SEALED AND THERMALLY INSULATING TANK

A sealed and thermally insulating tank has a bottom wall and a ceiling wall where at least a first pipe and a second pipe pass through the ceiling wall. The tank is equipped with a support foot that passes through the bottom wall that is fastened to the load-bearing structure with a guide device that is fastened to the support foot. The guide device is configured to guide the first pipe and second pipe in translation in the vertical direction where the guide device has a first collar disposed around the entirety of the first pipe and a second collar is disposed around the entirety of the second pipe. A support plate is fastened to the support foot. A first linking arm links the first collar to the support plate. A second linking arm links the second collar to the support plate.

TECHNICAL FIELD

The invention relates to the field of sealed and thermally-insulating membrane tanks. The invention relates in particular to the field of sealed and thermally-insulating tanks for the storage and/or the transportation of liquefied gas at low temperature, such as tanks for the transportation of liquefied petroleum gas (LPG) at for example a temperature between −50° C. and 0° C. inclusive or for the transportation of liquefied natural gas (LNG) at approximately −162° C. The liquefied gas may equally be for example ammonia, carbon dioxide, hydrogen, ethane or ethylene. These tanks can be installed on land or a floating structure. In the case of a floating structure the tanks may be intended to transport liquefied gas or to receive liquefied gas serving as fuel for the propulsion of the floating structure.

TECHNOLOGICAL BACKGROUND

Sealed and thermally-insulating tanks for storing liquefied natural gas (LNG) onboard a ship and equipped with a loading/offloading tower are known. The loading/off-loading tower includes a tripod structure, that is to say it includes three vertical masts that are fixed to one another by crossmembers. Each of the vertical masts is hollow. Thus two of the masts form an offloading line of the tank and to this end are each associated with an offloading pump carried by the loading/offloading tower near its lower end. For its part the third mast forms a standby well enabling the lowering of a standby pump and offloading line in the event of failure of the other offloading pumps. The loading/offloading tower also carries loading lines that do not constitute one of the three masts. Such loading/offloading towers are described for example in the document WO2019211551. A tank may include one or more loading/offloading towers as required.

The loading/offloading tower is also equipped with a base that is fixed to the lower end of the three masts and supports the offloading pumps.

The loading/offloading tower further includes a guide device that is fixed against the lower face of the base and cooperates with a support foot that is fixed to the bottom wall of the supporting structure. Such a guide device aims to allow movement of the loading/offloading tower relative to the support foot in the heightwise direction of the tank in order to enable the loading/offloading tower to contract or to expand as a function of the temperatures to which it is subjected while preventing horizontal movements of the base of the loading/offloading tower.

SUMMARY

One idea behind the invention is to simplify the sealed and thermally-insulating tank and in particular the structure passing through the tank formed by the loading and offloading pipes while taking into account the phenomena of thermal contraction and expansion of the pipes.

In accordance with one embodiment the invention provides a sealed and thermally-insulating tank for storing liquefied gas integrated into a supporting structure, the tank including a bottom wall and a ceiling wall opposite the bottom wall in a heightwise direction of the tank, the bottom wall and the ceiling wall being fixed to the supporting structure, in which the ceiling wall has passed through it at least one first pipe and one second pipe, in which the tank is equipped with a support foot passing through the bottom wall and fixed to the supporting structure and a guide device fixed to the support foot, the guide device being configured to guide movement in translation in the heightwise direction of the first pipe and of the second pipe, in which the guide device includes a first collar disposed all around the first pipe, a second collar disposed all around the second pipe, a support plate fixed to the support foot, a first connecting arm connecting the first collar to the support plate, and a second connecting arm connecting the second collar to the support plate.

Thanks to these features the pipes are directly guided by the guide device which is itself fixed to the support foot without necessitating any intermediary parts as in the prior art at the base of the loading/offloading tower. Moreover, each of the pipes is individually guided by each of the collars. Thus if the pipes exhibit a different thermal contraction/expansion behavior the guide device enables guidance of the lower end of the pipes in movement in translation in the heightwise direction of the tank independently of one another. The collars also make it possible to prevent the lower end of the pipes moving.

The connecting arms and the support plate enable transfer to the support foot of forces to which the pipes are subjected having a component in the plane parallel to the bottom wall.

Embodiments of such a tank may have one or more of the following features.

In accordance with one embodiment stiffeners are formed along the first connecting arm and/or the second connecting arm.

In accordance with one embodiment the first connecting arm and/or the second connecting arm include(s) a connecting tube, preferably of circular section, having a first end and a second end, and a base connected to the first end of the connecting tube, the base being fixed, for example bolted or welded, to the support plate.

In accordance with one embodiment one end of at least one of the stiffeners is situated against the base of the first connecting arm or the second connecting arm.

In accordance with one embodiment one end of at least one of the stiffeners formed on the first connecting arm is situated against the first collar and preferably welded to the first collar.

In accordance with one embodiment one end of at least one of the stiffeners formed on the second connecting arm is situated against the second collar and preferably welded to the second collar.

In accordance with one embodiment the stiffeners include primary stiffeners and secondary stiffeners, the primary stiffeners extending from the first or second collar to the base of the first connecting arm or the second connecting arm, the secondary stiffeners having a first end situated against the first or second collar and a second end situated at a non-zero distance from the base of the first or second connecting arm.

In accordance with one embodiment the stiffeners are distributed all around the connecting tube with a regular angular pitch.

The stiffeners therefore make it possible to increase the stiffness and in particular the resistance to bending of the connecting arm.

In accordance with one embodiment the stiffeners are gussets.

In accordance with one embodiment the first collar includes a first cylindrical portion fixed to the first connecting arm and a second cylindrical portion fixed to said first cylindrical portion of the first collar.

In accordance with one embodiment the collar has a right cylinder shape with a circular, square or rectangular base, preferably a circular base.

In accordance with one embodiment the second collar has a first cylindrical portion fixed to the second connecting arm and a second cylindrical portion fixed to said first cylindrical portion of the second collar.

In accordance with one embodiment the second cylindrical portion is removably fixed to the first cylindrical portion by bolting it thereto.

In accordance with one embodiment an internal surface of the first collar and/or an internal surface of the second collar is or are equipped with at least one anti-friction pad extending for example in the heightwise direction.

In accordance with one embodiment an internal surface of the first collar and/or an internal surface of the second collar is equipped with a plurality of anti-friction pads extending for example in the heightwise direction and uniformly distributed on the internal surface.

In accordance with one embodiment the anti-friction pad is made of a material the static coefficient friction of which on steel is less than or equal to 0.2, preferably less than or equal to 0.1, for example equal to 0.04 in the case of PTFE anti-friction pads.

In accordance with one embodiment the first pipe is a liquefied gas loading pipe connected to a loading pump and the second pipe is a liquefied gas offloading pipe connected to an offloading pump.

In accordance with one embodiment the guide device is a main guide device and the ceiling wall has passed through it at least one third pipe, the tank being equipped with at least one secondary guide device, the secondary guide device being fixed to the first pipe or to the second pipe, the secondary guide device being configured to guide movement in translation in the heightwise direction of the third pipe, and the second guide device includes a third collar disposed all around the third pipe, a third connecting arm connecting the third collar to the first pipe or to the second pipe.

In accordance with one embodiment the tank includes in a direction of thickness from the exterior to the interior of the tank at least one thermally-insulating barrier and at least one sealing membrane supported by the thermally-insulating barrier and intended to be in contact with the fluid contained in the tank.

In accordance with one embodiment the tank includes successively in a direction of thickness from the exterior to the interior of the tank a secondary thermally-insulating barrier including insulating elements resting against the supporting structure, a secondary sealing membrane anchored to the insulating elements of the secondary thermally-insulating barrier, a primary thermally-insulating barrier including insulating elements resting against the secondary sealing membrane, and a primary sealing membrane anchored to the insulating elements of the primary thermally-insulating barrier and intended to be in contact with the fluid contained in the tank.

In accordance with one embodiment the invention also provides a ship for the transportation of a cold liquid product, the ship including a double hull and an aforementioned tank disposed in the double hull, the ship extending in a longitudinal direction.

In accordance with one embodiment the first connecting arm and the second connecting arm extend orthogonally to the longitudinal direction.

At sea, because of the action of the swell, the liquefied gas storage tanks are subjected to phenomena of sloshing of the cargo. These phenomena can be very violent inside the tank and consequently generate high forces in the tank and notably on the equipment thereof, such as the first pipe and the second pipe. These sloshing phenomena are greater in a transverse direction of the ship, namely a direction orthogonal to the longitudinal direction of the ship.

By disposing the connecting arms in the direction in which the sloshing phenomena are the strongest it is therefore possible for the connecting arms to function primarily in tension/compression and thus to limit the risks of damage through bending. The guide device is then able to withstand the main sloshing forces.

In accordance with one embodiment the first connecting arm and the second connecting arm extend in an arm direction at an angle between 75° and 105° inclusive to the longitudinal direction.

The arm direction is contained in a plane parallel to the bottom wall.

In accordance with one embodiment the first pipe and the second pipe are situated on either side of a transverse plane passing through the support foot that is orthogonal to the longitudinal direction, the support plate being positioned in a plane orthogonal to the transverse direction, the transverse direction being perpendicular to the longitudinal direction.

In accordance with one embodiment the support plate is fixed to the support foot by means of at least two connecting plates, the connecting plates being positioned in a plane orthogonal to the heightwise direction, the connecting plates being disposed against the support plate in the longitudinal direction so as to stiffen the support plate against bending.

In accordance with one embodiment the invention also provides a transfer system for a cold liquid product, the system including the aforementioned ship, insulated pipes arranged in such a manner as to connect the tank installed in the hull of the ship to a floating or terrestrial storage installation and a pump for driving a flow of cold liquid product through the insulated pipes from or to the floating or terrestrial storage installation to or from the tank of the ship.

In accordance with one embodiment the invention also provides a method of loading or offloading such a ship in which a cold liquid product is routed through insulating pipes from or to a floating or terrestrial storage installation to or from the tank of the ship.

DESCRIPTION OF EMBODIMENTS

In the present application the terms “internal” and “external” designate positions of elements of the sealed and thermally-insulating tank71relative to the interior of the tank, internal elements being closer to the interior of the tank than external elements.

FIG.1represents a sealed and thermally-insulating tank71for liquefied gas that is accommodated inside and anchored to the supporting structure1, the supporting structure3being for example formed by the double hull72of a ship70, as represented inFIG.6.

The tank71is a membrane tank for storing liquefied gas. The tank71has a multilayer structure including from the exterior to the interior in a direction of thickness of the wall a secondary thermally-insulating barrier including insulating elements resting against the supporting structure1, a secondary sealing membrane resting against the secondary thermally-insulating barrier, a primary thermally-insulating barrier including insulating elements resting against the secondary sealing membrane, and a primary sealing membrane2intended to be in contact with the liquefied gas contained in the tank71. The primary sealing membrane2defines an internal space3intended to receive the liquefied gas. Such membrane tanks are described in particular in the patent applications WO14057221, FR2691520 and FR2877638, for example.

The liquefied natural gas intended to be stored in the tank1may in particular be liquefied natural gas (LNG), that is to say a gas mixture including mostly methane and one or more other hydrocarbons. The liquefied gas may equally be ethane or liquefied petroleum gas (LPG), that is to say a mixture of hydrocarbons resulting from refining petroleum and essentially including propane and butane.

The tank71is a polyhedral tank including in particular a ceiling wall4fixed to an upper supporting wall5of the supporting structure1and a bottom wall6fixed to a lower supporting wall7of the supporting structure1, the ceiling wall4and the bottom wall6being spaced from one another in a heightwise direction H. The tank71also includes a front wall and a rear wall20, visible inFIG.2, spaced from the front wall in a longitudinal direction L. The tank71equally includes lateral walls that with the bottom wall6, the ceiling wall4, the front wall and the rear wall20close off the internal space3. The lateral walls are disposed on either side of the bottom wall6in a transverse direction T perpendicular to the longitudinal direction L. When the tank71is disposed in a ship70the longitudinal direction L corresponds to the longitudinal direction of the ship70.

FIG.1represents a part of the tank71of which only a portion of the ceiling wall4and a portion of the corresponding bottom wall6have been represented.

As can be seen inFIG.1the tank71includes a dome structure8and a manhole structure9, each structure8,9passing through an opening made in the ceiling wall4and the upper supporting wall5. As represented inFIG.1the manhole structure9is situated at a distance from the dome structure8.

The dome structure8in particular enables the liquefied gas loading and offloading pipes10,11to pass in sealed manner through the ceiling wall4. The manhole structure9for its part is for preserving access for an operative, for example for repair operations, and leads to the internal space3of the tank1.

The loading pipe10and the offloading pipe11therefore discharge into the internal space3of the tank1in order to load or offload liquefied gas to or from the latter. Moreover and as can be seen inFIG.1there is provided a support foot12passing through the bottom wall6and fixed to the lower supporting structure7. The support foot12is equipped with a guide device13configured to guide movement in translation in the heightwise direction of the loading pipe10and the offloading pipe11and to keep the loading and offloading pipes10,11vertical and on the axis of the dome structure8. The support foot12is therefore positioned near the axis of the dome structure8. As represented inFIG.2the dome structure8and the support foot12are respectively situated in an area of the ceiling wall4and an area of the bottom wall6closer to the rear wall20than the front wall, as.

The support foot12and the guide device13are described in more detail hereinafter.

FIGS.2to5represent the support foot12equipped with a guide device13in accordance with different embodiments.

As can be seen inFIG.3the support foot12has a shape of revolution of circular section extending in the heightwise direction H with a frustoconical lower part14that is connected at its end of smallest diameter to a cylindrical upper part15. The larger diameter base of the frustoconical part14is fixed to the lower supporting wall7of the supporting structure3. The frustoconical lower part14extends through the thickness of the bottom wall6of the tank71beyond the level of the primary sealing membrane2. The cylindrical upper part15is closed in sealed manner by means of a circular plate for example. The secondary and primary sealing membranes2are connected in sealed manner to the frustoconical lower part14by means of a secondary collar16and a primary collar17.

The guide device13is welded to the cylindrical upper part15of the support foot12. The guide device13includes a support plate18that is fixed to the cylindrical upper part15by means of two connecting plates19, as can be seen inFIG.3in particular. The connecting plates19are for example welded on the one hand to the cylindrical upper part15and on the other hand to the support plate18. The support plate18is positioned in a plane orthogonal to the longitudinal direction L while the connecting plates19are disposed parallel to one another in planes orthogonal to the heightwise direction H. The connecting plates19serve both for fixing the support plate18and as stiffeners.

The guide device13also includes a first connecting arm21and a second connecting arm22. Each connecting arm21,22includes a base23, for example in the form of a rectangular plate, that is fixed, for example bolted, to the support plate18. The base23of the first connecting arm21and the base23of the second connecting arm are disposed at two ends of the support plate18.

Each connecting arm21,22further includes a connecting tube24connected to the base23at a first end and extending along an axis parallel to the transverse direction T.

The guide device13finally includes a first collar25disposed all around the loading pipe10and fixed to a second end of the first connecting arm21and a second collar26disposed all around the offloading pipe11and fixed to a second end of the second connecting arm22. The first collar25and the second collar26have a central axis that is oriented vertically so as to guide the pipes10,11in movement in translation in the heightwise direction of the tank.

Each collar25,26is formed of a first cylindrical portion27welded to the second end of the connecting tube24. The first cylindrical portion27includes attachment zones28on either side of the first cylindrical portion27. Each collar25,26is also formed of a second cylindrical portion29including attachment zones28on either side of the second cylindrical portion29and disposed facing the attachment zones28of the first cylindrical portion27. The first cylindrical portion27is removably fixed to the second cylindrical portion29by bolting it thereto so as to form a cylindrical collar surrounding one of the pipes10,11.

As represented inFIG.3in particular the internal surface of the first collar25and the internal surface of the second collar26are equipped with a plurality of anti-friction pads30each extending in the heightwise direction and regularly distributed on the internal surface. The anti-friction pads30are configured to serve as contact surfaces limiting friction on the pipes10,11. The anti-friction pads are made of a material chosen for example from polytetrafluoroethylene (PTFE) or high-density polyethylene (HDPE).

In order to stiffen the connecting tubes24of the connecting arms21,22, in particular to resist any bending forces, stiffeners31,32extending in the longitudinal direction of the connecting arms21,22are welded along the connecting tubes24.

FIG.3represents a first embodiment of the guide device13whileFIGS.4and5represent a second embodiment that differs in the number and the disposition of the stiffeners31,32on the connecting tubes24.

In the first embodiment, depicted inFIG.3, the connecting tube24of the first connecting arm21includes two primary stiffeners31disposed on either side of the connecting tube24and two primary stiffeners31positioned in a plane orthogonal to the heightwise direction H and passing through the central axis of the connecting tube24. The primary stiffeners31of the first connecting arm21have a first end welded against the first collar25and a second end opposite the first end welded against the base23of the first connecting arm21so that the primary stiffeners31extend over all the dimension in the longitudinal direction L of the connecting tube24.

Also in the first embodiment the connecting tube24of the second connecting arm22includes two secondary stiffeners32disposed on either side of the connecting tube24and two secondary stiffeners32positioned in a plane orthogonal to the heightwise direction H passing through the axis of the connecting tube24. The secondary stiffeners32of the second connecting arm22further have a first end welded against the second collar26and a second end opposite the first end situated at a distance from the base23of the second connecting arm22so that the stiffeners32extend over a portion of the dimension in the longitudinal direction L of the connecting tube24.

In the second embodiment depicted inFIGS.4and5primary stiffeners31have been added all around the connecting tube24of the first connecting arm21compared to the first embodiment. In this embodiment the connecting tube24of the first connecting arm21is therefore equipped with six primary stiffeners31regularly distributed all around the connecting tube24and extending from the first collar26to the base23.

In other embodiments that are not represented the number and the arrangement of the stiffeners31,32on the connecting tubes24of the connecting arms21,22can vary. In fact, the connecting tubes24may be equipped with at least two stiffeners31,32, the stiffeners being exclusively primary stiffeners31or secondary stiffeners32or primary stiffeners31alternating with secondary stiffeners32.

InFIG.5the loading pipe10and the secondary pipes33have been represented with the support foot12and the guide device13. The loading pipe10therefore passes the first collar26of the guide device13. Where the secondary pipes33are concerned, they are also guided in movement in translation in the heightwise direction H by means of secondary guide devices34.

The secondary guide device34include on the one hand a secondary collar36disposed all around one of the secondary pipes33and a secondary connecting arm35fixed on the one hand to the secondary collar36and on the other hand to one of the pipes10,11. In the embodiment represented inFIG.5the secondary guide devices35are fixed to the loading pipe10and each secondary guide33is guided by a plurality of secondary guide device35distributed in the heightwise direction H.

Referring toFIG.6, a cutaway view of a methane tanker ship70shows a sealed and insulated tank71of prismatic general shape mounted in the double hull72of the ship. The wall of the tank71includes a primary sealed barrier intended to be in contact with the LNG contained in the tank, a secondary sealed barrier arranged between the primary sealed barrier and the double hull72of the ship, and two insulating barriers respectively arranged between the primary sealed barrier and the secondary sealed barrier and between the secondary sealed barrier and the double hull72.

In a manner known in itself loading/offloading pipes73disposed on the top deck of the ship may be connected by means of appropriate connectors to a maritime or harbor terminal to transfer a cargo of LNG from or to the tank71.

FIG.6shows an example of a maritime terminal including a loading and offloading station75, an underwater pipe76and a terrestrial installation77. The loading and offloading station75is a fixed off-shore installation including a mobile arm74and a tower78that supports the mobile arm74. The mobile arm74carries a bundle of insulated flexible tubes79that can be connected to the loading/offloading pipes73. The orientable mobile arm74adapts to all methane tanker loading gauges. A connecting pipe that is not shown extends inside the tower78. The loading and offloading station75enables loading and offloading of the methane tanker70from or to the terrestrial installation77. The latter includes liquefied gas storage tanks80and connecting pipes81connected via the underwater pipe76to the loading or offloading station75. The underwater pipe76enables transfer of the liquefied gas between the loading or offloading station75and the terrestrial installation77over a great distance, for example 5 km, which enables the methane tanker ship70to remain at a great distance from the coast during loading and offloading operations.

Pumps onboard the ship70and/or pumps equipping the terrestrial installation77and/or pumps equipping the loading and offloading station75are used to generate the pressure necessary to transfer the liquefied gas.

Although the invention has been described in connection with a plurality of particular embodiments, it is obvious that it is in no way limited to them and that it encompasses all technical equivalents and combinations of the means described if the latter fall within the scope of the invention.

The use of the verb “to include” or “to comprise” and conjugate forms thereof does not exclude the presence of elements or steps other than those stated in a claim.

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