Method for manufacturing a large-diameter thin-walled cylinder segment of a suction cylinder

Abstract

The application discloses a whole-circle penetrating type prefabrication method for a suction cylinder super-large-diameter thin-wall cylinder section and belongs to the technical field of large steel structure manufacturing. In view of the contradictions of workshop hoisting height limitation, thin-wall cylinder body easy deformation, poor welding quality and process fragmentation, the whole-circle penetrating type prefabrication method is provided, that is, a connecting device lifts the steel plate from the inside during coiling, and the same device hoists the whole-circle cylinder section after coiling; the cylinder section is hoisted back to the coiling machine again after welding to eliminate deformation; and finally, the U-shaped turning-over device is used to complete the code-free turning-over in cooperation with two cranes. The application realizes the whole-circle horizontal penetration of the cylinder section from coiling to turning-over, and the whole process does not need welding clamping plates or lifting lugs, and does not need to be transported for many times. After being applied to the ZS117 project, the prefabrication period of 21 8m cylinder sections is shortened from 51 days to 28 days, the daily labor is reduced from 1017 MD to 385 MD, the ellipticity is less than or equal to 5mm, and the cost is significantly reduced, the construction period is shortened and the quality is improved.

Description

Technical Field

[0001] This invention relates to the field of large steel structure manufacturing technology, specifically to a prefabrication method for ultra-large diameter thin-walled cylindrical sections such as offshore wind turbine suction cylinders, which is particularly suitable for working conditions where workshop hoisting height is limited. Background Technology

[0002] Suction cylinders are key structural components of offshore wind turbine jacket foundations, typically with a diameter of over 8 meters, a wall thickness of 30-50 millimeters, and a diameter-to-thickness ratio greater than 100. These cylinders are characterized by their "ultra-large diameter and thin walls," requiring extremely high standards for roundness and weld quality. However, due to limitations imposed by general industrial plant design standards (such as GB / T 783-2023), the lifting height of overhead cranes in workshops is usually only 9-10 meters, making it impossible to vertically hoist 8-meter diameter cylinder sections. This physical constraint has become a long-standing bottleneck in cylinder manufacturing.

[0003] Faced with the limitation of hoisting height, the "tile segmentation method" has long been used in this field: the cylinder is divided into 2 to 3 tiles and rolled separately, then the tiles are vertically assembled and welded with longitudinal seams, and then transported and turned over many times. References [1] (CN202310571399) and [2] (CN202111475113) both record this segmented manufacturing process, which represents the mainstream practice in the industry. Even in key national projects such as the Hong Kong-Zhuhai-Macau Bridge, the vertical segmentation method (i.e., tile segmentation) is used when manufacturing ultra-large diameter steel cylinders, which shows that this technical solution has been solidified as an industry practice.

[0004] However, the tile-segmentation method has several irreconcilable contradictions: Contradiction 1: The conflict between hoisting height restrictions and the goal of forming a complete circle. While segmenting the tiles circumvents the hoisting height restrictions, the longitudinal seams after tile assembly are in a vertical welding position, requiring manual MIG welding (carbon dioxide gas shielded welding). Vertical welding is not only slow and has a low pass rate, but also requires workers to operate on high scaffolding, posing significant safety hazards. To improve welding quality and efficiency, the weld seam must be placed horizontally, but horizontal welding of a complete circle is impossible with segmented tiles.

[0005] Contradiction Two: The contradiction between thin-walled characteristics and hoisting deformation. The suction cylinder's diameter-to-thickness ratio is greater than 100, making the cylinder body extremely flexible. Traditional hoisting methods require welding clamps or temporary lifting lugs onto the cylinder body, causing localized stress concentration and leading to irreversible permanent deformation. To control deformation, it is often necessary to add reinforcing structures such as star-shaped braces inside the cylinder body, which not only increases material costs but also consumes a lot of labor for welding and subsequent grinding.

[0006] Contradiction 3: The contradiction between welding deformation and subsequent processes. Welding heating inevitably causes localized wave deformation, especially near the longitudinal seam, where "angular" protrusions are very likely to appear. In the tile segmentation process, the welded cylindrical sections cannot be rolled into a whole on a plate rolling machine for rounding (returning to roundness). Only inefficient methods such as flame straightening can be used. Multiple straightenings are not only time-consuming, but also difficult to guarantee roundness.

[0007] Contradiction Four: The contradiction between fragmented processes and frequent relocation. Plate rolling machines are typically located indoors, while processes such as tile assembly and turning require larger working spaces, often necessitating outdoor or larger-span areas. This results in tiles or semi-finished cylindrical sections needing to be moved between indoors and outdoors multiple times: after rolling, they are transported outdoors for assembly; after assembly, they are transported back indoors for welding; after welding, they are transported outdoors again for turning… This repeated relocation not only consumes significant crane and flatbed truck resources but also increases the risk of deformation and safety hazards, severely prolonging the prefabrication cycle.

[0008] The aforementioned contradictions have led those skilled in the art to fall into a path dependency of "tile segmentation → vertical welding → local deformation → inefficient correction → frequent relocation" for a long time, and they have never been able to find a fundamental solution. Even though rolling auxiliary support fixtures have appeared in recent years (such as reference [3] CN202410270069), their function is limited to preventing sagging during the rolling process and cannot realize the hoisting of the whole circle after rolling; while the existing turning fixtures (such as reference [4] CN202311349917) are either powered or require separate hoisting of the cylinder section into place, and cannot be quickly connected with the rolling and welding processes.

[0009] Therefore, how to achieve efficient and high-quality prefabrication of ultra-large diameter thin-walled cylindrical sections in workshops with limited hoisting height, while avoiding chronic problems such as welding and stacking, multiple relocations, and poor vertical welding quality, has become a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0010] To address the multiple contradictions in the aforementioned background technologies, such as lifting height limitations and the need for whole-circle forming, thin-walled characteristics and lifting deformation, welding deformation and subsequent processes, and process interruptions and frequent relocation, this invention proposes a whole-circle through-type prefabrication method. The core idea is to maintain the cylindrical section in a fully circular, horizontal position throughout the entire process, from rolling to welding, forming, and turning. This approach directly bypasses the lifting height limitations (the cylindrical section is horizontal, eliminating the need for vertical erection), but it also introduces new challenges: How to unload and lift the fully circular cylindrical section from the rolling machine? How to avoid localized deformation during lifting of the thin-walled section? How to eliminate post-weld wavy deformation? How to avoid welding lifting lugs during the turning process? These challenges need to be overcome one by one.

[0011] Firstly, to solve the problem of unloading and hoisting the entire cylindrical section, this invention designs a receiving device. Viewed from the side, the device is a flat isosceles triangle: the apex is a lifting beam (longer than the height of the cylindrical section, extending beyond the ends of the section), and the base consists of multiple cantilevered receiving support rods arranged in an arc shape, their curvature matching the inner wall of the cylindrical section. The two sides of the triangle are formed by stiffening plate assemblies, connecting the lifting beam and the bottom support rods into a single unit, transferring the hoisting load. The lifting beam is equipped with multiple lifting lugs (including a large lug in the center and smaller lugs distributed in different positions), allowing for flexible selection of lifting point combinations based on the cylindrical section's center of gravity. The device's open side has a flip-up hook that opens upon insertion and flips up to close after insertion, naturally locking under its own weight during hoisting. Mechanical calculations show that this structure possesses sufficient strength and rigidity under the rated hoisting load, ensuring safe use.

[0012] When the steel plate is rolled into a semicircle on the rolling machine, the guiding device is horizontally inserted from one end of the drum section along its axial direction, allowing the cantilevered guiding support rod at the bottom to extend into the inside of the steel plate and support the inner wall of the rolled portion. The device is suspended and fixed in place by a gantry crane; the steel plate continues to slide forward through the opening of the device. This device is subjected to intermittent force during the rolling process—it only supports the steel plate when it sags due to gravity, preventing the steel plate from becoming unstable.

[0013] After the steel plate is closed into a complete cylindrical section, the connecting device is naturally positioned inside and above the section. At this point, the hook is flipped up and closed, and the crane pulls upwards using the lifting lugs on the lifting beam, ensuring close contact between the bottom support rod and the inner wall of the section. Because the support rods are arranged in an arc shape, the lifting force is evenly distributed across the entire area of ​​the top inner wall of the section, avoiding localized stress concentration. The crane continues lifting, thus lifting the entire cylindrical section as a whole, without the need to weld any clamps or lifting lugs onto the cylinder (i.e., "clip-free" lifting).

[0014] Thus, the problems of unloading and hoisting the entire cylindrical section were solved. However, a new problem arose: welding heating inevitably caused local wave deformation. How could this deformation be eliminated without disassembling the cylindrical section? To address this, the present invention hoists the welded cylindrical section back to the plate rolling machine for recirculation.

[0015] Specifically, after the longitudinal seam welding is completed, the same set of guiding devices (which can still be easily inserted into the cylindrical section) is used to lift the cylindrical section from the welding fixing device and transport it back to the plate rolling machine, so that the cylindrical section is rolled again by the three rollers of the plate rolling machine. This operation is almost impossible to achieve in the tile segmentation process (because the tiles are disassembled and cannot be rolled onto the plate rolling machine as a whole), but in the whole-circle through-through process, it can be easily completed simply by inserting the guiding device again. After the whole-circle process, the local wave deformation caused by welding is effectively eliminated, and the roundness of the cylindrical section is restored to the design requirements.

[0016] At this point, the forming and welding issues of the cylinder itself have been completely resolved. However, the subsequent turning process brings new challenges: traditional turning requires welding temporary lifting lugs and cross braces onto the cylinder section, which not only causes localized deformation but also adds post-weld grinding, contradicting the "code-free" concept of a fully circular cylinder. To avoid welding accessories during the turning process, this invention designs a code-free turning device. This device has a U-shaped structure with limiting devices on both sides to firmly fix the cylinder section, and it has its own flat lifting lugs and turning lugs. In use, the receiving device lifts the entire circular cylinder section onto the turning device, and the limiting devices tighten the cylinder section; two cranes are connected to the top lifting lug and the side lifting lug respectively, and after being lifted off the ground simultaneously, one crane remains stationary while the other continues to lift, allowing the cylinder section to smoothly turn from a horizontal position to a vertical position, without the need to weld any accessories onto the cylinder section throughout the entire process.

[0017] Through the aforementioned three-tiered closed-loop device and process, this invention successfully achieves the seamless prefabrication of ultra-large diameter thin-walled cylindrical sections in workshops with limited lifting height. From the initial connection during rolling, to the subsequent hoisting, the final rounding after welding, and the final turning, all stages require no welding clamps or lifting lugs, completely avoiding localized deformation and multiple relocations. This significantly shortens the construction period, reduces costs, and improves quality.

[0018] Thus, this invention, through its three-tiered design—a dual-purpose receiving device, a closed-loop return-to-circuit mechanism after welding, and a code-free flipping device—has overcome all the challenges in the full-circle through-process. The entire prefabrication method can be summarized in the following steps: Step 1: Rolling into a complete cylinder. The steel plate is rolled into a complete cylindrical section on a plate rolling machine. The diameter of the cylinder section is ≥8 meters and the ratio of wall thickness to diameter is ≤1 / 100.

[0019] Step 2: Positioning and guiding of the guiding device. During the rolling process, when the steel plate is rolled into a semicircle, the guiding device is horizontally inserted from one end of the axial direction of the drum section, so that the arc-shaped support rod at the bottom supports the inner wall of the steel plate. The device is fixed in place, and the steel plate slides forward in the opening of the device.

[0020] Step 3: Lifting of the receiving device. After the winding is completed, the receiving device is located inside the upper part of the cylinder section. The hook flips up and closes, and the crane lifts the cylinder section through the lifting lugs on the device, so that the support rod is in close contact with the inner wall of the cylinder section, and the entire cylindrical section is lifted as a whole.

[0021] Step 4: Transfer to the welding fixing device. The receiving device lifts the cylinder section onto the welding roller frame, and the receiving device is then removed; the rollers drive the cylinder section to rotate, bringing the longitudinal seam to a horizontal position directly above; the gantry is pushed above the weld seam, and the submerged arc automatic welding machine completes the longitudinal seam welding.

[0022] Step 5: Return to round shape after welding. After welding is completed, the connecting device is inserted into the cylinder section again, and the cylinder section is lifted back to the rolling machine for re-rolling to eliminate local wave deformation caused by welding.

[0023] Step Six: Transfer to the Turning Device. The receiving device lifts the entire cylindrical section onto the U-shaped turning device, and the limiting device tightens the section.

[0024] Step 7: Unlocked Turning. Two cranes are connected to the top and side lugs of the turning device, respectively. After being lifted off the ground simultaneously, one crane remains stationary while the other continues to lift, turning the cylinder section from a horizontal position to a vertical position.

[0025] Step 8: Lifting and Assembly. After the turning is completed, the vertically positioned cylinder section is lifted off the turning device and assembled and welded with the adjacent cylinder section.

[0026] In the above steps, the receiving device is integrated into multiple stages such as rolling, hoisting, and recirculation, achieving "one device for two purposes"; the immediate recirculation after welding forms an effective closed loop; and the turning device completely avoids the need for welding lifting lugs. The entire process does not require disassembling the cylindrical section into tiles, welding any clamps or lifting lugs, or multiple transfers, achieving efficient and high-quality prefabrication of ultra-large diameter thin-walled cylindrical sections in workshops with limited hoisting height.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1. Significantly reduced construction period and labor costs. After adopting this invention, the prefabrication cycle of 21 8-meter cylindrical sections in Project ZS117 was shortened from 51 days to 28 days, a reduction of 45%; the prefabrication man-days were reduced from 1017MD to 385MD, a saving of 62%. Calculations show that labor costs alone can be reduced by more than 250,000 yuan. At the same time, the use of equipment such as cranes and flatbed trucks was significantly reduced. This achievement is not the result of optimization in a single step, but rather a systemic transformation brought about by the whole-circuit through-process—eliminating time-consuming processes such as tile segmentation, vertical welding, multiple transfers, plate stacking, welding, and grinding, enabling the cylindrical sections to achieve "one-stop" processing from rolling to turning, minimizing waiting and reassembly time between processes.

[0028] 2. Significantly Improved Welding Quality and Efficiency. In the tile segmentation process, the longitudinal seam is in a vertical welding position, requiring manual Methane welding, which is not only inefficient but also difficult to guarantee a high pass rate. This invention places the entire cylindrical section horizontally, naturally placing the longitudinal seam in a horizontal position, thus enabling the use of submerged arc welding. Submerged arc welding offers deep penetration, fast welding speed, stable quality, and a high degree of automation, significantly reducing human error. In actual production, the welding pass rate is significantly improved, reaching over 95% on the first pass, and the weld formation is aesthetically pleasing, eliminating the need for extensive rework.

[0029] 3. Effectively eliminates welding deformation and ensures roundness. Welding heating inevitably causes localized wavy deformation, especially near the longitudinal seam where "angular" protrusions are prone to appear. This invention, after welding, uses the same set of guiding devices to quickly lift the cylinder section back to the rolling machine for rounding (re-rolling), effectively correcting welding deformation. Actual measurements show that the ellipticity of the cylinder section after rounding is controlled within 5mm, far superior to the correction effect of the tile segmentation process. This "welding → rounding closed loop" is almost impossible to achieve in the tile segmentation process, representing a unique advantage of the rounding through-process technology.

[0030] 4. Code-free operation avoids localized deformation and saves auxiliary time. From rolling to turning, this invention eliminates the need for welding any clamps, lifting lugs, or cross braces onto the cylinder. The receiving device lifts the cylinder from the inside using an arc-shaped support rod, evenly distributing the lifting force; the turning device secures the cylinder section using a U-shaped bracket and limiting device, and its built-in lifting lugs complete the turning process. Compared to traditional processes, each cylinder section saves approximately 4-6 hours in steps such as welding clamps, grinding clamps, welding lifting lugs, and cutting lifting lugs, and completely avoids localized stress concentration and permanent deformation caused by welding accessories.

[0031] 5. Expanding the processing capacity of plate rolling machines and enhancing market competitiveness. Through the receiving device and full-circuit through-process of this invention, the upper limit of the rolling capacity of existing plate rolling machines is effectively expanded. This means that enterprises can undertake the manufacturing of suction cylinders with larger diameters without purchasing new equipment, significantly improving their market competitiveness. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of the whole-circle through-type prefabrication method of the present invention; Figure 2 This is a three-dimensional structural diagram of the receiving device of the present invention; Figure 3 for Figure 2 Projected view of the end face of the connecting device shown; Figure 4 This is a front view schematic diagram of the receiving device of the present invention in the receiving state during the winding process; Figure 5 This is a front view of the receiving device of the present invention in the hoisting state after the winding is completed; Figure 6 This is a finite element analysis cloud diagram of the receiving device of the present invention; Figure 7 This is a front view schematic diagram of the transfer cylinder section where the receiving device and welding fixing device of the present invention are used together; Figure 8 This is a front view schematic diagram of the welding state of the present invention; Figure 9 This is a schematic diagram of the structure of the turning device of the present invention; Figure 10The diagram shows the finite element analysis of the turning device of the present invention, where (a) represents the horizontal state and (b) represents the turning state. Figure 11 This is a front view schematic diagram of the transfer cylinder section where the receiving device and the turning device of the present invention are used together; Figure 12 This is a frontal view of the starting state of the turning-over process according to the present invention; Figure 13 This is a frontal view of the intermediate state during the turning process of the present invention; Figure 14 This is a frontal view of the completed flipping state of the present invention.

[0033] Marked in the image: 1-Cantilever support rod, 2-Ribbon, 3-First stiffening plate, 4-Second stiffening plate, 5-Third stiffening plate, 6-Lifting beam, 7-Lifting lug, 8-Wire rope, 9-Hook, 10-Fixing plate, 11-Inclined connecting plate, 12-Horizontal connecting plate, 13-Plate rolling machine, 14-Steel plate (cylindrical section), 15-Welding roller frame, 16-Power roller, 17-Baffle, 18-Rail-type gantry frame, 19-Submerged arc automatic welding machine, 20-Turning device base, 21-Limiting device, 22-Top flat lifting lug, 23-Side turning lifting lug, 24-Ladder, 25-Operating platform, 26-Crane A, 27-Crane B. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0035] Example 1: This example provides a whole-circle through-type prefabrication method for ultra-large diameter thin-walled cylinder sections of suction cylinders. Taking an 8-meter diameter, 3-meter height, and 30-50mm wall thickness cylinder section from the ZS117 project as an example, it is implemented in a workshop with a hoisting height of 9 meters.

[0036] Step 1: Rolling into a complete cylinder. The steel plate is rolled into a complete cylindrical section on a plate rolling machine. The rolling accuracy is controlled so that the ovality is ≤5mm.

[0037] Step 2: Positioning and connection of the receiving device. During the rolling process, when the steel plate is rolled into a semicircle, the receiving device is horizontally inserted from one end of the axial direction of the drum section, so that the cantilever receiving support rod 1 at the bottom of the device supports the inner wall of the steel plate 14 (see...). Figure 4 The device is suspended and fixed in place by a gantry crane; the steel plate continues to slide forward in the opening of the device, and the device is subjected to intermittent force to prevent the steel plate from sagging.

[0038] Step 3: Hoisting of the receiving device. After winding, the receiving device is naturally positioned above the inside of the drum section. Flip up and close the hook 9 on the device, and the crane pulls it upwards using the lifting lugs 7 on the lifting beam 6, ensuring the bottom support rod is in close contact with the inner wall of the drum section (see...). Figure 5 The entire cylindrical section is lifted as a whole, without the need to weld clamps or lifting lugs onto the cylinder.

[0039] Step 4: Transfer to the welding fixing device and weld. The receiving device lifts the cylinder section onto the welding roller frame 15 (see...). Figure 7 The receiving device is removed. The roller-driven cylinder section rotates, bringing the longitudinal seam to a horizontal position directly above. The track-mounted gantry is pushed above the weld seam, and the submerged arc welding machine 19 completes the longitudinal seam welding (see...). Figure 8 ).

[0040] Step 5: Post-weld rounding. After welding, the connecting device is reinserted into the cylinder section, which is then lifted back to the rolling machine and rolled again to eliminate localized wavy deformation caused by welding. After rounding, the ovality of the cylinder section is controlled within 5mm.

[0041] Step 6: Transfer to the turning device. The receiving device lifts the entire cylindrical section onto the U-shaped turning device base 20, and the limiting device 21 tightens the section from both sides (see...). Figure 11 ).

[0042] Step 7: Unlocked Turning. Crane A 26 and Crane B 27 are respectively connected to the top flat lifting lug 22 and the side turning lifting lug 23 of the turning device (see...). Figure 12 At the same time, after being lifted off the ground, crane A remains stationary while crane B continues to lift, so that the cylinder section can be smoothly rotated from a horizontal position to a vertical position.

[0043] Step 8: Lifting and Assembly. After the turning is completed, the vertically positioned cylinder section is lifted off the turning device and assembled and welded with the adjacent cylinder section.

[0044] According to actual production statistics, after adopting the above method, the prefabrication cycle of 21 cylinder sections was shortened from 51 days to 28 days, the man-days were reduced from 1017MD to 385MD, saving more than 250,000 yuan in labor costs, and the ellipticity was controlled within 5mm.

[0045] Example 2: Based on Example 1, this example further describes in detail the specific structure and operation details of the receiving device.

[0046] Receiving device (see) Figure 2 , Figure 3Viewed from the side, it resembles a flat isosceles triangle. Its top is the lifting beam 6, approximately 4 meters long, exceeding the height of the cylindrical section (3 meters), with both ends extending beyond the ends of the section. The lifting beam 6 has five lifting lugs 7: two large lugs located in the center (which can be considered a group, used for direct lifting of the midpoint with a single cable), and three small lugs located at the left, right 1 / 5, and right 2 / 5 of the lifting beam, respectively. The combination of lifting points can be flexibly selected according to the center of gravity of the cylindrical section, adapting to situations where the section is unevenly weighted.

[0047] The bottom of the receiving device consists of five cantilever receiving support rods 1 (three or four rods may be used for different specifications). These support rods are all straight rods, but arranged in an arc shape, with their curvature matching the inner wall of the cylinder section. The free ends of the support rods are connected by a transverse rod 2 to enhance the overall rigidity.

[0048] The two sides of the triangle are formed by stiffening plate assemblies, including a first stiffening plate 3, a second stiffening plate 4, and a third stiffening plate 5 (see...). Figure 3 These components form a stable triangular structure, connecting the lifting beam and the bottom support rod into a single unit, and transferring the lifting load. The arrangement and dimensions of the stiffening plates have been optimized through finite element analysis to ensure uniform stress distribution and deformation control within allowable limits under the rated lifting load.

[0049] The device has a hook 9 on the open side, which is operated manually by pulling a rope and a pulley. The hook opens when the cylinder section is inserted, and flips up to close after insertion, naturally locking itself by its own weight during lifting, without the need for an additional locking mechanism.

[0050] Finite element analysis (see) Figure 6 Under the rated lifting load (approximately 30 tons), the maximum deformation of the device without hooks is 9 mm, and the maximum stress is 74 MPa; with hooks, the maximum deformation is 1.3 mm, and the maximum stress is 49 MPa. Both are far below the yield strength of Q345 steel (345 MPa), providing a sufficient safety factor. Furthermore, the deformation is within the elastic range, and the cylinder section can fully recover after landing.

[0051] In this embodiment, the specific operations of steps 2 and 3 are both completed using the aforementioned receiving device. Example 3: Based on Example 1, this example further describes in detail the specific operation of the welding fixing device and the complete circular closed loop.

[0052] The welding fixing device is the welding roller frame 15 (see...) Figure 7 , Figure 8 The bottom of the welding roller frame is equipped with a power roller 16, which can drive the cylinder section to rotate around its axis. Baffles 17 are provided on both sides of the roller frame to prevent the cylinder section from moving axially. A track-type gantry frame 18 is provided above the welding roller frame, which can move along the track to be directly above the weld seam. An automatic submerged arc welding machine 19 can be fixed on the gantry frame.

[0053] Step 4 is operated as follows: After the receiving device hoists the cylinder section onto the welding roller frame, the receiving device is removed. The roller frame is started, driving the cylinder section to rotate, so that the longitudinal seam moves from the bottom to a horizontal position directly above. The gantry is pushed above the weld seam, the welding machine position is adjusted, and the submerged arc welding machine is started, automatically moving along the weld seam for welding. Welding parameters are set according to the cylinder section wall thickness and material (e.g., current 500–800A, voltage 30–40V, speed 30–50cm / min; specific values ​​can be adjusted according to the actual process). After welding, the longitudinal seam is aesthetically pleasing, requiring minimal rework.

[0054] Step 5 is performed as follows: After welding, localized wavy deformation will occur near the weld due to the welding heating. At this time, the receiving device is reinserted into the cylinder section (insertion is very convenient as the opening side of the device can be opened). The cylinder section is then lifted from the welding roller frame by a crane and transported back to the plate rolling machine. The cylinder section is then rolled again by the three rollers of the plate rolling machine. The rolling parameters are similar to those during rolling, but the downward pressure is appropriately reduced to correct the localized wavy deformation. After rounding, the roundness of the cylinder section is restored to the design requirements, and the measured ellipticity is controlled within 5mm.

[0055] This "welding → full circle closed loop" utilizes the same set of receiving devices, eliminating the need to change tooling, and the cylinder section always maintains a full circle horizontal posture, making the operation simple and efficient.

[0056] Example 4: Based on Example 1, this example further describes in detail the specific structure of the turning device and the details of the turning operation.

[0057] The turning device has a U-shaped structure. Its base 20 has limiting devices 21 on both sides, two pairs of top-mounted flat lifting lugs 22 (4 in total) on the top, and one pair of side-mounted turning lifting lugs 23 (2 in total) on the sides. The device also includes a ladder 24 and an operating platform 25 to facilitate workers installing lifting slings (see...). Figure 9 Finite element analysis (see...) Figure 10 Under rated load, the deformation and stress of the turning device in both horizontal and turning states are within a safe range, indicating that the structure is reliable.

[0058] The specific steps for steps 6 and 7 are as follows (see...) Figures 11-14 ): The receiving device hoists the entire cylindrical section onto the base 20 of the turning device, placing the section horizontally within the U-shaped bracket. The adjusting limiting device 21 tightens the section from both sides to prevent it from sliding or slipping out during the turning process.

[0059] Connect the wire ropes 8 of cranes A 26 and B 27 to the top horizontal lifting lug 22 and the side turning lifting lug 23, respectively. Lift both cranes simultaneously, raising the device and cylinder section approximately 200-300mm off the ground. Keep crane A stationary while crane B slowly raises the device and cylinder section, gradually rotating them around the bottom fulcrum, changing the cylinder section from a horizontal to an inclined position (see...). Figure 13 Continue raising crane B until the cylinder section is completely vertical (see...). Figure 14 At this point, the cylinder section has been turned into position and can be lifted off the turning device for assembly and welding with the adjacent cylinder section.

[0060] The entire turning process requires no temporary lifting lugs or cross braces to be welded onto the cylinder section, achieving a "code-free" turning.

[0061] In summary, the technical solution of the present invention integrates four technical features into an organic whole: horizontal penetration of the whole circle, dual-purpose receiving device, closed-loop return to the circle after welding, and codeless turning device. At the same time, it solves four contradictions: lifting height limitation, thin-walled hoisting deformation, welding deformation, and frequent relocation.

[0062] Under the conditions of limited lifting height (contradiction 1) and thin-walled cylinder easily deformable (contradiction 2), the receiving device realizes the dual functions of receiving during the rolling process and lifting after rolling. During rolling, its arc-shaped support rod supports the steel plate from the inside to prevent it from sagging due to its own weight; after rolling, the same device directly serves as a lifting tool to evenly lift the entire cylindrical section from the inside without the need for welding clamps or lifting lugs. This design keeps the cylinder section in a horizontal position at all times, completely bypassing the lifting height limit, and avoiding local stress concentration caused by traditional lifting. However, the rolling support tool in reference [3] can only achieve anti-sagging during rolling, cannot undertake the lifting function, and cannot be connected with subsequent processes.

[0063] The local wave deformation caused by welding (contradiction three) and the frequent indoor and outdoor transport during the tile segmentation process (contradiction four) exacerbate each other in the segmentation method (such as in references [1] and [2]): the welding deformation cannot be completely rounded, and the tiles need to be repeatedly transported to different sites. This invention uses the same set of connecting devices to quickly lift the welded cylindrical sections back to the rolling machine for rounding, forming a closed loop. Since the connecting device runs through the entire process of rolling, lifting, and rounding, the cylindrical sections do not need to be disassembled or transported outdoors to complete the rounding, the welding deformation is effectively eliminated, and the ellipticity is controlled within 5mm.

[0064] The turning process is constrained by both thin-wall deformation (contradiction two) and process connection (contradiction four). Traditional turning requires welding temporary lifting lugs and cross braces, which not only causes new deformations but also requires the cylindrical section to be hoisted separately to the turning station. The turning device of this invention adopts a U-shaped structure, with its own lifting lugs and limiting device, which directly cooperates with the receiving device: the receiving device hoists the entire cylindrical section onto the turning device, and after the limiting device is tightened, the two cranes can complete the turning without any code, without any intermediate transfer or additional welding. This is fundamentally different from the turning fixture in reference [4] that requires electric drive and separate hoisting.

[0065] It should be noted that the above technical solutions are derived from the company's actual R&D process in production. From 2020 to 2023, the company used the traditional tile-segmentation method to manufacture cylinder sections with a diameter of approximately 6 meters. Due to the small production volume, efficiency issues were not prominent. Starting in 2023, the company undertook the ZS117 project, which required the batch production of 21 suction cylinder sections with a diameter of 8 meters, a height of 3 meters, and a wall thickness of 30-50 mm. Under the tile-segmentation process, each cylinder section required cumbersome processes such as rolling → tile transportation → vertical assembly → vertical welding → multiple transfers → turning over. Moreover, the rolling machine could only roll a diameter of 7 meters, and repeated indoor and outdoor transfers severely prolonged the cycle. After more than half a year of operation, it was found that, according to the original process, the prefabrication cycle of 21 cylinder sections was expected to be as long as 51 days, with a labor demand of up to 1017MD, and the vertical welding qualification rate was low with severe local deformation, which could not meet the project's schedule and quality requirements.

[0066] To address this, starting in May 2023, the company's technical team held multiple discussions with technical, process, and production managers to explore ways to overcome the lifting height limitations and proposed the idea of ​​a full-circle through-hole design. After repeated trials and optimizations, they designed a receiving device (with dual functions), a closed-loop return-to-circle design after welding, and a code-free turning device, and conducted finite element analysis verification. Ultimately, the first 8-meter cylindrical section was successfully rolled in one go. Statistics show that by adopting the new process of this invention, the prefabrication cycle for 21 cylindrical sections was shortened to 28 days, the number of man-days was reduced to 385 man-days, saving over 250,000 yuan in labor costs. The use of equipment such as cranes and flatbed trucks was significantly reduced, the ellipticity of the cylindrical sections was controlled within 5mm, the welding qualification rate was significantly improved, and no clamps or lifting lugs were required throughout the entire process.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the full-circle through-type prefabrication of ultra-large diameter thin-walled cylinder sections for suction cylinders, characterized in that, Includes the following steps: Step 1: Roll the steel plate into a whole cylindrical section on a plate rolling machine. The diameter of the cylindrical section is ≥8 meters and the ratio of wall thickness to diameter is ≤1 / 100. Step 2: During the rolling process, when the steel plate is rolled into a semicircle, insert the receiving device horizontally from one end of the axial direction of the drum section, so that the arc-shaped support rod at the bottom of the receiving device supports the inner wall of the steel plate. The receiving device is fixed and the steel plate slides forward in the opening of the receiving device. Step 3: After the winding is completed, the receiving device is located inside the upper part of the cylinder. Flip up and close the hook on the receiving device, and the crane lifts the cylinder through the lifting lug on the receiving device, so that the arc-shaped support rod is in close contact with the inner wall of the cylinder, and the entire cylindrical section is lifted up as a whole. Step 4: The guiding device lifts the cylinder section onto the welding fixing device, and then the guiding device is removed; the cylinder section is driven to rotate so that the longitudinal seam is turned to the horizontal position directly above, and the longitudinal seam welding is completed by submerged arc automatic welding. Step 5: After welding is completed, the connecting device is inserted into the cylinder section again, and the cylinder section is lifted back to the plate rolling machine and rolled again to eliminate the local wave deformation caused by welding. Step Six: The receiving device lifts the entire cylindrical section onto the turning device, and the limiting device tightens the section from both sides; Step 7: Connect the top and side lifting lugs of the turning device to the two cranes respectively. After lifting them off the ground at the same time, one crane remains stationary while the other crane continues to lift, turning the cylinder section from a horizontal position to a vertical position. Step 8: After the turning is completed, lift the vertically positioned cylinder section away from the turning device and assemble and weld it with the adjacent cylinder section.

2. The method according to claim 1, characterized in that, The receiving device is a flat isosceles triangle when viewed from the side. Its top is a lifting beam, and its bottom consists of multiple cantilever receiving support rods arranged in an arc. The two sides of the triangle are formed by stiffening plate assemblies. The lifting beam is equipped with multiple lifting lugs, including a large lug in the center and small lugs distributed in different positions. The lifting point combination can be selected according to the position of the cylinder section's center of gravity. The device has a flip-up hook on the open side, which naturally locks itself during lifting.

3. The method according to claim 2, characterized in that, The lifting beam is equipped with 5 lifting lugs, of which 2 large lifting lugs are located in the middle, and 3 small lifting lugs are located at the left end, 1 / 5 of the right end, and 2 / 5 of the right end, respectively.

4. The method according to claim 1, characterized in that, The welding fixing device is a welding roller frame, which has a power-driven roller at the bottom and baffles on both sides; a track-type gantry frame is provided above the welding roller frame, and an automatic submerged arc welding machine is fixed on the gantry frame.

5. The method according to claim 1, characterized in that, The turning device has a U-shaped structure, including a base, limiting devices on both sides, a top lifting lug, and a side lifting lug; the top is provided with two pairs of flat lifting lugs, and the side is provided with one pair of turning lifting lugs.

6. The method according to claim 1, characterized in that, In step five, the ellipticity of the cylindrical section after rounding is controlled within 5mm.

7. The method according to claim 1, characterized in that, The method is implemented when the workshop hoisting height is ≤10 meters.

8. The method according to claim 1, characterized in that, The wall thickness of the cylindrical section is 30-50 mm, and the material is high-strength steel.

9. The method according to claim 1, characterized in that, According to finite element analysis, the maximum deformation of the receiving device is ≤9mm and the maximum stress is ≤74MPa under the rated lifting load.

10. The method according to claim 1, characterized in that, The method eliminates the need for welding plates, lugs, or cross braces to the cylinder throughout the entire process, enabling code-free operation.

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