A method for controlling the lifting accuracy of the top full-beam section of an LNG bunkering vessel

Abstract

This invention discloses a method for controlling the lifting accuracy of the full-width section of the top of an LNG bunkering vessel. The method specifically includes the following steps: S1, establishing a finite element model of the full-width section and determining its center of gravity; S2, setting lifting rings on the full-width section based on the determined center of gravity; S3, performing finite element analysis on the full-width section to determine the location for constraint welding; S4, pre-setting support columns at the corresponding rib positions on the top of the B-type tank; S5, lifting the full-width section, performing constraint welding, and removing the pre-set support columns on the top of the B-type tank, thus completing the lifting of the full-width section. This invention improves lifting accuracy by determining the lifting ring positions through finite element analysis, calculating the deformation after hook release based on finite element calculations, pre-setting support columns, and finally performing hook release and reinforcement removal under pre-set constraint welding conditions.

Description

Technical Field

[0001] This invention belongs to the field of shipbuilding technology, specifically relating to a method for controlling the hoisting accuracy of the full-width top section of an LNG bunkering vessel. Background Technology

[0002] During the construction of LNG bunkering vessels, the top section needs to be hoisted into the B-type tank in the cargo hold before it is loaded. However, the surface covering material of the B-type tank is flammable, so the amount of open flame work should be minimized during the top section construction.

[0003] To minimize empty ship weight and maximize deadweight, LNG bunkering vessels typically feature a single-hull deck with triangular compartments on either side serving as ballast tanks. To meet the fire safety requirements of Type B compartments, the deck sections and the triangular compartment sections are assembled into a full-width top section. However, due to the single-hull design, the overall strength of this deck section is relatively weak, leading to significant deformation during lifting and undock release. Without proper control, this can result in serious problems such as the section failing to be properly installed, large-scale deck deformation, and water accumulation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for controlling the lifting accuracy of the full-width section of the top of an LNG bunkering vessel. This invention determines the position of the lifting rings through finite element analysis, controls the deformation during the lifting process of the section, calculates the deformation after the hook is released based on finite element analysis, performs anti-deformation addition by pre-setting supports, and finally releases and removes the hooks under preset constraint welding conditions, so that the deformation of the section is controlled within the accuracy requirements.

[0005] To achieve the above-mentioned objectives, the technical solution provided by this invention patent is as follows:

[0006] A method for controlling the lifting accuracy of the full-width top section of an LNG bunkering vessel, the method specifically includes the following steps:

[0007] S1. Establish a finite element model for the top full-width section and perform finite element analysis on the top full-width section; determine the centroid position of the top full-width section based on the finite element analysis results.

[0008] S2, Based on the determined center of gravity position of the top full-width section, set up lifting rings for the top full-width section, and perform weight load analysis on the lifting rings to determine whether the lifting ring positions meet the requirements;

[0009] S3, perform finite element analysis on the top full-width section to determine the location for constraint welding on the top full-width section;

[0010] S4. Based on the deformation obtained from the finite element analysis of the loose hook of the top full-width section, before hoisting the top full-width section, pre-set the supporting columns at the corresponding rib positions on the top of the B-type cabin.

[0011] S5, hoist the top full-width section. After hoisting, perform constraint welding on the top full-width section and remove the pre-installed support columns on the top of the B-type cabin to complete the hoisting of the top full-width section.

[0012] Furthermore, the establishment of the finite element model for the full-width top section is specifically as follows: A finite element model of the full-width top section is established using MSC / Patran software. The finite element mesh size is set to two meshes per rib along the ship's length direction, and two meshes are set per longitudinal girder spacing in the ship's beam direction. All plates in the finite element model are planar plates. Shell elements are used for the plates, longitudinal girder, and web of the strong transverse beams. Beam elements are used to simulate the transverse and longitudinal bulb flats. The material selected is ordinary carbon steel with a density of 7850 kg / m³. 3 The three-dimensional coordinate system adopts a right-handed coordinate system, with the X-axis pointing towards the bow, the Z-axis pointing upwards, and the Y-axis pointing towards the port side.

[0013] Furthermore, the lifting ring positions of the top full-width section are arranged as follows: the lifting rings are arranged front and back on the 3rd, 6th, 9th and 12th solid ribs from the stern to the bow of the top full-width section, and the lifting rings on the solid ribs are arranged symmetrically front and back; the lifting rings are set left and right on the upper diagonal side and on the strong longitudinal rib, and the left and right lifting rings are symmetrical and located at the strong frame.

[0014] Furthermore, the constraint welds are installed at both ends of the triangular cabin ribs, with one constraint weld installed every other section.

[0015] Furthermore, the height of the pre-set support cylinder at the top of the B-type cabin is the sum of the distance between the top full-width section and the top of the B-type cabin and the deformation of the top full-width section.

[0016] Based on the above technical solution, the method for controlling the hoisting accuracy of the full-width top section of an LNG bunkering vessel, as described in this invention patent, has achieved the following technical advantages through practical application:

[0017] 1. The present invention provides a method for controlling the lifting accuracy of the full-width section of the top of an LNG bunkering vessel. This method uses finite element analysis to determine the position of the lifting rings, controls the deformation during the lifting process, calculates the deformation after unhooking based on finite element analysis, adds counter-deformation support by pre-setting supports, and finally unhooks and reinforces the dismantling under pre-set constraint welding conditions, so that the deformation of the section is controlled within the accuracy requirements. Attached Figure Description

[0018] Figure 1 This is a diagram showing the arrangement of lifting rings for the top full-width section in the method for controlling the lifting accuracy of the top full-width section of an LNG bunkering vessel according to the present invention.

[0019] Figure 2 This is a diagram showing the constraint welding arrangement of the top full-width section in the method for controlling the hoisting accuracy of the top full-width section of an LNG bunkering vessel according to the present invention.

[0020] Figure 3 This is a diagram showing the arrangement of supporting cylinders in a method for controlling the lifting accuracy of the full-width section of the top of an LNG bunkering vessel according to the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific examples shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0022] This invention not only enables the pre-outfitting integrity of sections and overall sections, greatly reducing the outfitting workload in the engine room and bilge area during the dock construction phase, and improving the dock working environment and safe production environment, but also eliminates the interference between the structure and outfitting in the original dock hoisting process, thereby significantly improving the efficiency of section hoisting and further shortening the dock construction cycle.

[0023] like Figure 1-3 The present invention pertains to a method for controlling the lifting accuracy of the full-width section of the top of an LNG bunkering vessel, and the method specifically includes the following steps:

[0024] S1. Establish a finite element model for the top full-width section and perform finite element analysis on the top full-width section; determine the centroid position of the top full-width section based on the finite element analysis results.

[0025] S2, Based on the determined center of gravity position of the top full-width section, set up lifting ring 1 for the top full-width section, and perform weight load analysis on the lifting ring 1 to determine whether the position of lifting ring 1 meets the requirements;

[0026] S3, perform finite element analysis on the top full-width section to determine the position of the constraint weld 2 on the top full-width section;

[0027] S4. Based on the deformation obtained from the finite element analysis of the top full-width section, before hoisting the top full-width section, pre-set the support cylinder 3 at the corresponding rib position on the top of the B-type cabin.

[0028] S5, hoist the top full-width section. After hoisting, perform constraint welding 2 on the top full-width section and remove the pre-set support column 3 on the top of the B-type cabin to complete the hoisting of the top full-width section.

[0029] The establishment of the finite element model for the full-width top section is specifically as follows: A finite element model of the full-width top section is established using MSC / Patran software. Two finite element meshes are set for each rib along the ship's length, and two meshes are set for each longitudinal girder spacing along the ship's width. All plates in the finite element model are planar plates. Shell elements are used for the plates, longitudinal girder, and web of the strong transverse beams. Beam elements are used to simulate the transverse and longitudinal bulb flats. Ordinary carbon steel with a density of 7850 kg / m³ is selected as the material. 3 The three-dimensional coordinate system adopts a right-handed coordinate system, with the X-axis pointing towards the bow, the Z-axis pointing upwards, and the Y-axis pointing towards the port side.

[0030] The position arrangement of the lifting ring 1 of the top full-width section is as follows: the lifting ring 1 is arranged front and back on the 3rd, 6th, 9th and 12th solid ribs from the stern to the bow of the top full-width section, and the lifting ring 1 on the solid ribs is arranged symmetrically front and back; the lifting ring 1 is set on the upper diagonal side and the strong longitudinal bone, and the left and right lifting ring 1 are symmetrical and located at the strong frame.

[0031] The lifting rings 1 are positioned according to the center of gravity of the full-width top section. The lifting rings 1 are arranged symmetrically front to back and left to right, with the distance between them as uniform as possible to ensure even stress distribution and controllable deformation during section lifting. Based on these principles, the lifting rings 1 are positioned on the 3rd, 6th, 9th, and 12th solid ribs from stern to bow, ensuring symmetry between the front and rear lifting points and the center of gravity. The left and right lifting points are located on L8 and L11 longitudinal ribs on the upper diagonal side, symmetrically positioned within the strong frame to minimize lifting deformation. The total weight of this section is 209.6T. Assuming the section is stationary during lifting, the load in the strength analysis is calculated based on the section weight. The total weight of the section is defined by applying an inertial load, with the inertial load taken as 'a' in the depth direction. z =g = 9.8Kg m / s 2 The boundary constraints of the finite element model are selected on the nodes at the lifting ring 1 position, and translational constraints are applied. The left rear lifting ring 1 node is subject to translational constraints in three directions <0,0,0>, the left front lifting ring 1 node is subject to translational constraints in two directions <,0,0>, and the other lifting ring 1 nodes are subject to translational constraints in the Z direction <,,0>. After analysis, the results show that the maximum deformation is 4.32mm and the maximum stress is 49.1MPa. The lifting state meets the accuracy requirements.

[0032] The constraint weld 2 is set at both ends of the triangular cabin rib plate, with one constraint weld 2 set every other section.

[0033] Because the overall strength of the main section is relatively weak, it will deform significantly after the hook is released. Therefore, constraint weld 2 is set at both ends of the triangular cabin rib, with one constraint weld 2 placed every other section, to maximize the lateral and longitudinal bending resistance of the main section. Accordingly, an inertial load is applied to the finite element model of the main section to define the weight of the main section. The inertial load is taken as 'a' in the depth direction. z =g = 9.8Kg m / s 2 The remaining directions are 0; all nodes subjected to constraint welding 2 are fully constrained in six degrees of translation and rotation. Under these boundary conditions, a finite element analysis of the unhooking section is performed. The results show that the longitudinal section of the section experiences the largest deformation, exhibiting a sinking state, with values ​​ranging from 7mm to 12mm. The maximum stress in the section is 111MPa, indicating that all deformations are elastic. If this deformation is not corrected, it will cause consequences such as deck water accumulation and non-compliance of the clearance between the deck and the B-type compartment after the section is unhooked.

[0034] The height of the pre-set support cylinder 3 on the top of the B-type cabin is the sum of the distance between the top full-width section and the top of the B-type cabin and the deformation of the top full-width section.

[0035] The main section is hoisted to its theoretical position for positioning. After positioning, constraint welding 2 is carried out according to the drawings of the main section constraint welding 2. After all construction is completed, the deck reverse support column 3 is removed. At this time, due to its own weight and the influence of constraint welding 2, the main section deck levelness approaches the theoretical value, while the overall dimensions are guaranteed to be within the accuracy requirements.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for controlling the lifting accuracy of the full-width top section of an LNG bunkering vessel, characterized in that, The method specifically includes the following steps: S1. Establish a finite element model for the top full-width section and perform finite element analysis on the top full-width section; determine the centroid position of the top full-width section based on the finite element analysis results. S2, Based on the determined center of gravity position of the top full-width section, set up lifting rings for the top full-width section, and perform weight load analysis on the lifting rings to determine whether the lifting ring positions meet the requirements; S3, perform finite element analysis on the top full-width section to determine the location for constraint welding on the top full-width section; The constraint welds are installed at both ends of the triangular cabin ribs, with one constraint weld installed every other section. S4. Based on the deformation obtained from the finite element analysis of the loose hook of the top full-width section, before hoisting the top full-width section, pre-set the supporting columns at the corresponding rib positions on the top of the B-type cabin. S5, hoist the top full-width section. After hoisting, perform constraint welding on the top full-width section and remove the pre-installed support columns on the top of the B-type cabin to complete the hoisting of the top full-width section.

2. The method for controlling the lifting accuracy of the full-width top section of an LNG bunkering vessel according to claim 1, characterized in that, The establishment of the finite element model for the full-width top section is specifically as follows: A finite element model of the full-width top section is established using MSC / Patran software. Two finite element meshes are set for each rib along the ship's length, and two meshes are set for each longitudinal girder spacing along the ship's width. All plates in the finite element model are planar plates. Shell elements are used for the plates, longitudinal girder, and web of the strong transverse beams. Beam elements are used to simulate the transverse and longitudinal bulb flats. Ordinary carbon steel with a density of 7850 kg / m³ is selected as the material. 3 The three-dimensional coordinate system adopts a right-handed coordinate system, with the X-axis pointing towards the bow, the Z-axis pointing upwards, and the Y-axis pointing towards the port side.

3. The method for controlling the lifting accuracy of the full-width top section of an LNG bunkering vessel according to claim 1, characterized in that, The lifting ring positions of the top full-width section are arranged as follows: the lifting rings are arranged front and back on the 3rd, 6th, 9th and 12th solid ribs from the stern to the bow of the top full-width section, and the lifting rings on the solid ribs are arranged symmetrically front and back; the lifting rings are set left and right on the upper diagonal side and on the strong longitudinal rib, and the left and right lifting rings are symmetrical and located at the strong frame.

4. The method for controlling the lifting accuracy of the top full-width section of an LNG bunkering vessel according to claim 1, characterized in that, The height of the pre-set support cylinder at the top of the B-type cabin is the sum of the distance between the top full-width section and the top of the B-type cabin and the deformation of the top full-width section.

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