RU2818607C2 - Liquefied gas transportation and/or storage tank - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: group of inventions relates to tank (1) for transportation and/or storage of liquefied gas. Reservoir contains insulating layer (2, 3) and a contamination removal system providing for removal of potential gas leaks, which may occur in insulating layer (2, 3). At that, reservoir (1) includes one sealed membrane (5), which limits internal volume (4), for production of liquefied gas, which is divided into two sections by horizontal median plane (200). Contamination removal system comprises one contaminant removal pipeline (8) provided with vertical resultant section (82) extending inside insulating layer (2, 3). Insulating layer (2, 3) comprises a gas outlet, wherein the vertical resultant section (82) extends into the gas outlet and comprises opening (83) which opens into insulating layer (2, 3) between the horizontal central plane (200) and lower plane (100).

EFFECT: neutralization of penetration into insulating layers of gas contained in reservoir.

19 cl, 9 dwg

Description

The present invention relates to a tank for transporting and/or storing liquefied gas. The invention relates to the field of maritime transportation and/or storage of liquefied gas.

In the shipbuilding industry, such as methane tankers, when transporting and/or storing liquefied gas, it is essential to maintain this gas in liquid form and at a low temperature, while said gas has a very low vaporization temperature. For this purpose, liquefied gas is stored in tanks containing a group of layers of insulation, providing both sealing through a sealed membrane and thermal protection through a thermal insulating layer.

The compaction of the tank is controlled by a monitoring system that interacts with the volume of the insulating layers. The contaminant removal system is designed to neutralize the penetration of gas contained in the tank into the insulating layers of the gas phase, for example, after a leak from the latter. In fact, if the seal of the sealed membrane is deficient, the liquefied gas is capable of leaking into the thermal insulating layer, evaporating and spreading in the insulating layer. To reduce the risk of penetration, the contaminant removal system contains a pipeline that allows gas to be sucked out of the cargo, which penetrates into the insulating layer.

In the case of liquefied natural gas (LNG) transport and a decontamination system comprising, in particular, an inert gas purge function using nitrogen, the decontamination system comprises a pipeline that opens into one of the insulating layers, specifically at the level of the ceiling wall of the tank. Since nitrogen has a density higher than that of natural gas in the gas state, penetration of the thermal insulation layer is reflected in the accumulation of natural gas in the gas state at the top of the thermal insulation layer, in particular at the level of the ceiling wall of the tank, allowing the contaminant removal system piping to also open into this area , suck out natural gas in a gaseous state.

A processing problem then arises if the reservoir is designed to contain a gas whose density is higher than that of the gas present in the thermally insulating layer prior to penetration, such as nitrogen. Thus, this applies to liquefied petroleum gas (LPG). In fact, LPG contains hydrocarbons, particularly propane and/or butane, which are heavier than the hydrocarbons present in LNG. Thus, LPG has a higher density than nitrogen used as the inert gas purge gas. Thus, a contaminant removal system is currently known to be inoperative if the reservoir contains a gas whose vapor density is greater than the vapor density of the gas used in the contaminant removal system.

The present invention solves this problem by installing a contaminant removal system compatible with the transport and/or storage of gas whose density is higher than the density of the gas used in the contaminant removal system, the transport gas being, for example, LPG and the purge gas being an inert gas is, for example, nitrogen.

The invention consists of a tank for transporting and/or storing liquefied gas, containing at least one insulating layer and a contaminant removal system that ensures the removal of potential gas leaks that may occur in the insulating layer, wherein the tank contains at least one sealed membrane limiting an internal volume intended for producing liquefied gas, wherein the internal volume is divided into two sections by a horizontal median plane, and the contaminant removal system contains at least one pipeline for removing contaminants, equipped with at least one vertical resulting section extending into the insulating layer, characterized in that the insulating layer contains at least one gas outlet, wherein the vertical resulting section of the pipeline for removing contaminants extends into the gas outlet and contains a diaphragm that opens into the insulating layer between the horizontal median plane and the lower plane passing through the lower wall of the tank.

The reservoir according to the invention for transporting and/or storing gas is functional for any type of vehicle or installation, for example land or sea. The invention finds preferable application in LPG transport vessels equipped with membrane tanks.

The gas contained in the reservoir is a gas whose density, in gas form, is higher than the density in gas form of the gas used to purge the reservoir with inert gas. The gas is contained in liquid form in the internal volume of the tank, the internal volume being limited by a compacted membrane of the insulating layer. A sealed membrane consists of a group of metal plates or strips, such as those made of Invar or stainless steel, welded together to provide a seal to the layer in question.

The internal volume of the reservoir is divided into two volume sections, which are essentially the same, by a horizontal median plane. In other words, if a measurement is taken between the bottom wall of a tank and the ceiling wall of the tank, then the plane in question passes through the point corresponding to that measurement divided by two and is parallel to the bottom plane.

The reservoir also contains a contaminant removal system which, as stated above, detects and/or removes potential gas leaks that may occur in the insulating layer. The contaminant removal system contains a group of pipelines, in particular a contaminant removal pipeline located in the insulating layer. It is through this contaminant removal line that inert gas purge gas is injected into or sucked from the insulating layer, and potential leak gas is sucked off, for example through a connection to a compressor external to the tank.

By vertical resulting section we mean a section of the pipeline that continues along the axis at an angle of less than 45° relative to the vertical axis. The vertical resulting section of the contaminant removal pipeline can be placed inside any of the insulating layers if the tank contains a group of them.

In order to force the vertical resulting section of the contaminant removal pipeline to circulate within the insulating layer, a passage is created inside the latter, forming a gas outlet passing through the insulating layer in question. The presence of this gas outlet makes it possible to place in it at least a vertical resulting section of the pipeline for removing contaminants.

The vertical resulting section of the pipeline for removing contaminants descends in the insulating layer to the diaphragm of the vertical resulting section of the pipeline for removing contaminants located inside the insulating layer between the horizontal plane and the plane passing through the bottom wall of the tank. In other words, the diaphragm of the vertical resulting section of the contaminant removal pipeline is at the same level as any point in the lower section of the internal volume of the tank.

According to one feature of the invention, the diaphragm opens into an insulating layer between the bottom plane and a plane parallel to the bottom plane and located at a distance of 230 mm +/- 100 mm above the bottom plane.

According to a preferred feature of the invention, the diaphragm opens into an insulating layer between the bottom plane and a plane parallel to the bottom plane and located at a distance of 230 mm +/- 15% above the bottom plane. In other words, the diaphragm is closer to the plane formed by the bottom wall than to the horizontal plane dividing the internal volume of the tank into two equal sections, more specifically, at a distance of 500 mm +/- 10% above the plane formed by the bottom wall. This is the area where LPG in gas form escaping from the tank can be sucked through a pipeline to remove contaminants. The inventors were in fact able to demonstrate that it was not necessary to force the contaminant removal pipeline to extend beyond the plane formed by the bottom wall of the tank. This alternative would also be more restrictive, given that there are corner sections of the tank below the plane formed by the bottom wall of the tank and that it is much more difficult to locate the gas outlet at the level of these corner sections.

According to one feature of the invention, the transport reservoir contains at least one primary insulating layer and one secondary insulating layer, each of which is formed by a sealed membrane and a thermal insulation layer, wherein a gas outlet is formed in the primary insulating layer or in the secondary insulating layer.

The presence of a group of insulating layers that make up the tank limits heat loss. In other words, a tank containing a group of insulating layers has more effective thermal protection. Each insulating layer contains a sealed membrane that provides a seal to the reservoir, and a thermal insulating layer that provides thermal protection through components of said thermal insulating layer, as described below. If the reservoir contains a group of insulating layers, then the primary insulating layer allows the internal volume of the reservoir to be limited by its sealed membrane.

According to one feature of the invention, the thermal insulation layer of the primary insulating layer and/or the secondary insulating layer contains a group of box-shaped sections or panels, between which a gas outlet passes.

These box-shaped areas are filled with thermal insulation such as glass wool or perlite, or panels formed from polyurethane that provide thermal insulation. To provide passage of the vertical resulting section of the contaminant removal pipeline into the primary insulating layer and/or the secondary insulating layer of the tank, box sections and/or panels are positioned within the insulating layers so as to limit, at least partially, the aforementioned gas outlet.

According to one feature of the invention, a diaphragm is formed at the free end of a section of a vertical resulting section of conduit to remove contaminants. As stated above, in order to perform its suction function, among other things, the diaphragm of the contaminant removal pipeline must be placed between the horizontal median plane and the lower plane, preferably at a distance of 230 mm +/- 100 mm, i.e. between 130 mm and 330 mm above the bottom plane. The contaminant removal piping diaphragm may preferably be placed at a distance of 230 mm +/- 15%, i.e. between 195.5 mm and 264.5 mm above the bottom plane. Thus, it is preferable to place the diaphragm at the free end of the vertical resulting section of the contaminant removal pipeline so that the diaphragm is as close to the bottom plane as possible.

According to one feature of the invention, the contaminant removal pipeline comprises at least one inlet portion connected to a vertical output portion and passing through at least a secondary thermal insulation layer of the secondary insulating layer. The inlet portion of the contaminant removal conduit extends horizontally or substantially horizontally and is connected to the vertical output portion of the contaminant removal conduit, for example by an elbow. Depending on the insulating layer in which the vertical resulting section of the contaminant removal pipeline is located, the inlet section of the contaminant removal pipeline passes through one or two thermally insulating layers of the insulating layers of the tank. Contaminant removal piping extends from the reservoir, for example, to a compressor external to the reservoir, which controls actions such as injecting gas for inert gas purge or sucking gas that penetrates the layer in question.

According to one feature of the invention, the vertical resulting section of the pipeline for removing contaminants is secured in the gas outlet with thermal insulation. The presence of a gas outlet creates a thermal bridge, that is, a preferred path along which heat passes. To prevent this phenomenon, thermal insulation of the pipeline is provided to remove contaminants with thermal insulation, and the space that surrounds it in the gas outlet. In addition, this thermal insulation can be supported by box-shaped sections of the insulating layer, providing the function of securing the vertical resulting section of the contaminant removal pipeline, which can extend vertically for several tens of meters. Securing the vertical resulting contaminant removal piping means that the thermal insulation immobilizes the vertical resulting contaminant removal piping in the longitudinal direction of the tank, transverse to the tank, and leaves it free in the vertical direction to accommodate the thermal expansion of the vertical resulting contaminant removal piping.

Various embodiments are applicable for the design of thermal insulation. The thermal insulation may, for example, comprise at least two half-shells surrounding the vertical resulting section of the contaminant removal pipeline. The half-shells can, for example, be made of polystyrene foam. Half-shells can be symmetrical or asymmetrical with respect to the pipe they surround. Each of the half-shells has a cavity shaped to complement the contaminant removal conduit, for example, a circular arc shape if the contaminant removal conduit is circular in shape. Once the half-shells have been placed around the vertical resulting contaminant removal pipeline section, the latter can be secured, for example, by means of adhesive tape. Another option for thermal insulation may be to fill the gas outlet, for example, with glass wool. The amount of glass wool present in the gas outlet makes it possible to exert a compressive force on the resulting vertical section of the pipeline to remove contaminants and act as thermal insulation.

According to one feature of the invention, the transverse dimension of the gas outlet is greater than the transverse dimension of the space located in the insulating layer, within which at least one rack supporting the reservoir extends. If the tank contains a group of insulating layers, then the support post extends through the secondary insulating layer and secures in position the box sections or panels that make up the secondary insulating layer. The support post also secures the insulating layer of the primary insulating layer by holding in position the box sections or panels that make up the primary insulating layer.

In order for the support post to pass through the secondary insulating layer, a gap is formed between two box-shaped sections of the thermal insulating layer of the secondary insulating layer through which the support post passes. This space, however, is less than the transverse dimension of the gas outlet, measured along parallel straight lines. This difference in size between the transverse dimension of the space in which the support column continues and the transverse dimension of the gas outlet can be verified by comparison, using any measuring instrument capable of measuring size, provided that these dimensions are measured along parallel straight lines and inscribed in one and the same same plane.

According to one feature of the invention, the rail covers one side of the gas outlet and forms a supporting surface on which the sealed membrane rests. The lath continues along the gas outlet, and the thermal insulation of the vertical resulting section of the pipeline for the removal of contaminants rests on this type of lath. The latter, for example, can be made of plywood or any rigid material similar to the material of the box-shaped sections and/or panels forming the thermal insulating layer of the insulating layer. The function of this rail is to form a bridge of material connecting two box sections and/or panels located on respective opposite sides of the gas vent to form a gas vent. The lath is aligned with the wall of the box sections and/or panels upon which the sealing membrane in question rests. In other words, the lath continues in line with the wall of the box sections and/or panels. The flat surface formed in this way ensures optimal positioning of the compacted membrane on the thermal insulating layer, despite the presence of a gas outlet inside the latter.

According to one feature of the invention, the contaminant removal system comprises at least one indicator tube, wherein the indicator tube comprises a first portion extending through a secondary thermal insulation layer of at least a secondary insulating layer, and a second portion that extends along at least one side wall reservoir, and which contains an inlet that opens between the horizontal median plane and the lower plane. The indicator tube is an outlet that allows gas samples to be taken and analyzed. Like the contaminant removal line, this type of indicator tube includes a portion extending through at least one thermally insulating layer of the reservoir. This section of the indicator tube is called the first section.

The second section of the indicator tube continues in a group of directions that follow the general shape of the tank, as seen in the vertical section, and perpendicular to the longitudinal direction of the tank. The second portion of the indicator tube extends along at least one of the side walls of the reservoir and includes an inlet that opens into an insulating layer between the horizontal median plane and a lower plane passing through the bottom wall of the reservoir. In other words, the inlet of the indicator tube and the diaphragm of the vertical resulting section of the contaminant removal pipeline are in substantially the same horizontal plane, thereby solving the problem of each of its respective functions.

According to one feature of the invention, at least one of the insulating layers contains box-shaped sections or panels arranged to form a channel in which the second section of the indicator tube continues. As well as the vertical resulting section of the pipeline for removing contaminants, a channel is provided to provide passage for the second section of the indicator tube. The channel is formed to extend along at least one of the side walls of the reservoir and correspond to the profile of the second section of the indicator tube.

According to one feature of the invention, the indicator tube is secured relative to the box sections by a fastening element. The second section of the indicator tube may have a significant length. Thus, its weight must be supported to prevent all types of mechanical accidents associated with this weight. The second section of the indicator tube can, for example, be secured to the box-shaped sections of the insulating layer by brackets screwed into the plywood wall of the box-shaped section or any other fastening element.

According to one feature of the invention, the contaminant removal conduit and/or indicator tube comprises segment(s) connected by a coupling. The presence of a coupling between the segments of the contaminant removal pipeline and/or indicator tube allows for simplified assembly by limiting the welds that must be made along the entire length of the contaminant removal system pipeline. The seal and mechanical connection between the coupling and the tube or conduit associated with it may be achieved by press fit, gluing or welding.

According to one feature of the invention, the inlet section of the contaminant removal pipeline and the first section of the indicator tube are located in the sleeve of the secondary insulating layer, the sleeve being configured to extend to the cofferdam of the vessel carrying the tank. As mentioned above, the contaminant removal conduit and indicator tube have respective inlet and first portions that extend at least partially through the secondary reservoir seal. These sections are connected to a system external to the reservoir containing, for example, a control device capable of triggering certain actions, such as, for example, injection of inert gas purge gas or suction through a pipeline to remove contaminants, or analysis of inert gas purge gas passing through through one of the insulating layers, and sampled through an indicator tube.

The inlet portion of the contaminant removal conduit and the first portion of the indicator tube are disposed within a sleeve that extends along each of the portions substantially to the junction between the inlet portion and the vertical output portion in the case of the contaminant removal conduit, and to the junction between the first portion and the second area in the case of an indicator tube. This bushing has sealing and mechanical retention functions as described in more detail below.

The sleeve extends to the vessel's cofferdam, passing through the wall of the cofferdam to ensure continuity of its function outside the tank. The sleeve is a tube containing an inlet section of the pipeline for removing contaminants and a first section of the indicator tube.

According to one feature of the invention, the sleeve includes a cover provided with openings through which an inlet section of the contaminant removal pipeline and a first section of an indicator tube extend. This cover consists of a partition substantially perpendicular to the longitudinal axis of the sleeve. It is located in the rubber dam of the ship and covers one end of the sleeve. To ensure continuity of the contaminant removal pipeline and the indicator tube, the cover is provided with holes allowing passage of the inlet section of the contaminant removal pipeline and the first section of the indicator tube. These holes are larger in size than the contaminant inlet portion and the first indicator tube portion, but are capable of providing a seal between the contaminant inlet portion, the first indicator tube portion, and the cap.

According to one feature of the invention, the inlet portion of the contaminant removal pipeline is supported in the sleeve by a support. As stated above, the contaminant removal pipeline is of considerable size, and the resulting vertical section of the contaminant removal pipeline can extend for several tens of meters. These factors significantly increase the weight of the vertical resulting section of the contaminant removal pipeline, which is supported by the upstream section of the contaminant removal pipeline. Thus, the upstream portion of the contaminant removal pipeline is subject to the weight of the vertical output portion of the contaminant removal pipeline, and requires mechanical support to be better able to withstand this force. Thus, a support, made from, for example, high-density polyethylene, is placed under the inlet section of the contaminant removal pipeline and rests on the sleeve to secure the inlet section in place and thus provide an improved ability to resist the weight created by the vertical resulting section of the contaminant. removing contaminants.

According to one feature of the invention, the sleeve includes a pipe and a metal cylinder positioned in line with the pipe, the metal cylinder extending through a secondary sealed membrane of the secondary insulating layer. In other words, the pipe is located in the rubber dam and continues into the secondary insulating layer section. The metal cylinder is in line with the pipe at the level of the secondary insulation layer, and continues into the primary insulation layer, passing through the secondary sealed membrane of the secondary insulation layer. The metal cylinder is made of a metal such as invar. A metal cylinder surrounds the inlet section of the contaminant removal pipeline and the first section of the indicator tube.

The present invention also consists of a transport vessel containing at least one tank, as described above, for transporting and/or storing liquefied gas, and a method for loading or unloading liquefied gas contained in the tank, as described above, for transporting and/or storage of liquefied gas, or the method of loading or unloading liquefied gas onto or from a vessel of that type.

Other features and advantages of the invention will become more apparent by means of the following description, on the one hand, and from a group of embodiments provided by way of non-limiting and illustrative example with reference to the accompanying schematic drawings, on the other hand, in which:

[Fig. 1] is a schematic view of a transportation and/or storage tank in the longitudinal and vertical plane.

[Fig. 2] is a schematic cross-sectional view of a transportation and/or storage tank in the transverse and vertical plane.

[Fig. 3] is an embodiment of thermal insulation placed between two box-shaped sections or panels of the thermal insulating layer of the tank according to the invention.

[Fig. 4] is a cross-sectional view of a contaminant removal pipeline surrounded by the thermal insulation embodiment of FIG. 3.

[Fig. 5] is a view of one embodiment of placing an insulating pipeline and a gas outlet inside the insulating layer in a section in the longitudinal and transverse plane.

[Fig. 6] is a perspective view of the placement of the indicator tube in the insulating layer.

[Fig. 7] is a sectional view of the indicator tube of FIG. 6, secured with a fastening element.

[Fig. 8] is a representation of contaminant removal system piping or tubing connected by a coupling.

[Fig. 9] is a cross-sectional view of the contaminant removal system at the bushing level of the insulating layers structure.

In the following description of a tank for transporting and/or storing liquefied gas and the elements that constitute it, the markers LV, LT and VT represent the position of the various elements in the detailed description. The longitudinal direction L corresponds to an axis parallel to the direction that passes through the insulating layer perpendicular to the latter, the vertical direction V corresponds to the vertical axis, and the transverse direction T corresponds to an axis perpendicular to the longitudinal axis L and the vertical axis V.

Figure 1 is a schematic view in the longitudinal vertical plane L, V of a tank 1 for transporting and/or storing liquefied gas, which will be referred to below and throughout the description as tank 1. The tank 1 is designed to be located, for example, in a ship. Here, the tank 1 is represented by a generally rectangular shape in this vertical plane L, V.

The reservoir 1 according to the invention contains at least one insulating layer 2, 3, and preferably two separate thermal insulating layers. The following description makes reference to these two barrier layers, but it should be understood that this description is given by way of example, and that the invention will be recognizable once a single barrier layer and the contaminant removal system of the invention exists. The technological features of a group of insulating layers are applied, mutatis mutandis, to a tank equipped with a single insulating layer.

Reservoir 1 contains a group of insulating layers. Insulating layers have both a thermal protective function and a sealing function. The thermal protection function is provided, for example, by box-shaped sections or panels located inside insulating layers, and filled, for example, with glass wool or perlite in the case of box-shaped sections, or formed of polyurethane in the case of panels.

In the embodiment shown in Figure 1, tank 1 comprises a primary insulating layer 2 and a secondary insulating layer 3, the latter surrounding the primary insulating layer 2. The fact that the primary insulating layer 2 is reinforced by a secondary insulating layer 3 provides tank 1 with double protection in the event of an incident. for example, in the event of a leak, simultaneously with thermal insulation of the fluid contained in the reservoir.

Each insulating layer is delimited by at least one wall, otherwise known as a sealed membrane. The primary seal layer 2 is delimited by a primary sealed membrane 5 and a secondary sealed membrane 6, the latter forming part of the secondary seal layer 3. The primary sealed membrane 5 has a shape similar to the general shape of the tank 1 and delimits the internal volume 4 of the tank 1. It is within this internal volume 4, a liquefied gas is stored, illustrated here by a liquid surface 25, this liquefied gas being in contact with the inner surface of the primary sealed membrane 5. The liquefied gas may, for example, be liquefied petroleum gas or, more generally, a gas whose density is in gas form above the density in the gaseous form of the gas that is present in the insulating layer in question.

The boundary between the primary insulating layer 2 and the secondary insulating layer 3 is delimited by a secondary sealed membrane 6, which also has a shape similar to the general shape of the tank 1. The secondary insulation layer 3 is delimited by a secondary sealed membrane 6 and the cofferdam wall 7 of the vessel. The primary sealed membrane 5 and the secondary sealed membrane 6 are in the form of metal, for example, Invar or stainless steel, partitions, plates or strips that seal the tank 1. If a leak occurs at the level of the primary sealed membrane 5, then the gas is contained within the primary insulating layer 2 of the secondary sealed membrane 6. The ship's cofferdam wall 7 provides a second degree of protection in the event of a leak in the primary sealed membrane 5 and the secondary sealed membrane 6.

The reservoir 1 includes an access opening 26 defined by a portion of the primary sealed membrane 5. The access opening 26 supplies a column for loading and/or unloading the reservoir 1, not presented herein.

According to the invention, the internal volume 4 of the tank 1 is divided by a horizontal median plane 200. Thus, the horizontal median plane 200 defines two substantially equal portions of the volume: a lower portion 41 located between the horizontal median plane 200 and the bottom wall 28 of the tank 1, and an upper portion 42 located between the horizontal median plane 200 and the ceiling wall 29 of the tank 1. In other words, the horizontal median plane 200 is halfway between the bottom wall 28 and the ceiling wall 29, i.e. on the vertical dimension V of the internal volume 4 divided by two. Also shown is a bottom plane 100. The bottom plane 100 is also horizontal and extends through the bottom wall 28 of the tank 1.

The reservoir 1 contains a contaminant removal system equipped with at least one conduit 8 for removing contaminants. A special function of the contaminant removal line 8 is to inject an inert gas purge gas such as nitrogen. The contaminant removal pipeline also has a suction function that can be activated if a leak is detected from the reservoir 1 into the primary insulating layer 2.

The contaminant removal pipeline 8 includes an inlet section 81, a resulting vertical section 82, and a diaphragm 83 located at the free end 84 of the contaminant removal conduit 8. The inlet portion 81 is generally horizontal and passes through at least one thermally insulating layer of the reservoir 1, as will be described below. The vertical resultant section 82 is connected to the inlet section 81 and extends substantially vertically to the diaphragm 83. By vertical resultant section 82 is meant a section of pipeline that extends along an axis at an angle of at least 45° with respect to the vertical axis V. This means that the section 82 can continue along a perfectly vertical straight line or along a straight line inclined at an angle of less than 45° with respect to the vertical axis to connect the bottom of the insulating layer in question.

The vertical resulting section 82 of the contaminant removal conduit 8 extends into one of the insulating layers of the reservoir 1. Thus, Figure 1 shows two embodiments illustrating the position of the contaminant removal conduit 8 within the reservoir 1, the two embodiments being alternative or cumulative.

On the left in figure 1, the vertical resulting section 82 of the contaminant removal pipeline 8 continues inside the primary insulating layer 2 to the diaphragm 83. Thus, the inlet section 81 of the contaminant removal pipeline 8 passes through the wall 7 of the vessel's cofferdam and the secondary sealed membrane 6. On the right in figure 1 the vertical resultant section 82 of the contaminant removal conduit 8 extends generally into the secondary seal layer 3. However, when the diaphragm 83 opens into the primary containment layer 2, the vertical resultant section 82 of the contaminant removal conduit 8 extends through the secondary seal diaphragm 6 to open into the primary insulating layer 2 through the diaphragm 83. In this embodiment of the contaminant removal pipeline 8, the inlet section 81 thus passes only through the cofferdam wall 7 of the vessel.

Whatever insulating layer the vertical resultant section 82 of the contaminant removal pipeline 8 passes through, a passage is formed within the insulating layer, within which the vertical resultant section 82 of the contaminant removal pipeline 8 continues. The box sections or panels forming the insulating layer in which the vertical resultant section 82 of the contaminant removal conduit 8 is located are thus arranged to form a gas outlet, as illustrated below.

As mentioned above, the diaphragm 83 of the contaminant removal line 8 opens into the primary insulating layer 2 or the secondary insulating layer 3. For example, it is through this diaphragm 83 that the inert gas purge gas exits or enters, or any fluid sucked out by the inert gas line 8 enters. removal of contaminants during the suction operation, thanks to penetration into the reservoir layer. The diaphragm 83 has the particular feature of being located between the horizontal median plane 200 and the bottom plane 100 passing through the bottom wall 28 of the reservoir. Therefore, this position makes it possible to suck out any gaseous emission from the internal volume 4 of the reservoir 1, which may occur after a sealing defect of the primary sealed membrane 5, since the gaseous emission has a higher density than the inert gas purge gas present in the insulating layer that has been penetrated .

The diaphragm 83 may preferably open between a bottom plane 100 passing through the bottom wall of the tank and a plane 110 parallel to the bottom plane 100 and located at a distance of 500 mm +/- 10% above the bottom plane 100. This position is ideal for optimal suction of the primary insulating layer 2 of the tank 1, taking into account that the gas form of the liquefied gas contained in the internal volume 4 of the tank 1 is denser than the gas present in this layer.

Figure 2 schematically represents the same tank 1 as shown in Figure 1, but viewed in cross-section in a transverse plane. From this point of view, the tank 1 has a substantially octagonal shape, the longer sides of which constitute the corresponding bottom wall 28 and the ceiling wall 29. This also applies to each of the insulating layers of the tank 1 and to the sealed membranes that compose it.

The elements of the contaminant removal system 10 are shown in Figure 2. The vertical resultant section 82 of the contaminant removal conduit 8 is at the center of the figure shown in dotted line, since it is not directly visible in Figure 2. This vertical resultant section 82 of the contaminant removal conduit 8 extends in the vertical direction V ceiling wall 29 until it opens near the bottom wall 28, and the diaphragm 83 opens into the insulating layer in question between the horizontal median plane 200 and the bottom plane 100, and preferably between the bottom plane 100 and the plane 110.

The vertical resultant section 82 of the removal line 8, also represented by a dotted line, continues into the gas outlet 18. The vertical resultant section 82 of the removal line 8 begins at the level of the primary insulating layer 2, as in the case of the location of the removal line 8 visible on the left. in figure 1.

Figure 2 also illustrates two indicator tubes 9 that form part of the contamination removal system according to the invention, more precisely, the second section 92 of the two indicator tubes 9. The indicator tube 9 also includes a first section, not visible in the figure, described in detail below.

Indicator tubes provide an outlet within the primary containment layer 2. This outlet is then used to obtain gas samples and analyze the latter to confirm the presence or absence of the vapor phase of the gas originally contained in the internal volume of the tank 1 in the primary containment layer 2, which is synonymous with leakage from the tank 1.

The reservoir 1 according to the invention contains at least one indicator tube 9. The embodiment shown in figure 2 contains two indicator tubes 9, but the technological features described below are applicable to at least one indicator tube. A second section 92 of indicator tube 9 extends along at least one side wall 32 of the reservoir. In other words, the second portion 92 of indicator tubes 9 follows the substantially octagonal shape formed, for example, by the primary sealed membrane 5. The presence of two indicator tubes results in the presence of two second portions 92, each of which extends along the side wall 32 of the reservoir, with said side The walls 32 are side walls located opposite each other and connecting the bottom wall with the ceiling wall. Thus, two second sections 92 bend around the internal volume 4 through the sides of the tank 1.

A second section 92 of indicator tubes 9 extends along at least one side wall 32 of the reservoir 1 and terminates at the diaphragm inlet 93 into the primary insulating layer 2. The inlet 93 is located between the horizontal median plane 200 and the bottom plane 100 passing through the bottom wall 28 of the reservoir. 1, and preferably between the bottom plane 100 and a plane 110 parallel to the bottom plane 100. Likewise, the inlet 93 is located within the primary insulating layer 2. Like the vertical resulting section 82 of the contaminant removal conduit 8, the second section 92 of the indicator tube 9 may extend either in the primary insulating layer 2 or in the secondary insulating layer 3.

The inlet 93 is preferably located in substantially the same horizontal plane as the diaphragm 83 to utilize the contaminant removal conduit in concert with the sampling and analyzes carried out by the indicator tube 9. Thus, the indicator tube 9 participates in the removal of contaminants from the reservoir 1 The contaminant removal pipeline 8 and the indicator tube 9 form at least part of the contaminant removal system of the tank 1.

Figure 3 is a perspective view of an embodiment of a thermal insulation 12 capable of supporting a vertical resultant section 82 of a contaminant removal conduit, and FIG. 4 is a cross-sectional view of a vertical resultant section 82 of a contaminant removal conduit 8 supported by the same thermal insulation.

The presence of a gas outlet creates thermal bridges, that is, preferential paths along which heat passes. Thermal insulation allows you to block these thermal bridges. In addition, the thermal insulation ensures that the vertical resulting section of the contaminant removal pipeline is limited in movement, more precisely, the movement is transverse to its common expansion axis, namely the vertical axis V. Thus, figure 3 represents a thermal insulation 12 capable of performing these functions.

The thermal insulation 12 may be composed of foam, such as polyethylene or polyurethane foam, thus serving as a thermal insulator. In Figure 3, the thermal insulation embodiment comprises a first half-shell 121 and a second half-shell 122 capable of interacting with each other by contact. Each half-shell 121, 122 contains a recess 123 of a complementary shape in the pipeline section for removing contaminants. Accordingly, when the two half-shells interact, the vertical resulting section of the contaminant removal pipeline is surrounded by thermal insulation 12, as illustrated in Figure 4. In this figure, each half-shell 121 and 122 is formed in one piece, but it is possible that one and/or the other of the half-shells is formed assembly of a group of parts.

In Figure 4, the vertical resulting section 82 of the contaminant removal pipeline 8 has a circular shape, visible in cross-section. Thus, the recesses in the thermal insulation 12 have the shape of a circular arc. According to one example, two half-shells of thermal insulation 12 are asymmetrical with respect to each other. The second half-shell 122 has larger dimensions than the first half-shell 121, which provides a deeper recess 123 of the circular arc in the second half-shell 122. Thus, the vertical resulting section 82 of the contaminant removal conduit 8 is first placed in the second half-shell 122, after which this assembly is covered first half-shell 121. The shape of the two half-shells provides direct contact between them, on respective opposite sides of the vertical resultant section 82 of the contaminant removal pipeline 8. As a result, the vertical resulting section 82 of the pipeline 8 for removing contaminants is free to expand in the vertical direction V and is immobilized transversely and longitudinally by thermal insulation 12.

In addition to the recesses, in each half-shell, which must match the shape of the vertical resulting section 82 of the contaminant removal pipeline 8, the half-shells can be of different shapes. In this way, imaginary shapes can be imagined to adapt to the shapes of the gas outlet created for the passage of the vertical resultant section 82 of the contaminant removal pipeline 8 so that the thermal insulation is able to rest on the box-shaped sections. Thus, thermal insulation 12 simultaneously performs the functions of thermal insulation and securing the vertical resulting section 82 of the pipeline 8 for removing contaminants.

The above is a non-exhaustive embodiment of the thermal insulation 12. By way of example, the thermal insulation 12 may equally consist of mineral wool, such as glass wool, inserted into the gas outlet to create a seal around the vertical resultant section 82 of the conduit 8 to remove contaminants. The thermal insulation properties of glass wool and the amount placed in the gas outlet produce the same functions as the half-shells described above.

Figure 5 is a horizontal sectional view of the insulating pipeline and the gas outlet inside the insulating layer. In this embodiment, the vertical resulting section 82 of the contaminant removal pipeline 8 continues inside the primary insulating layer 2 and is secured by thermal insulation 12, consisting of two half-shells 121 and 122, as shown in figures 3 and 4.

Figure 5 allows one to observe the design details of each insulating layer of the tank. The primary insulating layer 2 contains a primary sealed membrane 5, which limits the internal volume of the tank, and a primary thermal insulation layer 21, which contains a group of box-shaped sections 13. The secondary insulating layer 3 contains a secondary sealed membrane 6 and a secondary thermal insulation layer 31, also containing a group of box-shaped sections 13 Thus, the primary thermal insulating layer 21 is contained between the primary sealed membrane 5 and the secondary sealed membrane 6, while the secondary thermal insulating layer 31 is contained between the secondary sealed membrane 6 and the rubber dam wall 7.

A gap 504 is created within the secondary insulating layer 3 between two box-shaped sections 13 of the secondary thermal insulating layer 31. This gap 504 has a transverse dimension of 700. The gap 504 allows passage of a support post 500, which is connected to the rubber dam wall 7 by any fastening means. The support post 500 continues in the longitudinal direction L through the secondary insulating layer 3 and through the secondary sealed membrane 6. The support post 500 continues into the thermal insulating layer 21, more precisely, into the gas outlet 18, allowing the passage of the vertical resulting section 82 of the pipeline 8 to remove contaminants.

The support post portion 500 located in the gas vent 18 includes at least one plate 501 that extends in a transverse direction T within the gas vent 18. One end of the plate 501 is supported by a generally rectangular pin 502 attached to a box-shaped portion of the primary insulating layer 21. One the end of the support 500, located in the gas outlet 18, is equipped with a nut 503, which presses on the plate 501 in such a way as to secure the box-shaped sections 13 relative to the wall 7 of the cofferdam. Thus, this type of pressure exerted on the plates 501 by the nut 503 provides mechanical retention of the secondary insulating layer 3. In Figure 5, the support post 500 and its associated elements are shown at the level of the gas outlet 18, but the reservoir contains a group of support posts 500 arranged in a regular pattern at the level of the secondary insulating layer 3.

The plate 501 may also offer a support surface for a second half-shell 122 of the thermal insulation 12. To accommodate the thermal insulation 12, the gas outlet 18 has a transverse dimension of 800, substantially larger than the transverse dimension of the thermal insulation 12. Thus, the thermal insulation 12 is held transversely between two box-like sections 13 of the primary thermal insulation layer 21. forming the longitudinal sides of the gas outlet 18. The transverse dimension 800 has a size larger than the transverse dimension 700 of the gap 504 created inside the secondary insulating layer 3 for the passage of the support post 500.

As stated above, the thermal insulation 12 and therefore the vertical resulting section 82 of the contaminant removal conduit 8 is supported transversely by the box sections 13 and longitudinally by the plate 501 of the support post 500.

The longitudinal side of the gas outlet 18, more precisely, the longitudinal side located closer to the primary sealed membrane 5, is closed by a lath 600. The lath 600, for example, is made of plywood and extends vertically along the gas outlet 18. The transverse dimension of the lath 600 is therefore equal to or substantially equal to the transverse size 800 of the gas outlet 18. The rail 600 secures the vertical resulting section 82 of the pipeline 8 to remove contaminants longitudinally, supported on thermal insulation 12.

Another function of the lath 600 is to create a bridge of material between the plywood layers 132 of the box sections 13 of the primary thermal insulating layer 21, more precisely, the plywood layers 132 of the box sections 13 on which the primary sealed membrane 5 rests. Thus, the longitudinal dimension of the lath 600 is as follows: that the latter forms a flat surface with plywood layers 132 of box sections 13 that are adjacent to the gas outlet 18. This flat surface thus formed allows the primary sealed membrane 5 to be placed in a simple and secure manner during the manufacture of the tank.

Figure 6 is a view of the arrangement of the indicator tube 9 in the insulating layer. As stated above, the second portion 92 of the indicator tube 9 may be located in the primary or secondary insulating layer. The insulating layer shown in figure 6 can thus be any insulating layer of the reservoir.

The insulating layer structure is made of a group of box sections 13. These box sections 13 provide thermal insulation to each insulating layer, for example, due to glass wool or perlite contained in the box sections 13. For clarity and clarity, in particular relating to the second section 92 of the indicator tube 9, not all box sections 13 are represented. Like the vertical resulting section of the contaminant removal conduit extending into any insulating layer through a gas outlet, the second section 92 of the indicator tube 9 extends into the core of the insulating layer through a channel 19 formed by the gap between two rows of box sections 13 so that ensure the passage of the second section 92 of the indicator tube 9.

The second section 92 of the indicator tube 9 is located in the channel 19, more specifically, opposite the row of box sections 13 at the level of the contact surface 131 of the box section 13. Each box section 13 of this row includes a fastening element 145. The fastening element 145 may, for example, contain a rail 14 and bracket 15. The rack 14 is rigidly attached to the contact surface 131 of the box section 13. The rack 14 extends generally in a direction parallel to the longitudinal axis of the second section 92 of the indicator tube 9 along the contact surface 131 of the box section 13. The second section 92 of the indicator tube 9 is sandwiched between the bracket 15 and a rail 14. The bracket 15 is rigidly attached to the contact surface 131 of the box-shaped section 13 by means of a fastening means 151, in particular with one or more screws. Thus, the second section 92 of the indicator tube 9 is fixed inside the insulating layer by the combination of the contact surface 131 of the box sections 13, the rail 14 and the bracket 15, as shown in the sectional view in Figure 7.

This figure 7 allows us to observe the construction of the box section 13. As indicated above, the box section 13 contains walls formed by a group of layers of plywood 132. The interior of the box section 13 is filled with glass wool 133, but the box section 13 may, for example, contain perlite or another thermal insulating element .

Figure 7 shows that the second portion 92 of the indicator tube 9 is in direct contact with the contact wall 131 and the rail 14, with the majority of this contact continuing along two axes parallel to the longitudinal axis of the second portion 92 of the indicator tube 9. The bracket 15 presses the second portion 92 of the indicator tube 92. 9 to the contact wall 131 and to the rail 14. The bracket 15 includes a flat area 152 located opposite the contact wall 131, parallel to the latter. This flat area 152 secures the bracket 15 to the box portion 13 via a fastener 151. The fastener 151 provided herein is a screw through the plywood layers 132 of the box portion 13, but other fasteners may be provided. The bracket 15 contains a circular arc zone 153 that partially follows the circumference of the second section 92 of the indicator tube 9. The combination of the contact wall 131, the rail 14 and the bracket 15 thus ensures optimal fastening of the second section 92 of the indicator tube 9, which can extend along the insulating layer, in in which it is placed, without the risk of mechanical destruction or movement due to the length of the second section 92 of the indicator tube 9.

Figure 8 is a representation of segments 33 of the vertical resulting section 82 of the contaminant removal pipeline 8 or the second section 92 of the indicator tube 9 connected by a coupling 16. The vertical resulting section 82 of the contaminant removal pipeline 8 and the second section 92 of the indicator tube 9 have a substantial length of five up to forty meters, inclusive. These sections consist of a group of segments 33 connected to each other to form a longer section. These segments 33 can be connected, for example, by welding. However, to limit welding work, it is possible to connect these segments 33 by means of couplings 16. Thus, segment 33 may include a coupling 16 at each of its ends. The coupling 16 has a diameter slightly smaller than the segment 33 and is thus screwed onto the latter, after which it is secured, for example by gluing or force-fitting. This simplifies the assembly of contaminant removal pipe sections 8 and/or indicator tube 9.

Figure 9 is a cross-sectional view of the sleeve 300 and the structure of the various insulating layers in a plane passing through the contaminant removal conduit 8 of the contaminant removal system. Figure 9 represents an embodiment in which the vertical resulting section 82 of the contaminant removal conduit 8 and the second section 92 of the indicator tube 9 extend into the interior of the primary insulating layer 2, as shown on the left in Figure 1.

The inlet section 81 of the contaminant removal pipeline 8 and the first section 91 of the indicator tube 9 are generally horizontal and parallel to each other. These two sections extend in the longitudinal direction L through the secondary sealing membrane 6 and the cofferdam wall 7 of the vessel, housed within the sleeve 300, described in more detail below. Thus, the inlet section 81 of the contaminant removal pipeline 8 and the first section 91 of the indicator tube 9 pass through the entire secondary insulating layer 3 while passing through the secondary thermal insulating layer 31 in the longitudinal direction L until it opens into the primary insulating layer 2 after passing through the secondary seal membrane 6 and while passing through the primary thermal insulating layer 21. As mentioned above, the secondary insulating layer 3, as well as the primary insulating layer 2, contains a group of box-shaped sections 13 arranged in rows.

The contaminant removal conduit 8 and the indicator tube 9 extend into the interior of the primary insulating layer 2 by a vertical resulting section 82 of the contaminant removal conduit 8, and a second section 92 of the contaminant removal conduit 9, respectively connected to the inlet section 81 of the contaminant removal conduit 8 and to the first section 91 indicator tube 9 elbow. The vertical resulting section 82 of the contaminant removal pipeline 8 continues in the vertical direction V along the primary sealed membrane 5 and the secondary sealed membrane 6 inside the gas outlet 18. To ensure the passage of the vertical resulting section 82 of the contaminant removal pipeline 8, the box-shaped sections 13 of the primary insulating layer 2 are separated so to form a gas outlet 18, as explained above. The second portion 92 of the indicator tube 9 extends along at least one side wall of the reservoir as it extends generally in the transverse direction T, which is the reason why only a small portion of the second portion 92 of the indicator tube 9 is visible in Figure 9.

The inlet section 81 of the contaminant removal pipeline 8 and the first section 91 of the indicator tube 9 also extend beyond the cofferdam wall 7 of the vessel, outside the tank, to the cofferdam 17 located between the cofferdam wall 7 and another cofferdam wall 7 of the adjacent vessel tank. In this way, the decontamination line 8 and the indicator tube 9 extend to the decontamination unit present on the ship and allowing a group of operations to be started, for example gas injection for inert gas purge or suction through the decontamination line 8, or indeed gas analysis , present in the primary insulating layer 2 or in the secondary insulating layer 3 through the indicator tube 9.

The sleeve 300 extends in the longitudinal direction L from the rubber dam 17 to the primary insulating layer 2, as it passes through the secondary insulating layer 3. The sleeve 300 includes a pipe 301, which extends from the rubber dam 17 to the secondary insulating layer 3, while passing through the wall 7 of the ship's rubber dam. The sleeve 300 also includes a metal cylinder 302 in line with the pipe 301. This metal cylinder 302 extends from the secondary insulation layer 3 to the primary insulation layer 2 while passing through the secondary sealed membrane 6. The pipe 301 can be of any shape as it has dimensions , allowing to receive the inlet section 81 of the pipeline 8 for removing contaminants and the first section 91 of the indicator tube 9 inside its structure.

To maintain the seal of the tank, although the pipe 301 pierces the cofferdam wall 7 of the vessel, a group of elements around the pipe 301 provides this type of function. The cover 400 is located at the level of the end of the pipe 301 located in the rubber dam 17. The cover 400 is perpendicular to the longitudinal axis of the pipe 301 and is large enough to seal all diameters of the latter.

The cover 400 includes openings 401 that are sized substantially equal to the dimensions of the inlet section 81 of the conduit 8, and the first section 91 of the indicator tube 9 to pass through the cover 400, while ensuring that a seal is provided around the inlet section 81 of the conduit. 8 to remove contaminants and the first section 91 of the indicator tube 9. The presence of the cover 400, for example, prevents any escape of inert gas purge gas when the primary insulating layer 2 is inert.

The pipe 301 contains within its structure a support 402. The support 402 has the function of supporting the inlet section 81 of the contaminant removal conduit 8 and, where applicable, the first section 91 of the indicator tube 9, which is placed on the support 402. The contaminant removal conduit 8 has dimensions of several tens of meters and, accordingly, weighs several kilograms. A support 402 is interlocked between the wall of the pipe 301 and the inlet portion 81 to receive the weight of the contaminant removal line 8 and/or the first portion 91 to receive the weight of the indicator tube 9. The support 402 may, for example, be a block of high density polyethylene.

The metal cylinder 302 is in line with the pipe 301 and extends from the secondary insulating layer 3 to the primary insulating layer 2 as it passes through the secondary sealed membrane 6 providing a seal between the latter and the metal cylinder 302. The metal cylinder 302 is made of, for example, Invar and peripherally surrounds the inlet section 81 of the contaminant removal conduit 8 and the first section 91 of the indicator tube 9. A metal cylinder 302 extends the end of the pipe 301 located in the secondary insulating layer 3. Thanks to these elements, the sleeve 300 remains generally sealed in the event of a leak from the tank, despite to pierce the secondary sealed membrane 6 and the wall 7 of the cofferdam of the vessel, while ensuring the passage of the pipeline 8 to remove contaminants and the indicator tube 9 into the tank through the same hole.

Of course, the invention is not limited to the examples that have just been described, and numerous adaptations can be made to these examples without departing from the scope of the invention.

The invention, as has just been described, achieves the object that has been set for it, and thus makes it possible to provide a tank for transporting and/or storing liquefied gas, in particular LPG, containing a pollution removal system ensuring the removal of pollution from at least one thermally insulating reservoir layer when the latter contains a gas whose vapor density is greater than the vapor density of the gas present in the insulating layer in question or is used for inert gas purge operation. Embodiments not described herein may be used without departing from the context of the invention provided that, in accordance with the invention, they comprise a tank for transporting and/or storing liquefied gas in accordance with an aspect of the invention.

Claims (19)

1. A reservoir (1) for transporting and/or storing liquefied gas, including at least one insulating layer (2, 3) and a contaminant removal system (10), configured to remove potential gas leaks occurring in the insulating layer (2, 3), wherein the reservoir (1) includes at least one sealed membrane (5) delimiting the internal volume (4) to produce liquefied gas, which is divided into two sections by a horizontal median plane (200), while the system (10) removal of contaminants includes at least one pipeline (8) for removing contaminants, equipped with at least one vertical resulting section (82) extending into the insulating layer (2, 3), characterized in that the insulating layer includes at least one gas outlet ( 18), while the vertical resulting section (82) of the pipeline (8) for removing contaminants is made to continue inside the gas outlet (18) and includes a diaphragm (83) installed with the possibility of opening into the insulating layer (2, 3) between the horizontal median plane (200 ) and the lower plane (100) passing through the lower wall (28) of the tank (1). 2. Reservoir (1) according to claim 1, characterized in that the diaphragm (83) is installed with the possibility of opening into the insulating layer (2, 3) between the lower plane (100) and the plane (110) parallel to the lower plane (100) and located at a distance of 230 mm +/- 100 mm above the lower plane (100). 3. Reservoir (1) according to any one of paragraphs. 1 or 2, characterized in that it includes at least one primary insulating layer (2) and one secondary insulating layer (3), each of which is formed by a compacted membrane (5, 6) and a thermal insulation layer (21, 31), while the gas outlet (18) is formed in the primary insulating layer (2) or in the secondary insulating layer (3). 4. Tank (1) according to claim 3, characterized in that the thermal insulation layer (21, 31) of the primary insulating layer (2) and/or the secondary insulating layer (3) includes a group of box-shaped sections or panels (13), between which there is gas outlet (18). 5. Reservoir (1) according to any of the previous paragraphs, characterized in that a diaphragm (83) is formed at the free end (84) of the section (82) of the vertical resulting section of the pipeline (8) to remove contaminants. 6. Reservoir (1) according to any one of paragraphs. 3 or 4, characterized in that the pipeline (8) for removing contaminants includes at least one inlet section (81) connected to a vertical resulting section (82) and passing through at least a secondary layer (31) of thermal insulation of the secondary insulating layer ( 3). 7. Reservoir (1) according to any of the previous paragraphs, characterized in that the vertical resulting section (82) of the pipeline (8) for removing contaminants is fixed in the gas outlet (18) with thermal insulation (12). 8. Reservoir (1) according to any of the previous paragraphs, characterized in that the transverse dimension (800) of the gas outlet (18) is larger than the transverse dimension (700) of the space (504) located in the insulating layer (2, 3), inside which it continues along at least one post (500) supporting the reservoir (1). 9. Reservoir (1) according to any of the previous paragraphs, characterized in that it contains a rail (600) covering one side of the gas outlet (18) and forming a supporting surface for the sealed membrane (5). 10. Reservoir (1) according to any one of paragraphs. 3, 4 or 6, characterized in that the system (10) for removing contaminants includes at least one indicator tube (9) containing a first section (91) passing through a secondary layer of thermal insulation (31) of at least a secondary insulating layer (3 ), and a second portion (92) that extends along at least one side wall (32) of the reservoir (1), and which includes an inlet (93) configured to open between the horizontal median plane (200) and the bottom plane ( 100). 11. Reservoir (1) according to claim 10, characterized in that at least one of the insulating layers (2, 3) includes box-shaped sections or panels (13) arranged to form a channel (19) in which the second section continues (92) indicator tube (9). 12. Reservoir (1) according to any one of paragraphs. 10 or 11, characterized in that the indicator tube (9) is fixed relative to the box-shaped sections (13) by a fastening element (145). 13. Reservoir (1) according to any one of paragraphs. 10-12, characterized in that the pipeline (8) for removing contaminants and/or the indicator tube (9) contains segments (33) connected by a connecting coupling (16). 14. Reservoir (1) according to any one of paragraphs. 6, 10-13, characterized in that the inlet section (81) of the pipeline (8) for removing contaminants and the first section (91) of the indicator tube (9) are placed in the sleeve (300) of the secondary insulating layer (3), while the sleeve ( 300) is designed to extend into the cofferdam (17) of the vessel carrying the tank (1). 15. Reservoir (1) according to claim 14, characterized in that the sleeve (300) contains a cover (400) equipped with holes (401) made for passing the inlet section (81) of the pipeline (8) to remove contaminants and the first section ( 91) indicator tube (9). 16. Reservoir (1) according to any one of paragraphs. 14 or 15, characterized in that the inlet section (81) of the pipeline (8) for removing contaminants is supported by a support (402) on the sleeve (300). 17. Reservoir (1) according to any one of paragraphs. 14-16, characterized in that the sleeve (300) contains a pipe (301) and a metal cylinder (302) placed in line with the pipe (301) and passing through the secondary sealed membrane (6) of the secondary insulating layer (3). 18. A transport vessel, including at least one tank (1) according to any of the previous paragraphs, for transporting and/or storing liquid. 19. A method for loading or unloading liquefied gas contained in a tank (1), according to any one of paragraphs. 1-17, for transportation and/or storage of liquefied gas, or a vessel for transporting liquefied gas according to paragraph 18.