A method for welding a liquid cargo tank head and a tooling applied thereto

Abstract

This application discloses a method for welding the end caps of a liquid cargo tank and the tooling for its application. The welding method for the liquid cargo tank includes: setting up a jig with a support surface that matches the outer circumferential contour of the end cap; assembling and fixing an electrode plate and a temperate plate on the jig, with the equatorial opening of the end cap facing upwards; welding the inner weld of the end cap; setting up a clamping structure to support the equatorial opening edge of the end cap; lifting and flipping the end cap, placing the end cap on the clamping structure; and welding the outer weld of the end cap.

Description

Technical Field

[0001] This application relates to the field of liquid pipe processing technology, and in particular to a method for welding the end caps of a liquid cargo tank and the tooling for its application. Background Technology

[0002] As core equipment for the storage and transportation of clean energy, the safety performance of liquid cargo tanks is directly related to industrial production and people's livelihood. As a key pressure-bearing component of pressure vessels, the manufacturing precision of the end cap is the core prerequisite for the safe operation of the equipment.

[0003] In related technologies, the heads of large LPG / LNG pressure vessels, especially type C cargo tanks, are typically hemispherical. The heads are usually manufactured using a horizontal fabrication process with the equatorial seam as the base surface. On-site construction requires extensive scaffolding and auxiliary equipment both inside and outside the site, resulting in limited construction space. Furthermore, the welding methods, including vertical and overhead welding, are challenging and prone to defects. Secondly, insufficient precision in the positioning components can lead to excessive ellipticity in the assembled heads, failing to meet the stringent requirements for pressure-bearing components. Simultaneously, traditional welding assembly relies heavily on experience, lacking scientific planning of the welding sequence. This can easily cause problems such as localized warping of the heads and stress concentration during welding. Post-weld deformation correction is complex, reducing production efficiency and posing potential safety hazards. Summary of the Invention

[0004] This application aims to at least partially address one of the aforementioned technical problems in the prior art. To this end, embodiments of this application provide a method for welding liquid cargo tank end caps and a tooling for its application, which can improve welding conditions within the end cap, reduce welding difficulty, and thus improve welding quality.

[0005] The first aspect of this application provides a method for welding the end caps of a liquid cargo tank, comprising the following steps:

[0006] A support frame is provided, the support frame having a support surface that matches the outer peripheral contour of the end cap;

[0007] The base plate and temperate plate of the end cap are assembled and fixed on the frame, with the equatorial opening of the end cap facing upwards.

[0008] The inner weld of the welded head;

[0009] A retaining structure is provided, which is used to support the equatorial opening edge of the end cap;

[0010] The end cap is hoisted and flipped, and then placed on the clamping structure.

[0011] The outer weld of the welded head.

[0012] According to an embodiment of the first aspect of this application, the step of laying the jig includes the following steps:

[0013] Draw multiple circumferentially spaced axes on the ground;

[0014] Multiple stake points are determined on each of the aforementioned axes;

[0015] The jig is installed at each of the said pile points, wherein the height of the jig at each of the said pile points is set according to the outer contour shape of the end cap;

[0016] Adjust the angle of the movable ear plate at the top of the column frame so that the movable ear plate on each column adapts to the outer contour angle of the end cap;

[0017] Lock the angle of the movable ear plate.

[0018] According to an embodiment of the first aspect of this application, the step of welding the inner weld of the end cap includes:

[0019] Symmetrical welding of the first gap, wherein the first gap refers to the gap between two adjacent temperate plates;

[0020] The second gap is symmetrically welded, wherein the second gap refers to the gap between the temperate plate and the base plate, and the welding orientation of the second gap is symmetrical about the center of the end cap.

[0021] Symmetrical welding refers to welding simultaneously along at least two welding paths in the same direction, with the welding paths evenly distributed around the head in the circumferential direction.

[0022] According to an embodiment of the first aspect of this application, the second gap includes weld reserving sections located on both sides of the first gap and a continuous section connecting two adjacent weld reserving sections;

[0023] The welding steps for the second gap include:

[0024] The continuous segments were symmetrically welded;

[0025] Weld the aforementioned weld-retaining section.

[0026] According to an embodiment of the first aspect of this application, the length of the weld reserving section is 160mm-240mm.

[0027] According to an embodiment of the first aspect of this application, before welding the inner weld of the end cap, the welding method further includes: providing a support frame on the inner side of the end cap, the support frame including a plurality of support rods extending radially, the plurality of support rods being spaced apart circumferentially, and the ends of the support rods abutting against the inner surface of the end cap.

[0028] According to an embodiment of the first aspect of this application, during assembly of the substrate electrode plate and the temperate plate, the seam between two adjacent temperate plates is misaligned with the jig.

[0029] Secondly, this application also provides a tooling for manufacturing liquid cargo tank heads, including multiple sets of jig sets, which are equally spaced along the circumference. Each set of jig sets includes multiple jigs arranged at radial intervals. The height of the multiple jigs gradually increases from the projection center to the outer periphery so that the support surface of the jig matches the outer periphery contour of the head. The projection center refers to the projection of the center of the head on the ground when the head is placed on the jig.

[0030] The jig frame includes a column and a movable ear plate. The movable ear plate is disposed on the top of the column and is used to support the outer peripheral surface of the end cap. The angle of the movable ear plate relative to the column is adjustable.

[0031] According to an embodiment of the second aspect of this application, the movable ear plate includes a plate body and a first connecting ear that are connected to each other. The plate body is used to connect with the end cap. The top of the column is provided with a second connecting ear. The first connecting ear is provided with a positioning hole. The second connecting ear is provided with a plurality of angled snap-fit ​​holes. The first connecting ear and the second connecting ear are rotatably connected so that the positioning hole is aligned with any of the snap-fit ​​holes. The frame also includes a pin, which is used to insert into the positioning hole and the snap-fit ​​hole to lock the relative angle between the ear plate and the column.

[0032] The central angles of two adjacent frames in each frame group are the same, wherein the central angle refers to the angle formed by the support point of the two adjacent frames on the end cap and the center of the end cap.

[0033] According to an embodiment of the second aspect of this application, the tooling used for manufacturing liquid tank heads further includes a support frame, the support frame including a plurality of support rods extending radially, the plurality of support rods being equally spaced circumferentially, and the ends of the support rods abutting against the inner surface of the head.

[0034] In the above technical solution, the support surface formed by the jig matches the contour of the outer periphery of the end cap, allowing the jig to support the outer periphery of the end cap. This ensures the equatorial opening of the end cap faces upwards, preventing the jig from occupying space inside the end cap. Therefore, sufficient space is available inside the end cap for welding operations. Specifically, vertical welding can be used when welding the gaps between temperate plates, while horizontal welding can be used when welding the gaps between temperate plates and electrode plates. Thus, by rationally setting up the jig, the equatorial opening of the end cap can be placed upwards, providing more operating space inside the end cap and overcoming the limitation of insufficient space inside the end cap. This improves welding conditions, allowing the replacement of overhead welding with vertical, horizontal, or flat welding methods, thereby reducing construction difficulty and improving welding quality and safety. When welding the outer side of the end cap, the supporting and holding function of the clamping structure can fix the opening edge of the end cap, facilitating welding on the outer side of the end cap. After welding the inner and outer sides of the end cap, the requirements for sealing performance and welding performance in end cap manufacturing can be met. Attached Figure Description

[0035] The present application will be further described below with reference to the accompanying drawings and embodiments;

[0036] Figure 1 This is a structural schematic diagram of a liquid cargo tank end cap in related technologies;

[0037] Figure 2 This is a schematic diagram of the welding construction of the inner side of the liquid cargo tank during the fabrication of the liquid cargo tank head in related technologies;

[0038] Figure 3 This is a schematic diagram of the liquid cargo tank head resting on the jig according to an embodiment of this application;

[0039] Figure 4 This is a schematic diagram of the tooling used in the fabrication of liquid cargo tank heads according to an embodiment of this application;

[0040] Figure 5 This is a flowchart of the liquid cargo tank head welding method according to an embodiment of this application;

[0041] Figure 6 This is a flowchart of the process for arranging the jig in the liquid cargo tank head welding method according to an embodiment of this application;

[0042] Figure 7 This is a schematic diagram of the fabrication and welding process of the liquid cargo tank head according to an embodiment of this application;

[0043] Figure 8 This is a top view of the liquid cargo tank head resting on the jig according to an embodiment of this application;

[0044] Figure 9This is the first example of symmetrical welding in the liquid cargo tank head welding method of this application embodiment;

[0045] Figure 10 This is a second example of symmetrical welding in the liquid cargo tank head welding method of this application embodiment;

[0046] Figure 11 This is a third example of symmetrical welding in the liquid cargo tank head welding method of this application embodiment;

[0047] Figure 12 This is a schematic diagram of the structure of the liquid cargo tank head after it has been unfolded along the second gap according to an embodiment of this application;

[0048] Figure 13 This is a schematic diagram of the support frame of the tooling used for welding the end caps of liquid cargo tanks according to an embodiment of this application;

[0049] Figure 14 This is an exploded view of the jig used for welding the head of a liquid cargo tank according to an embodiment of this application;

[0050] Figure 15 This is a schematic diagram of the structure of a jig used in the tooling for welding the end caps of liquid cargo tanks according to an embodiment of this application;

[0051] Figure 16 This is a side view of a jig used in the tooling for welding the end caps of liquid cargo tanks, according to an embodiment of this application.

[0052] Figure 17 This is a schematic diagram of the snap-fit ​​structure of the tooling used for welding the end caps of liquid cargo tanks according to an embodiment of this application;

[0053] Figure 18 This is a schematic diagram of the liquid cargo tank head being lifted, flipped, and placed on the snap-fit ​​structure according to an embodiment of this application.

[0054] Figure label:

[0055] 100. Tire frame; 101. Support surface; 110. Column; 111. Second connecting lug; 1111. Snap-fit ​​hole; 120. Movable lug plate; 121. Plate body; 122. First connecting lug; 1221. Positioning hole; 130. Tire frame assembly; 140. Pin; 160. Brake pad; 170. Bolt;

[0056] 200. End cap; 210. Electrode plate; 220. Temperate zone plate; 230. Equatorial opening; 240. First gap; 250. Second gap; 251. Welding section; 252. Continuous section; 253. T-joint area;

[0057] 300. Holding structure; 310. Pile body; 320. Slot;

[0058] 500. Support frame; 510. Support rod;

[0059] 600, Axis; 610, Pile point. Detailed Implementation

[0060] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0061] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0062] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0063] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0064] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0065] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0066] In related technologies, the head 200 of large LPG / LNG pressure vessels, especially type C cargo tanks, is typically hemispherical. The head 200 is usually manufactured using a horizontal construction process with the equatorial seam as the base surface. Horizontal construction specifically means that the equatorial opening of the head 200 faces downwards. Figure 1 As shown, therefore, during on-site construction, a considerable amount of scaffolding and auxiliary equipment needs to be erected inside and outside the head 200. Typically, the head 200 includes an electrode plate 210 and multiple temperate zone plates 220. The head 200 is obtained by assembling the electrode plate 210 and the multiple temperate zone plates 220 together and welding them to the inner and outer sides. Among these, Figure 1 and Figure 2 Lines with triangular symbols represent welds. Similarly, lines with triangular symbols have the same meaning in other figures of this embodiment; that is, lines with triangular symbols all represent welds, which will not be repeated below. When welding the inner side of the end cap 200, the working space for operators is limited because auxiliary tools such as scaffolding occupy part of the space inside the end cap 200. Figure 2 As shown, the welding method during construction is usually overhead welding. Compared with vertical and horizontal welding, overhead welding is more difficult and therefore more prone to welding defects. Based on this, this application proposes a welding method for fabricating the head 200 of a liquid cargo tank (hereinafter referred to as the welding method), which helps to reduce welding difficulty and improve welding quality. It should be noted that the welding method proposed in this application can be applied not only to the head 200 structure of type C liquid cargo tanks, but also to the welding of other structures with similar hemispherical structures; no specific limitations are made here. The following description will continue to use the head 200 structure of a type C liquid cargo tank as an example.

[0067] The following reference Figures 3 to 5 The first aspect of this embodiment provides a method for welding the end caps of a liquid cargo tank, including the following steps:

[0068] S100, the mounting frame 100 has a support surface 101 that matches the outer peripheral surface contour of the end cap 200;

[0069] S200, Assemble and fix the pole plate 210 and temperate plate 220 of the end cap 200 on the frame 100, with the equatorial opening 230 of the end cap 200 facing upwards.

[0070] S300, inner weld of welding head 200;

[0071] S400, with a clamping structure 300, which is used to support the edge of the equatorial opening 230 of the end cap 200;

[0072] S500, hoist and flip the end cap 200, and place the end cap 200 on the clamping structure 300;

[0073] S600, outer weld of welding head 200.

[0074] By utilizing the support surface 101 formed by the jig 100 that matches the outer peripheral contour of the end cap 200, the jig 100 can support the outer peripheral surface of the end cap 200, and the equatorial opening 230 of the end cap 200 faces upwards. This avoids the jig 100 occupying the space inside the end cap 200, thus providing sufficient space inside the end cap 200 for welding operations. When welding the gaps between the temperate plates 220, a vertical welding method can be used; when welding the gaps between the temperate plates 220 and the electrode plate 210, a horizontal welding method can be used. In some examples, the electrode plate 210 can be formed by splicing multiple plates (e.g., middle plate, side plate, edge plate, etc.), and vertical welding, horizontal welding, or flat welding methods can be used when welding the electrode plate 210. Therefore, in this embodiment, by reasonably setting the jig 100, the equatorial opening 230 of the end cap 200 can be placed upwards. This allows for more operating space inside the end cap 200, overcoming the limitation of insufficient space inside the end cap 200, thereby improving welding conditions and enabling the replacement of overhead welding with vertical, horizontal, or flat welding methods. Figure 7 As shown, this reduces construction difficulty and improves welding quality and construction safety. During welding of the outer side of the end cap 200, the supporting and holding structure 300 secures the opening edge of the end cap 200, facilitating welding of the outer side by construction personnel. After welding the inner and outer sides of the end cap 200 respectively, the requirements for sealing and welding performance in the manufacture of the end cap 200 are met.

[0075] It should be noted that the support surface 101 of the jig 100 refers to the jig 100 having multiple continuous or discretely distributed support points on the outer surface of the head 200, with a curved surface (such as a hemisphere, arc surface, etc.) that allows each support point to lie within the curved surface; this curved surface is the support surface 101 of the jig 100. When the support surface 101 of the jig 100 is matched with the outer peripheral contour of the head 200, the jig 100 can better fit and support itself on the outer peripheral surface of the head 200. It can be understood that, in order to make the equatorial opening 230 of the head 200 face upwards, the jig 100 is arranged with a lower center and higher edges.

[0076] Optionally, since both the inner and outer sides of the end cap 200 require welding, bevels that facilitate welding can be provided on both the inner and outer sides of the electrode plate 210 and the temperate plate 220. The inner and outer bevels can be asymmetrically arranged, specifically, the inner bevel is larger than the outer bevel. This allows for a deeper weld during inner welding, creating a stable foundation and controlling deformation to some extent. After the inner welding is completed, the end cap 200 is hoisted and flipped, and welding is performed on the shallower outer bevel to meet the weld strength requirements. By welding the deep bevel first and then the shallow bevel, a reverse shrinkage force is applied. The two shrinkage forces partially cancel each other out, ultimately achieving a balance and control of overall deformation, resulting in a more uniform stress distribution on the end cap 200.

[0077] Optionally, when assembling and fixing the electrode plate 210 and the temperate plate 220 on the jig 100, in order to prevent the plates from shifting during welding, clamps can be used to fix adjacent plates on the outside of the end cap 200. That is, clamps are set on the splicing gaps of each plate (e.g., between temperate plates 220 and between temperate plates 220 and electrode plate 210). The clamps can fix two adjacent plates and can be removed after welding is completed.

[0078] Optionally, the clamping material is the same as that of the end cap 200. This ensures that the clamping material and the end cap 200 have the same thermal expansion and electrical conductivity, preventing excessive thermal stress and cracking caused by asynchronous shrinkage of the clamping material and the end cap 200 plate during weld cooling. It also ensures that the clamping material has the same structural strength and rigidity as the end cap 200, guaranteeing that the clamping material can effectively fix and support the plate during welding, resisting shrinkage stress generated during welding and preventing misalignment and deformation.

[0079] In some embodiments, please refer to Figures 6 to 8 The above steps S100 and laying the frame 100 also include the following steps:

[0080] S110. Draw multiple 600-degree axes at equal intervals along the circumference on the ground.

[0081] S120. Determine multiple stake points 610 on each axis 600;

[0082] S130, Install a jig 100 at each pile point 610;

[0083] S140, Adjust the angle of the movable ear plate 120 at the top of the upright column 110 of the frame 100, and set the height of the frame 100 on each upright point 610 according to the outer contour shape of the end cap 200;

[0084] S150, lock the movable ear plate at an angle of 120.

[0085] The multiple axes 600, evenly spaced circumferentially, help the end cap 200 achieve uniform support and bearing in the circumferential direction. Similarly, defining multiple anchor points 610 on each axis 600 helps the end cap 200 achieve uniform bearing in the radial direction, thus making the stress on the end cap 200 more uniform, avoiding deformation problems caused by uneven stress during welding, and improving the assembly and forming accuracy of the end cap 200. Since the support points of each jig 100 on the end cap 200 are different, the contact angle between each jig 100 and the end cap 200 is also different. Therefore, setting the movable ear plate 120 to have an adjustable tilt angle helps to better fit the outer contour of the end cap 200 by adjusting the angle of the movable ear plate 120 at different positions, so that the end cap 200 can obtain more uniform support and improve the assembly accuracy of the end cap 200. In addition, by adjusting the angle of the movable ear plates 120 on each jig 100, the curvature of the jig 100 support surface 101 can be adjusted, thereby adapting to the assembly of heads 200 with different diameters and curvatures, meeting the welding requirements of heads 200 of different specifications, and allowing the jig 100 to be reused in different welding tasks, thus improving the versatility of the jig 100. After adjusting the angle of each movable ear plate 120 according to the outer contour shape of the head 200, the angle of the movable ear plate 120 needs to be locked to prevent the movable ear plate 120 from rotating, ensuring that the movable ear plate 120 can stably support the head 200 during the welding process.

[0086] For example, ground marking can be performed using laser marking, which ensures straight lines and good accuracy, reducing errors caused by marking. Optionally, the number of axes 600 can be flexibly set according to the number of temperate zone plates 220, for example, Figure 8 In the end cap 200 shown, the end cap 200 is provided with 6 temperate plates 220, and correspondingly, 12 axes 600 can be drawn. Each temperate plate 220 is supported by 2 sets of jigs 100. Alternatively, in other examples, the number of axes 600 can be 6, 18, etc.

[0087] In some embodiments, please refer to Figures 9 to 11 Step 300, the weld seam on the inner side of the welding head, includes:

[0088] S310, Symmetrically weld the first gap 240, wherein the first gap 240 refers to the gap between two adjacent temperate plates 220;

[0089] S320, symmetrically weld the second gap 250, wherein the second gap 250 refers to the gap between the temperate plate 220 and the electrode plate, and the welding orientation of the second gap 250 is symmetrical about the center of the end cap 200.

[0090] Symmetrical welding refers to welding simultaneously along at least two welding paths in the same direction, with the welding paths evenly distributed circumferentially on the end cap.

[0091] For example, when welding using two welding paths simultaneously, such as Figure 9 As shown, two welders can simultaneously weld the first gap 240. The numbers I and II on the dashed arrows indicate the welding sequence, and arrows with the same number indicate simultaneous welding. When welding simultaneously using three welding paths, the three starting points are equally spaced in the circumferential direction, as shown below. Figure 10 As shown, three welders can simultaneously weld the first gap 240. The numbers I, II, and III on the dashed arrows indicate the welding sequence, and arrows with the same number indicate simultaneous welding. For example, the first gap 240 can be welded from bottom to top, along... Figure 9 Perform vertical welding in the direction of the arrow shown. The second gap 250 can be welded clockwise or counterclockwise, along... Figure 11 As shown, horizontal welding is performed along the direction of the arrow. The numbers IV and V on the dashed arrows indicate the welding sequence, and arrows with the same number indicate simultaneous welding.

[0092] Specifically, "same welding direction" includes ① the direction extending from the electrode plate towards the equatorial plane (all welding paths start from the electrode plate area of ​​the end cap, proceed along the surface of the end cap towards the equatorial plane, such as...). Figure 9 , Figure 10 As shown); ② The extension direction of the circumferential weld (e.g., the second gap 250), in which case all welding paths are along the same circumferential direction, that is, all are clockwise (e.g. Figure 11 (As shown), or all of them are counterclockwise.

[0093] The use of symmetrical welding leverages the principle of force cancellation to help control deformation within a smaller range during the welding process. Specifically, firstly, symmetrical welding reduces angular deformation, preventing the shrinkage force of the first weld from pulling the workpiece to one side and causing significant angular deformation, which is common in sequential welding on one side. Therefore, when both sides are welded symmetrically and simultaneously, the two shrinkage forces are opposite in direction and equal in magnitude, canceling each other out along the central axis of the structure, thus bringing the workpiece closer to equilibrium. Secondly, symmetrical welding reduces residual stress. Simultaneous heating and cooling on both sides ensures more uniform heat input, avoiding uneven expansion and contraction caused by heat concentration on one side. This results in a more symmetrical distribution of residual stress and a significant decrease in stress peaks. These characteristics of symmetrical welding help reduce problems such as local warping, out-of-tolerance ellipticity, angular deformation, and diameter deviation, controlling deformation at its source. This can directly reduce or even eliminate the need for straightening processes, thereby lowering manufacturing costs.

[0094] It should be noted that simultaneous welding does not require multiple welders to operate in perfect synchronization every second. Rather, it means that welders should be evenly distributed and weld synchronously, with the length ahead or behind being too large within the same time frame, thus meeting the synchronization requirement. This means that as long as the welders maintain a basically consistent overall progress, without a significant progress difference where one side is completed while the other is not even halfway done, the requirement of "synchronous welding" can be considered met.

[0095] In some embodiments, please refer to Figure 11 and Figure 12 The second gap 250 includes weld reserving sections 251 located on both sides of the first gap 240 and a continuous section 252 connecting two adjacent weld reserving sections 251. The welding step 320 of the second gap 250 includes:

[0096] S321, Symmetrical welding continuous section 252;

[0097] S322, Welding Retention Section 251.

[0098] The intersection of the first gap 240 and the second gaps 250 on both sides of the first gap 240 forms a T-joint portion 253. When welding the second gaps 250, if the T-joint portion 253 is not avoided, the second gaps 250 will directly pull on the solidified first gap 240 when they cool and shrink. This pulling action creates significant stress on the T-joint portion 253, making it prone to cracking, leading to local angular deformation and misalignment, and compromising the flatness of the curved surface. Therefore, a weld gap 251 is provided at the T-joint portion 253 of the second gap 250. Welding is performed on a portion of the continuous section 252 first, which avoids directly starting and ending the arc at the T-joint portion 253. That is, when welding the second gap 250, welding begins at a certain distance from the T-joint portion 253, and welding continues for a certain distance before stopping when there is still a certain distance between the weld and the T-joint portion 253, thus leaving a gap at the T-joint portion 253. In this way, when the continuous section 252 cools and shrinks, its shrinkage can pull the half that is not yet fully fixed, without directly tearing the already welded first gap 240. After the connecting section of the second gap 250 is completely welded, the stress of the entire head 200 structure can be fully released and redistributed, reducing the risk of cracking. By setting the weld retention section 251, the convergence of the three weld lines at the same point is effectively avoided, thereby eliminating the "rigid node" in the welded structure, reducing the peak value of welding residual stress in this area, helping to reduce the risk of cold cracking, hot cracking and arc crater cracking, and improving the fatigue strength of the weld and the overall structural safety.

[0099] Optionally, the length of the weld retention section 251 is 160mm-240mm. Optionally, the weld retention section 251 can be evenly distributed on both sides of the first gap 240, that is, the second gap 250 can reserve weld retention sections 251 of 80mm-120mm on both sides of the first gap 240 respectively.

[0100] In some embodiments, please refer to Figure 13 Before welding the inside of the welding head 200, the assembly method also includes:

[0101] S700, a support frame 500 is provided on the inner side of the end cap 200. The support frame 500 includes a plurality of support rods 510 extending radially. The plurality of support rods 510 are spaced apart circumferentially, and the ends of the support rods 510 abut against the inner side of the end cap 200.

[0102] By incorporating a support frame 500 within the head 200, with each radial support rod 510 abutting against the inner wall of the corresponding temperate plate 220, this structure provides a forced radial geometric constraint. During welding, this constraint resists the centripetal force generated by weld shrinkage, ensuring the roundness of the head 200 and minimizing angular and wave deformation. Furthermore, the support frame 500 provides a stable reference for plate assembly, guaranteeing the accuracy of the bevel gap and overall dimensions. Ultimately, this configuration helps reduce post-weld straightening work, lowers manufacturing costs, and enhances the load-bearing capacity and structural reliability of the head 200 by ensuring precise geometry.

[0103] In some embodiments, step S200, assembling and fixing the electrode plate 210 and the temperate plate 220 on the jig 100, includes: S201, the seams of two adjacent temperate plates 220 are offset from the jig 100. Since adjacent temperate plates 220 need to be fixed on the outside using clips, when assembling and fixing the temperate plates 220 on the jig 100, the seams of the temperate plates 220 are offset from the jig 100, thus preventing interference between the movable ear plate 120 of the jig 100 and the clips, which would affect the clip fixing. It is understood that when marking and selecting the anchor points 610 of the jig 100, the axis 600 can be positioned offset from the seams of the temperate plates 220, so that the jig 100 can avoid the seams after installation.

[0104] In some embodiments, please refer to Figure 17 and Figure 18 Step S500: Lifting and flipping the end cap 200, placing the end cap 200 on the clamping structure 300, including S510: Installing lifting lugs on the end cap 200, and lifting the end cap 200 to flip it over using the lifting lugs.

[0105] For example, lifting lugs can be welded to the end cap 200. Lifting equipment can connect to the lifting lugs to lift and rotate the end cap 200, so that the equatorial opening 230 of the end cap 200 faces downwards. At this point, the edge of the opening of the end cap 200 can be engaged with the holding structure 300 for fixation. Optionally, multiple holding structures 300 can be arranged circumferentially, with equal intervals between them, to provide uniform support force to the end cap 200. The holding structure 300 may include a pile body 310 and a V-shaped groove 320 disposed on the top of the pile body 310. The edge of the opening of the end cap 200 can be engaged within the V-shaped groove 320, thus enabling precise positioning and fixation of the end cap 200 and preventing displacement during external welding.

[0106] Optionally, before step S600 and welding the outer side of the end cap 200, the weld seam on the outer side of the end cap 200 (e.g., the first gap 240 and the second gap 250) can be cleaned to remove the defect layer at the root of the inner weld seam, such as slag inclusions and porosity, thereby creating a good foundation for the outer welding, enabling the outer weld to penetrate the inner weld seam, ensuring the continuity of the outer welding and obtaining good mechanical properties, thereby ensuring the quality of the outer welding.

[0107] Secondly, please refer to Figure 3 , Figure 4 , Figure 7 and Figure 8 This embodiment provides a tooling for manufacturing a liquid cargo tank end cap 200. The tooling includes multiple sets of jig sets 130, which are equally spaced circumferentially. Each jig set 130 includes multiple jigs 100 arranged radially. The height of the multiple jigs 100 gradually increases from the projection center O' to the outer periphery, so that the support surface 101 of the jig 100 matches the outer periphery contour of the end cap 200. The projection center O' refers to the projection of the center of the end cap 200 on the ground when the end cap 200 is placed on the jig 100. The jig 100 includes a column 110 and a movable ear plate 120. The movable ear plate 120 is disposed on the top of the column 110 and is used to support the outer periphery of the end cap 200. The angle of the movable ear plate 120 relative to the column 110 is adjustable.

[0108] By utilizing the support surface 101 formed by the jig 100 that matches the outer peripheral contour of the end cap 200, the jig 100 can support the outer peripheral surface of the end cap 200, and the equatorial opening 230 of the end cap 200 faces upwards. This avoids the jig 100 occupying the space inside the end cap 200, thus providing sufficient space inside the end cap 200 for welding operations. When welding the gaps between the temperate plates 220, a vertical welding method can be used; when welding the gaps between the temperate plates 220 and the electrode plate 210, a horizontal welding method can be used. In some examples, the electrode plate 210 can be formed by splicing multiple plates (e.g., middle plate, side plate, edge plate, etc.), and vertical welding, horizontal welding, or flat welding methods can be used when welding the electrode plate 210. Therefore, in this embodiment, by rationally setting the jig 100, the equatorial opening 230 of the end cap 200 can be placed upwards. This provides more operating space inside the end cap 200, overcoming the limitation of insufficient space inside the end cap 200, thereby improving welding conditions and allowing the overhead welding method to be replaced by vertical, horizontal, or flat welding methods, thus reducing construction difficulty and improving welding quality and construction safety. When welding the outer side of the end cap 200, the supporting and holding function of the clamping structure 300 can be used to fix the opening edge of the end cap 200, facilitating welding of the outer side of the end cap 200 by construction personnel. After welding the inner and outer sides of the end cap 200 respectively, the requirements for sealing performance and welding performance of the end cap 200 can be met.

[0109] Multiple sets of jig sets 130 are evenly spaced circumferentially, which helps to provide uniform support and bearing for the end cap 200 in the circumferential direction. Similarly, each set of jig sets 130 includes multiple jigs 100 spaced radially, which helps to provide uniform bearing for the end cap 200 in the radial direction. This results in more uniform stress on the end cap 200, avoiding deformation problems caused by uneven stress during welding, and improving the assembly and forming accuracy of the end cap 200. Since the support points of each jig 100 on the end cap 200 are different, the contact angle between each jig 100 and the end cap 200 is also different. Therefore, setting the movable ear plate 120 to have an adjustable tilt angle helps to better fit the outer contour of the end cap 200 by adjusting the angle of the movable ear plate 120 at different positions, so that the end cap 200 can obtain more uniform support and improve the assembly accuracy of the end cap 200. In addition, by adjusting the angle of the movable ear plates 120 on each jig 100, the curvature of the jig 100 support surface 101 can be adjusted, thereby adapting to the assembly of heads 200 with different diameters and curvatures, meeting the welding requirements of heads 200 of different specifications, and allowing the jig 100 to be reused in different welding tasks, thus improving the versatility of the jig 100. After adjusting the angle of each movable ear plate 120 according to the outer contour shape of the head 200, the angle of the movable ear plate 120 needs to be locked to prevent the movable ear plate 120 from rotating, ensuring that the movable ear plate 120 can stably support the head 200 during the welding process.

[0110] In some embodiments, please refer to Figures 14 to 16The movable ear plate 120 includes a plate body 121 and a first connecting ear 122 connected to each other. The plate body 121 is used to connect with the end cap 200. The top of the column 110 is provided with a second connecting ear 111. The first connecting ear 122 is provided with a positioning hole 1221. The second connecting ear 111 is provided with a plurality of angled snap-fit ​​holes 1111. The first connecting ear 122 and the second connecting ear 111 are rotatably connected so that the positioning hole 1221 is aligned with any one of the snap-fit ​​holes 1111. The jig 100 also includes a pin 140, which is used to insert into the positioning hole 1221 and the snap-fit ​​hole 1111 to lock the relative angle between the ear plate and the column 110. The central angle α of two adjacent jigs 100 in each jig group 130 is the same. The central angle α refers to the angle formed by the support point of the two adjacent jigs 100 on the end cap 200 and the center of the end cap 200. The angle of the movable ear plate 120 can be adjusted by the relative rotation of the first connecting ear 122 and the second connecting ear 111. Since the second connecting ear 111 has multiple locking holes 1111, the plate 121 can have different tilt angles when the positioning hole 1221 is aligned with different locking holes 1111. The pin 140 simultaneously passes through both the locking hole 1111 and the positioning hole 1221, locking the relative movement of the first and second ear plates, thereby locking the angle of the ear plates. This central arrangement makes the angle adjustment of the movable ear plate 120 easy to achieve and simplifies the angle adjustment operation. The central angle α of two adjacent jigs 100 within the jig group 130 set on the same axis 600 is the same. This means that the angle change rate of the movable ear plate 120 on the jig 100 is the same. For example, if the central angle α formed between two adjacent jigs 100 is 10°, then the angle difference of the movable ear plate 120 between two adjacent jigs 100 is 10°. This helps to make the jigs 100 evenly distributed on the same circumference, providing uniform support for the end cap 200, and also simplifies the angle adjustment operation of the movable ear plate 120.

[0111] Optionally, two second connecting ears 111 can be arranged parallel to each other at the top of the column 110. A first connecting ear 122 is rotatably disposed in the gap between the two second connecting ears 111. The first connecting ear 122 and the two second connecting ears 111 are connected by a bolt 170, so that the first connecting ear 122 can rotate relative to the second connecting ear 111 with the bolt 170 as an axis. A brake pad 160 can also be provided on the outside of the second connection. When the pin 140 is inserted into the snap-fit ​​hole 1111 and the positioning hole 1221, it can abut against the brake pad 160. The brake pad 160 can increase the friction between the first connecting ear 122 and the second connecting ear 111, preventing the movable ear plate 120 from sliding or rotating when locked, and improving the stability and reliability of the locking of the movable ear plate 120.

[0112] In some embodiments, please refer to Figure 13The tooling used in the fabrication of the liquid tank head 200 also includes a support frame 500. The support frame 500 comprises multiple radially extending support rods 510, which are evenly spaced circumferentially. The ends of the support rods 510 abut against the inner surface of the head 200. By installing the support frame 500 inside the head 200, each radially arranged support rod 510 abuts against the inner wall of the corresponding temperate plate 220. This structure, on the one hand, creates a forced radial geometric constraint, resisting the centripetal force generated by weld shrinkage during welding, ensuring the roundness of the head 200, and controlling angular deformation and waviness to a minimum. On the other hand, the support frame 500 provides a stable reference for plate assembly, ensuring the accuracy of the bevel gap and overall dimensions. Ultimately, this arrangement helps reduce post-weld straightening work, lowers manufacturing costs, and improves the pressure-bearing capacity and structural reliability of the head 200 by ensuring precise geometry.

[0113] Optionally, the number of support rods 510 can correspond to the number of temperate plates 220, for example, in a one-to-one correspondence or in multiples thereof. Figure 13 The end cap 200 shown includes 6 temperate plates 220. Therefore, the support frame 500 can be provided with 6 support rods 510, which are arranged in a star pattern, or 3 or 12 support rods 510, or multiple support rods 510 are arranged radially.

[0114] Optionally, the support frame 500 can adopt a detachable or adjustable structure. For example, the number and spacing of the support rods 510 can be flexibly adjusted according to the number of temperate plates 220, so that the support frame 500 has better flexibility and adaptability. After the end cap 200 is welded, the support frame 500 can be easily disassembled and recycled, realizing the reuse of the support structure.

[0115] In some embodiments, please refer to Figure 17 and Figure 18After the inner welding of the end cap 200 is completed, it needs to be flipped using lifting equipment so that the opening of the end cap 200 faces downwards. At this time, a clamping structure 300 can be used to support the end cap 200. Specifically, the tooling used in the fabrication of the liquid cargo tank end cap 200 also includes clamping structures 300 arranged at equal intervals along the circumference. The clamping structure 300 has a groove 320 for engaging the opening edge of the end cap 200. The lifting equipment can be connected to lifting lugs to lift and flip the end cap 200 so that the equatorial opening 230 of the end cap 200 faces downwards. At this time, the opening edge of the end cap 200 can be engaged with the clamping structure 300 for fixation. The arrangement of multiple clamping structures 300 along the circumference at equal intervals provides uniform support force to the end cap 200. The holding structure 300 may include a pile body 310 and a V-shaped groove 320 provided on the top of the pile body 310. The opening edge of the end cap 200 can be engaged in the V-shaped groove 320, so that the end cap 200 can be accurately positioned and fixed, avoiding displacement during the welding process on the outside.

[0116] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

Claims

1. A method for welding the end caps of a liquid cargo tank, characterized in that, Includes the following steps: A support frame is provided, the support frame having a support surface that matches the outer peripheral contour of the end cap; The end cap's electrode plate and temperate plate are assembled and fixed on the jig, with the equatorial opening of the end cap facing upwards. The inner weld of the welded head; A retaining structure is provided, which is used to support the equatorial opening edge of the end cap; The end cap is hoisted and flipped, and then placed on the clamping structure. The outer weld of the welded head.

2. The method for welding the C-type liquid cargo tank head according to claim 1, characterized in that, The steps for setting up the frame include: Draw multiple circumferentially spaced axes on the ground; Multiple stake points are determined on each of the aforementioned axes; The jig is installed at each of the said pile points, wherein the height of the jig at each of the said pile points is set according to the outer contour shape of the end cap; Adjust the angle of the movable ear plate on the top of the tire frame so that each movable ear plate adapts to the outer contour angle of the end cap; Lock the angle of the movable ear plate.

3. The method for welding the end caps of a liquid cargo tank according to claim 1, characterized in that, The steps for welding the inner side of the end cap include: Symmetrical welding of the first gap, wherein the first gap refers to the gap between two adjacent temperate plates; The second gap is symmetrically welded, wherein the second gap refers to the gap between the temperate plate and the electrode plate, and the welding orientation of the second gap is symmetrical about the center of the head. Symmetrical welding refers to welding simultaneously along at least two welding paths with the same welding direction, and the welding paths are evenly distributed circumferentially on the end cap.

4. The method for welding the end caps of a liquid cargo tank according to claim 3, characterized in that, The second gap includes weld receptacles located on both sides of the first gap and a continuous segment connecting two adjacent weld receptacles; wherein, the welding steps for the second gap include: The continuous segments were symmetrically welded; Weld the aforementioned weld-retaining section.

5. The method for welding the end caps of a liquid cargo tank according to claim 4, characterized in that, The length of the weld retention section is 160mm-240mm.

6. The method for welding the end caps of a liquid cargo tank according to claim 1, characterized in that, Before welding the inner weld of the end cap, the liquid cargo tank end cap welding method further includes: setting a support frame on the inner side of the end cap, the support frame including a plurality of support rods extending radially, the plurality of support rods being spaced apart circumferentially, and the ends of the support rods abutting against the inner surface of the end cap.

7. The method for welding the end caps of a liquid cargo tank according to claim 1, characterized in that, During assembly of the electrode plate and the temperate plate, the seam between two adjacent temperate plates is misaligned with the jig frame.

8. A tooling for manufacturing liquid cargo tank heads, characterized in that, It includes multiple sets of jig sets, which are equally spaced along the circumference. Each set of jig sets includes multiple jigs that are spaced along the radial direction. The height of the multiple jigs gradually increases from the projection center to the outer periphery so that the support surface of the jig matches the outer periphery of the end cap. The projection center refers to the projection of the center of the end cap on the ground when the end cap is placed on the jig. The jig frame includes a column and a movable ear plate. The movable ear plate is disposed on the top of the column and is used to support the outer peripheral surface of the end cap. The angle of the movable ear plate relative to the column is adjustable.

9. The tooling for manufacturing liquid cargo tank heads according to claim 8, characterized in that, The movable ear plate includes an interconnected plate body and a first connecting ear. The plate body is used to connect with the end cap. The top of the column is provided with a second connecting ear. The first connecting ear is provided with a positioning hole. The second connecting ear is provided with a plurality of angled snap-fit ​​holes. The first connecting ear and the second connecting ear are rotatably connected so that the positioning hole is aligned with any of the snap-fit ​​holes. The frame also includes a pin. The pin is used to insert into the positioning hole and the snap-fit ​​hole to lock the relative angle between the ear plate and the column. The central angles of two adjacent frames in each frame group are the same, wherein the central angle refers to the angle formed by the support point of the two adjacent frames on the end cap and the center of the end cap.

10. The tooling for manufacturing liquid cargo tank heads according to claim 9, characterized in that, The tooling used for manufacturing liquid cargo tank heads also includes a support frame, which includes multiple support rods extending radially and spaced equally in the circumferential direction. The ends of the support rods abut against the inner surface of the tank head.

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