A method for determining the degree of hazard of pipeline girth weld defects

Abstract

The present invention discloses a method for determining the degree of hazard of pipeline girth weld defects. The method performs radiographic and TOFD inspections on pipeline girth weld defects. The defects found by radiographic and TOFD inspections are then determined and classified into surface-open defects and buried defects. Surface-open defects are determined as hazardous defects. Buried defects are determined as acceptable or unacceptable through TOFD inspection and ultrasonic verification of the defective areas exceeding the standard. Unacceptable defects are classified as point defects or linear defects, and then the acceptable and hazardous defects are determined. This method can reduce the number of unacceptable girth welds and the number of girth welds requiring repair decisions. It meets the needs of comprehensive pipeline inspection, assessment, and repair, and facilitates on-site promotion and use for girth weld hazard investigation and quality improvement.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipeline detection, and specifically relates to a method for determining the degree of hazard of defects such as cracks, lack of fusion, slag inclusions, and pores in a gas pipeline girth weld when the results of X-ray and TOFD detection are inconsistent. Background Art

[0002] Currently, there are over 10 million girth welds on long-distance oil and gas pipelines in China. For most pipelines constructed before 2015, the vast majority of girth welds were welded semi-automatically on-site. Due to various factors, such as the construction environment, construction schedule, and welder skill, welding defects are inevitable and may spread. To improve the inherent safety of pipelines during service, major domestic and international pipeline companies have adopted a common practice of conducting internal pipeline inspections. If girth weld anomalies are discovered, external inspections are conducted after excavation to verify the defect indications and to quantify and characterize the girth weld anomalies.

[0003] After excavation, external inspection uses a combination of inspection methods such as X-ray, ultrasound and TOFD (time difference method of ultrasonic diffraction). A common problem in on-site inspections is that the X-ray inspection results and TOFD inspection results are inconsistent, making it difficult to determine the defect disposal plan. This is due to the differences between the X-ray inspection method and the TOFD inspection method. If the general principles of non-destructive testing methods are followed, that is: when two or more inspection methods are used to inspect the same girth weld, the level should be assessed according to their respective methods, then these differences will lead to inconsistent inspection results. For example, during the 2017-2018 girth weld hazard investigation and control process of a pipeline company, in addition to the insensitivity of the internal detection signal to the girth weld, the important doubt encountered during the excavation inspection process was that the excavation re-inspection results could not correspond to the film re-evaluation. 2. Different non-destructive testing methods have completely different results in defect judgment. Among the 1,168 girth welds inspected during excavation, a total of 318 girth welds failed either radiographic testing or TOFD testing. Among them, 126 girth welds failed radiographic testing (level III / IV) but passed TOFD testing (level I / II). In addition, there were 102 girth welds whose radiographic testing results passed (level I / II) but failed TOFD testing (level III). The two together accounted for 72%, which greatly affected the decision-making plan for defect disposal.

[0004] A similar problem plagued the pipeline management department during a 2019 oil and gas pipeline girth weld excavation verification project at a certain pipeline company. Of the 61 unqualified girth welds inspected during excavation, 57, or 93%, passed radiographic testing (Level I / II) but failed TOFD testing (Level III). Determining the severity of girth weld defects based on TOFD results would require significant manpower and resources to address, and pose the risk of excessive maintenance. Therefore, a method for determining the severity of defects such as cracks, lack of fusion, slag inclusions, and porosity, when the results of radiographic and TOFD tests differ, was urgently needed to guide the investigation of girth weld hazards. Summary of the Invention

[0005] In order to address the above-mentioned defects in the prior art, the purpose of the present invention is to provide a method for determining the degree of hazard of pipeline girth weld defects, thereby providing a method for detecting and determining the degree of hazard of defects when the X-ray and TOFD test results are inconsistent in actual engineering, thereby meeting the needs of pipeline defect treatment.

[0006] The present invention is achieved through the following technical solutions.

[0007] The present invention provides a method for determining the degree of hazard of pipeline girth weld defects, comprising the following steps:

[0008] Step 1: Perform radiographic inspection and TOFD inspection on pipeline girth weld defects respectively;

[0009] Step 2: For the pipeline girth weld defects that failed the radiographic test but passed the TOFD test, the pipeline girth weld defects are judged as qualified based on the TOFD test results;

[0010] Step 3: Classify the pipeline girth weld defects that pass the radiographic test and fail the TOFD test, including surface open defects and buried defects;

[0011] Step 4: Determine the surface opening defects as hazardous defects;

[0012] Step 5: The buried defects are tested by TOFD, and the defective parts exceeding the standard are ultrasonically checked. If the ultrasonic check meets the ultrasonic testing standard Level II, it is considered acceptable. If it does not meet the ultrasonic testing standard Level II and is a linear defect exceeding the standard, it is considered unqualified.

[0013] Step 6: Unqualified buried defects are divided into point defects and linear defects. Point defects that exceed the standard and linear defects that do not exceed the standard are determined as acceptable defects; linear defects that exceed the standard are determined as hazardous defects.

[0014] In the above scheme, the qualified standard for radiographic inspection is Level II of SY / T 4109 "Nondestructive Testing of Petroleum and Natural Gas Steel Pipelines".

[0015] The TOFD test qualification standard is NB / T 47013.10 "Non-destructive testing of pressure equipment Part 10: Time-of-flight diffraction ultrasonic testing" Level II.

[0016] In the above solution, the opening defects include cracks on the inner and outer surfaces, lack of fusion on the outer surface, lack of fusion at the root and incomplete penetration at the root.

[0017] In the above solution, the buried defects include lack of fusion between layers, lack of fusion at the groove, incomplete penetration in the middle, slag inclusions and pores.

[0018] In the above scheme, the ultrasonic testing standard is SY / T 4109 "Non-destructive Testing of Petroleum and Natural Gas Steel Pipelines".

[0019] In the above scheme, the buried defects meet the TOFD detection NB / T 47013.10 "Non-destructive Testing of Pressure Equipment" Level II, and the defect areas exceeding the standard meet the ultrasonic detection standard SY / T 4109 "Non-destructive Testing of Petroleum and Natural Gas Steel Pipelines".

[0020] In the above solution, the point defects of the unqualified buried defects include small slag inclusions and pores.

[0021] In the above solution, the linear defects of the unqualified buried defects include interlayer lack of fusion, groove lack of fusion, middle lack of penetration and linear slag inclusion defects.

[0022] In the above solution, the point-shaped excessive defects are defects whose length cannot be measured by ultrasonic detection.

[0023] In the above solution, the linear defect exceeding the standard is a defect with a measurable length by ultrasonic detection.

[0024] The present invention adopts the above technical solution, which has the following beneficial effects:

[0025] The method disclosed in the present invention determines the degree of hazard of pipeline girth weld defects. The method performs nondestructive testing and actual precise measurement on girth weld defects when radiographic testing is qualified (level I / level II) and TOFD testing is unqualified (level III), and performs applicability evaluation on the defect with the largest metallographic measurement height among the samples that are qualified in radiographic testing and unqualified in TOFD, so as to determine the degree of hazard. Considering that there are many types of girth weld defects, in addition to testing and evaluating typical defect samples, the applicability evaluation is also performed on the limit sizes of defects that may occur under the on-site testing standards when radiographic testing is qualified and TOFD is unqualified. By analyzing the reasons for the qualified radiographic testing and the unqualified TOFD, a criterion for determining the degree of hazard of the defects in this case is given. The applicability evaluation of girth weld defects when radiographic testing is unqualified (level III / level IV) and TOFD testing is qualified (level II) shows that the defect evaluation results when radiographic testing is unqualified but TOFD testing is qualified are both acceptable, and the actual hazard is relatively small. In this case, the TOFD test results can be used as the basis for determination.

[0026] This method can reduce the number of unqualified girth welds. The application of judgment criteria can reduce the number of girth welds that require applicability evaluation and the number of girth welds that require repair by the operating unit, meet the needs of comprehensive pipeline inspection, evaluation, and repair, provide a scientific and reasonable operation and maintenance plan for the safe and reliable operation of the pipeline, and reduce unnecessary inspection, maintenance, and emergency repair work. Through the implementation of this method, the repair of defective points can be significantly reduced, effectively saving costs. If the use of methods such as pipe replacement and B-type sleeves is considered for repair, the process disposal costs and construction costs are calculated, and the cost savings are even more significant, with significant economic and social benefits. The design process is simple, easy to implement, low in economic cost, and highly reliable, making it convenient for major pipeline companies to promote and use girth weld hidden danger inspections and quality improvement on-site. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute an improper limitation of the present invention. In the drawings:

[0028] Figure 1 It is a process for determining the degree of hazard of girth weld defects when the X-ray and TOFD test results are inconsistent;

[0029] Figure 2 The X-ray and TOFD test images of a Φ1016×12.8mm defective sample;

[0030] Figure 3 This is the metallographic analysis diagram of the Φ1016×12.8mm wire-cut sample T1-1;

[0031] Figure 4 This is the metallographic analysis diagram of Φ1016×12.8mm wire-cut sample T2;

[0032] Figure 5This is the metallographic analysis diagram of the Φ1016×12.8mm wire-cut sample T3-2;

[0033] Figure 6 This is the applicability evaluation diagram of the T1-1-1 specimen with the largest defect height among the Φ1016×12.8mm wire-cut specimens;

[0034] Figure 7 This is the X-ray and TOFD inspection image of the Φ1219×18.4mm sample with defect 2-1;

[0035] Figure 8 This is the X-ray and TOFD inspection image of the Φ1219×18.4mm sample with defect 3-2;

[0036] Figure 9 This is the X-ray and TOFD inspection image of a Φ1219×18.4mm sample with 3-3 defects;

[0037] Figure 10 This is the metallographic analysis diagram of the Φ1219×18.4mm sample 2-1 with defects;

[0038] Figure 11 This is the metallographic analysis diagram of the Φ1219×18.4mm sample 3-2 with defects;

[0039] Figure 12 This is the metallographic analysis diagram of the Φ1219×18.4mm sample with defect 3-3;

[0040] Figure 13 This is the suitability evaluation diagram of the 3-3-2 specimen with the largest defect height among the Φ1219×18.4mm wire-cut specimens. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0042] like Figure 1 As shown, the method for determining the degree of hazard of pipeline girth weld defects established by the present invention includes the following steps:

[0043] Step 1: Perform radiographic inspection and TOFD inspection on pipeline girth weld defects respectively.

[0044] Step 2: For girth weld defects that fail the radiographic test (Level III) but pass the TOFD test (Level I / II), the pipeline girth weld defects are determined to be qualified based on the TOFD test results.

[0045] The qualified standard for radiographic testing is SY / T 4109 "Non-destructive Testing of Steel Pipelines for Petroleum and Natural Gas," Level II. The qualified standard for TOFD testing is NB / T 47013.10 "Non-destructive Testing of Pressure Equipment - Part 10: Ultrasonic Testing by Time of Flight Diffraction," Level II.

[0046] Step 3: Classify and count girth weld defects that pass radiographic testing (Level I / II) but fail TOFD testing (Level III): including girth welds with surface-open defects and girth welds with buried defects. Open defects include internal and external surface cracks, lack of fusion on the external surface, lack of fusion at the root, and lack of penetration at the root. Buried defects include lack of fusion between layers, lack of fusion at the groove, lack of penetration at the center, slag inclusions, and porosity.

[0047] Step 4: Determine the surface opening defects as hazardous defects.

[0048] Step 5: Use TOFD to detect buried defects, and conduct ultrasonic testing (UT) verification on the TOFD-exceeding defect areas of girth welds determined to be buried defects, and count the UT verification results: girth welds with qualified UT verification results and girth welds with unqualified UT verification results. Girth welds whose UT verification results meet the ultrasonic testing standard SY / T 4109 "Non-destructive Testing of Petroleum and Natural Gas Steel Pipelines" are qualified and are judged to be acceptable. Girth welds whose UT verification results do not meet the requirements of the ultrasonic testing standard and are unqualified need to determine their hazard level.

[0049] Step 6: Classify the girth welds that fail the UT verification in step 5 into point defects and linear defects according to the nature of the defects.

[0050] Among them, point defects of unqualified buried defects include small slag inclusions, pores, etc. Linear defects of unqualified buried defects include interlayer lack of fusion, groove lack of fusion, middle incomplete penetration, and linear slag inclusions.

[0051] Among them, the degree of hazard of point-like defects exceeding the standard and defective linear defects not exceeding the standard is judged to be acceptable, and linear defects exceeding the standard are judged to be hazardous defects and their applicability needs to be evaluated.

[0052] Among them, point-shaped defects are defects whose length cannot be measured by ultrasonic detection, while linear defects are defects whose length can be measured by ultrasonic detection.

[0053] According to the judgment criteria, the actual harm of the girth weld defect is relatively small if the X-ray detection result is unqualified (Level III / IV) but the TOFD detection is qualified (Level I / II), and it is judged to be qualified based on the TOFD detection result.

[0054] The effects of the present invention are further illustrated below by means of specific examples.

[0055] Taking the inspection and treatment of girth weld hazards of a pipeline company from 2017 to 2018 as an example, among the 1,168 girth welds inspected during excavation, 102 girth welds passed the radiographic inspection (level I / II) but failed the TOFD inspection (level III). In addition, there were 126 girth welds that failed the radiographic inspection (level III / IV) but passed the TOFD inspection (level I / II). A decision-making plan for defect disposal was required.

[0056] Example 1:

[0057] Take the Φ1016×12.8mm defective specimen as an example.

[0058] Step 1: Perform radiographic inspection and TOFD inspection on the girth weld defects of the Φ1016×12.8mm pipeline respectively. Figure 2 These are the X-ray and TOFD inspection images of a Φ1016×12.8mm defective sample.

[0059] Step 2: For the 102 girth weld defects that failed the X-ray test (Level III) but passed the TOFD test (Level I / II), the pipeline girth weld defects were determined to be qualified based on the TOFD test results.

[0060] Step 3: Classify and count the 102 girth weld defects that passed the X-ray test (Level I / II) but failed the TOFD test (Level III): 0 girth welds with surface open defects and 102 girth welds with buried defects.

[0061] Step 4: Determine the surface opening defects as hazardous defects.

[0062] Step 5: Use TOFD to detect buried defects. Perform ultrasonic testing (UT) on the 102 girth welds that are identified as buried defects and have TOFD defects exceeding the standard. Calculate the UT verification results: Figure 3 This is the metallographic analysis of the Φ1016×12.8mm wire-cut sample T1-1. The defect type in the figure is the lack of fusion at the groove; Figure 4 This is the metallographic analysis of the Φ1016×12.8mm wire-cut sample T2. The defects in the figure are interlayer lack of fusion and pores. Figure 5 This is the metallographic analysis diagram of the Φ1016×12.8mm wire-cut sample T3-2. The defect in the figure is the lack of fusion at the groove. It can be seen from the figure that the buried defects in the sample are mainly the lack of fusion between layers, lack of fusion at the groove, pores and other defects.

[0063] 76 girth welds passed the UT calibration results, and 26 girth welds failed the UT calibration results. The girth welds that met the UT calibration results (ultrasonic testing standard requirements) were judged to be acceptable, and the girth welds that did not meet the UT calibration results (ultrasonic testing standard requirements) needed to determine their degree of hazard.

[0064] Step 6: The 26 girth welds that failed the UT verification in step 5 are divided into point defects including porosity and linear defects including interlayer infusion and groove infusion according to the nature of the defects.

[0065] Among them, the hazard levels of 12 point-shaped defects that exceeded the standard and defective line defects that did not exceed the standard were determined to be acceptable, and 14 line-shaped defects that exceeded the standard were determined to be hazardous defects and their applicability evaluation was required. Figure 6 This is the applicability evaluation diagram of the T1-1-1 specimen, which has the largest defect height among the Φ1016×12.8mm wire-cut specimens. It can be seen from the figure that after the applicability evaluation, the evaluation result of the T1-1-1 specimen is acceptable.

[0066] The results of 126 X-ray inspections failed (Level III / IV) but passed the TOFD inspection (Level I / II). According to the judgment criteria, the actual harm of the girth weld defects is relatively small, and they are judged to be qualified based on the TOFD inspection results.

[0067] Example 2:

[0068] Take the Φ1219×18.4mm defective specimen as an example.

[0069] Step 1: Perform radiographic inspection and TOFD inspection on the girth weld defects of the Φ1219×18.4mm pipeline respectively. Figure 7 This is the X-ray and TOFD inspection image of the Φ1219×18.4mm sample with defect 2-1; Figure 8 This is the X-ray and TOFD inspection image of the Φ1219×18.4mm sample with defect 3-2; Figure 9 These are the X-ray and TOFD inspection images of a Φ1219×18.4mm sample containing 3-3 defects.

[0070] Step 2: For the 102 girth weld defects that failed the X-ray test (Level III) but passed the TOFD test (Level I / II), the pipeline girth weld defects were determined to be qualified based on the TOFD test results.

[0071] The qualified standard for radiographic testing is SY / T 4109 "Non-destructive Testing of Steel Pipelines for Petroleum and Natural Gas," Level II. The qualified standard for TOFD testing is NB / T 47013.10 "Non-destructive Testing of Pressure Equipment - Part 10: Ultrasonic Testing by Time of Flight Diffraction," Level II.

[0072] Step 3: Classify and count the 102 girth weld defects that passed the X-ray test (Level I / II) but failed the TOFD test (Level III): 0 girth welds with surface open defects and 102 girth welds with buried defects.

[0073] Step 4: Determine the surface opening defects as hazardous defects.

[0074] Step 5: Use TOFD to detect buried defects. Perform ultrasonic testing (UT) on the 102 girth welds that are identified as buried defects and have TOFD defects exceeding the standard. Calculate the UT verification results: Figure 10 This is the metallographic analysis of the defective sample 2-1 with a diameter of Φ1219×18.4mm. The defect types in the figure are lack of fusion at the groove, slag inclusion, and pores. Figure 11 This is the metallographic analysis diagram of the defective sample 3-2 with a diameter of Φ1219×18.4mm. There are no defects in the diagram. Figure 12 This is the metallographic analysis diagram of the Φ1219×18.4mm defective 3-3 sample. The defect type in the figure is unfused groove. It can be seen from the figure that the buried defects in the sample are mainly unfused groove, slag inclusions, pores and other defects.

[0075] 76 girth welds passed the UT calibration results, and 26 girth welds failed the UT calibration results. The girth welds that met the UT calibration results (ultrasonic testing standard requirements) were judged to be acceptable, and the girth welds that did not meet the UT calibration results (ultrasonic testing standard requirements) needed to determine their degree of hazard.

[0076] Step 6: The 26 girth welds that failed the UT verification in step 5 are divided into point defects such as slag inclusions and pores and linear defects such as lack of fusion at the groove according to the nature of the defects.

[0077] Among them, the hazard levels of 12 point-shaped defects that exceeded the standard and defective line defects that did not exceed the standard were determined to be acceptable, and 14 line-shaped defects that exceeded the standard were determined to be hazardous defects and their applicability evaluation was required. Figure 13 This is the applicability evaluation diagram of the 3-3-2 specimen with the largest defect height among the Φ1219×18.4mm wire-cut specimens. It can be seen from the figure that after the applicability evaluation, the evaluation result of the 3-3-2 specimen is acceptable.

[0078] The results of 126 X-ray inspections failed (Level III / IV) but passed the TOFD inspection (Level I / II). According to the judgment criteria, the actual harm of the girth weld defects is relatively small, and they are judged to be qualified based on the TOFD inspection results.

[0079] According to the pipeline company's statistics, before the application of the judgment criteria, 89 of the 102 girth welds that passed radiographic testing (Level I / II) but failed TOFD testing (Level III) required serviceability evaluation. After the evaluation, repair recommendations were given for three girth welds, and the pipeline company decided to repair 70 of them. After the application of the judgment criteria, only 14 of the girth welds required serviceability evaluation, of which three were recommended for repair, and the pipeline company decided to repair nine. The 126 girth welds that failed radiographic testing (Level III / IV) but passed TOFD testing (Level I / II) were deemed acceptable after the judgment criteria were applied and did not require serviceability evaluation.

[0080] It can be seen from the above results that the determination method established by the present invention can significantly reduce the repair of defect points, effectively save costs, and meet the actual needs of the project.

[0081] It should be noted that the above is only part of the embodiments of the present invention. Equivalent changes made to the system described in the present invention are all included in the scope of protection of the present invention. Those skilled in the art of the present invention may make similar substitutions for the specific examples described, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, and all such substitutions are within the scope of protection of the present invention.

Claims

1. A method for determining the degree of hazard of pipeline girth weld defects, characterized in that: The following steps are involved: Step 1: Perform radiographic inspection and TOFD inspection on pipeline girth weld defects respectively; Step 2: For the pipeline girth weld defects that failed the radiographic test but passed the TOFD test, the pipeline girth weld defects are judged as qualified based on the TOFD test results; Step 3: Classify the pipeline girth weld defects that pass the radiographic test and fail the TOFD test, including surface open defects and buried defects; Step 4: Determine the surface opening defect as a hazardous defect; Step 5: The buried defects are detected by TOFD, and the defective parts exceeding the standard are subjected to ultrasonic calibration. If the ultrasonic calibration meets the ultrasonic testing standard Level II, it is considered an acceptable defect; if it does not meet the ultrasonic testing standard Level II, it is considered unqualified; Step 6: Unqualified buried defects are divided into point defects and linear defects. Point defects and linear defects that do not exceed the standard are determined as acceptable defects; linear defects that exceed the standard are determined as hazardous defects.

2. The method for determining the degree of hazard of pipeline girth weld defects according to claim 1, characterized in that: The qualified standard for radiographic testing is SY / T 4109 "Nondestructive Testing of Petroleum and Natural Gas Steel Pipelines" Level II; The TOFD test qualification standard is NB / T 47013.10 "Non-destructive Testing of Pressure Equipment" Part 10: Time-of-flight Diffraction Ultrasonic Testing Level II.

3. The method for determining the degree of hazard of pipeline girth weld defects according to claim 1, characterized in that: The opening defects include internal and external surface cracks, lack of fusion on the external surface, lack of fusion at the root and incomplete penetration at the root.

4. The method for determining the degree of hazard of pipeline girth weld defects according to claim 1, characterized in that: The buried defects include lack of fusion between layers, lack of fusion at the groove, incomplete penetration in the middle, slag inclusion and pores.

5. The method for determining the degree of hazard of pipeline girth weld defects according to claim 1, wherein: The ultrasonic testing standard is SY / T 4109 "Non-destructive Testing of Petroleum and Natural Gas Steel Pipelines".

6. The method for determining the degree of hazard of pipeline girth weld defects according to claim 1, characterized in that: The point defects of the unqualified buried defects include small slag inclusions and pores.

7. The method for determining the degree of hazard of pipeline girth weld defects according to claim 1, characterized in that: The linear defects of the unqualified buried defects include interlayer lack of fusion, groove lack of fusion, middle lack of penetration and linear slag inclusion defects.

8. The method for determining the degree of hazard of pipeline girth weld defects according to claim 1, characterized in that: The point-shaped defect is a defect whose length cannot be measured by ultrasonic detection.

9. The method for determining the degree of hazard of pipeline girth weld defects according to claim 1, characterized in that: The linear excessive defect is a defect with a measurable length by ultrasonic detection.

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