Segmented assembly method for double-lug storage tank of LNG transport ship

Abstract

The invention discloses a sectional assembly method for a double-lug storage tank of an LNG transport ship. The sectional assembly method comprises the following steps that S1, a tank body is divided into two sections, and storage tank sections are manufactured; s2, a temporary saddle and an air bag are installed in the cabin, so that two supporting parts are formed in the cabin; s3, the two storage tank sections are hoisted to the two supporting parts correspondingly for preliminary butt joint; s4, the inflation state of the air bag is controlled so that accurate butt joint of the storage tank sections can be conducted; s5, after precise butt joint is completed, the two storage tank sections are welded, and a tank body is obtained; and S6, the inflation state of the air bag is controlled to disassemble the temporary saddle and connect the tank body with the storage tank permanent support, and then installation of the double-lug storage tank is completed. And the air bag and the temporary saddle are assembled and butted, so that the double-lug storage tank can be accurately assembled in a cabin by folding weld joints and the whole storage tank can be stably positioned without ultra-large hoisting equipment while the construction operation of the ultra-large hoisting equipment is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of LNG carrier storage tank manufacturing, and in particular to a segmented assembly method of a binaural storage tank of an LNG carrier. Background Art

[0002] LNG (liquefied natural gas) carriers are a major industry in the LNG industry chain. They play the role of "super refrigerated trucks" for transporting LNG at sea and have become the main mode of ocean-going natural gas transportation. LNG storage tanks are the core equipment of C-type independent liquid cargo tank LNG carriers. With the surge in domestic LNG demand and transportation volume, LNG carriers and LNG storage tanks are also developing in the direction of large-scale.

[0003] The cylinder sections of C-type liquid cargo tanks of large LNG carriers include single-cylinder, double-cylinder and triple-cylinder types. The double-cylinder tank, i.e., double-ear tank, adopts a structure in which two cylinders intersect. Generally, the tank volume exceeds 20,000 m³, and its dimensions are relatively large. When the total tonnage of the tank exceeds 1,000 tons, the on-site lifting capacity is required to be high. For a small space like a cabin, the installation of double-ear tanks is difficult, and the assembly and docking method relies on lifting, and the installation accuracy is relatively low.

[0004] In the prior art, the patent with publication number CN 110356512 B discloses a liquefied natural gas shipboard double-hull storage tank and its manufacturing method, including two cylinders and a bulkhead disposed between the cylinders, the cylinder including a left head, a right head, and a first cylinder section, a second cylinder section, a third cylinder section, a fourth cylinder section and a fifth cylinder section disposed between the left head and the right head; the left head, the first cylinder section, the second cylinder section, the third cylinder section, the fourth cylinder section, the fifth cylinder section and the right head are welded and connected in sequence. However, this manufacturing method mainly installs the storage tank by hoisting, and its installation accuracy is relatively low, and it cannot effectively solve the problem of excessive tonnage of the double-ear storage tank during the installation process in the cabin.

[0005] In view of this, it is necessary to design a segmented assembly method for the double-ear storage tank of an LNG carrier to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a method for assembling a double-ear storage tank of an LNG carrier by dividing the tank body of the double-ear storage tank into two sections along the length direction of the tank body, and assembling and docking the two sections in the cabin by using air bags and temporary saddles, thereby avoiding the use of super-large lifting equipment for construction operations, and realizing the precise assembly of the welds of the double-ear storage tank in the cabin and the overall stable positioning of the storage tank without super-large lifting equipment.

[0007] To achieve the above-mentioned object of the invention, the present invention provides a segmented assembly method of a binaural storage tank of an LNG carrier, comprising the following steps: S1. Divide the tank into two sections along the length direction of the tank, and complete the production of each tank section through multiple shell plates; S2. Install at least two temporary saddles and at least four air bags in the cabin according to the installation position of the binaural storage tank, so that two supporting parts are formed in the cabin; S3, hoist the two storage tank sections onto the two supporting parts respectively to carry out preliminary docking of the closed sections; S4, controlling the inflation state of the airbag to adjust the relative positions of the two tank segments to achieve precise docking; S5. After precise docking, the two storage tanks are welded in sections to obtain the tank body; S6. Control the inflation state of the airbag to dismantle the temporary saddle and connect the tank body to the permanent support of the storage tank, thus completing the installation of the double-ear storage tank.

[0008] As a further improvement of the present invention, the temporary saddle height is greater than or equal to the permanent support height of the storage tank.

[0009] As a further improvement of the present invention, the maximum lifting height of the airbag in the inflated state is greater than the temporary saddle height.

[0010] As a further improvement of the present invention, the support portion includes at least one temporary saddle and at least two air bags.

[0011] As a further improvement of the present invention, the support portion further includes a permanent support for the storage tank.

[0012] As a further improvement of the present invention, the segmentation position is located in the middle of the tank body.

[0013] As a further improvement of the present invention, in step S4, the radial relative positions of the two tank segments are adjusted by controlling the inflation state of the airbag, and the airbag acts as a rolling fulcrum to adjust the axial relative positions of the two tank segments to achieve precise docking of the two tank segments.

[0014] As a further improvement of the present invention, in step S5, the welding operation includes welding the closed annular seams and the bulkhead plates of the two tank segments.

[0015] As a further improvement of the present invention, in step S6, when the airbag inflation state is controlled so that the airbag lifting height is greater than the temporary saddle height, the temporary saddle is dismantled; when the airbag inflation state is controlled so that the airbag lifting height is lower than the permanent support height, the tank body falls on the permanent support of the tank, and the tank body is connected to the permanent support of the tank.

[0016] As a further improvement of the present invention, a pressure test is performed after the installation of the binaural storage tank is completed.

[0017] The beneficial effects of the present invention are: 1. The present invention divides the double-ear storage tank into two sections along the length direction of the tank body, and uses air bags and temporary saddles for assembly and docking, which significantly reduces the requirements of large-scale LNG carrier double-ear storage tanks on lifting equipment and solves the problem of assembly welding and overall positioning of large-scale LNG carrier double-ear storage tanks without super-large lifting equipment.

[0018] 2. The present invention utilizes the elasticity and flexibility of the airbag itself. During the assembly and docking process, by adjusting the pressure and position of the airbag, stable and flexible support for the tank body can be achieved, avoiding damage to the storage tank by a single pressure point. At the same time, it can also provide a rolling fulcrum and cooperate with a temporary saddle to achieve precise adjustment of the segmented closed annular seam to ensure the installation accuracy of the storage tank.

[0019] 3. The present invention uses lifting equipment to hoist two storage tank sections onto a temporary saddle for preliminary docking, and uses air bags in conjunction with the temporary saddle to accurately dock the two storage tank sections. After the tank body is welded, the air bag is used to lift the tank body to dismantle the temporary saddle, thus avoiding the use of super-large lifting equipment for construction operations. The present invention has the advantages of convenient construction, low equipment investment cost, good economy, safety and reliability, and stable quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flow chart of a method for assembling a double-ear tank of an LNG carrier in sections.

[0021] Figure 2 The construction flow chart of the segmented assembly method of the double-ear storage tank of the LNG carrier.

[0022] Figure 3 This is a schematic diagram of the bottom distribution when installing a double-ear storage tank.

[0023] Figure 4 This is a schematic diagram of the segmentation, segmentation and weld layout of a double-ear storage tank.

[0024] Reference numerals 10. Cabin; 20. Permanent support for storage tank; 30. Temporary saddle; 40. Air bag; 51. First storage tank section; 52. Second storage tank section. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0027] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0028] like Figure 1 and Figure 2 As shown, the present invention provides a segmented assembly method for a binaural storage tank of an LNG carrier, comprising the following steps: S1. Tank segmentation and production: The tank body is divided into two sections along the length direction of the tank body, and each tank segment is produced through multiple shell plates; S2, temporary saddle 30 and airbag 40 installation in the cabin 10: at least two temporary saddles 30 and at least four airbags 40 are installed in the cabin 10 according to the installation position of the binaural storage tank, so that two support parts are formed in the cabin 10; S3. Preliminary docking of tank sections: hoist two tank sections onto two supporting parts respectively to perform preliminary docking of the closed sections; S4. Use the airbag 40 to precisely dock the tank segments: by controlling the inflation state of the airbag 40, the radial relative positions of the two tank segments are adjusted. At the same time, the airbag 40 acts as a rolling fulcrum to adjust the axial relative positions of the two tank segments, thereby achieving precise docking of the two tank segments. S5. Tank segment welding: After precise docking, the two tanks are welded segment by segment to obtain the tank body; S6. Disassembly of the temporary saddle 30 and connection of the tank body with the permanent support 20 of the storage tank: Control the inflation state of the airbag 40 to disassemble the temporary saddle 30 and connect the tank body with the permanent support 20 of the storage tank, thereby completing the installation of the binaural storage tank.

[0029] Specifically, in step S1, regarding the number of segments, the tank body is divided into two segments along the length direction, taking into account the lifting capacity of the cabin 10 on site and the subsequent docking accuracy and efficiency issues. Compared with the conventional method of first completing a single cylinder and then docking the sides of the two cylinders, the segmentation method of the present invention, i.e., segmentation along the length direction of the tank body, can reduce the interference of the bulkhead on the docking of the tank segments, thereby facilitating the subsequent position adjustment using the airbag 40 and the temporary saddle 30 to ensure installation accuracy.

[0030] Considering the difficulty of subsequent docking and assembly, the weight of the two tank sections should be kept as consistent as possible. For example, the section position is located in the middle of the tank body. After the section is completed, each tank section is divided into pieces and welded.

[0031] The steps for making tank segments are as follows: a. Manufacturing shell plates for double-ear storage tanks: Calculate the shell plate size according to the set segmentation, slicing and weld layout method, cut and process the shell plates; b. Assemble and weld into a single cylinder section or head segment: Assemble the manufactured shell plate segments into a single cylinder section and head, and then complete the welding of the single cylinder section and head weld; c. Welding into process sections of double-ear storage tanks: single cylinder sections or heads are assembled into process sections in the vertical direction, and then the welds within the process sections are welded; d. Welding into large closed sections of double-ear storage tanks: The process sections are assembled into two large closed sections, i.e. two storage tank sections, in the vertical direction, and then the circumferential seam welding is completed in the closed sections; e. Nondestructive testing of welds: nondestructive testing and repair of welds in tank sections; f. Rust removal and painting of the outer surface of the tank sections: Rust removal and anti-corrosion painting shall be carried out on the outer surface of the tank sections. No anti-corrosion painting shall be carried out within 200mm on both sides of the closed annular seam along the length direction of the tank body.

[0032] Specifically, in step S2, a temporary saddle 30 is installed inside the cabin 10 according to the centerline position of the binaural storage tank; the support portion includes at least one temporary saddle 30 and at least two air bags 40; the support portion also includes a permanent support 20 for the storage tank; for example, Figure 2 and Figure 3 As shown, the permanent supports 20 of the storage tanks are arranged at intervals in the cabin 10, and two temporary saddles 30 are arranged on both sides of each permanent support 20 of the storage tanks, two air bags 40 are arranged at intervals between the temporary saddle 30 and the permanent support 20 of the storage tanks, and one air bag 40 is arranged between two adjacent temporary saddles 30, so that the two temporary saddles 30, one permanent support 20 of the storage tank, the two air bags 40 between the temporary saddle 30 and the permanent support 20 of the storage tank, and the air bag 40 between the two temporary saddles 30 together form a support part to support the storage tank sections. The airbag 40 between the two temporary saddles 30 provides support for the docking surfaces of the two tank segments, that is, during subsequent lifting, the docking surfaces of the two tank segments all fall on the airbag 40 between the two temporary saddles 30, and the airbag 40 between the two adjacent temporary saddles 30 is mainly used for lifting and positioning the entire tank body, and does not participate in the position adjustment of the tank segments during the precise docking process; in addition, in order to meet the needs of precise docking regulation, each tank segment needs to have at least two airbags 40 for docking adjustment, that is, at least four airbags 40 are installed in the cabin 10.

[0033] Since the double-ear storage tank has large dimensions and thin walls, it is difficult to adjust the entire tank. By hoisting the tank in sections into the cabin 10 and placing it on a temporary saddle 30, combined with the regulation of the airbag 40, damage to the tank body during the docking adjustment process can be avoided. At the same time, the accuracy of the closed annular seam assembly and the straightness of the tank body can be ensured. Compared with the hoisting adjustment, the adjustment method of the airbag 40 is safer and more convenient and stable.

[0034] The height of the temporary saddle 30 is greater than or equal to the height of the permanent support 20 of the storage tank, and the maximum lifting height of the airbag 40 in the inflated state is greater than the height of the temporary saddle 30. Exemplarily, the height of the temporary saddle 30 is equal to the height of the permanent support 20 of the storage tank.

[0035] Specifically, in step S3, during the preliminary docking, the two tank segments are hoisted onto the support part using a lifting device, and the rough alignment and closing of the closing segments are performed. During the rough alignment, the tank segments are supported by the temporary saddle 30 and the permanent tank support 20.

[0036] Specifically, in step S4, when precise docking is performed, the airbag 40 is inflated to raise the support point of the airbag 40, and the flexible support and rolling fulcrum of the airbag 40 are used to adjust the straightness and relative position of the two tank segments, and the gap and misalignment of the closing weld group are precisely adjusted. After passing the test, the closing weld is spot welded and fixed, and the airbag 40 is deflated so that the tank segments are located on the temporary saddle 30 and the permanent tank support 20.

[0037] Specifically, in step S5, the welding operation includes welding the closed annular seams and the bulkhead plates of the two storage tank segments. After the welding is completed, non-destructive testing of the closed annular seams is performed.

[0038] Specifically, in step S6, by controlling the inflation state of the airbag 40 so that the lifting height of the airbag 40 is greater than the height of the temporary saddle 30, the tank body leaves the temporary saddle 30 and the temporary saddle 30 is disassembled; by controlling the inflation state of the airbag 40 so that the lifting height of the airbag 40 is lower than the height of the permanent support 20 of the tank, the tank body falls on the permanent support 20 of the tank, and the tank body and the permanent support 20 of the tank are welded.

[0039] The airbag 40 is used for accurate docking of the storage tank segments and is also used for the design of disassembly and regulation of the temporary saddle 30, which can quickly, safely, smoothly and efficiently complete the assembly of the binaural storage tank.

[0040] Specifically, after the installation of the binaural storage tank is completed, a gas-liquid combined pressure test is performed inside the cabin 10, and stress monitoring is performed during the pressure test. Finally, the insulation layer is installed and constructed on the outer surface of the binaural storage tank.

[0041] Specifically, the airbag 40 is a marine airbag.

[0042] The segmented assembly method of the binaural storage tank for an LNG carrier provided by the present invention is described below in conjunction with specific embodiments.

[0043] Example 1 A large LNG carrier double-ear storage tank, which is installed in the cabin 10 and fixedly connected to the hull through two permanent tank supports 20 inside the cabin 10. The double-ear storage tank is designed and constructed in accordance with the specifications for the construction and equipment of ships carrying liquefied gas in bulk and the IGC Code, and the storage medium is liquefied natural gas. The minimum design temperature is -163℃, the design pressure is 0.531MPa, the geometric volume is 20603m³, the shell material is SA553TypeⅢ, the cylinder wall thickness is 26~27mm, the spherical head wall thickness is 20mm, the total length is 40000mm, and the total weight is 1076.6 tons.

[0044] The steps for assembling the two-ear storage tank in sections are as follows: (1) Setting tank segments like Figure 4 As shown, according to the length, diameter, weight and other parameters of the double-ear storage tank, combined with the consideration of transportation and lifting capacity, the double-ear storage tank is divided into two sections along the length direction of the tank body, namely the first storage tank section 51 and the second storage tank section 52, and each storage tank section does not exceed 600 tons.

[0045] According to the length, diameter and weight parameters of the tank segments, combined with the consideration of steel plate rolling, shell plate processing and manufacturing, transportation and hoisting capacity, a comprehensive analysis is conducted to set the segmentation form and weld layout of the tank shell plate. The tank cylinder is divided into 6 segments and arranged symmetrically along the axis.

[0046] (2) Manufacture storage tanks in sections a. Calculate the size of the tank shell plate according to the set segmentation and weld layout method, and cut and process the shell plate; b. Assemble the manufactured tank shell plates into a first tank segment 51 and a second tank segment 52, and complete the welding of the longitudinal seams and circumferential seams of the two tank segments in accordance with the design technical requirements; c. Carry out non-destructive testing and repair of the welds in the two tank sections according to the design technical requirements; d. According to the design technical requirements, the outer surfaces of the two tank sections shall be rust-removed and anti-corrosion coated respectively. The anti-corrosion coating shall not be applied within 200mm from the center line of the weld of the butt joint of the first tank section 51 and the second tank section 52; (3) Tank segment welding Use the lifting equipment to hoist the storage tank sections onto the support installed inside the cabin 10, perform rough alignment and closing of the storage tank closing sections, and then accurately adjust the closing weld assembly gap and misalignment by controlling the state of the airbag 40. After passing the test, perform spot welding and fixation of the closing weld. The airbag 40 deflates the storage tank sections and locates them on the temporary saddle 30 and the permanent support 20 of the storage tank. The welding of the closed annular seam and the bulkhead is completed in the cabin 10, so that the two storage tanks are segmented into a complete tank body, and after the welding is completed, the non-destructive testing of the closed annular seam is performed.

[0047] (4) Removal of temporary saddle 30 and connection of permanent support 20 for storage tank By controlling the lifting height of the airbag 40 to be higher than the height of the temporary saddle 30, the tank body is separated from the temporary saddle 30 and the temporary saddle 30 is removed; by controlling the inflation state of the airbag 40 to make the lifting height of the airbag 40 lower than the height of the permanent support 20 of the tank, the tank body falls on the permanent support 20 of the tank, and the tank body and the permanent support 20 of the tank are connected, thus completing the installation of the double-ear tank.

[0048] Finally, the double-ear storage tank is subjected to pressure resistance test and insulation layer construction.

[0049] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A segmented assembly method for a binaural storage tank of an LNG carrier, characterized in that: The following steps are involved: S1. Divide the tank into two sections along the length direction of the tank, and complete the production of each tank section through multiple shell plates; S2. Install at least two temporary saddles and at least four air bags in the cabin according to the installation position of the binaural storage tank, so that two supporting parts are formed in the cabin; S3, hoist the two storage tank sections onto the two supporting parts respectively to carry out preliminary docking of the closed sections; S4, controlling the inflation state of the airbag to adjust the relative positions of the two tank segments to achieve precise docking; S5. After precise docking, the two storage tanks are welded in sections to obtain the tank body; S6. Control the inflation state of the airbag to dismantle the temporary saddle and connect the tank body to the permanent support of the storage tank, thus completing the installation of the double-ear storage tank.

2. The segmented assembly method of the binaural storage tank of an LNG carrier according to claim 1 is characterized in that: The temporary saddle height is greater than or equal to the permanent support height of the storage tank.

3. The segmented assembly method of the binaural storage tank of an LNG carrier according to claim 2 is characterized in that: The maximum lifting height of the airbag in the inflated state is greater than the temporary saddle height.

4. The segmented assembly method of the binaural storage tank of an LNG carrier according to claim 1 is characterized in that: The support portion includes at least one temporary saddle and at least two air bags.

5. The segmented assembly method of the binaural storage tank of the LNG carrier according to claim 4 is characterized in that: The support portion also includes a permanent support for the tank.

6. The segmented assembly method of the binaural storage tank of an LNG carrier according to claim 1, characterized in that: The segmentation position is located in the middle of the tank.

7. The segmented assembly method of the binaural storage tank for an LNG carrier according to claim 1, characterized in that: In step S4, the radial relative positions of the two tank segments are adjusted by controlling the inflation state of the airbag, and the airbag acts as a rolling fulcrum to adjust the axial relative positions of the two tank segments to achieve precise docking of the two tank segments.

8. The segmented assembly method of the binaural storage tank of an LNG carrier according to claim 1, characterized in that: In step S5, the welding operation includes welding the closed annular seams and the bulkhead plates of the two tank segments.

9. The segmented assembly method of the binaural storage tank of an LNG carrier according to claim 1, characterized in that: In step S6, when the airbag inflation state is controlled so that the airbag lifting height is greater than the temporary saddle height, the temporary saddle is removed; when the airbag inflation state is controlled so that the airbag lifting height is lower than the permanent support height, the tank body falls on the permanent tank support, and the tank body and the permanent tank support are connected.

10. The segmented assembly method of the binaural storage tank of an LNG carrier according to claim 1, characterized in that: After the installation of the double-ear storage tank is completed, a pressure test is carried out.

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