Underwater fillet weld local dry method welding device
By designing the local dry welding device for underwater fillet welds, using multi-layer multi-channel fillet welding technology and modular structure, the problem of fillet weld maintenance is solved, and efficient welding is achieved without emptying water sources, which is improved. Welding quality and safety are suitable for the remote maintenance needs of the nuclear power industry.
Patent Information
- Application Number
- CN202411407640.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-10
- Publication Date
- 2024-12-27
AI Technical Summary
Existing underwater welding technology is difficult to effectively repair the fillet weld structure, especially in the safety and quality problems in the absence of emptied water sources and nuclear power radioactive environments, and remote repairs cannot be achieved.
A local dry welding device for underwater fillet welds was designed, and the multi-layer multi-channel fillet welding technology was used to achieve efficient welding of fillet welds through sealing materials and modular structures, including rotating modules, AVC modules and walking modules. Ensure the multi-angle adjustment and movement of the welding gun head, combined with the sealing material and the hatch mechanism, and realize the partial dry welding of the underwater corner weld.
It realizes efficient welding of diagonal welds without emptying water sources, expands the maintenance scope, improves welding quality and safety, is suitable for the pool maintenance needs of the nuclear power industry, and has the ability to remote maintenance.
Smart Images
Figure CN119187766A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of welding, and in particular relates to an underwater fillet weld local dry welding device. Background Art
[0002] As the service time increases, many underwater facility structures will have defects such as pitting and cracks, which affect the safety of the facilities. For example, during the service of nuclear power pool structures, due to high radiation and residual stress in welds, stress corrosion cracking is prone to occur, causing liquid leakage in the pool and requiring repair. At present, the welding repair method for underwater defects often uses frogman underwater wet welding or underwater dry welding. During wet welding, there is water around the arc, which makes the welding visibility poor, the hydrogen content of the weld is high, and the welding quality is poor, which is difficult to meet the requirements. Underwater dry welding requires that all the water in the pool be drained, and then the defects are repaired by manual welding, but it is not applicable to some structures that are difficult to drain water, and there are certain risks in manual welding in the radioactive environment of nuclear power. Underwater local dry welding technology can improve welding quality without draining the water source, and this method can achieve remote maintenance, which is suitable for water pool maintenance in the nuclear power industry.
[0003] After searching for relevant patents, Harbin Institute of Technology (Weihai) invented a device and welding method for underwater local dry welding, but it can only be used for welding of planar structures and cannot be used in corner weld structures. Shanghai Nuclear Engineering Research and Design Institute Co., Ltd. proposed a local dry welding device and method for the corner areas of underwater facilities. The main body consists of an upper shell, a lower shell and a watertight welding device. The lower shell and the corner area are prevented from forming a closed space, and the upper shell and the lower shell are slidably connected to realize the welding process. Beijing University of Petrochemical Technology proposed a multifunctional underwater TIG arc repair welding drainage device and repair method. The drainage cover body is connected to the motion platform to realize drainage and welding functions. Summary of the invention
[0004] The purpose of the present invention is to provide an underwater fillet weld local dry welding device, which is suitable for underwater remote maintenance of fillet welds, and expands the maintenance range through multi-layer and multi-pass filler wire surfacing to ensure that the repair of the defective area of the fillet weld is completed.
[0005] In order to achieve the above object, the technical solution adopted by the present invention is:
[0006] A local dry welding device for underwater fillet welds, wherein sealing materials are fixed on the bottom surface and side walls of a drainage cover, including the lower bottom surface and side walls in contact with the fillet weld structure and the outer edges of the lower bottom surface and the side walls, a cable air pipe joint and a welding gun cable joint are installed on the upper surface of the drainage cover, a No. 1 air inlet pipe is fixed along the sealing materials on the side walls, and a No. 2 air inlet pipe, a No. 1 drainage pipe, a No. 2 drainage pipe and an endoscope tube are fixed along the sealing materials on the bottom surface; a fixed bracket is fixed on the inner wall of the drainage cover, a walking module motor and a walking module are installed on the fixed bracket, an AVC module is connected and fixed to the walking module, an OSC module is installed at the front end of the AVC module, the OSC module is connected to a rotating module and a rotating module motor, and the rotating module is connected to a welding gun head, The welding gun head is connected to the vision module, and the wire feeding nozzle is fixed on the vision module; the hatch fixing device is installed on the inner wall of the drainage cover body, the front end of the hatch fixing device is connected to the downward pressure cylinder, the forward push cylinder fixing plate is fixed on the inner wall of the drainage cover body, and is connected to the forward push cylinder, the forward push cylinder and the downward pressure cylinder are connected through a hinge block, the hatch body is fixed at the front of the downward pressure cylinder, a hatch through hole is installed on the hatch of the hatch body, and a hatch sealing material filling groove is fixed on the outer surface of the hatch body, the forward push cylinder lifts the downward pressure cylinder when working through the hinge block, and adjusts the angle of the hatch body at the same time, and then pushes the hatch body toward the opening area on the drainage cover body through the downward pressure cylinder, and the sealing material in the hatch sealing material filling groove contacts with the drainage cover body to achieve sealing at the hatch.
[0007] The sealing material is silicone.
[0008] The sealing material is a sealed, watertight and compressible sealing material.
[0009] The welding gun head is connected to the vision module through a fixing plate.
[0010] The walking module enables the welding gun head to move along the length direction of the drainage cover body; the rotating module and the AVC module are adjusted to enable the welding gun head to align with different welding positions.
[0011] The AVC module realizes the feeding movement of the welding gun head, that is, completes the movement of the welding gun head extending out or retracting into the drainage cover body, thereby achieving the effect of preparing for welding and stopping welding.
[0012] The OSC module enables the welding gun head to swing in a plane perpendicular to the welding direction, optimizing the weld formation effect.
[0013] The rotating module realizes the rotating movement of the welding gun head in a plane perpendicular to the welding direction, that is, completes the adjustment of the welding angle, thereby achieving the effect of improving the multi-layer and multi-pass welding forming.
[0014] The front end of the door fixing device is connected to the downward pressure cylinder through a hinge, and the forward push cylinder fixing plate is connected to the forward push cylinder through a hinge.
[0015] S1. With the hatch closed, fix the underwater fillet weld local dry welding device to the position to be welded, and press along the bottom and wall of the fillet weld to deform the sealing material and isolate the external water source. At this time, the hatch through hole is closed, and air is ventilated to the inside of the drainage cover through the cable air pipe joint to balance the internal air pressure with the external underwater pressure;
[0016] S2, supply air to the No. 1 air inlet pipe and the No. 2 air inlet pipe to discharge the water in the area of the fillet weld to be welded, so that the water in the area is discharged along the No. 1 drainage pipe and the No. 2 drainage pipe, and observe whether it is drained through an endoscope. If it is drained, proceed to the next step;
[0017] S3. Open the hatch through hole on the hatch body to balance the air pressure inside the drainage cover with the air pressure in the area to be welded, retract the forward cylinder and the downward cylinder, open the hatch and bring it close to the inner wall of the drainage cover, move the welding device to the hatch door area through the walking module, and further observe through the visual module, and adjust the walking module, AVC module, and rotating module to align the welding gun head with the area to be welded at a suitable welding angle;
[0018] S4, jointly control the walking module, AVC module, and OSC module, the filling wire passes through the wire feeding nozzle to reach the welding area, and the underwater local dry filling welding is completed; after completing a weld seam, the welding gun head returns to the position before welding;
[0019] S5. Adjust the rotation module and the AVC module to change the welding gun head from the highest angle welding position to the middle angle welding position. The adjustment angle of the welding position is adjusted according to the size of the welding area of the fillet weld to achieve multi-layer and multi-pass welding.
[0020] S6. Repeat steps S4 and S5 to complete the multi-layer and multi-pass welding of the entire weld, then retract the welding device, close the hatch to seal the internal space of the drainage cover, and finally drain the water from the entire device.
[0021] The beneficial effects achieved by the present invention are:
[0022] The present invention arranges sealing materials (the sealing materials are compressible and impermeable, such as silicone materials) around the area to be welded along the outside of the drainage cover body to isolate the welding area from the external water source, and then inflates the drainage to form an underwater sealing area, thereby realizing local dry welding of the underwater corner weld structure.
[0023] The welding mechanism of the present invention is equipped with a rotating module and an AVC module, which can realize the adjustment of the welding angle and welding height of the welding gun, thereby realizing multi-layer and multi-pass welding of underwater corner weld structures, so that the welding area covers a larger corner weld area.
[0024] In addition to being arranged around the area to be welded, the sealing material of the present invention is also arranged on the outer edge lines of the lower bottom surface and the side wall surface to ensure that the drainage cover body does not tilt or shift during the pressing process along the wall surface and the bottom surface, so that the sealing material deforms more evenly to ensure the sealing effect and welding effect.
[0025] The present invention has an air inlet and an air outlet on the upper part of the drainage cover body, and gas is introduced during the welding process to remove the smoke generated by the welding, thereby preventing the smoke from accumulating in the drainage cover body, so as to facilitate the observation of the welding process through a visual module.
[0026] The present invention designs a hatch through hole on the hatch, and the hole can be manually controlled to be closed and opened. Before the hatch is opened, the hatch through hole is opened first to make the air pressure in the hatch space the same as the air pressure in the external welding area, thereby preventing water backflow caused by a sudden change in air pressure when the hatch is opened.
[0027] The welding device of the present invention comprises AVC and OSC modules, which can realize automatic adjustment and automatic swing of arc voltage during welding, so as to achieve better welding effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 It is a schematic diagram of the drainage cover structure of an underwater fillet weld local dry welding device;
[0029] Figure 2 It is a schematic diagram of the bottom structure of a drainage cover of an underwater fillet weld local dry welding device;
[0030] Figure 3 It is a structural schematic diagram of a local dry welding device for underwater fillet welds;
[0031] Figure 4 It is a schematic diagram of a hatch mechanism of an underwater fillet weld local dry welding device;
[0032] Figure 5 A schematic diagram of welding positions of a local dry welding device for underwater fillet welds;
[0033] In the figure: 1. Drain cover, 2. No. 1 air inlet pipe, 3. Cable air pipe connector, 4. Endoscope tube, 5. No. 1 drain pipe, 6. No. 2 air inlet pipe, 7. No. 2 drain pipe, 8. Sealing material, 9. Welding gun cable connector, 10. Fixed bracket, 11. Walking module motor, 12. Walking module, 13. AVC module, 14. OSC module, 15. Rotation module motor, 16. Rotation module, 17. Welding gun head, 18. Wire feeding nozzle, 19. Vision module, 20. Door fixing device, 21. Forward push cylinder, 22. Downward pressure cylinder, 23. Door sealing material filling groove, 24. Door through hole, 25. Door body, 26. Forward push cylinder fixing plate, 27. Articulated block, 101. Middle angle welding position, 102. Highest angle welding position. DETAILED DESCRIPTION
[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.
[0035] An underwater fillet weld local dry welding device, the drainage cover structure includes a drainage cover body 1 and a sealing material 8, the sealing material 8 can be silica gel, or other sealed and watertight but compressible sealing materials. The sealing material 8 is fixed on the bottom surface and side wall of the drainage cover body 1, including the lower bottom surface and side wall surface in contact with the fillet weld structure and the outer edge of the lower bottom surface and the side wall surface, see Figure 1 and Figure 2 The upper surface of the drainage cover 1 is installed with a cable air pipe joint 3 and a welding gun cable joint 9. A No. 1 air inlet pipe 2 is fixed along the sealing material 8 on the side wall, and a No. 2 air inlet pipe 6, a No. 1 drainage pipe 5, a No. 2 drainage pipe 7 and an endoscope tube 4 are fixed along the sealing material 8 on the bottom surface.
[0036] The welding device is fixed on the inner wall of the drainage cover 1 through a fixed bracket 10, the walking module motor 11 and the walking module 12 are installed on the fixed bracket 10, the AVC module 13 is connected and fixed to the walking module 12, the front end of the AVC module 13 is installed with the OSC module 14, the OSC module 14 is connected to the rotating module 16 and the rotating module motor 15, the rotating module 16 is connected to the welding gun head 17, the welding gun head 17 is connected to the visual module 19 through a fixed plate, and the wire feeder 18 is fixed on the visual module 19. It should be noted that the above connection is to meet the welding movement requirements of the welding device, and can also be achieved by adjusting the connection sequence between the modules. The walking module 12 realizes the movement of the welding gun head 17 along the length direction of the drainage cover, that is, the welding movement can be completed. The AVC module 13 realizes the feeding movement of the welding gun head 17, that is, the action of the welding gun head 17 extending or retracting the drainage cover 1 is completed, so as to achieve the effect of preparing for welding and stopping welding. The OSC module 14 realizes the swing of the welding gun head 17 in a plane perpendicular to the welding direction to optimize the weld forming effect. The rotating module 16 realizes the rotating movement of the welding gun head 17 in a plane perpendicular to the welding direction, that is, completes the adjustment of the welding angle, thereby achieving the effect of improving the multi-layer and multi-pass welding forming.
[0037] The hatch device is composed of a hatch fixing device 20, a forward thrust cylinder 21, a downward pressure cylinder 22 and a hatch body 25. The hatch fixing device 20 is installed on the inner wall of the drainage cover 1, and the front end of the hatch fixing device is connected to the downward pressure cylinder 22 by a hinge. The forward thrust cylinder fixing plate 26 is fixed to the inner wall of the drainage cover 1 and is connected to the forward thrust cylinder 21 by a hinge. The forward thrust cylinder 21 is connected to the downward pressure cylinder 22 by a hinge block 27. The hatch body 25 is fixed to the front of the downward pressure cylinder 22. A hatch through hole 24 is installed on the hatch of the hatch body 25. The hole can be manually controlled to open and close by a solenoid valve or the like. A layer of hatch sealing material filling groove 23 is fixed on the outer surface of the hatch body 25. The forward thrust cylinder 21 lifts the downward thrust cylinder 22 when working through the hinge block 27, and at the same time adjusts the angle of the hatch body 25, and then pushes the hatch body 25 toward the opening area on the drainage cover body 1 through the downward thrust cylinder 22. The sealing material in the hatch sealing material filling groove 23 contacts the drainage cover body 1 to achieve sealing at the hatch. When the hatch needs to be removed, only reverse work is required.
[0038] By adjusting the rotation module 16 and the AVC module 13 , the welding gun head 17 can be aligned with different welding positions, such as the highest angle welding position 102 and the middle angle welding position 101 .
[0039] The present invention also provides a method for local dry welding of underwater fillet welds, the specific implementation steps of which include:
[0040] S1. With the hatch closed, fix the underwater fillet weld local dry welding device to the position to be welded, and press along the bottom and wall of the fillet weld to deform the sealing material 8 and isolate the external water source. It should be noted that at this time, the hatch through hole 24 is closed, and air is ventilated to the inside of the drainage cover 1 through the cable air pipe joint 3, so that the internal air pressure is basically balanced with the external underwater pressure;
[0041] S2, supply air to the No. 1 air inlet pipe 2 and the No. 2 air inlet pipe 6 to discharge the water in the area of the fillet weld to be welded, so that the water in the area is discharged along the No. 1 drainage pipe 5 and the No. 2 drainage pipe 7, and observe whether it is drained through an endoscope. If it is drained, the next step can be carried out;
[0042] S3, open the hatch through hole 24 on the hatch body 25, balance the air pressure inside the drainage cover 1 with the air pressure in the area to be welded, retract the forward cylinder 21 and the downward cylinder 22, open the hatch and bring it close to the inner wall of the drainage cover, move the welding device to the hatch door area through the walking module, and further observe through the visual module 19, and adjust the walking module 12, the AVC module 13, and the rotating module 16 to align the welding gun head 17 with the area to be welded at a suitable welding angle;
[0043] S4, jointly control the walking module 12, the AVC module 13, and the OSC module 14, the filling wire passes through the wire feeding nozzle 18 to reach the welding area, and the underwater local dry filling welding is completed; after completing a weld seam welding, the welding gun head returns to the position before welding;
[0044] S5. Adjust the rotation module 16 and the AVC module 13 to change the welding gun head 17 from the highest angle welding position 102 to the middle angle welding position 101. The adjustment angle of the welding position can be adjusted according to the size of the welding area of the fillet weld to achieve multi-layer and multi-pass welding. The size of the welding angle can be determined according to the welding process.
[0045] S6. Repeat steps S4 and S5 to complete the multi-layer and multi-pass welding of the entire weld, then retract the welding device, close the hatch to seal the internal space of the drainage cover, and finally drain the water from the entire device.
[0046] The present invention provides an underwater fillet weld local dry welding device, comprising a drainage cover, a hatch mechanism and a welding device. The drainage cover is connected to the hatch mechanism, when the hatch is closed, the interior of the drainage cover is sealed, and when the hatch is opened, the welding device moves to the hatch position for welding.
[0047] Furthermore, sealing materials are arranged along the lower bottom surface and side wall surfaces of the drainage cover body in contact with the fillet weld structure, and the arrangement area includes the periphery of the hatch and the outer edges of the lower bottom surface and the side wall surfaces.
[0048] Furthermore, two groups of air intake pipes, two groups of drainage pipes and an endoscope are inserted in the silicone material around the hatch. The two groups of air intake pipes are arranged on the silicone above the hatch and on the bottom of the hatch respectively; the two groups of drainage pipes are arranged on the silicone at the bottom of the hatch and in contact with the bottom surface. The endoscope is arranged on the silicone inside the drainage pipe and opposite to the air intake pipe.
[0049] Furthermore, holes are respectively opened on both end surfaces of the upper part of the drainage cover, and the hole far from the welding area and the hole close to the welding area are used as air inlet holes and smoke exhaust holes respectively. The top surface of the drainage cover is equipped with air pipeline holes.
[0050] Further, the hatch mechanism is composed of a hatch top plate, a forward push cylinder, and a downward pressure cylinder, and the hatch top plate is adapted to the drainage cover body. The forward push cylinder and the downward pressure cylinder are used to realize the advancement and retreat of the hatch top plate.
[0051] Furthermore, the welding mechanism is composed of a walking module, an AVC module, an OSC module, a rotating module, a welding gun, a visual module, and a wire feeding module. The walking module is fixed on the drainage cover, and the forward and backward movement of the welding mechanism is realized by the guide rail. The AVC module is fixed on the walking module, the OSC module is installed on the AVC module, the rotating module is installed in front of the OSC module, and the welding gun, the visual module and the wire feeding module are fixed in front of the rotating module.
[0052] The present invention provides an underwater fillet weld local dry welding method, using the above-mentioned underwater fillet weld local dry welding device, comprising the following steps:
[0053] Step one: fold up the welding mechanism and close the hatch, fill the closed drainage cover with gas to make the internal air pressure the same as the water pressure, and at the same time move and fix the underwater corner weld local dry welding device to the defect, and press it along the wall and bottom surface, and achieve sealing by deformation of the sealing material.
[0054] Step 2: Inflate the two groups of air inlet pipes to drain the water in the fillet weld area outward along the drain pipe, and observe the drainage effect through an endoscope until the water in the area to be welded is drained;
[0055] Step three, adjust the two sets of cylinders of the hatch mechanism to open the hatch, and retract the hatch top plate to the rear of the drainage cover. The walking module moves the welding gun to the area to be welded, and adjust the AVC and rotating module to align the welding gun with the arc starting position at a suitable angle.
[0056] Step 4: arc welding, the walking module realizes welding movement, the AVC module conditions the welding height, the OSC module realizes welding swing, the wire feeding module realizes filling wire, the visual module is used to observe the welding process, and air is inflated, water is drained and smoke is exhausted while welding.
[0057] Step 5. After welding is completed, the welding gun returns to the arc starting position, and the rotation module and AVC module are adjusted to change the welding angle, and then step 4 is repeated to achieve multi-pass welding.
[0058] Step 6. After all welding is completed, put away the welding gun and close the hatch, and discharge the water from the equipment while the internal mechanism is in a sealed condition.
Claims
1. An underwater fillet weld local dry welding device, characterized in that: The sealing material is fixed on the bottom surface and side wall of the drainage cover body, including the lower bottom surface and side wall surface in contact with the fillet weld structure and the outer edge line of the lower bottom surface and the side wall surface; the upper surface of the drainage cover body is installed with a cable air pipe joint and a welding gun cable joint; the No. 1 air inlet pipe is fixed along the sealing material on the side wall; the No. 2 air inlet pipe, the No. 1 drain pipe, the No. 2 drain pipe and the endoscope tube are fixed along the sealing material on the bottom surface; the fixed bracket is fixed on the inner wall of the drainage cover body, the walking module motor and the walking module are installed on the fixed bracket, the AVC module is connected and fixed to the walking module, the OSC module is installed at the front end of the AVC module, the OSC module is connected to the rotating module and the rotating module motor, the rotating module is connected to the welding gun head, and the welding gun head is connected to the visual module The block is connected, and the wire feeding nozzle is fixed on the visual module; the hatch fixing device is installed on the inner wall of the drainage cover body, the front end of the hatch fixing device is connected to the downward pressure cylinder, the forward push cylinder fixing plate is fixed on the inner wall of the drainage cover body and connected to the forward push cylinder, the forward push cylinder and the downward pressure cylinder are connected through a hinge block, the hatch body is fixed at the front of the downward pressure cylinder, a hatch through hole is installed on the hatch of the hatch body, and a hatch sealing material filling groove is fixed on the outer surface of the hatch body, the forward push cylinder lifts the downward pressure cylinder when working through the hinge block, and adjusts the angle of the hatch body at the same time, and then pushes the hatch body toward the opening area on the drainage cover body through the downward pressure cylinder, and the sealing material in the hatch sealing material filling groove contacts with the drainage cover body to achieve sealing at the hatch.
2. The underwater fillet weld local dry welding device according to claim 1, characterized in that: The sealing material is silicone.
3. The underwater fillet weld local dry welding device according to claim 1, characterized in that: The sealing material is a sealed, watertight and compressible sealing material.
4. The underwater fillet weld local dry welding device according to claim 1, characterized in that: The welding gun head is connected to the vision module through a fixing plate.
5. The underwater fillet weld local dry welding device according to claim 1, characterized in that: The walking module enables the welding gun head to move along the length direction of the drainage cover body; the rotating module and the AVC module are adjusted to enable the welding gun head to align with different welding positions.
6. The underwater fillet weld local dry welding device according to claim 1, characterized in that: The AVC module realizes the feeding movement of the welding gun head, that is, completes the movement of the welding gun head extending out or retracting into the drainage cover body, thereby achieving the effect of preparing for welding and stopping welding.
7. The underwater fillet weld local dry welding device according to claim 1, characterized in that: The OSC module enables the welding gun head to swing in a plane perpendicular to the welding direction, optimizing the weld formation effect.
8. The underwater fillet weld local dry welding device according to claim 1, characterized in that: The rotating module realizes the rotating movement of the welding gun head in a plane perpendicular to the welding direction, that is, completes the adjustment of the welding angle, thereby achieving the effect of improving the multi-layer and multi-pass welding forming.
9. The underwater fillet weld local dry welding device according to claim 1, characterized in that: The front end of the door fixing device is connected to the downward pressure cylinder through a hinge, and the forward push cylinder fixing plate is connected to the forward push cylinder through a hinge.
10. The underwater fillet weld local dry welding device according to claim 1, characterized in that: S1. With the hatch closed, fix the underwater fillet weld local dry welding device to the position to be welded, and press along the bottom and wall of the fillet weld to deform the sealing material and isolate the external water source. At this time, the hatch through hole is closed, and air is ventilated to the inside of the drainage cover through the cable air pipe joint to balance the internal air pressure with the external underwater pressure; S2, supply air to the No. 1 air inlet pipe and the No. 2 air inlet pipe to discharge the water in the area of the fillet weld to be welded, so that the water in the area is discharged along the No. 1 drainage pipe and the No. 2 drainage pipe, and observe whether it is drained through an endoscope. If it is drained, proceed to the next step; S3. Open the hatch through hole on the hatch body to balance the air pressure inside the drainage cover with the air pressure in the area to be welded, retract the forward cylinder and the downward cylinder, open the hatch and bring it close to the inner wall of the drainage cover, move the welding device to the hatch door area through the walking module, and further observe through the visual module, and adjust the walking module, AVC module, and rotating module to align the welding gun head with the area to be welded at a suitable welding angle; S4, jointly control the walking module, AVC module, and OSC module, the filling wire passes through the wire feeding nozzle to reach the welding area, and the underwater local dry filling welding is completed; after completing a weld seam, the welding gun head returns to the position before welding; S5. Adjust the rotation module and the AVC module to change the welding gun head from the highest angle welding position to the middle angle welding position. The adjustment angle of the welding position is adjusted according to the size of the welding area of the fillet weld to achieve multi-layer and multi-pass welding. S6. Repeat steps S4 and S5 to complete the multi-layer and multi-pass welding of the entire weld, then retract the welding device, close the hatch to seal the internal space of the drainage cover, and finally drain the water from the entire device.