Pipeline welding method

Abstract

The invention provides a pipeline welding method. The pipeline welding method comprises the steps that the welding ends of two welding pipes are pretreated; the welding ends of the two welding pipes are oppositely arranged, and an assembling gap is formed between the two welding ends; a plugging tool is provided, the plugging tool comprises two plugging sponges, an exhaust pipe and an exhaust valve, the two plugging sponges are installed in the two welding pipes correspondingly and are arranged close to the welding ends, so that an inflation area is formed on the peripheral side of the assembling gap, one end of the exhaust pipe is connected with one of the plugging sponges, and the other end of the exhaust pipe is connected with the other plugging sponge; the other end of the exhaust pipe is arranged outside the inflation area and is connected with the exhaust valve; and an inflation tool is provided, the inflation tool penetrates through the other blocking sponge to stretch into the inflation area, the inflation area is filled with nitrogen, the welding ends of the two welding pipes are welded when air in the inflation area is exhausted, and when the two welding ends are to be folded, the exhaust valve is opened. According to the method, the gas consumption is reduced, and the production efficiency and the welding quality are improved.

Description

Technical Field

[0001] The invention relates to the field of ship pipeline welding, and in particular to a pipeline welding method. Background Art

[0002] Liquid cargo system pipelines are the basis for ensuring the performance and stable operation of liquefied gas ships. During the welding construction of liquid cargo system pipelines, flange docking is not allowed for pipe connection, and pipe-to-pipe welding is required for assembly. At present, liquid cargo system pipelines are mainly constructed by argon arc welding, and argon gas needs to be filled into the pipes during welding. Due to the large number of liquid cargo system pipelines and some single pipelines running from the bow to the stern, the gas consumption increases significantly during welding. Summary of the invention

[0003] In view of the above-mentioned shortcomings of the related art, an object of the present invention is to provide a pipeline welding method for reducing gas consumption during welding and improving welding quality.

[0004] To achieve the above-mentioned object and other related objects, the present invention provides a pipeline welding method, the method comprising the steps of:

[0005] Pre-treating the welding ends of the two welded pipes;

[0006] The welding ends of the two welding pipes are arranged opposite to each other and an assembly gap is provided between the two welding ends;

[0007] A plugging tool is provided, the plugging tool comprising two plugging sponges, an exhaust pipe and an exhaust valve, the two plugging sponges are respectively installed in two welding pipes and arranged near the welding ends to form an inflation area around the assembly gap, one end of the exhaust pipe is connected to one of the plugging sponges, and the other end of the exhaust pipe is arranged outside the inflation area and connected to the exhaust valve;

[0008] Provide an inflation tool, pass the inflation tool through another sealing sponge to extend into the inflation area, fill the inflation area with nitrogen, and weld the welding ends of the two welding pipes when the air in the inflation area is exhausted. When the two welding ends are about to close, open the exhaust valve.

[0009] Optionally, the specific steps of pre-treating the welding ends of the two welded pipes include:

[0010] Perform groove processing on the welding ends of the two welded pipes respectively;

[0011] Clean both welding ends.

[0012] Optionally, the groove type is a V-shaped groove, and the single-side angle of the groove is 30°±1°.

[0013] Optionally, the step of cleaning the two welding ends includes: polishing the pipe walls on both sides of the welding end and wiping the welding seam area with acetone.

[0014] Optionally, the step of arranging the welding ends of the two welded pipes relative to each other and setting an assembly gap between the two welding ends includes: providing an inlay iron and a horse plate, inserting the inlay iron into the two welded pipes for positioning, and removing the inlay iron after positioning, and using the horse plate to weld and fix the two welded pipes.

[0015] Optionally, the plugging tool further includes two steel plates, which are respectively connected to the two plugging sponges. When the two plugging sponges are respectively installed in the two welding pipes, the two steel plates are respectively placed on the opposite sides of the two plugging sponges.

[0016] Optionally, the inflation tooling includes an inflation tank, an inflation tube and an inflation head, the inflation tube is used to connect the inflation tank and the inflation head, the inflation head is arranged in the inflation area, and a plurality of small ventilation holes are opened on the inflation head.

[0017] Optionally, when welding the welding ends of two welding pipes, a layer-by-layer welding method is adopted to fill the assembly gap between the two welding ends.

[0018] Optionally, the welding order of each layer is: first weld upward from the six o'clock position to the three o'clock position; then weld upward from the six o'clock position to the nine o'clock position; then weld upward from the three o'clock position to the twelve o'clock position; and finally weld upward from the nine o'clock position to the twelve o'clock position.

[0019] Optionally, the temperature during welding is controlled below 100°C.

[0020] As described above, the pipeline welding method of the present invention has the following beneficial effects: the present invention can reduce the space for filling nitrogen by arranging two plugging sponges in two welding pipes, and the gas filling area is enclosed by using the plugging sponges so that the gas can quickly fill the gas filling area, thereby improving the filling efficiency of nitrogen, improving the production schedule requirements, shortening the construction period, and saving the cost of nitrogen use. In addition, the forming quality of the weld can be improved by using nitrogen protective gas for welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Shown is a schematic flow chart of a pipeline welding method according to an embodiment of the present invention.

[0022] Figure 2 It shows a schematic diagram of the arrangement of the inflation tool and the sealing tool during welding in an embodiment of the present invention.

[0023] Figure 3 Shown is a schematic diagram of an inflatable tooling in an embodiment of the present invention.

[0024] Figure 4 It is a schematic diagram showing the locations of the four-layer welds in an embodiment of the present invention.

[0025] Figure 5 It is a schematic diagram showing the welding sequence of the welded pipe in an embodiment of the present invention.

[0026] Component number description

[0027] 1. Sealing sponge; 2. Inflatable tank; 3. Inflatable tube; 4. Inflatable head; 41. Breathing hole; 5. Exhaust valve. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.

[0030] For ease of description, spatial relational terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatial relational terms are intended to include other directions of the device in use or operation in addition to the directions depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can be one or more intervening layers. As used herein, "between..." means including the end point values.

[0031] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0032] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0033] like Figure 1 As shown, this embodiment provides a pipeline welding method, which is used to weld two stainless steel welded pipes, and the opposite ends of the two welded pipes are welding ends.

[0034] The specific steps of this method include:

[0035] S1. Pre-treat the welding ends of the two welded pipes.

[0036] In order to weld two welded pipes together and ensure the welding degree, the welding ends of the two welded pipes are firstly grooved. The groove type of this embodiment adopts a V-shaped groove, wherein the single-side angle of the groove is 30°±1°, where the single-side angle of the groove refers to the angle between the inclined slope surface on the welded pipe and the vertical direction.

[0037] Then the two welding ends are cleaned. Specifically, the pipe walls on both sides of the welding end are polished and the welding seam area is cleaned with acetone. Impurities such as rust can be removed by polishing the pipe wall, and dirt such as oil can be removed by wiping the welding seam area, so as to ensure the strength of the welding. In this embodiment, the polishing distance on the pipe wall is at least 30 mm.

[0038] S2. The welding ends of the two welding pipes are arranged opposite to each other and an assembly gap is provided between the two welding ends.

[0039] Specifically, an embedded iron and a horse plate are provided, wherein there is one embedded iron and multiple horse plates. The embedded iron is a columnar structure, and the embedded iron is passed through two welded pipes for positioning. An assembly gap of 3.5mm-4mm is reserved between the welding ends of the two welded pipes. At this time, the two welded pipes meet the concentricity requirements under the action of the embedded iron.

[0040] After positioning, the two welded pipes are removed from the embedded iron and fixed with horse plates. Specifically, multiple horse plates are welded at intervals along the circumference of the welded pipes. The horse plates are made of stainless steel and have dimensions of 3mm thickness, 30mm-40mm width, and 80mm length.

[0041] S3. Provide a plugging tool, which includes two plugging sponges 1, an exhaust pipe and an exhaust valve 5. The two plugging sponges 1 are respectively installed in two welding pipes and arranged near the welding ends to form an inflation area around the assembly gap. One end of the exhaust pipe is connected to one of the plugging sponges 1, and the other end of the exhaust pipe is arranged outside the inflation area and connected to the exhaust valve 5. Figure 2 shown.

[0042] After welding is completed, the blocking sponge 1 needs to be taken out. In order to facilitate the removal of the blocking sponge 1 from the welded tube, a steel plate is connected to one side of the blocking sponge 1. When two blocking sponges 1 are installed in two welded tubes, the two steel plates are located on the opposite sides of the two blocking sponges 1. By connecting the blocking sponge 1 to a steel plate, the blocking sponge 1 is not easily dragged and damaged when taking out the blocking sponge 1.

[0043] In this embodiment, the diameter of the sealing sponge 1 is larger than the inner diameter of the welding pipe, and the inner diameter of the welding pipe is larger than the diameter of the steel plate. When installing the sealing sponge 1, the sealing sponge 1 can be compressed and then placed in the welding pipe. At this time, the sealing sponge 1 expands to seal the welding end.

[0044] In this embodiment, the distance between the two sealing sponges 1 is 1m. By arranging two sealing sponges 1 in two welded pipes, the space for filling nitrogen can be reduced. By using the sealing sponges 1 to enclose an inflation area, the gas can quickly fill the inflation area, thereby improving the nitrogen filling efficiency, improving the production progress requirements, shortening the construction period, and saving the nitrogen use cost.

[0045] In addition, by using sponge for plugging, the sponge material has a certain air permeability. When the weld is about to close during welding, the excess gas in the inflation area can be discharged through the plugging sponge 1. If the gas exhaust speed through the plugging sponge 1 is slow, the exhaust valve 5 can be opened to quickly discharge the excess gas from the inflation area to reduce the pressure in the inflation area.

[0046] S4. Provide an inflation tool, pass the inflation tool through another plugging sponge 1 to extend into the inflation area, fill the inflation area with nitrogen, and weld the welding ends of the two welding pipes when the air in the inflation area is exhausted. When the two welding ends are about to close, open the exhaust valve.

[0047] like Figure 2 and Figure 3 As shown, the inflating tool includes an inflating tank 2, an inflating tube 3 and an inflating head 4. The inflating tube 3 is used to connect the inflating tank 2 and the inflating head 4. The inflating head 4 is arranged in the inflating area. The inflating head 4 is a columnar structure. A plurality of air holes 41 are provided on the inflating head 4. The diameter of the air holes 41 in this embodiment is 3mm-4mm. When filling with nitrogen, the gas flow rate of nitrogen is 20-25L / min, and the flow rate of nitrogen can be determined according to the actual working conditions.

[0048] In order to connect the inflation tooling with the blocking sponge 1, a through hole is opened in the steel plate connected to the blocking sponge 1, and the size of the through hole can be adapted to the inflation tube 3, so that the inflation tube 3 can pass through the through hole to be connected with the inflation head 4 in the inflation area, or the size of the through hole can be adapted to the inflation head 4, so that the inflation head 4 can be inserted and fixed in the through hole, and the inflation head 4 extends into the inflation area away from the end of the inflation tube 3 for inflation.

[0049] During welding, nitrogen needs to be filled first to exhaust the air in the gas-filled area to avoid oxidation and other problems during welding. Specifically, during the process of filling nitrogen, nitrogen enters the gas-filled area through the air-permeable holes 41. Since the gas enters the gas-filled area through the gas-filling head 4, the gas flow rate will not be too fast at this time, and a gas vortex will not be formed in the gas-filled area, thereby avoiding affecting welding.

[0050] When welding the welding ends of two welded pipes, the assembly gap between the two welding ends is filled by welding layer by layer. In this embodiment, the weld between the two welding ends is composed of a four-layer structure, that is, the first welding is performed along the assembly gap to form a first layer of weld for base, and then welding is continued on the basis of the first layer of weld to form a second layer and a third layer of weld for filling, and finally welding is performed to form a fourth layer of weld. The specific positions of the four layers of weld are as follows: Figure 4 As shown, the numbers in the figure represent four layers of welds. It should be noted that during the welding process, the current used for each welding gradually increases. The first layer is welded with a smaller current to avoid problems such as welding through, while the subsequent welding uses a larger current to improve welding efficiency. It should be noted that during the welding process, the bottoms of the two welded pipes are in contact with a conductor, which is connected to the welding power supply. Since the welded pipe is not connected to the power supply, the problem of the outer surface of the welded pipe being burned by the current during welding can be avoided.

[0051] like Figure 5 As shown, in this embodiment, the four welds adopt the same welding sequence, that is, the welding sequence of each layer is: first weld upward from the six o'clock position to the three o'clock position; then weld upward from the six o'clock position to the nine o'clock position; then weld upward from the three o'clock position to the twelve o'clock position; and finally weld upward from the nine o'clock position to the twelve o'clock position.

[0052] In this embodiment, in order to avoid weld nodules during the welding process, the temperature of each welding is controlled below 100°C.

[0053] After welding, the weld is tested to verify the implementation of the method. The test items include appearance inspection, weld X-ray flaw detection, strength test, yield test, tensile test, bending test, low-temperature impact test of -196℃, macroscopic metallographic and intergranular corrosion test, etc. The requirements of each test item and the test results of the sample are shown in Table 1.

[0054] Table 1

[0055]

[0056]

[0057] By adopting the nitrogen protection welding method, the tensile strength of the sample is greater and the tensile performance is better; in the impact test, the heat input at the weld center, fusion line, and fusion line + 2mm is smaller using the nitrogen protection test method, and the impact toughness of the welded joint is higher. Among them, the test results of the samples protected by argon and nitrogen are shown in Table 2.

[0058] Table 2

[0059]

[0060] By testing the samples, the weld seam is well formed, the overall weld seam width is consistent, the X-ray flaw detection results are qualified, no defects such as lack of fusion, pores, slag inclusions, cracks, etc. are found in the weld seam, and the results of strength test, yield test, tensile test, bending test, etc. are all qualified. Therefore, by using nitrogen as the shielding gas for welding, the welding quality of stainless steel pipes is improved. In addition, the use of nitrogen as the shielding gas can achieve the purpose of cost saving and solve the problem of high cost.

[0061] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A pipeline welding method, characterized in that: The steps of the method include: Pre-treating the welding ends of the two welded pipes; The welding ends of the two welding pipes are arranged opposite to each other and an assembly gap is provided between the two welding ends; A plugging tool is provided, the plugging tool comprising two plugging sponges, an exhaust pipe and an exhaust valve, the two plugging sponges are respectively installed in two welding pipes and arranged near the welding ends to form an inflation area around the assembly gap, one end of the exhaust pipe is connected to one of the plugging sponges, and the other end of the exhaust pipe is arranged outside the inflation area and connected to the exhaust valve; Provide an inflation tool, pass the inflation tool through another sealing sponge to extend into the inflation area, fill the inflation area with nitrogen, and weld the welding ends of the two welding pipes when the air in the inflation area is exhausted. When the two welding ends are about to close, open the exhaust valve.

2. The pipeline welding method according to claim 1, characterized in that: The specific steps of pre-treating the welding ends of the two welded pipes include: Perform groove treatment on the welding ends of the two welded pipes respectively; Clean both welding ends.

3. The pipeline welding method according to claim 2, characterized in that: The type of groove is V-shaped groove, and the single-side angle of the groove is 30°±1°.

4. The pipeline welding method according to claim 2, characterized in that: The step of cleaning the two welding ends includes: polishing the pipe walls on both sides of the welding end and wiping the welding seam area with acetone.

5. The pipeline welding method according to claim 1, characterized in that: The step of arranging the welding ends of the two welded pipes opposite to each other and setting an assembly gap between the two welding ends includes: providing an inlay iron and a horse plate, inserting the inlay iron into the two welded pipes for positioning, removing the inlay iron after positioning, and using the horse plate to weld and fix the two welded pipes.

6. The pipeline welding method according to claim 1, characterized in that: The plugging tool also includes two steel plates, which are respectively connected to the two plugging sponges. When the two plugging sponges are respectively installed in the two welding pipes, the two steel plates are respectively placed on the opposite sides of the two plugging sponges.

7. The pipeline welding method according to claim 1, characterized in that: The inflatable tooling includes an inflatable tank, an inflatable tube and an inflatable head. The inflatable tube is used to connect the inflatable tank and the inflatable head. The inflatable head is arranged in the inflatable area and has a plurality of small ventilation holes.

8. The pipeline welding method according to claim 1, characterized in that: When welding the welding ends of two welded pipes, a layer-by-layer welding method is adopted to fill the assembly gap between the two welding ends.

9. The pipeline welding method according to claim 8, characterized in that: The welding order of each layer is: first weld upward from the six o'clock position to the three o'clock position; then weld upward from the six o'clock position to the nine o'clock position; then weld upward from the three o'clock position to the twelve o'clock position; finally weld upward from the nine o'clock position to the twelve o'clock position.

10. The pipeline welding method according to claim 1, characterized in that: The temperature during welding is controlled below 100°C.

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