KR20220062405A - airtight insulated tank - Google Patents

Abstract

The present invention relates to a sealed and insulated tank (1) for storing liquefied gas, said tank (1) comprising:
- a plurality of walls defining an interior space (3) intended for storing liquefied gas, the plurality of walls comprising an upper wall (10); And
a collection line (2) intended to extract vapor phase liquefied gas, said collection line projecting downward beyond the upper wall (10);
- at least one first pipe ( 22 ) for conveying liquefied gas in vapor phase from the interior space ( 3 ) of the tank ( 1 ) to the collection line ( 2 ), the first pipe ( 22 ) having a bypass section ( 25 ) first It extends below the bottom end 15 of the collection line 2 for connecting the first and second ends 23 , 24 of the pipe 22 .

Description

airtight insulated tank

The present invention relates to a hermetically insulated tank for storing and/or transporting liquefied gas. The tank transports, for example, LPG (Liquefied petroleum gas) having a temperature of -50 °C to 0 °C, or LNG (Liquefied natural gas) at about -162 °C at atmospheric pressure.

These tanks can be installed on land or on floating structures. In the case of floating structures the tank may be intended to transport the liquefied gas or to contain the liquefied gas serving as fuel for propelling the floating structure.

Document WO2013093261 discloses a hermetically insulated tank for storing liquefied gas in liquid-vapor equilibrium. Due to the heat transfer phenomenon between the inside and outside of the tank, the liquefied gas stored in the tank absorbs heat and causes evaporation. The tank is therefore equipped with a collection line for extracting the vapors through the walls of the tank and from the ceiling of the tank filled with gas. A collection line opens on the inside of the tank to form a passage between the interior space of the tank and the vapor collector, the vapor collector being disposed outside of the tank and connected with the collection line, for example via a degassing mast. The collection line is connected to the vapor collector through a calibrated safety valve to evacuate vapor phase gases from the tank when the vapor pressure of the tank's gas-filled ceiling is above the critical pressure. This makes it possible to control the pressure inside the tank to avoid overpressure which could possibly damage the tank.

The wall of the sealed tank consists of a multi-layered structure, that is, continuously from the outside of the tank to the inside, a secondary insulating barrier, a secondary sealing membrane, a primary insulating barrier and a primary sealing membrane. To ensure continuity of the primary sealing membrane around the collection line, the end has an L-shaped cross-section and is rigidly connected to the primary sealing membrane via a collar that protrudes into the interior space of the tank. The bottom end of the collection line thus projects beyond the primary sealing membrane into the interior space of the tank.

For safety reasons, it is important to ensure that the gas-filled ceiling of the tank remains connected to the inside of the collection line when the tank is filled to its maximum water level. At this time, in order to prevent the lower end of the collection line from being submerged in the liquid phase of the liquefied gas, the gas existing in the upper part of the tank interior space is prevented from being extracted by the collection line, so the maximum loading level of the tank is likely to be reduced, which is completely not satisfied

This drawback is also particularly significant when the height of the collar is large or the interior space of the tank is low in order to give greater flexibility to the connection between the primary hermetic membrane and the collection line.

One idea on which the present invention is based is a tank equipped with a collection line for collecting vapor from gas filled in the tank ceiling and the space inside the tank while the collection line penetrates the ceiling wall of the tank and extracts the vapor through the collection line. The point is that the optimum liquefied gas can be collected irrespective of the vertical dimension of the portion of the vapor collection line protruding from the

According to one embodiment, the present invention provides a hermetically insulated tank for storing liquefied gas, said tank comprising:

- a plurality of walls defining an interior space intended to store liquefied gas, said plurality of walls comprising an upper wall; and

- a collection line intended to extract vapor phase liquefied gas from the interior space of the tank, said collection line passing through an upper wall and having a bottom end which is open in the interior space and protrudes downwardly beyond the upper wall to a height h a collection line comprising; and

- at least one first pipe intended to convey vapor phase liquefied gas to a collection line in the interior space of the tank, said first pipe comprising first and second ends, the first end being external to the collection line and located in the interior space of the tank, open in the interior space at a height h1 greater than h, a second end opening in the interior space of the collection line at a height h2 greater than h, wherein the first pipe and at least one first pipe having a diverted section extending below a bottom end of the collection line to connect the first and second ends of the pipe.

Thus, the first pipe ensures a fluid connection between the gas-filled ceiling and the interior space of the collection line even when the bottom end of the collection line is submerged in the liquid phase of the liquefied gas.

According to embodiments, such tanks may include one or more of the following features.

According to one embodiment, the bypass section has a U-shape.

According to one embodiment, the height h is lower than the maximum shipping level hmax. The pipe can thus fill the tank above the bottom end of the collection line while allowing vapor to be extracted from the gas-filled ceiling in case of overpressure.

According to one embodiment, the height h1 is higher than the maximum shipping level hmax.

According to one embodiment, the height h2 is higher than the maximum shipping level hmax.

According to an embodiment, the collection line is connected to a safety valve configured to extract vapor phase liquefied gas from the collection line when the pressure in the interior space of the collection line is above a critical pressure Ps.

According to one embodiment, the critical pressure Ps satisfies the following inequality:

Ps < P design - φ* g * min

min: the smallest of (h2 - h3) and l.

According to one embodiment, the critical pressure Ps satisfies the following inequality:

Ps < P design - φ* g * min

P design: The maximum design pressure at which the tank is dimensioned.

φ : Density of liquefied gas stored in the tank

g: vertical acceleration of earth's gravity;

h2: the height of the second end of the first pipe and

h3: the height of the lowest point of the first pipe.

According to one embodiment, the critical pressure Ps further satisfies the following inequality:

Ps > Pdesign - φ * g * (h2 - h3) - k;

k is between 100 and 1000 Pa.

According to another embodiment, the critical pressure Ps satisfies the following inequality:

Ps < Pdesign - φ* g * l

P design: Maximum design pressure for a dimensioned tank.

φ: density of liquefied gas stored in the tank

g: vertical acceleration of earth's gravity; And

l: Length of the first pipe that can be filled with liquefied gas when the tank is filled with liquefied gas to the maximum loading level (hmax).

According to one embodiment, the critical pressure Ps further satisfies the following inequality:

Ps > Pdesign - φ * g * l - k;

k is between 100 and 1000 Pa.

According to one embodiment, the upper wall comprises a primary sealing membrane intended for contact with the liquefied gas stored in the tank, said primary sealing membrane passing through a corrugation protruding toward the interior of the tank and the primary sealing membrane to the tank Includes a collection line protruding into the interior of the

According to one embodiment, the collection line projects beyond the upper wall and into the interior space by a vertical distance of greater than 80 mm, preferably greater than 100 mm, for example on the order of approximately 150 mm.

According to one embodiment, the tank comprises one or more lines intended for loading and/or unloading of the tank running inside the collection line. Therefore, the collection line can form both a gas dome structure and a liquid dome structure, thereby simplifying the tank construction and reducing the cost.

According to one embodiment, the upper wall comprises at least one primary thermal insulation barrier and a primary hermetic membrane fixed to the primary thermal insulation barrier, the upper wall having a metal anchorage fixed on the primary thermal insulation barrier and fixed to a metal sheet including plate. A portion of the primary hermetic membrane is tightly welded, and the first pipe is formed in a portion of the primary hermetic membrane fixed to one of the metal fixing plates or fixed to a fixing section formed on one of the metal fixing plates. Thereby, it is possible to prevent tearing of the primary sealing membrane.

According to one embodiment, the tank comprises a second pipe intended to deliver vapor phase liquefied gas from the interior space of the tank to the collection line, said second pipe comprising first and second ends, said first The end is disposed in the inner space of the tank outside the collection line, and is open in the inner space at a height greater than h (h'1), and the second end is disposed inside the collection line at a height (h'2) greater than h. open at the opening.

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 central 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 proximate to two ends of the upper wall opposite to each other in the transverse direction orthogonal to the longitudinal direction of the vessel.

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

According to one embodiment, the upper wall covers the interior space.

Such tanks may form part of, for example, onshore storage facilities for the storage of LNG or may be used in floating, offshore or deep-sea structures, in particular methane tankers, Floating Storage and Regasification Units (FSRUs), Floating Production and Storage Offshore Units ( FPSO: Floating Production and Storage Offshore Unit).

According to one embodiment, the present invention provides a ship for transporting a fluid, said ship comprising a double hull and said tank arranged in said double hull.

According to one embodiment, the present invention also provides a method for loading or unloading such a vessel, wherein the fluid is conveyed via an insulated pipeline from a floating or onshore storage facility to a tank of the vessel and vice versa.

According to one embodiment, the present invention also provides a conveying system for a fluid, said system comprising an insulated pipeline and an insulated pipe arranged to connect the aforementioned vessel, a tank installed in the hull of the vessel to a floating or onshore storage facility. and pumps that move fluid through the line to a floating or onshore storage facility or to or from a tank on a ship.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood from the following description of several specific embodiments of the invention, given in an illustrative and non-limiting manner only, with reference to the accompanying drawings, wherein other objects, details, features and advantages become more apparent will be done

1 is a cross-sectional view of a closed insulated tank equipped with a collection line and a pipe for transporting gas filled in the ceiling portion of the tank to the interior space of the collection line.
FIG. 2 is a front view showing in detail the collection line and piping of FIG. 1 .
3 is a bottom perspective view showing in detail the collection line and the pipe of FIG.
4 is a schematic cross-sectional view of a closed and insulated tank according to another embodiment;
5 is a schematic view of a primary sealing membrane section of an upper wall for fastening of a pipe, according to a first embodiment;
6 is a schematic view of a primary sealing membrane section of an upper wall intended for fastening of a pipe, according to a second embodiment;
7 shows means for fastening a pipe to an upper wall according to an embodiment;
8 is a schematic cross-sectional view of a ship including a liquefied natural gas storage tank and a terminal for unloading the tank.

1 , a closed and insulated tank 1 is observed equipped with a collection line 2 intended to extract vapor phase liquefied gas from the interior space of the tank. The tank 1 is for storing a liquefied gas selected, for example, from liquefied natural gas (LNG) and liquefied petroleum gas (LPG).

The tank 1 is arranged inside a support structure 4 which may be formed, for example, by the double hull of a ship, but more generally by any type of rigid partition having suitable mechanical properties.

Tank 1 is preferably a tank with a membrane. The tank 1 has a plurality of walls defining an interior space 3 for storage of liquefied gas. Each wall has a multi-layered structure and is supported by a secondary insulating barrier 5, a secondary insulating barrier 5 supported against the supporting structure 4 in the thickness direction of the wall from the outside to the inside of the tank 1 A hermetic membrane (6), a primary insulating barrier (7) supported by a secondary hermetic membrane (6) and a primary hermetic membrane (8) in contact with the liquefied gas stored in the tank and supported by a primary insulating barrier (7) ) is included. According to an alternative embodiment, each wall comprises only a primary hermetic membrane 8 and a primary insulating barrier 7 supported by a supporting structure 4 .

According to one embodiment of the invention, the primary hermetic membrane 8 is a pleated membrane. Accordingly, the primary sealing membrane 8 comprises a plurality of metal sheets comprising corrugations protruding toward the inner space 3 of the tank 1 , so that the primary sealing membrane 8 is stored in the tank 1 . It is subject to deformation under the influence of thermal and mechanical stresses generated by the liquefied gas. Such a tank 1 is for example of the Mark III® type as described in patent application FR2691520. For example, tank 1 may be of type NO96 ® as described in patent application FR2877638.

As shown in FIG. 1 , the tank 1 has a bottom wall 9 , an upper wall 10 opposite the bottom wall 9 , a side wall 11 connecting the bottom wall 9 and the upper wall 10 , 12 , 13 ) and a transverse wall 14 connecting the bottom wall 9 and the top wall 10 . In the embodiment shown, the tank 1 has a cross section in the form of an octagon in cross section on the cross section. Accordingly, the tank 1 has a vertical sidewall 11 and inclined sidewalls 12 and 13 connecting one of the vertical sidewalls 11 to the floor wall 9 or the ceiling wall 10 respectively.

The tank 1 is a collection line intended to extract liquefied gas vapor contained in the ceiling filled with gas, that is, liquefied gas vapor contained in the upper part of the internal space 3 of the tank 1 in which the liquefied gas is in a gaseous state. (2) is included. The collection line 2 passes through the ceiling wall 10 of the tank 1 . The collection line 2 opens into the interior space 3 of the tank 1 and has an open bottom end 15 which projects downward beyond the ceiling wall 10 . The bottom end 15 of the collection line 2 is located at a height h relative to the bottom wall 9 of the tank 1 . The height h is lower than the maximum loading level hmax of the tank 1 so that when the liquefied gas is loaded into the tank 1 up to the maximum loading level hmax, the bottom end 15 of the collection line 2 immersed in the liquid of The upper end 16 of the collection line 2 is tightly closed by a cover 17 .

The interior space 18 of the collection line 2 is connected to a vapor collector, not shown, via at least one line equipped with a safety valve 19 . The safety valve 19 is calibrated (calibrated) to ensure the release of gaseous gas when the pressure in the inner space 18 of the collection line 2 exceeds the critical pressure Ps. The collection line 2 thus aims to extract vapors from the gas-filled ceiling in case of overpressure and thus can control the pressure of the gas-filled ceiling to prevent overpressure that could damage the tank 1 . For example, the vapor collector transports the extracted vapor to a degassing mast, burner, ship's propulsion unit, or a liquefaction unit where the vapor gas is re-liquefied and then reintroduced into the tank in liquid state. In the embodiment shown, the interior space 18 of the collection line 2 is connected to the steam collector via two safety valves 19 , which provides a level of redundancy that makes it possible to improve the reliability of steam extraction. to secure

The collection line 2 is tightly connected to the primary sealing membrane 8 to ensure continuity of the seal. For this purpose, the collection line 2 is connected to the primary sealing membrane 8 via a collar 20 having an L-shaped cross-section. The collar 20 includes a cylindrical portion in a vertical orientation and an annular flange in a horizontal orientation. The cylindrical part is wound tightly around the collection line 2 . The annular flange protrudes horizontally from the top of the cylindrical part and is tightly welded to the primary sealing membrane 8 . This collar 20 makes it possible to impart flexibility to the connection of the collection line 2 and the primary hermetic membrane 8 , which makes it possible to absorb thermal and dynamic stresses.

Preferably, as shown in FIG. 1 , the tank 1 is operated inside the collection line 2 and is intended for loading and/or unloading of the tank 1 completely passing through its cover 17 . The above line 21 is included. A line 21 for ensuring unloading of the tank 1 extends to the immediate vicinity of the lower wall 9 . At the lower end of the line 21, an unloading pump not shown in FIG. 1 is mounted.

According to an embodiment not shown, the lines intended for loading and/or unloading are formed by vertical masts of the loading/unloading risers. The loading/unloading riser comprises, for example, a tripod structure, ie three vertical masts held together by crossmembers. Each mast is hollow and passes through a cover 17 of the collection line 2 . Therefore, each mast has a loading line for loading liquefied gas into tank 1, an unloading line for unloading liquefied gas from tank 1, or a backup pump and unloading in case the unloading pump fails. Form a relief well that allows the line.

Thus, in the embodiment described above, the collection line 2 forms both a gas dome structure and a liquid dome structure. That is, the pressure management function of the ceiling filled with gas and the function of loading and/or unloading liquefied gas into the tank 1 are ensured by a single structure, thereby simplifying the configuration of the tank, and reducing the cost by limiting the number of specific structures. can be reduced However, on the other hand, if the collection line 2 is used for the passage of at least one loading and/or unloading line 21 , it has a larger diameter and is sufficient for the link between the collection line 2 and the hermetic membrane. The axial dimension of the collar 20 and the partial dimension of the collecting line 2 projecting on the inside of the tank 1 are increased to give flexibility.

2 and 3, when the primary sealing membrane 8 is a pleated membrane including pleats protruding toward the inner space 3 of the tank 1, the collection line 2 It protrudes from the inside of the inner space 3 of the tank 1 toward the bottom.

According to one embodiment, the collection line 2 projects more than 80 mm, preferably more than 100 mm, for example 150 mm into the tank 1 with respect to the primary sealing membrane 8 of the upper wall 10 . .

The tank 1 is also equipped with a pipe 22 for conveying the liquefied gas from the gas-filled ceiling to the interior space 18 of the collection line 2 . The pipe 22 comprises a first end 23 located in the interior space 3 of the tank 1 outside the collection line 2 . The first end 23 has an inner space ( 3) is opened. The pipe 22 also comprises a second end 24 which opens into the interior space 18 of the collection line 2 at a height h2 . The height h2 is higher than the height h of the bottom end 15 of the collection line 2 and higher than the maximum shipping level hmax.

Accordingly, the first and second ends 23 , 24 of the pipe 22 are located above the maximum loading level hmax of the tank 1 while the bottom end 15 of the collection line 2 is located below it. This ensures a fluid connection between the gas-filled ceiling of the tank 1 and the interior space 18 of the collection line 2, even if the bottom end 15 of the collection line 2 is immersed in the liquid phase of the liquefied gas. can do.

The pipe 22 further comprises a bypass section 25 running under the bottom end 15 of the collection line 2 for connecting the first end 23 and the second end 24 of the collection line 2 . do. In the embodiment shown, the bypass section 25 is a bottom end 15 of the collection line 2 to connect the first and second ends 23 , 24 of the pipe 22 without the need for a pipe 22 . It has a U-shape that allows it to flow downwards. The pipe 22 therefore does not pass through the portion of the collection line 2 that protrudes into the inner space 3 of the tank 1 . The lowest part of the bypass section 25 is arranged at a height h3 from the bottom wall 9 of the tank 1 .

1, when the tank 1 is filled with liquefied gas to the maximum loading level hmax so that the bottom end 15 of the collection line 2 is submerged in the liquid phase of the liquefied gas, the bypass of the pipe 22 Section 25 is filled with liquid liquefied gas. However, if the pressure difference between the gas-filled ceiling and the inner space 18 of the collection line 2 is sufficient, the liquid liquefied gas contained in the bypass section 25 of the pipe 22 can be discharged.

Preferably, the geometry of the pipe 22 and the safety valve 19 are arranged so that, under normal operating conditions, the gas-filled ceiling pressure never reaches the maximum pressure Pdesign that the tank 1 can withstand. When measuring the critical pressure (Ps), the additional overpressure required to expel the liquefied gas in liquid state from the tank is taken into account.

Depending on the geometry of the pipe 22 , the magnitude of the critical pressure Ps is the probability of filling or filling the tank 1 with liquefied gas up to the maximum loading level hmax or the height difference h2-h3. It depends on the length l of the pipe 22 with the teeth. 1 , the length l corresponds substantially to the length of the diverted portion of the pipe 22 located below the maximum loading level hmax, preferably the length l is the maximum loading level hmax ) corresponds to the length of the bypassed part of the pipe 22 located below.

In the example chosen to illustrate the present invention, the pipe 22 has a U-shape with a central portion extending linearly; The two opposite ends are extended by the two distal ends. When the tank is not inclined, the central portion of the pipe 22 extends horizontally and the two end portions extend vertically due to the pitch or roll phenomenon. The dimension of the critical pressure Ps is therefore measured according to two specific cases, taking into account the height of the pipe 22 taking into account the length of each end part under the maximum shipping level hmax and the length of the central part of the pipe 22. where length l corresponds to the sum of the lengths of the central part and the two end parts at the maximum loading level hmax. The length of the central portion of the pipe 22 makes it possible to take into account the roll or pitch phenomenon of the vessel and the tendency of liquefied gas, LPG/LNG or other gases. Obviously, any other shape of pipe 22 , for example where the central portion and distal portion do not extend linearly, does not modify the function of this pipe 22 and its relation to the dimension of the critical pressure Ps. won't

According to the first embodiment, the length l of the pipe 22 likely to be filled with liquefied gas when the tank 1 is loaded with liquefied gas to the maximum loading level hmax is greater than the height difference h2-h3 big. In this case, the critical pressure Ps of the safety valve 19 is confirmed by the following inequality.

Ps < Pdesign - φ* g * (h2 - h3);

Ps: critical pressure of safety valve 19;

P design: the maximum design pressure at which the tank (1) is dimensioned.

φ: density of liquefied gas stored in tank (1)

g: vertical acceleration of earth's gravity;

h2: the height of the second end 24 of the pipe 22; and

h3: the height of the lowest point of the pipe 22 .

Preferably, in order not to underestimate the critical pressure Ps of the safety valve 19 and not to lose the pressure-rising capacity of the tank 1, the critical pressure Ps is also determined by the following inequality.

Ps > Pdesign - φ * g * (h2 - h3) - k;

k is 50 to 20,000 Pa, preferably 100 to 1000 Pa, preferentially on the order of 100 Pa.

According to the second embodiment, when the tank 1 is loaded with liquefied gas to the maximum loading level hmax, the length l of the pipe 22 likely to be filled with liquefied gas is greater than the height difference h2-h3 small. In this case, the critical pressure Ps of the safety valve 19 is confirmed by the following inequality.

Ps < Pdesign - φ* g * l.

Preferably, in order not to underestimate the critical pressure Ps, the latter is also confirmed by the following inequality.

Ps > Pdesign - φ* g * l - k ;

k is 50 to 20,000 Pa, preferably 100 to 1000 Pa, preferentially on the order of 100 Pa.

Referring to Fig. 4, another embodiment of the present invention is described below. In this embodiment, the tank 1 comprises at least two pipes 22 , 26 which are each intended to convey liquefied gas in vapor phase from a region of the ceiling filled with gas to the interior space 18 of the collection line 2 . do.

The second pipe 26 includes:

- a first end 27 located in the interior space 3 of the tank 1 and located outside the collection line 2 and open at a height h'1 above the height h and above hmax;

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

- a bypass section 29 running under the bottom end 15 of the collection line 2 for connecting 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 zones of the internal space 3 of the tank 1 , which zones are parallel and perpendicular to the longitudinal direction of the vessel. and is located on both sides of the central longitudinal plane (P) passing through the ship's center of gravity. Preferably, the two sections of the interior space 3 of the tank 1 are located close to the two ends of the upper wall 10 and face each other in a transverse direction perpendicular to the longitudinal direction of the vessel. Thus, when the vessel is fixed in an inclined position indicating a wrist inclination, at least one of the two pipes 22 , 26 is opened at the highest point of the tank 1 and thus can discharge the cryogenic vapor phase stored in the tank. .

Furthermore, preferably, the first ends 23 , 27 of the two pipes 22 , 26 are located proximate to a central cross-section orthogonal to the longitudinal direction of the vessel. That is, the first ends 23 , 27 are located spaced apart from one of the transverse walls 14 of the tank 1 between 30-70% of the dimensions of the tank 1 in the longitudinal direction of the vessel. This makes it possible to limit the risk that the first ends 23 , 27 of the pipes 22 , 26 are immersed in the liquid phase of the liquefied gas when the vessel is fixed in an inclined position indicating a trim inclination.

5 and 6 , a zone for fixing the pipe 22 on the upper wall 10 is illustrated according to two embodiments. In these two embodiments, in order to limit the stress in the primary sealing membrane 8 due to the fastening of the pipe 22 , the pipe is fixed directly on the insulating panel of the primary insulating barrier 7 and the primary sealing membrane It is fixed on a metal fixing plate 30, 31, 32 which is rigidly welded to the seat 33, 34, 35, 36, 37 of (8).

FIG. 5 shows the positions of the metal fixing plates 30 and 31 fixed to the thermal insulation panel of the primary thermal insulation barrier 7 by dotted lines. The metal fixing plate 30 is disposed in two directions orthogonal to each other. The metal sheets 33 , 34 , 35 , 36 of the primary sealing membrane 8 are overlap welded to each other along the metal fixing plate 30 . Further, the edges of the metal plates 33 , 34 , 35 , 36 covered by the edges of the adjacent metal plates are fixed to one of the metal fixing plates 30 by welding. Corner regions of the metal sheets 33 , 34 , 35 , 36 are cut so that an area of one of the metal fixing plates 30 at the intersection between the four adjacent metal sheets 33 , 34 , 35 , 36 is no more than any four adjacent metal sheets 33 , 34 , 35 , 36 . The metal sheets 33, 34, 35 and 36 are also cut so as not to be covered. Preferably, this uncovered zone forms a fastening zone 38 for the pipe 22 .

In FIG. 6 , the metal fixing plate 32 indicated by dotted lines is covered with a metal sheet 37 of the primary hermetic membrane 8 . The metal sheet 37 includes an orifice 39 . A metal sheet 37 is firmly welded to the metal fixing plate 32 around the entire perimeter of the orifice. The section of the metal fastening plate 32 arranged opposite the orifice 39 of the metal sheet 37 can thus constitute a fastening section 40 for the pipe 22 . According to an alternative embodiment, the fastening section 40 of the pipe may be formed on the metal sheet 37 if this fastening section is in line with the fastening portion of the metal sheet 37 on the metal fastening plate 32 . . 7 shows means for fixing the pipe 22 to the upper wall 10 according to an embodiment. In this embodiment, the fastening means comprise a clamp 41 through which the pipe 22 passes. The clamp 41 is fixed in the fixing zone as described above with respect to FIGS. 5 and 6 . According to one embodiment, the pipe 22 is slidably mounted inside the clamp 41 so that the pipe 22 can freely contract or expand under the influence of a temperature difference.

According to another embodiment, not shown, the pipe 22 comprises one or more compensation devices which make it possible to provide flexibility in the longitudinal direction to allow for contraction and expansion. The compensating device can in particular be produced as a bellows or compensating loop.

Referring to FIG. 8 , a cross-sectional view of a methane tanker vessel 170 shows a generally prismatic, sealed, insulated tank 171 mounted to the double hull 172 of the vessel. The walls of the tank 171 have a primary hermetic membrane intended to come into contact with the LNG contained in the tank, a secondary hermetic membrane disposed between the primary hermetic membrane and the double hull 172 of the ship, and a primary hermetic membrane and 2 It consists of a primary sealing membrane, and two insulating barriers each disposed between the secondary sealing membrane and the double hull (172).

As is known per se, a loading/unloading pipeline 173 disposed on the upper deck of a vessel may be connected to a sea or port terminal by suitable connectors for transporting LNG cargo to or from tank 171 . can

8 also shows an example of an offshore terminal comprising an unloading station 175 , a subsea line 176 and an onshore facility 177 . The loading and unloading station 175 is a stationary offshore installation comprising a movable arm 174 and a riser 178 supporting the movable arm 174 . The movable arm 174 supports a bundle of insulated flexible pipe 179 that can be connected to a loading/unloading pipeline 173 . The directional movable arm 174 adapts to all methane tanker templates. Link lines not shown extend into riser 178 . A loading and unloading station 175 allows methane tankers 170 to be loaded and unloaded from or to an onshore facility 177 . It comprises a liquefied gas storage tank 180 and a link line 181 connected to a loading or unloading station 175 by a subsea line 176 . The subsea line 176 makes it possible to transport liquefied gas between the loading or unloading station 175 and the onshore facility 177 over long distances, for example 5 km, away from shore during loading and unloading operations. It makes it possible to maintain the methane tanker vessel 170 .

A pump mounted on the vessel 170 and/or a pump mounted on the shore facility 177 and/or a pump mounted on the loading and unloading station 175 is implemented to generate the pressure required for the transfer of the liquefied gas.

While the present invention has been described in connection with several specific embodiments, it is to be understood that it is not limited thereto, but encompasses all technical equivalents of the described means, and combinations thereof, provided they come within the context of the claimed subject matter of the invention.

The use of the verbs "to include" or "to include" and their conjugations do not exclude the presence of elements or steps other than those specified in a claim.

Reference signs between parentheses in the claims should not be construed as limiting the claims.

Reference signs between parentheses in the claims should not be construed as limiting the claims.

Claims (13)

A hermetically insulated tank (1) for storing liquefied gas, said tank (1) comprising:
- a plurality of walls defining an interior space (3) intended for storing liquefied gas, the plurality of walls comprising an upper wall (10); and
- a collection line (2) adapted to extract vapor phase liquefied gas from the interior space (3) of the tank (1), said collection line (2) passing through the upper wall (10), said collection interior space (3) a collection line (2) having a bottom end (15) which is open to and projects downwardly to a height (h) beyond the upper wall (10); and
- at least one first pipe (22) adapted to convey liquefied gas in vapor phase from the interior space (3) of the tank (1) to the collection line (2), said first pipe (22) having a first end (23) ) and a second end 24 , wherein the first end 23 is disposed outside the collection line 2 and is disposed in the interior space 3 of the tank 1 , the height h1 being higher than h ) into the interior space 3 , the second end 24 opening inside the collection line 2 at a height h2 higher than h, the first pipe 22 being the first pipe a bypass section (25) extending below a bottom end (15) of a collection line (2) for connecting a first end (23) and a second end (24) of (22), said collection line (2) ) is the liquefied gas from the collection line 2 into the vapor phase when the pressure in the internal space 18 of the collection line 2 is greater than the critical pressure Ps, and the critical pressure Ps satisfies the following inequality A hermetically insulated tank (1) comprising at least one first pipe (22) connected to a safety valve (19) adapted for extraction.
Ps < Pdesign - φ * g * min;
P design: the maximum design pressure dimensioned for the tank (1);
φ: density of liquefied gas to be stored in tank 1;
g: vertical acceleration of earth's gravity;
min: the smallest of (h2 - h3) and l;
h2: the height of the second end of the first pipe 22;
h3: the height of the lowest point of the first pipe 22;
l: Length of first pipe 22 which is likely to be filled with liquefied gas when loading liquefied gas into tank 1 up to the maximum loading level hmax. The hermetically insulated tank (1) according to claim 1, wherein the bypass section (25) has a U-shape. 3. Hermetically insulated tank (1) according to claim 1 or 2, wherein the height (h) is lower than the maximum shipping level (hmax) and the heights (h1, h2) are higher than the maximum shipping level (hmax). 4. The tank (1) according to any one of the preceding claims, wherein the critical pressure (Ps) further satisfies the following inequality.
Ps > Pdesign - φ * g * min - k;
k is a value between 100 and 1000 Pa. 5. A primary sealing membrane (8) according to any one of the preceding claims, wherein the upper wall (10) comprises a primary sealing membrane (8) intended for contact with the liquefied gas stored in the tank (1). ) has a corrugation protruding toward the inside of the tank 1 and the collection line 2 protrudes into the interior space 3 beyond the corrugation of the primary sealing membrane 8 , the hermetically insulated tank ( 1 ) . 6. Hermetically insulated tank (1) according to any one of the preceding claims, wherein the collection line (2) projects beyond the upper wall (10) into the interior space (3) by a vertical distance greater than 80 mm. . 7. Hermetically insulated according to any one of the preceding claims, wherein the tank (1) comprises one or more lines for loading and/or unloading of the tank (1) running inside the collection line (2). tank (1). 8. The upper wall (10) according to any one of the preceding claims, wherein the upper wall (10) comprises at least one primary insulating barrier (7) and a primary hermetic membrane (8) fixed to the primary insulating barrier,
The upper wall 10 is fixed to the primary insulating barrier 7 and metal fixing plates 30 , 31 to which the metal sheets 33 , 34 , 35 , 36 , 37 of the primary sealing membrane 8 are rigidly welded. , 32),
The first pipe 22 is a fastening formed in one of the metal fixing plates 30 , 31 , 32 or formed in a part of the primary hermetic membrane 8 fixed to one of the metal fixing plates 30 , 31 , 32 . A hermetically insulated tank (1), fixed in regions (38, 40). 9. A second pipe (26) according to any one of the preceding claims, wherein the tank (1) is adapted to convey the liquefied gas from the interior space (3) of the tank (1) in the vapor phase to the collection line (2). ), including
the second pipe (26) comprises a first end (27) and a second end (28);
said first end 27 is external to the collection line 2 but is arranged in the interior space 3 of the tank 1 and opens into the interior space 3 at a height h'1 higher than h,
The second end (28) opens to the collection line (2) at a height (h′2) higher than h. The hermetically insulated 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 arranged on either side of a central longitudinal vertical plane. ). A vessel (170) for transporting a fluid, comprising a double hull (172) and a tank (171) according to any one of claims 1 to 10 arranged in said double hull. A vessel (170) according to claim 11, an insulated pipeline (173, 179, 176, 181) configured to connect a tank (171) installed on the hull of the vessel to a floating or onshore storage facility (177) and the insulated pipe A fluid transport system comprising a pump for driving the flow of fluid through a line from a tank on a ship to a floating or onshore storage facility or from a floating or onshore storage facility to a tank on a ship. 14. A method of loading or unloading a vessel (170) according to claim 13, wherein the fluid is passed through an insulating pipeline (173, 179, 176, 181) to or from a floating or onshore storage facility (177) or from a tank (171) of the vessel. ) by way of transport, loading or unloading.

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