FR3149290A1 - Tower intended for loading and/or unloading a tank intended to contain a liquefied gas - Google Patents

Abstract

The invention relates to a tower (2) for loading and/or unloading a tank (1) intended to contain a liquefied gas, the tower comprising at least two hollow masts (11, 12, 13) which extend parallel in a longitudinal direction (D), the masts being connected by reinforcing structures (20, 25, 26), each reinforcing structure comprising at least one crosspiece (21) and extending perpendicular to said longitudinal direction, the reinforcing structures being distributed along the masts while being spaced apart by spacings (EN, EA) located between the adjacent reinforcing structures along the masts, the reinforcing structures being distributed such that the spacings comprise a plurality of normal spacings (EN) having a normal spacing distance (H1), and a number equal to one or two of adaptation spacings (EA) having an adaptation spacing distance (H2) different from said distance normal spacing. Figure for abstract: Fig. 2

Description

Tower intended for loading and/or unloading a tank intended to contain a liquefied gas

The invention relates to the field of storage and/or transport of liquefied gas and more particularly concerns a tower for loading and/or unloading liquefied gas into a tank intended for this use.

In particular, the invention relates to the field of sealed and thermally insulating tanks for storing and/or transporting liquefied gas at low temperature, such as tanks for transporting Liquefied Natural Gas (LNG) at approximately -162°C at atmospheric pressure, Liquid Hydrogen (LH ₂ ) at -253°C at atmospheric pressure, Ammonia (NH ₃ ) at -30°C at atmospheric pressure or Liquefied Petroleum Gas (also called LPG) having for example a temperature between -50°C and 0°C. These tanks can be installed on land or on a floating structure. In the case of a floating structure, the tank can be intended for transporting liquefied gas or for receiving liquefied gas used as fuel for the propulsion of the floating structure.

Technological background

In the state of the art, there are known sealed and thermally insulating tanks for storing liquefied natural gas (LNG) on board a ship and equipped with a tower for loading and/or unloading them. This tower extends vertically in the tank, between a bottom of this tank and a ceiling thereof.

The tower intended for loading and/or unloading comprises, for example, a tripod structure, i.e. it comprises three vertical masts which are fixed to each other by horizontal crosspieces distributed at regular intervals along the masts and diagonal crosspieces connecting the masts in pairs between the horizontal crosspieces. Each of the vertical masts is hollow. Two of the masts form a line for unloading the tank and are each associated with an unloading pump carried by the tower, near its lower end. The third mast forms an emergency well allowing the descent of an emergency pump and an unloading line in the event of failure of the other unloading pumps. The tower also carries loading lines which do not constitute one of the three masts.

The tower intended for loading and/or unloading the tank extends over the entire depth of the tank. However, tanks intended for the transport and/or storage of liquefied gas can have different sizes depending on the use for which they are intended. For example, LNG tanks intended to transport liquefied gas have larger dimensions than tanks in which liquefied gas is stored as fuel for the needs of the ship, in particular for its propulsion. In addition, there are different models of tank for each use with different dimensions, in particular different depths.

It is therefore necessary to adapt the height of the tower to the depth of the tank in which it is intended to be mounted.

For this purpose, it is known to modify the geometry of the tower only in its upper part, intended to be fixed to the ceiling wall of the tank. More precisely, it is the distance between the upper ends of the tower masts and the first horizontal crosspieces, closest to these upper ends of the masts, which is modified in order to obtain towers of different heights. Horizontal crosspieces are added or removed while maintaining the same regular interval between all the horizontal crosspieces. The relative positions of the masts and the other horizontal crosspieces remain unchanged.

As a result of this adaptation of the total height of the tower at its upper part, the distance between the first horizontal crosspieces and the upper ends of the tower masts varies from one tower to another depending on its total height.

This variation in distance between the first horizontal crosspieces and the upper ends of the masts can in particular lead to difficulties of use when working in the tank when this distance is reduced: access to the platform allowing work in the tank can be made difficult when the first horizontal crosspieces are too close to the ceiling wall of the tank.

In addition, when used at sea in a storage tank for the transport of liquefied gas or in a storage tank for liquefied gas used as fuel, the tower is subjected to significant mechanical stresses, linked on the one hand to the temperature changes caused by the loading/unloading of the liquefied gas and on the other hand to the phenomena of sloshing of the cargo, called "sloshing" in English. These phenomena are likely to be very violent inside the tank and consequently to generate significant forces in the tank and in particular on its equipment, such as the tower intended for loading and/or unloading the liquefied gas.

The variation in the distance between the first crosspieces and the ceiling wall of the tank can thus make the structural validation of the tower complex with regard to the mechanical and thermal constraints that it must be able to withstand.

Finally, the variation in the distance between the first horizontal crosspieces and the tank ceiling wall also influences the forces that the tank ceiling wall must take up. This variation must therefore also be taken into account during the structural validation of the tank.

The use of towers with different distances between the upper ends of the masts and the first horizontal crosspieces therefore presents several disadvantages.

Summary

An idea underlying the invention is to provide a tower intended for loading and/or unloading liquefied gas from the tank, the geometry of which allows the height of the tower to be adapted by simple modifications to make and manage.

According to one embodiment, the invention proposes a tower intended for loading and/or unloading a tank intended to contain a liquefied gas, the tower comprising at least two hollow masts which extend parallel in a longitudinal direction, the masts being connected by reinforcing structures, each reinforcing structure comprising at least one crosspiece and extending perpendicular to said longitudinal direction, the reinforcing structures being distributed along the masts while being spaced apart by spacings located between the adjacent reinforcing structures along the masts, the reinforcing structures being distributed such that the spacings comprise a plurality of normal spacings having a normal spacing distance, and a number equal to one or two of adaptation spacings having an adaptation spacing distance different from said normal spacing distance.

Thanks to these characteristics, it is possible to obtain towers with different total heights without modifying the distance between the high ends of the masts and the reinforcement structure closest to these high ends. It is possible, to vary the total height of the tower, to add or remove reinforcement structures, and to localize the structural modifications on one or two pairs of reinforcement structures delimiting the adaptation spacing(s). Thus, the disadvantages related to the variable distance between the high end of the masts and the reinforcement structure closest to this high end are eliminated. In addition, the structural validation of the tower is simplified.

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

According to one embodiment, the tower comprising at least three masts, each reinforcement structure comprises a number of crosspieces equal to the number of masts, said crosspieces of each reinforcement structure being arranged according to a planar polygon.

Thus, the masts form with the reinforcement structures a right prism whose base is the plane polygon drawn by the extreme reinforcement structures. The stability of the tower is ensured.

According to one embodiment, the normal spacing distance is the same for all normal spacings.

According to one embodiment, three masts are provided and each reinforcement structure comprises three crosspieces.

According to one embodiment, said or each adaptation spacing is arranged between a first subset of the normal spacings and a second subset of the normal spacings.

According to one embodiment, said or each adaptation spacing is arranged halfway between two extreme reinforcement structures of the tower.

Thus, the modification of the geometry of the tower is advantageously located at a distance from the longitudinal ends of the tower. The modification of the geometry of the tower is furthermore preferentially located near a median plane located midway between the extreme reinforcement structures.

According to one embodiment, said or each adaptation spacing is delimited by a median reinforcement structure, the median reinforcement structure being arranged such that a number of reinforcement structures located above said median reinforcement structure and a number of reinforcement structures located below said median reinforcement structure have a difference less than or equal to 1.

The adaptation spacing or the two adaptation spacings are thus located near the middle in height of the part of the tower containing the reinforcement structures.

According to one embodiment, the tower comprises two adaptation spacings, and the adaptation spacing distances of said two adaptation spacings are the same or different.

When the adaptation distances of said two adaptation spacings are identical, it is possible to distribute the adaptation spacings symmetrically, for example with respect to the median plane. The manufacturing and assembly of the tower are simplified. The distribution of mechanical forces on the tower is improved.

When the adaptation distances of said two adaptation spacings are different, the fixing of the equipment on the tower can be easier.

According to one embodiment, said two adaptation spacings are adjacent in the longitudinal direction. The height adaptation of the tower is thus carried out in a single region of the tower located over a limited extent of the tower in the longitudinal direction D. The manufacture and assembly of the tower are facilitated.

According to one embodiment, a said adaptation spacing distance is strictly less than said normal spacing distance.

Structural validation of the tower is simplified.

According to one embodiment, said normal spacing distance is between 1500 and 3000 millimeters.

According to one embodiment, the adaptation spacing distance is strictly greater than a minimum value of the normal spacing distance and less than or equal to a maximum value of the normal spacing distance.

The minimum and maximum values of the normal spacing distance are for example equal to 1500 and 3000 millimeters (mm). For each tower according to the invention, the normal spacing distance is constant and between said minimum and maximum values.

In some embodiments, the adaptation spacing distance is greater than said normal spacing distance.

According to one embodiment, at least four reinforcement structures are provided.

According to one embodiment, the distance between a longitudinal end of the tower and an extreme reinforcement structure closest to said longitudinal end is determined by taking into account a total height of the tower, the thermal and mechanical resistance constraints thereof as well as the space constraints linked to the installation of the tower in the tank.

According to one embodiment, a number of adaptation spacings and/or the adaptation spacing distance is determined based on a distance between one or each longitudinal end of the tower and an extreme reinforcement structure closest to that longitudinal end, said normal spacing distance and a total height of the tower.

According to one embodiment, the tower further comprises additional crosspieces connecting the masts two by two between said reinforcement structures, in directions oblique to the longitudinal direction.

According to one embodiment, at least one said additional crosspiece is arranged in each of the spaces located between the reinforcement structures of the tower.

In particular, at least one additional crosspiece is provided in each adaptation space.

The invention also relates to a sealed and thermally insulating tank for storing liquefied gas, comprising a tower as described above, in which an upper end of said tower is suspended from a ceiling wall of the tank, said tank further comprising at least one pump supported by said tower, for loading or unloading the tank.

According to embodiments, such a tank may comprise one or more of the following features.

According to one embodiment, the distance between the ceiling wall of the tank and an extreme reinforcement structure closest to the upper end of the tower is between 1.5 and 6 meters, preferably between 1.7 and 5.5 meters, preferably equal to 2.7 meters.

According to one embodiment, a distance between the lower longitudinal end of the tower and an extreme reinforcement structure closest to the lower longitudinal end of the tower is between 4.7 and 4.9 meters.

Such a tank may be part of a land-based storage facility, for example for storing LNG, or installed in a floating, coastal or deep-water structure, including an LNG carrier, a floating storage and regasification unit (FSRU), a floating production and remote storage unit (FPSO) and others. Such a tank may also serve as a fuel tank in any type of vessel.

The invention also relates to a vessel for transporting liquefied gas comprising a double hull and a tank as described above arranged in the double hull.

The invention also provides a transfer system for liquefied gas, the system comprising the aforementioned vessel, insulated pipes arranged to connect the tank disposed in the double hull of the vessel to a floating or land-based storage facility and a pump for driving a flow of liquefied gas through the insulated pipes from or to the floating or land-based storage facility to or from the vessel tank.

Finally, the invention also provides a method of loading or unloading such a vessel, in which a liquefied gas is conveyed through insulated pipes from or to a floating or land-based storage facility to or from the vessel's tank.

The invention also relates to a method for designing a tower as described above, intended for loading and/or unloading a tank intended to contain a liquefied gas, the tower comprising at least two hollow masts which extend parallel in a longitudinal direction, the masts being connected by reinforcement structures, each reinforcement structure comprising at least one crosspiece and extending perpendicular to said longitudinal direction, this tower having a total height measured along the longitudinal direction, the reinforcement structures being distributed along the masts while being spaced apart by spacings located between the adjacent reinforcement structures along the masts, according to which:
- extreme reinforcement structures are positioned closest to the longitudinal ends of the tower, arranging them at predefined distances from each longitudinal end of the tower,
- determining the positions of the other reinforcement structures of the tower such that said spacings comprise a plurality of normal spacings having a normal spacing distance, and a number equal to one or two of adaptation spacings having an adaptation spacing distance different from said normal spacing distance, said adaptation spacing distance being determined as a function of the total height of the tower.

The invention also relates to a method for determining the geometry of a set of several towers each intended for loading and/or unloading a tank intended to contain a liquefied gas, each tower comprising at least two hollow masts which extend parallel in a longitudinal direction, the masts being connected by reinforcing structures, each reinforcing structure comprising at least one crosspiece and extending perpendicular to said longitudinal direction, each tower having a total height measured along the longitudinal direction, the reinforcing structures being distributed along the masts while being spaced apart by spacings located between the adjacent reinforcing structures along the masts, according to which:
- the extreme reinforcement structure closest to an upper longitudinal end of each tower is placed at the same first predefined distance from this upper longitudinal end,
- the extreme reinforcement structure closest to a lower longitudinal end of each tower is placed at the same second predefined distance from this lower longitudinal end,
- determining the positions of the other reinforcing structures of each tower such that said spacings of the reinforcing structures of each tower comprise a plurality of normal spacings having a normal spacing distance, and a number equal to one or two of adaptation spacings having an adaptation spacing distance different from said normal spacing distance, said adaptation spacing distance being determined as a function of the total height of the tower.

Thus, it is possible to design and manufacture towers of different heights all having the same distance between the upper longitudinal end of each tower and the nearest extreme reinforcing structure, the same distance between the lower longitudinal end of each tower and the nearest extreme reinforcing structure and the same normal spacing distance. These distances are uniform for the towers of said set of several towers. Only the adaptation spacing distance is modified from one tower to another to take into account the different total heights of the towers.

Brief description of the figures

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

is a schematic representation of a tank intended to contain liquefied gas, in which is installed an exemplary embodiment of a tower intended for loading and/or unloading according to the invention.

is a schematic perspective representation of the tower of the .

is a schematic representation in perspective from a different viewing angle of the tower of the .

is a schematic representation of the profile of the tower of the .

is a schematic representation of the tower's profile from another angle of view .

is a schematic representation similar to the of the tower according to the invention equipped with pumps allowing the liquefied gas to be set in motion for its transfer.

is a cutaway schematic representation of a LNG carrier tank and a loading/unloading terminal for this tank.

By convention, on the , an orthonormal reference frame defined by three axes x, y and z is used to describe the tower and the tank. The x axis corresponds to a longitudinal axis of the ship, oriented towards the front thereof and the y axis corresponds to a transverse axis perpendicular to the longitudinal axis of the ship, substantially horizontal when the tank is in place in a ship floating on a calm sea. The z axis corresponds to a transverse axis, perpendicular to the longitudinal axis of the ship, substantially vertical when the tank is in place in a ship floating on a calm sea. In the following, the term "front" will be used in reference to the front of the ship when the tank provided with the tower according to the invention is arranged in a ship.

It was represented on the a sealed and thermally insulating tank 1 for storing liquefied gas, which is equipped with a tower 2 intended for loading/unloading according to the invention, in particular allowing the liquefied gas to be loaded into the tank 1 and/or unloaded.

Liquefied gas may in particular be liquefied natural gas (LNG), i.e. a gas mixture comprising mainly methane and one or more other hydrocarbons, such as ethane, propane, n-butane, i-butane, n-pentane, i-pentane, neopentane, and nitrogen in small proportions.

Liquefied gas can also be ethane or liquefied petroleum gas (LPG), which is a mixture of hydrocarbons from oil refining, mainly comprising propane and butane.

Liquefied natural gas is stored at a temperature of approximately -162°C at atmospheric pressure.

Alternatively, the liquefied natural gas can be liquid hydrogen ( _LH2 ) stored at -253°C at atmospheric pressure, or ammonia ( _NH3 ) stored at -30°C at atmospheric pressure.

The tank 1 is for example anchored in a supporting structure 3 embarked in a ship. The supporting structure 3 is for example formed by the double hull of a ship but can more generally be formed of any type of rigid partition having appropriate mechanical properties. Alternatively, the tank can be self-supporting.

Tank 1 may be intended for the transport of liquefied gas or for receiving liquefied gas used as fuel for the propulsion of the ship.

The tank 1 is for example a membrane tank. The general structure of such a tank has a polyhedral shape and is well known per se. It will not be fully re-described in all the details here, but we recall below some basic elements of this tank 1 in the case of the embodiment shown more particularly on the .

In such a tank 1, each wall successively has, from the outside to the inside, in the thickness direction of the wall, a secondary thermally insulating barrier 4 comprising insulating elements resting against the supporting structure 3, a secondary sealing membrane 5 anchored to the insulating elements of the secondary thermally insulating barrier 4, a primary thermally insulating barrier 6 comprising insulating elements resting against the secondary sealing membrane 5 and a primary sealing membrane 7 anchored to the insulating elements of the primary thermally insulating barrier 5 and intended to be in contact with the fluid contained in the tank 1 ( ).

According to one embodiment, each thermally insulating barrier comprises a plurality of juxtaposed rectangular parallelepiped insulating blocks. The insulating blocks can be produced in different ways. According to one embodiment, each parallelepiped insulating block comprises a box in which the heat-insulating lining is housed, said box comprising a bottom panel and side panels extending between said bottom panel and the cover panel. According to another embodiment, each parallelepiped insulating block comprises a bottom panel and a cover panel with an intercalated foam block forming said heat-insulating lining.

Such a tank may also have one of the following characteristics:
- the primary waterproof membrane and/or the secondary waterproof membrane comprises corrugated iron plates welded to each other and which have corrugations,
- the primary waterproof membrane and/or the secondary waterproof membrane comprises a continuous layer of steel strakes with a low coefficient of expansion which are welded in a watertight manner by their raised side edges on parallel welding supports.

The tower 2 intended for loading and/or unloading liquefied gas from the tank 1 is for example installed in the vicinity of a rear wall 8 of the tank 1, which makes it possible to optimize the quantity of cargo likely to be unloaded by the tower 2 to the extent that the ships are generally leaning backwards using the ballasts in a particular way, in particular in order to limit vibrations ( ).

Tower 2 is suspended from a ceiling wall 9 of tank 1 ( ). The ceiling wall 9 of the tank 1 closes the latter in the upper part. Here, it comprises a wall element of the supporting structure 3. According to a preferred embodiment, the ceiling wall 9 of the tank 1 comprises, near the rear wall 8, a space of rectangular parallelepiped shape, projecting upwards, called a liquid dome (not shown in the figures). The liquid dome is defined by two transverse walls, front and rear, and by two side walls which extend vertically and project upwards from the ceiling wall 9. The liquid dome further comprises a horizontal cover 10, shown in FIGS. 2 to 6, from which the tower 2 is suspended.

The tower 2 has an elongated shape in a longitudinal direction D which extends along the z axis when the tower is installed in the tank 1. It extends between two upper 2A and lower 2B longitudinal ends, over substantially the entire height of the tank 1 ( ). The length of tower 2 in this longitudinal direction D will hereinafter be called the height of tower 2.

Each of the masts 11, 12, 13 is thus intended to extend substantially vertically when the tower 2 is installed in the tank 1.

The tower 2 according to the invention comprises at least two masts 11, 12, 13 which extend parallel in said longitudinal direction D. The masts 11, 12, 13 are connected by reinforcing structures 20, 25, 26 each comprising at least one crosspiece 21 and extending perpendicular to the longitudinal direction D (figures 2 to 6).

Each reinforcement structure 20, 25, 26 extends in a reinforcement plane Pi perpendicular to the longitudinal direction D, with i = 1 to n, n being the total number of reinforcement structures 20, 25, 26 provided in the tower 2 ( ). Each reinforcement plane Pi thus extends substantially horizontally when tower 2 is installed in tank 1.

Each of the masts 11, 12, 13 is hollow and passes through the ceiling wall 9 of the tank 1 at the level of the cover 10 of the liquid dome.

According to an embodiment such as that shown in the figures, the tower 2 according to the invention comprises at least three masts 11, 12, 13, and each reinforcement structure 20, 25, 26 comprises a number of crosspieces 21 equal to the number of masts 11, 12, 13. The crosspieces 21 of each reinforcement structure 20, 25, 26 are arranged along the edges of a polygon in said corresponding reinforcement plane Pi. In other words, the crosspieces 21 of the reinforcement structure 20, 25, 26 draw the edges of a plane polygon at the vertices of which the masts 11, 12, 13 pass.

In the example shown in Figures 1 to 6, the tower 2 comprises a tripod structure, that is to say it comprises three vertical masts 11, 12, 13, which are fixed to each other by reinforcing structures 20, 25, 26 each comprising three crosspieces 21.

The three masts 11, 12, 13 define with the crosspieces 21 a prism with a triangular section. According to one embodiment, two masts 11, 12 of said three masts 11, 12, 13 are arranged at an equal distance from the third mast 13 so that the section of the prism is an isosceles triangle.

Alternatively, the three masts can be arranged equidistant from each other so that the prism section is an equilateral triangle.

In the example shown in the figures, ten reinforcement structures 20, 25, 26 are provided, arranged in the reinforcement planes P1 to P10 ( ). The reinforcement structures 20, 25, 26 each comprise three crosspieces 21. The reinforcement planes P1 to P10 here correspond to the average planes of the crosspieces 21.

The reinforcement structures 20, 25, 26 are distributed along the masts 11, 12, 13, being spaced apart by spacings EN, EA located between the adjacent reinforcement structures 20, 25, 26 along the masts 11, 12, 13 (figures 2 and 6).

In the remainder of the description, a pair CR, CA of adjacent reinforcement structures 20, 25, 26 designates a set of two reinforcement structures 20, 25, 26 arranged side by side along said longitudinal direction D of the tower 2, without another reinforcement structure 20, 25, 26 being interposed between the two reinforcement structures of this pair (FIGS. 3 and 6). The reinforcement structures 20, 25, 26 of one of said pairs CR, CA of reinforcement structures are separated by one of said spacings EN, EA.

In the example shown in the figures, there are nine pairs of reinforcement structures 20, 25, 26 delimiting nine spacings EN, EA.

Each spacing EN, EA extends along the longitudinal direction D of the tower, over a distance called the “spacing distance”. Said spacing distance is measured, for example, between the two reinforcement planes P1-P10 delimiting said spacing EN, EA.

Remarkably, the spacings EN, EA are distributed along the longitudinal direction D of the tower 2 such that the spacings EN, EA comprise a plurality of normal spacings EN having a normal spacing distance H1, and a number equal to one or two of adaptation spacings EA having an adaptation spacing distance H2 different from said normal spacing distance H1 (Figures 2 to 6).

Thus, the reinforcing structures 20, 25, 26 are distributed along the masts 11, 12, 13 such that the reinforcing structures 20, 25, 26 of each pair CR of adjacent reinforcing structures 20, 25, 26 along the masts 11, 12, 13 are separated by the normal spacing distance H1 with the exception of only one or two pairs of adjacent reinforcing structures 25, called adaptation pairs CA, the reinforcing structures 25 of each adaptation pair CA being separated, along the masts 11, 12, 13, by the adaptation spacing distance H2.

Tower 2 preferably includes a majority of normal EN spacings.

The normal spacing distance H1 is preferably the same for all normal spacings EN of tower 2.

According to one embodiment of the invention, said or each adaptation spacing EA is arranged between a first subset of the normal spacings EN and a second subset of the normal spacings EN.

Each adaptation spacing EA is thus arranged in a central portion of the tower 2, at a distance from its longitudinal ends 2A, 2B. Said one or two adaptation spacings EA are preferably framed by a plurality of normal spacings EN.

According to one embodiment of the invention, said or each adaptation spacing EA is arranged halfway between two extreme reinforcement structures 26 of the tower 2.

The extreme reinforcing structures 26 include an upper extreme reinforcing structure closest to the upper longitudinal end 2A of the tower 2 and a lower extreme reinforcing structure closest to the lower longitudinal end 2B of the tower 2.

A median plane PM of tower 2 is defined as the plane perpendicular to the longitudinal direction D which extends midway between the extreme reinforcing structures 26 of tower 2. Said or each adaptation spacing EA is preferably arranged astride the median plane PM or adjacent to the spacing EN, EA extending astride the median plane PM (figures 2, 3 and 5).

In the following, we call “middle reinforcement structure 25” each reinforcement structure 25 arranged such that a number of reinforcement structures 20, 25, 26 located above said middle reinforcement structure 25 along the longitudinal direction D and a number of reinforcement structures 20, 25, 26 located below said middle reinforcement structure 25 along the longitudinal direction D have a difference less than or equal to 1.

Tower 2 therefore has between one and three median reinforcement structures 25.

According to one embodiment, each of said one or two adaptation pairs CA then comprises at least one median reinforcement structure 25, such that said or each adaptation spacing EA is delimited by at least one median reinforcement structure 25.

According to another embodiment, said or each adaptation spacing EA is arranged near a transverse plane at mid-height of the tower defined at mid-distance from the longitudinal ends 2A, 2B of the tower 2.

Thus, said or each adaptation spacing EA is more particularly arranged in a central portion of the tower 2 located at a distance from its two longitudinal ends 2A, 2B. This has the advantage of allowing a simplified design of the towers 2 of different heights intended for tanks 1 of different depths. As will be described in more detail later, it is then possible to fix the geometry of the ends of the towers of different heights in order to locate the structural modifications imposed by the variation of the total height of the tower 2 in the central portion of each tower 2.

In the embodiment of the invention shown in the figures, two adaptation spacings EA are provided.

Here they have identical H2 adaptation spacing distances.

Alternatively, it can be provided that the adaptation spacing distances H2 of said two adaptation spacings are different.

In the embodiment of the invention shown in the figures, said two adaptation spacings EA are adjacent in the longitudinal direction D.

Alternatively, it can be provided that these adaptation spacings EA are separated at most by a normal spacing EN.

According to one embodiment, the tower may comprise two adaptation spaces arranged symmetrically with respect to the median plane or the transverse plane at mid-height of the tower.

In one embodiment of the tower according to the invention, each adaptation spacing distance H2 is strictly less than said normal spacing distance H1.

This makes the structural validation of the tower easier, particularly from the point of view of the mechanical strength of tower 2 after the introduction of one or two EA adaptation spacings.

Preferably, said normal spacing distance H1 is between a minimum value equal to 1500 millimeters (mm) and a maximum value equal to 3000 millimeters (mm). It is for example equal to 1838 mm, which is a standard distance.

Advantageously, the normal spacing distance H1 is greater than 1838 mm, for example strictly greater than 1838 mm and less than or equal to 3000 mm.

The use of a normal spacing distance H1 greater than 1838 mm, for example equal to 3000 mm, makes it possible to install a reduced total number of reinforcement structures 20, 25, 26 and thus reduce the quantity of material used as well as the weight of tower 2.

Furthermore, since the crosspieces 21 of the reinforcement structures 20, 25, 26 are welded to the masts 11, 12, 13, the use of a reduced total number of crosspieces 21 makes it possible to limit the time required for these welds. This results in a saving of time and a reduction in the labor cost associated with the manufacture of the tower 2.

In one embodiment, the adaptation spacing distance H2 separating the reinforcement structures 25 of at least one of said one or two adaptation pairs CA is strictly greater than the minimum value of said normal spacing distance H1 and less than or equal to its maximum value. The maximum value is for example equal to 3000 millimeters.

According to the invention, a spacing between the reinforcement structures 20, 25, 26 of at most 3000 mm is envisaged. Thus, when the normal spacing distance H1 between the reinforcement structures 20, 25, 26 of the pairs of reinforcement structures CR is less than 3000 mm, the adaptation spacing distance H2 can be greater than the normal spacing distance H1 while remaining less than 3000 mm. Thus, the adaptation spacing distance H2 can be greater than the normal spacing distance H1.

Alternatively, the adaptation spacing distance H2 can also be less than the normal spacing distance H1.

Tower 2 is preferably between 15 and 50 meters long. At least four reinforcement structures 20, 25, 26 are planned.

According to the invention, the distance between each longitudinal end 2A, 2B of the tower 2 and the extreme reinforcement structure 26 closest to this longitudinal end 2A, 2B is predetermined by taking into account a total height HT of the tower ( ), the thermal and mechanical resistance constraints of the latter as well as the space constraints linked to the installation of tower 2 in tank 1.

Furthermore, a number of adaptation spacings EA and/or the adaptation spacing distance H2 is determined as a function of this distance between one or each longitudinal end 2A, 2B of the tower 2 and an extreme reinforcement structure 26 closest to this longitudinal end 2A, 2B, of said normal spacing distance H1 and of a total height HT of the tower 2.

In the following, we call the “adjustment zone” the area of the tower accommodating the EA adaptation spacing(s).

According to one embodiment, the number of normal spacings EN of tower 2 is maximized to obtain a height adjustment zone whose height is greater than 1500 mm, and less than twice the normal spacing distance H1 of tower 2.

If the height of the adjustment zone is between 1500 mm and the normal spacing distance H1 of the normal spacings of the tower, then the tower includes only one adaptation spacing EA. There is therefore also only one adaptation couple CA.

If the height of the adjustment zone is strictly greater than the normal spacing distance H1 of the tower, the latter then comprises two adaptation spacings EA. Each of the two adaptation spacings EA preferably has an adaptation spacing distance corresponding to half the height of the adjustment zone determined previously.

The height of the adjustment zone depends on the overall height of the tower, the distance between each extreme reinforcement structure 26 and the nearest longitudinal end of the tower 2 and the normal spacing distance H1.

The total height HT of the tower is for example an overall height of the tower.

As shown in Figures 1 to 6, the tower 2 further comprises additional crosspieces 22 fixed to the masts between said reinforcing structures 20, 25, 26, in directions oblique to the longitudinal direction D.

More specifically, at least one of said additional crosspieces 22 is provided in each spacing EA, EN. Preferably, a number of additional crosspieces 22 equal to the number of masts 11, 12, 13 is provided between the reinforcement structures 20, 25, 26 of each pair CR, CA of adjacent reinforcement structures.

In particular, additional crosspieces 22 are preferably provided connecting the masts 11, 12, 13 two by two in each adaptation spacing EA. The additional crosspieces 22 extend diagonally between the crosspieces 21 of the reinforcement structures 25 delimiting said or each adaptation spacing EA.

The additional crosspieces 22 form a lattice with the crosspieces 21 of the reinforcement structures 20, 25, 26.

The invention further relates to a method of designing the tower 2 described above, according to which:
- the extreme reinforcement structures 26 are positioned closest to the longitudinal ends 2A, 2B of the tower 2, arranging them at predefined distances from each longitudinal end 2A, 2B of the tower,
- the positions of the other reinforcement structures 20, 25 of the tower 2 are determined so that said spacings EN, EA comprise a plurality of normal spacings EN having a normal spacing distance H1, and a number equal to one or two of adaptation spacings EA having an adaptation spacing distance H2 different from said normal spacing distance H1, said adaptation spacing distance H2 being determined as a function of the total height HT of the tower 2.

The adaptation spacing distance H2 is also determined as a function of the predefined distances between each longitudinal end 2A, 2B of the tower 2 and the extreme reinforcement structure 26 closest to this longitudinal end 2A, 2B, and/or as a function of the normal spacing distance H1.

For example, for a total height HT of tower 2 equal to 32.196 m, after structural validation following the thermal contraction forces, the sloshing of the liquid in the tank and the inertial forces induced by the weight of tower 2, the extreme reinforcement structure 26 closest to the upper longitudinal end 2A of tower 2 is placed at a distance of 2700 mm from this upper longitudinal end 2A.

The extreme reinforcement structure 26 closest to the lower longitudinal end 2B of the tower 2 is placed at a distance of 4800 mm from this lower longitudinal end 2B. The normal spacing distance H1 is for example equal to the maximum value of the normal spacing distance, i.e. here 3000 mm.

In tower 2 according to this example, the number of normal spacings EN of tower 2 is maximized and the adaptation spacing distance EA is greater than or equal to a value of 1500 mm which corresponds to the minimum value of the normal spacing distance.

Thus, seven normal spacings EN are distributed on tower 2, which corresponds to seven pairs of reinforcement structures 20, 25, 26.

The height adjustment area of tower 2 then extends over 3696 mm. Since the height of this adjustment area is greater than the maximum value of the normal spacing distance, i.e. 3000 mm, two adaptation spacings EA corresponding to two adaptation couples CA are placed in the adjustment area.

The adaptation spacing distance H2 of each adaptation spacing EA is equal to half the height of the adjustment zone, i.e. here 1848 mm. These adaptation spacings EA are arranged side by side and placed substantially close to the median plane PM of tower 2 or halfway between the extreme reinforcement structures 26. The normal spacings EN are distributed on either side of the adaptation spacings EA with four normal spacings EN above the adaptation spacings EA and three normal spacings EN below the adaptation spacings EA.

To summarize, in this exemplary embodiment of tower 2, from the top of tower 2 to the bottom, it comprises an extreme reinforcement structure 26 closest to the upper longitudinal end 2A of the tower placed 2700 mm from this upper longitudinal end 2A, then reinforcement structures 20, 25 delimiting, with this extreme reinforcement structure 26, four normal spacings EN having said normal spacing distance H1 equal to 3000 mm, then two adaptation spacings EA each having an adaptation spacing distance H2 equal to 1848 mm, then three normal spacings EN having said normal spacing distance H1 equal to 3000 mm, the last normal spacing closest to the lower longitudinal end of tower 2 being partially delimited by the extreme reinforcement structure 26 closest to the lower longitudinal end 2B of tower 2 placed 4800 mm from this longitudinal end. lower 2B.

Tower 2 is then manufactured in accordance with the geometry of tower 2 determined using the design method according to the invention.

Thanks to the invention, it is possible to design and manufacture towers 2 of different heights in which the distance between each longitudinal end 2A, 2B of the masts 11, 12, 13 and the extreme reinforcement structure 26 closest to this longitudinal end is identical regardless of the total height HT of the tower 2.

In particular, the invention also relates to a method for determining the geometry of a set of several towers 2 as described above, each tower 2 having a total height HT measured along the longitudinal direction D, according to which:
- the extreme reinforcement structure 26 closest to an upper longitudinal end 2A of each tower 2 is placed at the same first predefined distance from this upper longitudinal end 2A,
- the extreme reinforcement structure 26 closest to a lower longitudinal end 2B of each tower 2 is placed at the same second predefined distance from this lower longitudinal end 2B,
- the positions of the other reinforcement structures 20, 25 of each tower 2 are determined so that said spacings EN, EA of the reinforcement structures 20, 25, 26 of each tower 2 comprise a plurality of normal spacings EN having a normal spacing distance H1, and a number equal to one or two of adaptation spacings EA having an adaptation spacing distance H2 different from said normal spacing distance H1, said adaptation spacing distance H2 being determined as a function of the total height HT of the tower 2.

The fact that the distance between the upper longitudinal end 2A of the tower 2, oriented towards the ceiling wall 9 of the tank 1, and the nearest extreme reinforcement structure 26 is kept constant from one tower 2 to the other makes it possible to maintain easy access to the platform which allows the installation and maintenance work of the tank 1 regardless of the depth of the tank. This access can in fact be hindered when the distance between the upper longitudinal end 2A of the tower 2 and the nearest extreme reinforcement structure 26 is reduced.

Furthermore, the fact that the distance between the lower longitudinal end 2B of the tower, oriented towards the bottom of the tank 1, and the nearest extreme reinforcement structure 26 is kept constant makes it possible to maintain the adequate dimensions for the installation of the pumps 40 at the bottom of the tower 2, as will be described below.

The design and manufacture of towers 2 of different heights and their installation in the corresponding tank is thus facilitated.

The tower 2 according to the invention is manufactured for example outside the tank 1. In the case of the example shown in the figures, sections of masts are welded together to form the masts 11, 12, 13. The crosspieces 21 are assembled by welding to the first two of the masts 11, 12, 13 at the determined positions, flat. The additional crosspieces 22 are added between these first two masts. The third mast is assembled to the other two using the crosspieces 21 and the appropriate additional crosspieces 22. The accessories are fixed to the tower 2 thus formed.

Tower 2 is then straightened and installed in tank 1.

The invention also relates to the sealed and thermally insulating tank 1 for storing liquefied gas comprising the tower 2 as described above.

As mentioned above, tower 2 is suspended, at one of its longitudinal ends, from the ceiling wall 9 of tank 1. It is fixed to a base 30 at its other longitudinal end.

The tank 1 according to the invention further comprises at least one pump 40 supported by said tower 2, for loading or unloading the tank 1. For example, two pumps 40 are provided which are housed between the base 30 of the tower 2 and the extreme reinforcement structure 26 closest to this base 30 ( ).

In the example shown in the figures, two of the masts 11, 12 form an unloading line for the tank 1 and are each associated with one of the unloading pumps 40 for this purpose. The third mast 13 forms an emergency well allowing the descent of an emergency pump and an unloading line in the event of failure of the other unloading pumps.

Preferably, according to the invention, the distance between the ceiling wall 9 of the tank 1 and the extreme reinforcement structure 26 closest to the upper longitudinal end 2A of the tower 2 is between 1.5 and 6 meters, preferably between 1.7 and 5.5 meters, preferably equal to 2.7 meters.

More specifically, according to an exemplary embodiment, the distance between the ceiling wall 9 of the tank 1 and the extreme reinforcement structure 26 closest to the upper longitudinal end 2A of the tower 2 for a tank corresponding to the Mark III® product is between 2 and 4.5 meters.

According to another exemplary embodiment, the distance between the ceiling wall 9 of the tank 1 and the extreme reinforcement structure 26 closest to the upper longitudinal end 2A of the tower 2 for a tank corresponding to the product NO96® is between 2 and 5.5 meters.

According to another exemplary embodiment, the distance between the ceiling wall 9 of the tank 1 and the extreme reinforcement structure 26 closest to the upper longitudinal end 2A of the tower 2 for a tank corresponding to the Mark III® product for a ship powered by liquefied gas is between 1.7 and 4.2 meters.

It is possible, for example, to envisage that the distance between the ceiling wall 9 of the tank 1 and the extreme reinforcement structure 26 closest to the upper longitudinal end 2A of the tower 2 is equal to 2700 mm for a set of towers 2 adapted to different types of tank.

Preferably, the distance between the base 30 and the extreme reinforcing structure 26 closest to the lower longitudinal end 2B of the tower 2 is between 4.7 and 4.9 meters.

The invention also relates to a ship 70 for transporting a liquefied gas, the ship comprising a double hull 72 and a tank 1 as described above arranged in the double hull.

In reference to the , a view of this vessel 70 shows the watertight and thermally insulating tank 1 of generally prismatic shape, mounted in the double hull 72 of the vessel.

In a manner known per se, loading/unloading pipelines 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 1.

According to the invention, a transfer system for a liquefied gas is provided, the system comprising the ship 70, insulated pipes 73, 79, 76, 81 arranged so as to connect the tank 1 arranged in the double hull of the ship to a floating or land-based storage facility 77 and a pump for driving a flow of liquefied gas through the insulated pipes from the floating or land-based storage facility to the tank of the ship or from the tank of the ship to the floating or land-based storage facility.

To load and unload the ship 70 according to the invention, a liquefied gas is conveyed through insulated pipes 73, 79, 76, 81 from a floating or land-based storage facility 77 to the tank 1 of the ship 70 or from the tank 1 of the ship 70 to the floating or land-based storage facility 77.

There represents an example of a maritime terminal comprising a loading and unloading station 75, an underwater pipeline 76 and an onshore installation 77. The loading and unloading station 75 is a fixed offshore installation comprising a mobile arm 74 and a vertical pipeline 78 which supports the mobile arm 74. The mobile arm 74 carries a bundle of insulated flexible pipes 79 which can be connected to the loading/unloading pipelines 73. The orientable mobile arm 74 adapts to all sizes of LNG carriers. A connecting pipe, not shown, extends inside the vertical pipe 78. The loading and unloading station 75 allows the loading and unloading of the LNG carrier 70 from or to the onshore installation 77. The latter comprises liquefied gas storage tanks 80 and connecting pipes 81 connected by the subsea pipe 76 to the loading or unloading station 75. The subsea pipe 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the onshore installation 77 over a long distance, for example 5 km, which makes it possible to keep the LNG carrier 70 at a great distance from the coast during the 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 equipping the onshore installation 77 and/or pumps equipping the loading and unloading station 75 are used.

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

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

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

Claims (19)

Tower (2) intended for loading and/or unloading a tank (1) intended to contain a liquefied gas, the tower (2) comprising at least two hollow masts (11, 12, 13) which extend parallel in a longitudinal direction (D), the masts (11, 12, 13) being connected by reinforcing structures (20, 25, 26), each reinforcing structure (20, 25, 26) comprising at least one crosspiece (21) and extending perpendicular to said longitudinal direction (D), the reinforcing structures (20, 25, 26) being distributed along the masts (11, 12, 13) while being spaced apart by spacings (EN, EA) located between the adjacent reinforcing structures (20, 25, 26) along the masts (11, 12, 13), the reinforcing structures (20, 25, 26) being distributed such that the spacings (EN, EA) comprise a plurality of normal spacings (EN) having a normal spacing distance (H1), and a number equal to one or two of adaptation spacings (EA) having an adaptation spacing distance (H2) different from said normal spacing distance (H1). Tower (2) according to claim 1, comprising at least three masts (11, 12, 13), in which each reinforcing structure (20, 25, 26) comprises a number of crosspieces (21) equal to the number of masts (11, 12, 13), said crosspieces (21) of each reinforcing structure (20, 25, 26) being arranged according to a planar polygon. Tower (2) according to claim 2, comprising three masts (11, 12, 13) and in which each reinforcing structure (20, 25, 26) comprises three crosspieces (21). Tower (2) according to one of claims 1 to 3, in which said or each adaptation spacing (EA) is arranged between a first subset of the normal spacings (EN) and a second subset of the normal spacings (EN). Tower (2) according to claim 4, wherein said or each adaptation spacer (EA) is arranged halfway between two extreme reinforcing structures (26) of the tower (2). Tower (2) according to one of claims 1 to 5, wherein said or each adaptation spacing (EA) is delimited by a median reinforcement structure (25), the median reinforcement structure (25) being arranged such that a number of reinforcement structures (20, 25, 26) located above said median reinforcement structure (25) and a number of reinforcement structures (20, 25, 26) located below said median reinforcement structure (25) have a difference less than or equal to 1. Tower (2) according to one of claims 1 to 6, comprising two adaptation spacings (EA), in which the adaptation spacing distances (H2) of said two adaptation spacings (EA) are identical or different. Tower (2) according to claim 7, wherein said two adaptation spacings (EA) are adjacent in the longitudinal direction (D). Tower (2) according to one of claims 1 to 8, in which a said adaptation spacing distance (H2) is strictly less than said normal spacing distance (H1). Tower (2) according to one of claims 1 to 9, in which said normal spacing distance (H1) is between 1500 and 3000 millimeters. Tower (2) according to one of claims 1 to 10, in which a said adaptation spacing distance (H2) is strictly greater than said normal spacing distance (H1) and less than or equal to 3000 millimeters. Tower (2) according to one of claims 1 to 11, in which at least four reinforcing structures (20) are provided. Tower (2) according to one of claims 1 to 12, further comprising additional crosspieces (22) fixed to the masts (11, 12, 13) between said reinforcing structures (20), in directions oblique to the longitudinal direction (D). Tower (2) according to claim 13, in which at least one said additional crosspiece (22) is arranged in each of the spaces (EN, EA) located between the reinforcement structures (20) of the tower (2). A sealed and thermally insulating tank (1) for storing liquefied gas, comprising a tower (2) according to one of claims 1 to 14, in which an upper end (2A) of said tower (2) is suspended from a ceiling wall (9) of the tank, said tank (1) further comprising at least one pump (40) supported by said tower (2), for loading or unloading the tank (1). A vessel (70) for transporting a liquefied gas, the vessel comprising a double hull (72) and a tank (1) according to claim 15, arranged in the double hull. A transfer system for liquefied gas, the system comprising a vessel (70) according to claim 16, insulated pipes (73, 79, 76, 81) arranged to connect the tank (1) disposed in the double hull of the vessel (70) to a floating or land-based storage facility (77) and a pump for driving a flow of liquefied gas through the insulated pipes (73, 79, 76, 81) from the floating or land-based storage facility (77) to the vessel tank (1) or from the vessel tank (1) to the floating or land-based storage facility (77). A method of loading or unloading a ship (70) according to claim 16, in which a liquefied gas is conveyed through insulated pipes (73, 79, 76, 81) from a floating or land-based storage facility (77) to the tank (1) of the ship (70) or from the tank of the ship to the floating or land-based storage facility (77). Method for designing a tower intended for loading and/or unloading a tank (1) intended to contain a liquefied gas, the tower (2) comprising at least two hollow masts (11, 12, 13) which extend parallel in a longitudinal direction (D), the masts (11, 12, 13) being connected by reinforcing structures (20, 25, 26), each reinforcing structure (20, 25, 26) comprising at least one crosspiece (21) and extending perpendicular to said longitudinal direction (D), this tower having a total height measured along the longitudinal direction, the reinforcing structures (20) being distributed along the masts (11, 12, 13) while being spaced apart by gaps located between the adjacent reinforcing structures along the masts (11, 12, 13), according to which:
- extreme reinforcement structures (26) are positioned closest to the longitudinal ends (2A, 2B) of the tower (2), arranging them at predefined distances from each longitudinal end (2A, 2B) of the tower,
- the positions of the other reinforcement structures of the tower are determined so that said spacings comprise a plurality of normal spacings (EN) having a normal spacing distance (H1), and a number equal to one or two of adaptation spacings (EA) having an adaptation spacing distance (H2) different from said normal spacing distance (H1), said adaptation spacing distance (H2) being determined as a function of the total height (HT) of the tower (2).