary insulation and a primary waterproof membrane. In order to ensure the continuity of the primary waterproof membrane around the collecting pipe, the latter is connected in a sealed manner to the primary waterproof membrane by means of a collar which has an L-shaped section and which protrudes. inside space inside the tank. The lower end of the collecting pipe therefore protrudes into the internal space of the tank, beyond the sealed primary membrane.

[0005] For safety reasons, it should be ensured that, when the tank is filled to its maximum level, the gas overhead of the tank remains in communication with the interior of the collecting pipe. However, in order to prevent the lower end of the collecting pipe from being immersed in the liquid phase of the liquefied gas, thus preventing the gas phase present in the upper part of the internal space of the vessel from being extracted by the gas phase. collecting pipe, the maximum filling level of the tank is likely to be reduced, which is not fully satisfactory.

This drawback is particularly critical when, in order to give more flexibility to the connection between the waterproof primary membrane and the collecting pipe, the height of the flange is important and / or when the internal space of the tank has a low height.

summary

An idea at the basis of the invention is to provide a tank equipped with a collecting pipe intended to collect steam in the gas overhead of the tank and passing through a ceiling wall of the tank and which allows load an optimum quantity of liquefied gas while allowing the vapor to be extracted from the gas overhead via said collecting pipe and, whatever the vertical dimension of the portion of said collecting vapor pipe projecting inside the internal space of the tank.

[0008] According to one embodiment, the invention provides a sealed and thermally insulating tank for the storage of a liquefied gas, said tank comprising:

a plurality of walls defining an internal space intended for the storage of liquefied gas, the plurality of walls comprising an upper wall; and

a collecting pipe intended to extract, from the internal space of the vessel, liquefied gas in the vapor phase, said collecting pipe passing through the upper wall, and comprising a lower end which opens into the internal space and which projects towards the low, beyond the upper wall, to a height h; and

- at least a first pipe intended to conduct liquefied gas in vapor phase from the internal space of the vessel to the collecting pipe, said first pipe comprising a first and a second end, the first end being located in the internal space of the tank, outside the collecting pipe, and opening into said internal space at a height h1 greater than h, the second end opening inside the collecting pipe at a height h2 greater than h, the first pipe comprising a diverted section that passes below the lower end of the header pipe to connect the first and second ends of the first pipe.

[0009] Thus, the first pipe provides fluid communication between the gas overhead and the interior space of the header pipe even if the lower end of the header pipe is immersed in the liquid phase of the liquefied gas.

[0010] According to embodiments, such a tank may include one or more of the following characteristics.

[0011] According to one embodiment, the diverted section has a U-shape.

According to one embodiment, the height h is less than a maximum loading level hmax. Thus, the pipe makes it possible to fill the tank above the lower end of the collecting pipe while allowing the extraction of vapor from the gaseous sky in the event of overpressure.

According to one embodiment, the height h1 is greater than the maximum loading level hmax.

According to one embodiment, the height h2 is greater than the maximum loading level hmax.

According to one embodiment, the header pipe is connected to a safety valve which is configured to extract liquefied gas in the vapor phase from the header pipe when the pressure in the interior space of the header pipe is greater than a threshold pressure Ps.

[0016] According to one embodiment, the threshold pressure Ps satisfies the following inequality:

Ps <Pdesign - f ^* g ^* min; with: min: the smallest value among (h2 - h3) and I.

[0017] According to one embodiment, the threshold pressure Ps satisfies the following inequality:

Ps <Pdesign - f ^* g ^* (h2 - h3); with:

P design: the maximum design pressure for which the tank was dimensioned; f: the density of the liquefied gas intended to be stored in the tank; g: the normal acceleration of gravity; h2: the height of the second end of the first pipe; and h3: a height of the lowest point of the first pipe.

According to one embodiment, the threshold pressure Ps further satisfies the following inequality: Ps> Pdesign - f * g * (h2 - h3) - k; with k between 100 and 1000 Pa.

[0019] According to another embodiment, the threshold pressure Ps satisfies the following inequality: Ps <Pdesign - f * g * I; with:

P design: the maximum design pressure for which the tank was dimensioned; f: the density of the liquefied gas intended to be stored in the tank; g: the normal acceleration of gravity; and

I: a length of the first pipe which is likely to be filled with liquefied gas, when the tank is charged with liquefied gas up to a maximum loading level hmax.

[0020] According to one embodiment, the threshold pressure Ps further satisfies the following inequality:

Ps> Pdesign - f * g * I - k; with k between 100 and 1000 Pa.

According to one embodiment, the upper wall comprises a sealed primary membrane intended to be in contact with the liquefied gas stored in the tank, the sealed primary membrane having corrugations projecting towards the inside of the tank and the pipe. collector protrudes inside the internal space, beyond the corrugations of the waterproof primary membrane.

According to one embodiment, the collecting pipe projects inside the internal space, beyond the upper wall, by a vertical distance greater than 80 mm, preferably greater than 100 mm, by example of the order of 150 mm.

[0023] According to one embodiment, the tank comprises one or more lines for loading and / or unloading the tank which pass inside the collecting pipe. Thus, the collecting pipe forms both a gas dome structure and a liquid dome structure, which makes it possible to simplify the construction of the vessel and to reduce its cost.

According to one embodiment, the upper wall comprises at least one primary thermally insulating barrier and a waterproof primary membrane retained at the primary thermally insulating barrier, the upper wall comprising metal anchoring plates which are fixed to the thermally barrier primary insulation and to which metal sheets of the waterproof primary membrane are welded in a sealed manner, the first pipe being anchored in an anchoring zone provided on one of the metal anchoring plates or provided on a portion of the membrane waterproof primer which is anchored to one of the metal anchoring plates. This makes it possible to avoid tearing of the waterproof primary membrane.

[0025] According to one embodiment, the vessel comprises a second pipe intended to conduct liquefied gas in the vapor phase from the internal space of the vessel to the collecting pipe, said second pipe comprising a first and a second end, the first end being located in the internal space of the tank, outside the collecting pipe, and opening into said internal space at a height h'1 greater than h, the second end opening inside the collecting pipe at a height h'2 greater than h.

[0026] According to one embodiment, the first end of the first pipe and the first end of the second pipe are arranged on either side of a median longitudinal vertical plane of the tank.

According to one embodiment, the first end of the first pipe and the first end of the second pipe are arranged near two ends of the upper wall, opposite to each other in a transverse direction perpendicular to the direction longitudinal ship

According to one embodiment, the median longitudinal vertical plane of the tank is parallel to the longitudinal direction of the vessel on which the tank is integrated and passes through the center of gravity of the vessel.

[0029] According to one embodiment, the upper wall covers the internal space.

Such a tank can be part of an onshore storage installation, for example to store LNG or be installed in a floating, coastal or deep water structure, in particular an LNG vessel, a floating storage and regasification unit (FSRU), a floating production and remote storage unit (FPSO), and others.

[0031] According to one embodiment, the invention provides a vessel for transporting a fluid, the vessel comprising a double hull and a above-mentioned tank, arranged in the double hull.

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

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

Brief description of the figures

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

[0035] [fig.1] Figure 1 is a schematic view, in cross section, of a sealed and thermally insulating tank equipped with a collecting pipe and a pipe intended to conduct the vapor from the gas overhead of the tank to the interior space of the collecting pipe.

[0036] [fig.2] Figure 2 is a front view illustrating in detail the header pipe and the pipe of Figure 1.

Figure 3 is a bottom perspective view illustrating in detail the header and the pipe of Figure 1.

[0038] [Fig.4] Figure 4 is a schematic view, in cross section, of a sealed and thermally insulating tank according to another embodiment.

[0039] [fi g.5] Figure 5 is a schematic view of an area of the primary sealing membrane of the upper wall for anchoring a pipe, according to a first embodiment.

[0040] [fi g.6] Figure 6 is a schematic view of an area of the primary waterproof membrane of the upper wall intended for anchoring a pipe, according to a second embodiment.

[0041] [Fig.7] Figure 7 illustrates means for anchoring the pipe to the upper wall according to one embodiment.

[0042] [fig.8] Figure 8 is a cutaway schematic representation of a ship comprising a liquefied natural gas storage tank and a loading / unloading terminal of this tank. Description of the embodiments

In relation to Figure 1, there is a sealed and thermally insulating tank 1 equipped with a header 2 for extracting liquefied gas in the vapor phase from the internal space of the tank. The tank 1 is intended to store a liquefied gas which is for example chosen from liquefied natural gas (LNG) and liquefied petroleum gas (LPG).

The tank 1 is arranged inside a supporting structure 4 which is, for example, formed by the double hull of a ship but can, more generally, be formed of any type of rigid partition having properties appropriate mechanics.

The tank 1 is advantageously a membrane tank. The tank 1 has a plurality of walls defining an internal space 3 intended for the storage of the liquefied gas. Each wall has a multilayer structure and comprises, in the direction of thickness of said wall, from the outside to the inside of the tank 1, a secondary thermally insulating barrier 5 resting against the supporting structure 4, a waterproof secondary membrane 6 resting on it. against the secondary thermally insulating barrier 5, a primary thermally insulating barrier 7 resting against the waterproof secondary membrane 6 and a waterproof primary membrane 8 intended to be in contact with the liquefied gas stored in the tank 1 and resting against the primary thermally insulating barrier 7 According to an alternative embodiment, each wall has only one waterproof primary membrane 8 and a primary thermally insulating barrier 7 resting against the supporting structure 4.

[0046] According to one embodiment of the invention, the waterproof primary membrane 8 is a corrugated membrane. Thus, the waterproof primary membrane 8 comprises a plurality of metal sheets comprising corrugations projecting towards the internal space 3 of the tank 1 and thus allowing the waterproof primary membrane 8 to deform under the effect of the thermal and mechanical stresses generated. by the liquefied gas stored in the tank 1. Such a tank 1 is for example of Mark III® type as described in patent application FR2691520. By way of example, the tank 1 can also be of the N096 ® type, as described in patent application FR2877638.

As illustrated in Figure 1, the tank 1 comprises a bottom wall 9, a top wall 10 opposite the bottom wall 9, side walls 11, 12, 13 connecting the bottom wall 9 and the top wall 10 as well as transverse walls 14 also connecting the bottom wall 9 and the upper wall 10. In the embodiment shown, the tank 1 has, in section along a transverse plane, a section of octagonal shape. Thus, the tank 1 has vertical side walls 11 and inclined side walls. 12, 13 each connecting one of the vertical side walls 11 to the bottom wall 9 or to the top wall 10.

The tank 1 comprises a collecting pipe 2 which is intended to extract the vapor of liquefied gas contained in the gas overhead, that is to say the upper portion of the internal space 3 of the tank 1 in which the liquefied gas is in the gaseous state. The collecting pipe 2 passes through the upper wall 10 of the tank 1. The collecting pipe 2 has an open lower end 15 which opens into the internal space 3 of the tank 1 and projects downwards beyond the upper wall 10. The lower end 15 of the collecting pipe 2 is positioned. at a height h relative to the bottom wall 9 of the tank 1. The height h is less than the maximum filling level hmax of the tank 1 so that, when the tank 1 is charged with liquefied gas up to its level maximum hmax, the lower end 15 of the collecting pipe 2 is immersed in the liquid phase of the liquefied gas. The upper end 16 of the collecting pipe 2 is sealed by a cover 17.

The interior space 18 of the collecting pipe 2 is connected to a vapor manifold, not shown, via at least one pipe equipped with a safety valve 19. The safety valve 19 is calibrated so as to ensure evacuation of the gas in the vapor phase, when the pressure in the interior space 18 of the collecting pipe 2 exceeds a threshold pressure Ps. Thus, the collecting pipe 2 aims, in the event of overpressure, to extract vapor of the gas overhead and thus makes it possible to control the pressure in the gas overhead so as to avoid overpressures liable to damage the tank 1. By way of example, the steam collector is arranged to conduct the extracted steam to a degassing mast , to a burner, to a ship propulsion device or to a liquefaction device in which the gas in the vapor phase is re-liquefied and then reintroduced into the tank 1 in the liquid phase. In the embodiment shown, the interior space 18 of the collecting pipe 2 is connected to the steam manifold by means of two safety valves 19, which provides redundancy making it possible to improve the reliability of the extraction of water. steam.

The collecting pipe 2 is connected in a sealed manner to the waterproof primary membrane 8 so as to ensure continuity of the seal. To do this, the collecting pipe 2 is connected to the waterproof primary membrane 8 by means of a flange 20 having an L-shaped section. The flange 20 has a cylindrical portion of vertical orientation and an annular flange of horizontal orientation. The cylindrical portion is sealed all around the collector pipe 2. The annular flange projects horizontally from the upper end of the cylindrical portion and is sealed to the waterproof primary membrane 8. A such a collar 20 makes it possible to give the connection between the collecting pipe 2 and the impervious primary membrane 8 a flexibility making it possible to absorb the thermal and dynamic stresses.

Advantageously, as shown in Figure 1, the tank 1 comprises one or more lines 21 for loading and / or unloading the tank 1 which pass inside the collecting pipe 2 and cross so seals its cover 17. The line 21 when it is intended to ensure the unloading of the tank 1 extends to the immediate vicinity of the bottom wall 9. The lower end of the line 21 is then equipped with a unloading pump, not shown in figure 1.

According to an embodiment not shown, the lines for loading and / or unloading are formed by vertical masts of a loading / unloading tower. The loading / unloading tower comprises, for example a tripod structure, that is to say it has three vertical masts which are each fixed to each other by cross members. Each of the masts is hollow and passes through the cover 17 of the collecting pipe 2. Each of the masts thus forms a loading line making it possible to charge liquefied gas to the tank 1, an unloading line making it possible to unload liquefied gas from the tank 1. or an emergency well allowing the descent of an emergency pump and an unloading line, in the event of failure of an unloading pump.

Thus, in the embodiments described above, the collecting pipe 2 forms both a gas dome structure and a liquid dome structure. In other words, the functions for managing the pressure of the gas overhead as well as the functions for loading and / or unloading the tank 1 with liquefied gas are provided by a single structure, which makes it possible to simplify the construction of the tank. tank 1 and reduce its cost, by limiting the number of specific structures. However, on the other hand, when the collecting pipe 2 also serves for the passage of at least one loading and / or unloading line 21, it has a larger diameter, which leads to an increase in the axial dimension of the collar 20. in order to give sufficient flexibility to the connection between the collecting pipe 2 and the sealing membrane and to an increase in the size of the part of the collecting pipe 2 which protrudes inside the tank 1.

As shown in Figures 2 and 3, when the waterproof primary membrane 8 is a corrugated membrane having corrugations projecting towards the internal space 3 of the tank 1, the collecting pipe 2 protrudes, inside the internal space 3 of the tank 1, towards the bottom wall 9, beyond the corrugations. According to one embodiment, the collecting pipe 2 protrudes inside the tank 1, by a distance greater than 80 mm, preferably greater than 100 mm and for example of the order of 150 mm per relative to the reference plane of the waterproof primary membrane 8 of the upper wall 10.

Furthermore, the tank 1 is equipped with a pipe 22 which is intended to conduct liquefied gas from the gaseous head towards the interior space 18 of the collecting pipe 2. The pipe 22 has a first end 23 which is located in the internal space 3 of the tank 1, outside the collecting pipe 2. The first end 23 opens into the internal space 3 of the tank 1 at a height h1 which is greater than the height h of the lower end 15 of the collecting pipe 2 and which is also greater than the maximum filling level hmax of the tank 1. Furthermore, the pipe 22 has a second end 24 which opens into the interior space 18 of the collecting pipe 2 to a height h2. The height h2 is greater than the height h of the lower end 15 of the collector pipe 2 and greater than the maximum filling level hmax.

Thus, the first and the second ends 23, 24 of the pipe 22 are located above the maximum filling level hmax of the tank 1 while the lower end 15 of the collecting pipe 2 is located below that here, which makes it possible to ensure fluid communication between the gas overhead of the tank 1 and the interior space 18 of the collecting pipe 2, even if the lower end 15 of the collecting pipe 2 is immersed in the liquid phase liquefied gas.

The pipe 22 further comprises a diverted section 25 which passes below the lower end 15 of the collecting pipe 2 in order to connect the first end 23 and the second end 24 of the collecting pipe 2. In the embodiment shown, the diverted section 25 has a U-shape which allows said pipe 22 to pass below the lower end 15 of the collecting pipe 2 so as to connect the first and second ends 23, 24 of the pipe 22 without having to cross the portion of the collecting pipe 2 which protrudes into the internal space 3 of the tank 1. The lower portion of the diverted section 25 is arranged at a height h3 from the bottom wall 9 of the tank 1.

As shown in Figure 1, when the tank 1 is loaded with liquefied gas up to its maximum loading level hmax so that the lower end 15 of the collecting pipe 2 is immersed in the liquid phase of the liquefied gas , the diverted section 25 of the pipe 22 is then filled with liquefied gas in the liquid phase. However, the liquefied gas in the liquid state which is contained in the diverted section 25 of the pipe 22 is capable of being driven out, provided that the pressure difference between the gas overhead and the interior space 18 of the collecting pipe 2 is sufficient.

Advantageously, in order to ensure that, under normal navigation conditions, the pressure of the gas overhead never reaches the maximum pressure Pdesign that the tank 1 is likely to withstand, account is taken of the additional overpressure required to expel the liquefied gas in the liquid state from the pipe 22 to size the geometry of the pipe 22 and the threshold pressure Ps of the safety valve 19.

Depending on the geometry of the pipe 22, the dimensioning of the threshold pressure Ps depends either on the length I of the pipe 22 which is capable of being filled with liquefied gas, when the tank 1 is loaded with liquefied gas up to its maximum loading level hmax, i.e. the height difference h2-h3. Note that, in the embodiment of Figure 1, the length I corresponds substantially to the length of the diverted portion of the pipe 22 which is located below the maximum loading level hmax, advantageously the length I corresponds to the length of the diverted portion of the pipe 22 which is located below the maximum loading level hmax.

In the example chosen to represent the invention, the pipe 22 has a U-shape with a central portion extending linearly; the two opposite ends being extended by two distal portions. When the vessel does not undergo any inclination, due to pitching or the phenomenon of rolling, the central portion of the pipe 22 extends horizontally while the two distal portions extend vertically. Thus, the sizing of the threshold pressure Ps is carried out according to two scenarios taking into account the height of the pipe 22, that is to say the length of each distal portion under the maximum loading level hmax, and of the length of the central portion of this pipe 22; the length I corresponding here to the sum of the lengths of the central portion and of the two distal portions under the maximum loading level hmax. The length of the central portion of the pipe 22 makes it possible in particular to take into account the phenomena of the ship's rolling or pitching, and therefore the inclination of the liquefied gas, LPG / LNG or others, contained in the tank. Of course, all other shapes of the pipe 22, for example in which the central portion and the distal portions do not extend linearly, would not modify the function of this pipe 22 and its relation to the sizing of the threshold pressure. Ps.

According to a first embodiment, the length I of the pipe 22 which is capable of being filled with liquefied gas, when the tank 1 is loaded with liquefied gas up to its maximum loading level hmax, is greater than the height difference h2-h3. In this case, the threshold pressure Ps of the safety valve 19 responds to the following inequality:

Ps <Pdesign - f * g ^* (h2 - h3); with

Ps: the threshold pressure of the safety valve 19;

Pdesign: the maximum design pressure for which tank 1 has been sized; f: the density of the liquefied gas intended to be stored in the tank 1; g: the normal acceleration of gravity; h2: the height of the second end 24 of the pipe 22; and h3: the height of the lowest point of pipe 22.

[0064] Advantageously, in order not to under-dimension the threshold pressure Ps of the safety valve 19 and to lose a capacity to increase the pressure of the tank 1, the threshold pressure Ps also responds to the following inequality:

Ps> Pdesign - f * g * (h2 - h3) - k; with k between 50 and 20,000 Pa, advantageously between 100 and 1000 Pa, preferably of the order of 100 Pa.

According to a second embodiment, the length I of the pipe 22 which is capable of being filled with liquefied gas, when the tank 1 is charged with liquefied gas up to its maximum loading level hmax, is less than the height difference h2-h3. In this case, the threshold pressure Ps of the safety valve 19 corresponds to the following inequality: Ps <Pdesign - f * g * I.

Advantageously, in order not to under-dimension the threshold pressure Ps, it also responds to the following inequality:

Ps> Pdesign - f * g * I - k; with k between 50 and 20,000 Pa, advantageously between 100 and 1000 Pa, preferably of the order of 100 Pa.

[0067] In relation to FIG. 4, another embodiment of the invention is described below. In this embodiment, the vessel 1 comprises at least two pipes 22, 26 which are each intended to conduct liquefied gas in the vapor phase from a zone of the gas overhead towards the interior space 18 of the collecting pipe 2.

The second pipe 26 comprises:

- a first end 27 which is located in the internal space 3 of the tank 1, outside the collecting pipe 2 and opens at a height h'1 which is greater than the height h and greater than hmax;

- a second end 28 which opens into the interior space 18 of the collecting pipe 2 at a height h'2 which is greater than h and hmax; and

- a diverted section 29 which passes below the lower end 15 of the pipe manifold 2 in order to connect the first end 27 and the second end 28 of the second pipe 26.

The first ends 23, 27 of the pipes 22, 26 open inside the tank 1 in two areas of the internal space 3 of the tank 1 which are located on either side of a longitudinal plane median P which is vertical, parallel to the longitudinal direction of the ship and passes through the center of gravity of the ship. Advantageously, the two zones of the internal space 3 of the tank 1 are located near two ends of the upper wall 10, opposite to each other in a transverse direction perpendicular to the longitudinal direction of the vessel. Thus, if the ship is immobilized in an inclined position in which it has a heeling inclination, at least one of the two pipes 22, 26 opens at the level of the highest point of the tank 1 and is thus able to evacuate the vapor phase of the cryogenic fluid stored in tank 1.

Furthermore, advantageously, the first ends 23, 27 of the two pipes 22, 26 are located near the median transverse plane which is orthogonal to the longitudinal direction of the ship, that is to say that they are located at a distance from one of the transverse walls 14 of the tank 1 of between 30 and 70% of the dimension of the tank 1 in the longitudinal direction of the vessel. This makes it possible to limit the risks that the first ends 23, 27 of the pipes 22, 26 are immersed in the liquid phase of the liquefied gas when the ship is immobilized in an inclined position in which it presents a trim inclination.

In relation to Figures 5 and 6, there is shown an anchoring zone of a pipe 22 on the upper wall 10 according to two embodiments. In these two embodiments, in order to limit the stresses on the waterproof primary membrane 8 which would be due to the anchoring of the pipe or pipes 22, they are anchored on metal anchoring plates 30, 31, 32 which are directly attached to the insulating panels of the primary thermally insulating barrier 7 and onto which are sealed sheets 33, 34, 35, 36, 37 of the primary waterproof membrane 8.

Figure 5 illustrates, in dotted lines, the position of metal anchoring plates 30, 31 which are fixed to the insulating panels of the primary thermally insulating barrier 7. The metal anchoring plates 30 are arranged in two directions orthogonal to each other. The metal sheets 33, 34, 35, 36 of the waterproof primary membrane 8 are welded to each other overlapping along the metal anchoring plates 30. In addition, the edge of the metal sheets 33, 34, 35, 36 which is covered by the edge of an adjacent metal sheet is fixed by welding on one of the metal anchoring plates 30. The areas of angles of the metal sheets 33, 34, 35, 36 are cut so that at the intersection between four adjacent metal sheets 33, 34, 35, 36, an area of one of the metal anchor plates 30 is not covered by any of the four metal sheets 33, 34, 35 , 36 adjacent. Advantageously, this uncovered zone forms an anchoring zone 38 for a pipe 22.

In Figure 6, a metal anchoring plate 32, shown in dotted lines, is covered by a metal sheet 37 of the waterproof primary membrane 8. The metal sheet 37 has an orifice 39. The metal sheet 37 is welded in a sealed manner, to the metal anchoring plate 32, all around said orifice. The zone of the metal anchoring plate 32 which is arranged opposite the orifice 39 of the metal sheet 37 can thus constitute an anchoring zone 40 for a pipe 22. According to an alternative embodiment, the zone of Anchoring 40 of the pipe can be made on a metal sheet 37 provided that this anchoring zone is in line with the anchoring of the metal sheet 37 on the metal anchoring plate 32.

[0074] Figure 7 illustrates means for anchoring the pipe 22 to the upper wall 10 according to one embodiment. In this embodiment, the anchoring means comprise a collar 41 through which the pipe 22 passes. The collar 41 is fixed to an anchoring zone, as described above in relation to FIGS. 5 and 6. According to FIGS. one embodiment, the pipe 22 is slidably mounted inside the collar 41 so as to allow the pipe 22 to contract or expand freely under the effect of the temperature differences.

According to another embodiment, not shown, the pipe 22 comprises one or more compensation devices allowing to give it flexibility in the longitudinal direction so as to allow its contraction and expansion. The compensation device can in particular be produced by bellows or by a compensation lyre.

Referring to Figure 8, a cutaway view of an LNG carrier 170 shows a sealed and insulated tank 171 of generally prismatic shape mounted in the double hull 172 of the ship. The wall of the vessel 171 comprises a primary membrane intended to be in contact with the LNG contained in the vessel, a secondary membrane arranged between the primary membrane and the double hull 172 of the vessel, and two thermally insulating barriers arranged respectively between the primary membrane and the secondary membrane and between the secondary membrane and the double shell 172.

In a manner known per se, the loading / unloading pipes 173 arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a maritime or port terminal for transferring a cargo of LNG from or to the tank 171. FIG. 8 also represents an example of a marine terminal comprising a loading and unloading station 175, an underwater pipe 176 and an installation on land 177. The loading and unloading station 175 is an off-station fixed installation. shore comprising a movable arm 174 and a tower 178 which supports the movable arm 174. The movable arm 174 carries a bundle of insulated flexible pipes 179 which can be connected to the loading / unloading pipes 173. The movable arm 174 can be swiveled and adapts to all LNG carrier templates. A connecting pipe, not shown, extends inside the tower 178. The loading and unloading station 175 allows the loading and unloading of the LNG carrier 170 from or to the onshore installation 177. The latter includes liquefied gas storage tanks 180 and connecting pipes 181 connected by the underwater pipe 176 to the loading or unloading station 175. The underwater pipe 176 allows the transfer of the liquefied gas between the loading or unloading station 175 and the shore installation 177 over a long distance, for example 5 km, which makes it possible to keep the LNG carrier 170 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 170 and / or pumps fitted to the shore installation 177 and / or pumps fitted to the loading and unloading station are used. 175.

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

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

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

Claims

[Claim 1] Tight and thermally insulating tank (1) for the storage of a liquefied gas, said tank (1) comprising:

- a plurality of walls defining an internal space (3) intended for the storage of the liquefied gas, the plurality of walls comprising an upper wall (10); and

- a collecting pipe (2) intended to extract, from the internal space (3) of the tank (1), liquefied gas in the vapor phase, said collecting pipe (2) passing through the upper wall (10), and comprising a lower end (15) which opens into the internal space (3) and which projects downwards, beyond the upper wall (10), to a height h; and

- at least a first pipe (22) intended to conduct liquefied gas in vapor phase from the internal space (3) of the tank (1) to the collecting pipe (2), said first pipe (22) comprising a first and a second end (23, 24), the first end (23) being located in the internal space (3) of the tank (1), outside the collecting pipe (2), and opening into said internal space (3) at a height h1 greater than h, the second end (24) opening inside the collecting pipe (2) at a height h2 greater than h, the first pipe (22) further comprising a diverted section ( 25) which passes below the lower end (15) of the header pipe (2) in order to connect the first and the second ends (23, 24) of the first pipe (22), the header pipe (2) being connected to a safety valve (19) which is configured to extract liquefied gas in the vapor phase from the header pipe (2) when the pressure in space inside (18) of the manifold (2) is greater than a threshold pressure Ps, and in which the threshold pressure Ps satisfies the following inequality:

Ps <Pdesign - f * g * min; with:

P design: the maximum design pressure for which the tank (1) was dimensioned; f: the density of the liquefied gas intended to be stored in the tank (1); g: the normal acceleration of terrestrial gravity min: the smallest value among (h2 - h3) and I; h2: the height of the second end of the first pipe (22); and h3: a height of the lowest point of the first pipe (22); I: a length of the first pipe (22) which is capable of being filled with liquefied gas, when the tank (1) is charged with liquefied gas up to a maximum loading level hmax.

[Claim 2] Tank (1) according to claim 1, in which the diverted section (25) is U-shaped.

[Claim 3] Tank (1) according to claim 1 or 2, wherein the height h is less than a maximum loading level hmax and the heights h1 and h2 are greater than the maximum loading level hmax.

[Claim 4] A vessel (1) according to any one of claims 1 to 3, wherein the threshold pressure Ps further satisfies the following inequality:

Ps> Pdesign - f ^* g ^* min - k; with k between 100 and 1000 Pa.

[Claim 5] Tank (1) according to any one of claims 1 to 4, in which the upper wall (10) comprises a sealed primary membrane (8) intended to be in contact with the liquefied gas stored in the tank (1 ), the waterproof primary membrane (8) having corrugations projecting towards the inside of the tank (1) and in which the collecting pipe (2) projects inside the internal space (3), at- beyond the corrugations of the waterproof primary membrane (8).

[Claim 6] Tank (1) according to any one of claims 1 to 5, in which the collecting pipe (2) projects inside the internal space (3), beyond the upper wall ( 10), with a vertical distance greater than 80 mm.

[Claim 7] Tank (1) according to any one of claims 1 to 6, wherein the tank (1) comprises one or more lines for loading and / or unloading from the tank (1) which pass to the inside the collector pipe (2).

[Claim 8] Tank (1) according to any one of claims 1 to 7, in which the upper wall (10) comprises at least one primary thermally insulating barrier (7) and a waterproof primary membrane (8) retained at the barrier. primary thermally insulating barrier, the upper wall (10) comprising metal anchor plates (30, 31, 32) which are fixed to the primary thermally insulating barrier (7) and to which are welded sealingly metal sheets (33, 34, 35, 36, 37) of the waterproof primary membrane (8), the first pipe (22) being anchored in an anchoring zone (38, 40) formed on one metal anchoring plates (30, 31, 32) or provided on a portion of the waterproof primary membrane (8) which is anchored to one of the metal anchoring plates (30, 31, 32).

[Claim 9] Tank (1) according to any one of claims 1 to 8, wherein the tank (1) comprises a second pipe (26) for conducting liquefied gas in the vapor phase of the internal space (3). from the tank (1) to the collecting pipe (2), said second pipe (26) having first and second ends (27, 28), the first end (27) being located in the internal space (3) of the tank (1), outside the collecting pipe (2), and opening into said internal space (3) at a height h'1 greater than h, the second end (28) opening inside the collector pipe (2) at a height h'2 greater than h.

[Claim 10] Tank (1) according to claim 9, wherein the first end (23) of the first pipe (22) and the first end (27) of the second pipe (26) are disposed on either side of a median longitudinal vertical plane of the tank (1).

[Claim 11] A vessel (170) for transporting a fluid, the vessel comprising a double hull (172) and a tank (171) according to any one of claims 1 to 10, arranged in the double hull.

[Claim 12] A transfer system for a fluid, the system comprising a vessel (170) according to claim 11, insulated pipes (173, 179, 176, 181) arranged to connect to the vessel (171) installed in the hull from the ship to a floating or onshore storage facility (177) and a pump for driving a flow of fluid through insulated pipelines from or to the floating or onshore storage facility to or from the vessel's vessel.

[Claim 13] A method of loading or unloading a ship (170) according to claim 13, wherein a fluid is conveyed through insulated pipelines (173, 179, 176, 181) from or to a floating storage facility or land (177) to or from the vessel (171).