Welding method for misaligned pipe orifice of pipeline

Abstract

The invention discloses a welding method of a pipeline misaligned pipe orifice, and relates to the technical field of pipeline welding, the welding method of the pipeline misaligned pipe orifice is used for welding a first pipe section and a second pipe section which are misaligned in a pipeline, and comprises the following steps: coaxially butting the first pipe section and the second pipe section, obtaining the outer alignment tolerance of the outer surface of the pipeline and the inner alignment tolerance of the inner surface of the pipeline; two opposite ports of the first pipe section and the second pipe section are welded together to form a butt welding seam; according to the outer alignment tolerance and the inner alignment tolerance, reinforcement welding is conducted on the inner side and the outer side of the butt welding seam, so that an inner reinforcement welding seam and an outer reinforcement welding seam which obliquely cover the inner surface and the outer surface of the butt welding seam are formed, and the size of the inner reinforcement welding seam in the axial direction is larger than that of the inner alignment tolerance; the size of the outer reinforcing weld joint in the axial direction is larger than the outer alignment tolerance. According to the scheme, reinforcing welding is carried out according to the outer misalignment quantity and the inner misalignment quantity, the welding strength of the pipe opening connecting position is guaranteed, and the welding difficulty of the misalignment pipe opening position is reduced.

Description

Technical Field

[0001] This invention relates to the field of pipe welding technology, and in particular to a welding method for misaligned pipe ends. Background Technology

[0002] In large-scale chemical plants, such as propane dehydrogenation and ethylene cracking processes, reaction feed and discharge pipelines often use large-diameter, thick-walled carbon steel or chromium-molybdenum alloy steel pipes. These pipelines require extremely high standards for the integrity, strength, and creep resistance of their welded joints.

[0003] However, due to manufacturing tolerances, non-standard pipe types, or on-site assembly errors, misalignment frequently occurs when pipe sections are joined. If this misalignment is not properly addressed, it can not only affect welding quality but also lead to stress concentration at the weld, increasing the risk of leakage and safety hazards during pipeline operation. Traditional solutions typically involve forcibly grinding the higher side of the pipe wall to minimize the misalignment, but this often results in excessive material removal, weakening structural strength, and is particularly difficult to implement for pipes with significant misalignment. Summary of the Invention

[0004] The main objective of this invention is to propose a welding method for misaligned pipe ends, which aims to solve the problems of difficult welding or substandard welding strength of misaligned pipe ends, and to achieve a highly reliable and high-pass-rate welded joint without weakening the strength of the pipe.

[0005] To achieve the above objectives, this invention proposes a welding method for misaligned pipe ends, used to weld a first pipe segment and a second pipe segment with misaligned ends, comprising the following steps: The first and second pipe sections are coaxially connected to obtain the external misalignment of the outer surface and the internal misalignment of the inner surface of the pipe. The two opposite ends of the first and second pipe sections are welded together to form a butt weld. Based on the external misalignment and the internal misalignment, reinforcement welding is performed on the inner and outer sides of the butt weld to form an inner reinforcement weld and an outer reinforcement weld that are inclined to cover the inner and outer surfaces of the butt weld. The axial dimension of the inner reinforcement weld is greater than the internal misalignment, and the axial dimension of the outer reinforcement weld is greater than the external misalignment.

[0006] In one embodiment, the inner misalignment is a1, the outer misalignment is a2, the axial dimension of the inner reinforcing weld is b1, and the axial dimension of the outer reinforcing weld is b2, satisfying: b1≥3a1, b2≥3a2.

[0007] In one embodiment, before the step of coaxially connecting the first pipe segment and the second pipe segment to obtain the external misalignment of the outer surface of the pipe and the internal misalignment of the inner surface, the method further includes: Obtain the diameter difference between the first and second pipe sections; If the pipe diameter difference is less than the preset difference, adjust the diameter of the pipe opening of the first or second pipe segment to eliminate the misalignment.

[0008] In one embodiment, the preset difference is c, the wall thickness of the first pipe section is d1, and the wall thickness of the second pipe section is d2, satisfying: c≤10%d1, c≤10%d2.

[0009] In one embodiment, prior to the step of welding the two opposite ends of the first pipe segment and the second pipe segment together to form a butt weld, the method further includes: The pipe openings of the first and second pipe sections are processed to form inwardly sloping bevels.

[0010] In one embodiment, after processing the openings of the first and second pipe sections to form an inwardly inclined bevel, the method further includes: Grind and clean the beveled surface to remove impurities such as oxide scale, oil, and moisture.

[0011] In one embodiment, the bevel is formed by an angle grinder, a milling machine or a carbon arc gouging machine, and the surface roughness Ra of the bevel is ≤12.5μm.

[0012] In one embodiment, after the step of performing reinforcing welds on the inner and outer sides of the butt weld according to the outer misalignment and the inner misalignment to form an inner reinforcing weld and an outer reinforcing weld that obliquely cover the inner and outer surfaces of the butt weld, the method further includes: The reinforcing weld is heat-treated at a temperature of 600 to 650°C for 2 to 4 hours.

[0013] In one embodiment, after the step of heat-treating the reinforcing weld at a temperature of 600 to 650°C and a holding time of 2 to 4 hours, the method further includes: Radiographic and ultrasonic testing were performed on the reinforcing welds.

[0014] In one embodiment, the reinforcing welding is performed using a tungsten inert gas (TIG) welding process.

[0015] The technical solution of this invention first involves coaxially butt-joining the first and second pipe segments to prepare for subsequent welding. Then, preliminary welding is performed on the first and second pipe segments, connecting the pipe ends together through a butt weld, ensuring the continuity of the walls of the first and second pipe segments. Finally, based on the previously obtained internal and external misalignment amounts, reinforcing welds are performed on both the inner and outer sides of the butt weld, forming reinforcing welds that cover the butt weld, thereby strengthening the connection between the first and second pipe segments. Specifically, the axial dimension of the inner reinforcing weld is larger than the internal misalignment amount, and the axial dimension of the outer reinforcing weld is larger than the outer misalignment amount. This achieves a smooth weld coverage on the walls of the first and second pipe segments, avoiding geometric discontinuities at the misaligned pipe ends and effectively improving the stress concentration problem at the weld. This simple method achieves high-strength welding of misaligned pipe ends. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 This is a partial structural diagram of the pipe opening at the misaligned edge. Figure 2 This is a schematic flowchart of the first embodiment of the welding method for misaligned pipe ends provided by the present invention; Figure 3 This is a schematic flowchart of the second embodiment of the welding method for misaligned pipe ends provided by the present invention; Figure 4 This is a flowchart illustrating the third embodiment of the welding method for misaligned pipe ends provided by the present invention. Figure 5 This is a flowchart illustrating the fourth embodiment of the welding method for misaligned pipe ends provided by the present invention.

[0018] Explanation of icon numbers: 1. First pipe section; 2. Second pipe section; 3. Butt weld; 4. Internal reinforcement weld; 5. External reinforcement weld.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

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

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] In large-scale chemical plants, such as propane dehydrogenation and ethylene cracking processes, reaction feed and discharge pipelines often use large-diameter, thick-walled carbon steel or chromium-molybdenum alloy steel pipes. These pipelines require extremely high standards for the integrity, strength, and creep resistance of their welded joints.

[0024] However, due to manufacturing tolerances, non-standard pipe types, or on-site assembly errors, misalignment frequently occurs when pipe sections are joined. If this misalignment is not properly addressed, it can not only affect welding quality but also lead to stress concentration at the weld, increasing the risk of leakage and safety hazards during pipeline operation. Traditional solutions typically involve forcibly grinding the higher side of the pipe wall to minimize the misalignment, but this often results in excessive material removal, weakening structural strength, and is particularly difficult to implement for pipes with significant misalignment.

[0025] The main objective of this invention is to propose a welding method for misaligned pipe ends, which aims to solve the problems of difficult welding or substandard welding strength of misaligned pipe ends, and to achieve a highly reliable and high-pass-rate welded joint without weakening the strength of the pipe.

[0026] To achieve the above objectives, please refer to Figures 1 to 2 This invention proposes a welding method for misaligned pipe ends, used to weld a first pipe segment 1 and a second pipe segment 2 with misaligned ends in a pipe, comprising the following steps: S100. Connect the first pipe section 1 and the second pipe section 2 coaxially to obtain the external misalignment of the outer surface of the pipe and the internal misalignment of the inner surface. S200. Weld the two opposite ends of the first pipe section 1 and the second pipe section 2 together to form a butt weld 3; S300. Based on the external misalignment amount and the internal misalignment amount, reinforcement welding is performed on the inner and outer sides of the butt weld 3 to form an inner reinforcement weld 4 and an outer reinforcement weld 5 that are inclined to cover the inner and outer surfaces of the butt weld 3. The axial dimension of the inner reinforcement weld 4 is greater than the internal misalignment amount, and the axial dimension of the outer reinforcement weld 5 is greater than the external misalignment amount.

[0027] The technical solution of this invention firstly involves coaxially butt-jointing the first pipe segment 1 and the second pipe segment 2 to prepare for subsequent welding. Then, preliminary welding is performed on the first pipe segment 1 and the second pipe segment 2, connecting the pipe ends together through a butt weld 3, ensuring the continuity of the walls of the first pipe segment 1 and the second pipe segment 2. Finally, based on the previously obtained internal and external misalignment amounts, reinforcing welds are performed on both the inner and outer sides of the butt weld 3, forming reinforcing welds that cover the butt weld 3, thereby strengthening the connection between the first pipe segment 1 and the second pipe segment 2. Specifically, the axial dimension of the inner reinforcing weld 4 is larger than the internal misalignment amount, and the axial dimension of the outer reinforcing weld 5 is larger than the external misalignment amount. This achieves a smooth weld coverage on the walls of the first pipe segment 1 and the second pipe segment 2, avoiding geometric discontinuities at the misaligned pipe ends and effectively improving the stress concentration problem at the weld. This simple method achieves high-strength welding of misaligned pipe ends.

[0028] It should be noted that, Figure 1 The diagram only shows the structure above the half-axis plane of the first pipe section 1 and the second pipe section 2. The 1 and 2 markings are specifically the pipe walls of the first pipe section 1 and the second pipe section 2, respectively.

[0029] In practice, the butt weld 3 was completed using a combination of manual tungsten inert gas (TIG) welding for the root pass and manual electric arc welding for the filler pass. The interpass temperature was strictly controlled to ≤150℃ and the ambient humidity to <80% during the welding process, and a windproof canopy was erected.

[0030] Furthermore, the internal misalignment is a1, the external misalignment is a2, the axial dimension of the internal reinforcing weld 4 is b1, and the axial dimension of the external reinforcing weld 5 is b2, satisfying: b1≥3a1, b2≥3a2. This configuration, by limiting the relationship between the internal misalignment and the axial dimension of the internal reinforcing weld 4, and the relationship between the external misalignment and the axial dimension of the external reinforcing weld 5, helps to disperse stress at the weld joint, reduce the probability of crack formation, and thus extend the service life of the pipeline.

[0031] In the second embodiment provided by the present invention, please refer to Figure 3 Before the step of coaxially connecting the first pipe segment 1 and the second pipe segment 2 to obtain the external misalignment of the outer surface and the internal misalignment of the inner surface of the pipe, the method further includes: S401, Obtain the diameter difference between the first pipe segment 1 and the second pipe segment 2; S402. If the pipe diameter difference is less than the preset difference, adjust the diameter of the pipe opening of the first pipe section 1 or the second pipe section 2 to eliminate the misalignment.

[0032] It should be noted that this solution does not limit the specific implementation method for eliminating misalignment. For example, a jack or hydraulic tensioner can be used to make circumferential uniform adjustment so that the diameters of the two pipe openings are similar. Alternatively, the pipe wall at the pipe opening can be processed and reduced to make the wall surfaces of the two pipe openings match.

[0033] Furthermore, the preset difference value is c, the wall thickness of the first pipe section 1 is d1, and the wall thickness of the second pipe section 2 is d2, satisfying: c≤10%d1, c≤10%d2. By limiting the relationship between the wall thickness of the first pipe section 1, the wall thickness of the second pipe section 2, and the preset difference value, the difficulty of eliminating misalignment is reduced, the connection quality of the pipe joints is guaranteed, and the construction efficiency is improved.

[0034] In the third embodiment provided by the present invention, please refer to Figure 4 Before the step of welding the two opposite ends of the first pipe segment 1 and the second pipe segment 2 together to form a butt weld 3, the method further includes: S501. The pipe openings of the first pipe section 1 and the second pipe section 2 are processed to form an inwardly inclined bevel.

[0035] Furthermore, after processing the pipe openings of the first pipe segment 1 and the second pipe segment 2 to form an inwardly inclined bevel, the method further includes: S502. Grind and clean the bevel to remove impurities such as oxide scale, oil, and moisture.

[0036] Understandably, by beveling and cleaning the pipe opening, the quality of the weld surface is ensured, the influence of impurities is reduced, and the welding success rate is improved.

[0037] Furthermore, the bevel is formed using an angle grinder, milling machine, or carbon arc gouging, with a surface roughness Ra ≤ 12.5 μm. In practice, an angle grinder with a stainless steel wire brush is used to clean the bevel and a 50 mm radius on both sides to remove oxide scale, oil, and moisture until a metallic luster is revealed.

[0038] In the fourth embodiment provided by the present invention, please refer to Figure 5 After the step of performing reinforcing welding on the inner and outer sides of the butt weld 3 according to the outer misalignment and the inner misalignment to form an inner reinforcing weld 4 and an outer reinforcing weld 5 that obliquely cover the inner and outer surfaces of the butt weld 3, the method further includes: S601. The reinforcing weld shall be heat-treated at a temperature of 600 to 650°C for 2 to 4 hours.

[0039] Furthermore, after the step of heat-treating the reinforcing weld at a temperature of 600 to 650°C and a holding time of 2 to 4 hours, the method further includes: S602. Perform radiographic and ultrasonic testing on the reinforcing welds.

[0040] In practice, X-ray inspection shall be carried out in accordance with NB / T47013.2-2015, with Class II qualification required; ultrasonic inspection shall be carried out in accordance with NB / T47013.3-2015, requiring the absence of incomplete fusion, cracks, and dense pores.

[0041] Understandably, post-weld heat treatment and non-destructive testing further ensure the mechanical properties of the weld and reduce potential safety hazards.

[0042] It is worth mentioning that the reinforcing welding was carried out using tungsten inert gas (TIG) welding. TIG welding offers advantages such as arc stability and high weld quality, making it suitable for the high-quality welding requirements under complex operating conditions in this project.

[0043] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A welding method for misaligned pipe ends, used to weld a first pipe segment and a second pipe segment with misaligned ends in a pipe, characterized in that, Includes the following steps: The first and second pipe sections are coaxially connected to obtain the external misalignment of the outer surface and the internal misalignment of the inner surface of the pipe. The two opposite ends of the first and second pipe sections are welded together to form a butt weld. Based on the external misalignment and the internal misalignment, reinforcement welding is performed on the inner and outer sides of the butt weld to form an inner reinforcement weld and an outer reinforcement weld that are inclined to cover the inner and outer surfaces of the butt weld. The axial dimension of the inner reinforcement weld is greater than the internal misalignment, and the axial dimension of the outer reinforcement weld is greater than the external misalignment.

2. The welding method for misaligned pipe ends as described in claim 1, characterized in that, The inner misalignment is a1, the outer misalignment is a2, the axial dimension of the inner reinforcing weld is b1, and the axial dimension of the outer reinforcing weld is b2, satisfying: b1≥3a1, b2≥3a2.

3. The welding method for misaligned pipe ends as described in claim 1, characterized in that, Before the step of coaxially connecting the first pipe segment and the second pipe segment to obtain the external misalignment of the outer surface and the internal misalignment of the inner surface of the pipe, the method further includes: Obtain the diameter difference between the first and second pipe sections; If the pipe diameter difference is less than the preset difference, adjust the diameter of the pipe opening of the first or second pipe segment to eliminate the misalignment.

4. The welding method for misaligned pipe ends as described in claim 3, characterized in that, The preset difference is c, the wall thickness of the first pipe section is d1, and the wall thickness of the second pipe section is d2, satisfying: c≤10%d1, c≤10%d2.

5. The welding method for misaligned pipe ends as described in claim 1, characterized in that, Prior to the step of welding the two opposite ends of the first pipe segment and the second pipe segment together to form a butt weld, the method further includes: The pipe openings of the first and second pipe sections are processed to form inwardly sloping bevels.

6. The welding method for misaligned pipe ends as described in claim 5, characterized in that, The step of processing the pipe openings of the first and second pipe sections to form an inwardly inclined bevel also includes: Grind and clean the beveled surface to remove impurities such as oxide scale, oil, and moisture.

7. The welding method for misaligned pipe ends as described in claim 6, characterized in that, The bevel is formed by using an angle grinder, milling machine or carbon arc gouging, and the surface roughness Ra of the bevel is ≤12.5μm.

8. The welding method for misaligned pipe ends as described in claim 1, characterized in that, After the step of performing reinforcing welding on the inner and outer sides of the butt weld according to the outer misalignment and the inner misalignment to form an inner reinforcing weld and an outer reinforcing weld that obliquely cover the inner and outer surfaces of the butt weld, the method further includes: The reinforcing weld is heat-treated at a temperature of 600 to 650°C for 2 to 4 hours.

9. The welding method for misaligned pipe ends as described in claim 8, characterized in that, The step of heat-treating the reinforcing weld at a temperature of 600 to 650°C and holding it for 2 to 4 hours further includes: Radiographic and ultrasonic testing were performed on the reinforcing welds.

10. The welding method for misaligned pipe ends as described in claim 1, characterized in that, The reinforcing welding was carried out using tungsten inert gas (TIG) welding.

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