Wall of diaphragm tank for cold fluid medium

Abstract

The invention relates to the field of construction materials, and more particularly to the manufacture of hermetically sealed and thermally insulated tanks for cryogenic fluids. An impermeable wall of a tank comprises two mutually perpendicular sets of parallel wave-like corrugations. At the points of intersection, one of each of the two intersecting corrugations is interrupted, forming symmetrical gradual curves which transition into flat regions on either side of the corrugation with which it intersects, wherein the differently oriented corrugations are interrupted in an alternating fashion. The technical result is that of rendering the wall of the tank pliable to accommodate temperature-related deformations without damage by providing the wall of the tank with corrugations that have an optimal shape and mutual arrangement, while also making it possible to stamp such a wall in a single operation.

Description

[0001] WALL OF A MEMBRANE TANK FOR COLD LIQUID

[0002] Field of technology to which the invention relates

[0003] The invention relates to the field of manufacturing membrane tanks for storing and / or transporting cryogenic fluid, which are sealed and thermally insulated, and more specifically to an insulating structure for such tanks.

[0004] State of the art

[0005] Numerous experts and specialists believe that liquefied natural gas (LNG) holds the future of the global energy industry. LNG logistics are constantly evolving and being optimized. The ability to transport the fuel across oceans and continents makes it unique and significantly expands its application. Large-capacity tanks are used for sea transportation. Requirements for LNG storage tanks are quite stringent and are regulated by numerous regulations. Only nickel-containing steel is used in the construction of LNG storage facilities. This choice is driven by structural strength and low-temperature resistance, specifically the need to reduce the likelihood of brittle fracture when exposed to extremely low temperatures. Designs employing a unique double wall: an inner (membrane) made of nickel-containing steel, and an outer wall, which can be made of alternative materials.At the same time, in relation to double-wall structures, a search is constantly underway to improve their required properties.

[0006] One of the areas of technical development in this area is the use of corrugated membranes. It is known that an impermeable wall in direct contact with a cryogenic liquid must be sufficiently elastic to withstand loads arising from, for example, hydrostatic pressure, dynamic pressure (due to cargo movement), and thermal contraction and expansion. Technologies using corrugated membranes are based on the ability of the corrugations to absorb membrane deformations under thermal loads acting on the tank walls.

[0007] An example of such an implementation is the technical solution described in document SU 293372 AZ, published January 15, 1971, which discloses a thermally insulated wall for a liquid tank, including an internal, sealed, corrugated membrane located at a distance from the outer shell. The technical result of the invention is the elimination of heat-conducting channels that cool the casing. To achieve this, the assemblies that secure the membrane tank's position relative to the rigid casing are designed as rigid angle elements with stiffening ribs. However, the proposed solution suffers from the drawback that the tank design is not sufficiently reliable in operation and does not provide compensation for thermal stresses.

[0008] In this regard, a number of technical solutions have been proposed to ensure reliability and more effective compensation of thermal stresses by improving thermal insulation blocks.

[0009] To reduce thermal stress, a technical solution presented in WO 2005095234 A1, published October 13, 2005, is proposed. It discloses a metal membrane panel for an insulated LNG cargo tank, which includes a plurality of rectangular single corrugations arranged on the panel so as to be spaced from one another at a predetermined distance. Each of the plurality of rectangular single corrugations consists of a pair of transverse convex portions and a pair of longitudinal convex portions and has smoothly curved corners. Transverse and longitudinal connecting corrugations connect the plurality of rectangular single corrugations to one another. The corrugations may have semicircular, elliptical, or parabolic cross-sections.

[0010] The technical result of this solution is a reduction in localized stress concentration zones and increased welding efficiency by reducing the number of corrugations on the overlapping weld edges of the adjacent panel with the metal membrane, thereby reducing the number of curved sections to be welded. However, the proposed corrugation design does not fully realize the potential for reducing thermal stress in the membrane.

[0011] Another example of the membrane tank wall design for LNG is the technical solution presented in document KR 101908563 B1, published on 16 October 2018, which discloses a thermal insulation structure for a cryogenic liquid storage tank, integrated with the inner wall of the storage tank. The design comprises: a plurality of thermal insulation slabs located on the inner wall of the storage tank at a distance from one another; a lintel extended between adjacent thermal insulation slabs; a cover element mounted on the lintel; and unit membranes secured to the thermal insulation slabs. This solution helps to minimize stress concentration on the tank membrane. Another aspect of improving LNG tanks is disclosed in the technical solution presented in RU 2563563 C2, published on 09 / 20 / 2015, which discloses a stiffening element designed to be inserted into a high corrugation in the direction of the outer surface of the sheet.Corrugated metal sheet is suitable for forming an impermeable membrane for a large-capacity tank, such as one intended for cold liquid products. The stiffening element has a profiled geometry with a constant cross-section, allowing for easy production of the required length by cutting a long profiled product.

[0012] Thanks to the proposed additional stiffening elements, it is possible to eliminate or limit dangerous plastic deformations caused by the hydrostatic pressure of the liquid gas contained in the tank, as well as the impacts of waves generated in it during sea transportation.

[0013] The reliability of a membrane-based storage tank is addressed in the technical solution presented in JP 2001058693 A, published March 6, 2001, which pertains to a membrane-based design for a low-temperature liquefied gas storage tank. The tank's side surfaces are octagonal, while the entire tank is a 10-sided structure. This tank is rigidly mounted within an outer tank using thermal insulation material made of hard urethane or a similar material. On each side surface, pairs of longitudinal corrugations are arranged in a grid pattern in the vertical and horizontal directions, respectively. On the bottom surface and ceiling surface, pairs of long-axis corrugations are arranged in a grid pattern.

[0014] In the tank described above, during the cooling and heating associated with storing low-temperature liquefied natural gas (LNG), the rectangular flat plate section has the ability to move angularly as the corrugations expand and contract, absorbing thermal effects. Furthermore, at each corner of the bottom and ceiling surfaces, the triangular flat plate section rotates as the corrugations expand and contract, allowing for thermal shrinkage compensation and ensuring smooth contraction continuation during rotation between each plate surface, even at the corner where the rectangular plate surfaces meet.

[0015] This results in smooth thermal contraction and expansion characteristics and the ability to absorb them without damage to the tank. The closest technical solution to the proposed one, eliminating the aforementioned drawbacks of known membrane tank wall designs and ensuring a maximum reduction in thermal stress, is a stamped membrane metal wall for a thermally insulated tank, disclosed in KR 20050108692 A, published November 17, 2005. By optimizing the shape and arrangement of the corrugations, as well as the method for positioning the membrane metal panel, a reduction in stress levels under operating conditions is achieved. The membrane metal panel is made of a metal that is less brittle at low temperatures and is designed to facilitate expansion and contraction in response to temperature changes.This solution incorporates multiple transverse corrugations formed parallel to each other and at right angles to the transverse corrugations. The transverse and longitudinal corrugations do not intersect, but are instead positioned at 90° to each other, with their ends positioned opposite the midpoints of adjacent corrugations. Furthermore, the radii of curvature and the cross-sectional dimensions of the corrugations are selected to reduce stress and increase durability. As a result, this solution increases the durability of the tank while simultaneously reducing production costs.

[0016] Another drawback of the above-mentioned known solutions is their insufficient reduction of stress concentrators, which leads to increased stress levels in these areas and, consequently, reduced service life. The formation of such stress concentrators is caused by the membrane tank wall's design, which still contains sharp changes in its geometry, namely, small corrugation radii and sharp transitions / bends.

[0017] Thus, there is currently a need to optimize the design of the impermeable wall of a membrane tank in order to increase its fatigue life, since the known designs of the primary membrane contain a large number of geometric stress concentrators, which in turn worsens the performance characteristics of such a tank.

[0018] Disclosure of invention

[0019] To solve the stated problem of minimizing the stresses of the sealed wall of a membrane tank when exposed to cryogenic temperatures, the present invention proposes a design for the sealed wall of a membrane tank that will have increased fatigue life relative to known solutions from the prior art, i.e., which will be able to withstand temperature deformations without its further destruction due to the optimization of the mutual combination of design parameters.

[0020] The proposed membrane tank wall according to the invention also provides a simple and cost-effective method for its manufacture.

[0021] The technical result is to ensure the flexibility of the tank wall to withstand temperature deformations without destruction by producing a tank wall with corrugations of an optimal shape and their mutual arrangement, while ensuring the possibility of stamping such a wall in one operation.

[0022] In accordance with the tasks set, a design is proposed for an impermeable wall of a membrane tank, the inner surface of which is in direct contact with a low-temperature fluid medium, made of a flexible material, which is a sealed membrane containing a first set of parallel wave-shaped corrugations and a second set of parallel wave-shaped corrugations protruding from the inner surface of the tank, wherein the corrugations of the first set have a direction perpendicular to the direction of the corrugations of the second set, forming intersections.At the specified intersection points, one of the two intersecting corrugations is made interrupted, forming symmetrical smooth roundings (6.5) on both sides of the transverse corrugation, obtained using the radius of curvature (6) of rounding the inner part of the corrugation and the outer radius of curvature (5) of rounding the corrugation, and transitioning into flat plastically strengthened sections (4) adjacent to the transverse corrugations. The size of the flat section (4), determining the distance between the base of the rounded end of the corrugation and the base of the lateral part of the corrugation perpendicular to it, ranges from 10 to 50 mm. The radius of curvature (3) of the rounding of the corrugation at its base from the side surface is from 10 to 30 mm, and the radius of curvature (5) of the rounding of the corrugation at its base from the end surface facing the adjacent corrugation at the point of their intersection is from 60 to 80 mm, the height (8) of the corrugation is from 30 to 60 mm.The ratio of the radius of curvature (6) of the rounding of the corrugation at its apex on the side of the end internal surface to the radius of curvature (5) of the rounding of the corrugation at its base on the side of the end external surface is equal to 2.5±5%, and the ratio of the distance (7) from the point of intersection of the flat surface with the end of the corrugation to the middle of the cross-section of the corrugation perpendicular to it to the distance (4) from the point of intersection of the flat surface with the end of the corrugation to the point of intersection of the flat surface with the side surface of the corrugation perpendicular to it is equal to 3.2±5%. In this case, the interruptions of the corrugations of different directions are made alternating in a checkerboard pattern.

[0023] Moreover, each corrugation of such a membrane is designed to reduce geometric stress concentrators and simplify the manufacturing process. Therefore, in addition to the aforementioned radii of curvature (5, 6), it also contains roundings directed along the corrugation, as well as several bending radii in the transverse direction of the corrugation, such as the radius of curvature (1) of the rounding near the apex of the inner portion of the corrugation, the radius of curvature (2) of the rounding of its lateral inner portion, and the radius of curvature (3) of the rounding of the lateral outer portion of its base. Furthermore, the interruptions of the corrugations in different directions are performed in an alternating staggered pattern, which also affects the achievement of the technical result.

[0024] In this case, the sealed wall is designed to be located in the tank in such a way that its corrugated part is in direct contact with the low-temperature liquid medium (for example, LNG).

[0025] In one embodiment, the radius of curvature (1) of the section of the corrugation adjacent to its top is from 8 to 28 mm, and the radius of curvature (2) of the transition between this section of the corrugation and the rounding at the base of the corrugation may be the same relative to the axis of symmetry of the corrugation and is from 45 to 65 mm.

[0026] In one embodiment, the wall is formed from a plurality of overlapping sheets, each sheet having molded projections on at least two of its side faces, which serve to allow the entry of adjacent sheets and extend along the entire length of the side face of the sheet, including the surface of the corrugations.

[0027] In one embodiment, all of the corrugations may have a substantially semicircular cross-section, the geometry of which depends on the radius of curvature (1) of the rounding near the top of the inner part of the corrugation and the radius of curvature (2) of the rounding of its lateral inner part.

[0028] In one embodiment, all corrugations may have the same shape and dimensions in length, width and height (8).

[0029] In one embodiment, the corrugations of the first set and the corrugations of the second set may be located at the same distance from each other, and the distance (4) between the corrugations of the first set may be equal to the distance (4) between the corrugations of the second set.

[0030] In one embodiment, the corrugations of each set may extend from one edge to the other edge of the membrane sheet. b In one embodiment, each of the corrugations of the first set may be positioned perpendicular to and exactly in the middle of the intersections of the corrugations of the second set.

[0031] In one embodiment, the welding of corrugated sheets may be carried out end-to-end.

[0032] In one embodiment, the impermeable wall may be made of stainless steel.

[0033] In one embodiment, the corrugations may be formed by cold stamping in a single process step.

[0034] In another aspect of the invention, a sealed and thermally insulated tank for storing and / or transporting a low-temperature fluid medium is proposed, in which the supporting wall of the tank has a multilayer structure containing sequentially arranged: a main sealed barrier consisting of a wall in direct contact with the low-temperature fluid medium, a main thermal insulation barrier, an auxiliary sealing membrane and an auxiliary thermal insulation barrier, wherein the auxiliary thermal insulation barrier, the auxiliary sealing membrane and the main thermal insulation barrier essentially consist of a set of prefabricated panels fixed on said supporting wall of the tank, wherein the supporting wall of the tank contains thermal insulation blocks supporting the main sealed barrier.

[0035] The wall forming the hermetic barrier of the said tank is made of a flexible material, contains a first set of wave-shaped corrugations parallel to each other and a second set of wave-shaped corrugations parallel to each other, wherein the corrugations of the first set have a direction perpendicular to the direction of the corrugations of the second set with the formation of intersection points, wherein at the said intersection points one of the two intersecting corrugations is made interrupted, with the formation on both sides of the transverse direction corrugation of symmetrical smooth roundings (6.5), turning into flat sections (4) adjacent to the transverse direction corrugations, wherein the interruptions of the corrugations of different directions are made alternating in a checkerboard pattern, the size of the flat section (4), which is the distance between the base of the rounded end of the corrugation and the base of the lateral part of the corrugation perpendicular to it, is from 10 to 50 mm,the radius of curvature (3) of the rounding of the corrugation at its base from the side surface is from 10 to 30 mm, the radius of curvature (5) of the rounding of the corrugation at its base from the end surface facing the adjacent corrugation at the point of their intersection is from 60 to 80 mm, the height (8) of the corrugation is from 30 to 60 mm, the ratio of the radius of curvature (6) of the rounding of the corrugation at its apex from the end inner surface to the radius of curvature (5) of the rounding of the corrugation at its base from the end outer surface is equal to 2.5±5%, and the ratio of the distance (7) from the point of intersection of the flat surface with the end of the corrugation to the middle of the cross-section of the corrugation perpendicular to it to the distance (4) from the point of intersection of the flat surface with the end of the corrugation to the point of intersection of the flat surface with the side surface of the corrugation perpendicular to it is equal to 3.2 ±5%.,

[0036] Brief description of the drawings

[0037] Fig. 1 shows an image of the external appearance of a sealed sheet for producing an impermeable wall of a tank according to the invention.

[0038] Fig. 2 shows a schematic representation of a cross-section of a corrugated sheet with the designation of the design parameters of a sealed sheet for the manufacture of an impermeable wall according to the invention.

[0039] Fig. 3 shows the results of computer simulation, which demonstrate the stress level on a corrugation with a height of 75 mm.

[0040] Fig. 4 shows the results of computer modeling, which demonstrate the stress level of the corrugation intersection node in the absence of a radius of curvature (5) of the rounding of the corrugation at its base on the side of the end outer surface of the corrugation, exposed to a cryogenic temperature of -163 °C.

[0041] Fig. 5 shows the results of computer simulation, which demonstrate the stress level of the intersection node of corrugations containing radii of curvature (5,6), but in the absence of a flat section (4) under the influence of a cryogenic temperature of -163 °C.

[0042] Fig. 6 shows the results of computer simulation, which demonstrate the stress level of the corrugation intersection node, where the size of the flat section (4) is 70 mm and the distance (7) is 136 mm, under the influence of a cryogenic temperature of -163 °C.

[0043] Fig. 7 shows the results of computer simulation, which demonstrate the stress level of the corrugation intersection node, where the size of the flat section (4) is 84 mm and the distance (7) is 150 mm, under the influence of a cryogenic temperature of -163 °C.

[0044] Fig. 8 shows the results of computer simulation, which demonstrate the stress level of the corrugation intersection node, where the radius of curvature (5) is 80 mm, and the radius of curvature (6) is 100 mm, under the influence of a cryogenic temperature of -163 °C.

[0045] Fig. 9 shows the results of computer simulation, which demonstrate the stress level of the corrugation intersection node, where the radius of curvature (5) is 100 mm, and the radius of curvature (6) is 180 mm, under the influence of a cryogenic temperature of -163 °C.

[0046] Fig. 10 shows the results of computer modeling, which demonstrate the stress level of the intersection node of the membrane sheet corrugations with the design parameters of the invention when exposed to a cryogenic temperature of -163 °C.

[0047] Fig. 11 shows the results of computer modeling of a corrugated sheet for the manufacture of a sealed tank wall under a thermal load of -163 °C, the design of which combines the optimal parameters of the corrugations according to the invention.

[0048] Implementation of the invention

[0049] The problem is solved by changing the geometry of the corrugations and their relative positions relative to each other.

[0050] As shown in Fig. 1, the sheet (100) of the sealing membrane comprises two sets of parallel, wave-shaped corrugations of a semicircular cross-section, wherein the corrugations of the first set (101) are perpendicular to the direction of the corrugations of the second set (102) and extend from one edge of the sheet of the sealing membrane to the other. At the intersection of the perpendicular corrugations, one of the two intersecting corrugations is interrupted, and the other remains continuous, but is interrupted at the next, adjacent intersection, forming a pattern similar to a checkerboard weave of fabric fibers. Each sheet (100) has molded protrusions (103) on at least two of its lateral sides, serving for the entry of adjacent sheets and extending along the entire length of the lateral side of the sheet, including the surface of the corrugations.

[0051] In this case, at each intersection point from the remaining continuous corrugation of the transverse direction, the interrupted corrugation forms a smooth end bend line symmetrical on both sides, turning into a flat plastically strengthened section in the direction of the transverse corrugations.

[0052] According to one embodiment of the invention, the continuous corrugation is positioned at the intersection, exactly midway between the rounded ends of the interrupted perpendicular corrugation. This mutually symmetrical arrangement of the two sets of corrugations relative to each other allows for the complete compensation of deformations arising in the tank wall due to the temperature gradient.

[0053] Fig. 2 shows all the main design parameters of a sealed sheet for producing an impermeable wall, which play a significant role in achieving the technical result.

[0054] In the illustrated embodiment of the invention, the end bend line of the corrugation is formed by a smooth transition using two radii of curvature. Thus, the interruption of the corrugation in the longitudinal direction begins with radius (6) from its apex relative to the inner surface and ends at its base with outer radius (5), as shown in Fig. 2.

[0055] According to the invention, all the corrugations have a substantially semicircular cross-section formed by three radii of curvature: the radius of curvature (1) of rounding near the top of the inner part of the corrugation, the radius of curvature (2) of rounding the lateral inner part of the corrugation and the radius of curvature (3) of rounding at the base from the side of the outer lateral surface of the corrugation.

[0056] An important role in the distribution of thermal deformations is played by the size of the flat section (4), which determines the distance between the base of the rounded end of the corrugation and the base of the side part of the corrugation perpendicular to it, as well as the height (8) of the corrugation itself.

[0057] Fig. 3-11 shows the results of computer simulations that demonstrate the stress level on the corrugation, with a color palette where blue corresponds to the lowest stress level and red to the highest, according to the scale of values ​​given in MPa.

[0058] Fig. 3 shows the results of computer simulation, which demonstrate the stress level on the corrugation, the height (8) of which is equal to 75 mm. In Fig. 3 it is evident that the largest stress concentrators with such a height (8) of the corrugation are located on the sides of the corrugation, characterized by the radius of curvature (2), as well as at its top with the radius of curvature (1). It was determined by calculation that the optimal value of the quantity (8), providing minimum membrane stresses, is the range from 30 to 60 mm. When making a corrugation with a height (8) of more than 60 mm (as in Fig. 3), a significant increase in the stress level is observed on the sides of the corrugation, as well as near its top. When the height of the corrugation (8) is less than 30 mm, insufficient compensation of thermal deformations is observed, which is determined during computer simulation by the excess of stresses on the flat sections of the membrane. io In Fig.Figure 4 shows the results of computer modeling of a corrugation intersection without a radius of curvature (5) for the corrugation's rounding at its base, which is exposed to a cryogenic temperature of -163°C. It can be seen that high stresses arise at the end of the corrugation at its base due to thermal deformation, which is a potential source of membrane sheet failure. Constructing corrugations with a radius of curvature (5) prevents the occurrence of such stresses.

[0059] An analysis of the results of numerous calculations to determine the influence of the geometry of the corrugations and their relative position on the load distribution over the entire surface of the sealed wall showed that there is also a relationship between the value of the radius of curvature (6) of the rounding of the top of the inner end surface of the corrugation and the radius of curvature (5) of the rounding at the base of the outer end surface of the corrugation.

[0060] Calculations revealed a relationship between values ​​(5) and (6). The optimal ratio of the radius of curvature (6) of the corrugation rounding at its apex on the inner side of the end surface to the radius of curvature (5) of the corrugation rounding at its base on the outer side of the end surface, from a stress-resistance perspective, is 2.5±5%. Increasing this ratio increases stress along the longitudinal end bend line of the corrugation, which in turn leads to a reduction in the fatigue life of the wall.

[0061] When selecting a design of corrugated sheet, in which the value of the ratio of the radius of curvature (6) of the rounding of the corrugation at its apex on the inner side of the end surface to the radius of curvature (5) of the rounding of the corrugation at its base on the outer side of the end surface is less than 2.5±5%, for the sealed wall of the membrane tank, compensation for all thermal deformations that occur in the tank wall during compression and tension of the metal will not be ensured.

[0062] Furthermore, it was also determined by calculation that there is another relationship between the design parameters of the sealed wall, which directly affect the achievement of the technical result. Such parameters are the distance (7) from the point of intersection of the flat surface with the end of the corrugation to the middle of the cross-section of the corrugation perpendicular to it, and the distance (4) from the point of intersection of the flat surface with the end of the corrugation to the point of intersection of the flat surface with the side surface of the corrugation perpendicular to it. These parameters determine the percentage ratio of the flat part to the convex part in the sealed wall of the tank. li Fig. 5 shows that in the absence of the flat part (4), located between the end part of the corrugation of the first set relative to the corrugation of the second set perpendicular to it, high stress concentrations arise in the designated locations under the influence of cryogenic temperature, where the red color corresponds to the highest stress level.The presence of a large number of stress concentrators leads to accelerated failure of such a wall at the intersections of the corrugations (2, 3, 5) during operation. Therefore, to reduce stress concentrations in such areas, it is advisable to provide a flat section (4) to increase the fatigue life of the sealed membrane. It is worth noting that the presence of flat sections also simplifies the fabrication of membrane sheets. However, when selecting the value of (4), it is necessary to consider the membrane's ability to absorb and compensate for all thermal deformations.

[0063] Calculations revealed a relationship between values ​​(7) and (4) that enhances the technical result. Figures 6 and 7 show the stress level at the corrugation intersection, where the size of the flat section (4) is 70 mm and 84 mm, and the distance (7) is 136 mm and 150 mm, respectively. Thus, the ratios of the sizes of sections (7) and (4) for these membranes are 1.94 and 1.79, respectively. The simulation results confirm that when the value of this ratio is less than 3.2, stress occurs at the end sections of the corrugation at the intersections of the corrugations, as well as on the adjacent lateral sections of the membrane.

[0064] In this case, when making a sealed wall of the tank, in which the ratio of distance (7) to distance (4) is equal to 3.2±5%, temperature deformations will be completely compensated with the most uniform possible distribution of stress over the entire surface of the impermeable membrane, as shown below with reference to Fig. 10.

[0065] Fig. 8 and 9 show the stress level of the corrugation intersection node, where the radius of curvature (5) is 80 mm and 100 mm, and the radius of curvature (6) is 100 mm and 180 mm, respectively. Thus, the ratios of the sizes of radii (5) and (6) for these membranes are 1.25 and 1.8, respectively. The simulation results confirm that when the value of this ratio is less than 2.5, stress occurs at the end sections of the corrugation at the intersection of the corrugations, as well as on the adjacent lateral sections of the membrane.

[0066] Figs. 10 and 11 show the stress distribution at the corrugation intersection for one example of a membrane according to the invention, in which the radius of curvature (5) is 70 mm, and the radius of curvature (6) is 180 mm. When using the sealed wall design according to the invention, the maximum stresses are observed in the radial transition zone from the corrugations to the flat part, but their distribution is uniform, meaning there are no potentially dangerous areas for failure of the impermeable wall during thermal deformation.

[0067] An example of a sealed wall according to the invention is a wall made of corrugated metal sheets of grade 304L stainless steel, comprising two sets of parallel, wavy corrugations of semicircular cross-section. The corrugations of the first set are perpendicular to the direction of the corrugations of the second set and are arranged symmetrically relative to each other and precisely in the middle at their intersections. At these intersections, one of the intersecting corrugations is interrupted, forming symmetrical, smooth curves on both sides of the transverse corrugation, transitioning into flat sections (4) adjacent to the transverse corrugations. All corrugations have the same shape and dimensions.In one non-limiting example, the radius of curvature (1) of the rounding near the top of the inner part of the corrugation is 18 mm, the radius of curvature (2) of the rounding of the lateral inner part of the corrugation is 55 mm, the radius of curvature (3) of the rounding at the base on the side of the outer lateral surface of the corrugation is 20 mm, the flat section (4) is 30 mm, the radius of curvature (5) is 70 mm, the radius of curvature (6) is 180 mm, the distance (7) is 96 mm, and the height (8) of the corrugation is 50 mm.When selecting these parameters, the ratio of the radius of curvature (6) of the rounding of the corrugation at its apex on the inner side of the end surface to the radius of curvature (5) of the rounding of the corrugation at its base on the outer side of the end surface is 2.57, and the ratio of the distance (7) from the point of intersection of the flat surface with the end of the corrugation to the middle of the cross-section of the corrugation perpendicular to it to the distance (4) from the point of intersection of the flat surface with the end of the corrugation to the point of intersection of the flat surface with the side surface of the corrugation perpendicular to it is 3.2.

[0068] Fig. 11 shows the results of computer modeling of a corrugated sheet with the above parameters, illustrating the advantage of the proposed sealed wall design. A single membrane sheet is shown, containing multiple corrugation intersections with stress distribution across the entire surface of the membrane sheet in operating mode. The advantage lies in the ductility of the sealed wall design to withstand temperature deformations arising from contact with a low-temperature medium, with increased fatigue life of such a sealed wall due to the uniform distribution of load across the entire inner surface of the tank. The impermeable membrane sheets according to the invention can be used to create an impermeable wall design (sealed barrier) for the inner lining of a membrane thermally insulated tank for storing and / or transporting a cryogenic fluid.Such an impermeable wall may consist of multiple sheets of the sealing membrane according to the invention, for example, made of stainless steel, joined together by welding to form edge overlap zones to completely seal the wall. Said wall may be in direct contact with the low-temperature fluid.

[0069] Each sheet of the impermeable wall may have molded protrusions on its sides along its entire length. These protrusions allow for overlap welding of adjacent sheets by overlapping the edge zone of one sheet over the edge zone of the adjacent sheet.

[0070] However, in one embodiment, the sheets can be butt-welded. In this case, the membrane sheets will lack the aforementioned molded protrusions.

[0071] The present invention also relates to a sealed and thermally insulated tank for storing and / or transporting a low-temperature fluid, in which the tank wall has a multilayer structure comprising sequentially a primary thermal insulation barrier, an auxiliary sealing membrane and an auxiliary thermal insulation barrier. The auxiliary thermal insulation barrier, the auxiliary sealing membrane and the primary thermal insulation barrier essentially consist of a set of prefabricated panels fixed to the supporting wall of the tank, wherein each prefabricated panel comprises sequentially a lower and an upper rigid plate, a first layer of thermal insulation enclosed between these rigid plates, which forms with the rigid plates an element of the secondary thermal insulation barrier, an impermeable overlay that completely covers the upper rigid plate of the first layer of thermal insulation, being glued to the upper rigid plate of the first layer of thermal insulation,and which forms an element of the auxiliary sealing membrane, a second layer of thermal insulation that covers the central zone of the first layer of thermal insulation and the impermeable overlay, and a rigid plate covering the second layer of thermal insulation and forming, with the second layer of thermal insulation, an element of the main thermal insulation barrier, in which two rigid plates, the first layer of thermal insulation and the impermeable overlay of the prefabricated panel have a first rectangular contour, while the second layer of thermal insulation with the rigid plate have a second rectangular contour of smaller dimensions than the first rectangular contour, as a result of which the second layer of thermal insulation with the rigid plate do not cover the edge zone of the impermeable overlay along the four edges of the first rectangular contour. In this case, the prefabricated panels are placed side by side on the supporting structure,parallel to each other. The edge zone of the impermeable cover of the first prefabricated panel in each case adjoins the edge zone of the impermeable cover of the second prefabricated panel. In addition, the tank wall has thermal insulation blocks covered with a rigid slab, placed between the second layers of thermal insulation of two adjoining prefabricated panels, completing the main insulation barrier between the two prefabricated panels. As a result, the rigid slabs of the insulation blocks and the rigid slabs of the prefabricated panels form a substantially continuous wall capable of supporting the main hermetic barrier of the invention, which is in direct contact with the low-temperature fluid medium.

[0072] The main sealed barrier can be attached to the thermal insulation panels by welding each of the four corners of the sealed sheet to an anchor plate located on the top rigid plate of the upper thermal insulation layer. This type of fastening is flexible, preventing the edge zones of the corrugated sheets from experiencing high thermal stress.

[0073] From the point of view of load-bearing capacity, the proposed configuration of an impermeable wall, in comparison with those known from the prior art, is characterized by a reduction in the level of stresses, and, as a consequence, an increase in the fatigue life of such a wall due to the use of smooth shapes and transitions in its design.

[0074] The proposed corrugation configuration allows for the production of a sealed metal wall that evenly distributes loads across the entire surface of the tank wall. This, in turn, increases its reliability in terms of sealing and reduces the risk of failure under high pressures and temperature gradients due to its increased fatigue life. The longitudinal and transverse corrugations of the invention, which extend toward the inner surface of the tank, provide sufficient flexibility for the wall structure to accommodate thermal deformations under loads, particularly those caused by thermal compression and tension.

[0075] Furthermore, the primary membrane manufacturing process is also accelerated and simplified by simplifying or eliminating the design of the "intersection" node between the corrugations. The absence of additional stiffeners reduces the time it takes to manufacture a sealed membrane, but due to the staggered arrangement of the corrugation breaks, the strength and elastic deformation characteristics are not compromised.

[0076] The production of corrugations with a semicircular cross-section and identical radii of curvature allows the production of membrane sheets for a sealed tank wall using the cold stamping method in just one technological operation, since in the proposed design the corrugations do not intersect, and the membrane sheets do not contain sharp corners or abrupt transitions.

[0077] The wavy corrugations are convex relative to the main plane of the sealed sheet, but this does not exclude the presence of concave or other areas in certain places on their surface.

Claims

Invention formula 1. A membrane tank wall, the inner surface of which is in direct contact with a low-temperature fluid medium, made of a flexible material, which contains a first set of wave-shaped corrugations parallel to each other and a second set of wave-shaped corrugations parallel to each other, wherein the corrugations of the first set have a direction perpendicular to the direction of the corrugations of the second set with the formation of intersection points, wherein at said intersection points one of the two intersecting corrugations is made interrupted, with the formation on both sides of the transverse corrugation of symmetrical smooth roundings (6.5), turning into flat sections (4) adjacent to the transverse corrugations, wherein the size of the flat section (4), representing the distance between the base of the rounded end of the corrugation and the base of the lateral part of the corrugation perpendicular to it, is from 10 to 50 mm,the radius of curvature (3) of the rounding of the corrugation at its base from the side surface is from 10 to 30 mm, the radius of curvature (5) of the rounding of the corrugation at its base from the end surface facing the adjacent corrugation at the point of their intersection is from 60 to 80 mm, the height (8) of the corrugation is from 30 to 60 mm, the ratio of the radius of curvature (6) of the rounding of the corrugation at its apex from the end inner surface to the radius of curvature (5) of the rounding of the corrugation at its base from the end outer surface is equal to 2.5±5%, the ratio of the distance (7) from the point of intersection of the flat surface with the end of the corrugation to the middle of the cross-section of the corrugation perpendicular to it to the distance (4) from the point of intersection of the flat surface with the end of the corrugation to the point of intersection of the flat surface with the side surface of the corrugation perpendicular to it is equal to 3.2 ±5%, while the interruptions of the corrugations of different directions are performed alternating in a checkerboard pattern.

2. A wall according to item 1, in which the radius of curvature (1) of the section of the corrugation adjacent to its top is from 8 to 28 mm, and the radius of curvature (2) of the transition between this section of the corrugation and the rounding (3) at the base of the corrugation may be the same relative to the axis of symmetry of the corrugation and is from 45 to 65 mm.

3. A wall according to claim 1, in which the wall is formed from a plurality of sheets joined in an overlapping manner, wherein each sheet has molded projections on at least two of its side faces, serving for the entry of adjacent sheets and extending along the entire length of the side face of the sheet, including the surface of the corrugations.

4. The wall according to claim 1, wherein the corrugations have a substantially semicircular cross-section.

5. A wall according to any of paragraphs 1-4, in which all corrugations have the same shape and dimensions in length, width, height and radius of curvature.

6. A wall according to any of paragraphs 1-5, in which the corrugations of the first set and the corrugations of the second set are located at the same distance from each other.

7. A wall according to item 6, in which the distance between the corrugations of the first set is equal to the distance between the corrugations of the second set.

8. A wall according to any of paragraphs 1-7, in which the corrugations extend from one edge to the other edge of the plate.

9. A wall according to any of paragraphs 1-8, in which each corrugation is located at the intersection points exactly in the middle between the smooth rounding of the corrugation of the transverse direction.

10. A wall according to any of paragraphs 1-9, which is made of stainless steel. I. A wall according to any of paragraphs. 1-10, in which the corrugations are formed by a cold stamping method.

12. A wall according to any of paragraphs 1-11, consisting of a plurality of sheets connected to each other by welding to completely seal the wall.

13. A sealed and thermally insulated tank for storing and / or transporting a low-temperature fluid medium, in which the supporting wall of the tank has a multilayer structure containing sequentially arranged: a main sealed barrier consisting of a wall according to claim 1, which is in direct contact with the low-temperature fluid medium, a main thermal insulation barrier, an auxiliary sealing membrane and an auxiliary thermal insulation barrier, wherein the auxiliary thermal insulation barrier, the auxiliary sealing membrane and the main thermal insulation barrier essentially consist of a set of prefabricated panels fixed on the said supporting wall of the tank, The supporting wall of the tank contains thermal insulation blocks that support the main sealed barrier.

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