A CM node control method for the bilge section of an LNG carrier liquid cargo tank

Abstract

The present invention discloses a CM node control method for the bilge section of the liquid cargo tank of an LNG ship, comprising the following steps: Step 1: hoist the inner floor plate onto the frame in the small assembly area, and temporarily fix the inner bottom plate to the frame; Step 2: take the plate edge close to the side of the ship as a reference, measure 190mm in the direction of the midship side, and draw an upper inspection line on the upper surface of the inner bottom plate with this spacing; Step 3: use a right-angle marking tool, take the upper inspection line as a standard, and draw a lower inspection line on the lower surface of the inner bottom plate; Step 4: small group welding; Step 5: in the large assembly area, the sections are closed to form a large assembly; Step 6: the large assembly is welded in sections. According to the assembly process of the bilge section, the present invention adopts different precision inspections for the relevant structures involved in the CM node, timely discovers and corrects structural errors, and avoids the accumulation of various structural errors to the final stage, resulting in substandard assembly precision at the CM node of the bilge section, and a large amount of manual rework.

Description

Technical Field

[0001] The present invention belongs to the technical field of shipbuilding, and in particular relates to a CM node control method for a bilge section of a liquid cargo tank of an LNG ship. Background Art

[0002] As we all know, large LNG ships, which need to carry liquefied natural gas at -163 degrees Celsius, have a core containment system that isolates the outside temperature and ensures that the stored liquefied natural gas is always maintained at -163 degrees Celsius. However, the installation and erection of the containment system is greatly affected by the manufacturing accuracy of the hull sections. The bilge section of the liquid cargo tank is the lowest section in the liquid cargo tank area and also the section with the highest requirements for structural strength and manufacturing accuracy. This type of section mainly involves the CM node area where the inner bottom plate and the inner inclined side plate meet. The CM node control method for this area is mostly to draw inspection lines in the assembly area to detect the construction errors of the inner bottom plate surface. Such a CM node control method cannot monitor the construction accuracy of the inner bottom plate related structures throughout the entire process of segment construction, which often results in the assembly accuracy of the CM node area cannot be adjusted to the specification requirements after the segment is formed, resulting in a lot of rework in the assembly stage and delaying the segment production cycle. Summary of the Invention

[0003] In response to the problems existing in the prior art, the present invention provides a method for controlling the CM nodes of the bilge section of an LNG carrier's liquid cargo tank. The present invention ensures that the structural accuracy at the CM nodes meets the regulatory requirements by performing structural completion measurements on the bilge sections participating in the CM nodes at each assembly stage of the segmented production.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a CM node control method for a bilge section of a liquid cargo tank of an LNG carrier, comprising the following steps:

[0006] Step 1: In the group standing area, hoist the inner floor to the tire frame and temporarily fix the inner bottom plate and the tire frame;

[0007] Step 2: Using the edge of the plate close to the side as a reference, measure 190mm towards the midship side and draw the upper inspection line on the upper surface of the inner bottom plate at this distance;

[0008] Step 3: Use a right-angle marking tool and, using the above inspection line as a standard, draw a lower inspection line on the lower surface of the inner bottom plate corresponding to the position of the upper inspection line;

[0009] Step 4: After the team completes the electric welding, measure the distance between the upper inspection line and the adjacent longitudinal wall to check whether the inner bottom plate components have any welding shrinkage deformation;

[0010] Step 5: In the large assembly area, the sections are folded together to form a large assembly. Before spot welding the sections, use the inner and outer card templates to check whether the inspection line is within the error range. After the assembly is adjusted to a reasonable range, welding can be carried out;

[0011] Step 6. After the large assembly and segment welding is completed, use the external card sample again to check whether the inspection line is within the error range.

[0012] As a preferred technical solution, in step three, the right-angle marking tool includes a first vertical ruler, a second vertical ruler, and a horizontal ruler. The first vertical ruler and the second vertical ruler have the same width and are arranged vertically. The horizontal ruler is arranged at the connection between the first vertical ruler and the second vertical ruler, and the horizontal ruler is perpendicular to the first vertical ruler and the second vertical ruler, respectively.

[0013] As a preferred technical solution, the specific steps for using the right-angle marking tool are as follows:

[0014] S1. Set the right-angle marking tool at the end of the inner bottom plate and align one side edge of the first vertical ruler with the upper inspection line;

[0015] S2. Adjust the edge of the level ruler connected to the second vertical ruler so that it is flush with the upper edge of the inner bottom plate end;

[0016] S3. Use a chalk pencil to mark the lower edge of the inner bottom plate along the edge of the second vertical ruler.

[0017] S4. Repeat steps S1, S2, and S3 to draw another mark point on the other end of the inner bottom plate;

[0018] S5. Connect the two marked points and draw the lower inspection line.

[0019] As a preferred technical solution, the width of the first vertical ruler and the second vertical ruler are both 40 mm.

[0020] As a preferred technical solution, the first vertical ruler, the second vertical ruler, and the horizontal ruler have the same thickness.

[0021] As a preferred technical solution, the tire frame is a horizontal tire frame, including angle steel supports and channel steel edges arranged around the angle steel supports.

[0022] As a preferred technical solution, the material of the channel steel edge is No. 20 channel steel.

[0023] Compared with the existing technology, the present invention has the following technical effects: According to the assembly process of bilge segment construction, the present invention adopts different production accuracy tests for the relevant structures involved in the CM node, from small assembly to large assembly, to promptly discover and correct structural errors, and avoid the accumulation of various structural errors in the final stage, resulting in substandard assembly accuracy at the bilge segment CM node and the need for a large amount of manual rework. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a structural schematic diagram of the right-angle marking tool of the present invention.

[0026] Figure 2 It is a schematic diagram of the inspection line for the individual area inspection of the present invention.

[0027] Figure 3 Schematic diagram of the upper inspection line and the lower inspection line of the independent area of ​​the small group of the present invention.

[0028] Figure 4 It is a schematic diagram of the use of pallets in a large group area of ​​the present invention.

[0029] Figure 5 Schematic diagram of the use of pallets outside the large group area of ​​the present invention.

[0030] The specific descriptions of the accompanying drawings are as follows: inner bottom plate 1, upper inspection line 2, lower inspection line 3, first vertical ruler 11, second vertical ruler 12, horizontal ruler 13, outer card template 21, inner card template 22. DETAILED DESCRIPTION

[0031] In the description of the present invention, it should be understood that the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0032] Example 1

[0033] This embodiment provides a right-angle marking tool, comprising a first vertical ruler 11, a second vertical ruler 12, and a horizontal ruler 13. The first vertical ruler 11 and the second vertical ruler 12 have the same width and are arranged perpendicularly. The horizontal ruler 13 is arranged at the connection between the first vertical ruler 11 and the second vertical ruler 12, and is perpendicular to the first vertical ruler 11 and the second vertical ruler 12. In this embodiment, the first vertical ruler 11 and the second vertical ruler 12 are both 20 mm wide and have the same thickness.

[0034] Example 2

[0035] This embodiment provides a method for controlling CM nodes in a bilge section of a liquid cargo tank of an LNG carrier, the method comprising the following steps:

[0036] Step S11: In the group standing area, hoist the inner bottom plate 1 onto the horizontal frame and temporarily secure it to the frame. The horizontal frame includes angle steel supports and channel steel edges. The channel steel edges are made of No. 20 channel steel to ensure the frame meets the required rigidity and has a smooth surface.

[0037] Step S12: Taking the edge of the plate close to the side as the reference, measure 190mm towards the midship side, and draw an upper inspection line 2 on the upper surface of the inner bottom plate 1 at this distance for the inspection in the group standing stage.

[0038] Step S13: Use the right-angle marking tool to draw the upper inspection line 2 on the lower surface of the inner bottom plate 1 as the lower inspection line 3, which serves as the inspection line for the inner card template 22 to inspect the CM node assembly accuracy after the segmented integral molding.

[0039] The following steps are included in the drawing and setting of the inspection line and the inspection line of the right-angle marking tool:

[0040] Step S21: At the end of the inner bottom plate 1, align the right side of the first vertical ruler 11 with the upper inspection line 2.

[0041] Step S22 , move the other end of the inner bottom plate 1 along the upper inspection line 2 so that the lower edge of the level 13 is flush with the upper edge of the end surface of the inner bottom plate 1 .

[0042] Step S23: Use a stone pencil to draw a mark point along the right side outline of the second vertical ruler 12 at the lower edge of the end surface of the inner bottom plate 1.

[0043] Step S24: Repeat steps S21, S22, and S23 at the other end of the inner bottom plate 1, connect the two points on the lower edge of the end surface of the inner bottom plate 1, and draw the lower inspection line 3.

[0044] Step S14: After the subassembly welding, measure the distance between the upper inspection line 2 and the adjacent longitudinal wall to check for welding shrinkage deformation of the inner floor 1. Due to the welding of longitudinal and transverse members on the inner floor 1, there is a risk of local shrinkage deformation of the inner floor 1 components, which can affect the assembly accuracy of the CM nodes during the large-scale subassembly stage.

[0045] Step S15: In the large assembly area, the segments are folded together to form a large assembly. When the segments are not subjected to welding operations, the inner card template 22 and the outer card template 21 are used to check whether the lower inspection line 3 is within the error range. The assembly is adjusted to a reasonable range before welding.

[0046] Step S16: After the large assembly segment welding is completed, the external card template 21 is used again to check whether the lower inspection line 3 is within the error range. After segment welding, welding shrinkage deformation is likely to occur, and it is necessary to measure again to ensure that it is within the error range.

[0047] Although the above embodiments have been described in detail for the present invention, it should be understood by those skilled in the art that modifications or improvements can be made based on the contents disclosed in the present invention without departing from the spirit and scope of the present invention, and that these modifications and improvements are within the spirit and scope of the present invention.

Claims

1. A CM node control method for the bilge section of an LNG carrier, characterized in that: The following steps are involved: Step 1: In the group standing area, hoist the inner floor to the tire frame and temporarily fix the inner bottom plate and the tire frame; Step 2: Using the edge of the plate close to the side as a reference, measure 190mm towards the midship side and draw the upper inspection line on the upper surface of the inner bottom plate at this distance; Step 3: Use a right-angle marking tool, using the above inspection line as a standard, to draw a lower inspection line on the lower surface of the inner bottom plate corresponding to the position of the upper inspection line; wherein the right-angle marking tool includes a first vertical ruler, a second vertical ruler, and a horizontal ruler, wherein the first vertical ruler and the second vertical ruler have the same width and are arranged vertically, and the horizontal ruler is arranged at the connection between the first vertical ruler and the second vertical ruler, and the horizontal ruler is perpendicular to the first vertical ruler and the second vertical ruler respectively; the specific steps for using the right-angle marking tool are as follows: S1. Set the right-angle marking tool at the end of the inner bottom plate and align one side edge of the first vertical ruler with the upper inspection line; S2. Adjust the edge of the level ruler connected to the second vertical ruler so that it is flush with the upper edge of the inner bottom plate end; S3. Use a chalk pencil to mark the lower edge of the inner bottom plate along the edge of the second vertical ruler. S4. Repeat steps S1, S2, and S3 to draw another mark point on the other end of the inner bottom plate; S5. Connect the two marked points and draw the lower inspection line; Step 4: After the team completes the electric welding, measure the distance between the upper inspection line and the adjacent longitudinal wall to check whether the inner bottom plate components have any welding shrinkage deformation; Step 5: In the large assembly area, the sections are folded together to form a large assembly. Before spot welding the sections, use the inner and outer card templates to check whether the inspection line is within the error range. After the assembly is adjusted to a reasonable range, welding can be carried out; Step 6. After the large assembly and segment welding is completed, use the external card sample again to check whether the inspection line is within the error range.

2. A CM node control method for a bilge section of an LNG carrier according to claim 1, characterized in that: The width of the first vertical ruler and the second vertical ruler are both 40 mm.

3. The CM node control method for the bilge section of an LNG carrier according to claim 1, characterized in that: The first vertical ruler, the second vertical ruler, and the horizontal ruler have the same thickness.

4. The CM node control method for the bilge section of an LNG carrier according to claim 1, characterized in that: The tire frame is a horizontal tire frame, which includes angle steel pillars and channel steel edges arranged around the angle steel pillars.

5. A CM node control method for a bilge section of an LNG carrier according to claim 4, characterized in that: The material of the channel steel edge is No. 20 channel steel.

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