RU2727768C1 - Ship for transportation of liquefied natural gas and method of its construction - Google Patents

Abstract

FIELD: shipbuilding.SUBSTANCE: invention relates to the field of transport shipbuilding, means of marine transportation and storage of liquefied natural gas (LNG) and concerns creation of a gas carrier vessel and cargo container for transportation and storage of LNG. Disclosed is a vessel for LNG transportation, comprising LNG storage and transportation containers installed on housing by means of pliable supports, comprising heat insulated shells consisting of several layers, at least two of which are metal and sealed, wherein one of them is in contact with liquefied gas and is supported by the set and bulkheads, wherein the metal sealed layers are made of hollow aluminum panels welded together to form a multilayer shell, wherein the multilayer shell together with the set and bulkheads connected to it form a strong container structure, and between ship hull and strong vessel structure is multilayer heat insulation from easily deformed elements with hollow areas. Also disclosed is a method of constructing a gas carrier vessel with cargo tanks for LNG.EFFECT: technical result consists in improvement of strength and operational reliability of cargo container for transportation and storage of LNG, reduced probability of its leakage, reduced duration of construction of vessel and cost of gas carrier.6 cl, 3 dwg

Description

The invention relates to the field of transport shipbuilding, means of sea transportation and storage of liquefied natural gas (LNG) and concerns the issue of creating a gas carrier and a cargo capacity for transporting and storing LNG.

During the sea transportation of LNG on LNG carriers, self-supporting containers (tanks) of the SPB type are used, developed by the Japanese company IHI (SPB ship for the transportation of liquefied gas "Polar Eagle" LNG. // Advertising brochure of the company "IHI MARINE UNITED INC" Japan, 2006) , which are a robust structure with an inner set and outer insulation, corresponding in shape to the inner space of the ship's compartment. The container does not have direct contact with the inner bottom and inner side of the vessel. There is a gap (access space) between the tank and the ship's hull for ease of inspection. Tank support structures are installed between the bottom of the vessel and the bottom of the tank. They contain elastic elements (dock-type wooden cages), which reduce the deformations transmitted to the SPB tank from the general bending of the hull and bending of the bottom floor. There are also flexible stops against displacement of the tank when rolling. The absence of rigid connections between the ship's hull and the SPB tank ensures that there are no thermal stresses.

Storage tanks of the SPB type are usually made of stainless steel (or high-nickel-alloyed steel - 9% Ni) or aluminum.

In most cases, the SPB design is performed along the longitudinal set system. Within the tank, usually one baffle transverse bulkhead is installed; in the center plane, a strong or baffle bulkhead can also be installed, if it is not there, a powerful frame beam is installed. To support the frame frames, two or more horizontal shelves are installed.

The insulation is installed on the smooth outer surface of the SPB tank. A secondary barrier is installed on the bottom of the tank surface to allow leaked LNG droplets to drain into the sump.

The disadvantage of self-supporting self-supporting containers of the SPB type is their large weight and, due to the presence of an access space, the small (in comparison with membrane cargo containers) utilization of the ship's volume, which reduces its economic efficiency, the low efficiency of the secondary barrier, which does not serve to prevent the leakage of LNG from the sealed container, but only to collect it.

Also known is a membrane cargo tank for transportation and storage of LNG, consisting of a composite shell, forming a sealed and thermally insulated tank, built into the supporting structure of the ship (European patents No. 248721 and No. 573327). The reservoir contains two sealed barriers, and the primary barrier is in contact with the substance contained in the reservoir, and the secondary barrier is located between the primary barrier and the supporting structure; the aforementioned sealed barriers alternate with two thermal barriers (primary and secondary).

French patents No. 1376525 and No. 1379651, as well as patent of the Russian Federation No. 2282101, publ. 08/20/2006, Bulletin No. 23 (prototype) describe the design of a membrane cargo tank containing, as a primary hermetic barrier, metal plates with corrugated corrugations in contact with LNG, on the surface of which two series of waves are formed, between which flat surfaces are located. The first series is located perpendicular to the waves of the second series. Waves of one series have a lower height than waves of the second series, so that the waves of the first series are interrupted when they intersect with the waves of the second series.

The prototype membrane tanks are membranes with insulation, resting on the inner side, the inner bottom and in contact with the deck. Their advantage is the high degree of utilization of the ship's volume and the low cost of LNG transportation. The disadvantages of such containers are usually low strength and reliability associated with the presence of direct contact with the body.

The disadvantages of the method for the construction of gas carriers with such tanks include the high cost of work due to the large volume of installation of membrane tanks, and the long construction time associated with the need to complete the main work on the creation of the hull at the first stage of construction, and then, at the second stage, installation on membrane capacities, and the duration of these stages are comparable.

The disadvantages of such a constructive solution of the tank are the low strength and reliability of the primary and secondary hermetic barriers under external force influences (with the phenomenon of slashing in tanks, i.e., beating of LNG against the side walls of the tank during transportation, during wave and ice impacts on the vessel, in case of emergency collisions of the LNG carrier with other vessels or navigational obstacles), as well as temperature drops during filling or emptying of the cargo tank. These disadvantages are due to the following reasons:

- the presence of an intense hydrodynamic effect of liquefied gas on the side and ceiling surfaces of the tank during slashing;

- deep plastic deformation of the sheets of the primary barrier during its manufacture, associated with the need (to achieve the required shape of the product) the formation in it of large residual deformations and stresses caused by local stretching and compression, which have a very negative effect in the future on the static and fatigue strength of the barrier;

- the appearance of significant local stresses in the zones of deep plastic deformation under static and dynamic external influences from the transported (stored) liquid, as well as under temperature influences associated with filling (emptying) the cargo tank with liquid;

- the presence of relatively rigid structures of thermal insulation in the form of boxes with filler, displaced relative to each other in case of emergency damage to the body and do not prevent the development of such damage. Such displacement can, if the case is damaged, lead to a breach of the tightness of both the primary and secondary barriers.

The presence of such disadvantages has a particularly negative effect on the creation of large cargo tanks, as well as during the operation of partially filled tanks, associated with the appearance of slashing under wave conditions and is expressed in the loss of the structure tightness, in the plastic deformation of the material of the primary and secondary barriers and in the increase in the likelihood of fatigue cracks. An increase in the thickness of the plates of hermetic barriers does not lead to the elimination of design flaws, since it increases the material consumption of the structure, reduces the flexibility (flexibility) of the barriers, which is necessary (especially in the area of intersection of corrugated corrugations of mark type insulation) to ensure the possibility of thermal compression and expansion of the plates without the risk of breaking the tightness.

The objective of the present invention is to increase the strength and reliability of a cargo tank for transportation and storage of liquefied gas, to reduce the likelihood of breaking its tightness, to reduce construction costs and its duration.

This problem is solved due to the fact that a vessel for the transportation of liquefied natural gas, including installed on the hull with the help of flexible supports for storage and transportation of liquefied natural gas, containing thermally insulated shells consisting of several layers, at least two of which are metal and sealed, and one of them is in contact with liquefied gas and is supported by a set and bulkheads, has the following differences: metal sealed layers are made of hollow aluminum panels connected by welding to form a multilayer shell, while the multilayer shell forms, together with the set and bulkheads connected to it robust structure of the tank, and between the hull of the vessel and the robust structure of the tank there is a multilayer thermal insulation made of easily deformable elements with hollow areas.

And also, the multilayer thermal insulation of a container made of easily deformable elements contains cavities and is made in the form of interconnected multilayer hollow pliable panels made of polymer composite material, and the panels contain two outer skins and shock-absorbing (pliable) elements in the form of at least one plate located inside the panel between the skins, as well as the diaphragms connecting them, which are offset relative to each other.

And also, the multilayer thermal insulation of the container made of easily deformable elements with hollow areas is made of fiberglass, while the hollow areas are filled with fibrous mineral wool.

And also, the multilayer thermal insulation of the container made of easily deformable elements with cavities is made in the form of large-sized blocks mounted on the ship's hull.

In addition, this problem is solved due to the fact that the method of building a vessel for transporting liquefied natural gas with flexible supports installed on its hull for storage of liquefied gas containing thermally insulated shells consisting of several layers, at least two of which are metal and sealed, and one of them is in contact with LNG and is supported by a set and bulkheads, consisting of the sequential fabrication of the ship's hull, manufacturing and mounting on the hull of individual elements with the formation of multilayer thermal insulation, manufacturing and mounting on the hull of a sealed shell, which forms, together with welded to with a set and bulkheads, a solid structure of a liquefied natural gas tank, has the following differences: the manufacture of a ship's hull, durable structures of LNG tanks and large-sized thermal insulation blocks is carried out simultaneously and separately, then installation on the hull of a large-size ship is carried out thermal insulation blocks in the ship's compartments, after which solid structures of LNG tanks are installed as ready-made modules.

And also, the installation of strong structures of tanks is performed with deformation of the elements of thermal insulation located on the sides and transverse bulkheads of the vessel, and with the formation of interference in the connection of these structures with thermal insulation.

According to the invention, the primary and secondary hermetic cargo tank barriers are made in the form of extruded or extruded hollow aluminum alloy panels containing inner and outer layers connected by inclined elements. The cavities of the panels are made in the form of sealed volumes filled with an inert gas and equipped with natural gas analyzers that signal the detection of a leak.

The panels form a three-layer shell, corresponding to the shape of the internal space of the compartment of the gas carrier. From the inside, the shell is connected to a set and one or more bulkheads (transverse and longitudinal). The shell, set and bulkheads form a robust container structure. On the outer side of the shell (between it and the body) there is thermal insulation, which also corresponds to the shape of the inner space of the compartment.

Additional (in relation to thermal insulation) elastic supports (stops) can also be located between the solid structure of the tank and the body of the gas carrier. The supports between the bottom of the vessel and the bottom of the tank can be made in the form of elastic wooden cages (dock type), or from blocks made of high density foam. Blocks can have fiberglass linings and reinforcement. It is possible to use panels with external cladding made of fiberglass. The skins are glued together with an inner fiberglass layer, which has a trapezoidal cross-section. The internal cavities of the panels are filled with high density foam.

In the upper and lower parts of the container, flexible stops can be installed to prevent its displacement during rolling. The stops can have the same design as the supports.

In the first embodiment, the thermal insulation can be made of panels attached to the surface of the cargo tanks with clamps or glue and consisting of fibrous mineral wool (encased in a fiberglass sheath), foamed ebonite or low density foam.

Thermal insulation can be made in the second embodiment in the form of a multilayer hollow flexible fiberglass panel containing two outer skins and damping elements in the form of at least one plate located inside the panel between the outer skins, as well as diaphragms connecting them, the latter from the upper and lower sides of the shock-absorbing elements are offset relative to each other in the cross-section of the panel. The internal cavities of the panel can be filled with a flexible filler (mineral wool of fibrous design). The diaphragms can be arranged vertically, and their width is variable along the height of the compartment. It decreases with an increase in the distance from the second bottom of the vessel in such a way that when the cargo tank is lowered during its installation, the shock-absorbing elements are deformed under the influence of weight forces and the tank is seated in its place in the compartment of the gas carrier with the formation of horizontal interference forces, which increases as the tank is lowered.

The implementation of the primary and secondary sealed barriers in the form of a shell welded from hollow aluminum panels reduces the labor intensity of manufacturing sealed barriers, increases their strength and reduces the weight of a robust container structure in comparison with a similar structure of an SPB container. Filling the panel cavities with inert gas and its leakage detectors increases the safety of LNG transportation.

The presence of an internal set of robust structures and bulkheads provides a multiple reduction in the loads on the structures and their weight.

The implementation of thermal insulation in the form of deformable elements with high flexibility provides protection of the robust structure of the tank from damage in emergency situations (collisions with ships and large ice formations, grounding).

Fitting a robust vessel hull into place in the ship's compartment with interference creates resistance to the LNG pressure in the vessel and increases its strength and reliability.

The absence of a direct transfer of forces from the body of the gas carrier to hermetic barriers through heat-insulating boxes made of plywood (as is customary on the prototype) makes it possible to increase the operational reliability of the thermal protection, its heat-insulating properties and the safety of the container as a whole. The essence of the invention is illustrated by drawings, which show:

a diagram of a cross-section of a gas carrier with the proposed cargo capacity (Fig. 1);

one of the options for the cross-section of a hollow aluminum panel for the manufacture of a shell of a durable structure of the proposed cargo tank for transportation and storage of LNG (Fig. 2);

an element of the proposed thermal insulation in the form of a multilayer pliable fiberglass panel (Fig. 3).

The known cargo container of the SPB type contains a robust casing, protected by a heat-insulating layer and installed in the compartment of the LNG carrier with the help of supports, so that between the container and the LNG carrier there is an access space used for inspecting the durable housing.

Membrane cargo tank type Mark III has a structured shell, fixed to the body of the gas carrier, consisting of corrugated primary and secondary sealed metal barriers, separated by layers of thermal insulation.

The proposed cargo tank for transportation and storage of LNG (Fig. 1) contains a robust aluminum tank body, including a hollow aluminum panel 1 (Fig. 2), a set of sides 2, a set of bottom 3, a set of an upper platform 4, a bulkhead with skin 5 and a set with shelves 6. The durable aluminum body of the tank is mounted on the body 7 of the gas carrier with the help of supports 8, so that flexible thermal insulation 9 is located between the tank and the body of the gas carrier, which in the second version can have the form of a panel (multilayer hollow or filled with thermal insulation material) containing two skins 10 and 11 and yielding elements in the form of at least one plate 12 located inside the panel, as well as diaphragms 13 connecting them, the places whose fixings on the yielding element are offset relative to each other.

When the strong body of the tank is deformed as a result of a sharp change in its temperature, as well as in the event of an emergency elastoplastic deformation of the body of the gas carrier, deformation of the pliable heat-insulating layer occurs, accompanied by large relative displacements of its plates (skins). This deformation prevents damage and destruction of the robust container body and LNG leakage.

In the second embodiment, when flexible multi-layer panels are used in the heat-insulating layer, there is a significant bending of the shock-absorbing elements (plates) inside the panel, which contributes to the elastic displacement of the panel skins relative to each other and imparts reduced rigidity to the panels.

Achievement of the technical result using the proposed version of the tank for transportation and storage of LNG is carried out as follows.

In the event of temperature differences associated with the filling of gas into the cargo tank or with its emptying, the thermal expansion or contraction of the solid structure of the tank does not lead to the appearance of temperature stresses, deformations and displacements, since the latter are easily compensated by deformation of the flexible structure of the thermal insulation.

The presence of two hermetic barriers in the form of a strong and reliable multilayer shell eliminates the need to create an access space, makes it possible to control gas leakage and achieve an optimal thickness of the heat-insulating layer, which excludes the high rate of evaporation of LNG during transportation and storage.

The proposed method of building a gas carrier is distinguished by the fact that the manufacture of the ship's hull, strong structures of cargo tanks and large-sized blocks of thermal insulation is carried out simultaneously (in parallel), and not sequentially (as is customary when creating gas carriers with membrane cargo tanks for transporting and storing LNG) , then the installation of thermal insulation blocks in the compartments of the ship is carried out on the hull, after which the installation of durable structures of tanks for the transportation and storage of LNG is carried out.

Thus, the proposed designs of the tank for the transportation and storage of LNG and the design of its interface with the hull of the gas carrier allow to reduce the loads during slashing, increase the strength and reliability of the cargo tank and reduce the likelihood of breaking its tightness, reduce the volume and cost of installing elements of hermetic barriers and thermal insulation, which distinguishes these containers from the prototype. The proposed method of building a gas carrier vessel allows for the simultaneous (parallel) manufacture of the ship's hull, strong structures of cargo tanks and thermal insulation structures, which reduces the duration and cost of building a gas carrier.

Claims (6)

1. A vessel for the transportation of liquefied natural gas, including tanks mounted on the hull with the help of flexible supports for storing and transporting liquefied natural gas, containing thermally insulated shells consisting of several layers, at least two of which are metal and sealed, one of them is in contact with liquefied gas and is supported by a set and bulkheads, characterized in that the metal hermetic layers are made of hollow aluminum panels connected by welding to form a multilayer shell, while the multilayer shell, together with the set and bulkheads connected to it, forms a solid structure of the container, and between the vessel's hull and robust construction of the tank contains a multilayer thermal insulation made of easily deformable elements with hollow areas. 2. The vessel for transportation of liquefied natural gas according to claim 1, characterized in that the multilayer thermal insulation of the container from easily deformable elements contains cavities and is made in the form of interconnected multilayer hollow pliable panels made of polymer composite material, and the panels contain two outer skins and shock-absorbing ( compliant) elements in the form of at least one plate located inside the panel between the skins, as well as diaphragms connecting them, which are displaced relative to each other. 3. The vessel for transportation of liquefied natural gas according to claim 1, characterized in that the multilayer thermal insulation of the container of easily deformable elements with hollow regions is made of fiberglass, while the hollow regions are filled with fibrous mineral wool. 4. The vessel for transportation of liquefied natural gas according to claim 1, characterized in that the multilayer thermal insulation of the container from easily deformable elements with cavities is made in the form of large-sized blocks attached to the ship's hull. 5. A method of building a vessel for the transportation of liquefied natural gas with tanks for storing liquefied gas installed on its hull with yielding supports, containing thermally insulated shells consisting of several layers, at least two of which are metal and sealed, and one of them is located in contact with liquefied natural gas and reinforced with a set and bulkheads, consisting of the sequential manufacture of the ship's hull, manufacturing and mounting on the hull of individual elements with the formation of multilayer thermal insulation, manufacturing and mounting on the hull of a sealed shell, which together with the set and bulkheads welded to it forms a solid structure liquefied natural gas tanks, characterized in that the manufacture of the ship's hull, durable structures of liquefied natural gas tanks and large-sized thermal insulation blocks is carried out simultaneously and separately, then large-sized blocks are installed on the ship's hull in thermal insulation in the ship's compartments, after which solid structures of liquefied natural gas tanks are installed as ready-made modules. 6. The method of building a vessel for transporting liquefied natural gas according to claim 5, characterized in that the installation of strong structures of containers is made with deformation of the thermal insulation elements located on the sides and transverse bulkheads of the vessel, and with the formation of interference in the connection of these structures with thermal insulation.

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