CN107850262B

CN107850262B - Sealed heat insulation tank for ship

Info

Publication number: CN107850262B
Application number: CN201680039750.7A
Authority: CN
Inventors: 穆罕默德·萨西
Original assignee: Gaztransport et Technigaz SA
Current assignee: Gaztransport et Technigaz SA
Priority date: 2015-09-29
Filing date: 2016-09-28
Publication date: 2020-03-03
Anticipated expiration: 2036-09-28
Also published as: FR3041603A1; WO2017055744A1; FR3041603B1; CN107850262A; KR20180016562A; KR102041457B1

Abstract

The invention relates to a ship comprising: a canister (3), a pump (7) comprising a pump head (8) arranged near a bottom wall (5) of the canister (3), a container (9), the pump head (8) being accommodated in the container (9), the container (9) comprising a passage (15) connecting an interior of the canister and an interior of the container, a moving valve (16) arranged to close the passage (15) when a pressure difference between an exterior of the container (9) and the interior of the container (9) exerted on the valve (16) is below a determined positive threshold value, and to open the passage when said pressure difference is above said threshold value, wherein the valve (16) has a sloping bottom surface (23) cooperating with a valve seat comprising a complementary sloping surface (24) arranged to shut off communication of the passage (15) between the interior of the canister (3) and the interior of the container (9) when cooperating with the sloping bottom surface.

Description

Sealed heat insulation tank for ship

Technical Field

The present invention relates to the field of sealed and insulated tanks placed in a floating structure, in particular for storing and/or transporting cold products, in particular liquefied gases, such as Liquefied Natural Gas (LNG), which contain a high methane content and are in liquid form at atmospheric pressure at about-162 ℃.

Background

In membrane tank technology, the inner surface of a support structure, such as the inner shell of a double hull vessel, is laid with a multilayer structure comprising two thin sealing membranes alternating with two insulating layers for restricting the heat flow through the tank wall and structurally supporting the sealing membranes. Other techniques use thick steel plates with external insulation.

In order to maximize the efficiency of the operation of such tanks, it is desirable to optimize the amount of useful cargo that can be loaded into and unloaded from the tank. Similarly, to allow LNG to be used to propel a ship when the tanks are nearly empty, it is desirable to be able to pump LNG while minimizing the amount of LNG present in the tanks to propel the ship. However, the use of an unloading pump that draws liquid up from the tank requires a certain liquid head to be maintained at the bottom of the tank, otherwise the suction member of the pump is connected to the gas phase, which empties the pump and/or reduces the performance of the pump. The necessary liquid head may be difficult to reduce due to the tumbling of the cargo caused by the sea gush.

Publication EP1314927 envisages placing the suction member of the pump in a water collection chamber located near the bottom of the tank. The sump chamber is equipped with a check valve to allow liquid contained in the tank to enter the sump chamber and to keep the pumping means in the liquefied gas volume when the LNG in the tank reaches a level below said sump chamber.

Disclosure of Invention

One idea on which the invention is based is to minimize the minimum liquid level in the tank required for the correct operation of the pump in a simple, safe and efficient manner.

According to one embodiment, the invention provides a vessel comprising:

-an insulated tank for containing a cold liquid product,

-a pump comprising a pump head for absorbing a cold liquid product contained in an insulated tank, said pump head being arranged near a bottom wall of the insulated tank,

-a container inside an insulated tank, the pump head being housed in the container, the container comprising a bottom turned towards the bottom wall of the tank and provided with a passage connecting the inside of the container with the outside of the container, a top of the container, opposite to the bottom of said container, the top comprising an opening connected with the inside of the tank, said container further comprising at least one moving valve arranged to cooperate with a valve seat supported by the bottom of said container, said valve being able to close the passage at the bottom of the container when the pressure difference between the outside of the container and the inside of the container exerted on the valve is below a determined positive threshold value and to open the passage when said pressure difference is above said threshold value,

wherein the valve has a sloping bottom surface facing the valve seat, the valve seat comprising a sloping surface facing the valve, the sloping surface of the valve and the sloping surface of the valve seat being complementary and capable of making a tight contact around the passage at the bottom of the container in order to cut off the communication of the passage between the interior of the can and the interior of the container.

Such valves exhibit a significant contact surface with the valve seat when the valve is against the valve seat. This significant contact surface ensures a good seal and thus a good retention of the liquid in the container.

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

According to one embodiment, the container comprises a guiding system for the valve, which guiding system is capable of guiding the valve in a direction parallel or inclined to the direction of gravity, such that the valve closes by gravity.

According to one embodiment, the guiding system comprises a plurality of guiding rods extending from the bottom of the container towards the interior of the container, the valve having a plurality of guiding portions in sliding engagement with respective guiding rods, each guiding rod having one end opposite the bottom of the container comprising a shoulder, each guiding portion of the valve being inserted in a direction in which the respective guiding rod slides between the shoulder of the guiding rod and the bottom of the container to limit displacement of the guiding portions of the valve in the container.

According to one embodiment, the guiding system comprises a plurality of rails, each rail extending from the bottom of the container towards the interior of the container, the valve comprising a plurality of lugs, each lug being received in one of said respective rails and guiding the displacement through said respective rail, each rail further comprising a top wall at an end opposite to the bottom of the container, the top wall being able to limit the displacement of the respective lug of the respective valve received in said rail.

According to one embodiment, the guide comprises two side walls extending parallel to each other from the bottom of the container towards the interior of the container, the lug of the valve being received in the guide between the two side walls to block lateral displacement of the valve.

The container may have a variety of shapes. According to one embodiment, the container is cylindrical.

According to one embodiment, the top of all containers opposite to the bottom of the container is open.

The valves and passages may take a variety of forms. According to one embodiment, the valve and the channel in the bottom of the container are circular. In one embodiment, the valve is in the form of a disk.

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

According to one embodiment, the passage between the valve and the bottom of the container is in the form of a straight line.

According to one embodiment, the valve and the passage at the bottom of the container are rounded.

According to one embodiment, the lug of the valve is opposite at the longitudinal end of the valve.

The valve may be produced from a number of LNG compatible materials. Preferably, such LNG-compatible materials have a lower density than metals in order to minimize the opening pressure of the valve. According to one embodiment, the valve comprises PTFE. More specifically, according to a different variant, the valve is made entirely of PTFE, even comprising a coating of PTFE.

According to one embodiment, the bottom of the container comprises a plurality of passages connecting the interior of the container and the exterior of the container, the container further comprising a plurality of moving valves arranged to cooperate with valve seats supported by the bottom of said container around each passage, each valve being capable of closing one of the passages of the container bottom when the pressure difference between the exterior of the container and the interior of the container exerted on said valve is below a determined positive threshold value and opening said passage when said pressure difference is above said threshold value.

According to one embodiment, at least one guide rail is arranged between two channels of the bottom and has a first part accommodating a first lug of the first valve cooperating with a first valve seat of a first one of said channels and a second part accommodating a second lug of the second valve cooperating with a second valve seat of a second one of said channels, such that said guide rail guides the displacement of the first and second valves.

According to one embodiment, the invention also provides a method for loading or unloading a ship, in which method cold liquid product is led from a floating or onshore storage unit into the tanks of the ship or discharged from the tanks to the floating or onshore storage unit through insulated pipelines.

According to one embodiment, the invention also provides a transfer system for a cold liquid product, the system comprising a vessel as described above, an insulated conduit arranged to connect a tank mounted in the hull to a floating or onshore storage device, and a pump for driving a stream of cold liquid product through the insulated conduit from the floating or onshore storage device into the tank of the vessel or from the tank of the vessel into the floating or onshore storage device.

Aspects of the present invention begin with the idea of minimizing the amount of liquid that must remain in the tank to keep the pump head submerged and avoid pump emptying. Aspects of the present invention begin with the idea of housing the pump head in a container that exhibits good sealing properties. Some aspects of the invention start from the idea of ensuring a well-guided displacement of the valve, in particular in the case of closing the valve by cooperating with a corresponding valve seat. Aspects of the present invention begin with the idea of providing an alternative valve guide. Aspects of the present invention begin with the idea of minimizing the number of guidance systems required to guide the displacement of multiple valves.

Drawings

The invention will be better understood and other objects, details, characteristics and advantages thereof will become more apparent from the following description of several specific embodiments, given by way of illustration and not limitation, with reference to the accompanying drawings.

Figure 1 shows a partial view of a longitudinal section of a methane tanker comprising a tank in which an unloading pump supported by a tripod mast is arranged, and the pump head of which is located near the bottom wall of the tank.

Fig. 2 shows a schematic perspective view of the pump head of fig. 1 housed in a liquid holding container according to a first embodiment of the container and showing the securing of the container to the pump head.

Fig. 3 shows a plan view of the pump head and container of fig. 2, showing the container secured to the pump head, and the bottom of the container including a connecting valve between the interior of the container and the exterior of the container.

Fig. 4 shows a partial cross-sectional view of the bottom of the container showing the valve of fig. 3 in an open position.

Fig. 5 shows a partial cross-sectional view of the bottom of the container showing the valve of fig. 3 in a closed position.

Fig. 6 shows a perspective view of a second embodiment of the container, in which the valve takes the form of flat and linear vanes distributed around the pump head.

FIG. 7 shows a detail view of the valve of FIG. 6 mated with a valve seat and guide system.

Fig. 8 shows a perspective view of a longitudinal section of the valve and guide system of fig. 7.

Figures 9 and 10 show cross-sectional views of the valve and guide system of the second embodiment in the closed and open positions of the valve, respectively.

Fig. 11 shows a plan view of a container according to a third embodiment.

Fig. 12 shows a longitudinal section of the valve of fig. 11 cooperating with a guide system common to two adjacent valves.

Figure 13 is a schematic cross-sectional view of a methane tanker tank and terminal for loading/unloading the tank.

Detailed Description

In the following description, several containers will be described that may be used at pump head height in LNG storage and/or transport tanks. The bottom wall of the tank represents a wall, preferably a full plane, located at the bottom of the tank with respect to the earth's gravitational field. The general geometry of the tank may be of different types. Polyhedral geometries are the most common. Cylindrical, spherical or other geometries are also possible.

The wall of the tank is formed, for example, by a multilayer structure fixed to the supporting wall and comprising two sealing membranes alternated with two thermal insulation barriers. In view of the many known techniques for producing these multilayer structures, the following description will be limited to a brief description of the canister and will describe in more detail the structure of the elements that cooperate with the pump head in the canister. Other techniques use thick steel plates with external insulation.

Referring to fig. 1, a marine vessel 1 comprises a double hull forming a support structure 2, on which support structure 2 the walls of a tank 3 are mounted. Each tank wall 3 comprises a multilayer structure comprising, in turn, a secondary thermal barrier fixed on the supporting structure 2, a secondary sealing film supported by the secondary thermal barrier, a primary thermal barrier covering the secondary sealing film and a primary sealing film supported by the primary thermal barrier.

A tripod 4 is fixed to the side wall 5 of the tank 3. The triangular mast 4 is preferably substantially centered at the mid-width of the vessel. The triangular mast 4 extends from a bottom wall 5 of the tank to a top wall 6 of the tank 3. The triangular mast 4 supports one or more pumps 7, the pump heads 8 of which are adjacent the bottom wall 5 of the tank 3. The lines connect the pump head 8 to a cargo handling system (not shown) through the top wall 6 of the tank 3. The cargo handling system makes it possible to load/unload LNG contained in the tank 3 by means of the pump 7.

When unloading LNG from the tank or in the case of supplying gas to the engine of the vessel using LNG contained in the tank, the pump 7 is activated to pump the LNG contained in the tank 3 via the pump head 8. However, for a vessel whose engine is supplied with LNG from a tank and is returning, only the liquid tail end of the LNG remains in the tank for supply to the engine of the vessel in the return trip. Now, the LNG level in the tank 3 at the level of the pump head 8 may vary due to the rolling motion that may be caused at the sea on which the vessel 1 is sailing during this return journey. Thus, when the tank 3 is almost empty, the movement of the vessel 1 due to tilting and rocking does not ensure that the pump head 8 is continuously immersed in LNG. In order to keep the pump head 8 submerged in LNG regardless of the movement of LNG in the tank 3, the pump head 8 is housed in a container 9 as shown in fig. 2 to 11. Such a container 9 is fixed and rests at the pump head 8 above the bottom wall 5 into the tank 3.

Fig. 2 shows 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 shows said container 9 and the fixing of said container 9 to the pump head 8.

The container 9 shown in fig. 2 has a cylindrical shape. The container 9 comprises a circular bottom 10 (see fig. 3) which extends above the tank 3 parallel to the bottom wall 5 of the tank 3. Preferably, the distance between the bottom of the container and the bottom wall of the tank is between 25 and 150mm, a maximum of up to 250mm being possible. The circular side wall 11 extends from the bottom 10 of the container 9 towards the top wall 6 of the tank 3, that is to say at right angles to the bottom wall 5 of the tank 3, that is to say in a direction parallel to the direction of gravity of the earth.

The top of the container 9 is free of any covering walls so that the top end of the container 9 opposite the bottom 10 of the container is open. Thus, when the LNG level in tank 3 exceeds that of vessel 9, vessel 9 is filled with LNG.

The inner surface 12 of the wall 11 comprises two lugs 13 which project radially towards the inside of the container 9. These lugs 13 extend diametrically opposite from the region of the inner surface 12. The pump head 8 comprises two shoulders 14 which project radially outwardly, that is to say towards the inner surface 12 of the container. The lug 13 of the container 9 is secured to the shoulder 14 of the pump head 8 by any suitable means, for example by using screws and nuts, welding or the like. Thus, the container 9 is fixed to the pump head 8, whereas said pump head 8 is housed inside said container 9. Preferably, pump head 8 is located in the middle of container 9.

Fig. 3 shows a plan view of the pump head 8 and container 9, showing the container 9 secured to the pump head 8, and the bottom 10 of the container 9 including a connecting valve 16 between the interior and exterior of the container 9.

In the first embodiment shown in fig. 2 to 5, the container 9 comprises three channels 15 through the bottom 10 of the container 9 (see fig. 4 and 5). These passages 15 are evenly distributed around the pump head 8. Furthermore, the container 9 comprises three valves 16 for opening or closing the passage 15 depending on the pressure exerted by the LNG contained in the tank 3, as described below. Each valve 16 has a diameter greater than the diameter of the passage 15 with which it is fitted. Furthermore, each valve 16 is coaxial with the passage 15 with which it cooperates. The valve 16 has a circular form.

Each channel 15 is surrounded by an attachment piece 17 mounted on the container bottom 10. These additional pieces 17 have a through central hole extending to the corresponding passage 15 of the container 9. Furthermore, these appendages 17 each form a valve seat cooperating with a respective valve 16, as described below with respect to fig. 4 and 5. These additional pieces 17 are fixed to the bottom 10 of the container 9 by any suitable means, for example using screws or nuts, or even by welding.

Fig. 4 and 5 illustrate the operation of the valve 16 shown in fig. 3.

When unloading tank 3, one end 18 of pump head 8, through which LNG is drawn, is preferably located near bottom 10 of vessel 9 so as to remain submerged in the LNG in vessel 9.

The valve 16 moves in the container on a displacement axis 19 at right angles to the bottom 10 of the container 9 and preferably to the gravitational force parallel to the earth. To this end, the guide system is able to guide and limit the displacement of the valve 16. In the embodiment shown in fig. 2 to 5, the guide system comprises four pins 20 (only three of which are shown in fig. 4 and 5) fixed on the bottom 10 of the container 9. Each pin 20 extends from the bottom 10 of the container 9 towards the inside of the container 9 parallel to the axis of movement 19 of the valve 16. These pins 20 are fixed to the bottom 10 of the container 9 by any suitable means, for example by welding. Each pin 20 passes through an attachment piece 17, which for this purpose comprises four specially provided bores. The end 21 of each pin 20 opposite the bottom 10 of the container 9 has a reduced-size portion of the thread 21.

The peripheral edge of the valve 16 has four apertures 22. Each hole 22 is penetrated by a corresponding pin 20. Thus, the valve displacement is guided by sliding along the pin 20 from its peripheral edge. A nut 32 is screwed onto the end 21 of each pin 20. The nut 32 forms a shoulder which prevents displacement of the valve 16 along the axis 19 between said end 21 and the appendix 17.

The valve 16 is movable under its own weight and, if appropriate, under the pressure difference exerted on the valve 16 between the interior of the container 9 and the exterior of the container 9. Thus, when the container 9 is surrounded by LNG present in the tank 3, without the LNG exceeding the top end of the container 9 and thus being pulled into the container 9 through said open top end of the container 9, the valve 16 is subjected, on the one hand, to the internal pressure caused by the LNG present in the container 9 and, on the other hand, to the external pressure caused by the LNG present in the tank 3 surrounding the container 9 in contact with the valve 16. The valve 16 is thus subjected to a pressure difference which can push the valve 16 back from the attachment piece 17 and thus from the valve seat. This pressure differential allows the valve to open when the following equation is satisfied:

P_tankx S_bottom+F_buoyancy>P_bowlx S_top+Weight_valve

wherein, P_tankIndicating the pressure, S, exerted on the valve 16 by the LNG contained in the tank 3 outside the container 9_bottomDenotes the surface area of the valve 16 in contact with the LNG contained in the tank 3 outside the container 9, F_buoyancyShowing that the container 9 is accommodated externally in a tank3 buoyancy, P, exerted on the valve 16 by the LNG_bowlIndicating the pressure, S, exerted on the valve 16 by the LNG contained in the container 9_topShowing the upper surface area of the valve 16, wherein the LNG contained in the container 9 exerts pressure on the upper surface of the valve 16, and weight_valveIndicating the weight of the valve 16. In general, this equation reflects the opening of the valve 16, that is to say its separation from the appendix 17 forming the valve seat, depending on the difference in height between the LNG contained in the container 3 and the LNG contained in the container 9, outside the container 9.

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

The valve 16 is made of a material having a density lower than stainless steel metal to limit the cracking pressure and to be compatible with LNG. By way of example, preference is given to a plastic material, preferably of the polytetrafluoroethylene type, also known as PTFE, for example in the form of a coating of PTFE or a solid material. Thus, the valve 16 is light under the pressure exerted by the LNG contained in the container 3 outside the container 9, and its opening is hardly disturbed by the weight of the valve. Moreover, the PTFE coating gives the valve 16 good sliding properties, facilitating its displacement in the container 9.

As shown in fig. 4 and 5, the bottom surface of the valve 16 includes a ramp portion 23. Thus, the valve 16 has a tapered portion, the smallest diameter of which is located near the bottom 10 of the container 9.

Furthermore, the attachment 17 forming the valve seat also comprises a ramp portion 24. The ramp portion 24 of the appendix 17 complements the ramp portion 23 of the valve 16, said ramp portion 24 of the appendix 17 having a minimum diameter close to the bottom 10 of the container 9. Typically, the ramp portion 24 of the attachment forms a valve seat with which the valve 16 cooperates to close the passage 15. Thus, in the case where the ramp portion 23 of the valve 16 forms an angle of 45 with the bottom 10 of the container 9, the ramp portion 24 of the attachment 17 also forms an angle of 45 with the bottom of the container.

These

ramp portions

23 and 24 provide a significant contact surface between the valve seat and the valve 16, ensuring a better tightness of the container 9 when the valve 16 blocks the passage 15. Furthermore, when the valve 16 is moved towards the bottom 10 of the container, the inclined surface 24 of the valve seat guides the displacement of the valve 16 to close the passage 15.

The pressure exerted on the valve 16 by the LNG contained in the vessel 3 can withdraw the valve 16 from the valve seat when the LNG contained in the vessel 3 moves around the vessel or towards the vessel due to the tilting and swinging of the vessel 1. Thus, the passage 15 is no longer blocked and the LNG present in the tank 3 enters the vessel 9 through the passage 15 located in the bottom 10 of the vessel. In contrast, when the LNG contained in the container 3 does not surround the container and does not exert sufficient pressure on the valve 16 to push it back out of the valve seat, the LNG contained in the container 9 remains inside said container through the closing channel 15, wherein the closing channel 15 is completed by the valve 16 cooperating in a sealed manner with the additional piece forming the valve seat.

Fig. 6 to 10 show a second embodiment of the valve 16 as shown in fig. 3 to 5. In this second embodiment, elements that are the same as or perform the same function as in the first embodiment have the same reference numeral increased by 100.

In a second embodiment, the valve 116 is manufactured in the form of a linear blade. In the variant shown in fig. 6, the bottom 110 of the container 109 comprises four rectilinear channels 115 cooperating with four valves 116, the channels 115 being evenly distributed around the pump head 108. Each channel 115 is surrounded by an appendage 117 forming a valve seat.

As shown in fig. 9 and 10, the bottom surface of the valve 116 has a slope 123 in the longitudinal direction of the valve 16. Thus, the valve 116 has a trapezoidal cross section. Similarly, each appendage 117 forming a valve seat has a ramp 124 complementary to the ramp 123 of the valve 116. Thus, with the first embodiment, by cooperating with the

inclined surfaces

123 and 124, the valve 116 is guided at the end of the closing displacement. Furthermore, as in the first embodiment, the contact surface between the valve 116 and the valve seat formed by the appendage 117 is important in order to avoid LNG from the container 109 leaking when the LNG in the tank 103 outside the container 109 is not in contact with the bottom surface of the valve 116.

In this second embodiment, the system for guiding the displacement of the valve 116 is created by a guide rail 125 located on the bottom 110 of the container 109. For each channel 115, a guide rail 125 is mounted on the bottom 110 of the container at opposite longitudinal ends of the channel 115. Each rail 125 has a "U" shaped cross-section. The guide 125 comprises two side walls 126 extending from the bottom 110 of the container 109 towards the inside of the container 109 and at right angles to said bottom wall 110 on both sides of the appendix 117. These side walls 126 form branches of a "U" shaped cross-section. The bottom of the "U" shaped cross-section is formed by a top wall 127, the top wall 127 connecting the ends of the opposite side walls 126 to the bottom 110 of the container 109. The top wall 127 is parallel to the bottom 110 of the container 109.

The guide rail 125 is fixed to the bottom 110 of the container 109 by means of bolts 128 fixed to the bottom 110 of the container 109. Bolts 128 extend from the bottom 110 of the container 109 and through the top wall 127 of the rail 125. The top end of the bolt 128 opposite the bottom 110 of the container 109 comprises a nut 129 for fixing the rail 125. In addition, an "L" shaped block 130 is interposed between the top wall 127 and the appendix 117 forming the valve seat. The block 130 prevents deformation of the rail 125 when the nut 129 is threaded onto the stud 128. Both the block 130 and the appendage 117 have holes to allow the passage of the bolt 128 from the bottom 110 of the container 109, as shown in fig. 7.

The longitudinal ends of the valve 116 form lugs 131 which are received in the guide rails 125. The lug 131 is blocked in the transverse direction by the side wall 126 of the guide rail 125. Similarly, the lug 131 is movable in a direction parallel to the axis of displacement 119 of the valve 116, the axis 119 being located between, on the one hand, the appendage 117 forming the valve seat and, on the other hand, the top wall 127 of the guide 125. Finally, as shown in fig. 8, the lug 131 is blocked from displacement in the longitudinal direction of the valve 116 by abutting on the block 130 of the guide rail 125. Each valve 116 is therefore guided to be displaced in a direction 119 at right angles to the bottom 110 of the container 109, which is done by the cooperation between the lugs 131 received in the respective guides 125 and said guides 125.

In the embodiment shown in fig. 6 to 10, the lug 131 has the same cross-section as the rest of the valve 116. Thus, the valve 116 is easy to manufacture and does not require any special production of the lugs 131. However, the lug 131 may have any other form suitable for cooperating with a rail. Fig. 9 and 10 show the obstruction of displacement on the axis 119 of displacement of the valve 116 of the lug 131 by the top wall 127 of the guide 125. These figures 9 and 10 also show the cooperation between the

ramps

123 and 124 to ensure a good seal of the container 9 when the valve 116 cooperates with the appendix 117 and to ensure an effective guiding displacement when the valve 116 is displaced towards the seat formed by the appendix 117.

In a variant not shown, the passage through the bottom of the container and the valve is circular, as in the first embodiment. However, in this variation, each valve includes a plurality of lugs that project radially outward from its peripheral edge. A plurality of rails, similar to the rails of the second embodiment, are secured to the bottom of the container. Each lug of the valve cooperates with a respective guide track to guide the valve in displacement. In another variant, each valve further comprises a lug projecting from its peripheral edge and guided in displacement by the cooperation of a hole produced in said lug with the pin, as in the first embodiment.

Fig. 11 and 12 show a third embodiment of a valve corresponding to the variant of the valve 116 shown in fig. 6 to 10. In this third embodiment, elements that are the same as or perform the same function as in the first embodiment have the same reference numeral increased by 200.

The third embodiment differs from the second embodiment in that the valve 216 takes the form of a vane in the form of a circular arc. As shown in fig. 11, the bottom 210 of the container 209 includes four valves 216, each forming an arc of about 90 °. As in the second embodiment, the valves 216 are evenly distributed around the pump head 208 and cooperate with an appendage 217, also in the form of a circular arc, surrounding a channel 215 of the bottom 210 of the container 209.

Furthermore, in this embodiment, the same guide track 225 is capable of guiding the displacement of two adjacent valves 216. Typically, one and the same guide track 225 with a "U" shaped cross section prevents the lateral and vertical displacement of two adjacent valves 216 in a similar manner to the valve 116 of the second embodiment, but one and the same "L" shaped block 230 makes it possible to block circumferentially two adjacent valves 216, said block 230 being inserted circumferentially between the lugs 231 of said two adjacent valves.

In a variant not shown, the block 230 has a convex shape, such as a square or a semi-circle, turned towards the valve 216, and the valve 216 has a complementary concave shape. This form of block 230 may also laterally guide the vertical displacement of the valve 216 and thus have the guide track 225 only serving as a vertical abutment.

Referring to fig. 13, a cross-sectional view of a methane tanker 70 shows a generally prismatic sealed insulated tank 71 mounted in a double hull 72 of a vessel. The walls of the tank 71 comprise a primary sealing barrier for contact with the LNG contained in the tank, a secondary sealing barrier provided between the primary sealing barrier and the double hull 72 of the vessel, and two thermal insulation barriers arranged between the primary sealing barrier and the secondary sealing barrier and between the secondary sealing barrier and the double hull 72, respectively.

As is known per se, a loading/unloading line 73 arranged on the top deck of the vessel may be connected to the offshore or harbour terminal by means of suitable connectors for bringing LNG cargo to and from between the tanks 71.

Figure 13 shows an example of an offshore terminal comprising a loading and unloading station 75, a subsea pipeline 76 and an onshore installation 77. The loading and unloading station 75 is a fixed offshore facility that includes a moving arm 74 and a riser 78, the riser 78 supporting the moving arm 74. The moving arm 74 supports a bundle of insulated flexible tubes 79, which can be connected to the loading/unloading line 73. The orientable mobile arm 74 is adaptable to all methane tanker templates. A connection pipe, not shown, extends inside the riser 78. The loading and unloading station 75 allows the methane tanker 70 to be loaded or unloaded from an onshore installation 77 onto the onshore installation 77. The onshore installation 77 comprises a liquefied gas storage tank 80 and a connection pipe 81, the connection pipe 81 being connected by a subsea pipeline 76 to the loading or unloading station 75. The subsea pipeline 76 allows the liquefied gas to be transported over a significant distance, e.g., 5 kilometers, between the loading or unloading station 75 and the onshore facility 77, which makes it possible to maintain the methane tanker 70 at a significant distance from shore during loading and unloading operations.

In order to generate the pressure necessary for the transport of the liquefied gas, pumps are provided which are buried in the vessel 70 and/or which are used by the onshore installation 77 and/or which are used by the loading and unloading station 75.

Although the invention has been described in connection with several specific embodiments, it is obvious that the invention is in no way limited thereto and comprises all technical equivalents of the means described and their combinations, provided that they fall within the scope of the invention.

Use of the verb "comprise" or "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The use of the indefinite article "a" or "an" for an element or step does not exclude the presence of a plurality of such elements or steps, unless otherwise specified.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Claims

1. A marine vessel, comprising:

-an insulated tank (3) for containing a cold liquid product,

-a pump (7) comprising a pump head (8,108) for absorbing a cold liquid product contained in the insulated tank (3), the pump head (8,108) being arranged near a bottom wall (5) of the insulated tank (3),

-a container (9,109,209) located inside the thermally insulated tank (3), the pump head (8,108) being housed in the container (9,109,209), the container (9,109,209) comprising a bottom (10,110,210) facing the bottom wall of the tank and provided with a passage (15,115,215) connecting the interior of the container with the exterior of the container, a top of the container (9,109,209) opposite the bottom (10,110,210) of the container (9,109,209), the top comprising an opening connected with the interior of the tank (3), the container (9,109,209) further comprising a moving valve (16,116,216) arranged to cooperate with a valve seat (17,117,217) supported by the bottom (10,110,210) of the container (9,109,209), the valve (16,116,216) being able to close the passage (15,115,215) of the container (110, 9,109,209) when the pressure difference between the exterior of the container (9,109,209) and the interior of the container (9,109,209) applied on the valve (16,116,216) is below a determined positive threshold, and said valve is capable of opening said passage (15,115,215) when said pressure difference is higher than said threshold value,

wherein the valve (16,116,216) has a sloping bottom surface (23,123,223) facing the valve seat, the valve seat (17,117,217) comprising a sloping surface (24,124,224), a sloping bottom surface (23,123,223) facing the valve (16,116,216), the sloping bottom surface (23,123,223) of the valve (16,116,216) and the sloping surface (24,124,224) of the valve seat (17,117,217) being complementary and capable of making a tight contact around the passage (15,115,215) of the bottom (10,110,210) of the container (9,109,209) in order to cut off the communication of the passage (15,115,215) between the interior of the can (3) and the interior of the container (9,109,209),

and wherein the container (9,109,209) comprises a guide system (25,125,225) for the valve (16,116,216) which is able to guide the valve (16,116,216) in a direction parallel or inclined to the direction of gravity, so that it is closed by gravity, the guide system (25) comprising a plurality of guide rods (20) extending from the bottom (10) of the container (9) towards the inside of the container (9), the valve (16) having a plurality of guides in sliding engagement with the respective guide rods (20), one end (21) of each guide rod (20) being opposite the bottom (10) of the container (9), wherein the guide rods (20) comprise shoulders (22), each guide of the valves (16) being inserted along the direction in which the respective guide rod (20) slides between the shoulders (22) of the guide rods (20) and the bottom (10) of the container (9), to limit the displacement of the valve (16) in the container (9).

2. A marine vessel, comprising:

-an insulated tank (3) for containing a cold liquid product,

-a container (9,109,209) located inside the thermally insulated tank (3), a pump head (8,108) being housed in the container (9,109,209), the container (9,109,209) comprising a bottom (10,110,210) facing the bottom wall of the tank and being provided with a passage (15,115,215) connecting the interior of the container with the exterior of the container, a top of the container (9,109,209) being opposite to the bottom (10,110,210) of the container (9,109,209), the top comprising an opening connected with the interior of the tank (3), the container (9,109,209) further comprising a moving valve (16,116,216) arranged to cooperate with a valve seat (17,117,217) supported by the bottom (10,110,210) of the container (9,109,209), the valve (16,116,216) being capable of closing the passage (15,115,215) of the container (10, 115, 210) when the pressure difference between the exterior of the container (9,109,209) and the interior of the container (9,109,209) applied on the valve (16,116,216) is below a determined positive threshold value, and said valve is capable of opening said passage (15,115,215) when said pressure difference is higher than said threshold value,

wherein the valve (16,116,216) has a sloping bottom surface (23,123,223) facing the valve seat, the valve seat (17,117,217) comprising a sloping surface (24,124,224), a sloping bottom surface (23,123,223) facing the valve (16,116,216), the sloping bottom surface (23,123,223) of the valve (16,116,216) and the sloping surface (24,124,224) of the valve seat (17,117,217) being complementary and capable of making a tight contact around the passage (15,115,215) of the bottom (10,110,210) of the container (9,109,209) in order to cut off the communication of the passage (15,115,215) between the interior of the tank (3) and the interior of the container (9,109,209),

and wherein the container (9,109,209) comprises a guiding system (25,125,225) for the valve (16,116,216) capable of guiding the valve (16,116,216) in a direction parallel or inclined to the direction of gravity, such that the valve is closed by gravity, the guiding system comprising a plurality of rails (125,225), each rail (125,225) extending from a bottom (110,210) of the container (109,209) towards the interior of the container (109,209), the valve (116,216) having a plurality of lugs (131,231), each lug (131,231) being received in one of the respective rails (125,225) and being guided in displacement by the respective rail (125,225), each rail (125,225) further comprising a top wall (127,227) at an end opposite to the bottom (110,210) of the container (109,209), the top wall being capable of limiting the displacement of the respective lug (131,231) of the valve (116,216) received in the rail (125, 225).

3. The vessel according to claim 2, wherein the guide rail (125,225) comprises two side walls (126,226) extending parallel to each other from the bottom (110,210) of the container (109,209) towards the interior of the container (109,209), the lug (131,231) of the valve (116,216) being received in the guide rail (125,225) between the two side walls (126,226) to block lateral displacement of the valve (116, 216).

4. A ship as claimed in any one of claims 1 to 3, characterized in that the top of the container (9,109,209) opposite the bottom (10,110,210) of the container (9,109,209) is open.

5. A ship as claimed in any one of claims 1 to 3, characterized in that the valve (16) and the passage (15) of the bottom (10) of the container (9) are circular.

6. A ship as claimed in any one of claims 1 to 3, characterized in that the valve (116) and the passage (115) of the bottom (110) of the container (109) are in the form of a straight line.

7. A ship as claimed in any one of claims 1 to 3, characterized in that the valve (216) and the passage (215) of the bottom (210) of the container (209) are circular-arc-shaped.

8. A ship as claimed in claim 2, characterized in that the valve (116) and the channel (115) of the bottom (110) of the container (109) are in the form of a straight line, and the lugs (131,231) of the valve are opposite at the longitudinal ends of the valve (116, 216).

9. A ship as claimed in claim 2, characterized in that the valve (216) and the channel (215) of the bottom (210) of the container (209) are circular-arc-shaped and the lugs (131,231) of the valve are opposite at the longitudinal ends of the valve (116, 216).

10. A vessel according to any one of claims 1 to 3, wherein the valve (16,116,216) comprises a plastics material compatible with the liquefied natural gas phase.

11. A ship as claimed in any one of claims 1 to 3, characterized in that the bottom (10,110,210) of the container (9,109,209) comprises a plurality of passages (15,115,215) connecting the interior of the container (9,109,209) and the exterior of the container (9,109,209), the container (9,109,209) further comprising a plurality of moving valves (16,116,216) arranged to cooperate with respective valve seats supported by the bottom (10,110,210) of the container (9,109,209) around each passage, each valve (16,116,216) being capable of closing one of the passages (15,115,215) of the bottom (10,110,210) of the container (9,109,209) when the pressure difference between the exterior of the container (9,109,209) and the interior of the container (16,116,216) exerted on the valve (16,116,216) is below a determined positive threshold value, and of opening the passage (15,115,215) when the pressure difference is above the threshold value.

12. The vessel according to claim 2, wherein the bottom (10,110,210) of the container (9,109,209) comprises a plurality of passages (15,115,215) connecting the interior of the container (9,109,209) and the exterior of the container (9,109,209), the container (9,109,209) further comprises a plurality of moving valves (16,116,216) arranged to cooperate with respective valve seats supported by the bottom (10,110,210) of the container (9,109,209) around each passage, each valve (16,116,216) being capable of closing one of the passages (15,115,215) of the bottom (10,110,210) of a container (9,109,209) when the pressure difference between the exterior of the container (9,109,209) and the interior of the container (9,109,209) exerted on the valve (16,116,216) is below a determined positive threshold value, and each valve being capable of opening the passage (15,115,215) when the pressure difference is above the threshold value, at least one rail (225), arranged between two passages of the bottom, and has a first portion that receives a first lug of a first valve that engages a first valve seat of a first one of the passages and a second portion that receives a second lug of a second valve that engages a second valve seat of a second one of the passages such that the guide guides displacement of the first and second valves (216).

13. A method for loading or unloading a vessel (70) according to any one of claims 1 to 12, characterised in that the cold liquid product is led from a floating or onshore storage unit (77) to the tanks of the vessel (70) or discharged from the tanks (71) to the floating or onshore storage unit (77) through insulated pipes (73,79,76, 81).

14. A transport system for a cold liquid product, the system comprising a vessel (70) according to any of claims 1 to 12, insulated conduits (73,79,76,81) arranged to connect tanks (71) mounted in the hull to a floating or onshore storage facility (77), and a pump for driving a stream of cold liquid product through the insulated conduits from the floating or onshore storage facility into the vessels 'tanks or from the vessels' tanks into the floating or onshore storage facility.