RELATED APPLICATIONS

The present application is a national stage of International Application No. PCT/FR2019/050252, filed Feb. 5, 2019, which claims priority to French Patent Application No. 1851035, filed Feb. 7, 2018, both of which are incorporated herein by reference.

TECHNICAL FIELD

The invention relates to the field of sealed and thermally insulating membrane-type tanks for storing and/or transporting a liquefied gas, and in particular tanks carried on board ships or other floating structures.

The tank(s) may be intended to transport a large cargo of liquefied gas and/or to receive liquefied gas used as fuel for propelling the ship.

TECHNOLOGICAL BACKGROUND

Ships for transporting liquefied natural gas have a plurality of tanks for storing the cargo. The liquefied natural gas is stored in these tanks, at atmospheric pressure, at around −162° C. and is thus in a liquid-vapor two-phase state of equilibrium such that the heat flux applied through the walls of the tanks tends to cause the liquefied natural gas to evaporate.

In order to avoid the generation of overpressures inside the tanks, a tank of a methane tanker is associated with a pipe for evacuating the vapor, referred to as a gas dome, which is arranged in the ceiling wall of the tank, generally at the centerline of the ship, and connected to the main vapor collector of the ship and to a riser mast. The vapor thus collected can then be transferred to a re-liquefying facility in order that the fluid can then be reintroduced into the tank, to energy production equipment or to a riser mast provided on the deck of the ship.

A gas dome structure suitable for a tank wall having a bonded composite membrane is described in particular in the publication WO-A-2013093261 or WO-A-2014128381. However, these structures exhibit large dimensions and are fairly complex.

SUMMARY

An idea underlying the invention is to propose a relatively simple structure for passing a sealed pipe into a sealed and thermally insulating membrane-type tank, in particular a small-diameter pipe that can be used to collect or inject liquid or vapor.

According to one embodiment, the invention provides an installation for storing and transporting a liquefied gas, the installation having:

a load-bearing structure having a load-bearing wall provided with an opening,

a sealed and thermally insulating tank incorporated in said load-bearing structure, said sealed and thermally insulating tank having a tank wall mounted on an inner surface of the load-bearing wall, the tank wall having at least one thermally insulating barrier and at least one sealing membrane that are superposed in a thickness direction of the tank wall,

a sealed metal pipe that is fitted in the opening in the load-bearing wall and passes through the tank wall parallel or obliquely to said thickness direction so as to define a fluid passage between the inside and the outside of the tank,

a sealed metal sheath that is disposed around the sealed pipe and fitted in the opening in the load-bearing wall, the sealed sheath having a longitudinal portion extending parallel to the sealed pipe through the thickness of the thermally insulating barrier at least as far as the sealing membrane, the sealing membrane having an opening through which the sealed pipe passes and being joined to the sealed sheath in a sealed manner all around said opening,

wherein the load-bearing structure comprises a coaming that protrudes from an outer surface of the load-bearing wall and is disposed around the sealed pipe, the sealed pipe being supported by a top wall of the coaming,

the longitudinal portion of the sealed sheath having an outer end that is disposed outside the load-bearing wall and attached to the top wall of the coaming or to the sealed pipe in a sealed manner, all around the sealed pipe.

By virtue of these features, the sealed pipe can be passed through the sealed and insulating tank wall in a simple and reliable manner, without putting the sealing of the tank wall at risk. In particular, the transmission of mechanical loads between the load-bearing wall and the sealing membrane can be very substantially limited by the presence of the sealed sheath and of the coaming.

According to embodiments, such an installation may have one or more of the following features.

The or each sealed sheath can be fixed to the load-bearing structure in various ways, directly or indirectly. According to one embodiment, the outer end of the sealed sheath is attached to the top wall of the coaming. According to one embodiment, the longitudinal portion of the sealed sheath constitutes a lateral wall of the coaming, the longitudinal portion of the sealed sheath being welded to the load-bearing wall around the opening in the load-bearing wall, the top wall of the coaming being fixed to the outer end of said longitudinal portion. According to one embodiment, the sealed sheath also has a support ring that is fixed at the outer end of the longitudinal portion of the sealed sheath and extends radially toward the inside of the sealed sheath, the support ring having an inner edge attached to the sealed pipe all around the sealed pipe.

Preferably in this case, the support ring is disposed in the coaming, in particular in an outer half of the coaming.

According to one embodiment, the sealing membrane is a metal membrane that is welded to the sealed sheath in a sealed manner by way of a flanged ring. According to one embodiment, the metal membrane has a series of parallel corrugations spaced apart at a regular pitch, the opening in the sealing membrane through which the sealed pipe passes having dimensions smaller than the regular pitch and being disposed in a flat region of the metal membrane between two corrugations. According to embodiments, such a metal membrane may be the only sealing membrane of the tank, for example for an LPG tank, or a primary membrane of a tank have a plurality of sealing membranes. In the latter case, an annular space situated between sealed sheath the sealed pipe may be in communication with the interior space of the tank.

According to one embodiment, the tank wall has a primary sealing membrane intended to be in contact with the liquefied gas, a secondary sealing membrane arranged between the primary sealing membrane and the load-bearing wall, a secondary thermally insulating barrier arranged between the secondary sealing membrane and the load-bearing wall, and a primary thermally insulating barrier arranged between the secondary sealing membrane and the primary sealing membrane. In this case, the sealed sheath may serve to join the primary sealing membrane or the secondary sealing membrane. It is also possible to provide a secondary sealed sheath to join the secondary sealing membrane and a primary sealed sheath for joining the primary sealing membrane.

According to one embodiment, said sealed metal sheath has a connecting plate extending in the region of the secondary sealing membrane all around the longitudinal portion of the sealed sheath, the secondary sealing membrane having a composite ply bonded to the connecting plate in a sealed manner all around the opening in the secondary sealing membrane.

According to one embodiment, a filling of insulating material is arranged in a gap between the longitudinal portion of the sealed sheath and the sealed pipe.

According to one embodiment, the primary sealing membrane has an opening for the sealed pipe to pass through, an edge of said opening being joined to the sealed pipe in a sealed manner all around the sealed pipe.

According to one embodiment, said sealed metal sheath is a secondary sealed sheath and the installation also has a primary sealed metal sheath that is disposed around the sealed pipe between the sealed pipe and the secondary sealed sheath, the primary sealed sheath having a longitudinal portion extending parallel to the sealed pipe through the thickness of the thermally insulating barrier at least as far as the primary sealing membrane, the sealing membrane having an opening through which the sealed pipe and the primary sealed sheath pass and being joined to the primary sealed sheath in a sealed manner all around said opening.

According to one embodiment, a filling of insulating material is arranged in a gap between the longitudinal portion of the secondary sealed sheath and the longitudinal portion of the primary sealed sheath.

According to one embodiment, the longitudinal portion of the primary sealed sheath has an outer end that is disposed outside the load-bearing wall and attached to the top wall of the coaming or to the sealed pipe in a sealed manner, all around the sealed pipe. According to one embodiment, the primary sealed sheath also has a primary support ring that is fixed at the outer end of the longitudinal portion of the primary sealed sheath and extends radially toward the inside of the primary sealed sheath, the primary support ring having an inner edge attached to the sealed pipe all around the sealed pipe.

Such a sealed pipe may serve for various functions, for example to collect the liquefied gas from the interior space of the tank or to inject the liquefied gas into the interior space, in particular a vapor phase into a top portion of the tank or a liquid phase into a bottom portion of the tank.

According to one embodiment, the sealed pipe has a collection end that opens into the tank at an upper portion of the tank in order to collect a vapor phase of the liquefied gas. Such a pipe for collecting the vapor phase in the tank can be provided with a relatively small diameter, for example less than 300 mm, and in particular less than 100 mm.

According to one embodiment, the other end of the sealed pipe is connected to a gas dome of the tank and/or to a main vapor collector of the installation and/or to overpressure valves of the tank.

According to one embodiment, the tank wall is a ceiling wall. Such a pipe for collecting the vapor phase in the tank can be provided at different locations in the upper portion of the tank, in particular in the vicinity of a longitudinal edge and/or of a lateral edge of the ceiling wall of the tank.

The load-bearing structure can be realized in different ways, in particular in the form of an onshore construction, in the form of a transportable self-supporting metal casing, or in the form of a floating structure.

Thus, the invention also proposes a floating structure, in particular a methane tanker, having a double hull and an abovementioned installation installed in the double hull, wherein the load-bearing structure of the installation is formed by internal walls of the double hull.

According to embodiments, such a floating structure may have one or more of the following features.

According to one embodiment, the tank wall is a ceiling wall and the load-bearing wall is an intermediate deck of the floating structure, the floating structure also having an upper deck parallel to and spaced apart from the intermediate deck, the sealed pipe also having an upper portion extending above the coaming as far as the upper deck and through an opening in the upper deck, a sleeve made of insulating material being arranged around said upper portion between the coaming and the upper deck.

According to one embodiment, the floating structure also has an accordion-like compensator that extends along the upper portion of the pipe above the upper deck and has a lower end joined to the upper deck around the opening in the upper deck and an upper end joined to the sealed pipe all around the sealed pipe, the compensator serving to close the opening in the upper deck in a sealed manner around the sealed pipe, allowing thermal contraction of the sealed pipe.

According to one embodiment, the floating structure is a ship intended to transport liquefied gas, such as a methane tanker or a ship for transporting LPG for example. According to another embodiment, the ship is a ship propelled by drive means supplied by the vapor phase of the liquefied gas. These embodiments can be combined.

According to one embodiment, the floating structure is an inshore or offshore barge, a floating storage regasification unit (FSRU) or a floating production storage and offloading (FPSO) unit.

According to one embodiment, the invention also provides a method for loading or offloading from such a floating structure, wherein a liquefied gas is passed through insulated pipelines from or to a floating or onshore storage installation to or from a tank of the floating structure.

According to one embodiment, the invention also provides a system for transferring a cryogenic fluid, the system having the abovementioned floating structure, insulated pipelines arranged so as to connect the tank installed in the double hull to a floating or onshore storage installation and a pump for conveying a flow of cryogenic fluid through the insulated pipelines from or to the floating or onshore storage installation to or from the tank of the floating structure.

