A method for controlling post-weld deformation of boundary corrugated plates of a cargo containment system of an LNG carrier

Abstract

A kind of LNG transport ship cargo containment system boundary corrugated plate postwelding deformation control method, in assembly sequence, first install the corner connector of a station, then install the second corner connector of the station adjacent to the first station side, then install the third corner connector of the station adjacent to the other side of the first station.Clap on the corner part of steel corner, segmented welding is used, first complete the welding of corner part clapped on boundary corrugated plate, then complete the welding of clapped on steel corner, install corrugated knot clamp on the corrugated knot near the bulge of boundary corrugated plate and adjacent corrugated knot, assemble special pressing tool on corrugated knot clamp, by adjusting the length and height of special pressing tool, contact and extrude the end of special pressing tool to the bulge area of corrugated plate, keep the pressure of special pressing tool on bulge area before completing the welding of three types of corner parts by hand welding, realize the stress of boundary corrugated plate during dispersed welding by special pressing tool.

Description

Technical Field

[0001] This invention belongs to the field of marine shipbuilding and design, and specifically relates to a method for controlling the deformation of the boundary corrugated plate of the cargo containment system of an LNG carrier after welding. Background Technology

[0002] LNG carriers using Mark III membrane-type cargo containment system technology in the shipbuilding industry have a main shield wall of 1.2mm thick 304L stainless steel corrugated plate. Corrugated plates that overlap with steel corner pieces near the transverse corners and longitudinal corners of the hold are called boundary corrugated plates. To ensure the sealing and continuity of the boundary corrugated plate ends, corner components need to be installed at the ends of the boundary corrugated plates. The corrugated plate perimeter of the port and starboard sides of the cabin has a large number of corner components that are densely distributed. These corner components mainly include three types: corner connectors, corner joint connectors, and end seals. During on-site construction, these three types of corner components need to be installed sequentially onto the corrugated plate and its adjacent steel corner. Due to the close proximity of these three types of corner components, welding all of them onto the corrugated plate and its adjacent steel corner can easily cause post-weld deformation in the area where the corner components overlap. The corrugated plate is made of 1.2mm 304L stainless steel, which is an ultra-thin sheet with poor heat dissipation. The heat input generated during welding is concentrated, which can easily cause post-weld deformation in the area where the corrugated plate overlaps with the corner components. The visible manifestation of post-weld deformation is that the corrugated plate bulges in the area where the corner components are densely installed. If the bulge height exceeds the quality control standard, the bulging area of ​​the corrugated plate needs to be cut and repaired. Corrugated plate repair work mainly involves repairing defective products generated during the assembly and welding of corrugated plates in the cargo containment system. Repair work increases on-site production labor costs and repair material costs, directly affecting the on-site inspection progress and thus the production and construction rhythm, hindering the smooth progress of production and being detrimental to the overall production node control of the LNG carrier cargo containment system.

[0003] Currently, the industry lacks a mature and systematic method for controlling the post-weld deformation of the boundary corrugated plates of LNG carrier cargo containment systems. There is also no clear and well-defined method for assembling and welding the three types of corner components around the boundary corrugated plates. Post-weld deformation of the boundary corrugated plates of LNG carrier cargo containment systems is a common phenomenon in the industry. This invention provides a method for controlling the post-weld deformation of the boundary corrugated plates of LNG carrier cargo containment systems by introducing a special clamping fixture and designing an assembly and welding method for the corner components around the boundary corrugated plates. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for controlling post-weld deformation of the boundary corrugated plate of an LNG carrier cargo containment system. The aim is to resolve post-weld deformation of three types of corner components on the boundary corrugated plate. The technical solution adopted is as follows: A method for controlling the deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier after welding requires the use of a clamping fixture, which includes two clamping blocks and a telescopic rod, with a gap between the two clamping blocks; The telescopic rod has a telescopic sleeve and a telescopic inner rod. The telescopic inner rod is inserted from one end of the telescopic sleeve and is threaded to the telescopic sleeve. The other end of the telescopic sleeve is hinged to one end of the bidirectional screw rod. The other end of the bidirectional screw rod is hinged to the top of one of the pressure blocks. A tension gauge is installed inside the bidirectional screw rod. The telescopic sleeve is hinged to the top of another pressure block in the middle. A pressure plate is hinged to the free end of the telescopic inner rod. The specific welding process for the boundary corrugated plate is as follows: Inspect the assembly clearance of all corner connectors and end seals. After the assembly clearance requirements are met, perform spot welding on the corner connectors and end seals. After spot welding, inspect the corner connectors and end seals, mark the raised positions after welding, and mark the raised positions as the work stations.

[0005] A clamping fixture is installed near the raised area, with the clamping block pressing against the corrugated knot near the raised area. The length of the telescopic inner rod is adjusted to ensure that the clamping plate is completely in contact with the surface of the boundary corrugated plate. The double-ended screw is tightened, and rotation of the double-ended screw is stopped when the tension value displayed by the tension gauge reaches 30N. The clamping block of this invention is the same as the corrugated plate clamping structure disclosed in Chinese invention patent "An Automatic Laser Welding Device and Method for Corrugated Plates of LNG Transport Ships", application number "202511566760.3".

[0006] After the clamping fixture is installed, first complete the continuous welding of the corner connectors within the workstation, and then complete the continuous welding of the corner connectors adjacent to the workstation.

[0007] Next, complete the continuous welding of the corner connectors within the workstation, then complete the continuous welding of the corner connectors adjacent to the workstation; finally, perform continuous welding of the end seals adjacent to the workstation.

[0008] After the welds around the corner connector have completely cooled, loosen the double-ended screw and remove the clamping fixture.

[0009] Furthermore, in the above-mentioned method for controlling the deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier after welding, the tensile tester load is 50N.

[0010] Furthermore, the above-mentioned method for controlling the deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier is further improved by checking that the assembly gap meets the requirement of ≤0.3mm.

[0011] Furthermore, in the above-mentioned method for controlling the deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier after welding, the bottom of the pressure block has a groove, and the corrugated knot is located in the groove.

[0012] Furthermore, in the above-mentioned method for controlling the deformation of the boundary corrugated plate of the cargo containment system of an LNG carrier, before operation, the surface of the boundary corrugated plate is checked for damage and the welding area is cleaned with acetone, requiring that there be no oil or dust.

[0013] Furthermore, in the aforementioned method for controlling the deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier after welding, the steel corners are made of 8mm stainless steel plates.

[0014] The beneficial effects of this invention are: 1. The assembly method for corner components on the corrugated plate of the LNG carrier cargo containment system boundary is clearly defined. Utilizing a staggered, cross-assembly approach, corner components are installed at any workstation and adjacent workstations without sacrificing construction efficiency, minimizing heat input accumulation. By cross-installing corner connectors and end seals at three workstations, on-site construction efficiency and material quantity are guaranteed without affecting efficiency, while also meeting the time requirements for weld cooling after corner component welding. Furthermore, from a lean manufacturing perspective, the repeated installation of the same type of corner component, due to its consistent welding path, eliminates unnecessary waste of effort, significantly improving the efficiency of manual welding personnel.

[0015] 2. Clarify the welding method for corner components on the boundary corrugated plate. Starting with the welding sequence of corner components, utilize the characteristic that the heat dissipation rate of the steel corner beside the boundary corrugated plate is better than that of the boundary corrugated plate. Change the traditional method of completing the corner component welding in one go in the industry. That is, the corner components overlapping on the boundary corrugated plate and the steel corner are welded in sections. First, complete the welding of the corner component overlapping on the boundary corrugated plate, and then complete the welding of the corner component overlapping on the steel corner. By taking advantage of the heat dissipation rate of the steel corner compared to the heat dissipation rate of the boundary corrugated plate, the heat accumulated by the corner component welded on the boundary corrugated plate is effectively transferred to the steel corner area. At the same time, the stress concentrated by the corner component welded on the boundary corrugated plate is dispersed to the steel corner. In this way, the accumulation of post-weld deformation of the boundary corrugated plate is reduced during the welding stage, and the bulging phenomenon of the boundary corrugated plate is effectively controlled.

[0016] 3. Utilize the pre-tightening effect to pre-install a special clamping fixture on the area surrounded by the boundary corrugated plate for the three types of corner components. Press the pressure plate on the special clamping fixture against the raised area of ​​the corrugated plate in advance. Before completing the welding of the three types of corner components by manual welding, maintain the pressure of the special clamping fixture on the raised area. By applying pre-force to the boundary corrugated plate through the special clamping fixture, the stress during welding is dispersed, and the stress concentration during welding is controlled to effectively prevent the boundary corrugated plate from bulging.

[0017] 4. The length and height of the special clamping fixture can be adjusted according to the differences in installation position. Affected by the installation accuracy of the special clamping fixture and the position of the corrugated plate at the boundary, the length and height of the special clamping fixture need to be finely adjusted on site. The telescopic rod and pressure rod at the front end of the special clamping fixture body used in this solution can be adjusted in length. The bottom of the telescopic rod has a thread that fits with the internal thread at the front end of the special clamping fixture body. Its length can be adjusted by rotating the telescopic rod. Similarly, the pressure rod is also a telescopic structure with nested internal and external threads. Its length can be adjusted by rotating the pressure rod.

[0018] 5. A tension gauge is installed on the special clamping fixture. The clamping force of the special clamping fixture on the boundary corrugated plate can be observed in real time. When the operator rotates the bidirectional screw, he can observe the tension value on the tension gauge in real time. This enables precise control of the magnitude of the pre-applied force of the special clamping fixture on the boundary corrugated plate, avoiding damage to the surface of the corrugated plate caused by excessive clamping force, and also avoiding insufficient deformation control caused by insufficient clamping force. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the clamping fixture; Figure 2 This is a schematic diagram of welding three types of corner components onto a boundary corrugated plate using a clamping fixture; 1-Clamping fixture, 2-Double-actuated screw, 3-Force gauge, 5-Telescopic sleeve, 6-Telescopic inner rod, 7-Pressure block, 8-Pressure plate, 9-Raised area, 10-Boundary corrugated plate, 11-Corner connector, 12-Corner connector, 13-End seal. Detailed Implementation

[0020] The invention will be further described with reference to the accompanying drawings.

[0021] A method for controlling post-weld deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier, such as... Figure 1 As shown, the clamping fixture includes two clamping blocks 7 and a telescopic rod, with a gap between the two clamping blocks. The telescopic rod has a telescopic sleeve 5 and a telescopic inner rod 6. The telescopic inner rod is inserted into one end of the telescopic sleeve and threadedly connected to the telescopic sleeve. The other end of the telescopic sleeve is hinged to one end of a double-acting screw 2. The other end of the double-acting screw is hinged to the top of one of the clamping blocks. A tension gauge 3 is installed inside the double-acting screw. The telescopic sleeve is hinged to the top of another clamping block in the middle. A pressure plate 8 is hinged to the free end of the telescopic inner rod.

[0022] The three types of corner components are corner connector 11, corner connector 12, and end seal 13, such as Figure 2 As shown, the specific process of welding three types of corner components onto the boundary corrugated plate is as follows: S1: Inspect the surface of the boundary corrugated plate for damage and clean the welding area with acetone, ensuring it is free of oil and dust.

[0023] S2: According to the construction drawings, check the assembly clearance of the corner connectors. The assembly clearance must be ≤0.3mm.

[0024] S3: Adjust the parameters of the argon arc welding machine according to the requirements of the Welding Procedure Specification (WPS), and select any corner connector at the workstation to complete the assembly spot welding.

[0025] S4: Repeat steps S2 to S3 to complete the spot welding of the other two adjacent corner connectors on the side of the workstation.

[0026] S5: According to the construction drawings, select the end seals at the workstation and check that the assembly gap is ≤0.3mm.

[0027] S6: Check and adjust the parameters of the argon arc welding machine according to the Welding Procedure Specification (WPS), and select any station to assemble and spot weld the end seals.

[0028] S7: Repeat steps S5 to S6 to complete the spot welding of the other two adjacent end seals on the side of the workstation.

[0029] S8: Install one corrugated knot clamp on each of the corrugated knots and adjacent corrugated knots on the extended line of the corrugated plate near the boundary. The clamping fixture is similar to a four-bar linkage.

[0030] S9: Rotate the telescopic inner rod so that the pressure plate at the front end of the clamping fixture is directly opposite the pre-clamping area of ​​the boundary corrugated plate.

[0031] S10: Tighten the bidirectional screw, bring the pressure plate close to the surface of the boundary corrugated plate, and stop rotating the bidirectional screw when the tension gauge shows a tension value at both ends.

[0032] S11: Adjust the pressure plate so that it is completely attached to the surface of the boundary corrugated plate.

[0033] S12: Continue to tighten the double-ended screw to press the pressure plate against the surface of the boundary corrugated plate. When the tension value displayed by the tension gauge reaches 30N, stop rotating the double-ended screw.

[0034] S13: Adjust the TIG welding machine parameters according to the Welding Procedure Specification (WPS) to complete the continuous welding of the corner connector near the boundary corrugated plate. One end of the corner connector is connected to the boundary corrugated plate, and the other end is connected to the steel corner.

[0035] S14: Complete the continuous welding of the corner connectors of the remaining corrugated plates near the boundary adjacent to the workstation.

[0036] S15: Adjust the TIG welding machine parameters according to the Welding Procedure Specification (WPS) to complete the continuous welding of the corner connector where the workstation meets the steel corner. The two ends of the corner connector rest on the boundary corrugated plate and the steel corner respectively. We utilize the difference in heat dissipation performance of the lapped materials to weld the two ends of the corner connector separately.

[0037] S16: Complete the continuous welding with the remaining end seals near the adjacent steel corner.

[0038] S17: Complete the continuous welding of the corner connectors adjacent to the workstation. The corner connector is one of the corner components, but all corner components overlap on the steel corner, so there is no need to weld them separately. Once the corner connector is welded, the corner connector can be welded directly.

[0039] S18: Adjust the parameters of the argon arc welding machine according to the requirements of the Welding Procedure Specification (WPS) to complete the continuous welding of the end seal of the corrugated plate near the boundary of the station.

[0040] S19: Complete the continuous welding of the remaining corrugated plate end seals near the boundary adjacent to the workstation.

[0041] S20: Adjust the parameters of the argon arc welding machine according to the requirements of the Welding Procedure Specification (WPS) to complete the continuous welding of the end seals near the steel corner of the workstation.

[0042] S21: Complete the continuous welding of the remaining end seals near the steel corner adjacent to the workstation.

[0043] S22: After the corner connectors and end seals of the lower inclined plane and its adjacent vertical plane inside the cabin are installed, repeat steps S2 to S4 and S14 to S17 to complete the assembly and continuous welding of the corner connectors.

[0044] S23: After the weld around the corner connector has completely cooled, loosen the double-ended screw and remove the clamping fixture.

[0045] This invention addresses the assembly sequence and scope of corner components. The assembly sequence involves first installing the corner connector at one workstation, then installing the second corner connector at the workstation adjacent to the first workstation, and finally installing the third corner connector at the workstation on the other side of the first workstation. Similarly, the end seals are installed in the same manner: first the end seal at one workstation, then the second end seal at the workstation adjacent to the first workstation, and finally the third end seal at the workstation on the other side of the first workstation. This invention changes the traditional method of directly installing corner connectors and end seals at a single workstation. Directly installing corner connectors and end seals at one workstation, without sacrificing construction efficiency, results in insufficient cooling time for the welds, easily leading to heat accumulation. By installing corner connectors and end seals at three different workstations in a staggered manner, on-site construction efficiency and material quantity are not affected. The consistent welding path for repeated installation of the same type of corner component improves the efficiency of manual welding personnel, while also meeting the required cooling time for the welds after corner component welding.

[0046] The welding method for corner components on the boundary corrugated plate was clarified, starting with the welding sequence of the corner components. The steel corner pieces on the side of the boundary corrugated plate are made of 8mm stainless steel, which has good heat dissipation performance. Taking advantage of the fact that the heat dissipation rate of the steel corner pieces on the side of the boundary corrugated plate is better than that of the boundary corrugated plate, the traditional method of welding corner components in one go, which overlaps the steel corner pieces, is changed. The corner pieces are welded in sections. First, the corner pieces are welded to the boundary corrugated plate, and then the overlaps are welded to the steel corner pieces. By taking advantage of the heat dissipation rate of the steel corner pieces compared to the boundary corrugated plate, the heat accumulated by the corner pieces welded to the boundary corrugated plate is effectively transferred to the steel corner area. At the same time, the stress concentrated by the corner pieces welded to the boundary corrugated plate is dispersed to the steel corner, thereby reducing the accumulation of post-weld deformation of the boundary corrugated plate during the welding stage and effectively controlling the occurrence of boundary corrugated plate bulging.

[0047] Design a special clamping fixture. Before welding the three types of corner components around the boundary corrugated plate, install corrugated knot clamps on the corrugated knots near the raised area of ​​the boundary corrugated plate and on adjacent corrugated knots on the extension line. Assemble the special clamping fixture on the corrugated knot clamps. By adjusting the length and height of the special clamping fixture, the end of the special clamping fixture contacts and squeezes into the raised area of ​​the corrugated plate. Before completing the welding of the three types of corner components by manual welding, maintain the pressure of the special clamping fixture on the raised area. The stress during welding is dispersed by the pre-applied force of the special clamping fixture on the boundary corrugated plate.

[0048] The length and height of the special clamping fixture can be adjusted according to the differences in the installation position. The corrugated plates of the cargo containment system are arranged neatly and tightly. Although the distance between the large and small corrugations on the corrugated plates is consistent, the length and height of the special clamping fixture need to be finely adjusted due to the installation accuracy of the special clamping fixture and the position of the raised edge of the corrugated plate. The telescopic rod of the special clamping fixture is threaded to the fixture body. It can be extended and retracted in the thread of the body by rotating the telescopic rod. Similarly, the pressure rod connected to the telescopic rod of the special clamping fixture is also a nested structure with threaded engagement. It can be extended and retracted by rotating the pressure rod.

[0049] The clamping force of the special clamping fixture can be monitored in real time. A tension gauge is installed at the pressure adjustment position of the special clamping fixture, that is, between the bidirectional screw and the body of the special clamping fixture. When the operator rotates the bidirectional screw, the tension value on the tension gauge can be observed in real time. This enables precise control of the magnitude of the pre-applied force of the special clamping fixture on the boundary corrugated plate, avoiding damage to the surface of the corrugated plate caused by excessive clamping force applied by the special clamping fixture to the boundary corrugated plate, and also avoiding insufficient deformation control caused by insufficient clamping force applied by the special clamping fixture to the boundary corrugated plate.

Claims

1. A method for controlling post-weld deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier, characterized in that, A clamping fixture is required, which consists of two clamping blocks and a telescopic rod, with a gap between the two clamping blocks; The telescopic rod has a telescopic sleeve and a telescopic inner rod. The telescopic inner rod is inserted from one end of the telescopic sleeve and is threaded to the telescopic sleeve. The other end of the telescopic sleeve is hinged to one end of the bidirectional screw rod. The other end of the bidirectional screw rod is hinged to the top of one of the pressure blocks. A tension gauge is installed inside the bidirectional screw rod. The telescopic sleeve is hinged to the top of another pressure block in the middle. A pressure plate is hinged to the free end of the telescopic inner rod. The specific welding process for the boundary corrugated plate is as follows: Inspect the assembly clearance of all corner connectors and end seals. After the assembly clearance requirements are met, perform spot welding on the corner connectors and end seals. After spot welding, inspect the corner connectors and end seals, circle the raised area after welding, and mark the raised area after welding as the work station. Install the clamping fixture near the raised position, press the clamping block on the corrugated knot near the raised position, adjust the length of the telescopic inner rod so that the clamping plate is completely in contact with the surface of the boundary corrugated plate, tighten the double-ended screw, and stop rotating the double-ended screw when the tension value displayed by the tension gauge reaches 30N. After the clamping fixture is installed, first complete the continuous welding of the corner connectors in the station, and then complete the continuous welding of the corner connectors adjacent to the station. Next, complete the continuous welding of the corner connectors within the workstation, then complete the continuous welding of the corner connectors adjacent to the workstation; finally, perform continuous welding of the end seals adjacent to the workstation. After the welds around the corner connector have completely cooled, loosen the double-ended screw and remove the clamping fixture.

2. The method for controlling post-weld deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier according to claim 1, characterized in that, The load on the tension gauge is 50N.

3. The method for controlling post-weld deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier according to claim 1, characterized in that, The assembly clearance of the corner connector and end seal must be ≤0.3mm.

4. The method for controlling post-weld deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier according to claim 1, characterized in that, The bottom of the block has a groove, and the corrugated knot is located in the groove.

5. The method for controlling post-weld deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier according to claim 1, characterized in that, Before operation, check the surface of the boundary corrugated plate for damage and clean the welding area with acetone, ensuring it is free of oil and dust.

6. The method for controlling post-weld deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier according to claim 1, characterized in that, The steel corner pieces are made of 8mm stainless steel sheet.

7. The method for controlling post-weld deformation of the corrugated plate at the boundary of the cargo containment system of an LNG carrier according to claim 1, characterized in that, The workstation includes an end seal, a corner connector, and a corner area connector.

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