Large-diameter long-distance pipeline welding method

Abstract

The invention relates to the field of oil and gas gathering and transportation, in particular to a large-diameter long-distance pipeline welding method. The problems that an existing large-diameter long-distance pipeline is not high in welding quality and low in welding efficiency are mainly solved. Comprising the following steps that S1, a groove structure is determined, and a pipe end groove of a pipeline is machined; s2, performing pipe orifice assembly by using a pipe internal aligning device with a copper gasket, and enabling the copper gasket to be tightly attached to the back surface of the welding seam in an expanding manner; and S3, the pipelines are assembled, welding process parameters are determined, and the pipelines are welded through a double-welding-torch external automatic welding method. According to the welding method for the large-diameter long-distance pipeline, the inner aligning device and the copper liner are adopted for assembly, the double-welding-torch welding machine is adopted for automatic welding, one-time forming of root welding and hot welding is achieved, the welding quality is greatly improved, and the welding speed is greatly increased.

Description

Technical Field

[0001] This invention relates to the field of oil and gas gathering and transportation, specifically a welding method for large-diameter long-distance pipelines. Background Technology

[0002] Currently, most large-diameter long-distance pipelines in China have diameters between D1000mm and D1500mm. They generally employ a fully automated welding process using an internal welding machine for root welding. In situations where an internal welding machine cannot be used, such as in mountainous areas, hilly terrain, waterways, trench crossings, joints, elbows, and welds with varying wall thicknesses, a combination of manual argon arc root welding and automated welding is often used. However, this process is slow and inefficient. Internationally, there is also an automated welding technology for copper lining copper gaskets in long-distance pipeline circumferential welds that uses a single-torch automated welding machine for root welding, followed by a hot-welded layer. This method results in lower welding quality and lower efficiency. Summary of the Invention

[0003] To overcome the shortcomings of existing large-diameter long-distance pipeline welding, such as low welding quality and low welding efficiency, this invention provides a welding method for large-diameter long-distance pipelines. This method uses an internal alignment tool with a copper gasket for alignment and automatic welding with a dual-torch welding machine to achieve root welding and hot welding in one step, which greatly improves welding quality and welding speed.

[0004] The technical solution of this invention is: a welding method for large-diameter long-distance pipelines, comprising the following steps:

[0005] S1. Determine the bevel structure and process the pipe end bevel;

[0006] S2. Use a pipe fitting tool with a copper gasket to assemble the pipe ends and ensure that the copper gasket is tightly attached to the back of the weld.

[0007] S3. Assemble the pipelines, determine the welding process parameters, and weld the pipelines using a dual-torch external automatic welding method.

[0008] Furthermore, the bevel is a U-shaped bevel, with a bevel face angle β1 of 4°±1°, a blunt edge P1 of 1.5-2mm, a gap b1 of 0-0.5mm, a half-bevel width W1 of 3.6-4.2mm, an arc radius R1 of 2.4-3.2mm, and a distance h from the inner wall of the pipe to the bottom of the arc of 4.2±0.3mm.

[0009] Furthermore, the bevel is a double-V composite bevel, with the upper bevel face angle β2 being 5°±1°, the lower bevel face angle α being 45°±1°, the blunt edge P2 being 1.3±0.3mm, the gap between the two sides b2 being 0-0.5mm, the height H from the inflection point to the inner wall being 3.7±0.3mm, and the half-bevel width W2 being 3.6-4.2mm.

[0010] Furthermore, when the weld bead is root pass and hot pass, the front torch current is 210-240A, the voltage is 18-24A, the wire feed speed is 9-13m / min, the gas flow rate is 30-40L / min, the welding speed is 60-80cm / min, and the heat input is 0.34-0.43KJ / mm; the rear torch current is 200-240A, the voltage is 19-25A, the wire feed speed is 9-12m / min, the gas flow rate is 25-40L / min, the welding speed is 60-80cm / min, and the heat input is 0.38-0.45KJ / mm.

[0011] Furthermore, when the weld bead is a filler weld for the first and second layers, the parameters of the front and rear welding torches are the same: current is 170-220A, voltage is 19-25A, wire feed speed is 9.5-11.5m / min, gas flow rate is 25-40L / min, welding speed is 50-65cm / min, and heat input is 0.39-0.48KJ / mm.

[0012] Furthermore, when the weld bead is a filler weld for the third and fourth layers, the front welding torch current is 170-210A, the voltage is 19-25A, the wire feed speed is 9.5-11.5m / min, the gas flow rate is 25-40L / min, the welding speed is 50-65cm / min, and the heat input is 0.38-0.48KJ / mm; the rear welding torch current is 160-200A, the voltage is 19-25A, the wire feed speed is 9-11m / min, the gas flow rate is 25-40L / min, the welding speed is 50-65cm / min, and the heat input is 0.36-0.46KJ / mm.

[0013] Furthermore, when the weld bead is the first and second layer of the cover weld, the parameters of the front and rear welding torches are the same: current is 110-140A, voltage is 19-25A, wire feed speed is 5.6-6.8m / min, gas flow rate is 25-40L / min, welding speed is 50-60cm / min, and heat input is 0.25-0.35KJ / mm.

[0014] Furthermore, during welding, carbon dioxide gas shielded welding is used, the welding polarity is reversed DC, and the welding direction is downward welding.

[0015] Furthermore, during welding, the weld bead is divided into root weld, hot weld, filler weld and cap weld, where the filler weld includes several filler weld layers and the cap weld includes several cap weld layers.

[0016] The present invention has the following beneficial effects: Due to the adoption of the above scheme, the welding method is used for large-diameter long-distance pipelines with diameters of D1000mm-D1500mm. Different welding parameters are set according to different weld passes, and automatic welding is carried out by a dual-torch welding machine. Through the external automatic welding root welding and hot welding one-time forming welding process, the efficiency and quality of root welding and hot welding are effectively improved, and the rework cost is reduced. The welding efficiency is at least 6 times higher than that of the current combination of manual argon arc welding root welding and automatic welding, which effectively reduces the labor intensity of workers and reduces the input of human resources. Attached Figure Description

[0017] Figure 1 This is a flowchart of the present invention;

[0018] Figure 2 This is a schematic diagram of a U-shaped bevel;

[0019] Figure 3 This is a schematic diagram of a double-V composite bevel. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the description of this invention, it is necessary to understand that the orientations or positional relationships indicated by terms such as "upper," "lower," "left," "right," "inner," "outer," "top," and "bottom" are based on the orientations or positional relationships shown in the accompanying drawings. They are intended only to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the components referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] Depend on Figure 1 As shown, a welding method for large-diameter long-distance pipelines, typically referring to long-distance pipelines with a diameter range of D1000mm-D1500mm, specifically includes the following steps:

[0023] S1. Determine the beveling structure and process the pipe end beveling. The beveling structure can be a U-shaped beveling or a double V-shaped beveling, wherein the U-shaped beveling is described below. Figure 2 The bevel angle β1 is 4°±1°, the blunt edge P1 is 1.5-2mm, the butt joint gap b1 is 0-0.5mm, the half-bevel width W1 is 3.6-4.2mm, the arc radius R1 is 2.4-3.2mm, and the distance h from the inner wall of the pipe to the bottom of the arc is 4.2±0.3mm. See the double-V composite bevel example. Figure 3The upper bevel angle β2 is 5°±1°, the lower bevel angle α is 45°±1°, the blunt edge P2 is 1.3±0.3mm, the gap b2 is 0-0.5mm, the height H from the inflection point to the inner wall is 3.7±0.3mm, and the half-bevel width W2 is 3.6-4.2mm. Both the U-shaped bevel and the double V-shaped bevel use copper backing pads.

[0024] S2. Use a pipe fitting with a copper gasket to assemble the pipe ends and make the copper gasket tightly adhere to the back of the weld, sealing the bevel gap at the joint of the weldment, thereby constraining the shape of the weld pool and forming a good weld quality. This can avoid defects such as incomplete penetration, burn-through, and poor root fusion in the weld.

[0025] S3. Assemble the pipeline, determine the welding process parameters, and use a dual-torch external automatic welding method to weld the pipeline. With the pipeline in a horizontal and fixed state, the welding process parameters for circumferential welds of different thicknesses at different positions along the 360° circumference are the key technologies. These include determining the welding torch travel speed, wire feed speed, extension length, welding torch swing width, welding torch swing frequency, dwell time on both sides, voltage, etc. At the same time, in conjunction with inspection methods such as visual inspection, non-destructive testing, and mechanical property testing, an automatic external root welding process for copper backing is formed.

[0026] In welding long-distance pipelines, carbon dioxide gas shielded welding is used, with DC reverse polarity and downward welding direction. The weld bead is divided into root pass, hot pass, fill pass, and cap pass. The fill pass consists of several fill pass layers, and the cap pass consists of several cap pass layers. Different welding parameters are used for different weld bead types.

[0027] When the weld bead is root pass and hot pass, the current of the front welding torch is 210-240A, the voltage is 18-24A, the wire feed speed is 9-13m / min, the gas flow rate is 30-40L / min, the welding speed is 60-80cm / min, and the heat input is 0.34-0.43KJ / mm; the current of the rear welding torch is 200-240A, the voltage is 19-25A, the wire feed speed is 9-12m / min, the gas flow rate is 25-40L / min, the welding speed is 60-80cm / min, and the heat input is 0.38-0.45KJ / mm.

[0028] When the weld bead is the first and second filler layer, the parameters of the front and rear welding torches are the same: current is 170-220A, voltage is 19-25A, wire feed speed is 9.5-11.5m / min, gas flow rate is 25-40L / min, welding speed is 50-65cm / min, and heat input is 0.39-0.48KJ / mm.

[0029] When the weld bead is the third and fourth filler layer, the front torch current is 170-210A, the voltage is 19-25A, the wire feed speed is 9.5-11.5m / min, the gas flow rate is 25-40L / min, the welding speed is 50-65cm / min, and the heat input is 0.38-0.48KJ / mm; the rear torch current is 160-200A, the voltage is 19-25A, the wire feed speed is 9-11m / min, the gas flow rate is 25-40L / min, the welding speed is 50-65cm / min, and the heat input is 0.36-0.46KJ / mm.

[0030] When the weld bead is the first and second layer of the cover weld, the parameters of the front and rear welding torches are the same: current is 110-140A, voltage is 19-25A, wire feed speed is 5.6-6.8m / min, gas flow rate is 25-40L / min, welding speed is 50-60cm / min, and heat input is 0.25-0.35KJ / mm.

[0031] See Table 1 for details:

[0032] Table 1: Welding process parameters

[0033]

[0034] This welding method is designed for large-diameter long-distance pipelines with diameters ranging from D1000mm to D1500mm. Different welding parameters are set for different weld passes, and an automated dual-torch welding machine is used for welding. Through an automated external root welding and hot welding process, the efficiency and quality of root welding and hot welding are effectively improved, significantly reducing rework costs. The welding efficiency is at least six times higher than the current combination of manual argon arc welding and automated root welding, effectively reducing the labor intensity of workers and minimizing human resource input.

[0035] Example 1:

[0036] X80 steel Φ1219×19.1mm pipe copper gasket double welding torch external automatic welding.

[0037] Using a hydraulic copper gasket alignment tool as the assembly tool, and an X80 steel pipe with a diameter of 1219mm (wall thickness of 19.1mm) at position 5G as the test object, double V-grooves and U-grooves were independently designed. Welding was performed using a dual-torch automatic welding machine, with root welding and hot welding completed in one step. After passing the welding process test, the process qualification was completed. This welding process is superior to the single-torch automatic welding process for copper gasket pipes used domestically and internationally. The root welding and hot welding are completed in one step, further shortening the welding time, simplifying one process step, and reducing the time interval between root welding and hot welding. Laboratory tests showed that the weld joints welded according to the determined process parameters meet the requirements of current standards and specifications, and the mechanical performance test of the weld bead passed.

[0038] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A welding method for large-diameter long-distance pipelines, characterized in that... Includes the following steps: S1. Determine the bevel structure and process the pipe end bevel; S2. Use a pipe fitting tool with a copper gasket to assemble the pipe ends and ensure that the copper gasket is tightly attached to the back of the weld. S3. Assemble the pipelines, determine the welding process parameters, and weld the pipelines using a dual-torch external automatic welding method.

2. The welding method for large-diameter long-distance pipelines according to claim 1, characterized in that: The bevel is a U-shaped bevel with a bevel face angle β1 of 4°±1°, a blunt edge P1 of 1.5-2mm, a gap b1 of 0-0.5mm, a half-bevel width W1 of 3.6-4.2mm, an arc radius R1 of 2.4-3.2mm, and a distance h from the inner wall of the pipe to the bottom of the arc of 4.2±0.3mm.

3. The welding method for large-diameter long-distance pipelines according to claim 1, characterized in that: The bevel is a double-V composite bevel. The upper bevel face angle β2 is 5°±1°, the lower bevel face angle α is 45°±1°, the blunt edge P2 is 1.3±0.3mm, the gap between the two bevels b2 is 0-0.5mm, the height H from the inflection point to the inner wall is 3.7±0.3mm, and the half-bevel width W2 is 3.6-4.2mm.

4. The welding method for large-diameter long-distance pipelines according to claim 1, characterized in that: When the weld bead is root pass and hot pass, the current of the front welding torch is 210-240A, the voltage is 18-24A, the wire feed speed is 9-13m / min, the gas flow rate is 30-40L / min, the welding speed is 60-80cm / min, and the heat input is 0.34-0.43KJ / mm; the current of the rear welding torch is 200-240A, the voltage is 19-25A, the wire feed speed is 9-12m / min, the gas flow rate is 25-40L / min, the welding speed is 60-80cm / min, and the heat input is 0.38-0.45KJ / mm.

5. The welding method for large-diameter long-distance pipelines according to claim 1, characterized in that: When the weld bead is the first and second filler layer, the parameters of the front and rear welding torches are the same: current is 170-220A, voltage is 19-25A, wire feed speed is 9.5-11.5m / min, gas flow rate is 25-40L / min, welding speed is 50-65cm / min, and heat input is 0.39-0.48KJ / mm.

6. The welding method for large-diameter long-distance pipelines according to claim 1, characterized in that: When the weld bead is the third and fourth filler layer, the front torch current is 170-210A, the voltage is 19-25A, the wire feed speed is 9.5-11.5m / min, the gas flow rate is 25-40L / min, the welding speed is 50-65cm / min, and the heat input is 0.38-0.48KJ / mm; the rear torch current is 160-200A, the voltage is 19-25A, the wire feed speed is 9-11m / min, the gas flow rate is 25-40L / min, the welding speed is 50-65cm / min, and the heat input is 0.36-0.46KJ / mm.

7. The welding method for large-diameter long-distance pipelines according to claim 1, characterized in that: When the weld bead is the first and second layer of the cover weld, the parameters of the front and rear welding torches are the same: current is 110-140A, voltage is 19-25A, wire feed speed is 5.6-6.8m / min, gas flow rate is 25-40L / min, welding speed is 50-60cm / min, and heat input is 0.25-0.35KJ / mm.

8. The welding method for large-diameter long-distance pipelines according to claim 1, characterized in that: During welding, carbon dioxide gas shielded welding is used, the welding polarity is reversed DC, and the welding direction is downward welding.

9. The welding method for large-diameter long-distance pipelines according to claim 1, characterized in that: During welding, the weld bead is divided into root pass, hot pass, fill pass, and cap pass. The fill pass includes several fill pass layers, and the cap pass includes several cap pass layers.

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