WO2023118716A1

WO2023118716A1 - Tank comprising a sealing membrane having through-holes

Info

Publication number: WO2023118716A1
Application number: PCT/FR2022/052418
Authority: WO
Inventors: Julien COUTEAU; Edouard DUCLOY
Original assignee: Gaztransport Et Technigaz
Priority date: 2021-12-23
Filing date: 2022-12-19
Publication date: 2023-06-29
Also published as: FR3131361A1

Abstract

The invention relates to a tank for transporting and/or storing a liquefied gas, including at least a bottom wall, a top wall and side walls connecting the bottom wall to the top wall, at least the top wall including at least one sealing membrane (10) which comprises at least one series of first waves (16) intersecting a series of second waves (18), the top wall including at least a first through-hole (24), a second through-hole (26) and a third through-hole (28), the first through-hole (24) and the second through-hole (26) being aligned on a first straight line (42), while the first through-hole (24) and the third through-hole (28) are aligned on a second straight line (44) intersecting the first straight line (42), the sealing membrane including at least one uninterrupted first wave (16) between the first through-hole (24) and the second through-hole (26) and at least two uninterrupted second waves (18) between the first through-hole (24) and the third through-hole (28).

Description

Title: Tank comprising a sealed membrane with crossings

The invention relates to the field of sealed and thermally insulating tanks for the storage and/or transport of liquid at low temperature, such as tanks for the transport of Liquefied Petroleum Gas (LPG), having for example a temperature between -50°C and 0°C, or for the transport of Liquefied Natural Gas (LNG), at around -162°C and at atmospheric pressure. These tanks can be installed on land or on a floating structure. In the case of a floating structure, the tank may be intended for the transport of liquefied gas or to contain such a fluid serving as fuel for an installation on board, such as the propulsion of the floating structure.

Usually, the tanks used for the storage and/or the transport of liquid gas, include walls composed of at least one insulating mass and a sealing membrane intended to be in contact with the liquid retained in the tank. At least one of these walls can be provided with a crossing intended to allow, for example, the loading and/or the unloading of a liquid cargo. According to a known exemplary embodiment, the sealing membrane may comprise a plurality of corrugations which allow the tank to resist the thermal stresses imposed by the storage of the liquid cargo, but also the mechanical stresses imposed by the transport by ship of liquid cargo, in particular those resulting from the deformation of the ship's hull.

The crossing delimits an opening in the membrane and this opening allows the passage, for example, of a component intended to extend inside the tank. A closure plate placed on the periphery of the bushing makes it possible to connect the membrane to said bushing and to ensure the seal between them.

A first drawback of these tanks lies in the arrangement of the membrane on the periphery of the crossing. Indeed, the opening formed in the membrane cuts the waves of the latter and the closure plate usually used has the effect of reducing the elastic properties of the vessel wall around the bushing. Furthermore, the prior art uses this type of closing plate at a bottom wall of the tank, but these plates are not suitable for being installed on a wall other than the bottom wall.

An object of the present invention is therefore to overcome these drawbacks by designing a ceiling wall of a tank which has crossings arranged at three non-aligned points, a minimum number of waves being provided between these crossings.

The subject of the invention is a tank for transporting and/or storing a liquefied gas comprising at least one bottom wall, one ceiling wall and side walls connecting the bottom wall to the ceiling wall, at least the ceiling wall comprising at least one waterproof membrane which comprises at least a series of secant first waves of a series of second waves, the ceiling wall comprising at least a first via, a second via and a third via, the first via and the second crossing being aligned on a first straight line while this first crossing and the third crossing are aligned on a secant second straight line of the first straight line, the waterproof membrane comprising at least one first uninterrupted wave between the first crossing and the second crossing, as well at least two second uninterrupted waves between the first crossing and the third crossing.

Such an assembly makes it possible to pass through the ceiling wall by means of separate crossings, minimizing the impact on the mechanical rigidity resulting from these separate crossings. The design rule referred to here guarantees flexibility of the waterproof membrane between each crossing which contributes to limiting the risk of rupture of the waterproof membrane, due to its excessive rigidity.

We are aiming here for crossings that are arranged in an "L". In other words, the first straight line which passes through the first crossing and the second crossing intersects at a single point with the second straight line which passes through the first crossing and the third crossing.

The ceiling wall comprises for example at least one insulating mass which provides the thermal insulation of the tank necessary for the transport of a liquefied gas and may in particular comprise at least one layer of insulation formed of insulating panels assembled side by side. others. The membrane is impermeable to liquefied gas and includes the series of first waves and the series of second waves distributed over its surface, allowing it to better resist to the mechanical and thermal stresses generated on the tank, in particular thermal shrinkage when the tank is put in the cold. The waves on the waterproof membrane then allow it to deform so as to absorb the displacements which result from these stresses. This is particularly advantageous because these mechanical deformations are greater for a ceiling wall than for a bottom wall, adding all the more interest to the invention.

The crossing in the ceiling wall is materialized in particular by a cylinder placed transversely to the ceiling wall and of which a first free end extends into the interior volume of the tank and a second free end extends into the external environment at tank. This cylinder allows the passage of at least one tube through the ceiling wall, this tube being able to be for example a tube for loading and/or unloading the liquid cargo, or a tube for the passage of the gas emanating from the gas natural liquid contained in the tank or even a mast of a loading/unloading tower. Alternatively, the cylinder can allow the passage of men or materials, necessary for the management of the liquid cargo contained in the tank, or of the tank as such.

The opening of the waterproof membrane is a hole made in the ceiling wall and used by the cylinder forming the crossing. An edge delimiting the opening of the waterproof membrane can be adjusted around the bushing, that is to say that this edge is provided as close as possible to the bushing. In other words, the opening is made in such a way that a minimum distance is observed between the edge delimiting the opening and the crossing of the waterproof membrane. It is then understood that the crossing and the waterproof membrane have complementary surfaces allowing them to be as close as possible to each other, whether they are directly connected to each other or by means of a flange directly interposed between these two components.

According to a precision of the invention, at least a first wave extends mainly perpendicular to the second wave.

Advantageously, the first straight line passes through a center of the first crossing and a center of the second crossing, while the second straight line passes through the center of the first crossing and through a center of the third crossing. The first straight line is advantageously perpendicular to the second straight line. According to one characteristic, the sealed membrane comprises at least two first uninterrupted waves between the first crossing and the second crossing, as well as at least three second uninterrupted waves between the first crossing and the third crossing.

According to one characteristic, the tank according to the invention may comprise a loading/unloading tower comprising at least one mast which crosses the ceiling wall passing through at least one of the crossings. The loading/unloading tower can also comprise at least one tube for loading or unloading the liquefied gas which passes through the ceiling wall by using the crossing, the tube comprising at least one end positioned so as to be in contact with the liquefied gas at the liquid state present in the tank.

According to one characteristic, a distance separating the first waves located between the first crossing and the second crossing and measured perpendicularly to at least one of these first waves is between 300 and 500 mm.

According to another characteristic, a distance separating the second waves located between the first crossing and the third crossing and measured perpendicular to at least one of them is between 300 and 500 mm.

According to yet another characteristic, a first wave and a second secant wave at the level of a crossing are connected to each other by at least one deflection wave, optionally via one or more caps.

The deflection wave then makes it possible to connect a first wave to one of the second waves whose extension directions intersect the crossing. In other words, the waves of the waterproof membrane whose majority direction of elongation intersects the crossing of the ceiling wall are connected two by two by a deflection wave, the latter extending along a secant direction to the direction of the first wave and the direction of the second wave. Preferably, the misalignment base extends in a mostly straight direction between the first wave and the second wave that it joins.

Advantage is taken of this arrangement in that it makes it possible to retain an elasticity of the sealed membrane although the latter is borrowed by a crossing, by deflecting the waves and by connecting them to each other to maintain a continuity of stretching or contraction of the waterproof membrane in the vicinity of the penetration. This optimizes the resistance of the impermeable membrane to the stresses mentioned above and consequently increases the life of the tank.

The deflection wave is part of an additional plate, otherwise known as a closing partition, which is installed around the bushing, after or before positioning the base plates that make up the waterproof membrane. The waterproof membrane can thus comprise four complementary plates arranged around the bushing, connected by welding to the base plates of the waterproof membrane.

According to one characteristic of the invention, the base plate of the closing partition is connected to the base plate of the waterproof membrane at a free end of the first wave and at a free end of the second wave which it joins by minus one solder.

According to one characteristic, a maximum of four deflection waves are distributed around the bushing when the latter has a diameter less than 610 mm and preferably between 160 and 610 mm.

In addition, a maximum of eight deflection waves are distributed around the bushing when the latter has a diameter greater than 610 mm and preferably between 611 and 1100 mm.

In such a situation, the eight deflecting waves form four pairs of two deflecting waves, each deflecting wave of the same pair extending along parallel and distinct directions of extension. The complementary plates which each carry a pair of deflection waves are identical, or substantially identical in their conformation.

It should be noted that a distance measured between the cylinder forming the bushing and the direction of extension of the offset foundation furthest radially from this bushing is a maximum of 320mm.

According to one characteristic, a direction of extension of the base deflecting and a direction of extension of the first wave form a first angle complementary to a second angle formed between the direction of extending the base of deflecting and a direction of extension of the second wave. The first angle and the second angle can be equal to 45°. Alternatively, the first angle may be 60° while the second angle may be 30°. According to an exemplary embodiment of the tank, the ceiling wall comprises a main portion and a lid which closes an opening made in the main portion, the lid comprising at least a portion of the sealed membrane which comprises the series of first secant waves of the series of second waves, the cover comprising the crossings, the first crossing and the second crossing being aligned on the first straight line, the first crossing and the third crossing being aligned on the secant second straight line of the first straight line, the sealed membrane portion of the cover comprising at least the first uninterrupted wave between the first bushing and the second bushing, as well as at least the two second uninterrupted waves between the first bushing and the third bushing.

According to a first aspect of this example, the lid and the main portion of the ceiling wall are coplanar. The lid is thus at least partly disposed in a thickness of the main portion.

According to an alternative, the ceiling wall comprises a coaming provided around the opening and which protrudes from the main portion of the ceiling wall, the cover being arranged at a free end of the coaming.

According to one characteristic of the invention, at least one collar is attached to the waterproof membrane, the collar being in direct contact with the waterproof membrane, in particular with one or more closing partitions, and with one of the crossings.

It is understood that an example of the flange is a ring whose section in section along a radial direction and an axial direction of the crossing is an "L" shaped section. Such a conformation allows the flange to be in contact both with at least one closing partition of the sealed membrane and with the crossing in its axial direction, thus ensuring the seal between these two components of the sealed membrane. The flange can then be secured to the sealed membrane and to the bushing by means of a weld, or any other means ensuring the sealing required for a tank for transporting and/or storing a liquefied gas.

The flange is attached in the sense that it is a separate part from the waterproof membrane and from the bushing, this flange being installed and welded after positioning the bushing through the ceiling wall. The flange can be formed as a single piece or in a alternatively, an assembly of several parts secured to each other, for example by welding so that they form said collar.

According to another characteristic, the sealed membrane, in particular at least one closing partition arranged immediately around the bushing, comprises a folded edge which comes into direct contact with at least one of the bushings, in particular the cylinder which forms this bushing.

It is understood that the folded edge makes it possible to secure the waterproof membrane directly to the bushing and that this then ensures the tightness between these components. A folded edge is a slice of the closing partition which borders the bushing, such an edge extending in a direction substantially perpendicular to a main plane of extension of the waterproof membrane, the folded edge being in particular directed towards the inside of tank.

The waterproof membrane is thus composed of a plurality of plates, otherwise called base plates on which the first waves and the second waves are provided.

The invention also relates to a ship for transporting and/or storing liquefied gas comprising at least one tank according to any one of the preceding characteristics, the ship comprising a double hull, one of the hulls of which forms a support structure for the tank.

The invention also relates to a liquefied gas transfer system comprising a ship as described above, pipes arranged so as to connect the tank installed in the hull of the ship to a floating storage and/or treatment installation or on land and at least one pump to drive a flow of liquefied gas through the pipes between the storage and/or processing facility and the vessel's tank.

The invention also covers a method for loading and/or unloading a ship according to the preceding characteristics, during which the liquefied gas is circulated in the pipes between the floating or terrestrial storage and/or treatment installation and the vessel's tank.

Other characteristics, details and advantages of the invention will emerge more clearly on reading the description which follows on the one hand, and several examples of embodiment given by way of indication and not limitation with reference to the appended schematic drawings on the other. part, on which: [Fig. l] is a general view of a ship for storing and/or transporting a liquefied gas comprising at least one tank according to the invention;

[Fig.2] is a view taken from inside the tank and represents part of the ceiling wall of said tank;

[Fig.3] is a first enlargement of Figure 2;

[Fig.4] is a second enlargement of Figure 2.

The features, variants and different embodiments of the invention may be associated with each other, in various combinations, insofar as they are not incompatible or exclusive of each other. It is possible in particular to imagine variants of the invention comprising only a selection of characteristics described below in isolation from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention from to the state of the prior art.

In Figure 1 and in Figure 2 is shown a mark where a vertical direction V extends perpendicular to a longitudinal direction L and to a transverse direction T, the longitudinal direction "L" corresponding to a direction of advancement of a ship.

In Figure 1 is shown the ship 1, for example an LNG carrier, which comprises a double hull 100 in which are arranged for example four tanks 2 for the storage of a liquefied gas, in particular Liquefied Natural Gas (hereinafter LNG) . More specifically, the double hull 100 forms at least in part a support structure for at least one of the tanks 2, here four tanks 2.

At least one pipe 102 is arranged on the ship 1, so that it connects one of the tanks 2 installed in the hull 100 of the ship 1 to a floating or land-based storage and/or treatment facility (not shown), as well a pump for driving a flow of liquefied natural gas through the pipe 102 between the tank 2 and the storage and/or processing installation.

The tanks 2 are separated from each other by double transverse partitions 4, otherwise called "cofferdam". Each of the tanks 2 is formed of a bottom wall 20, a wall of ceiling 6 and a plurality of side walls 21. The bottom wall 20, the side walls 21 and the ceiling wall 6 comprise among other things an insulating block 8, forming part of a thermal insulation of the wall in question, and a waterproof membrane 10 composed of a plurality of base plates 12, visible in Figure 2.

The ceiling wall 6 comprises a main portion 70 and a cover 72 which closes an opening made in the main portion 70, the cover 72 comprising at least a portion of the waterproof membrane which comprises a series of first secant waves of a series of second waves. Such a cover comprises several crossings, the arrangement of which will be explained in detail in FIG. 2. According to an embodiment of such a tank 2, the cover 72 and the main portion 70 of the ceiling wall 6 are coplanar. The cover 72 is thus at least partly, and advantageously entirely, placed in a thickness of the main portion 70.

According to an alternative to this concept also illustrated in FIG. 1, the ceiling wall 6 can comprise a coaming 74 provided around the opening and which protrudes from the main portion 70 of the ceiling wall 6, extending in the external environment of the tank, that is to say outside its internal volume. According to this concept, the cover 72 provided with the waterproof membrane as described in the present document is arranged at a free end of the coaming 74, so as to close the latter.

A base plate 12 is made of an anti-corrosion material, in particular stainless steel, with a thickness for example between 0.5 mm and 1.5 mm, advantageously 1.2 mm, measured in the vertical direction V of the base plate 12, visible in Figure 2. The base plate 12 is a corrugated plate in the sense that it comprises flat portions and series of waves which surround these flat portions.

The waterproof membrane 10 of the ceiling wall 6, in particular of its cover, comprises a plurality of base plates 12. Each base plate 12 can be of a length comprised from 1020 mm to 3060 mm measured in the longitudinal direction L of the base plate 12. The base plate 12 can be between 680 mm and 1030 mm wide, measured in a transverse direction T, perpendicular to the Longitudinal direction L, of the base plate

12. The base plates 12 illustrated in FIG. 2 constitute the waterproof membrane 10 of the ceiling wall 6 of the tank 2, and more particularly of its lid 72. A base plate 12 comprises a series of first waves 16 parallel between them and extending along a first direction 46 parallel to the longitudinal direction L of the base plate 12. The base plate 12 also comprises a series of second waves 18 parallel to each other and extending along a second direction 48 parallel to the transverse direction T of the base plate 12.

The term “wave” is understood to mean a deformation of the surface of the base plate 12 in the vertical direction V of the base plate 12, which gives the membrane flexibility enabling it to absorb thermal and mechanical stresses. The waves seen in cross section then have a convex shape with a vertex 23 and thus project towards the inside of the tank 2.

The first wave(s) 16 and the second wave(s) 18 have a different height, measured between a base of the wave and the top thereof. Preferably, the first wave(s) 16 has a lower height than the second wave(s) 18. The height of the first wave(s) 16 may be between 30 and 40 mm. The height of the second waves 18 can be between 45 and 65mm. In the example shown, the height of the first wave(s) 16 is 36mm and the height of the second wave(s) 18 is 54.5mm.

The series of first waves 16 and the series of second waves 18 extend mainly along directions 46, 48 which are perpendicular to each other and form at their intersection nodes 22. A first wave 16 is thus secant of a second wave 18, for example perpendicularly.

It is understood from the above that the waterproof membrane 10, composed of a plurality of base plates 12, comprises a plurality of series of first waves 16 and a plurality of series of second waves 18. Such a configuration of the waterproof membrane 10 provides it with greater adaptation to the stresses generated on the ceiling wall of the tank, in particular to thermal shrinkage when the tank is cold, to deformations of the ship's hull, in particular due to the swell. The waves on the base plates 12 allow the ceiling wall to deform to overcome these constraints. Figure 2 shows limits 58 symbolized by a continuous line. These boundaries 58 illustrate the overlap between an edge of a base plate 12 with an edge of an adjacent base plate 12. In practice and by way of example, these limits 58 show the dimensions of a base plate 12, the latter comprising for example six first waves 16 and three second waves 18.

In order to load or unload the tanks 2 with liquefied gas, the ceiling wall of the tank 2 comprises a plurality of crossings, among which there are at least a first crossing 24, a second crossing 26 and a third crossing 28.

According to the example illustrated in Figure 2, the ceiling wall may also include a fourth crossing 30, a fifth crossing 32, a sixth crossing 34, a seventh crossing 36, an eighth crossing 38 and a ninth crossing 40.

All these crossings are formed by a circular cylinder 78, that is to say a portion of tube, which crosses right through the ceiling wall 6, so that a first end of this cylinder 78 extends in the internal volume of the tank and that a second end of this cylinder extends outside the internal volume of the tank, in particular in its external environment.

As illustrated in this figure 2, the first crossing 24 and the second crossing 26 are aligned on a first straight line 42, the latter passing through a center of these two crossings. In a comparable manner, the first crossing 24 and the third crossing 28 are aligned on a second straight line 44, the latter passing through a center of these two crossings.

The first straight line 42 and the second straight line 44 intersect at the center of the first crossing 24. More precisely and according to the example illustrated here, the first straight line 42 and the second straight line 44 are orthogonal. In general, the first straight line 42 and the second straight line 44 intersect at a single point.

The first crossing 24 and the second crossing 26 have a diameter of between 611 and 1100mm. According to the example illustrated in Figure 2, the diameter of the first bushing 24 is equal to 830mm while the diameter of the second bushing 26 is equal to 1100mm.

Between each of these crossings, the waterproof membrane of the ceiling wall comprises the plurality of waves referenced 16, 18. These waves extend in a rectilinear manner and are gathered in series: a series of first waves 16 and a series of second waves 18. The first waves 16 extend parallel to the first direction 46 while the second waves extend parallel to the second direction 48, the first direction 46 and the second direction 48 being secant and advantageously perpendicular.

According to the invention, the waterproof membrane 10 comprises at least one first corrugation 16 which extends uninterruptedly between the first crossing 24 and the second crossing 26. In the example illustrated in FIG. 2, the waterproof membrane 10 comprises two first waves 16 which extend uninterruptedly between the first crossing 24 and the second crossing 26, but the advantage procured by the invention is obtained from the presence of a single first wave 16.

The waterproof membrane 10 comprises at least two second corrugations 18 which extend uninterruptedly between the first crossing 24 and the third crossing 28. In the example illustrated in FIG. 2, the waterproof membrane 10 comprises three second corrugations 18 which are extend uninterruptedly between the first crossing 24 and the third crossing 28, but the advantage provided by the invention is obtained from the presence of two second waves 18.

The longitudinal movements of the ship can be greater than the lateral movements, which is why the invention provides for a greater number of uninterrupted waves which extend transversely than longitudinally.

The uninterrupted character of a wave located between two crossings is considered as such as soon as it is straight at least between these crossings.

Between these crossings, the distance which separates the first two uninterrupted waves 16 or two second uninterrupted waves from these three uninterrupted waves 18 is between 300 and 500 mm. According to the example illustrated here, this distance is equal to 340mm.

The fourth crossing 30 is arranged at the intersection of a third straight line 50 with a fourth straight line 52 perpendicular to the third straight line 50, this third straight line 50 being parallel to the first straight line 42, while the fourth straight line 52 is parallel to the second line 44. The first, second, third and fourth crossings are thus arranged at the four corners of a square. The waterproof membrane comprises three second uninterrupted waves 18 which extend between the second crossing 26 and the fourth crossing 30. By elsewhere, the waterproof membrane comprises four first uninterrupted waves 16 which extend between the third crossing 28 and the fourth crossing 30.

The fifth crossing 32 is arranged at the intersection of the fourth straight line 52 with a fifth straight line 54 which is perpendicular to this fourth straight line 52, this fifth straight line 54 being parallel to the first straight line 42. The waterproof membrane comprises three second uninterrupted waves 18 which extend between the second crossing 26 and the fifth crossing 32.

The sixth crossing 34 is arranged at the intersection of the second straight line 44 with the fifth straight line 54 which is perpendicular to this second straight line 44. The first, second, fifth and sixth crossings are thus arranged at the four corners of a square. The waterproof membrane comprises four first uninterrupted waves 16 which extend between the fifth via 32 and the sixth via 34. Furthermore, the waterproof membrane 10 comprises three second uninterrupted waves 18 which extend between the sixth via 34 and the first via 24.

The waterproof membrane of the ceiling wall is pierced with the eighth crossing 38. The latter is arranged at the intersection of the first straight line 42 with a sixth straight line 56 which is perpendicular to this first straight line 42, this sixth straight line 56 being parallel to the second line 44. The sealed membrane comprises two first uninterrupted waves 16 which extend between the first crossing 24 and the eighth crossing 38. This eighth crossing 38 has a diameter of between 611mm and 1100mm, for example equal to 830mm.

The seventh crossing 36 is arranged at the intersection of the fifth straight line 54 with the sixth straight line 56 perpendicular to this fifth straight line 54. The first, sixth, seventh and eighth crossings are thus arranged at the four corners of a square. The waterproof membrane comprises three second uninterrupted waves 18 which extend between the seventh crossing 36 and the eighth crossing 38. Furthermore, the waterproof membrane comprises four first uninterrupted waves 16 which extend between the sixth crossing 34 and the seventh crossing 36 .

The ninth crossing 40 is placed at the intersection of the third straight line 50 with the sixth straight line 56 which is perpendicular to this third straight line 50. The first, third, ninth and eighth crossings are thus placed at the four corners of a square. The waterproof membrane comprises four uninterrupted first waves 16 which extend between the third crossing 28 and the ninth crossing 40. Furthermore, the waterproof membrane comprises three second uninterrupted 18 waves which extend between the eighth crossing 38 and the ninth crossing 40.

The waterproof membrane described above is adapted to allow a loading/unloading tower to pass which comprises at least one mast which crosses the ceiling wall 6 passing through at least one of the crossings referenced 24, 26, 28, 30, 32, 34, 36, 38 or 40 and which extends in the volume of the tank to the bottom wall. This loading/unloading tower is for example a tripod consisting of three masts, a first rear mast passing for example through the fifth crossing 32, a second rear mast passing through the seventh crossing 36 and a front mast passing through the third crossing 28. Any of these masts can be the pipe 102 described in connection with Figure 1.

As visible in Figures 2 to 4, there are first waves 16 and second waves 18 whose path is secant of a crossing. In such a case, basing is interrupted at the right of the crossing. According to an interesting aspect of the invention, a first wave 16 and a second secant wave 18 at the level of the same crossing are connected to each other by at least one deflection wave 60. Such a deflection wave 60 is rectilinear and secant both of the first direction 46 and of the second direction 48 along which the first wave 16 and the second wave 18 respectively extend. direction of extension 46 of the first wave 16 form a first angle a which is complementary to a second angle P formed between the direction of extension 66, 68 of the deflecting base 60 and a direction of extension 48 of the second wave 18. The first angle a and the second angle P can each be equal to 45°.

The deflection wave 60 is arranged close to the crossing concerned and it forms part of a closing partition 62 which is bordered on two sides by two base plates 12, and by the crossing along the arc of a circle. In the case of FIG. 2, around each crossing, the waterproof membrane comprises four closing partitions 62, which each comprise at least one deflection wave 60, arranged around the crossing, so as to connect the circular cylinder materializing the crossing to the base plates 12. Each closing partition 62 closes a quarter of the opening between the bushing and the base plates 12 which surround this bushing.

A flange 76 of section in the shape of an “L” can also be arranged between these four closing partitions 62 and the cylinder 78 which forms the crossing concerned. In such a case, the collar is attached by being in direct contact with the circular cylinder 78 forming the crossing and the four closing partitions 62 which surround it, for example by being welded to these constituent elements of the waterproof membrane 10. Such a collar is for example a ring one-piece whose cross section in a radial direction and an axial direction of the crossing follows an "L" shaped profile.

According to another embodiment, the closure partition(s) 62 may comprise a bent edge which comes into direct contact with the circular cylinder which forms the crossing, being welded to the latter. The folded edge makes it possible to attach the closing partitions 62 directly to the crossing, without adding an additional element. A folded edge is a slice of the closing partition 62 which borders the crossing, such a folded edge extending in a direction perpendicular to a main plane of extension of the waterproof membrane while being directed towards the inside of the tank.

The deflecting wave 60 and the closing partition 62 which carries it are a metal part of the same material as that which forms the base plate 12. View in a section passing through a radial and axial plane of the bushing, deflecting base 60 has a section similar to that of a wave, that is to say a concave shape with an apex that protrudes towards the inside of the tank.

In FIGS. 3 and 4, the deflecting base 60 is connected in a sealed manner with the first wave 16 or the second wave 18 by means of a cap 64 arranged astride one end of the deflecting base and on one end of the first wave 16 or the second corrugation 18. This cap 64 is welded to the flat part of the base plate, to a flat portion of the closing partition 62 and against the corrugations, following their concave profile. For a deflecting wave 60, there are thus two caps 64: a first cap welded to the deflecting base 60 and to the first wave 16 and a second cap welded to the deflecting base 60 and to the second wave 18.

In Figure 3, there is illustrated the case of a crossing with a diameter greater than 611mm, as is the case with the first, second and eighth crossings detailed above. In such a situation, the waterproof membrane comprises a maximum of eight deflection waves 60 distributed around the bushing. These deflecting waves 60 are gathered in pairs, the latter being opposite to each other with respect to the center of the crossing. Each deflection wave 60 of the same pair extends along parallel and distinct directions of extension, referenced 66 and 68 in FIG. 3. At least a first deflection wave 60a and a second deflection wave 60b are arranged such that the first deflecting wave 60a extends between the second deflecting wave 60b and the bushing concerned. A distance between a peripheral edge of the bushing in question and the direction of extension of the offset base 60 farthest from the bushing is a maximum of 320 mm.

Figure 4 illustrates the case of a bushing with a diameter of less than 610mm, as is the case for the third to the seventh bushings and the ninth bushing, as detailed in Figure 2. In a In such a situation, the waterproof membrane comprises a maximum of four deflection waves 60 distributed around each crossing, each of these deflection waves 60 being sealed at their ends by the cap 64.

The invention thus achieves the goal it had set itself by proposing a tank provided with a ceiling wall complying with design rules which are adapted to the presence of several crossings grouped together within a restricted perimeter. of the waterproof membrane, in particular a cover or an area of the ceiling wall dedicated to penetrations.

The invention cannot however be limited to the means and configurations exclusively described and illustrated and also applies to all means or configurations, equivalents and to any combination of such means or configurations.

Claims

1. Tank (2) for transporting and/or storing a liquefied gas comprising at least a bottom wall (20), a ceiling wall (6) and side walls (21) connecting the bottom wall (20 ) to the ceiling wall (6), at least the ceiling wall (6) comprising at least one waterproof membrane (10) which comprises at least a series of first waves (16) secant of a series of second waves (18 ), the ceiling wall (6) comprising at least a first via (24), a second via (26) and a third via (28), the first via (24) and the second via (26) being aligned on a first straight line (42) while this first crossing (24) and the third crossing (28) are aligned on a second straight line (44) secant to the first straight line (42), the waterproof membrane (10) comprising at least a first wave (16) uninterrupted between the first via (24) and the second via (26), as well as at least two second waves (18) uninterrupted between the first via (24) and the third via (28).

2. Tank according to the preceding claim, wherein the sealed membrane (10) comprises at least two first waves (16) uninterrupted between the first crossing (24) and the second crossing (26), as well as at least three second waves ( 18) uninterrupted between the first crossing (24) and the third crossing (28).

3. Tank according to any one of the preceding claims, comprising a loading/unloading tower which comprises at least one mast which passes through the ceiling wall (6) passing through at least one of the crossings (24, 26, 28).

4. Tank according to any one of the preceding claims, in which a distance separating the first waves (16) located between the first crossing (24) and the second crossing (26) and measured perpendicular to at least one of these first waves ( 16) is between 300 and 500mm.

5. Tank according to any one of the preceding claims, in which a distance separating the second waves (18) located between the first crossing (24) and the third crossing (28) and measured perpendicular to at least one of these second waves ( 18) is between 300 and 500mm.

6. Tank according to any one of the preceding claims, in which a first wave (16) and a second wave (18) secant at the level of a crossing (24, 26, 28) are connected to each other. by at least one deflection wave (60).

7. Tank according to the preceding claim, comprising a maximum of four deflection waves (60) distributed around the crossing (24, 26, 28) when the latter has a diameter less than 610mm and preferably between 160 and 610mm.

8. Tank according to claim 6 or 7, comprising a maximum of eight deflection waves (60) distributed around the crossing (24, 26, 28) when the latter has a diameter greater than 610 mm and preferably between 611 and 1100mm.

9. Tank according to the preceding claim, in which the eight deflecting waves (60) form four pairs of two deflecting waves (60), each deflecting wave (60) of the same pair extending in directions of extension (66, 68) parallel and distinct.

10. Tank according to any one of claims 6 to 9, in which a direction of extension (66, 68) of the base deflecting (60) and a direction of extension (46) of the first wave (16) form a first angle (a) complementary to a second angle (P) formed between the direction of extension (66, 68) of the deflecting base (60) and a direction of extension (48) of the second corrugation (18) .

11. Tank according to any one of the preceding claims, in which the ceiling wall (6) comprises a main portion (70) and a lid (72) which closes an opening made in the main portion (70), the lid ( 72) comprising at least a portion of the waterproof membrane (10) which comprises the series of secant first waves (16) of the series of second waves (18), the cover (72) comprising the crossings (24, 26, 28) , the first crossing (24) and the second crossing (26) being aligned on the first line (42), the first crossing (24) and the third crossing (28) being aligned on the second line (44) secant of the first line (42), the sealed membrane portion of the cover (72) comprising at least the first uninterrupted wave (16) between the first crossing (24) and the second crossing (26), as well as at least the two second waves (18 ) uninterrupted between the first crossing (24) and the third crossing (28).

12. Tank according to the preceding claim, wherein the cover (72) and the main portion (70) of the ceiling wall (6) are coplanar.

13. Tank according to claim 11, in which the ceiling wall (6) comprises a coaming (74) formed around the opening and which protrudes from the main portion (70) of the ceiling wall (6), the cover (72) being arranged at a free end of the coaming (74).

14. Vessel (1) for transporting and/or storing liquefied gas comprising at least one tank (2) according to any one of the preceding claims, the vessel comprising a double hull (100) part of which forms a load-bearing structure. the bowl (2).