Device for reducing hydrodynamic loads from splashing liquid cargo in membrane tank of gas carrier vessel (embodiments)

Abstract

FIELD: transport shipbuilding.SUBSTANCE: invention relates to devices for cargo membrane tanks of gas carriers intended for transporting gas in a liquid state, in particular liquefied natural gas (LNG). At least three embodiments of soft-shell bulkhead designs are proposed, each of which performs the same task, namely: reducing the impact of hydrodynamic loads when liquid cargo splashes onto the membrane, heat-insulating layers and hull structures of the gas carrier vessel tank when it is partially filled during the transportation of liquid cargo, protecting them from destruction, maintaining the liquefied gas in a relatively stable position, even during extreme pitching, thereby improving the stability of the membrane cargo tank during transportation. In the first embodiment, the device is presented in the form of a vertical longitudinal perforated bulkhead, in the second a vertical transverse mesh bulkhead, in the third a vertical cross-shaped bulkhead (perforated or mesh). All bulkheads are permanently installed inside the tank of the gas carrier vessel along its entire height and are secured with the help of embedded foundations and reinforcements at the corners and at several points along its entire length from above to the deck ceiling of the tank, and from below to the bottom ceiling.EFFECT: improved design.6 cl, 3 dwg

Description

[0001] The invention relates to the field of transport shipbuilding, namely to devices for cargo membrane tanks of gas carriers intended for transporting gas in a liquid state, in particular liquefied natural gas (LNG).

[0002] LNG carrier membrane tanks have the highest utilisation rate by deadweight, accounting for over 90% of all orders. However, they are vulnerable to intense free-surface liquid vibrations that occur in partially filled tanks during rolling. These surface vibrations generate waves that strike the tank walls, causing dynamic loads and potentially damaging or destroying the membrane and thermal insulation. Random movements of liquid cargo in LNG carrier tanks (sloshing or sloshing) manifest themselves in two main effects: general and local. The general effect is the impact of the large mass of liquid moving within the tank on the hull structures during rolling, while the local effect is characterized by localized impacts of the liquid on the tank walls.The distinction between general and local effects is arbitrary; both effects occur simultaneously, although they differ significantly in the period of their impact (the general effect occurs with a frequency comparable to the period of the vessel's natural oscillations during rolling—approximately 10 s, while the local effect occurs with a frequency of 0.01–0.001 s), as well as in the area of ​​impact (in the case of a general effect, this affects virtually the entire surface of the vessel, while in a local effect, it affects only localized areas of the vessel). The causes of loads from the general movement of liquid cargo and local impact impact, in addition to all types of rolling caused by stormy navigation in rough seas, also include abrupt maneuvers of the vessel and collisions.

[0003] The consequences of liquid cargo splashing are a serious problem for gas carriers with membrane tanks, namely:

[0004] - damage to tank structures (unacceptable deformations and rupture of membranes of the first and even second barriers, damage and destruction of thermal insulation and its fasteners), which creates a risk of depressurization of the tank and leakage of LNG, cooling of the hull structure to a brittle state;

[0005] - a change in the inertial characteristics of the vessel, which, when on unfavorable courses to the wave, can cause resonance of the rolling motion and increase the impact of splashing liquid cargo in the tank;

[0006] - a decrease in the stability of the vessel due to regularly shifting liquid cargo with a free surface, which negatively affects the amplitude of the roll and may impair the controllability of the vessel;

[0007] - gas leak during depressurization of the cargo tank as a result of destruction of the membranes of the first and second barriers, which creates a risk of poisoning of crew members, fire and explosion of gas;

[0008] - limitation of the logistical capabilities of using a gas carrier for the transportation of non-batch cargo - partial emptying of cargo tanks in intermediate unloading ports;

[0009] - increased dynamic loads on the body structures of tanks and their membranes with thermal insulation, causing fatigue stresses and deformations, accelerating their wear and reducing service life.

[0010] Limitations on the filling level of membrane tanks (filling at a level of 10 to 70% is not permitted) are reflected in the Rules of the Russian Maritime Register of Shipping and other classification societies.

[0011] This problem remains a pressing issue in the shipbuilding industry today. Various technical solutions are being developed, and modern vessels are being designed with this phenomenon in mind. In particular, the Rules for the Classification and Construction of Sea-Going Vessels of the Russian Maritime Register of Shipping require the mandatory design of the cargo membrane tank with lower and upper inclined sections on the second side. This reduces the load on the membrane and thermal insulation from sloshing when filled to 10% and over 70%. However, this problem cannot yet be completely eliminated, especially in stormy conditions.

[0012] A known design of a membrane tank for transporting LNG is provided, with a double thermal insulation shell made of corrugated cryogenic steel or sheet Invar. To maintain the tank's shape and reduce sloshing during vessel operation, the tank is equipped with permanent scaffolding made of cryogenic metal, on which horizontal and vertical cryogenic metal plates are located. The connections between the scaffolding legs and the connection of the legs to the inner shell ensure freedom of thermal deformation in any direction (Russian Federation Patent Application No. 2012135717, published February 27, 2014, Bulletin No. 6).

[0013] A tank is known, having a square shape with a bottom, a front, rear, side walls and a top plate, provided on the inside with bulkheads that extend across the width of the tank, forming spacious spaces, and a reduced axial part facing the inside between the top plate and the side wall, extending upward. Elements that prevent lateral movement are installed between the front wall of the tank and one bulkhead of the vehicle and between the rear wall and the other bulkhead (KR 100305513, IPC B63B 25 / 16, E17C 3 / 02, published 22.11.2001).

[0014] A tank for transporting and storing LNG is known, containing a thermal insulation shell made of hollow aluminum panels, and connected to it inside the tank by a bulkhead with lining and a set of loops, which ensure the strength of the structure and reduce the load on the tank during sloshing (RU Patent No. 2727768, IPC B63B 25 / 16, B63B 73 / 10, published July 23, 2020, Bulletin No. 21).

[0015] The disadvantages of these inventions are as follows:

[0016] - the problem of liquid cargo splashing is being addressed by increasing the strength of the insulating layers of the cargo tank itself, installing reinforced metal structures on the second bottom, on the lower and upper inclined sections and on the vertical sections of the second side, on the inner deck and on the transverse bulkheads, which reduces the space directly for placing liquid cargo;

[0017] - the arrangement of metal structures inside the tank leads to the need to reinforce them with a longitudinal bulkhead, which further reduces the deadweight utilization coefficient, i.e., it actually neutralizes the advantages that membrane tanks have;

[0018] - the structures of the internal metal bulkheads have reinforcements at the points where they connect to the double bottom and the deck covering, which also makes the hull structure heavier; they provide strength to the heat-insulating barriers, but are not intended directly to dampen LNG splashing, which leads to dynamic loads;

[0019] - intensive splashing of liquefied gas in the membrane tank contributes to an increase in the intensity of its evaporation and, accordingly, an increase in the costs of operating systems for the extraction of evaporated gas;

[0020] - installation of metal structures on the sides, bottom, deck and transverse bulkheads increases the labor intensity of their installation;

[0021] - extreme dynamic loads in a partially filled tank from splashing liquid cargo, capable of damaging or destroying thermal insulation and longitudinal bulkheads, significantly complicate their repair.

[0022] The closest approach to the claimed solution and the achievable result is a pneumatic panel—a soft-shell structure installed in a membrane-type compartment of a gas carrier and consisting of two panels connected by tie rods. The pneumatic panel is flat and hinged along the contour of its junction with the compartment walls. The hinged support on the bulkheads is movable, while on the sides it is fixed. Air or gas, filling the space between the panels, which is sealed at the ends, under excess pressure, imparts rigidity and a certain load-bearing capacity to the pneumatic panel. When unfilled, the pneumatic panel occupies a minimal volume and behaves like a soft membrane (Tolmachev K.S., Ogay A.S., Ogay S.A., “Ways to solve the problem of sloshing in membrane-type tanks using soft-shell structures,” Magazine “Youth. Science. Innovation,” Vladivostok, Moscow State University named after Adm. G.I. Nevelskoy, Volume 1, 2023, pp. 131-136).

[0023] A drawback of the prototype is the need to equip the pneumatic panel with a device for securing it along its contour at a specific level in the tank, i.e., at the free surface of the liquid cargo. Moreover, this level is always variable, as it corresponds to the liquid cargo level in the tank. The necessary fastenings could, for example, be a system of cables with winches on the tank bottom, combined with guides on the side deck, which would significantly complicate the design and reduce its reliability. Furthermore, filling the pneumatic panel with air or gas under excess pressure requires a separate filling and pressure maintenance system, which also makes the device more expensive and requires additional maintenance.

[0024] Thus, liquid cargo splashing is a serious threat to the safety of liquid cargo transportation, which also limits the logistical capabilities of gas carriers, and requires the development of new measures to minimize risks.

[0025] The objective of the claimed invention is to create a device in the membrane tank of a gas carrier vessel that makes it possible to reduce the impact of hydrodynamic loads when liquid cargo splashes on the membrane and thermal insulation of the membrane tank of the gas carrier vessel when it is partially filled during the transportation of liquid cargo, in particular liquefied natural gas (LNG).

[0026] The technical result is achieved due to the fact that, thanks to the additional bulkhead made of soft shells built into the membrane tank, it becomes possible to reduce both general (piling on a large mass of liquid) and local (liquid impacts) hydrodynamic effects on the membranes, heat-insulating layers and hull structures of the gas carrier vessel tank, which allows protecting them from destruction, as well as maintaining liquefied gas in a relatively stable position, even during extreme pitching, and thereby improving the stability of the membrane cargo tank during transportation, while maintaining a high volume utilization ratio, characteristic of membrane-type tanks.

[0027] At least three soft-shell bulkhead design options are proposed, each of which performs the same task and is equivalent to the others. All bulkheads are permanently installed within the tank.

[0028] The stated objective is achieved by the first embodiment, which consists of a vertical bulkhead located within the membrane tank of a gas carrier vessel. The bulkhead is made of a soft, single-layer, cryogenic-resistant material, perforated over its entire surface, and installed lengthwise along the vessel's centerline across the entire height of the tank, from one hull transverse bulkhead to the other. The bulkhead is secured at the corners and at several points along its entire length by embedded foundations and reinforcements, at the top to the tank's deck ceiling, and at the bottom to the tank's bottom ceiling. The lateral edges of the bulkhead are freely adjacent to the forward and aft hull transverse bulkheads of the tank, but are not secured to them. The tank may have one bulkhead installed in the centerline, or two or more installed parallel to each other.

[0029] The stated objective is achieved by the second embodiment, which features a vertical bulkhead located within the membrane tank of a gas carrier vessel. This bulkhead is made of a fine-mesh, cryogenic-resistant mesh material and is installed transversely across the vessel's entire height from one side deck to the other. The bulkhead is secured at the corners and at several points using embedded foundations and reinforcements along its upper edge to the tank's deck ceiling and the inclined section of the inner deck, and along its lower edge to the tank's bottom ceiling and the inclined section of the tank's side ceiling. The bulkhead's lateral edges are freely adjacent to the tank's vertical side ceilings, but are not secured to them. A tank may contain one or more bulkheads, installed parallel to one another.

[0030] The set task is achieved by the fact that in the third variant, a cross-shaped bulkhead is installed inside the membrane tank of the gas carrier vessel, made in the form of two perforated sheets of soft single-layer cryogenic-resistant material, located perpendicular to each other along the entire height of the tank from one hull transverse bulkhead to the other and from side to side, the longitudinally oriented sheet is continuous, the transverse sheet has a gap at the place of contact with the continuous sheet, the bulkhead is fixed at the corners and at several points with the help of embedded foundations and reinforcements along the upper edge to the ceiling of the deck covering of the tank and the inclined section of the inner deck, and along the lower edge - to the bottom covering of the tank and the inclined section of the side covering of the tank, the side edges of the sheets freely adjoin the hull transverse front, rear bulkheads and the vertical side coverings of the tank, but are not fixed to them.The canvases can be made of fine mesh material.

[0031] Unlike a rigid bulkhead, a soft bulkhead is flexible, does not experience bending stresses that create additional stress at the attachment points to the tank body during deformation, and also has less weight, which reduces additional loads on the body and effectively dampens sharp fluctuations of the liquid cargo.

[0032] All bulkhead options can be made of soft, high-strength, high-modulus Kevlar-type material with a high modulus of elasticity, for example, grade K49, which maintains and even increases its strength at cryogenic temperatures, have a cryogenic gas-waterproof coating made of elastomers, or be uncoated.

[0033] The claimed device is suitable for all designs of membrane tanks of gas carriers.

[0034] During stormy voyages, gas carriers experience pitching and rolling, which causes fluid movement within their cargo tanks. For larger vessels, such as gas carriers, the amplitude of pitching and rolling is typically greater than that of pitching, as the liquid in the tank moves in large masses from side to side with periodic changes in speed and acceleration, both in magnitude and sign. Therefore, the greatest dynamic loads from the sloshing of liquid cargo are experienced by the tank's side walls, membranes, and thermal insulation on the sides. Impact loads from waves reach their maximum value in a partially filled tank, corresponding to 50% of its capacity. Dangerous impact loads occur in a tank filled from 10 to 70% of its full capacity. The movement of the entire mass of liquid when the LNG carrier tilts onto its side during rolling also creates additional stress on the side deck, the primary barrier membrane and the thermal insulation.The effect of installing soft-shell bulkheads in a membrane tank is a significant reduction in dynamic loads from the splashing of liquid cargo on the membranes of the primary and secondary barriers and thermal insulation, which are not designed to withstand large dynamic loads.

[0035] The main mechanisms for reducing dynamic loads on membranes and thermal insulation from splashing of liquid cargo in a tank with soft-shell longitudinal bulkheads during rolling:

[0036] - dividing the volume by one or more longitudinal bulkheads limits the movement of the liquid mass, thereby reducing the overall effect of the movement of liquid cargo in the tanks of gas carriers - the impact on the hull structures of a large mass of liquid moving in the tank during rolling, since part of the load is borne by the bulkhead, and the effect of reducing the load increases with the installation of two or more longitudinal bulkheads;

[0037] - reducing the area of ​​the free surface limited by the sides and bulkhead reduces the amplitude of the resulting wave, thereby weakening the local effect of local impacts of the liquid on the walls of the tank;

[0038] - the movement of liquid cargo leads to periodic deformations of the flexible soft-shell bulkhead and creates a damping effect - the absorption of part of the kinetic energy of the moving liquid, which occurs with each amplitude movement on board and, ultimately, reduces the dynamic impact on the membranes, thermal insulation and hull structures;

[0039] - soft-shell bulkheads separating the liquid mass in the cargo tanks of a gas carrier vessel change its amplitude-frequency characteristics, which will also have a positive effect on reducing the impact of moving liquid on membranes, thermal insulation and side ceilings.

[0040] The listed mechanisms for reducing dynamic loads on membranes and thermal insulation from splashing of liquid cargo in a tank with longitudinal soft-shell bulkheads during rolling are similar to those during pitching, when transverse soft-shell bulkheads operate.

[0041] Installing longitudinal and transverse soft-shell bulkheads in a membrane cargo tank, as in option 3, provides additional positive effects:

[0042] - soft-shell bulkheads transfer the load through the embedded foundations to the deck and bottom floors, which are not directly exposed to the moving liquid, thereby distributing the dynamic load from splashing between all the floors that form the cargo capacity and, consequently, reducing it on the side floors;

[0043] - a free surface, separated by soft-shell bulkheads, limits the movement of large masses of liquid cargo and the amplitude parameters of the resulting splash wave, which in turn reduces evaporation from the surface of liquefied natural or other gas (the amount of boil-off gas), ultimately reducing the load on the system for its utilization.

[0044] Variants of bulkhead design are shown in figures 1-3.

[0045] Figure 1 shows a general view of the first version of the bulkhead device.

[0046] Figure 2 shows a general view of the second version of the bulkhead device.

[0047] Figure 3 shows a general view of the third version of the bulkhead device.

[0048] The claimed invention is explained using the example of devices made in three design variants.

[0049] The device according to the first variant (Fig. 1) is located inside the cargo tank 1 and is at least one vertical single-layer soft-shell bulkhead 2 in the form of a solid sheet with perforation 3, which is installed along the tank 1 along its entire height from the forward hull transverse bulkhead 4 to the rear hull transverse bulkhead 5. The bulkhead 2 is secured with the help of embedded foundations and reinforcements 6 at the corners of the sheet and at several points along its entire length from above to the overhead of the deck covering of the tank 7, and from below - to the bottom covering of the tank 8. The side edges 9 of the bulkhead 2 freely adjoin the hull transverse bulkheads 4 and 5 and are not secured to them.

[0050] The technical result achieved using the first embodiment of the device is achieved as follows.

[0051] During roll, the soft-shell longitudinal bulkhead 2 at least halves the mass of liquid cargo exerted on the side deck during heeling, as the bulkhead itself supports the remaining portion of the liquid mass. On the free surfaces of the liquid cargo, reduced by the separating longitudinal soft-shell bulkhead, destructive waves of a fractionally smaller size form; therefore, the impact loads from them will also be significantly lower. The energy from the movement of the liquid cargo in the tank, which at different stages of the ship's periodic heeling, changes from potential to kinetic and vice versa, is partially absorbed by the deformation of soft-shell bulkhead 2 and the flow of some of the liquid cargo through the perforations of bulkhead 3, which also reduces the dynamic loads on the side decks with the membrane and thermal insulation.Bulkhead 2, free from fastening along the lateral edges 9 of the abutment to the transverse hull bulkheads 4 and 5 of tank 1, but fastened along the upper and lower edges by means of embedded foundations and reinforcements 6, experiences a uniaxial stress-strain state, excluding shear deformations, which has a favorable effect on the durability of the soft-shell material, and the gaps between the lateral edges 9 and the hull transverse bulkheads 4 and 5, as well as the perforation 3, make it possible to equalize the amount of liquid cargo on different sides of the soft-shell bulkhead by means of overflow, preventing asymmetry in the amount of liquid cargo on different sides of bulkhead 2.Shock loads from waves on the free surfaces of the liquid cargo, which Bulkhead 2 is subjected to during rolling, pose no danger to it. Due to the softness of the bulkhead material (the absence of bending stresses), the stresses (forces) within it are instantly redistributed across its entire surface, and the resulting forces are matched by the selected strength of the material and the embedded elements by which it is attached to the LNG carrier's hull structures. Furthermore, when transporting LNG, which has a temperature of -162°C, Bulkhead 2 reduces gas evaporation by reducing its rough surface area.

[0052] The device according to the second variant (Fig. 2) is located inside the cargo tank 1 and is at least one vertical single-layer mesh bulkhead 10 with a fine mesh, which is installed across the tank 1 along its entire height from the starboard side floor 11 to the port side floor 12. The bulkhead 10 is secured with the help of embedded foundations and reinforcements 13 at the corners and at several points from above to the ceiling of the deck floor of the tank 7 and the inclined section of the inner deck 14, and from below to the bottom floor of the tank 8 and the inclined section of the side floor 15 of the tank 1. The side edges 16 of the bulkhead 10 freely adjoin the side floors 11 and 12 and are not secured to them.

[0053] The technical result achieved using the second version of the device is achieved as follows.

[0054] Mesh transverse bulkhead 10 operates similarly to longitudinal bulkhead 2, shown in the first embodiment. During roll, mesh transverse bulkhead 10 also significantly reduces the dynamic destructive effect of moving liquid cargo with a rough free surface on the decks, membranes, and thermal insulation, allowing it to retain the liquid cargo flowing through the mesh mesh at certain flow rates. At low speeds and a relatively large mesh size, the mesh will be virtually permeable to the flow, while at high speeds and a relatively small mesh size and rope thickness, it will be similar to perforated bulkhead 2, i.e., it will have the required permeability. During slow inclinations of the gas carrier, the liquid cargo partially flows through the mesh bulkhead mesh, without creating additional trim.Reducing wave formation on the free surface separated by a mesh bulkhead will reduce the amount of boil-off gas. Liquid flow through the mesh will reduce the static and dynamic loads on the mesh bulkhead ropes. For a gas carrier of certain dimensions and characteristics, the roll and moving liquid cargo parameters are accurately calculated and remain within a relatively narrow range of variation. Therefore, it is possible to select an effective mesh size and rope thickness that ensure the required minimum mesh bulkhead permeability 10, at which the separated volume of liquid cargo will significantly reduce the dynamic destructive effect of the moving liquid cargo on the hull bulkheads, membranes, and thermal insulation.

[0055] The mesh transverse bulkhead 10, in contrast to the longitudinal bulkhead 2, has a lower weight and is easier to manufacture, install and repair.

[0056] The device according to the third variant (Fig. 3) is installed inside the cargo tank 1 and is a cross-shaped vertical perforated (or mesh) bulkhead consisting of two sheets 17 and 18 located perpendicular to each other, sheet 17 is placed along the tank 1 along its entire height from the forward hull transverse bulkhead 4 to the rear hull transverse bulkhead 5, the second sheet 18 is installed across the tank 1 along its entire height from the starboard side overlap 11 to the left side overlap 12. Sheets 17 and 18 are fixed at the corners and at several points with the help of embedded foundations and reinforcements 19 along the upper edge to the overhead of the deck overlap of the tank 7 and the inclined section of the inner deck 14, and along the lower edge - to the bottom overlap 8 and the inclined section of the side overlap of the 15th tank.The side edges 20 and 21 of panels 17 and 18 are loosely adjacent to the hull's transverse forward 4 and aft 5 bulkheads and vertical side partitions 11 and 12, but are not secured to them. Panel 17 is continuous along its entire length, while panel 18 has a break along the line of contact with panel 17, forming two sections—one on the starboard side of bulkhead 17 and one on the port side of it.

[0057] The technical result achieved using the third version of the device is achieved as follows.

[0058] The operating mechanism of the cruciform soft-shell bulkhead is similar to that of the first and second options. The cruciform bulkhead allows the entire tank volume to be divided into four smaller volumes and free surface areas. This ensures uniform distribution of dynamic and wave loads from sloshing between all the cargo tank floors during ship roll, thereby reducing their impact on the side floors with their membrane and thermal insulation. Securing panels 17 and 18 using embedded foundations and reinforcements 19 only along their upper and lower edges, without fixing them along the side edges 20 and 21, ensures a favorable stress-strain state, eliminating deformations and shear stresses. Limiting the movement and agitation of the free surfaces of the liquid cargo in all four parts of the volume reduces the intensity of boil-off gas formation during ship roll.

[0059] Thus, bulkheads installed inside the membrane tanks of a gas carrier vessel when it is partially filled make it possible to control the movement of liquefied gas, ensure the safety of the transportation of liquid cargo, minimize the risks of accidents, damage and leakage of LNG in unstable marine environments, and increase the reliability and strength of the membrane cargo tank.

Claims

1. A device for reducing hydrodynamic loads from splashing of liquid cargo in a membrane tank of a gas carrier vessel, which is a soft-shell bulkhead and is located inside the membrane tank, characterized in that the bulkhead is made of a soft single-layer cryogenic-resistant material and has perforations over its entire surface, is installed vertically along the vessel along its centerline plane along the entire height of the tank from the forward hull bulkhead to the rear, with the help of embedded foundations and reinforcements the bulkhead is fixed at the corners and at several points along its entire length from above to the deck head of the tank, from below - to the bottom floor of the tank, the side edges of the bulkhead are freely adjacent to the hull transverse bulkheads of the tank and are not secured to them.

2. A device for reducing hydrodynamic loads from the splashing of liquid cargo in a membrane tank of a gas carrier vessel, which is a soft-shell bulkhead and is located inside the membrane tank, characterized in that the bulkhead is made of a cryogenic-resistant mesh material with a fine mesh, is installed vertically across the entire height of the tank from one side floor to the other and is fixed at the corners and at several points along its entire length using embedded foundations and reinforcements along the upper edge to the overhead of the deck floor of the tank and the inclined section of the inner deck, along the lower edge - to the bottom floor of the tank and the inclined section of the side floor, the side edges of the bulkhead are freely adjacent to the vertical side floors of the tank and are not fixed to them.

3. A device for reducing hydrodynamic loads from splashing of liquid cargo in a membrane tank of a gas carrier vessel, which is a soft-shell bulkhead and is located inside the membrane tank, characterized in that the bulkhead is made in the form of two perforated sheets of soft single-layer cryogenic-resistant material, located perpendicular to each other along the entire height of the tank, one sheet is solid and is installed vertically along the tank from its forward hull transverse bulkhead to the rear, the second sheet is located vertically across the tank from one side overlap to the other and has a gap at the point of contact with the longitudinally installed sheet, with the help of embedded foundations and reinforcements, the cross-shaped bulkhead is fixed at the corners and at several points along the upper edge to the ceiling of the deck overlap of the tank and the inclined section of the inner deck,and along the lower edge - to the bottom cover of the tank and the inclined section of the side cover of the tank, the side edges of the panels freely adjoin the front, rear bulkheads and vertical side covers of the tank and are not secured to them.

4. A device for reducing hydrodynamic loads from splashing of liquid cargo in a membrane tank of a gas carrier vessel according to paragraph 1 or 2, characterized in that the number of vertical bulkheads may be one or more.

5. A device for reducing hydrodynamic loads from splashing of liquid cargo in a membrane tank of a gas carrier vessel according to paragraph 3, characterized in that the cross-shaped bulkhead can be made of a mesh material with a fine mesh.

6. A device for reducing hydrodynamic loads from splashing of liquid cargo in a membrane tank of a gas carrier vessel according to any of paragraphs 1, 2 or 3, characterized in that the bulkhead can be made of a high-strength material such as K49 Kevlar with or without a cryogenic elastomer coating.

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