A method for controlling welding deformation of a LNG ship liquid cargo tank wafer

Abstract

The present application relates to a kind of LNG ship liquid cargo tank wafer strip welding deformation control method, the method comprises the following steps: first, the hull inner shell is fixed with support, the support includes support panel and support cylinder, the support cylinder is vertically fixed to the support panel;Second step, wafer strip is set in the bottom of support cylinder through round hole and is close to support panel;Third step, special pressing tool is designed, and the whole wafer strip is fixed by using multiple pressing tools;Fourth step, the round hole of wafer strip and the butt joint of support panel contact part are carried out segmented symmetrical back welding and fillet welding;Fifth step, wafer strip is integrally fixed on support, and after welding is completed, remove pressing tool.The control method of the present application can effectively control the deformation of wafer strip during welding, ensure the smooth progress of main tank during installation, ensure the construction quality of LNG ship, and improve the construction efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to LNG ship construction, in particular to a method for controlling the deformation of the LNG ship liquid cargo tank diaphragm strip welding. BACKGROUND

[0002] The NO.96 type LNG ship liquid cargo tank is a containment system composed of two layers of insulation boxes and two layers of diaphragm, wherein the secondary layer box is fixedly contacted to the inner hull of the ship body, and the secondary layer diaphragm is attached to the surface of the secondary layer box; the primary box is installed above the secondary layer diaphragm and fixed by a connecting piece. According to the requirements of the GTT document, the secondary layer is in a negative pressure state (-800 mba) before the installation of the primary box. Under the negative pressure condition, the diaphragm strip on the secondary layer diaphragm film is an important component and is fixed on the support by multi-point welding. The conventional welding technology will cause the deformation of the diaphragm strip, thereby causing the deformation of the diaphragm film, and the deformation of the secondary layer diaphragm film will form obvious wrinkles, which will affect the installation of the primary box. Therefore, the welding deformation of the diaphragm needs to be controlled during the manufacturing and welding process of the containment system to ensure the manufacturing precision. SUMMARY

[0003] The present application aims to overcome the deformation problem of the diaphragm strip welding in the prior art, and provides a method for controlling the welding deformation of the diaphragm strip of the LNG ship liquid cargo tank. The control method can effectively control the welding deformation of the secondary layer diaphragm strip of the LNG ship liquid cargo tank, and ensure the smooth installation of the primary box.

[0004] In order to achieve the above-mentioned application purposes, the technical solutions provided by the present application are as follows:

[0005] A method for controlling the welding deformation of the diaphragm strip of the LNG ship liquid cargo tank, the liquid cargo tank of the LNG ship is a containment system composed of two layers of insulation boxes and two layers of diaphragm films, the secondary layer box is fixedly contacted to the inner hull of the ship body, and the secondary layer diaphragm film is attached to the surface of the secondary layer box. The secondary layer diaphragm film includes a diaphragm strip. The method comprises the following steps:

[0006] Firstly, a support is fixed on the inner hull of the ship body, the support includes a support panel and a support cylinder, and the support cylinder is fixed vertically to the support panel;

[0007] Secondly, a circular hole corresponding to the support cylinder is arranged on the diaphragm strip, the diaphragm strip is sleeved at the bottom of the support cylinder through the circular hole and tightly attached to the support panel, it is confirmed that the automatic welding of the diaphragm strip and the diaphragm film adjacent part is completed, and the lap plate welding is completed and the repair is completed;

[0008] Thirdly, a special pressing tool is designed, which comprises fixing bolts, a fixing ring, reinforcing ribs and a pressing ring. The inner diameter of the fixing ring is larger than the outer diameter of the support cylinder, and the inner diameter of the fixing ring is larger than the inner diameter of the circular hole on the Invar strip. The fixing ring and the pressing ring are parallel and connected by the reinforcing ribs, which form a circular truncated cone structure. The fixing bolts are adjustably arranged on the circumference of the fixing ring. The pressing tool is sleeved on the support cylinder, and the support cylinder is clamped by the fixing ring and the fixing bolts. The pressing ring presses the Invar strip, and the circular hole is inside the pressing ring. The entire Invar strip is fixed on the support by welding the edge of the circular hole to the support panel.

[0009] Fourthly, the circular hole of the Invar strip is symmetrically and sectionally welded to the contact part of the support panel.

[0010] Fifthly, the circular hole position and the support panel are welded multiple times at the pressing tool. The Invar strip is fixed on the support by welding the edge of the circular hole to the support panel. After welding, the pressing tool is removed.

[0011] In the LNG ship liquid cargo tank Invar strip welding deformation control method, the pressing tool is provided with three fixing bolts, which are uniformly and symmetrically distributed on the fixing ring.

[0012] In the LNG ship liquid cargo tank Invar strip welding deformation control method, the end of the fixing bolt is fixed with a rubber skin for protecting the support cylinder.

[0013] In the LNG ship liquid cargo tank Invar strip welding deformation control method, the pressing tool is provided with three reinforcing ribs, which are connected to the fixing ring and the pressing ring and are uniformly distributed in a circle. The connecting part of the reinforcing rib and the fixing ring is staggered with the position of the fixing bolt.

[0014] In the LNG ship liquid cargo tank Invar strip welding deformation control method, the pressing ring of the pressing tool is made of stainless steel, and the bottom of the pressing ring is smooth.

[0015] In the LNG ship liquid cargo tank Invar strip welding deformation control method, after checking that the circular hole of the Invar strip and the welding seam between the support panel are clean and free of foreign matter, the pressing tool is installed on the support cylinder, the pressing tool is pressed tightly, the pressing ring is tightly attached to the Invar strip, and then the fixing bolts are tightened to fix the fixing ring on the support cylinder.

[0016] In the LNG ship liquid cargo tank wafer strip welding deformation control method, the fourth step divides the round hole of the wafer strip and the contact part of the support panel into six welds, and divides the six welds into three pairs of arc welds in pairs, and welds and fixes according to the diagonal welding sequence.

[0017] Based on the above technical solution, the LNG ship liquid cargo tank wafer strip welding deformation control method has the following technical advantages compared with the prior art:

[0018] The LNG ship liquid cargo tank wafer strip welding deformation control method effectively reduces the deformation of the wafer strip in the welding process by designing a special welding auxiliary tool and preparing a special welding sequence, and lays a solid foundation for the smooth installation of the subsequent main tank. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is an operation flow chart of the LNG ship liquid cargo tank wafer strip welding deformation control method of the present application.

[0020] Figure 2 It is a wafer strip welding schematic diagram in the LNG ship liquid cargo tank wafer strip welding deformation control method of the present application.

[0021] Figure 3 It is a structure schematic diagram of the pressing tool in the LNG ship liquid cargo tank wafer strip welding deformation control method of the present application.

[0022] Figure 4 It is a welding sequence schematic diagram in the LNG ship liquid cargo tank wafer strip welding deformation control method of the present application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] On the LNG ship, the liquid cargo tank is a containment system composed of two layers of insulation tanks and two layers of wafer membranes, the secondary tank is fixedly contacted on the inner hull of the ship, and the secondary wafer membrane is attached to the surface of the secondary tank. The secondary wafer membrane includes a wafer strip, and the wafer strip and other components on the wafer membrane are fixed together by welding.

[0025] As shown in Figure 1 The LNG ship liquid cargo tank wafer strip welding deformation control method of the present application comprises the following steps:

[0026] First, a support column is fixed on the inner hull of the ship, which includes a support column panel and a support column cylinder, and the support column cylinder is vertically fixed on the support column panel;

[0027] Second, a round hole corresponding to the support column cylinder is arranged on the invar strip, the invar strip is sleeved on the bottom of the support column cylinder through the round hole and is tightly attached to the support column panel, and the automatic welding of the invar strip and the invar film is completed, the lap plate welding is completed and the repair is completed, and the connection relationship between the invar strip and the support column is as shown in Figure 2 .

[0028] Third, a special pressing tool is designed, and the entire invar strip is pressed and fixed by using a plurality of pressing tools. After checking that the welding seam between the round hole of the invar strip and the support column panel is clean and free of foreign matter, the pressing tool is installed on the support column cylinder, the pressing tool is pressed tightly, the pressing ring 4 is tightly attached to the invar strip, and then the fixing bolt 1 is tightened to fix the fixing ring 2 on the support column cylinder.

[0029] Fourth, the butt welding seam between the round hole of the invar strip and the contact part of the support column panel is segmented and symmetrically retreated and welded; in practice, the contact part of the invar strip and the support column panel is divided into six welding seams, which are divided into three pairs of arc-shaped welding seams in pairs, and are welded and fixed in accordance with the sequence of diagonal welding.

[0030] Fifth, the round hole position and the support column panel are welded multiple times at the pressing tool, the invar strip is fixed on the support column by welding the edge of the round hole and the support column panel, and the pressing tool is removed after welding is completed.

[0031] As shown in Figure 2 , as a core component in the application, the pressing tool structure includes a fixing bolt 1, a fixing ring 2, a reinforcing rib 3 and a pressing ring 4, the inner diameter of the fixing ring 2 is greater than the outer diameter of the support column cylinder, the inner diameter of the fixing ring 2 is greater than the inner diameter of the round hole on the invar strip, the fixing ring 2 and the pressing ring 4 are parallel and connected by a plurality of reinforcing ribs 3, the plurality of reinforcing ribs 3 connect the fixing ring 2 and the pressing ring 4 to form a circular truncated cone structure, and a plurality of the fixing bolts 1 are adjustably arranged on the circumference of the fixing ring 2.

[0032] In use, the pressing tool is sleeved on the support column cylinder, the support column cylinder is clamped by the fixing ring 2 and the fixing bolt 1, the invar strip is pressed by the pressing ring 4, and the round hole is inside the pressing ring 4.

[0033] In the method for controlling the welding deformation of Invar strips in the LNG carrier cargo tank of the present invention, the clamping fixture further includes three fixing bolts 1, which are evenly and symmetrically distributed on the fixing ring 2. A rubber sheet protecting the support cylinder is fixed to the end of each fixing bolt 1. The purpose of the rubber sheet is to protect the support cylinder during tightening. The clamping fixture also includes three reinforcing ribs 3, which connect the fixing ring 2 and the clamping ring 4 and are evenly distributed in a circle. The connection points of the reinforcing ribs 3 and the fixing ring 2 are staggered from the positions of the fixing bolts 1. The clamping ring 4 is made of stainless steel, and its bottom is smooth. The smooth bottom of the clamping ring 4 is designed to protect the Invar strips during the clamping process.

[0034] In the control method of the present invention, the following points should also be noted during the implementation steps:

[0035] 1. Before welding, confirm that the Invar strip automatic welding is completed, and that the repair and lap plate welding is completed.

[0036] 2. Add spot welding to the Invar strip welds as required, with a spot welding distance of 10-15mm.

[0037] 3. Check that the weld seam is clean and free of foreign objects to prevent damage to the Invar strips during the clamping process. Before installing the clamping fixture, install the clamping fixture on the support cylinder, press the fixture firmly so that the clamping ring is close to the Invar strip, and then tighten the fixing bolts.

[0038] 4. Divide the weld seam evenly into 6 segments, according to... Figure 4 The sequence number.

[0039] 5. Weld in sections in the order of 1'-2'-3'-4'-5'-6', using the back-welding method, with an overlap distance of no less than 10mm for each weld section.

[0040] 6. After welding is completed, the clamping fixture can only be removed after cooling.

[0041] The welding deformation method of the present invention can effectively control the deformation of Invar strips during the welding process, ensuring the smooth installation of the main container, guaranteeing the construction quality of LNG ships, and improving construction efficiency.

[0042] Although the above embodiments have provided a specific description of the present invention, it should be understood by those skilled in the art that modifications and improvements can be made based on the disclosure of the present invention without departing from the spirit and scope of the present invention, and such modifications and improvements are all within the spirit and scope of the present invention.

Claims

1. A method for controlling welding deformation of Invar strips in the cargo tank of an LNG carrier, wherein the cargo tank of the LNG carrier is an enclosure system consisting of two layers of insulating boxes and two layers of Invar membranes, the secondary boxes are fixed to the hull of the ship, and the secondary Invar membranes are attached to the surface of the secondary boxes, the secondary Invar membranes including Invar strips, the method comprising the following steps: The first step is to fix a support column to the hull of the ship. The support column includes a support column panel and a support column cylinder, and the support column cylinder is vertically fixed to the support column panel. The second step involves providing a circular hole on the Invar strip that corresponds to the support cylinder. The Invar strip is then fitted through the circular hole to the bottom of the support cylinder and pressed against the support panel. It is confirmed that the automatic welding of the adjacent parts of the Invar strip and the Invar membrane is completed, and the overlapping plate welding is completed and the repair is finished. The third step is to design a special clamping fixture. The clamping fixture structure includes a fixing bolt (1), a fixing ring (2), a reinforcing rib (3), and a clamping ring (4). The inner diameter of the fixing ring (2) is larger than the outer diameter of the support cylinder. The inner diameter of the fixing ring (2) is larger than the inner diameter of the circular hole on the Invar strip. The fixing ring (2) and the clamping ring (4) are parallel and connected by multiple reinforcing ribs (3). The multiple reinforcing ribs (3) connect the fixing ring (2) and the clamping ring (4) to form a frustum-shaped structure. The multiple fixing bolts (1) are adjustablely arranged inward on the circumference of the fixing ring (2). The clamping fixture is fitted on the support cylinder. The support cylinder is clamped by the fixing ring (2) and the fixing bolts (1). The clamping ring (4) clamps the Invar strip so that the circular hole is inside the clamping ring (4). The entire Invar strip is clamped and fixed by multiple clamping fixtures. The fourth step is to perform segmented symmetrical back-welding and wire-adding welding on the contact area between the round hole of the Invar strip and the support panel. Fifth step: Weld the round hole position and the support panel multiple times at the clamping fixture, and fix the Invar strip to the support by welding the edge of the round hole to the support panel. After welding, remove the clamping fixture.

2. The method for controlling welding deformation of Invar strips in LNG carrier cargo tanks according to claim 1, characterized in that, The clamping fixture has three fixing bolts (1), which are evenly and symmetrically distributed on the fixing ring (2).

3. The method for controlling welding deformation of Invar strips in LNG carrier cargo tanks according to claim 2, characterized in that, The end of the fixing bolt (1) is fixed with a rubber sheet to protect the support cylinder.

4. The method for controlling welding deformation of Invar strips in LNG carrier cargo tanks according to claim 2, characterized in that, The clamping fixture has three reinforcing ribs (3). The three reinforcing ribs (3) connect the fixing ring (2) and the clamping ring (4) and are evenly distributed around a circle. The connection between the reinforcing ribs (3) and the fixing ring (2) is offset from the position of the fixing bolt (1).

5. The method for controlling welding deformation of Invar strips in LNG carrier cargo tanks according to claim 1, characterized in that, The clamping ring (4) on the clamping fixture is made of stainless steel, and the bottom of the clamping ring (4) is smooth.

6. The method for controlling welding deformation of Invar strips in LNG carrier cargo tanks according to claim 1, characterized in that, In the third step, after checking that the weld between the round hole of the Invar strip and the support panel is clean and free of foreign matter, the clamping fixture is installed on the support cylinder, and the fixture is pressed tightly so that the clamping ring (4) is close to the Invar strip. Then the fixing bolt (1) is tightened to fix the fixing ring (2) on the support cylinder.

7. The method for controlling welding deformation of Invar strips in LNG carrier cargo tanks according to claim 1, characterized in that, In the fourth step, the contact area between the round hole of the Invar strip and the support panel is divided into six weld seams, which are divided into three pairs of arc-shaped weld seams in pairs, and then welded and fixed in the order of diagonal welding.

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