SYSTEM FOR STORING AND TRANSPORTING A CRYOGENIC FLUID ON A SHIP

Abstract

An installation for storing and transporting a cryogenic fluid on a ship includes: a sealed and thermally insulating tank, having a ceiling wall including, from the outside to the inside, a primary thermally insulating barrier and a primary sealing membrane intended to be in contact with the cryogenic fluid; and a sealed line penetrating through the ceiling wall of the tank, the line including a bottom portion of which a first end is situated inside the ceiling wall of the tank and a second end is situated outside the ceiling wall of the tank in a thicknesswise direction of the ceiling wall, and a top portion fixed to the second end of the bottom portion. The bottom portion includes an alloy with low thermal expansion coefficient. The primary sealing membrane is tightly fixed to the bottom portion of the line around the line.

Claims

1. An installation for storing and transporting a cryogenic fluid on a ship (1), the installation comprising: a sealed and thermally insulating tank (2) intended for the storage of the cryogenic fluid in a state of diphasic liquid-vapor equilibrium, the tank (2) having a ceiling wall comprising, in the direction of a thickness of the wall from the outside to the inside of the tank (2), a primary thermally insulating barrier (11) and a primary sealing membrane (10) intended to be in contact with the cryogenic fluid; a sealed line (14) penetrating through the ceiling wall of the tank (2) so as to define a passage for discharging the vapor phase of the cryogenic fluid from the inside to the outside of the tank (2), the line (14) comprising a bottom portion (15) of which a first end is situated inside the ceiling wall of the tank (2) and a second end is situated outside the ceiling wall of the tank (2) in a thicknesswise direction of the ceiling wall, and a top portion (16) fixed to the second end of the bottom portion (15); wherein the bottom portion (15), in contact with said cryogenic fluid, is composed of an alloy with low thermal expansion coefficient while the upper portion (16) comprises a stainless steel, the alloy with low thermal expansion coefficient having a lower thermal expansion coefficient than said stainless steel, and wherein the primary sealing membrane (10) is tightly fixed to the bottom portion (15) of the line (14) around the line (14).

2. The installation as claimed in claim 1, wherein the bottom portion (15) of the line (14) and the primary sealing membrane (10) are composed of an iron-nickel alloy whose thermal expansion coefficient is between 1.2 and 2.010.sup.6 K.sup.1.

3. The installation as claimed in claim 1, wherein the bottom portion (15) is tightly welded to the primary sealing membrane (10) via a flange ring (17).

4. The installation as claimed in claim 3, wherein the ceiling wall of the tank (2) also comprises, in the thicknesswise direction of the wall outside the primary thermally insulating barrier (11), a secondary thermally insulating barrier (13) and a secondary sealing membrane (12).

5. The installation as claimed in claim 4, wherein the primary thermally insulating barrier (11) and the secondary thermally insulating barrier (13) are each composed of a plurality of insulating caissons (18), the line (14) passing right through one of the caissons (18) of the plurality of caissons (18) of each of the primary and secondary thermally insulating barriers.

6. The installation as claimed in claim 4, wherein the primary sealing membrane (10) and/or the secondary sealing membrane (12) comprise a plurality of elongate strakes (20) with raised edges welded edge-to-edge in the longitudinal direction of the strake, each strake (20) comprising a flat zone between two longitudinal raised edges, the line (14) passing through the primary sealing member and/or the secondary sealing membrane (12) through the flat zone of an elongate strake (20).

7. The installation as claimed in claim 6, wherein the strake (20) of the primary (10) and/or secondary (12) sealing membrane comprises a reinforced portion (32), the reinforced portion (32) having a greater thickness than the rest of the strake (20) and comprising a flat zone between two longitudinal raised edges, the line (14) passing through the flat zone of the reinforced portion (32).

8. The installation as claimed in claim 4, wherein the installation comprises a sheath (21) surrounding the line (14) with a gap in a radial direction and fixed to the top portion (16) of the line (14), the sheath (21) extending from the top portion (16) at least to the secondary sealing membrane (12), and the secondary sealing membrane (12) being tightly fixed to the sheath (21) all around the sheath (21).

9. The installation as claimed in claim 8, wherein the sheath (21) is welded to the secondary sealing membrane (12) via a flange ring (17).

10. The installation as claimed in claim 6, wherein the flange ring or rings (17) have a thickness greater than the strakes (20).

11. A ship (1) comprising an installation (1) as claimed in claim 1, the ceiling wall being attached to a bottom surface of an intermediate deck (8) of the ship (1).

12. The ship (1) as claimed in claim 11, wherein the line (14) comprises a bellows compensator (25) on an end of the top portion (16) remote from the bottom portion (15), the compensator (25) being configured to ensure the fixing of the line (14) to a top surface of a top deck (9) of the ship (1), the compensator (25) having corrugations configured to allow the thermal contraction of the line (14).

13. The ship (1) as claimed in claim 11, wherein the line (14) comprises an insulating sleeve (26) surrounding a part of the top portion (16) of the line (14) and situated between the intermediate deck (8) of the ship (1) and a top deck (9) of a ship (1).

14. The ship (1) as claimed in claim 13, wherein the intermediate deck (8) and the top deck (9) comprise an orifice (27, 28), the orifice (27, 28) having a diameter greater than an outer diameter of the top portion (16) of the line (14), the line (14) passing through the intermediate deck (8) and the top deck (9) through the intermediate deck orifice (27) and the top deck orifice (28) respectively.

15. The ship (1) as claimed in claim 14, wherein the intermediate deck (8) comprises a coaming (22) on a top surface of the intermediate deck (8), the coaming (22) surrounding the intermediate deck orifice (27) and being passed through by the line (14), and wherein the line (14) is fixed to the coaming (22).

16. A method for loading or offloading a ship (1) as claimed in claim 11, wherein a cryogenic fluid is conveyed through insulated pipelines (40, 43, 46, 48) from or to a floating or onshore storage installation (44) to or from a tank (2) of the ship (1).

17. A transfer system for a cryogenic fluid, the system comprising a ship (1) as claimed in claim 11, insulated pipelines (40, 43, 46, 48) arranged so as to link the tank (2) installed in the double hull (7) of the ship (1) to a floating or onshore storage installation (44) and a pump for driving a flow of cryogenic fluid through the insulated pipelines from or to the floating or onshore storage installation to or from the tank (2) of the ship (1).

18. The installation as claimed in claim 2, wherein the bottom portion (15) is tightly welded to the primary sealing membrane (10) via a flange ring (17).

19. The installation as claimed in claim 1, wherein the ceiling wall of the tank (2) also comprises, in the thicknesswise direction of the wall outside the primary thermally insulating barrier (11), a secondary thermally insulating barrier (13) and a secondary sealing membrane (12).

20. The installation as claimed in claim 2, wherein the ceiling wall of the tank (2) also comprises, in the thicknesswise direction of the wall outside the primary thermally insulating barrier (11), a secondary thermally insulating barrier (13) and a secondary sealing membrane (12).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0065] The invention will be better understood, and other aims, details, features and advantages thereof will emerge more clearly from the following description of several particular embodiments of the invention, given purely in an illustrative and nonlimiting manner, with reference to the attached drawings.

[0066] FIG. 1 is a cutaway schematic representation of a ship comprising a cryogenic fluid storage tank.

[0067] FIG. 2 is a partial schematic representation of an installation for storing and transporting a cryogenic fluid on a ship.

[0068] FIG. 3 is an enlarged view of the detail III, of the storage installation of FIG. 2.

[0069] FIG. 4 is an enlarged view of the detail IV, of the storage installation of FIG. 2.

[0070] FIG. 5 is an exploded view of a tank wall, notably of the secondary thermally insulating barrier and of the secondary sealing membrane.

[0071] FIG. 6 is an exploded view of a tank wall, notably of the primary thermally insulating barrier and of the primary sealing membrane.

[0072] FIG. 7 is a schematic cross-sectional view of an inclined cryogenic fluid storage tank.

[0073] FIG. 8 is a cutaway schematic representation of a ship comprising a cryogenic fluid storage tank and of a terminal for loading/offloading this tank.

DETAILED DESCRIPTION OF EMBODIMENTS

[0074] By convention, the terms top, bottom, above and below are used to define a relative position of an element or of a part of an element with respect to another in a direction directed from the tank 2 to the top deck 9 of the ship 1.

[0075] FIG. 1 shows a ship 1 equipped with an installation for storing and transporting cryogenic fluid, notably liquefied natural gas, which comprises a plurality of sealed and thermally insulating tanks 2. Each tank 2 is associated with an exhaust riser 4 provided on a top deck 9 of the ship 1 and allows gas in vapor phase to escape from the occurrence of an overpressure inside the associated tank 2.

[0076] At the aft end of the ship 1 there is a machine compartment 3 which conventionally comprises a hybrid supply steam turbine capable of operating either by diesel fuel combustion, or by combustion of oil-off gas coming from the tanks 2.

[0077] The tanks 2 have a longitudinal dimension extending along the longitudinal direction of the ship 1. Each tank 2 is bordered at each of its longitudinal ends by a pair of transverse partitions 5 delimiting a sealed separating space, known as cofferdam 6.

[0078] The tanks are thus separated from one another by a transverse cofferdam 6. It can thus be seen that the tanks 2 are each formed inside a supporting structure which consists, on the one hand, of the double hull 7 of the ship 11, and on the other hand, of one of the transverse partitions 5 of each of the cofferdams 6 bordering the tank 2.

[0079] FIG. 2 schematically represents a line 14 making it possible to define an exhaust passage for the vapor phase of the cryogenic fluid from the inside to the outside of the tank 2, the line 14 passing in succession through the tank 2, the intermediate deck 8 of the ship 1 and the top deck 9 of the ship 1.

[0080] The sealed and thermally insulating tank 2 has a ceiling wall attached to the intermediate deck 8, the wall comprising, in the thicknesswise direction of the wall from the outside to the inside of the tank 2: a secondary thermally insulating barrier 13, a secondary sealing membrane 12, a primary thermally insulating barrier 11 and a primary sealing membrane 10.

[0081] The line 14 is formed by a bottom portion 15 and a top portion 16. The bottom portion 15 is formed from an alloy of iron and of nickel with an expansion coefficient typically lying between 1.2.10.sup.6 and 2.10.sup.6 K.sup.1, or from an iron alloy with high manganese content with an expansion coefficient typically of the order of 7.10.sup.6 K.sup.1, i.e. a low thermal expansion coefficient. The bottom portion 15 has a first end situated inside the tank 2 and a second end situated outside the tank 2.

[0082] The top portion 16 is formed from stainless steel and welded by a first end to the second end of the bottom portion 15 so as to create a continuity of the line 14. The second end of the top portion 16 is linked to a pipeline of the ship 1. The top portion 16 has a greater wall thickness than the bottom portion 15.

[0083] The bottom portion 15 of the line 14 passes first of all through the primary sealing membrane 10 and the primary thermally insulating barrier 11. The primary sealing membrane 10 is tightly welded all around the bottom portion 15 to guarantee the continuity of the seal-tightness of the primary sealing membrane 10.

[0084] A sheath 21 surrounds the line 14 with a gap in a radial direction and fixed to the top portion 16 of the line 14. The sheath extends from the top portion 16 at least to the secondary sealing membrane 12. The secondary sealing membrane 12 is tightly welded all around the sheath 21 to guarantee the continuity of the seal-tightness of the secondary sealing membrane 12. The line 14 therefore passes through the secondary sealing membrane 12 and the secondary thermally insulating barrier 13 via the sheath 21.

[0085] The bottom portion 15 is therefore welded to the top portion 16 inside the sheath 21, so that the sheath 21 guarantees the seal-tightness and the seal-tightness of the secondary membrane in the event of a break of the bottom portion 15, for example at the weld.

[0086] The bottom portion 15 therefore serves as a part of the primary sealing membrane 10 whereas the sheath 21 serves as a part of the secondary sealing membrane 12. Thus there are always two membrane layers, even at the line 14.

[0087] The line 14 then passes through the intermediate deck 8 of the ship 1 at an intermediate deck orifice 27. The intermediate deck orifice 27 has a diameter greater than the outer diameter of the sheath 21 so that there is a link play allowing the intermediate deck 8 to be deformed without causing deformation of the sheath 21 and of the line 14.

[0088] The intermediate deck 8 comprises, on its top surface, a coaming 22. The coaming 22 comprises a top part 23 and a lateral part 24 linking the top part 23 to the intermediate deck 8. The top portion 16 of the line 14 passes through the top part 23 of the coaming 22. The top portion 16 of the line 14 is tightly welded all around the top part 23 of the coaming 22.

[0089] The line 14 then passes through the space situated between the intermediate deck 8 and the top deck 9, called betweendeck, where the line is coated with an insulating sleeve 26 so that the low temperatures of the cryogenic gas contained in the line 14 do not cause a high thermal leak in the betweendeck.

[0090] The line 14 finally passes through the top deck 9 of the ship 1 at a top deck orifice 28. The top deck orifice 28 has a diameter greater than the outer diameter of the line 14 so that there is a link play allowing the top deck 9 to be deformed without causing deformation of the line 14.

[0091] The line 14 comprises a bellows compensator 25 on the second end of the top portion 16 remote from the bottom portion 15. The compensator ensures the fixing of the line 14 to a top surface of the top deck 9 of the ship 1. The bellows compensator 25 has corrugations configured to allow the thermal contraction of the line 14, notably of the top portion 16 which is made of stainless steel, a material which has a high expansion coefficient compared to the alloy of the bottom portion 15.

[0092] FIGS. 3 and 4 represent enlarged details III and IV of FIG. 2.

[0093] FIG. 3 makes it possible to distinguish the fixing of the primary sealing membrane 10 to the line 14 and the fixing of the secondary sealing membrane 12 to the sheath 21. In fact, the fixing of the primary sealing membrane 10 to the line 14 is produced using a flange ring 17 provided with a base and a flange. The flange of the ring 17 is welded to the line 14 and the base of the ring 17 is welded to the primary sealing membrane 10 which makes it possible to produce a tight fixing.

[0094] Likewise, the fixing of the secondary sealing membrane 12 to the sheath 21 is produced using a flange ring 17 provided with a base and a flange. The flange of the ring 17 is welded to the sheath 21 and the base of the ring 17 is welded to the secondary sealing membrane 12 which makes it possible to produce a tight fixing.

[0095] The base of the flange ring 17 can notably be of flat annular form comprising an inner diameter and an outer diameter. The flange of the flange ring 17 protrudes from the inner diameter of the base of the flange ring 17. The base and the flange of the flange ring have a thickness of 1.5 mm greater than the thicknesses of the primary and secondary sealing membranes 10, 12 of 0.7 mm.

[0096] FIG. 4 makes it possible to distinguish the junction between the bottom portion 15 and the top portion 16 of the line 14 and the fixing of the sheath 21 to the top portion 16. In fact, the welded fixing of the second end of the bottom portion 15 and of the first end of the top portion 16 of the line 14 is done with equal thickness of the two portions 15, 16 of the line 14. For that, the thickness of the first end of the top portion 16 decreases, for example linearly, from the thickness of the top portion 16 to the thickness of the bottom portion 15 so as to facilitate the welding of these portions 15, 16 and enhance the strength of the fixing.

[0097] The fixing of the sheath 21 to the top portion 16 is done by welding all around the top portion 16 just after the first end of the top portion 16 so that the sheath 21 is fixed to the top portion 16 at a point where its thickness is maximal but also close to the first end of the top portion 16 to minimize the length of the sheath 21 where that is not necessary to act as secondary sealing membrane 12.

[0098] FIGS. 5 and 6 represent schematic views of the primary 10 and secondary 12 sealing membranes and of the primary 11 and secondary 13 thermally insulating barriers. The sealing membranes 10, 12 and the thermally insulating barriers 11, 13 are produced according to the NO96 technology notably described in the document WO2012072906 A1.

[0099] Thus, the thermally insulating barriers 11, 13 are, for example, formed by insulating caissons 18 comprising a bottom panel and a cover panel that are parallel, spaced apart along the line of thickness of the insulating caisson 18, bearing elements 19 extending along the line of thickness, optionally peripheral partitions, and a heat insulating lining housed inside insulating caissons. The bottom and cover panels, the peripheral partitions and the bearing elements 19 are for example made of wood, for example plywood, or of a composite thermoplastic material. The heat insulating lining can consist of glass wool, cotton wool or a polymer foam, such as polyurethane foam, polyethylene foam or polyvinyl chloride foam or a granular or powdery materialsuch as perlite, vermiculite or glass woolor a nanoporous material of aerogel type. Also, the primary 10 and secondary 12 sealing membranes comprise a continuous sheet of metal strakes 20 with raised edges, said strakes 20 being welded by their raised edges onto parallel weld supports secured to the insulating caissons 18. The metal strakes 20 are, for example, made of Invar: that is to say an alloy of iron and of nickel with an expansion coefficient typically of between 1.2.10.sup.6 and 2.10.sup.6 K.sup.1, or an iron alloy with high manganese content with an expansion coefficient typically of the order of 7.10.sup.6 K.sup.1.

[0100] FIGS. 5 and 6 make it possible to distinguish where the line 14 passes through the sealing membranes 10, 12 and the thermally insulating barriers 11, 13. In fact, to avoid embrittling the structure of the caisson 18, it is preferable to avoid having the line 14 pass through the caisson on the ends of the caisson 18. Preferably, the line 14 passes through the primary thermally insulating barrier 11 and the secondary thermally insulating barrier 13 in a central zone of the caisson 18 between a plurality of bearing elements 19.

[0101] To facilitate the tight fixing of the primary sealing membrane 10 and the line 14 and the tight fixing of the secondary sealing membrane 12 and the sheath 21, it is preferable to avoid having the line 14 pass through the sealing membranes at the raised edges of the strakes 20. In fact, the zone where the edges are raised is geometrically complex and is already subject to the welding linking two adjacent strakes and a support web. That is why the line 14 passes through the sealing membranes 10, 12 in a flat zone of a strake 20 between two raised edges.

[0102] The strakes 20 of the primary sealing membrane 10 and of the secondary sealing membrane 12 passed through by the line 14 comprise a reinforced portion 32 so as to retain a continuity of the primary and secondary sealing membranes. In fact, the reinforced portion 32 represents a section of the strake 20 passed through by the line 14.

[0103] The reinforced portion 32 has a greater thickness than the rest of the strake 20, for example a thickness of 1.5 mm compared to a strake of 0.7 mm thickness. The reinforced portion 32 comprises a flat zone between two longitudinal raised edges. The line 14 passes through the reinforced portion 32 of the primary sealing membrane 10 and the reinforced portion 32 of the secondary sealing membrane 12 through the flat zone. The sheath 21 passes through the reinforced portion 32 of the secondary sealing membrane 12 also through the flat zone.

[0104] FIG. 7 represents a sealed and thermally insulating tank 2 filled with a liquefied gas and transported by a ship 1, the ship having fifteen degrees of list for example because of grounding.

[0105] In a normal case of use, with a ship having zero degrees of list, the tank 2 discharges the liquefied gas which is evaporated to avoid generating overpressures inside the tank 2 through a gas dome 29 passing through the ceiling wall of the tank 2 at its center.

[0106] In the case of an abovementioned grounding, with a ship having fifteen degrees of list, the gas dome 29 is fully immersed in the liquefied gas and can no longer fulfil its role of discharging the evaporated liquefied gas. To avoid having the overpressure damage the tank 2, two lines 14 situated at the ends of the ceiling wall and on either side of the gas dome 29 are placed in the tank 2 passing through the ceiling wall. The lines 14 are then linked to the main gas collector 30 of the ship 1 which conveys the gas to the engine compartment 3 and/or to a reliquefaction unit. The lines 14 are also linked to pressure relief valves 31 which open if the pressure is too great, thus redirecting a portion of the gas to the exhaust risers 4.

[0107] Preferentially, the lines 14 are linked to the main gas collector 30 and to the pressure relief valves 31 via the gas dome 29 outside the double hull 7.

[0108] Other details concerning the number and the position of the gas exhaust lines can be found in the publication WO2016120540 A1.

[0109] Referring to FIG. 8, a cutaway view of a methane tanker ship 1 shows a sealed and insulated tank 2 of generally prismatic form mounted in the double hull 7 of the ship 1.

[0110] As is known per se, loading/offloading pipelines 40 disposed on the top deck 9 of the ship 1 can be connected, by means of appropriate connectors, to a maritime or port terminal to transfer a liquefied gas cargo from or to the tank 2.

[0111] FIG. 8 represents an example of maritime terminal comprising a loading and offloading station 42, a submarine line 43 and an onshore installation 44. The loading and offloading station 42 is a fixed offshore installation comprising a mobile arm 41 and a riser 45 which supports the mobile arm 41. The mobile arm 41 supports a bundle of insulated flexible pipes 46 that can be connected to the loading/offloading pipelines 40. The orientable mobile arm 41 adapts to all methane tanker templates. A link line that is not represented extends inside the riser 45. The loading and offloading station 42 allows the loading and the offloading of the methane tanker 1 from or to the onshore installation 44. The latter comprises liquefied gas storage tanks 47 and link lines 48 linked by the submarine line 43 to the loading or offloading station 42. The submarine line 43 allows the transfer of the liquefied gas between the loading or offloading station 42 and the onshore installation 44 over a great distance, for example 5 km, which makes it possible to keep the methane tanker ship 1 at a great distance from the coast during the loading and offloading operations.

[0112] To create the pressure necessary to the transfer of the liquefied gas, pumps are implemented that are embedded in the ship 1 and/or pumps with which the onshore installation 44 is equipped and/or pumps with which the loading and offloading station 42 is equipped.

[0113] Although the invention has been described in association with a number of particular embodiments, it is quite obvious that it is in no way limited thereto and that it comprises all the technical equivalents of the means described and the combinations thereof provided the latter fall within the context of the invention.

[0114] The use of the verb comprise or include and its conjugate forms does not preclude the presence of elements or steps other than those stated in a claim.

[0115] In the claims, any reference symbol between parentheses should not be interpreted as a limitation on the claim.