FR3041603A1 - SEALED AND INSULATED TANK DISPOSED IN A SHIP - Google Patents

Abstract

Vessel comprising: - a tank (3), - a pump (7) comprising a pump head (8) arranged near a bottom wall (5) of the tank (3), - a container (9), the pump head (8) being housed in the container (9), the container (9) having a passage (15) placing the interior of the vessel in communication with the interior of the container, a movable valve (16) being arranged obstructing the passage (15) when a pressure differential exerted on the valve (16) between the outside of the container (9) and the inside of the container (9) is below a determined positive threshold and releasing the passage (15) ) when said pressure differential is greater than said threshold, wherein the valve (16) has a beveled lower surface (23) cooperating with a valve seat having a complementary bevelled surface (24) arranged to cut the communication between the interior of the the tank (3) and the interior of the container (9) via the passage (15) when that they cooperate.

Description

TECHNICAL FIELD The invention relates to the field of sealed and insulating tanks arranged in floating structures, in particular for the storage and / or transport of a cold product, especially a liquefied gas, for example liquefied natural gas (LNG) which contains a high methane content and has a liquid state at about -162 ° C at atmospheric pressure.

Technological background

In the membrane chamber technique, the internal surfaces of a bearing structure such as the inner shell of a double-hulled ship are lined with a multilayer structure comprising two thin alternating sealing membranes with two layers of thermal insulation which serve both to limit the heat flow through the tank wall and to structurally support the waterproof membranes. Other techniques use thick plates with an outer insulation.

In order to maximize the operating efficiency of such a tank, it is desirable to optimize the useful volume of cargo that can be loaded into the tank and to discharge from the tank. Similarly, in order to allow the use of LNG for the propulsion of the vessel when the tanks are almost empty, it is desirable to be able to pump the LNG while minimizing the amount of LNG present in the tank necessary for the propulsion of the ship. However, the use of an unloading pump drawing the liquid to the top of the tank requires to maintain a certain height of liquid at the bottom of the tank, otherwise the suction member of the pump enters into communication with the gas phase, which defuses and / or degrades the pump. Given the swelling of the cargo by the swell, the necessary liquid height can hardly be minimized.

EP1314927 publication envisages placing the suction member of the pump in a collection chamber located near the bottom of the tank. This capture chamber is equipped with non-return valves to allow the liquid contained in the tank to enter the chamber and to keep the suction member in a volume of liquid gas when the LNG in the tank reaches a level below the level of said capture chamber. summary

An idea underlying the invention is to minimize the minimum level of liquid in the tank necessary for the proper functioning of the pump simply, safely and effectively.

According to one embodiment, the invention provides a vessel comprising: a thermally insulated tank intended to contain a cold liquid product, a pump comprising a pump head intended to suck up the cold liquid product contained inside the thermally insulated tank , said pump head being arranged near a bottom wall of the thermally insulated tank, a container located inside the thermally insulated tank, the pump head being housed in the container, the container having a bottom turned towards a bottom wall of the tank and provided with a passage communicating the interior of the container with the outside of the container, an upper portion of the container opposite the bottom of the container having an opening in communication with the inside of the tank , the container further comprising at least one movable valve arranged to cooperate with a valve seat carried by the bottom of the r container, the valve being able to obstruct the passage of the bottom of the container when a pressure differential exerted on the valve between the outside of the container and the inside of the container is less than a determined positive threshold and release the passage when said differential pressure is greater than said threshold, wherein the valve has a beveled lower surface vis-à-vis the valve seat, said valve seat having a bevelled surface vis-à-vis the bevelled surface of the valve, the surface beveled valve and the beveled surface of the valve seat being complementary and able to come into sealing contact all around the passage of the bottom of the container to cut the communication between the inside of the tank and the interior of the container via the passage.

Such a valve has with the valve seat a large contact surface when the valve is in abutment against the valve seat. This important contact surface ensures a good seal and thus allows good retention of the liquid contained in the container.

In embodiments, such a ship may have one or more of the following features.

According to one embodiment, the container comprises a guide system of the valve adapted to guide the valve in a direction parallel or oblique to the direction of gravity so that the valve closes by gravity.

According to one embodiment, the guide system comprises a plurality of guide rods developing from the bottom of the container towards the inside of the container, the valve having a plurality of guide portions slidingly cooperating with a respective guide rod, one end of each guide rod opposite the bottom of the container having a shoulder, each guide portion of the valve being inserted in a sliding direction along the corresponding guide rod between the shoulder of said guide rod and the bottom of the container so as to limit the movement of said guide portions of the valve in the container.

According to one embodiment, the guide system comprises a plurality of guide rails, each guide rail developing from the bottom of the container towards the interior of the container, the valve comprising a plurality of tabs, each tab being housed in a housing. said respective guide rails and guided in displacement by said respective guide rail, each guide rail further comprising at an end opposite the bottom of the container an upper wall adapted to limit in displacement the corresponding tab of the corresponding valve housed in said rail of guide.

According to one embodiment, the guide rail has two side walls developing parallel to each other from the bottom of the container towards the inside of the container, the flap tabs being housed in the guide rail between the two. side walls so as to block the lateral displacement of the valve.

The container can have many shapes. According to one embodiment, the container is cylindrical in shape.

According to one embodiment, the entire upper section of the container opposite the bottom of said container is open.

The valve and the passage can have many forms. According to one embodiment, the valve and the passage in the bottom of the container are circular in shape. In one embodiment, the valve is disk-shaped.

According to one embodiment, the valve is in the form of a blade.

According to one embodiment, the valve and the passage in the bottom of the container are of rectilinear shape.

According to one embodiment, the valve and the passage in the bottom of the container are in the shape of a circular arc.

According to one embodiment, the flap tabs are located at opposite longitudinal ends of the valve.

The valve can be made in many materials compatible with LNG. Preferably, such materials compatible with LNG have a lower density than metals to minimize the opening pressure of the valve. According to one embodiment, the valve comprises teflon. More particularly, according to different variants, the valve is entirely made of Teflon or has a Teflon coating.

According to one embodiment, the bottom of the container comprises a plurality of passages placing in communication the interior of the container and the outside of the container, the container further comprising a plurality of movable flaps arranged to cooperate with a respective valve seat worn. by the bottom of the container around each of the passages, each valve being adapted to obstruct one of the passages of the bottom of the container when a pressure differential exerted on said valve between the outside of the container and the interior of the container is lower than at a determined positive threshold and release said passage when said pressure differential is greater than said threshold.

According to one embodiment, at least one guide rail is arranged between two passages of the bottom and has a first portion which receives a first tab of a first valve cooperating with a first valve seat of a first of said passages and a second part which receives a second leg of a second valve cooperating with a second valve seat of a second of said passages so that the guide rail moves the first and second valves.

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

According to one embodiment, the invention also provides a transfer system for a cold liquid product, the system comprising the abovementioned vessel, insulated pipes arranged to connect the vessel installed in the hull of the vessel to a floating storage facility. or terrestrial and a pump for driving a flow of cold liquid product through the insulated pipelines from or to the floating or land storage facility to or from the vessel vessel.

Some aspects of the invention start from the idea of minimizing the amount of liquid to be kept in the tank in order to keep the pump head immersed and avoid a defusing of the pump. Some aspects of the invention start from the idea of housing the pump head in a container having a good seal. Some aspects of the invention start from the idea of ensuring a good guiding movement of the valves, in particular when closing said valves by cooperation with a respective valve seat. Certain aspects of the invention start from the idea of providing means for guiding the alternative valves. Some aspects of the invention start from the idea of minimizing the number of guide systems necessary for moving guidance of a plurality of valves.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood, and other objects, details, features and advantages thereof will become more clearly apparent from the following description of several particular embodiments of the invention, given solely for the purposes of the invention. illustrative and not limiting, with reference to the accompanying drawings. FIG. 1 represents a partial view in longitudinal section of a LNG tanker having a tank in which an unloading pump carried by a tripod mast and having a pump head located near a bottom wall of the tank is arranged. . Fig. 2 is a schematic perspective view of the pump head of Fig. 1 housed in a liquid holding container according to a first embodiment of said container and illustrating attachment of said container to the pump head. FIG. 3 represents a view from above of the pump head and the container of FIG. 2 illustrating the attachment of the container to the pump head, as well as the bottom of the container comprising communication valves between the inside of the container and the outside of the container. • Figure 4 shows a partial sectional view of the bottom of the container illustrating a valve of Figure 3 in an open position. • Figure 5 shows a partial sectional view of the bottom of the container illustrating a valve of Figure 3 in a closed position. FIG. 6 represents a perspective view of a second embodiment of the container in which the valves have the form of flat and rectilinear blades distributed around the pump head. • Figure 7 shows a detail view of a valve of Figure 6 cooperating with a valve seat and a guide system. FIG. 8 represents a perspective view in longitudinal section of the valve and of the guiding system of FIG. 7; FIGS. 9 and 10 show cross-sectional views of the valve and the guiding system of the second embodiment respectively; in a closed position and in an open position of the valve. • Figure 11 shows a top view of a container according to a third embodiment. • Figure 12 shows a longitudinal sectional view of the valves of Figure 11 cooperating with a guide system common to two adjacent valves. • Figure 13 shows a schematic schematic representation of a tank LNG tank and a loading / unloading terminal of this tank.

Detailed description of embodiments

In the description below, there will be described several containers that can be used at the pump head in a storage tank and / or LNG transport. The bottom wall of the tank designates a wall, preferably generally flat, located in the bottom of the tank relative to the earth's gravity field. The general geometry of the tank can also be of different types. Polyhedral geometries are the most common. A cylindrical, spherical or other geometry is also possible.

The walls of the tank are for example formed by a multilayer structure attached to supporting walls and including two alternating waterproof membranes with two thermally insulating barriers. Since there are many known techniques for making these multilayer structures, the description below will be limited to a brief description of the tank and describe in more detail the structure of the elements cooperating with the pump head in the tank. Other techniques use thick plates with an outer insulation.

Referring to Figure 1, a vessel 1 comprises a double shell forming a supporting structure 2 on which are mounted walls of a vessel 3. Each vessel wall 3 comprises a multilayer structure successively including a secondary insulating barrier fixed on the structure carrier 2, a secondary waterproof membrane supported by the secondary insulating barrier, a primary insulating barrier covering the secondary waterproof membrane and a primary waterproof membrane supported by the primary insulating barrier.

A tripod mast 4 is fixed near a transverse wall 5 of the tank 3. This tripod mast 4 is preferably substantially centered at the mid-width of the ship. The tripod mast 4 develops from a bottom wall 5 of the tank to an upper wall 6 of the tank 3. The tripod mast 4 supports one or more pump (s) 7 whose pump head 8 is located near of the bottom wall 5 of the r * ii \ / a * 3 Hoc oana jicafinnQ making the fnnmno ff a cwcfomo rla moni ifontinn vi vb / vv vCii iCUivwuiwi) wi viivi u M "t Ivvv mu ^ / ui ifu wu W Ci iv iv u IV IV IV IV lu lu lu lu lu lu lu lu de de de de de de (Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce Ce contained in the tank 3 via the pump 7.

During an unloading of the LNG tank or in the case of the use of the LNG contained in the tank to supply gas to the engines of the ship, the pump 7 is activated in order to suck up the LNG contained in the tank 3 via 8. However, in the case of a vessel whose engines are fed with LNG from the tank and making a return voyage, only a liquid LNL bead is kept in the tank to feed the tank. ship engines on this return trip. However, due to roll movements that can be caused by the sea on which the ship 1 sails during this return trip, the level of LNG in the tank 3 at the pump head 8 may vary. Thus, when the tank 3 is almost empty, the movements of the ship 1 due to pitch and roll can not guarantee that the pump head 8 is immersed continuously in the LNG. In order to keep the pump head 8 immersed in the LNG despite the movements of LNG in the tank 3, the pump head 8 is housed in a receptacle 9 as illustrated in FIGS. 2 to 11. Such a receptacle 9 is fixed on and carried by the pump head 8 in the tank 3 above the bottom wall 5 of the tank 3.

FIG. 2 represents a schematic perspective view of the pump head of FIG. 1 housed in a liquid-holding container 9 according to a first embodiment of the container 9 and illustrating said container 9 and the fastening of said container 9 to the head pump 8.

The container 9 illustrated in Figure 2 has a circular cylindrical shape. The container 9 has a bottom 10 (see Figure 3) of circular shape developing parallel to the bottom wall 5 of the vessel 3 above it. Preferably, the distance between the bottom of the container and the bottom wall of the tank is between 25 and 150 mm, the maximum value up to 250 mm. A circular side wall 11 is developed from the bottom 10 of the container 9 to the upper wall 6 of the tank 3, that is to say away perpendicularly from the bottom wall 5 of the tank 3, it is in a direction parallel to Earth's gravity.

The upper section of the container 9 does not have a lid wall so that the upper end of the container 9 opposite the bottom 10 of the container is open. Thus, when the level of LNG in the tank 3 exceeds the container 9, the container 9 is filled with LNG.

An inner face 12 of the wall 11 has two lugs 13 protruding radially inwardly of the container 9. These lugs 13 develop from diametrically opposite regions of the inner face 12. The pump head 8 has two shoulders 14 protruding radially outward, that is to say in the direction of the inner face 12 of the container. The legs 13 of the container 9 are fixed on the shoulders 14 of the pump head 8 by any suitable means such as using screws and nuts, a weld or the like. Thus, the container 9 is fixed to the pump head 8 and said pump head 8 is housed inside said container 9. Preferably, the pump head 8 is centered in the container 9.

3 shows a top view of the pump head 8 and the container 9 illustrating the attachment of the container 9 to the pump head 8 and the bottom 10 of the container 9 having valves 16 for communication between the inside of the container 9 and the outside of the container 9.

In the first embodiment illustrated in Figures 2 to 5, the container 9 has three passages 15 (see Figures 4 and 5) through the bottom 10 of the container 9. These passages 15 are evenly distributed around the pump head 8 On the other hand, the container 9 has three valves 16 intended to release or obstruct the passages 15 as a function of the pressure exerted by the LNG contained in the tank 3 as explained hereinafter. Each valve 16 has a diameter greater than the diameter of the passage 15 with which it cooperates. Each valve 16 is also coaxial with said passage 15 with which it cooperates. The valves 16 have a circular shape.

Each passage 15 is surrounded by an insert 17 mounted on the bottom 10 of the container. These inserts 17 have a central through opening extending the corresponding passage 15 of the container 9. Moreover, these inserts 17 each form a valve seat cooperating with a respective valve 16, as explained below with reference to FIGS. These inserts 17 are fixed to the bottom 10 of the container 9 by any suitable means, for example using screws and nuts or by welding.

Figures 4 and 5 illustrate the operation of a valve 16 as shown in Figure 3.

An end 18 of the pump head 8 through which the LNG is sucked during unloading of the tank 3 is preferably located near the bottom 10 of the container 9 to be kept immersed in the LNG contained in the container 9 .

The valve 16 is movable in the container along an axis of displacement 19 perpendicular to the bottom 10 of the container 9 and, preferably, parallel to the Earth's gravity. For this purpose, a guiding system makes it possible to guide and limit the displacement of the valve 16. In the embodiment illustrated in FIGS. 2 to 5, the guiding system comprises four pins 20 fixed to the bottom 10 of the container 9 (of which only three are illustrated in Figures 4 and 5). Each pin 20 develops from the bottom 10 of the container 9 towards the inside of the container 9 parallel to the axis 19 of displacement of the valve 16. These pins 20 are fixed by any means adapted to the bottom 10 of the container 9, for example by welding. Each pin 20 passes through the insert 17 which includes four holes ad hoc. One end 21 of each pin 20 opposite the bottom 10 of the container 9 has a threaded reduced dimension section 21.

A peripheral edge of the valve 16 has four bores 22. Each bore 22 is traversed by a corresponding pin 20. Thus, the valve is guided in displacement by sliding its peripheral edge along the pins 20. A nut 32 is screwed onto the end 21 of each pin 20. This nut 32 forms a shoulder blocking the movement of the valve 16 along the axis 19 between said end 21 and the insert 17.

The valve 16 is movable in the container under the effect of its own weight and, if appropriate, a differential pressure exerted on the valve 16 between the inside of the container 9 and the outside of the container 9. Thus, when the container 9 is surrounded by LNG present in the tank 3, without the LNG protruding from the upper end of the container 9 and thus discharging into the container 9 by said open upper end of the container 9, the valve 16 is subject on the one hand to an internal pressure caused by the LNG present in the container 9 and, on the other hand, to an external pressure caused by the LNG which is in contact with the valve 16 and is present in the tank 3 by surrounding the 9. The valve 16 is therefore subjected to a pressure differential that allows to push the valve 16 away from the insert 17, and therefore the valve seat. This differential pressure allows! opening of the valve when the following equation is fulfilled;

Pcuve * $ lower "I" Parchimede ^ P bowl * Upward "h P OÏds flap

In which Pcuve represents the pressure exerted by the LNG contained in the tank 3 out of the container 9 on the valve 16, S inferior represents the surface of the valve 16 in contact with the LNG contained in the tank 3 out of the container 9, Parchimède represents the thrust of Archimedes exerted on the valve 16 by the LNG contained in the tank 3 out of the container 9, Gammaie represents the pressure exerted by the LNG contained in the container 9 on the valve 16, Ssuperior represents the upper surface of the valve 16 on which the pressure of the LNG contained in the container 9 is exerted, and Weightapet represents the weight of the valve 16. Typically, this equation reflects the fact that the opening of the valve 16, that is to say its distance from the insert 17 forming the valve seat, depends on the difference in height between the LNG contained in the tank 3 out of the container 9 and the LNG contained in the container 9.

Conversely, when the container 9 is not surrounded by LNG, the only pressure exerted on the valve 16 is that exerted by the LNG contained in the container 9. Under the effect of the gravity and the pressure exerted by the LNG contained in the container 9, the valve 16 is pushed back to the bottom 10 of the container 9 and cooperates with the valve seat to obstruct the passage 15 in the bottom 10 of the container 9.

The valve 16 is made of a material with a lower density than the stainless steel type metals to limit the opening pressure and compatible with LNG. For example, preference will be given to plastic materials, preferably polytetrafluoroethylene also called teflon for example in the form of a teflon coating or solid material. Thus, the valve 16 is light and the weight of the valve only slightly disturbs its opening under the effect of the pressure exerted by the LNG contained outside the container 9 in the tank 3. In addition, the Teflon coating has good properties sliding to the valve 16 facilitating its movement in the container 9.

As illustrated in FIGS. 4 and 5, the lower surface of the valve 16 comprises a bevelled portion 23. Thus, the valve 16 has a frustoconical portion whose smallest diameter is located near the bottom 10 of the container

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Furthermore, the insert 17 forming the valve seat also comprises a tapered portion 24. The tapered portion 24 of the insert 17 is complementary to the tapered portion 23 of the valve 16, said tapered portion 24 of the insert 17 having a Minimum diameter near the bottom 10 of the container 9. Typically, the tapered portion 24 of the insert forms the valve seat with which the valve 16 cooperates to obstruct the passage 15. Thus, in the case of a tapered portion 23 of the valve 16 forming an angle of 45 ° with the bottom 10 of the container 9, the tapered portion 24 of the insert 17 also has an angle of 45 ° with the bottom of the container.

These bevelled portions 23 and 24 provide a large contact surface between the valve seat and the valve 16 thus ensuring a better seal to the container 9 when the valve 16 obstructs the passage 15. In addition, the beveled shape 24 of the guide valve seat the displacement of the valve 16 when it moves towards the bottom 10 of the container to obstruct the passage 15.

When the LNG contained in the tank 3 surrounds the container or is moved to the container due to the pitch and roll of the ship 1, the pressure exerted by the LNG contained in the tank 3 of the valve 16 allows to push back the valve 16 out of the valve seat. Therefore, the passage 15 is no longer obstructed and the LNG present in the tank 3 enters the container 9 through the passage 15 located in the bottom 10 of the container. Conversely, when the LNG contained in the tank 3 does not surround the container and does not exert sufficient pressure on the valve 16 to push it out of the valve seat, the LNG contained in the container 9 is retained in said container by the obstruction of the passage 15 by the valve 16 cooperating sealingly with the insert forming the valve seat.

FIGS. 6 to 10 illustrate a second embodiment of the valves 16 as illustrated in FIGS. 3 to 5. In this second embodiment, the elements that are identical or fulfill the same function as in the first embodiment bear the same increased reference of 100.

In the second embodiment, the valves 116 are made in the form of straight blades. In the variant illustrated in FIG. 6, the bottom 110 of the tank 109 comprises four rectilinear passages 115 cooperating with four valves 116, the passages 115 being equi-distributed around the pump head 108.

Each passage 115 is surrounded by an insert 117 forming a valve seat.

As illustrated in Figures 9 and 10, the lower face of the valve 116 has a bevelled surface 123 in a longitudinal direction of said valve 16. Thus, the valve 116 has a trapezoidal section. Similarly, each insert 117 forming the valve seat has a beveled surface 124 complementary to the beveled surface 123 of the valve 116. Thus, as for the first embodiment, the valve 116 is guided at the end of closing movement by cooperation In addition, as in the first embodiment, the contact surface between the valve 116 and the valve seat formed by the insert 117 is important, thus avoiding LNG leakage from the container 109 when the LNG present in the tank 103 out of the container 109 is not in contact with the lower surface of the valve 116.

In this second embodiment, the displacement guide system of the valve 116 is formed by a guide rail 125 located on the bottom 110 of the container 109. For each passage 115, a guide rail 125 is mounted on the bottom 110 of the container at opposite longitudinal ends of said passage 115. Each guide rail 125 has a U-shaped profile. The guide rail 125 has two side walls 126 which develop from the bottom 110 of the container 109 towards the interior of the container 109 perpendicularly to said bottom wall 110 on either side of the insert 117. These walls side 126 form the branches of the profile in "U". The base of the profile "U" is formed by an upper wall 127 connecting the ends of the side walls 126 opposite the bottom 110 of the container 109. This upper wall 127 is parallel to the bottom 110 of the container 109

The guide rail 125 is fixed on the bottom 110 of the container 109 by means of a stud 128 fixed to the bottom 110 of the container 109. The stud 128 develops from the bottom 110 of the container 109 and passes through the upper wall 127 of the guide rail 125. An upper end of the pin 128 opposite the bottom 110 of the container 109 includes a nut 129 to fix the guide rail 125. Furthermore, a wedge 130 in the shape of "L" is inserted between the upper wall 127 and the insert 117 forming the valve seat. This shim 130 prevents the deformation of the guide rail 125 when the nut 129 is screwed onto the stud 128.

Both the shim 130 and the insert 117 have an orifice allowing the stud 128 to pass from the bottom 110 of the container 109, as illustrated in FIG. 7.

A longitudinal end of the valve 116 forms a tab 131 housed in the guide rail 125. This tab 131 is locked in displacement in a direction transverse by the side walls 126 of the guide rail 125. Similarly, this tab 131 is movable on the move in a direction parallel to the axis 119 of displacement of the valve 116 between firstly the insert 117 forming the valve seat and, secondly, the upper wall 127 of the guide rail 125. Finally, the tab 131 is locked in displacement in a longitudinal direction of the valve 116 by abutment on the shim 130 of the guide rail 125 as illustrated in Figure 8. Thus, each valve 116 is guided in displacement in the direction 119 perpendicular to the bottom 110 of the container 109 by cooperation between the lugs 131 housed in the corresponding guide rails 125 and said guide rails 125.

In the embodiment illustrated in Figures 6 to 10, the tabs 131 have a section identical to the section of the rest of the valve 116. Thus, the valve 116 is simple to perform and does not require special embodiment of the tabs 131. However , the tabs 131 could have any other form adapted to cooperate with a guide rail. Figures 9 and 10 illustrate the blocking movement along the axis 119 of displacement of the valve 116 of a tab 131 by the upper wall 127 of the guide rail 125. These Figures 9 and 10 also illustrate the cooperation between the bevelled surfaces 123 and 124 ensuring a good seal of the container 9 when the valve 116 cooperates with the insert 117 and an effective displacement guide when the valve 116 moves towards the valve seat formed by the insert 117.

In a variant not shown, the passages passing through the bottom of the container and the valves are circular in a manner similar to the first embodiment. However, in this variant, each valve has a plurality of tabs protruding radially outwardly from its peripheral edge. A plurality of guide rails similar to the guide rails of the second embodiment are fixed on the bottom of the container. Each tab of a valve cooperates with a respective guide rail for moving guide said valve. In another variant, each valve also comprises tabs protruding from its peripheral edge and is guided in displacement by cooperation of bores made in said tabs with pins such as according to the first embodiment.

FIGS. 11 and 12 illustrate a third embodiment of the valves corresponding to a variant of the valves 116 as illustrated in FIGS. 6 to 10. In this third embodiment, the elements that are identical or that fulfill the same function as in the first embodiment embodiment carry the same reference increased by 200.

The third embodiment differs from the second embodiment in that the valves 216 have a shape of circular arcuate blade. As illustrated in Figure 11, the bottom 210 of the container 209 has four valves 216 each forming a circular arc of about 90 °. As for the second embodiment, these valves 216 are equi-distributed around the pump head 208 and cooperate with inserts 217 surrounding passages 215 of the bottom 210 of the container 209 which also have an arcuate shape.

In addition, in this embodiment, one and the same guide rail 225 makes it possible to guide two adjacent valves 216 in displacement. Typically, the same guide rail 225 having a profiled section "U" which blocks in lateral displacement and vertical two adjacent valves 216 similarly to the valves 116 of the second embodiment but one and the same shim 230 in "L" allows blocking two adjacent valves 216 in a circumferential direction, said wedge 230 being interspersed circumferentially between the tabs 231 of said two adjacent flaps.

In a variant not shown, the wedge 230 has a convex shape such as a square or a semi-circle facing the valve 216 and the latter to a complementary concave shape. This wedge shape 230 also makes it possible to guide laterally the vertical displacement of the valve 216 and thus to have a guide rail 225 serving only as a vertical stop.

Referring to Figure 13, a broken view of a LNG tank 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 sealed barrier intended to be in contact with the LNG contained in the tank, a secondary sealed barrier arranged between the primary waterproof barrier and the double hull 72 of the ship, and two insulating barriers arranged respectively between the primary watertight barrier and the secondary watertight barrier and between the secondary watertight barrier and the double hull 72.

In a manner known per se, loading / unloading lines 73 arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a marine or port terminal to transfer a cargo of LNG from or to the tank 71.

FIG. 13 represents an example of a marine terminal comprising a loading and unloading station 75, an underwater pipe 76 and an onshore installation 77. The loading and unloading station 75 is a fixed off-shore installation comprising an arm mobile 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 that can connect to the loading / unloading pipes 73. The movable arm 74 can be adapted to all gauges of LNG carriers . A connection pipe (not shown) extends inside the tower 78. The loading and unloading station 75 enables the loading and unloading of the LNG tank 70 from or to the shore facility 77. liquefied gas storage tanks 80 and connecting lines 81 connected by the underwater line 76 to the loading or unloading station 75. The underwater line 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the onshore installation 77 over a large distance, for example 5 km, which makes it possible to keep the tanker vessel 70 at great distance from the coast during the loading and unloading operations.

In order to generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps equipping the shore 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 not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention. The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim. The use of the indefinite article "a" or "an" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps.

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

Claims (15)

A vessel comprising: a thermally insulated tank (3) for containing a cold liquid product, a pump (7) having a pump head (8, 108) for sucking the cold liquid product contained inside the tank (3) thermally insulated, said pump head (8, 108) being arranged near a bottom wall (5) of the thermally insulated tank (3), a container (9, 109, 209) located inside of the thermally insulated tank (3), the pump head (8, 108) being housed in the container (9, 109, 209), the container (9, 109, 209) having a bottom (10, 110, 210) turned towards a bottom wall of the tank and provided with a passage (15, 115, 215) placing the inside of the container in communication with the outside of the container, an upper portion of the container (9, 109, 209) opposite at the bottom (10, 110, 210) of the container (9, 109, 209) having an opening in communication with the inside of the tank (3), the container ( 9, 109, 209) further comprising a movable valve (16, 116, 216) arranged to cooperate with a valve seat (17, 117, 217) carried by the bottom (10, 110, 210) of the container (9, 109, 209), the valve (16, 116, 216) being able to obstruct the passage (15, 115, 215) of the bottom (10, 110, 210) of the container (9, 109, 209) when a differential of pressure exerted on the valve (16, 116, 216) between the outside of the container (9, 109, 209) and the inside of the container (9, 109, 209) is lower than a determined positive threshold and free the passage ( 15, 115, 215) when said pressure differential is greater than said threshold, wherein the valve (16, 116, 216) has a beveled lower surface (23, 123, 223) opposite the valve seat, said valve seat (17, 117, 217) having a bevelled surface (24, 124, 224) facing the bevelled surface (23, 123, 223) of the valve (16, 116, 217), the bevelled surface (23, 123, 223) of the valve (16, 116, 216 ) and the bevelled surface (24,124, 224) of the valve seat (17, 117, 217) being complementary and sealingly engageable all around the bottom passage (15, 115, 215) (10, 110, 210) of the container (9, 109, 209) to cut the communication between the inside of the tank (3) and the inside of the container (9, 109, 209) via the passage (15, 115, 215). 2. Ship according to claim 1, wherein the container (9, 109, 209) comprises a guide system (25, 125, 225) of the valve (16, 116, 216) adapted to guide the valve (16, 116, 216) in a direction parallel or oblique to the direction of gravity so that the valve closes by gravity. 3. Ship according to claim 2, wherein the guide system (25) comprises a plurality of guide rods (20) developing from the bottom (10) of the container (9) towards the inside of the container (9), the valve (16) having a plurality of guide portions cooperating by sliding with a respective guide rod (20), an end (21) of each guide rod (20) opposite the bottom (10) of the container (9) comprising a shoulder (22), each guide portion of the valve (16) being interposed in a sliding direction (19) along the corresponding guide rod (20) between the shoulder (22) of said rod (20) of guiding and the bottom (10) of the container (9) so as to limit the movement of the valve (19) in the container (9). The vessel according to claim 2, wherein the guide system comprises a plurality of guide rails (125, 225), each guide rail (125, 225) developing from the bottom (110, 210) of the container (109). 209) inwardly of the container (109, 209), the valve (116, 216) having a plurality of tabs (131, 231), each tab (131, 231) being accommodated in one of said guide rails (125). , 225) and guided in movement by said respective guide rail (125, 225), each guide rail (125, 225) further comprising at an end opposite the bottom (110, 210) of the container (109, 209). an upper wall (127, 227) adapted to limit in displacement the corresponding lug (131, 231) of the valve (116, 216) housed in said guide rail (125, 225). The vessel according to claim 4, wherein the guide rail (125, 225) has two side walls (126, 226) extending parallel to each other from the bottom (110, 210) of the container (109). 209) to the interior of the container (109, 209), the tabs (131, 231) of the valve (116, 216) being accommodated in the guide rail (125, 225) between the two side walls (126, 226). ) so as to block the lateral displacement of the valve (116,216). 6. Vessel according to claim 5, wherein the entire upper section of the container (9, 109, 209) opposite the bottom (10, 110, 210) of the container (9, 109, 209) is open. 7. Ship according to one of claims 1 to 6, wherein the valve (16) and the passage (15) in the bottom (10) of the container (9) are circular in shape. 8. Ship according to one of claims 1 to 6, wherein the valve (116) and the passage (115) in the bottom (110) of the container (109) are rectilinear shape. 9. Ship according to one of claims 1 to 6, wherein the valve (216) and the passage (215) in the bottom (210) of the container (209) are shaped circular arc. The ship according to one of claims 8 to 9 in combination with claim 4, wherein the flap tabs (131, 231) are at opposite longitudinal ends of the flapper (116, 216). 11. Ship according to one of claims 1 to 10, wherein the valve (16, 116, 216) comprises a plastic material compatible with Liquefied Natural Gas. Ship according to one of claims 1 to 11, wherein the bottom (10, 110, 210) of the container (9, 109, 209) comprises a plurality of passages (15, 115, 215) connecting the container interior (9, 109, 209) and the outside of the container (9, 109, 209), the container (9, 109, 209) further comprising a plurality of movable flaps (16, 116, 216) arranged to cooperate with a respective valve seat carried by the bottom (10, 110, 210) of the container (9, 109, 209) around each of the passages, each valve (16, 116, 216) being able to obstruct one of passage (15, 115, 215) of the bottom (10, 110, 210) of the container (9, 109, 209) when a pressure differential exerted on said valve (16, 116, 216) between the outside of the container (9, 109 209) and the interior of the container (9, 109, 209) is less than a determined positive threshold and releasing said passage (15, 115, 215) when said pressure differential is greater than said threshold. 13. Ship according to claim 12 in combination with claim 4, wherein at least one guide rail (225) is arranged between two passages of the bottom and has a first portion which receives a first leg of a first valve cooperating with a first valve seat of a first one of said passages and a second portion which receives a second tab of a second valve cooperating with a second valve seat of a second one of said passages so that the guide rail moves the first and second valves (216). 14. A method of loading or unloading a vessel (70) according to one of claims 1 to 13, wherein a cold liquid product is conveyed through insulated pipes (73, 79, 76, 81) from or to a a floating or land storage facility (77) to or from the vessel vessel (71). 15. Transfer system for a cold liquid product, the system comprising a ship (70) according to one of claims 1 to 13, insulated pipes (73, 79, 76, 81) arranged to connect the tank (71). ) installed in the hull of the vessel at a floating or land storage facility (77) and a pump for driving a flow of cold liquid product through the insulated pipelines from or to the floating or land storage facility to or from the vessel of the ship.