Method for applying insulation to a composite cylindrical tank, composite cylindrical tank and use thereof

Abstract

The invention relates to a method of applying a thermal insulation to a composite cylindrical tank for storing liquefied gas. One or more layers of polymeric foam (2) are sprayed onto the outer surface of the tank shell (1). On top of certain layers of polymeric foam (2) a crack barrier (4) is installed, wherein the crack barrier (4) is anchored to the outer surface of the tank shell (1). The invention also relates to a related composite cylindrical tank for storing liquefied gas, and the use of such a composite cylindrical tank for storing and / or transporting liquefied gas.

Description

Technical Field

[0001] This invention relates to tanks for storing and transporting liquefied gases, such as those used in marine facilities. More particularly, this invention relates to a novel method for applying insulation to assembled cylindrical tanks. Background Technology

[0002] Liquefied gases are typically stored at low to very low temperatures, close to their boiling points, to avoid high pressures during storage. Therefore, storage tanks with advanced insulation are required to keep the gases contained within cold and liquid. A common type of tank for storing liquefied gases is the cylindrical tank, which consists of a single cylindrical segment or blade, such as the International Maritime Organization (IMO) Independent Type C tank. These single-blade cylindrical tanks comply with the IMO Code on Structures and Equipment of Ships Transporting Liquefied Gases (IGC Code).

[0003] Cylindrical tanks are particularly well-suited to withstand pressurized conditions because their cylindrical shape generates very little stress concentration within the tank structure. Therefore, the increased peak pressure stress is more manageable for cylindrical tanks compared to tanks with transverse cross-sections that include sharper corners.

[0004] On the other hand, single-lobed cylindrical tanks typically offer poor volume utilization in the tank space or the holding space where the tank is placed. This is particularly important for marine facilities, which often have holding spaces with rectangular cross-sections.

[0005] For rectangular holding spaces, one solution is to combine two or more cylindrical tank sections. Thus, the combined cylindrical tank comprises two or more cylindrical tank sections connected longitudinally, for example, by welding. Compared to a single cylindrical tank, this solution increases the volume utilization within the holding space having a rectangular cross-section.

[0006] The most common type of combined cylindrical tank is the bivalve tank. The transverse cross-section of a bivalve tank comprises two connected cylindrical sections and is typically of a binocular form, with strong bulkheads connecting the two cylindrical sections. The strong bulkheads can be welded to the two cylindrical sections along their longitudinal direction. When placed within a rectangular retaining space volume, bivalve tanks offer higher volumetric efficiency than single-lobed cylindrical tanks. At the same time, the strength benefits of the cylindrical shape are largely maintained.

[0007] Optionally, three or more cylindrical sections can be connected in the same manner as a bilobed tank, for example, by welding. Strong bulkheads for connection are placed between every two adjacent cylindrical sections and can also be used to store liquefied gases. A trilobed tank comprises three connected cylindrical sections in its transverse cross-section, while a multilobed tank comprises more than three connected cylindrical sections in its transverse cross-section.

[0008] For insulation purposes, it is well known that polymer foam, such as polyurethane (PU) foam, is applied directly to the outer surface of a tank by spraying. Polymer foam typically comprises two main components: a premixed polyol and isocyanate (P-MDI) in the case of PU foam. During application, the main components are mixed to form a polymer foam precursor, which is then dispensed from a spray gun and sprayed onto the exterior of the tank shell. Upon application, the sprayed polymer foam expands and subsequently cures, forming an insulating layer. Sprayed polymer foam is typically applied in several layers, ranging from 10 to 35 mm in thickness, to the exterior of the tank shell to achieve the desired total insulation layer thickness.

[0009] The application of polymer spray foam, which is sprayed directly onto the exterior of the can shell, is primarily used on single-lobed cylindrical cans. Once applied to the can, the polymer spray foam remains in position on the outer surface of the can shell solely through adhesion between the polymer spray foam and the outer surface of the can shell. This adhesion occurs during the curing process of the polymer foam on the can. Therefore, the adhesive strength is limited by the tensile strength within the foam.

[0010] Compared to single-lobed cans, combined cylindrical cans of two, three, or more lobes present challenges for the robust adhesion of polymer-sprayed foam insulation. The cross-sectional geometry of these combined cylindrical cans in the connection areas between the individual cylindrical can sections is complex. Consequently, highly concentrated thermal stresses occur within the polymer-sprayed foam insulation mass in the connection areas during can temperature variations. Problems arise due to thermal shrinkage and stress in the multidirectional surfaces at the joints between the strong bulkhead and the individual cylindrical can sections. These stresses occur during can cooling and preheating and increase the risk of delamination between the sprayed foam and the outer surface of the can shell. Specifically, the thermal shrinkage of the can material differs from that of the foam insulation material. Furthermore, the foam material undergoes varying shrinkage across its entire thickness due to temperature gradients from its cold side (near the can shell) to its hot side on its outer surface. The combination of these geometrically induced differences in thermal shrinkage results in multidirectional stresses within the foam, which can lead to delamination between the foam and the can shell surface. These effects are more pronounced with higher temperature gradients involved, and the colder the liquefied gas contained in the can, the more pronounced these effects become.

[0011] Due to these issues, for cylindrical tanks with double, triple, or multi-lobed configurations, the standard practice is to use mechanically fixed insulation panels instead of sprayed foam. However, the manufacture of mechanically fixed insulation panels is time-consuming and expensive. Furthermore, mechanically fixed panels require more manpower, thus increasing application costs.

[0012] Therefore, there is a clear need for improved insulation arrangements for combined cylindrical tanks, as well as improved methods for applying insulation to combined cylindrical tanks.

[0013] WO2020050515 A1 discloses multiple sandwich panels, including a first insulation panel and a second insulation panel fixed to the wall structure of a tank. WO2018029613 A1 discloses a cryogenic insulation system for ocean-going vessels, involving the steps of sequentially applying multiple layers to the outer surface of a tank. US2017101163A1 discloses a cryogenic barrier for marine vessels formed by multiple individual panels. Summary of the Invention

[0014] This invention relates to a method for applying insulation to a combined cylindrical tank for storing liquefied gas. The method includes providing a combined cylindrical tank comprising a tank shell, spraying one or more layers of polymer foam onto the outer surface of the tank shell, and installing a crack barrier on top of some of the polymer foam layers, wherein the crack barrier is anchored to the outer surface of the tank shell.

[0015] The present invention also relates to a combined cylindrical tank for storing liquefied gas. The combined cylindrical tank includes a tank shell and one or more layers of polymer-sprayed foam covering the outer surface of the tank shell, and one or more crack barriers mounted on top of certain layers of polymer-sprayed foam and anchored to the outer surface of the tank shell.

[0016] Finally, the present invention also relates to the use of the combined cylindrical tank according to the invention for storing and / or transporting liquefied gases, such as liquefied natural gas, liquefied petroleum gas, liquefied ethane gas or liquefied ethylene gas.

[0017] The method according to the invention for applying insulation to a combined cylindrical tank and a corresponding insulated combined cylindrical tank can be applied to the storage and transportation of liquefied gases, such as liquefied petroleum gas (LPG), liquefied ethane and / or ethylene gas, liquefied natural gas (LNG) or other cryogenic liquefied gases. Attached Figure Description

[0018] Figure 1 This is a schematic cross-section of the connection area of ​​the combined cylindrical tank, which includes studs for anchoring the foam insulation material as described herein.

[0019] Figure 2a It is a schematic cross-section of the stud structure based on the first construction.

[0020] Figure 2b It is a schematic cross-section of the stud construction based on the alternative construction.

[0021] Figure 2c It is a schematic cross-section of a stud construction based on an alternative construction. Detailed Implementation

[0022] Figure 1A schematic cross-sectional view of a portion of the tank shell 1 in the connection area of ​​the combined cylindrical tank is shown. The combined cylindrical tank is suitable for the transport and storage of liquefied gases, preferably an IMO freestanding C tank. The combined cylindrical tank can be a bivalve, trivalve, or multivalve type tank. In each case, the laterally adjacent cylindrical portions are connected by a strong bulkhead positioned between them. This strong bulkhead can be welded to the adjacent cylindrical portions in its longitudinal direction.

[0023] One or more layers of polymer spray foam 2 are adhered to the exterior of the tank shell 1, thereby forming insulation on the tank shell 1, wherein each layer of polymer spray foam 2 may consist of several sublayers. Preferably, the polymer spray foam 2 comprises polyurethane (PU) foam. The polymer spray foam 2 may optionally contain additives, such as reinforcing fibers, expansion additives, antimicrobial or antifungal agents, or volumetric fillers.

[0024] The stud 3 extends from the connection area of ​​the cylindrical portion of the assembled cylindrical can. Preferably, the stud 3 extends partially into the surface of the can shell in the normal direction. The stud 3 is preferably threaded. Preferably, the stud 3 is welded to the can shell 1.

[0025] One or more crack barriers 4 are attached to studs 3 and extend laterally along certain layers of the polymer spray foam 2. Crack barriers 4 may be in the form of a mesh or perforated sheet. Crack barriers 4 may comprise plastic, fiberglass, metal, or composite materials. Crack barriers 4 may be placed at equal intervals along the studs 3. Alternatively, crack barriers 4 may be placed at intervals of varying lengths along the studs 3, see [reference needed]. Figure 1 In the latter case, different numbers of polymer sprayed foam layers can exist between different pairs of crack barriers. Optionally, each layer of polymer sprayed foam 2 may include different numbers of sublayers, thereby achieving different thicknesses. The sublayers are used... Figure 2a The stripes in the figure indicate that the same reference numerals represent the same features. Figure 2a A schematic cross-sectional view of the can shell 1, the polymer spray foam layer 2, and the cover layer 7 is shown.

[0026] The retaining rod 6, washer, and nut 5 secure one or more crack barriers 4 to the stud 3. The retaining rod 6 can be made of a sufficiently strong material, such as metal, reinforced plastic, plywood, composite material, or any other suitable strength support material. Advantageously, the retaining rod 6 is configured such that the fixing force is effectively transferred from the stud bolt 3 to the crack barrier 4.

[0027] Each crack barrier 4 locally secures the underlying layer of the polymer spray foam 2 to the tank shell. Thus, moving outward from the tank shell along the studs 3, each or more layers of the polymer spray foam 2 are locally secured in place by the crack barriers 4. Consequently, the crack barriers 4 and the retaining rods 6 secure the polymer spray foam layers to the tank, preventing the polymer spray foam 2 from loosening from the tank shell surface and preventing delamination of the insulation material.

[0028] During application, one or more layers of polymer spray foam 2 are applied to the exterior of the tank housing 1, wherein each layer of polymer spray foam 2 may include one or more sublayers. After applying one or more layers of polymer spray foam 2, a crack barrier 4 is installed. This process is then repeated until the desired number of layers of polymer spray foam 2 are obtained. Each layer of polymer spray foam 2 applied directly on top of the crack barrier 4 is mechanically and chemically anchored to the crack barrier 4 and the underlying layer of polymer spray foam 2. Mechanical anchoring occurs as the overlying foam layer expands into the gaps in the mesh or perforated plate forming the crack barrier 4. Chemical anchoring occurs as the overlying foam layer bonds with the underlying foam layer located below the crack barrier 4 through the gaps in the crack barrier 4. Thus, each crack barrier 4 located between the layers of polymer spray foam 2 is firmly embedded in the polymer spray foam 2.

[0029] Mechanical protective material covers the exterior of the polymer spray foam 2, thereby forming the outer surface of the can and a barrier against the surrounding environment. The mechanical protective material is preferably a cover layer 7, and preferably comprises a metallic material. Preferably, the cover layer 7 is configured to be waterproof. The cover layer 7 can be secured to the stud 3 at appropriate locations using a fixing rod 6, a washer, and a nut 5, see [link to documentation]. Figure 1 .

[0030] Advantageously, the crack barrier holds the polymer sprayed foam layer in place and prevents delamination due to thermal stress within the foam. Additionally, the crack barrier advantageously removes some weight from the capping layer.

[0031] exist Figure 2b and 2c Alternative configurations are shown in the figure, where the same reference numerals denote the same as... Figure 1 and 2a The same characteristics. For ease of understanding, in Figure 2b and 2c Sublayers are not shown. According to... Figure 2b As shown in one alternative configuration, the cover layer 7 is not fixed to the stud 3.

[0032] Advantageously, thermal fracture is thus formed between the stud and the outer surface formed by the covering layer. This reduces thermal stress and further reduces the risk of insulation material delamination.

[0033] According to another alternative configuration, such as Figure 2c As shown, the thermal breakage element 8 is formed as an integral part of the stud 3. The thermal breakage element 8 is preferably positioned between the two crack barriers 4. Advantageously, the thermal breakage element divides the stud into two parts, thereby generating thermal breakage within the stud itself and reducing thermal stress. Therefore, the risk of delamination of the insulation is further reduced.

[0034] The following describes a method according to the invention for applying insulation to a combined cylindrical tank.

[0035] Provided as previously combined Figure 1 The assembled cylindrical can. The assembled cylindrical can includes a can shell 1 provided with studs 3. The studs 3 are positioned along the longitudinal connection area between the cylindrical can portions. One or more crack barriers 4 can be attached to the studs 3 by means of retaining rods 6, washers, and nuts 5, as described above. Figure 1 As shown.

[0036] Polymer spray foam 2 is sprayed onto the outer surface of the can housing 1 in separate layers. The polymer foam precursor is dispensed from a spray gun, which can be manually or robotically operated. Each pass of the spray gun forms a sub-layer of polymer spray foam 2. One or more sub-layers form a single layer of polymer spray foam 2. Upon application to the can housing 1, the polymer foam precursor expands and adheres to the outer surface of the can housing 1. Optionally, the polymer spray foam 2 may cure upon expansion. A crack barrier 4 is then mounted on studs 3 to partially cover the layer of polymer spray foam 2. After the crack barrier 4 is mounted, subsequent layers of polymer spray foam 2 are applied, upon which further crack barriers 4 are applied. These subsequent layers of polymer spray foam 2 adhere to the underlying layer of polymer spray foam 2. This process continues until the desired number of polymer spray foam layers are achieved. For the outermost layer of polymer spray foam 2, crack barriers 4 may or may not be applied. Once completed, the sprayed, expanded, and possibly cured polymer spray foam 2 forms an insulating layer surrounding the can housing 1.

[0037] During the spraying and expansion of each subsequent layer of polymer spray foam 2, the polymer foam precursor penetrates and expands through the gaps in the grid or perforated plate forming the crack barrier 4. Thus, each subsequent foam layer is mechanically anchored to the crack barrier 4 to which it is applied. Additionally, the polymer foam precursor chemically bonds to the previous layer of polymer spray foam through the gaps in the crack barrier 4 during expansion. Through mechanical and chemical anchoring, polymer spray foam 2 becomes firmly attached to the crack barrier 4, thereby preventing delamination due to thermal stress within the foam.

[0038] After completing the application of polymer spray foam 2, mechanical protective materials can be provided, such as those described above. Figure 1 The aforementioned cover layer 7 is used to cover the polymer sprayed foam insulation. For example... Figure 2a As shown, the cover layer 7 can be directly attached to the stud 3. Optionally, as... Figure 2c As shown in the alternative configuration, the stud 3 may be provided with a thermal break element 8.

[0039] Alternatively, the capping layer can remain unfixed to stud 3, thereby creating thermal fracture, such as Figure 2b As shown in the alternative configuration.

[0040] Advantageously, the method of the present invention provides convenience in the insulation process of polymer spray foam cans and associated reductions in labor and costs, while preventing the risk of insulation delamination that is typically associated with spray foam insulation on assembled cylindrical cans.

[0041] In use, the combined cylindrical tank according to the invention can be used to store and / or transport liquefied gases. Therefore, the combined cylindrical tank can be installed in the holding space of marine structures such as LNG or LPG carriers.

[0042] The coldest liquefied gas currently stored in combined cylindrical tanks is LNG. Advantageously, the present invention allows for the use of combined cylindrical tanks insulated with polymer spray foam insulation for LNG and even colder liquefied gases, while safely preventing delamination problems.

[0043] The foregoing embodiments and examples are not intended to be limiting; the scope of the invention is defined only by the appended claims.

[0044] Figure Labels

[0045] 1. Tank shell

[0046] 2 Polymer spray foam

[0047] 3 studs

[0048] 4. Crack Barrier

[0049] 5. Washers and nuts

[0050] 6. Fixing rod

[0051] 7. Covering layer

[0052] 8. Thermal breakage element

Claims

1. A method for applying insulation to a double-lobed, triple-lobed, or multi-lobed combined cylindrical tank for storing liquefied gases, the method comprising: A double-lobed, triple-lobed, or multi-lobed combined cylindrical tank is provided, the combined cylindrical tank including a tank shell (1). One or more layers of polymer foam (2) are sprayed onto the outer surface of the tank shell (1); and One or more crack barriers (4) are installed on top of one or more polymer foams (2), wherein the one or more crack barriers (4) are anchored to the outer surface of the tank shell (1) in the cylindrical portion connection area of ​​a bivalve, trivalve or multivalve combined cylindrical tank, wherein the one or more crack barriers (4) are anchored to the outer surface of the tank shell (1) by studs (3) fixed to the tank shell (1), wherein each stud (3) includes a thermally fractured element formed as an integral part of the stud (3); as well as The covering layer (7) is attached to the combined cylindrical can; The one or more crack barriers (4) are secured to the stud (3) at appropriate positions by means of a fixing rod (6), a washer, and a nut (5); and The cover layer (7) remains unconnected to the stud (3), thereby causing thermal breakage.

2. The method according to claim 1, characterized in that, Each crack barrier (4) includes a mesh or perforated plate, which may be made of plastic, fiberglass, metal or composite material.

3. The method according to any one of claims 1 to 2, characterized in that, The cover layer (7) is fixed to the stud (3) by a fixing rod (6), a washer and a nut (5).

4. A double-lobed, triple-lobed, or multi-lobed combined cylindrical tank for storing liquefied gases, wherein the double-lobed, triple-lobed, or multi-lobed combined cylindrical tank comprises: Tank shell (1); One or more layers of polymer spray foam (2) covering the outer surface of the can housing (1); One or more crack barriers (4) are mounted on top of one or more layers of polymer spray foam (2) and anchored to the outer surface of the tank housing (1) in the cylindrical portion connection area of ​​a two-, three-, or multi-lobed combined cylindrical can, wherein the one or more crack barriers (4) are anchored to the outer surface of the tank housing (1) by studs (3) fixed to the tank housing (1), wherein each stud (3) includes a thermally fractured element formed as an integral part of the stud (3); as well as Covering layer (7) covering the polymer spray foam (2); The one or more crack barriers (4) are secured to the stud (3) at appropriate positions by means of a fixing rod (6), a washer, and a nut (5); and The cover layer (7) is not connected to the stud (3), thus causing thermal breakage.

5. The combined cylindrical tank according to claim 4, characterized in that, Each crack barrier (4) includes a mesh or perforated plate, which may be made of plastic, fiberglass, metal or composite material.

6. The combined cylindrical tank according to any one of claims 4 to 5, characterized in that, The cover layer (7) is fixed to the stud (3) by a fixing rod (6), a washer and a nut (5).

7. The combined cylindrical tank according to any one of claims 4 to 5, characterized in that, The combined cylindrical tank is used for storing and / or transporting liquefied gases.

8. The combined cylindrical tank according to claim 7, characterized in that, The liquefied gas is liquefied natural gas, liquefied petroleum gas, liquefied ethane gas, or liquefied ethylene gas.

9. A marine apparatus comprising a combined cylindrical tank according to any one of claims 4 to 8.

10. The marine apparatus according to claim 9, characterized in that, The marine device is a ship.

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