Fluid storage system comprising access device for performing maintenance operations and storage method

Abstract

An underground storage system (1) for fluid storage. The device comprises a cavity (2) formed in a land (3), the cavity (2) having a bottom (6); a holding element (4) comprising at least one opening; at least one tank (5) having a longitudinal axis, a lower end (13) closed by a first closure device (12) and an upper end (14) closed by a second closure device (15); and means for access from the outside of the cavity (2), comprising at least one of the following: means for access to each tank (5), means for access to the inside of the tank (5), and means for access to the contents of the cavity (2).

Description

Technical Field

[0001] This invention relates to underground storage, particularly the storage of fluids (e.g., hydrogen or oxygen). More specifically, this invention relates to the maintenance of fluid storage systems, particularly high-pressure fluid storage systems, i.e., systems with pressures between 100 bar and 1200 bar, more specifically between 200 bar and 500 bar.

[0002] The present invention also relates to a method for underground fluid storage.

[0003] Systems used for storing fluids must be inspected regularly, especially when the fluids pose significant risks, particularly the risk of explosion or fire.

[0004] In underground facilities used to store fluids that pose a risk of explosion or fire, various levels of maintenance must be provided. Specifically, it must be possible to maintain the upper level of the storage system (which may be external), the storage tanks of the storage system, and the cavities that house the tanks.

[0005] Therefore, maintenance operations require various access points, which are difficult to set up when the storage system to be inspected is compact and / or installed tens or hundreds of meters underground. Furthermore, certain maintenance operations, such as replacing components with limited lifespans in storage tanks, are difficult to perform. Summary of the Invention

[0006] The object of this invention is to provide a solution ranging from inspecting to replacing components of a fluid storage system by optimizing the ease of access to the tank and / or cavity. This invention also aims to optimize the frequency at which certain tank components need to be replaced due to wear. More specifically, this invention also aims to optimize the lifespan of sensitive components of the tank, thereby limiting the intervention required to replace said sensitive components.

[0007] This invention relates to an underground storage system for storing fluids. The system includes: a cavity formed in a plot of land, the cavity having a bottom; a retaining element including at least one opening; and at least one tank having a longitudinal axis, a lower end closed by a first sealing device, and an upper end closed by a second sealing device. The upper end includes a support member, which is assembled to the retaining element such that the tank is suspended within the cavity. The storage system also includes means for access from outside the cavity, comprising at least one of the following: means for accessing each tank, means for accessing the interior of the tank, and means for accessing the contents of the cavity.

[0008] Advantageously, the means for accessing each storage tank includes a channel formed on the periphery of the retaining element.

[0009] According to one embodiment, the channel surrounds the retaining element. In other words, the channel is formed around the retaining element.

[0010] According to one embodiment, the channel is formed on the upper surface of the retaining element, for example, on a flange that forms the outer contour of the retaining element. Since it has no openings for the tank, forming a channel on such a flange ensures that the flange has a lower surface area sufficient to allow the retaining element to rest stably on the ground surface, while providing a completely unobstructed upper flange surface.

[0011] In one embodiment, the channel may be formed together around the retaining element and on its upper surface.

[0012] Advantageously, the means for accessing each tank includes a corridor located on the retaining element. This corridor advantageously enables access from the retaining element to one or more tanks that cannot be accessed from a channel formed on the periphery of the retaining element.

[0013] Such passageways or corridors are unobstructed surfaces that allow operators to move directly to access the tanks arranged along the free surface. Typically, with the aid of such passageways or corridors, operators can directly access the tanks to operate the first closure device.

[0014] The device for accessing the interior of the storage tank includes a sacrificial auxiliary component inserted between the second closure device and the support member.

[0015] Advantageously, the sacrificial auxiliary component is removable. Therefore, it can be removed from the tank for access inside the tank. Furthermore, the sacrificial auxiliary component is an easily replaceable element, for example, by tightening / loosening the closure three times during maintenance operations, thus allowing for a longer service life of the support components.

[0016] According to one embodiment, the means for accessing the interior of the storage tank includes a plurality of sacrificial auxiliary components removably inserted between the second closure device and the support member, each sacrificial auxiliary component enabling the support portion to remain in place for a longer period of time.

[0017] According to one embodiment, the device for accessing the contents of a cavity includes at least one suction tube for a fluid and / or solid and at least one injection tube for a fluid and / or solid. The injection tube enables the injection of fluid and / or solid into the cavity, typically to surround one or more reservoirs inserted into the cavity with the fluid and / or solid. Similarly, the pumping tube enables the removal of the fluid and / or solid from the cavity in a manner that allows pumping and circulation of the fluid and / or solid present at the bottom of the cavity.

[0018] According to one embodiment, the device for accessing the contents of a cavity includes a portion outside the cavity, in which an injection tube and / or aspiration tube are opened and / or controlled from the portion outside the cavity.

[0019] Advantageously, the storage tank includes at least one metal pipe having at least one end with at least one threaded portion.

[0020] The storage tank comprises at least two metal tubes assembled by threaded connection to form a tubular column.

[0021] Preferably, the support member includes a threaded portion. The metal tube or column is assembled with the support member by tightening a threaded portion of the metal tube or one of the metal tubes forming the column together with the threaded portion of the support member.

[0022] Preferably, the storage tank is suspended inside the cavity, such that there is an axial gap between the first sealing device of the storage tank and the bottom of the cavity, which is suitable for absorbing the axial thermal expansion of the storage tank.

[0023] Advantageously, the axial clearance suitable for absorbing the axial thermal expansion of the storage tank satisfies the following inequality:

[0024] [Mathematical Formula 1]

[0025] Where: G is the length of the axial clearance in meters, L is the length in meters between the tank and the retaining element, β is the geothermal gradient of the land in degrees Celsius per meter, and α is the coefficient of thermal expansion of the metal used to manufacture the tank in degrees Celsius per meter.

[0026] Preferably, the support member includes an upper threaded portion, and the sacrificial auxiliary member is sealed to the support member by tightening on the upper threaded portion.

[0027] For example, the first sealing device and / or the second sealing device are adapted to seal the storage tank in a sealed manner via a threaded connection. For example, the first sealing device is screwed onto the upper threaded portion of the sacrificial auxiliary component.

[0028] According to one embodiment, the storage system includes a plurality of tanks, each tank having a longitudinal axis, a lower end and an upper end, the upper end of each tank being adapted to be assembled to a retaining element by a corresponding support member, such that each tank is suspended inside a cavity.

[0029] Advantageously, the cavity includes at least one waterproof lining made of concrete, cement or steel.

[0030] The present invention also relates to an underground storage method for storing fluids using a storage system as described above. The method includes at least the following steps: A cavity is formed in the plot of land, the cavity having a bottom; A retaining element is provided, which includes at least one opening adapted to receive a support member; At least one storage tank is provided, the storage tank having a longitudinal axis, a lower end and an upper end, the upper end including a support member; A first sealing device is provided, suitable for sealing the storage tank at its lower end, and a second sealing device is provided, suitable for sealing the storage tank at its lower end; The upper end is assembled to the retaining element by a support component, so that the storage tank is suspended inside the cavity; and A device for access from outside the cavity is formed, comprising at least one of the following: a device for accessing each storage tank, a device for accessing the interior of the storage tank, and a device for accessing the contents of the cavity.

[0031] definition The “lower end” of a storage tank refers to the end of the tank located near the bottom of the cavity. This “lower end” is defined as the opposite of the end referred to as the “upper end” of the tank, which is positioned near the retaining element and thus close to the ground.

[0032] "Axial clearance" refers to the length measured along the longitudinal axis of the tank between the first sealing device (near the bottom of the cavity) and the bottom of the cavity. It should be noted that the tank is not necessarily perfectly vertical. In this case, the longitudinal axis of the tank forms an angle with the vertical in the reference frame (x;y). The maximum value of this angle is 15°. In this case, the axial clearance is measured by orthogonal projection onto the vertical axis passing through the point on the first sealing device closest to the bottom of the cavity. In other words, the axial clearance always corresponds to the shortest distance measured between the bottom of the cavity and the first sealing device.

[0033] "Threaded metal tube" refers to a tube comprising at least one end having at least one threaded portion, adapted to be assembled with another element (e.g., another threaded metal tube, closure, or support component), said other element comprising at least one end having at least one complementary threaded portion. The thread can be external or internal.

[0034] "Cavity bottom" refers to the surface of the bottom of the cavity. Therefore, when the cavity is lined and the waterproof lining is made of cement, the term "cavity bottom" refers to the surface of the cement layer at the bottom of the cavity. When the waterproof lining is not made of cement, the term "cavity bottom" refers only to the surface of the plot where the cavity is formed at the bottom of the cavity. Attached Figure Description

[0035] Further objects, features, and advantages of the invention will become apparent from the following description, which is given by way of non-limiting example only and with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the overall structure of the underground storage system; Figure 2 A schematic diagram of the retaining elements for an underground storage system; Figure 3 A schematic diagram of a retaining element of an underground storage system including a corridor according to an embodiment of the present invention; and Figure 4 This is a schematic diagram of the upper part of a storage tank included in an underground storage system according to an embodiment of the present invention. Detailed Implementation

[0036] Figure 1 A cross-sectional view of storage system 1 in reference frame (x;y) is shown. The x-axis of reference frame (x;y) is the horizontal axis, and the y-axis of reference frame (x;y) is the vertical axis corresponding to the Earth's gravity axis.

[0037] Storage system 1 includes a cavity 2 formed in plot 3, a retaining element 4 placed on the ground surface S of plot 3, a device for access from outside the cavity (2), and six storage tanks 5 suspended in the cavity 2 on the retaining element 4. Figure 1 (Only four storage tanks 5 are visible in the system). According to an embodiment, the storage system 1 includes at least one storage tank 5.

[0038] Cavity 2 has a bottom 6 and includes a waterproof lining 7. Cavity 2 can be obtained by drilling or excavation. Cavity 2 is essentially cylindrical and has an average diameter of, for example, four meters. The waterproof lining 7 is made of cement and extends vertically from the ground S to the bottom 6 of cavity 2.

[0039] like Figure 1 and Figure 2 As shown, the retaining element 4 is a circular cylindrical plate having a central body 19 and a flange 20, the flange 20 having a lower surface resting on the ground S. The central body 19 has a first thickness, and the flange has a second thickness, the first thickness being greater than the second thickness. The retaining element 4 also includes an upper surface, which is opposite to the lower surface of the flange 20.

[0040] like Figure 2 As shown, the retaining element 4 also includes six openings 8. The openings 8 are holes that pass through the first thickness and open onto the upper and lower surfaces of the central body 19 of the retaining element 4. The retaining element 4 includes at least one opening 8. Preferably, these openings 8 are cylindrical and have generatrices perpendicular to the upper and lower surfaces.

[0041] Each storage tank 5 may include multiple pipes A. Figure 1In the illustrated embodiment, the storage tank 5 includes several threaded pipes A. Therefore, the pipes A are assembled by tightening them in a manner that forms posts C to form the pipes A. These pipes A, and the resulting posts C, have a cross-section smaller than the cross-section of the opening 8 of the storage tank 5 intended to accommodate the pipes or posts C, such that the pipes A or posts C of the storage tank 5 can be inserted into or removed from the cavity 2 through the opening 8.

[0042] Therefore, the storage tank 5 is a generally tubular shape with a circular cross-section, and each storage tank has a longitudinal axis, a lower end 13 and an upper end 14.

[0043] Each storage tank 5 is closed at its lower end 13 by a first sealing device 12, and each storage tank 5 is closed at its upper end 14 by a second sealing device 15. Figure 1 In the illustrated embodiment, each tank 5 has a lower end 13 and an upper end 14 with threads, and a first sealing device 12 and a second sealing device 15 are respectively screwed onto these threads in a sealing manner. Thus, the lower end 13 is sealed by screwing onto the first sealing device 12, and the upper end 14 is sealed by screwing onto the second sealing device 15.

[0044] In other words, each tank 5 is formed of an assembly including a column C and is closed at its ends 13 and 14 by sealing devices 12 and 15. Tank 5 may also include a single pipe A and be closed at its ends 13 and 14 by sealing devices 12 and 15.

[0045] As described below, the upper end of the storage tank 5 includes a support member 17 inserted between the pipe A or column C and the second sealing device 15. This support member 17 interacts with the retaining element 4 to suspend the storage tank 5 in the cavity 2.

[0046] The access devices are designed to enable maintenance operations by allowing access to various components of the facility from the outside. These include, in particular, at least one of the following: devices for accessing each tank 5, devices for accessing the interior of each tank 5, and devices for accessing the contents of the cavity 2.

[0047] The first device for accessing the storage tank includes a channel formed on the periphery of the retaining element 4. This channel is formed, for example, around the retaining element 4 and / or on the upper surface of the flange 20. Typically, this channel allows an operator wishing to maintain the storage tank 5 located around the retaining element 4 to access the tank 5 simply by moving around the periphery of the retaining element 4. This channel around the retaining element 4 can be formed in the plot 3 surrounding the flange 20, for example, on the surface S if the retaining element 4 rests on the ground, or at the bottom of a hollow portion (not shown) formed in the plot 3 and on which the retaining element 4 rests.

[0048] If the cavity 2 contains a number of storage tanks 5, some of them are located at the center of the assembly consisting of the storage tanks 5 and therefore cannot be accessed from the channel formed around the retaining element 4. However, access is necessary for maintenance operations. Therefore, the means for accessing each storage tank 5 includes a second means for accessing the storage tank 5 in the form of a corridor 9, such as... Figure 3 As shown, the corridor 9 extends radially around the center point of the retaining element 4. Depending on certain variables or limitations of the facility, such as the number of storage tanks 5 stored in the cavity 2 and the size of the retaining element 4, one or more corridors 9 may exist to provide access to each storage tank 5.

[0049] Each tank 5 must be accessible to at least one operator; therefore, the configuration of the retaining element 4 must allow access to each tank 5. Preferably, the tanks should be as compact as possible to optimize the number of tanks 5 in the facility. To this end, the following equation defines the optimal level of compactness: [Mathematical Formula 2]

[0050] Where j is the index of each group of tanks 5 with different diameters, ODsj is the outer diameter of tank 5, and Am is the area required to access tank 5 from retaining element 4. Am is defined by considering a corridor 9 with a width between 0.6 meters and 1 meter. Tanks 5 located at the edge of retaining element 4 can be directly accessed from the outside of retaining element 4 via a temporary ad hoc passage.

[0051] exist Figure 3 In this system, the storage system 1 comprises approximately fifty tanks 5, and thus the retaining element 4 comprises approximately fifty openings 8, with each tank 5 suspended in the cavity 2 via a corresponding opening 8 in the retaining element 4. This configuration is circular and includes a maintenance corridor 9 having two rows of tanks 5 on its radially outer side and one row of seven tanks 5 on its radially inner side. Access to the outer row of tanks 5 is available from a channel formed around the periphery of the retaining element 4, and access to the inner and central rows of tanks 5 is available from the circular corridor 9 on the retaining element 4. The tanks 5 are spaced apart on at least a portion of the outer two rows to form entrances 10 to the corridor 9.

[0052] Naturally, the retaining element 4 and the cavity 2 can have various shapes, such as circular or polygonal.

[0053] The circular area of ​​retaining element 4 is defined as follows: [Mathematical Formula 3]

[0054] The polygon area of ​​retaining element 4 is defined as follows: [Mathematical Formula 4]

[0055] Where Ai is the area of ​​each triangle that makes up the area of ​​the polygon.

[0056] Naturally, the tanks 5 can be arranged on the retaining element 4 as horizontal lines, vertical lines, offset lines, lines aligned on a circle or any other geometry, and the tanks 5 can have different dimensions from each other.

[0057] like Figure 1 As shown, the tank 5 is suspended on the retaining element 4. Therefore, for each tank 5 in the storage system 1, there exists an axial clearance G between the first sealing device 12 at the lower end 13 of the closed tank 5 on one side and the bottom 6 of the cavity 2 on the other side. This axial clearance G functions to absorb the axial thermal expansion of the tank 5, which occurs particularly during filling and emptying operations. Therefore, for each tank 5, the dimension of the axial clearance G, especially its length, depends directly on the surrounding conditions of the storage system 1, particularly the temperature and pressure conditions, and the ability of the tank 5 to expand under temperature and pressure changes (especially during filling and emptying operations). Therefore, the axial clearance G of any tank 5 in the storage system 1 satisfies the following inequality: [Mathematical Formula 1]

[0058] Where: G is the axial clearance length in meters. L is the length of tank 5 in meters. β is the geothermal gradient of block 3 in degrees Celsius per meter. The geothermal gradient β varies with the geological structure of the storage system 1. Therefore, β satisfies 0.02℃ / m ≤ β ≤ 2℃ / m. α represents the coefficient of thermal expansion of the metal used to manufacture tank 5, expressed in degrees Celsius-1. The coefficient of thermal expansion α varies with the type of metal used to form the pipes of tank 5. Therefore, α satisfies 8... 10⁻⁶℃⁻¹≤α≤18 10-6℃-1.

[0059] The device for accessing the interior of each storage tank 5 includes a sacrificial auxiliary component 16. This sacrificial auxiliary component 16, support component 17, and second sealing device 15 together form the upper end 14 of the storage tank 5. The upper end 14 is as follows: Figure 4 As shown. The support member 17 includes a metal tubular body 21 with a circular cross-section having a flange 22. The outer dimension of the flange 22 is larger than the size of the opening 8, such that when the tank 5 is inserted into the opening 8, the flange 22 rests on the upper surface of the retaining element 4. Therefore, the flange 22 is adapted to suspend the tank 5 in the cavity 2 via the retaining element 4.

[0060] In embodiments where the flange 22 allows the tank 5 to rest on the upper surface of the retaining element 4, the tank 5 does not need to be attached to the retaining element 4, which simplifies the assembly of the storage system 1. However, in a variation, the flange 22 may also be attached to the retaining element 4, for example by screwing in a screw or any other suitable means.

[0061] The support member 17 is sealed at its lower end to the pipe A or column C via a threaded connection. The support member 17 is assembled at its upper end to the sacrificial auxiliary member 16, which in turn is assembled to the second sealing device 15. These assemblies are made via threaded connections including at least one seal.

[0062] Maintenance operations inside the storage tank 5 are performed via the second sealing device 15 and / or via the sacrificial auxiliary component 16. Specifically, the second sealing device 15 and / or the sacrificial auxiliary component 16 can be loosened and removed from the support component 17 to access the contents of the storage tank 5, for example, to inspect the internal condition of the storage tank 5. However, tightening / loosening during maintenance operations can damage components, which need to be replaced after several cycles.

[0063] For safety reasons, tightening / loosening of components is preferably limited to three operations. Specifically, after three tightening / loosening operations on the second sealing device 15, the seal in the second sealing device 15 can no longer reliably guarantee the sealing of the tank 5. The components that interact to form the seal must then be replaced. This is an advantageous reason for using the sacrificial auxiliary component 16 to extend the service life of the support component 17. Specifically, after three tightening / loosening operations on the second sealing device 15 on the tank 5, the second sealing device 15 and the sacrificial auxiliary component 16 are then replaced. During this replacement, tightening / loosening is performed between the sacrificial auxiliary component 16 and the support component 17. Once the sacrificial auxiliary component 16 and the sealing device 15 have been replaced, three more operations can be performed before another component replacement is required.

[0064] Therefore, the use of sacrificial auxiliary component 16 allows for up to nine operations on tank 5 without replacing support component 17. Since replacing support component 17 involves completely removing tank 5 from cavity 2, which requires manpower, time, and other additional tasks, sacrificial auxiliary component 16 improves the usability of storage system 1 and simplifies maintenance operations.

[0065] Naturally, the upper end 14 of the storage tank 5 may include more than one sacrificial auxiliary component 16, thereby further increasing the number of maintenance operations without having to remove the entire storage tank 5 from the cavity 2.

[0066] To allow inspection of tank 5, particularly its interior, the storage system 1 is designed to allow inspection of tank 5 without affecting the operation of other tanks 5. Therefore, tank 5 can be flushed, isolated, and replaced without affecting other tanks 5.

[0067] The second sealing device 15 is equipped with sensors 18, such as pressure gauges, thermometers, and leak detectors. Naturally, the first sealing device 12 may also include pressure gauges, thermometers, and leak detectors. Depending on the nature of the parameter to be checked, other types of sensors may be used.

[0068] In addition to the storage tank 5, the cavity 2 is preferably filled with a deflagration suppressant material. In the event of a leak in the storage tank 5, the presence of oxygen in the cavity 2 is limited or even eliminated, thereby reducing the risk of explosion. This deflagration suppressant material is a liquid and / or solid, such as water, sand, etc. It preferably includes antimicrobial agents, such as chlorine, antimicrobial filters, or hydrogen peroxide, as well as corrosion inhibitors to prevent bacterial growth around the storage tank 5 and deterioration of the storage tank 5.

[0069] The material must be kept in good condition to maintain its performance and prevent the storage system from deteriorating.

[0070] During maintenance operations, access to the material is required. Therefore, the device for accessing the contents of cavity 2 includes at least one suction tube and one injection tube for the material, connected to this location. Ideally, the device for accessing the contents of cavity 2 also includes a location outside cavity 2, where the suction tube and injection tube open and / or where components controlling the suction and injection tubes are located.

[0071] According to one embodiment, the injection tube is located above the material level, typically in the upper part of cavity 2, while the suction tube is located at the bottom of cavity 2. These tubes allow for pumping and injection, thereby enabling the circulation and / or replacement of material in cavity 2.

[0072] Storage system 1 is used to store any type of fluid, especially explosive gases. The fluid can be hydrogen, oxygen, methane, nitrogen, or ammonia. Hydrogen is preferred.

[0073] The present invention also proposes an underground storage method for storing fluids using the storage system 1 described above. The method includes: at least one step of forming a cavity 2 in a plot 3, the cavity 2 having a bottom 6; a step of providing a retaining element 4, the retaining element 4 including at least one opening 8 adapted to receive a support portion 17; a step of providing at least one tank 5, the tank 5 having a longitudinal axis, a lower end 13 and an upper end 14, the upper end 14 including the support portion 17; a step of providing a first sealing device 12 adapted to close the tank 5 at its lower end 13 and a second sealing device 15 adapted to close the tank 5 at its upper end 14; a step of assembling the upper end 14 to the retaining element 4 via the support portion 17 such that the tank 5 is suspended inside the cavity 2, and preferably there is an axial gap G between the first sealing device 12 of the tank 5 and the bottom 6 of the cavity 2 adapted to absorb the axial thermal expansion of the tank 5; and a step of forming a means for access from outside the cavity (2), which includes at least one of the following: a means for accessing each tank 5 from the retaining element 4, a means for accessing the interior of the tank 5 and a means for accessing the contents of the cavity 2.

Claims

1. An underground storage system (1) for fluid storage, characterized in that, It includes: A cavity (2) is formed in a plot (3) and the cavity (2) has a bottom (6); A retaining element (4) includes at least one opening (8); At least one storage tank (5) having a longitudinal axis, a lower end (13) closed by a first sealing device (12) and an upper end (14) closed by a second sealing device (15), the upper end including a support member (17), the upper end (14) being assembled to the retaining element (4) via the support member (17) such that the storage tank (5) is suspended inside the cavity (2); as well as The means for accessing from outside the cavity (2) includes at least one of the following: means for accessing each tank (5), means for accessing the interior of the tank (5), and means for accessing the contents of the cavity (2).

2. The storage system (1) according to claim 1, wherein, The device for accessing each tank (5) includes a channel formed on the periphery of the retaining element (4) and / or a corridor (9) located on the retaining element (4).

3. The storage system (1) according to any one of claims 1 and 2, wherein, The device for accessing the interior of the storage tank (5) includes a sacrificial auxiliary component (16) inserted between the second sealing device (15) and the support component (17).

4. The storage system (1) according to claim 3, wherein, The sacrificial auxiliary component (16) is removable.

5. The storage system (1) according to any one of claims 1 to 4, wherein, The device for accessing the contents of the cavity (2) includes at least one suction tube for fluids and / or solids and at least one injection tube for fluids and / or solids.

6. The storage system (1) according to any one of claims 1 to 5, wherein, The storage tank (5) includes at least one metal pipe (A) having at least one end with at least one threaded portion.

7. The storage system (1) according to any one of claims 1 to 6, wherein, The storage tank (5) includes at least two metal tubes (A) assembled by threaded connection to form a tube column (C).

8. The storage system (1) according to any one of claims 1 to 7, wherein, The first sealing device (12) and / or the second sealing device (15) are adapted to seal the storage tank (5) by means of a threaded connection.

9. The storage system (1) according to any one of claims 1 to 8, comprising a plurality of storage tanks (5).

10. An underground storage method for storing fluids using a storage system (1) according to any one of claims 1 to 9, characterized in that, It includes at least the following steps: A cavity (2) is formed in the plot (3), the cavity (2) having a bottom (6); A retaining element (4) is provided, which includes at least one opening (8) adapted to receive a support member (17); At least one storage tank (5) is provided, the storage tank (5) having a longitudinal axis, a lower end (13) and an upper end (14), the upper end (14) including a support member (17); A first sealing device (12) is provided to close the storage tank (5) at its lower end (13) and a second sealing device (15) is provided to close the storage tank (5) at its upper end (14). The upper end (14) is assembled to the retaining element (4) by means of the support member (17), so that the tank (5) is suspended inside the cavity (2); and Forming a means for access from outside the cavity (2), comprising at least one of the following: means for accessing each tank (5), means for accessing the interior of the tank (5), and means for accessing the contents of the cavity (2).

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