KR20240013073A - Sealed tank comprising a perforation device - Google Patents

Abstract

The present invention relates to a sealed tank intended to transport natural gas in liquid state and to be fitted into a floating structure, the sealed tank comprising:
- a primary sealing membrane (38) in contact with the gas,
- a secondary sealing membrane (34),
- a primary space (36) separating the secondary sealing membrane (34) from the primary sealing membrane (38),
- a piercing device (1) for piercing the primary sealing membrane (38),
The drilling device 1 is characterized in that it comprises drilling elements 44 arranged in a primary space 36 .

Description

Sealed tank comprising a perforation device {SEALED TANK COMPRISING A PERFORATION DEVICE}

The invention relates in particular to the field of tanks for gases in liquid state, for example liquid natural gas or liquefied petroleum gas, for transport by sea or river. More specifically, the present invention relates to tanks equipped with safety devices that limit the risk of damage in the event of a leak of liquid natural gas within the tank.

These tanks have a capacity of thousands of cubic meters of liquid natural gas, or even tens of thousands of cubic meters of liquid natural gas. Carriers transporting natural gas are equipped with specially fitted holds to contain these tanks, and the holds are usually divided into a number of tanks. These tanks can also be produced outside of a carrier for above-ground storage of liquid natural gas. The gas is maintained in the tank in a liquid state at -163 degrees Celsius (-163 degrees Celsius) at atmospheric pressure. Therefore, the tank must be sealed and insulated.

As shown in Figure 1, this tank 2 generally has a parallelepiped shape with a wall comprising a primary sealing membrane 10 and a secondary sealing membrane 12. The two membranes 10 and 12 are separated by a primary space 14 containing an insulating layer. The secondary space 16 between the secondary sealing membrane 12 and the walls 4, 6, 8 of the floating structure (e.g. a transport or storage carrier) is also filled with insulation. The lower wall 4 of the floating structure is the actual inner hull of the floating structure. The upper wall 8 of the floating structure has an opening for access to the internal volume of the tank.

Leakage of liquid natural gas can occur in the primary sealing membrane 10 for many reasons, for example, adverse weather conditions resulting in significant deformation of the floating structure. Then, the liquid natural gas contained in the tank 2 penetrates into the primary space 14 and enters the thermal insulation layer of the primary space 14.

To access and repair a leak in the primary sealing membrane (10), the tank (2) containing liquid natural gas must be emptied. At the end of this emptying step, a significant amount of liquid natural gas may remain in the insulating layer of the primary space 14. Since the internal volume of the tank 2 is empty, there is no longer a pressure balance between the thermal insulation layer of the primary space 14 and the internal volume of the tank 2. The weight of the liquid natural gas in the insulating layer of the primary space 14 can press the primary sealing membrane 10 against the internal volume of the tank 2, damaging the tank. Additionally, the liquid natural gas trapped in the primary space 14 vaporizes during emptying, causing the pressure in the tank walls to increase. Depending on the amount of natural gas that has seeped into the walls of the tank 2, its vaporization damages the walls of the tank 2 at least partially, in particular by deformation or local tearing of the primary sealing membrane 10.

In order to limit this deformation of the primary sealing membrane 10, a piercing device has been developed, which allows piercing the primary sealing membrane 10 in the lower wall 4 of the tank 2, which creates a primary space ( 14) By releasing the liquid natural gas that has seeped into it, it can reach the internal volume of the tank (2) very quickly. This device for completely emptying the tank 2 comprises a piercing member 22 (in this case a spike) fixed with a cable 24 to the upper part of the internal volume of the tank 2. This perforating member is a pole having an end opening into the lower part of the internal volume of the tank 2 opposite the perforated area 18 which takes the form of a stud formed on the surface of the primary sealing membrane 10. )(20). The other end of the pole 20 extends outside the tank 2. Cable 24 is partially wrapped around drum 26 containing locking means.

If a gas leak is detected in the primary sealing membrane (10), the locking means of the drum (26) is deactivated, thereby releasing the perforating member (22) punching the perforation area (18).

However, this device is expensive to install and requires precise alignment of the pole and the area to be pierced, which is difficult to achieve considering the length of the pole (1 meter to tens of meters). Moreover, several attempts are sometimes necessary to puncture the primary sealing membrane 10.

Therefore, there is a need for a drilling device to perforate the sealing membrane of a liquefied natural gas tank, which is inexpensive, easy to implement, and effective compared to the prior art.

The present invention relates to a sealed tank for liquefied natural gas comprising a perforation device which makes it possible to at least partially overcome these disadvantages.

To this end, the invention proposes a sealed tank intended to transport gases in liquid state and intended to be fitted into a floating structure, the sealed tank comprising:

- a primary sealing membrane intended to be in contact with the gas,

- a secondary sealing membrane,

- a primary space separating the secondary sealing membrane from the primary sealing membrane,

- a puncturing device for piercing the primary sealing membrane,

The drilling device is characterized in that it includes a drilling member arranged in the primary space in the resting state of the drilling device.

In other words, when the tank is in operation and sealed, the tank contains a piercing member within the primary space, even if there is no puncturing in the tank, and the puncturing device is not activated until it is necessary to pierce the primary membrane. In its resting state, the piercing member does not move in this primary space.

Therefore, by locating the perforating member in the primary space of the tank, the use of complex and expensive poles can be avoided. The device for puncturing a tank according to the invention is also more stable because the piercing elements are arranged close to the primary sealing membrane, that is, in the immediate vicinity of the wall to be pierced.

According to one embodiment, the perforation axis of the perforation element of the tank according to the invention extends intersecting the main extension plane of the primary sealing membrane located on the perforation element.

Alternatively, the piercing axis of the piercing element of the tank according to the invention extends parallel to the main plane of extension of the primary sealing membrane, and the piercing element is positioned close to the primary sealing membrane. This solution allows the perforated element to be accommodated, for example, in a small space demarcated by the corrugations of the membrane, or between two insulating panels in the primary space.

Preferably, the piercing device of the tank according to the invention comprises a propulsion device for the piercing member, the propulsion device being arranged in the primary space. This arrangement makes the drilling device compact.

Also advantageously, the puncturing device for a tank according to the invention comprises an actuating device for the piercing element, the actuating device being adapted to be installed between the secondary sealing membrane and the external enclosure of the tank. This arrangement allows the power cable to be easily connected to the operating device.

The propulsion device of the tank according to the invention is controlled by an actuating device. More specifically, the piercing device for a tank according to the invention preferably comprises a locking device for the piercing member adapted to be commanded or controlled by an actuating device.

Advantageously, the puncturing device for a tank according to the invention includes redundancy for the locking device and the actuating device. Accordingly, the drilling device comprises at least two locking devices and two actuating devices each connected to the locking devices. This serves as a safety net when controlling the tank drilling device according to the present invention and prevents the drilling device from operating due to accidental commands or electrical faults.

In one embodiment, the propulsion device, locking device and piercing member of the tank according to the invention are received at least partially in a space defined by bosses of the primary sealing membrane. These bosses may be specially provided to accommodate propulsion devices, locking devices and perforation members. Alternatively and advantageously, this boss is a corrugation formed in the metal plate of the primary sealing membrane.

Preferably, the puncturing device for a tank according to the invention comprises a return device for the piercing member. If a hole is created in the primary sealing membrane, this return device moves the puncturing member in a way that ensures that it does not block the hole created.

The tank according to the invention comprises a lower wall and a side wall, and the perforation device is arranged on the lower wall of the tank.

Also advantageously, the tank according to the invention comprises a primary insulating barrier in the primary space, the primary insulating barrier comprising a plurality of insulating casings or insulating panels, and the perforation device comprising two casings of the plurality of insulating casings. It is arranged between, or between two insulating panels, or within a casing, or inside an insulating panel. These casings or panels insulate the tank and limit the influx of heat energy.

Advantageously, the thickness of the primary sealing membrane of the tank according to the invention is between 0.5 and 2 millimeters.

Preferably, the propulsion device of the tank according to the invention is a helical spring or a leaf spring or a gas piston. The operating device of the tank according to the invention is, for example, an electromagnet or a radio signal transmitter.

Additional features and advantages of the invention will become more clearly apparent from the following description, and from the numerous exemplary embodiments presented by non-limiting representations and with reference to the accompanying schematic drawings.
Figure 1, already explained in relation to the prior art, shows a tank intended to transport liquid gas comprising a perforation device according to the prior art.
Figure 2 shows the device for drilling a tank according to the invention in a resting state according to a first embodiment of the invention.
Figure 3 shows the drilling device of Figure 2 in operation.
Figure 4 shows the device for drilling a tank according to the invention in a resting state according to a second embodiment of the invention.
Figure 5 shows the drilling device of Figure 4 in operation.
Figure 6 shows the perforation device for a tank according to the invention in a resting state according to a third embodiment of the invention.
Figure 7 shows the drilling device of Figure 6 in operation.

According to one embodiment of the present invention, a sealed tank according to the present invention for transporting gas in liquid state or storing this gas in liquid state above ground has an internal volume of several thousand cubic meters of gas, and is provided in the tank of FIG. As shown, it includes two sealing layers and two insulating layers. The tank thus comprises, from the inside of the tank to the outside, a primary sealing membrane (38), a primary space (36) comprising insulation, a secondary sealing membrane (34) and a secondary space (32) comprising insulation; , this secondary space 32 includes walls forming the external enclosure of the tank.

The sealed tank according to the invention has a generally parallelepiped shape and includes a lower wall (shown in Figure 2), side walls and an upper wall provided with an opening, which wall fits inside the floating structure.

In a first embodiment of the invention, the lower wall 5 of the tank is located on the inner hull 30 of a floating structure, for example a carrier for transport and/or storage. In other variations, the tank has a shape other than a parallelepiped (eg, spherical).

In a first embodiment of the invention, the drilling device 1 according to the invention is arranged on the lower wall 5 of the tank, as shown in FIG. 2 . As a variant, the perforation device 1 according to the invention is arranged on the side wall of the tank, but relatively close to the bottom wall 5 for efficient emptying of the tank.

The lower wall 5 of the tank according to the invention comprises a primary sealing membrane 38 which, when the tank is full, comes into contact with the liquefied gas and directly demarcates the tank interior. This primary sealing membrane 38 is made of, for example, an iron alloy, or stainless steel, or an alloy containing nickel or manganese, or aluminum, and has a thickness of 0.5 to 2 millimeters, for example a thickness of 0.7. to 1.2 millimeters.

The lower wall 5 of the tank according to the invention can also be made of a metal alloy containing nickel and/or manganese, for example on the basis of iron, with a thickness of 0.5 to 2 millimeters, for example 0.7 millimeters. , a secondary sealing membrane 34 made of stainless steel or a composite material with overlapping synthetic and aluminum layers. The secondary sealing membrane 34 is separated from the primary sealing membrane 38 by a primary space 36 .

The primary space 36 is filled with a plurality of insulating casings filled with an insulating material, for example glass wool or perlite. The primary space 36 can also be occupied by an insulating panel, for example made of polyurethane foam, preferably reinforced with glass fibres.

In the remainder of the description, the term "casing" is used to designate the insulating element, but note that the term "casing" may be replaced by the term "panel".

The secondary sealing membrane 34 is separated by a secondary space 32 from the inner hull 30 of the floating structure itself containing a tank, and also consists of a casing filled with insulation, or is made of insulation (e.g. , glass wool, perlite or polyurethane foam). This casing or panel is securely fastened to the inner hull 30 by adhesive studs 31 and/or mechanical anchoring (e.g. metal pins).

The distance between secondary sealing membrane 34 and primary sealing membrane 38 is between 20 and 250 millimeters (eg, 25, 100 or 230 millimeters).

The distance between the secondary sealing membrane 34 and the inner hull 30 is between 130 and 400 millimeters, for example 130, 230, 300 or 380 millimeters. Naturally, one can expect primary or secondary spaces to be larger or smaller in thickness. The distance between the two insulating casings is approximately 50 millimeters measured in the main extension plane of the respective sealing membranes.

2 and 3 , the drilling device 1 according to the invention is arranged along the drilling axis X orthogonal to the lower wall 5 of the tank and thus to the inner hull. It comprises perforation elements 44, for example metal spikes, arranged in the primary and secondary sealing membranes 38, 34 arranged at 30. As a variant, the perforation axis

In the resting state of the drilling device 1 according to the invention, that is, when not in use, the drilling element 44 is moved by the locking device 40 (in this case a yoke) to the propulsion device 42 (in this case a yoke). , compression is maintained in the helical spring). For this purpose, the locking device 40 comprises an elbow rotatably mounted on the secondary sealing membrane 34 or casing, from which an arm 405 is arranged parallel to the perforation member 44. ), and the arm 405 ends with a rod 403 that crosses the arm 405. The rod 403 is locked in the corresponding opening 443 (shown in FIG. 3 ) of the piercing member 44, thereby preventing propulsion of the piercing member 44 by the propulsion device 42. The locking device 40 also includes an arm 401 extending from the elbow in a slightly inclined direction with respect to the lower wall 5 (or the secondary sealing membrane 34 of this lower wall 5).

Since the locking device 40 is rotatable about a rod rigidly fixed to the secondary sealing membrane 34 or the casing, when the arm 401 is rotated towards the secondary sealing membrane 34, the opening 443 With the rod 403 released, the propulsion device 42 propels the piercing member 44 towards the primary sealing membrane 38 to effect the same puncture, as shown in FIG. 3 .

This rotation of the arm 401 is commanded by an actuating device 46 (in this case an electromagnet) which, when the electromagnet is energized, moves the arm 401 horizontally, i.e. against the lower wall 5. pulled in a direction parallel to The actuating device 46 is inserted into the insulating barrier of the secondary space 32 , for example between two insulating casings of the secondary space 32 or directly into the insulating material of one of these casings. A power cable 48 connected to the electromagnet passes through part of the secondary space 32 to a system (e.g. a switch) for powering and controlling the drilling device 1. As a variant, the electromagnets are commanded wirelessly if the primary and secondary sealing membranes 34 and 38 are made of a material that allows radio waves to be transmitted.

The propulsion device 42, the piercing member 44 and the locking device 40 are preferably accommodated between two insulating casings of the primary space 36, Since the distance is about 50 millimeters, this arrangement is acceptable.

According to a second embodiment of the present invention, the sealed tank according to the present invention, as shown in Figures 4 and 5, except for the perforation device 1, where the propulsion device is a leaf spring rather than a helical spring. It is the same as the tank of the first embodiment of the invention. Elements that are the same as in the first embodiment of the present invention will not be described again below.

In a second embodiment of the invention, the piercing device 1 for a tank according to the invention also comprises, like the first embodiment of the invention, a piercing member 44 arranged in the primary space 36, a propulsion device ( 50) and a locking device 40 and an actuating device 46 arranged in the secondary space 32. In particular, the locking device 40 is the same yoke as in the first embodiment of the present invention, and the piercing member 44 is held in a resting state by a rod 403 inserted into the opening 443 of the puncturing member 44, It locks in the direction perpendicular to the lower wall (5). Therefore, the operation of the locking device 40 is the same as that of the first embodiment of the present invention.

In a second embodiment of the invention, the propulsion device 50 is a leaf spring comprising a fixed arm 501 rigidly fixed to a secondary sealing membrane 34 or casing. The leaf spring also includes a propulsion arm 502, the end of which is mounted in tension against the edge 441 of the piercing member 44 in the resting state of the piercing device 1.

When the actuating device 46 (in this case an electromagnet) is energized, the arm 401 of the locking device 40 is pulled towards the secondary sealing membrane 34 and away from the opening 443 of the piercing member 44. Load 403 is released. The piercing member 44 is then propelled against the primary seal membrane 38 by the propulsion arm 502 of the propulsion device 50 to create a hole in the primary seal membrane 38 as shown in FIG. 5 . forms.

According to the third embodiment of the invention shown in Figures 6 and 7, the sealed tank according to the invention has the same features as the above-described embodiment, the only difference being the primary sealing membrane 38 and the secondary sealing. The primary space 36 between the membranes 34 is much smaller, and therefore the puncturing device 1 of the tank according to the invention provides a boss of the primary sealing membrane 38, as shown in FIGS. 6 and 7 381) is arranged differently. Therefore, elements that are identical to the preceding embodiments of the present invention will not be described again in this case.

In a third embodiment of the invention, the primary space 36 is defined by an insulating layer with a thickness of 20 to 100 millimeters, the insulating material being, for example, plywood or a polymer composite or polyurethane foam sheet.

The boss 381 in which the drilling device 1 is accommodated takes the form of a corrugated section with a length (L) of about 1 meter and a height (H) of about 70 millimeters. As a variant, the height of the wave-shaped portion is different but has a value of 30 millimeters to 100 millimeters. The undulations 381 also extend transversely over several centimeters (eg, 50 millimeters), with their transverse dimensions being orthogonal to the cross-sectional plane of FIG. 6 . As a variant, the corrugated portion extends over a greater distance in this orthogonal dimension. In an embodiment of the invention, the corrugated portion 381 is specially designed to accommodate the drilling device 1. As a variant, the corrugation 381 is a corrugation formed by the primary sealing membrane 38, especially to absorb deformation of the tank caused by temperature fluctuations.

In a third embodiment of the invention, the drilling device 1 according to the invention comprises a drilling member 60 (in this case a rod ending in a spike), the drilling axis X of which extends to the lower wall of the tank ( 5) parallel to the main extension plane of the secondary sealing membrane 34. Accordingly, the perforation axis

The rod constituting the perforated member 60 is rigidly fixed to the secondary sealing membrane 34 or the casing or panel of the primary space 36. A plurality of guide bearings, for example, four guide bearings 62, 64 , 65 and 66) can be translated. 6 and 7 the bearings 62, 64, 65 and 66 are fixed to an insulating sheet in the primary space 36, which is for example a sheet of plywood or polymer composite or polyurethane foam. The propulsion device 69 is mounted compressed around a rod between a guide bearing 65 and a ring 603 rigidly fixed to the drilling member 60, for example in the resting state of the drilling device 1. It is a spiral spring. The distance between the ring 603 and the spike of the rod is greater than the distance between the side wall 382 and the surface of the guide bearing 66 close to the side wall 382. Accordingly, when the spring constituting the propulsion device 69 is relaxed, the ring 603 translates toward the bearing 66 and the spike of the rod is propelled against the side wall 382 as shown in FIG. The same perforation is made.

Once the primary sealing membrane 38 has been perforated, a return device 68, e.g. , a helical spring mounted on the rod constituting the piercing member 60 brings the spike of the rod completely back into the space at least partially defined by the corrugated portion 381. For this purpose, a spring 68 for returning the spikes is arranged between the collar 601 at the spike-free end of the rod and the guide bearing 62 close to the spike-free end of the rod. The path along which the spring 68 moves is about half that of the spring 69 in a way that does not impede the propulsion of the perforating member 60.

To keep the drilling device 1 at rest, two locking devices 70 and 72 hold the drilling member 60 inside the corrugation 381 against the wall 382. These locking devices 70 and 72 are each a yoke with an elbow rotatably mounted on a protruding element of the secondary sealing membrane 34, which element is rigidly fixed to the secondary sealing membrane 34, not shown. there is.

The yoke constituting the first locking device 70 includes two arms 705 and 701 extending from the elbows of the yoke parallel to the rod constituting the perforation member 60 . The arm 705 includes at its end a stud 703 that is received in the opening 605 of the drilling member 60, when the drilling device 1 is at rest. Accordingly, the first locking device 70 prevents this rod from sliding in the guide bearings 62, 64, 65 and 66.

Likewise, the yoke constituting the second locking device 72 includes two arms 725 and 721 extending from the elbows of the yoke parallel to the rod constituting the perforation member 60. The arm 725 includes at its end a stud 723 that is received in the opening 607 of the drilling member 60 in the resting state of the drilling device 1 . Accordingly, the second locking device 72 prevents this rod from sliding between the guide bearings 62, 64, 65 and 66.

Since the elbow of the first locking device 70 is rotatable about an element rigidly fixed to the second sealing membrane 34, when the arm 701 rotates towards the second sealing membrane 34, the stud ( 703 is released from the opening 605 . Likewise, when the arm 721 of the second locking device 72 rotates towards the second sealing membrane 34, the stud 723 is released from the opening 607. These two rotations release the piercing member 60, allowing the propulsion device 69 to push the piercing member 60 towards the wall 382 of the boss 381.

This rotational movement of the arms 701 and 721 is commanded respectively by a first actuating device 80 and a second actuating device 84 (in this case an electromagnet) which, when energized, rotates. Arms 701 and 721 are pulled towards second sealing membrane 34. The actuating devices 80 and 84 are arranged within the insulating barrier of the secondary space 32, for example between two insulating casings of this secondary space 32 or directly in one of these casings. Power cables 82 and 86, respectively connected to the first actuating device 80 and the second actuating device 84, are connected to a secondary power supply to a system (e.g. a switch) for powering and controlling the drilling device 1. It penetrates part of the space 32. As a variant, the electromagnet issues commands wirelessly if the primary and secondary sealing membranes 34 and 38 are made of a material that allows radio waves to be transmitted.

The locking devices 70 and 72, the propulsion device 69 and the piercing member 60 are for the part arranged in the corrugation 381 of the primary sealing membrane 38.

In a third embodiment of the invention the redundancy of the locking devices 70, 72 and the corresponding actuating devices 80, 84 acts as a safety net for the drilling device 1 in the resting state. Specifically, if one of the yokes 70 and 72 is actuated accidentally, no perforation occurs in the wall 382 because the other yoke still holds the perforation member 60 inside the corrugation 381.

Clearly, the invention is not limited to the embodiment just described, and many adjustments may be made to this example without departing from the scope of the invention.

Claims (14)

A sealed tank configured to transport gas in a liquid state and fitted into a floating structure, comprising:
- a primary sealing membrane (38) adapted to contact said gas,
- a secondary sealing membrane (34),
- a primary space (36) separating the secondary sealing membrane (34) from the primary sealing membrane (38),
- said sealed tank comprising a piercing device (1) for piercing said primary sealing membrane (38),
The drilling device (1) is characterized in that it comprises drilling members (44, 60) arranged in the primary space (36) in the resting state of the drilling device (1).
Sealed tank. According to claim 1,
Characterized in that the piercing axis (
Sealed tank. According to claim 1,
Characterized in that the piercing axis (
Sealed tank. The method according to any one of claims 1 to 3,
The drilling device (1) comprises a propulsion device (42, 50, 69) for the drilling member (44, 60), the propulsion device (42, 50, 69) arranged in the primary space (36). characterized by being
Sealed tank. The method according to any one of claims 1 to 4,
The puncturing device (1) comprises an actuating device (46, 80, 84) for the puncturing member (44, 60), the actuating device (46, 80, 84) being used for the secondary sealing membrane (34). Characterized in that it is configured to be installed between the external enclosure of the tank.
Sealed tank. The method of claim 4 or 5,
Characterized in that the propulsion device (42, 50, 69) is controlled by an operating device (46, 80, 84)
Sealed tank. The method of claim 5 or 6,
Characterized in that the drilling device (1) comprises a locking device (40, 70, 72) for the drilling element (44, 60) configured to be commanded by the operating device (46, 80, 84).
Sealed tank. According to claim 7,
Characterized in that the drilling device (1) comprises redundancy for the locking device (70, 72) and the actuating device (80, 84).
Sealed tank. The method of claim 7 or 8 in addition to claims 3 and 4,
Characterized in that the propulsion device (69), the locking device (70, 72) and the piercing member (60) are at least partially received in the space defined by the boss (381) of the primary sealing membrane (38). doing
Sealed tank. The method according to any one of claims 1 to 9,
Characterized in that the drilling device (1) comprises a return device (68) for the drilling member (60).
Sealed tank. The method according to any one of claims 1 to 10,
Characterized in that the tank comprises a lower wall (5) and a side wall, and the perforation device (1) is arranged on the lower wall (5) of the tank.
Sealed tank. The method according to any one of claims 1 to 11,
The tank includes a primary insulating barrier in the primary space 36, the primary insulating barrier includes a plurality of insulating casings, and the perforation device 1 is positioned between two of the plurality of insulating casings. Characterized by being arranged in the space of
Sealed tank. The method according to any one of claims 4 to 13,
The propulsion device (42, 50, 69) is a helical spring (42, 69) or a leaf spring (50) or a gas piston.
Sealed tank. The method according to any one of claims 5 to 14,
Characterized in that the operating device (46, 80, 84) is an electromagnet or a wireless signal transmitter.
Sealed tank.