Sealed and thermally insulating tank equipped with a loading / unloading column

Abstract

The invention relates to a tank for storing and / or transporting a fluid and intended for a ship having a longitudinal direction (X), the tank comprising: · a column for loading / unloading the fluid, · a first sump (30) provided in a bottom wall (23), · a supporting foot (31) fixed in an area of the bottom wall, the column comprising at least three vertical masts (11, 12, 13), two of which are arranged in a first transverse plane (P1) orthogonal to the longitudinal direction (X), the masts (11, 12, 13) delimiting, by axial projection onto the bottom wall, a first perimeter, the column bearing a first pump (20) entirely arranged outside the first perimeter and extending into the first sump (30), the supporting foot (31) being arranged in a second transverse plane (P2), parallel to the first transverse plane (P1), the first pump (20) extending in a third transverse plane (P3), parallel to the first transverse plane (P1), the first transverse plane (P1) and the third transverse plane (P3) being situated one on each side of the second transverse plane (P2).

Description

Watertight and thermally insulated tank equipped with a loading / unloading tower

[0001] The present invention relates to the field of vessels transporting a fluid, such as, for example, liquefied natural gas (LNG). More particularly, the present invention relates to the field of tanks equipping such vessels, in which the liquefied gas, for example, natural gas in its liquid state, is stored, and which include liquefied natural gas loading / unloading towers for loading fluid into the tank and / or unloading it. Technological background

[0002] In the prior art, it is known that sealed and thermally insulated liquefied gas storage tanks are carried on board a ship and equipped with a loading / unloading tower. The loading / unloading tower is generally suspended from a ceiling wall of a load-bearing structure, the load-bearing structure representing the ship's internal hull. The tank also has a support foot that is fixed to the load-bearing structure in an area of ​​the tank's bottom wall. The support foot is designed to provide vertical translational guidance for the loading / unloading tower.

[0003] Such a tank may include a corrugated primary sealing membrane designed to be in contact with the liquefied gas. The corrugated sealing membrane comprises multiple corrugations to increase its flexibility, particularly in the event of deformations caused by significant temperature variations.

[0004] At sea, under the action of waves, liquefied gas storage tanks are subject to cargo sloshing within the tank. These phenomena can be very violent inside the tank and can generate significant stresses within the tank and particularly on its equipment, such as the loading / unloading tower.

[0005] The risk of experiencing significant sloshing is lower when the tank's fill level is close to its maximum or when the tank contains only a small amount of liquefied gas. Thus, since LNG carrier tanks are designed to transport liquefied gas, their fill level is close to maximum on the outbound journey and contains only a small amount of liquefied gas on the return journey, thereby limiting the risk of significant sloshing.

[0006] This is not the case for tanks storing liquefied gas used as fuel for the ship's needs, particularly for propulsion, since the tank's fill level varies across its entire filling range. Furthermore, such tanks are generally smaller, resulting in greater space constraints on the tank equipment, especially the loading / unloading tower.

[0007] In what follows, the context of the invention and the invention itself will be described using LNG as an example. However, the invention is by no means limited to this and can be applied to other liquefied gases, liquefied petroleum gas, hydrogen, and ammonia being cited as non-limiting examples.

[0008] This is a schematic cutaway view of a sealed, thermally insulated fluid storage tank equipped with a prior art loading / unloading tower. A sealed, thermally insulated liquefied gas storage tank 1 is shown, equipped with a loading / unloading tower 2, which allows for loading and / or unloading the liquefied gas into tank 1. The liquefied gas may be liquefied natural gas (LNG), i.e., a gaseous mixture consisting mainly of methane, along with one or more other hydrocarbons, such as ethane, propane, n-butane, and a small proportion of nitrogen.

[0009] Tank 1 is anchored to a load-bearing structure 3 onboard a ship. The load-bearing structure 3 is, for example, formed by the ship's double hull, but can more generally be any type of rigid bulkhead with suitable mechanical properties. Tank 1 may be intended for the transport of liquefied gas or for receiving liquefied gas used as fuel for the ship's propulsion.

[0010] The tank 1 can be a membrane tank. In such a tank 1, each wall can successively present, from the outside to the inside, according to 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.

[0011] As an example, each wall can notably be of type Mark III, as described for example in FR2691520, of type NO96 as described for example in FR2877638, or of type Mark V as described for example in WO14057221.

[0012] The loading / unloading tower 2 is preferably installed in the vicinity of the rear wall 8 of the tank 1, which optimizes the amount of cargo that can be unloaded by the loading / unloading tower 2, since ships are generally inclined towards the rear using ballast in a particular way, especially to limit vibrations.

[0013] The loading / unloading tower 2 is suspended from an upper wall 9 of the supporting structure 3. The upper wall 9 of the supporting structure 3 may include, near the rear wall 8, an upward-projecting rectangular parallelepiped-shaped space (not shown), called the liquid dome. The liquid dome is defined by two transverse walls, front and rear, and by two lateral walls that extend vertically and project upwards from the upper wall 9 at an opening in the tank. The liquid dome also includes a horizontal cover 10, shown in Figures 2 and 3, from which the loading / unloading tower 2 is suspended.

[0014] The loading / unloading tower 2 extends over substantially the entire height of the tank 1. The loading / unloading tower 2 generally has a tripod structure, that is to say, it has three vertical masts 11, 12, 13, which are each fixed to each other by cross members 14. Each of the masts 11, 12, 13 is hollow and passes through the cover 10 of the liquid dome.

[0015] The three masts 11, 12, 13, together with the crossbeams 14, define a prism with a triangular cross-section. The three masts 11, 12, 13 can be arranged equidistant from each other so that the cross-section of the prism is an equilateral triangle. Advantageously, the three masts 11, 12, 13 are arranged such that at least one face of the prism lies in a transverse plane P1 that is orthogonal to the longitudinal direction X of the ship. In other words, two of the masts 11, 12 are aligned in the transverse plane P1. More specifically, the two masts 11, 12 that are aligned in the transverse plane P1 are the two aft masts, that is, the ones closest to the aft wall 8 of the hull 1.

[0016] This is a perspective view of a tank loading / unloading tower according to the prior art, notably described in document FR3080832A1.

[0017] As shown in the figure, the forward mast 13 may have a larger diameter than the two aft masts 11 and 12. The forward mast 13 forms an emergency well allowing the lowering of an emergency pump and a discharge line in case of failure of the other discharge pumps.

[0018] Furthermore, as shown, the two masts 11, 12 can form conduits for the passage of electrical supply cables, notably supplying the unloading pumps supported by the loading / unloading tower 2. In addition, the installation includes three unloading conduits 15, 16, 17, shown in the figure, which are each connected to an unloading pump 18, 19, 20. The three unloading conduits 15, 16, 17 are arranged here in the transverse plane P1. The three discharge conduits 15, 16, 17 are more particularly placed between the two masts 11, 12. Thus, the preferential direction of the sloshing phenomena being oriented transversely to the longitudinal direction X of the ship, such an arrangement of the discharge conduits 15, 16, 17 between the two masts 11, 12 makes it possible to protect them from the sloshing phenomena.

[0019] Alternatively, the two masts 11 and 12 can each be connected to a discharge pump and form a discharge line. The loading / unloading tower 2 is then equipped with conduits for the passage of electrical power cables which are arranged in the transverse plane P1 and are placed between the two masts 11 and 12.

[0020] Furthermore, as shown, the loading / unloading tower 2 is also equipped with two loading lines 21 and 22, which are attached to the forward mast. One of the two loading lines 21, shown only in Figure 1, extends only in the upper portion of tank 1, while the other loading line 22 extends substantially over the entire height of tank 1 to near the bottom wall 23 of tank 1. Advantageously, the loading line 22 that extends substantially over the entire height of tank 1 is aligned with the mast 13 along a transverse plane that is orthogonal to the longitudinal direction X of the ship. This helps to limit the stresses due to sloshing phenomena acting on this loading line 22.

[0021] At the lower part of the loading / unloading tower, the unloading pumps 18, 20 are each arranged in a sump 30. The sumps 30 are provided in the bottom wall and are intended to keep the suction members 15 of the lateral pumps 18, 20 immersed in a certain quantity of liquefied gas, despite the sloshing phenomena of said liquefied gas, so as to avoid losing prime and / or degrading said lateral pumps 18, 20. In other words, a sump 30 receives the suction member of one of the lateral pumps 18, 20.

[0022] The sump 30 receives the pump's suction inlet. As is known, the sump 30 comprises a primary cylindrical basin that provides a first reservoir connected to the interior of the tank, and a secondary cylindrical basin that provides a second reservoir surrounding the lower part of the primary cylindrical basin. The primary cylindrical basin is continuously connected to the bottom wall 23 of the tank, thus completing it in a watertight manner. An inlet to the sump 30, that is, an opening through which the fluid present in the tank can enter the sump, is provided flush with the bottom wall 23 of the tank.

[0023] In document FR3080832A1, the central pump 19 is positioned in the transverse plane P1, between the masts 11 and 12, which protects it against sloshing. The two lateral pumps 18 and 20 are aligned with each other in a transverse plane P2 containing the support foot and perpendicular to the longitudinal direction X of the vessel. The sumps, and therefore the pumps 18 and 20, are located on either side of the prism described above.

[0024] Compared to other existing solutions, in which the side pumps are positioned between planes P1 and P2, the solution in document FR3080832A1 provides sufficient distance between the side pumps 18 and 20 so that their suction unit can be housed in the sumps 30 without further increasing the dimensions of the loading / unloading tower. Indeed, to ensure acceptable mechanical strength of the tank walls, it is necessary to maintain a minimum distance between equipment that interrupts the multi-layered structure of the walls, such as the sumps or the support base of the loading / unloading tower.Therefore, since a support foot is located in the area of ​​the bottom wall opposite the central axis of the loading / unloading tower, the sumps intended to house the suction members of the side pumps must be sufficiently far from the central axis of the loading / unloading tower to avoid compromising the mechanical behavior of the tank's bottom wall. Furthermore, in document FR3080832A1, the support foot is aligned with the side pumps 18 and 20 in plane P2 and is specifically centered between the two side pumps 18 and 20. This arrangement is advantageous because it limits the stresses due to the sloshing phenomenon acting on the side pumps 18 and 20 and on the support foot.

[0025] As will become apparent from the description of the invention, although it applies to all types of tanks, the invention advantageously finds application in tanks in which liquefied gas is stored for use as fuel for the ship's needs, for example, for ships powered by fuel stored in one of its tanks. Such tanks are characterized by their smaller dimensions compared to the tanks of ships such as a conventional LNG carrier. For a small-volume tank, for example, 12,700 m³ 3 The dome is smaller than the dome of a so-called standard-sized tank (49,000 m³). 3The opening of a small-volume tank therefore has smaller dimensions compared to those of so-called standard-sized tanks. As a non-limiting example, the opening of a standard tank may measure approximately 6 m in length and 4.9 m in width, while the opening of a small tank may measure approximately 5.6 m in length and 3.5 m in width.

[0026] In the case of a tank with such a small opening, the previously discussed positioning of the side pumps is not optimal. Because the opening is smaller, the sumps end up outside the perimeter defined by the axial projection of the opening onto the tank's bottom wall. In other words, the sumps are not aligned with the opening; that is, they are not positioned below it. Such a configuration of the sumps, and therefore of the side pumps, would necessitate the installation of additional pump supports after the mast is installed in the tank.

[0027] The invention aims to overcome all or part of the problems mentioned above by proposing an innovative sump arrangement allowing the lateral pumps to be positioned below the opening of the tank dome, regardless of the tank category considered (standard for the storage and transport of liquefied gas or reduced size for the storage of liquefied gas used as fuel), while ensuring good mechanical behavior of the bottom wall as well as a limitation of the forces due to cargo sloshing acting on the pumps.

[0028] To this end, the invention relates to a storage and / or transport tank for a fluid anchored to a supporting structure intended for a ship, the ship having a longitudinal direction, the tank comprising: a fluid loading / unloading tower suspended from a ceiling wall of the supporting structure, at least one first sump provided in a bottom wall of the tank, a support foot fixed to the supporting structure in an area of ​​the bottom wall of the tank and arranged to ensure vertical translational guidance of the loading / unloading tower,

[0029] the loading / unloading tower comprising at least three vertical masts, two of the at least three masts being arranged in a first transverse plane which is orthogonal to the longitudinal direction of the ship, the masts delimiting, by axial projection onto the bottom wall of the tank, a first perimeter, the loading / unloading tower being equipped with at least one first pump, the first pump being entirely located outside the first perimeter and extending, at least partially, into the first sump, the support foot being arranged in a second transverse plane, parallel to the first transverse plane, the tank being characterized in that the first pump extends in a third transverse plane, parallel to the first transverse plane, the first transverse plane and the third transverse plane being located on either side of the second transverse plane and the tank comprising a second sump formed in the bottom wall of the tank,the loading / unloading tower being equipped with a second pump entirely located outside the first perimeter and extending, at least partially, into the second sump, the second pump being aligned with the first pump in the third transverse plane.

[0030] Thanks to these features, the pump(s) are positioned below the opening of the tank dome while respecting the minimum distances required between the different elements associated with the loading / unloading tower such as the pump and the support foot.

[0031] This also ensures pump redundancy. If one of the pumps were to fail, the other pump can take over the function of pumping and discharging the liquefied gas.

[0032] Advantageously, the first and second pumps are arranged on either side of a longitudinal axis perpendicular to the second transverse plane and passing through the support base. The two pumps are positioned on opposite sides of the loading / unloading tower.

[0033] In one embodiment of the invention, the third transverse plane is tangent to the first perimeter. The sumps are therefore aligned with the third mast.

[0034] In another embodiment of the invention, the third transverse plane is located outside the first perimeter. The sumps are further from the masts than in the previously mentioned embodiment. The distance between the pumps and the support base is greater and contributes to good mechanical strength of the tank bottom wall.

[0035] Advantageously, the tank includes an opening in the ceiling wall for the passage of a dome structure. This opening, projected axially onto the tank's bottom wall, defines a second perimeter. The pump(s) are entirely located within this second perimeter. The pumps are thus positioned below the opening, near the lower part of the loading / unloading tower, eliminating the need for additional pump supports.

[0036] Advantageously, the loading / unloading tower includes a base which extends horizontally and which is fixed to a lower end of the loading / unloading tower in a manner rigidly connected to the at least three masts, the pump(s) being fixed to the base.

[0037] The invention also relates to a vessel comprising a hull forming a load-bearing structure and at least one tank as described above anchored to said load-bearing structure.

[0038] The invention also covers a method of loading or unloading such a vessel, in which a fluid is conveyed through insulated pipes from or to a floating or land-based storage facility to or from the vessel's tank.

[0039] Finally, the invention relates to a fluid transfer system, the system comprising such a vessel, pipes arranged to connect the vessel's tank to a floating or land-based storage facility, and a pump to drive a fluid through the pipes from or to the floating or land-based storage facility to or from the vessel's tank. Brief description of the figures

[0040] These features and advantages, and others, of the present invention will become more apparent from the following description, made with reference to the accompanying drawings, given by way of non-limiting examples, and in which:

[0041] Laest is a schematic cutaway view of a sealed and thermally insulated fluid storage tank equipped with a prior art loading / unloading tower;

[0042] This is a perspective view of a tank loading / unloading tower according to the prior art;

[0043] This is a perspective view of a tank loading / unloading tower according to an example of an embodiment of the present invention;

[0044] This is a simplified top view, from the opening of the tank, of the tank loading / unloading tower according to the invention;

[0045] This is a simplified top view, from the opening of the tank, of the tank loading / unloading tower according to the invention;

[0046] This is a perspective view of the lower part of the tank loading / unloading tower according to the invention;

[0047] This is a detailed view from below of the loading / unloading tower illustrating the guidance of the loading / unloading tower on the support foot;

[0048] This is a top view of the back wall at the loading / unloading tower;

[0049] Laest is a schematic cutaway representation of a ship tank according to the invention and of a loading / unloading terminal for this tank.

[0050] For the sake of clarity, the same elements will carry the same markers in the different figures.

[0051] The features, variations, and different embodiments of the invention, as described or as they will be presented in the detailed description that follows, can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variations of the invention may include only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0052] The invention relates to a sealed and thermally insulated liquefied gas storage tank equipped with a loading / unloading tower for loading and / or unloading liquefied gas into the tank. By way of non-limiting example, the liquefied gas may include liquefied natural gas (LNG).

[0053] This is a schematic cutaway view of a sealed and thermally insulated fluid storage tank equipped with a prior art loading / unloading tower. It has been described previously.

[0054] This is a perspective view of a tank loading / unloading tower according to the prior art, and has been discussed above.

[0055] Laest is a perspective view of a tank loading / unloading tower according to an embodiment of the present invention. The fluid storage and / or transport tank according to the invention is anchored to a supporting structure intended for a ship, the ship having a longitudinal direction X. The tank comprises a liquefied gas loading / unloading tower 2 suspended from a ceiling wall of the supporting structure, at least one first sump 30 provided in a bottom wall of the tank, and a support foot 31 fixed to the supporting structure in an area of ​​the bottom wall of the tank and arranged to ensure vertical translational guidance of the loading / unloading tower.

[0056] The loading / unloading tower comprises at least three vertical masts, two of which, 11 and 12, are arranged in a first transverse plane P1, which is orthogonal to the longitudinal direction X of the ship. The masts define, by axial projection onto the bottom wall of the tank, a first perimeter. The loading / unloading tower supports at least one first pump 20, the first pump 20 being entirely located outside the first perimeter and extending, at least partially, into the first sump 30. The support base 31 is arranged in a second transverse plane P2 (not shown for clarity), parallel to the first transverse plane P1. According to the invention, the first pump 20 extends in a third transverse plane P3, parallel to the first transverse plane P1, the first transverse plane P1 and the third transverse plane P3 being located on either side of the second transverse plane P2.

[0057] The loading / unloading tower shown in Figure 1 therefore comprises the same elements as the loading / unloading tower shown in Figure 2. It differs from the loading / unloading tower shown in Figure 1 by a different positioning of the sump(s). As a result, at least one lateral pump 20 (here, the first pump 20) extends into the third transverse plane P3. In other words, at least one sump 30 is located in plane P3.

[0058] The positioning of the transverse planes P1, P2, P3 is described below and the resulting advantages will be detailed based on the description of figures 4 and 5.

[0059] This is a simplified top view, from the tank opening, of the tank loading / unloading tower 2 according to the invention. Through the tank opening, delimited by the perimeter 80, the tank bottom wall 23 is visible, the grid representing the undulations of the membrane. The three masts 11, 12, 13 of the loading / unloading tower are also visible. The three masts define, by axial projection onto the tank bottom wall, a first perimeter. The loading / unloading tower carries at least one first pump 20, the first pump being entirely located outside the first perimeter and extending, at least partially, into a first sump 30.

[0060] Masts 11 and 12 are aligned in the first transverse plane P1, which is orthogonal to the longitudinal direction X of the ship. Advantageously, the first transverse plane P1 passes through the center of masts 11 and 12, but it is understood that the first transverse plane P1 may be slightly offset, in which case the first transverse plane P1 intersects masts 11 and 12.

[0061] The support foot 31 is fixed to the load-bearing structure in a section of the tank bottom wall. It is located within the prism defined by the three masts 11, 12, and 13 and is designed to guide the loading / unloading tower in vertical translation. The support foot 31 lies in the second transverse plane P2, parallel to the first transverse plane P1. Advantageously, the second transverse plane P2 passes through the center of the support foot, but it is understood that the second transverse plane P2 may be slightly offset, in which case the second transverse plane P2 intersects the support foot.

[0062] A third transverse plane P3 is defined, parallel to the first transverse plane P1, such that the first transverse plane P1 and the third transverse plane P3 are located on either side of the second transverse plane P2. Plane P3 is distinct from planes P1 and P2. In other words, in axial projection onto the back wall, and as shown in the diagram, plane P1 lies on one side of plane P2, and plane P3 lies on the other side of plane P2. As will be described below, plane P3 can be a plane located between plane P2 and a plane parallel to plane P2 that intersects mast 13. In another variant, plane P3 can be a plane parallel to plane P2 that intersects mast 13. And in yet another variant, plane P3 can be a plane parallel to plane P2 such that plane P2 and plane P3 are arranged on either side of a plane parallel to plane P2 that intersects mast 13.

[0063] According to the invention, the first pump 20 extends in the third transverse plane P3. The sump 30 is therefore positioned in plane P3. Advantageously, the third transverse plane P3 passes through the center of the sump, but it is understood that the third transverse plane P3 may be slightly offset, in which case the third transverse plane P3 intersects the sump 30.

[0064] According to the invention, the tank includes a second sump formed in the bottom wall of the tank, the loading / unloading tower carrying a second pump 18 entirely disposed outside the first perimeter and extending, at least partially, into the second sump, the second pump 18 being aligned with the first pump 20 in the third transverse plane P3.

[0065] This ensures redundancy of the pumps in case one pump should fail.

[0066] In the rest of the description the first pump 20 and the second pump 18 can also be referred to as lateral pumps.

[0067] In this embodiment, the first pump 20 and the second pump 18 are advantageously arranged on either side of a longitudinal axis M perpendicular to the second transverse plane P2 and passing through the support foot 31. The first pump 20 and the second pump 18 are therefore positioned on either side of the loading / unloading tower and, in particular, on either side with respect to the plane M which is defined here by the alignment of the support foot 31 and the mast 13.

[0068] In this embodiment and preferably, the first pump 20 and the second pump 18 are positioned on either side of the plane defined by the alignment of the support foot 31 and the mast 13 and symmetrically to this plane.

[0069] It will be noted that in the embodiment illustrated in figures 4 and 5, the first pump 20 is aligned with the mast 12 along a plane extending along the longitudinal axis X' perpendicular to the second transverse plane P2 and passing through the center of the sump 30 in which the first pump 20 is disposed at least in part.

[0070] Similarly, the second pump 18 is aligned with the mast 11 along a plane extending along a longitudinal axis X'' and extending along a longitudinal axis perpendicular to the second transverse plane P2 and passing through the center of the sump 30 in which the second pump 18 is disposed at least in part.

[0071] Aligning the first and second pumps with a mast of the loading / unloading tower respectively optimizes the tank arrangement according to the invention by allowing the pumps to be inserted or extracted through the opening in the tank located at the top of the tank without having to enlarge or modify this opening.

[0072] Aligning the first pump 20 and the second pump 18 on the same plane allows for a symmetrical tank arrangement, grouping in the same plane the areas containing the sumps 30, which at least partially accommodate the first pump 20 or the second pump 18, thus balancing the tank structure.

[0073] This results in a balanced tank structure that improves the behavior of the bottom wall of the tank in the face of sloshing.

[0074] This new positioning of the sumps relative to the support base is particularly advantageous. It allows the sumps to be positioned below the tank opening, despite a smaller opening. Furthermore, it brings the sumps closer to the loading / unloading tower, thus reducing the leverage required to support the pumps within the sumps. Consequently, additional supports are not needed after the loading / unloading tower is installed in the tank. This results in a simplified installation and greater robustness of the base connecting the pumps to the tower.

[0075] This positioning of the sumps in the third transverse plane P3 is highly innovative. Indeed, it is known from the prior art that a minimum distance between the sump and the support base, for example 2.04 meters, is essential to ensure proper mechanical stability of the tank walls. Not wanting to compromise the mechanical behavior of the tank's bottom wall, the prior art dictates placing the sumps further from the loading / unloading tower. The invention, on the contrary, proposes a solution in which the sumps are positioned as close as possible to the loading / unloading tower, but offset from the prior art approach.

[0076] Let X' or X'' be one of the longitudinal axes perpendicular to the second transverse plane P2 and passing through the center of one of the two sumps 30. As a non-limiting example, in axial projection onto the bottom wall, the distance between plane P2 and the center of sump 30 can be 1.7 m. The distance between the center of the support foot and the intersection of axis X' or X'' with plane P2 can be 1.02 m. It follows that the distance between the center of the support foot and the center of the sump, again in axial projection onto the bottom wall, is approximately 2 m.

[0077] In the embodiment presented herein, the third transverse plane P3 is located outside the first perimeter. The third plane P3 is offset from the loading / unloading tower. It does not intersect mast 13.

[0078] Thanks to this feature, the sumps are at a greater distance from the support foot, while remaining below the opening of the tank.

[0079] Advantageously, the longitudinal axis X'' intersects a rear mast while passing through the sump 30, which receives at least part of the second pump 18 located on the same side with respect to the longitudinal axis M. In other words, in axial projection onto the bottom wall, the mast 11 is located at the intersection of the axis X'' and plane P1. The same reasoning applies to the mast 12, where the longitudinal axis X'' intersects the rear mast 12 while passing through the sump 30, which receives at least part of the first pump 20 located on the same side with respect to the longitudinal axis X. In other words, in axial projection onto the bottom wall, the mast 12 is located at the intersection of the axis X'' and plane P1. The two sumps 30 are thus positioned in plane P3 at a distance close to the loading / unloading tower.

[0080] This is a simplified top view, from the tank opening, of the tank loading / unloading tower according to the invention. In this embodiment, the third transverse plane P3 is tangent to the first perimeter. The third transverse plane P3 intersects the mast 13. As shown in the figure, the third transverse plane P3 passes through the center of the mast 13.

[0081] Thus, the mast 13 is aligned with the lateral pumps 18, 20 (i.e. the first and second pumps) in the plane P3 and is more particularly centered between the two lateral pumps 18, 20. Such an arrangement is advantageous in that it allows to limit the forces due to the swaying phenomenon acting on the lateral pumps 18, 20 and on the mast 13.

[0082] In addition to the elements already presented in Figure 1, a base 27 is shown. The base is an element of a loading / unloading tower located at the lower end of the tower and connected to the support foot. It typically includes an anchoring device attached to the pumps and a vertical guide device for each pump relative to the base, as well as bushings connected to the masts.

[0083] Through this schematic representation, we see that the judicious arrangement of the sumps in the P3 plane ensures the minimum distance required between the pumps and the support foot while limiting the length of the half-boxes 47, 48 ensuring the fixing of the pumps.

[0084] This is a perspective view of the lower part of the tank loading / unloading tower according to the invention, consisting of the base 27.

[0085] The base 27 has rings 34, 35, 36 through which the lower ends of the three masts 11, 12, 13 pass. The rings 34, 35, 36 are welded to the masts 11, 12, 13 so as to fix said base 27 to the lower end of the three masts 11, 12, 13. In addition, the base 27 has a central stiffening structure 28 allowing to increase the stiffness of the base 27 and thus increase the resistance of the loading / unloading tower 2 to the phenomena of swaying.

[0086] The side pumps 18, 20 are housed in half-boxes 47, 48 open to the outside of the loading / unloading tower 2. The half-boxes 47, 48 protrude from the rest of the base 27 towards the bottom wall 23 of the tank 1, which allows the side pumps 18, 20 to be lowered sufficiently so that their suction element is housed in the sump 30. Each half-box 47, 48 is formed by a horizontal bottom 49, which is connected to two vertical walls 50, 51 of transverse orientation and one vertical wall 52 of longitudinal orientation. The bottom 49 has a cutout through which the body of one of the side pumps 18, 20 is placed. The side pumps 18, 20 are each equipped with fixing lugs ensuring their attachment to the bottom 49, around the cutout.

[0087] As shown, it can be seen that the third transverse plane P3 intersects the mast 13 intended to be inserted into the ring 36. More precisely, the third transverse plane P3 passes through the center of the ring 36, i.e., the mast 13. The perspective view of the base 27 illustrates the short distance between the pumps and the positioning of the mast 13 intended to be inserted into the ring 36. The lever arm to support the lateral pumps 18, 20 in the sumps 30 is minimized.

[0088] This is a detailed view from below of the loading / unloading tower, illustrating the guidance of the loading / unloading tower on the support foot. Typically, the tank has a support foot 31 that is fixed to the supporting structure in an area of ​​the tank's bottom wall. The support foot is arranged to provide vertical translational guidance for the loading / unloading tower. The support foot 31 typically has a circular cross-section and a truncated conical lower portion 54 that connects at its smaller diameter end to a cylindrical upper portion. The larger diameter base of the truncated conical portion bears against the bottom wall of the supporting structure. Typically, the lower truncated conical portion 54 extends through the thickness of the tank's bottom wall beyond the level of the primary sealing membrane.The upper cylindrical section is sealed by a circular plate. The primary and secondary sealing membranes are sealed to the lower truncated conical section 54.

[0089] The loading / unloading tower 2 includes a guide device fixed to the underside of the base and which cooperates with the support foot 31, which is fixed to the bottom wall of the supporting structure. This guide device is designed to allow relative movements of the loading / unloading tower 2 with respect to the support foot 31 along the height direction of the tank, enabling the loading / unloading tower 2 to contract or expand according to the temperatures to which it is subjected, while preventing horizontal movements of the base of the loading / unloading tower 2 by means of guide elements 57, 59.

[0090] This is a top view of the bottom wall at the loading / unloading tower. The watertight membrane covering the bottom wall is a corrugated membrane in which the corrugations extend in both the transverse and longitudinal directions of the vessel. This type of membrane provides sufficient flexibility to the wall to withstand the various mechanical stresses it is subjected to.

[0091] Since the sumps 30 are provided in the bottom wall 23, the membrane corrugations are interrupted in these two areas. At each sump, the interrupted corrugations terminate on the plate 29, which ensures the watertightness of the bottom wall. The corrugations terminate with a cap 32.

[0092] Between the two sumps 30 there are at least two undulations along the longitudinal axis X. On the, three undulations 61, 62, 63 extend along the axis X between the two sumps 30. This number of undulations guarantees the flexibility required in the area between the sumps to ensure good mechanical strength of the waterproofing membrane.

[0093] Figure 1 is a schematic cutaway representation of a ship tank 70 according to the invention and of a loading / unloading terminal for this tank. The cutaway view of the ship 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary sealing membrane intended to be in contact with the liquefied gas contained in the tank, a secondary sealing membrane arranged between the primary sealing membrane and the double hull 72 of the ship, and two insulating barriers arranged respectively between the primary sealing membrane and the secondary sealing membrane and between the secondary sealing membrane and the double hull 72.

[0094] As is known per se, loading / unloading pipelines 73 arranged on the upper deck of the ship can be connected, by means of suitable connectors, to a marine or port terminal to transfer a cargo of LNG to or from the tank 71.

[0095] Figure 75 represents an example of a marine terminal comprising a loading and / or unloading berth 75, a subsea pipeline 76, and an onshore facility 77. The loading and / or unloading berth 75 is a fixed offshore facility comprising a movable arm 74 and a tower 78 that supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 that can be connected to the loading / unloading pipelines 73. The steerable movable arm 74 adapts to all ship sizes. An unshown connecting pipeline extends inside tower 78. The loading and unloading station 75 allows the ship 70 to be loaded and unloaded from or to the onshore facility 77. This facility includes liquefied gas storage tanks 80 and connecting pipelines 81 linked by the subsea pipeline 76 to the loading or unloading station 75.The subsea pipeline 76 allows the transfer of liquefied gas between the loading or unloading station 75 and the onshore facility 77 over a long distance, for example 5 km, which allows the ship 70 to be kept a long distance from the coast during loading and unloading operations.

[0096] To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps equipping the land installation 77 and / or pumps equipping the loading and unloading station 75 are used.

[0097] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them 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.

[0098] The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0099] In claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

[0100] It will be more generally apparent to a person skilled in the art that various modifications can be made to the embodiments described above, in light of the teaching that has just been disclosed to them. In the claims that follow, the terms used shall not be interpreted as limiting the claims to the embodiments set forth in this description, but shall be interpreted to include all equivalents that the claims aim to cover by virtue of their formulation and whose prediction is within the grasp of a person skilled in the art based on their general knowledge.

Claims

A fluid storage and / or transport tank anchored to a supporting structure intended for a ship, the ship having a longitudinal direction (X), the tank comprising: a fluid loading / unloading tower (2) suspended from a ceiling wall of the supporting structure, at least one first sump (30) provided in a bottom wall (23) of the tank, a support foot (31) fixed to the supporting structure in an area of ​​the bottom wall of the tank and arranged to provide vertical translational guidance of the loading / unloading tower, the loading / unloading tower comprising at least three vertical masts (11, 12, 13), two of the at least three masts (11, 12) being arranged in a first transverse plane (P1) which is orthogonal to the longitudinal direction (X) of the ship, the masts (11, 12, 13) delimiting, by axial projection onto the bottom wall of the tank, a first perimeter, the loading / unloading tower being equipped with at least one first pump (20),the first pump (20) being entirely disposed outside the first perimeter and extending, at least partially, into the first sump (30), the support foot (31) being disposed in a second transverse plane (P2), parallel to the first transverse plane (P1), the tank being characterized in that the first pump (20) extends in a third transverse plane (P3), parallel to the first transverse plane (P1), the first transverse plane (P1) and the third transverse plane (P3) being located on either side of the second transverse plane (P2), and in that the tank includes a second sump formed in the bottom wall (23) of the tank, the loading / unloading tower being equipped with a second pump (18) entirely disposed outside the first perimeter and extending, at least partially, into the second sump, the second pump (18) being aligned with the first pump (20) in the third transverse plane (P3)., Tank according to claim 1, in which the first pump (20) and the second pump (18) are arranged on either side of a longitudinal axis (X') perpendicular to the second transverse plane (P2) and passing through the support foot (31). Tank according to any one of the preceding claims, wherein the third transverse plane (P3) is located outside the first perimeter. Tank according to any one of the preceding claims, wherein the third transverse plane (P3) is tangent to the first perimeter. Tank according to any one of the preceding claims, comprising an opening in the ceiling wall for the passage of a dome structure, the opening delimiting, by axial projection onto the bottom wall (23) of the tank, a second perimeter, the pump(s) being entirely disposed within the second perimeter. Tank according to any one of the preceding claims, wherein the loading / unloading tower comprises a base (27) which extends horizontally and which is fixed to a lower end of the loading / unloading tower in a manner fixed to the at least three masts (11, 12, 13), the pumps (18, 20) being fixed to the base (27). Vessel comprising a hull forming a load-bearing structure and at least one tank according to any one of the preceding claims anchored on said load-bearing structure. Method of loading or unloading a ship (70) according to claim 7, wherein a fluid is conveyed through insulated pipes (79) from or to a floating or land-based storage facility (77) to or from the tank (1) of the ship (70). Transfer system for a fluid, the system comprising a vessel (70) according to claim 7, pipelines (79) arranged to connect the tank (1) of the vessel (70) to a floating or land-based storage facility (77) and a pump for conveying a fluid through the pipelines (79) from or to the floating or land-based storage facility (77) to or from the tank (1) of the vessel (70).

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