Evaluation test method for in-service oil and gas pipeline welding lap fillet weld defect repair process

Abstract

The invention discloses an in-service oil and gas pipeline welding lap fillet weld defect evaluation test method. The method comprises the following steps that the type and position of an in-service oil and gas pipeline welding lap fillet weld defect are determined; designing a repair groove based on the fillet weld defect type and position; carrying out repair area division and welding process quality control on the repair groove; and formulating a fillet weld defect repair process flow. By setting the radius of the root of the groove, good fusion and forming of the root are guaranteed; the repair workload and the repair quality are compatible through groove angle adjustment; quality control of a fillet weld repair local area is refined, the repair fusion quality is improved by setting different welding heat inputs, hydrogen-induced cracks are avoided, and the influence of secondary heat input is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of in-service welding of oil and gas pipelines, and particularly relates to a test method for evaluating the repair process of lap fillet weld defects in in-service welding of oil and gas pipelines. Background Art

[0002] In-service welding repair is one of the main repair methods for pipeline defects and leakage emergency repair, and is also an important development direction for pipeline repair, which directly affects the continuity and safety of pipeline operation. In-service pipeline welding repair not only has a short repair time, but also has low investment cost and is environmentally friendly, with broad development prospects. Common in-service pipeline welding repair methods include B-type sleeve repair and patch repair. Among them, most domestic B-type sleeves are made of Q345R ordinary container steel with a low steel grade. When this type of sleeve is applied to large-diameter high-steel-grade pipelines, due to the large difference in steel grades, the wall thickness of the sleeve is more than 40 mm. At present, high-steel-grade thin-wall sleeve products are gradually being promoted. The two main problems in the process of in-service welding repair of oil and gas pipelines are burn-through and hydrogen-induced cracking. To prevent burn-through, the pipeline operating conditions and welding process can be evaluated in advance before welding to find reasonable welding parameters. At the same time, the hydrogen content and the hardness of the heat-affected zone should be strictly controlled to prevent hydrogen-induced cracking. In-service welding repair of oil and gas pipelines has a certain degree of complexity and contingency, especially for field construction, it faces various uncontrollable factors.

[0003] The existing repair technologies are mainly applied to the repair of defects in butt welds, and generally, there is no requirement for the pipeline to have a conveying medium inside or for the repair to be carried out under a shutdown state. The repair working conditions are not complex.

[0004] The current research focus on in-service welding repair technology for oil and gas pipelines lies in the quality control of the welding process. It mainly improves the existing problems in the process through various means. While formulating reasonable and scientific welding process conditions, a perfect welding management system is also established to prevent the influence of uncontrollable factors at the construction site on the welding quality and ensure the reasonable, effective, safe and smooth implementation of in-service welding. However, the importance of defect repair for in-service welding repair has not been fully recognized. Once unacceptable buried defects occur, there is currently no clear and targeted repair method. Moreover, the workload of repair grinding and welding is relatively large, which is likely to introduce secondary defects and cause quality and safety problems. In addition, the possible defect positions in the lap fillet weld during in-service welding are not fixed. There are fillet weld fusion defects on the steel pipe side, fillet weld fusion defects on the sleeve side, and internal defects in the fillet weld cladding metal. For the welding defects existing in different positions, how to formulate the welding process, especially the selection of welding heat input, becomes particularly important. When formulating the welding process after grinding the fusion defect on the steel pipe side, both the generation of hydrogen-induced cracks and the prevention of the decrease in the pressure-bearing capacity of the in-service pipeline during welding should be considered. When formulating the welding process after grinding the fillet weld fusion defect, both the influence of secondary heating on the original welding cladding metal and the guarantee of good welding fusion should be considered. Summary of the Invention

[0005] In view of the above problems, the present invention discloses a test method for evaluating the repair process of lap fillet weld defects in in-service oil and gas pipelines, which includes the following steps:

[0006] Determine the type and position of lap fillet weld defects in in-service oil and gas pipelines;

[0007] Design a repair groove based on the type and position of the fillet weld defect;

[0008] Divide the repair area of the repair groove and control the welding process quality;

[0009] Formulate a repair process flow for fillet weld defects.

[0010] Furthermore, the type and position of the fillet weld defect include internal defects in the fillet weld cladding metal, fillet weld fusion defects on the steel pipe side, and fillet weld fusion defects on the sleeve side.

[0011] Furthermore, the specific steps for designing a repair groove based on the type and position of the fillet weld defect are as follows:

[0012] Design the groove angle and the root radius of the repair groove based on the type and position of the fillet weld defect.

[0013] Furthermore, the range of the groove angle is 40 - 90°.

[0014] Furthermore, the range of the root radius of the groove is 6 - 10 mm.

[0015] Furthermore, the division of the repair groove into repair areas and the control of welding process quality include the following steps:

[0016] Divide the repair groove into Area I, Area II, Area III, Area IV, and Area V;

[0017] Determine the welding processes for Area I, Area II, Area III, Area IV, and Area V;

[0018] Among them, Area I, Area II, Area III, Area IV, and Area V are arranged in sequence from the inside out.

[0019] Furthermore, Area I is divided into the first weld bead and the second weld bead; the root pass is used for the first weld bead, and the hot pass is used for the second weld bead;

[0020] Area II is divided into the third weld bead and the fourth weld bead; both the third weld bead and the fourth weld bead use single-layer single-pass filling welding;

[0021] Area III is divided into the fifth weld bead, the seventh weld bead, and the ninth weld bead; both the fifth weld bead, the seventh weld bead, and the ninth weld bead use single-layer multi-pass filling welding;

[0022] Area IV is divided into the sixth weld bead and the eighth weld bead; both the sixth weld bead and the eighth weld bead use single-layer multi-pass filling welding; among them, the fifth weld bead, the sixth weld bead, the seventh weld bead, the eighth weld bead, and the ninth weld bead are stacked in sequence;

[0023] Area V is the tenth weld bead; the tenth weld bead is a tempering weld bead.

[0024] Furthermore, the thickness of the first weld bead is less than 3 mm;

[0025] The thickness of the second weld bead is less than 3 mm;

[0026] The thickness of the third weld bead is less than 3 mm;

[0027] The thickness of the fourth weld bead is less than 3 mm;

[0028] The thickness of the fifth weld bead is less than 3.5 mm;

[0029] The thickness of the sixth weld bead is less than 3.5 mm;

[0030] The thickness of the seventh weld bead is less than 3.5 mm;

[0031] The thickness of the eighth weld bead is less than 3.5 mm;

[0032] The thickness of the ninth weld bead is less than 3.5 mm;

[0033] The thickness of the tenth weld bead is less than 3 mm.

[0034] Furthermore, the specific steps for formulating the repair process flow of fillet weld defects are as follows:

[0035] Through the preliminary design of the repair groove and the preliminary implementation of the welding process, mechanical property tests are carried out according to the welding procedure qualification method. Then, according to the welding quality problems in each area, the repair groove angle, the root radius of the groove, and the welding heat input in each area are adjusted. Furthermore, the welding voltage, welding current, and welding speed are adjusted to formulate the repair process flow of fillet weld defects.

[0036] Furthermore, the range of the welding voltage is 22 - 28V;

[0037] The range of the welding current is 100 - 130A;

[0038] The welding speed of the first pass, second pass, sixth pass, and eighth pass is 6 - 15 cm / min, and the welding heat input is 0.8 - 2.8 KJ / mm;

[0039] The welding speed of the third pass, fourth pass, fifth pass, seventh pass, and ninth pass is 10 - 16 cm / min, and the welding heat input is 0.9 - 1.3 KJ / mm;

[0040] The welding speed of the tenth pass is 10 - 15 cm / min, and the welding heat input is 0.8 - 2.8 KJ / mm.

[0041] Compared with the prior art, the embodiments of the present invention have at least the following advantages:

[0042] 1. By setting the root radius of the groove, good root fusion and forming are ensured; through the adjustment of the groove angle, the repair workload and repair quality are compatible;

[0043] 2. The quality control of the local area of fillet weld repair is refined. By setting different welding heat inputs, the repair fusion quality is improved, the generation of hydrogen-induced cracks is avoided, and the influence of secondary heat input is reduced.

[0044] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures pointed out in the specification and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0046] Figure 1 Shows a schematic diagram of the position of the lap fillet weld defect according to an embodiment of the present invention;

[0047] Figure 2 Shows a schematic diagram of the repair groove design according to an embodiment of the present invention;

[0048] Figure 3 Shows a schematic diagram of the welding quality control area according to an embodiment of the present invention;

[0049] Figure 4 Shows a schematic diagram of the repair welding sequence according to an embodiment of the present invention.

[0050] Reference numerals: 1, steel pipe to be repaired; 2, B-type sleeve; 3, circumferential lap fillet weld; 4, internal defect of the fillet weld cladding metal; 5, fusion defect of the fillet weld on the steel pipe side; 6, fusion defect of the fillet weld on the sleeve side; 7, repair area. Detailed implementation manners

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0052] A method for evaluating the repair process of lap fillet weld defects in in-service oil and gas pipelines proposed by the present invention includes the following steps:

[0053] Determine the type and position of the lap fillet weld defects in the in-service oil and gas pipelines;

[0054] Design a repair groove based on the type and position of the fillet weld defects;

[0055] Divide the repair area of the repair groove and control the welding process quality;

[0056] Formulate a repair process flow for fillet weld defects.

[0057] A process evaluation test method for repairing lap fillet weld defects in in-service oil and gas pipelines according to the present invention can meet the requirements for repairing fillet weld defects in oil and gas pipeline welding, improve the welding fusion quality, reduce the influence of secondary welding heating, and avoid the generation of hydrogen-induced cracks.

[0058] Figure 1 It is a schematic diagram of the position of the fillet weld defect. As Figure 1 shown, a B-type sleeve 2 is sleeved outside the steel pipe 1 to be repaired, and an annular lap fillet weld 3 is surfacing welded between the side of the B-type sleeve 2 and the steel pipe 1 to be repaired.

[0059] The steel pipe 1 to be repaired, the general reason for repair is that there are defects or leaks in the pipe body or girth weld of the steel pipe; the B-type sleeve 2 is used for repair and reinforcement, and generally has a wall thickness greater than that of the steel pipe 1 to be repaired; the annular lap fillet weld 3 is formed by surfacing welding with electrodes.

[0060] The types and positions of fillet weld defects include internal defects 4 in the fillet weld clad metal, fusion defects 5 in the fillet weld on the steel pipe side, and fusion defects 6 in the fillet weld on the sleeve side.

[0061] The internal defects 4 in the fillet weld clad metal are caused by improper process control during welding. During the repair process, the influence of secondary heating on the original welded clad metal should be considered, and good welding fusion should be ensured; for the fusion defects 5 in the fillet weld on the steel pipe side, the influence of secondary heating on the sleeve pipe body should be considered during the repair process, and good welding fusion should be ensured; for the fusion defects 6 in the fillet weld on the sleeve side, the generation of hydrogen-induced cracks should be considered during the repair process, and the decrease in the pressure-bearing capacity of the in-service pipeline during welding should be prevented; the arrow in the figure indicates the flow direction of the conveying medium.

[0062] In some embodiments, the specific steps for designing a repair groove based on the type and position of the fillet weld defect are as follows:

[0063] Design the groove angle and the root radius of the repair groove based on the type and position of the fillet weld defect.

[0064] Based on the type of fillet weld defect, the position of the repair groove is specifically divided into the repair groove inside the annular lap fillet weld 3, the repair groove abutting against the steel pipe, and the repair groove abutting against the sleeve.

[0065] In some embodiments, the range of the groove angle α is 40-90°.

[0066] In some embodiments, the range of the root radius R of the groove is 6-10 mm.

[0067] By setting the root radius of the groove, good fusion and forming at the root are ensured; by adjusting the groove angle, the repair workload and repair quality are compatible.

[0068] Figure 3Shows a schematic diagram of the welding quality control area according to an embodiment of the present invention. As Figure 3 shown, in some embodiments, the division of the repair area of the repair groove and the welding process quality control include the following steps:

[0069] Divide the repair area 7 corresponding to the repair groove into area Ⅰ, area Ⅱ, area Ⅲ, area Ⅳ, and area Ⅴ;

[0070] Determine the welding processes for area Ⅰ, area Ⅱ, area Ⅲ, area Ⅳ, and area Ⅴ;

[0071] Among them, area Ⅰ, area Ⅱ, area Ⅲ, area Ⅳ, and area Ⅴ are arranged in sequence from the inside out, area Ⅰ is located at the root of the repair groove, and area Ⅴ is located on the outermost side.

[0072] Figure 4 Shows a schematic diagram of the repair welding sequence according to an embodiment of the present invention. As Figure 4 shown, in some embodiments, area Ⅰ is divided into the first weld bead ① and the second weld bead ②; the first weld bead ① uses root welding, and the second weld bead ② uses hot welding;

[0073] Area Ⅱ is divided into the third weld bead ③ and the fourth weld bead ④; both the third weld bead ③ and the fourth weld bead ④ use single-layer single-pass filling welding;

[0074] Area Ⅲ is divided into the fifth weld bead ⑤, the seventh weld bead ⑦, and the ninth weld bead ⑨; both the fifth weld bead ⑤, the seventh weld bead ⑦, and the ninth weld bead ⑨ use single-layer multi-pass filling welding;

[0075] Area Ⅳ is divided into the sixth weld bead ⑥ and the eighth weld bead ⑧; both the sixth weld bead ⑥ and the eighth weld bead ⑧ use single-layer multi-pass filling welding; among them, the fifth weld bead ⑤, the sixth weld bead ⑥, the seventh weld bead ⑦, the eighth weld bead ⑧, and the ninth weld bead ⑨ are stacked in sequence;

[0076] Area Ⅴ is the tenth weld bead ⑩; the tenth weld bead ⑩ is a tempering weld bead.

[0077] In some embodiments, the thickness of the first weld bead is less than 3 mm;

[0078] The thickness of the second weld bead is less than 3 mm;

[0079] The thickness of the third weld bead is less than 3 mm;

[0080] The thickness of the fourth weld bead is less than 3 mm;

[0081] The thickness of the fifth weld bead is less than 3.5 mm;

[0082] The thickness of the sixth weld bead is less than 3.5 mm;

[0083] The thickness of the seventh weld bead is less than 3.5 mm;

[0084] The thickness of the eighth weld bead is less than 3.5 mm;

[0085] The thickness of the ninth weld bead is less than 3.5 mm;

[0086] The thickness of the tenth weld bead is less than 3 mm.

[0087] In some embodiments, the specific steps for formulating the repair process flow of fillet weld defects are as follows:

[0088] Through the preliminary design of the repair groove and the preliminary implementation of the welding process, mechanical property tests are carried out according to the welding process qualification method. Then, according to the welding quality problems in each area, the repair groove angle, the root radius of the groove, and the welding heat input in each area are adjusted. Furthermore, the welding voltage, welding current, and welding speed are adjusted to formulate the repair process flow of fillet weld defects.

[0089] In some embodiments, the range of the welding voltage is 22 - 28 V;

[0090] The range of the welding current is 100 - 130 A;

[0091] The welding speed of the first, second, sixth, and eighth weld beads is 6 - 15 cm / min, and the welding heat input is 0.8 - 2.8 KJ / mm;

[0092] The welding speed of the third, fourth, fifth, seventh, and ninth weld beads is 10 - 16 cm / min, and the welding heat input is 0.9 - 1.3 KJ / mm;

[0093] The welding speed of the tenth weld bead is 10 - 15 cm / min, and the welding heat input is 0.8 - 2.8 KJ / mm.

[0094] Refine the quality control of the local area of fillet weld repair. By setting different welding heat inputs, improve the repair fusion quality, avoid the generation of hydrogen-induced cracks, and reduce the influence of secondary heat input.

[0095] Exemplarily, taking the fillet weld fusion defect 6 on the sleeve side, which is the most difficult to control in quality, as an example, a power angle grinder is used to clean the defect and grind the repair groove. Figure 2 It is a schematic diagram of the design of the repair groove. The groove angle α is 60°; the root radius R of the groove is 6 mm.

[0096] Perform physical welding in the above grinding area. The repair welding sequence and the welding quality control area are as Figure 3As shown, the quality control of the local area of ​​the fillet weld repair is refined, and different welding heat inputs are set to improve the repair fusion quality, avoid hydrogen-induced cracking, and reduce the impact of secondary heat input. Among them, the fifth weld, the seventh weld and the ninth weld are all in contact with the steel pipe 1 to be repaired. The sixth weld and the eighth weld are both in contact with the annular lap fillet weld 3.

[0097] The thickness of the first weld ① is 2.5mm; the range of the second weld ② is 2.5mm; the thickness of the third weld ③ is 2.5mm; the thickness of the fourth weld ④ is 2.5mm; the thickness of the fifth weld ⑤ is 3mm; the thickness of the sixth weld ⑥ is 3mm; the thickness of the seventh weld ⑦ is 3mm; the thickness of the eighth weld ⑧ is 3mm; the thickness of the ninth weld ⑨ is 3mm; the thickness of the tenth weld ⑩ is 2.5mm.

[0098] The welding voltage range is 25V;

[0099] The welding current range is 120A;

[0100] The welding speed of the first, second, sixth and eighth passes is 8cm / min, and the welding heat input is 1.8KJ / mm;

[0101] The welding speed of the third, fourth, fifth, seventh and ninth passes is 14cm / min, and the welding heat input is 1.1KJ / mm;

[0102] The welding speed of the tenth weld is 12cm / min, and the welding heat input is 1.8KJ / mm.

[0103] The designed process assessment test repair groove is located on the steel pipe side and cladding metal, which can represent the impact of secondary welding heat input on the performance of weld cladding metal and steel pipe body. It is also the area where problems are most likely to occur in the repair of in-service pipelines, that is, the high-speed flowing medium takes away heat and causes hydrogen-induced cracks in the weld on the steel pipe side.

[0104] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. The test method for defect repair of lap fillet welds of in-service oil and gas pipelines is characterized by: The following steps are involved: Determine the defect types and locations of lap fillet welds in in-service oil and gas pipelines; Design repair groove based on fillet weld defect type and location; Divide the repair area of ​​the repair groove and control the welding process quality; Develop a process flow for repairing fillet weld defects.

2. The test method for defect repair process evaluation of lap fillet welds of in-service oil and gas pipelines according to claim 1 is characterized in that: The fillet weld defect types and locations include internal defects of fillet weld cladding metal, fusion defects of steel pipe side fillet welds and fusion defects of sleeve side fillet welds.

3. The test method for defect repair of lap fillet welds of in-service oil and gas pipelines according to claim 1 is characterized in that: The specific steps of designing the repair groove based on the type and location of the fillet weld defect are as follows: The groove angle and groove root radius of the repair groove are designed based on the defect type and location of the fillet weld.

4. The test method for defect repair process evaluation of lap fillet welds of in-service oil and gas pipelines according to claim 3 is characterized in that: The groove angle ranges from 40 to 90 degrees.

5. The test method for defect repair process evaluation of lap fillet welds of in-service oil and gas pipelines according to claim 3 is characterized in that: The radius of the groove root is in the range of 6 to 10 mm.

6. The test method for defect repair process evaluation of lap fillet welds of in-service oil and gas pipelines according to claim 1 is characterized in that: The division of the repair area for the repair groove and the welding process quality control include the following steps: Divide the repaired groove into area I, area II, area III, area IV and area V; Determine the welding process for areas I, II, III, IV and V; Among them, area I, area II, area III, area IV and area V are arranged in sequence from the inside to the outside.

7. The test method for defect repair process evaluation of lap fillet welds of in-service oil and gas pipelines according to claim 6 is characterized in that: The I region is divided into a first weld bead and a second weld bead; the first weld bead is root welded, and the second weld bead is hot welded; The II region is divided into a third weld bead and a fourth weld bead; the third weld bead and the fourth weld bead are both single-layer single-pass filling welds; The III region is divided into the fifth weld bead, the seventh weld bead and the ninth weld bead; the fifth weld bead, the seventh weld bead and the ninth weld bead are all single-layer multi-pass filling welds; The IV region is divided into a sixth weld bead and an eighth weld bead; the sixth weld bead and the eighth weld bead are both single-layer multi-pass filling welds; wherein the fifth weld bead, the sixth weld bead, the seventh weld bead, the eighth weld bead and the ninth weld bead are stacked in sequence; The V region is the tenth weld bead; the tenth weld bead is a tempering weld bead.

8. The test method for defect repair process evaluation of lap fillet welds of in-service oil and gas pipelines according to claim 7 is characterized in that: The thickness of the first weld bead is less than 3 mm; The thickness of the second weld bead is less than 3 mm; The thickness of the third weld bead is less than 3 mm; The thickness of the fourth weld bead is less than 3 mm; The thickness of the fifth weld bead is less than 3.5 mm; The thickness of the sixth weld bead is less than 3.5 mm; The thickness of the seventh weld bead is less than 3.5 mm; The thickness of the eighth weld bead is less than 3.5 mm; The thickness of the ninth weld bead is less than 3.5 mm; The thickness of the tenth weld bead is less than 3 mm.

9. The test method for defect repair process evaluation of lap fillet welds of in-service oil and gas pipelines according to claim 7 is characterized in that: The specific steps of formulating the fillet weld defect repair process are as follows: Through the preliminary design of the repair groove and the preliminary implementation of the welding process, mechanical properties tests are carried out according to the welding process assessment method. Then, according to the welding quality problems in each area, the repair groove angle, groove root radius and welding heat input of each area are adjusted, and then the welding voltage, welding current and welding speed are adjusted to formulate a process flow for repairing corner weld defects.

10. The test method for defect repair process evaluation of lap fillet welds of in-service oil and gas pipelines according to claim 9 is characterized in that: The welding voltage ranges from 22 to 28 V; The welding current ranges from 100 to 130A; The welding speed of the first weld bead, the second weld bead, the sixth weld bead and the eighth weld bead is 6-15 cm / min, and the welding heat input is 0.8-2.8 KJ / mm; The welding speed of the third weld bead, the fourth weld bead, the fifth weld bead, the seventh weld bead and the ninth weld bead is 10-16 cm / min, and the welding heat input is 0.9-1.3 KJ / mm; The welding speed of the tenth weld is 10-15 cm / min, and the welding heat input is 0.8-2.8 KJ / mm.

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