Mechanical Properties of the China-russian Pipeline
Posted: 02/10/2023 07:41:13 Hits: 6
After the tee is welded, multiple drawings and heat treatments are required. Heat treatment will deteriorate the low-temperature performance of the tee’s welding seam, and the low-temperature toughness of the pipe fittings is the key to restricting the tee’s manufacturing capacity. The toughness index of the tee with a diameter of 1422 mm × 1 219 mm used in the China-Russia East Natural Gas Pipeline Project is determined based on the actual test level of the pipe fittings used in various projects in recent years, analyzing the accumulated test data, domestic and foreign technical standards.
ISO 15590-2-2003, BS EN 14870-2-2004, and DEP 31.40.21.33-Gen-2013 have the same regulations on the Charpy impact test indicators, and the influence of material strength is considered to determine the Charpy impact test. The standard does not distinguish between the pipe body, welding seam and heat-affected zone, and stipulates that the average impact energy of the transverse specimen of the pipe body, welding seam and heat-affected zone should be one-tenth of the minimum yield strength; the minimum impact energy of a single specimen should not be less than 75% of the required average value; the requirements for the shear area should be negotiated and determined. If it is negotiated to increase the shear area index, the minimum average shear area of the failure sample should be 50% of the total cross-section. The shear area of a single sample should not be less than 40% of the total section.
CSA Z245.11-2005, MSS SP-75-2014, SY/T 0609-2016 and other standards stipulate that for pipe fittings with steel grade not less than X52, the impact absorption energy of the pipe body shall not be less than 27J. CSA Z245.11-2005 and SY /T 0609-2016 allow higher requirements to be put forward through negotiation based on engineering reality.
ТУ 1469-012-04834179-2008 stipulates that the Charpy impact energy of the welding seam and heat-affected zone is lower than that of the pipe body. For pipe fittings with a wall thickness greater than 25 mm, when V-notch specimens are selected, the average Charpy impact energy of the pipe body shall not be less than 70 J for У-type pipe fittings at the test temperature. The average Charpy impact energy of the welding seam and heat-affected zone is not less than 57 J. For УХЛ fittings, the average Charpy impact energy of the pipe body is not less than 59 J, and the average Charpy impact energy of the welding seam and heat-affected zone is not less than 49 J. When the U-shaped notch sample is selected, the average Charpy impact energy of the pipe body and the welding seam of the У-type and УХЛ pipe fittings are the same at the test temperature; the average Charpy impact energy of the pipe body is not less than 59 J. The average Charpy impact energy in the area is not less than 49 J (Table 1).
Table 4 Temperature and energy indicators of Charpy impact tests of pipe fittings on the China-Russia East Pipeline
ISO 15590-2-2003, BS EN 14870-2-2004, and DEP 31.40.21.33-Gen-2013 have the same regulations on the Charpy impact test indicators, and the influence of material strength is considered to determine the Charpy impact test. The standard does not distinguish between the pipe body, welding seam and heat-affected zone, and stipulates that the average impact energy of the transverse specimen of the pipe body, welding seam and heat-affected zone should be one-tenth of the minimum yield strength; the minimum impact energy of a single specimen should not be less than 75% of the required average value; the requirements for the shear area should be negotiated and determined. If it is negotiated to increase the shear area index, the minimum average shear area of the failure sample should be 50% of the total cross-section. The shear area of a single sample should not be less than 40% of the total section.
CSA Z245.11-2005, MSS SP-75-2014, SY/T 0609-2016 and other standards stipulate that for pipe fittings with steel grade not less than X52, the impact absorption energy of the pipe body shall not be less than 27J. CSA Z245.11-2005 and SY /T 0609-2016 allow higher requirements to be put forward through negotiation based on engineering reality.
ТУ 1469-012-04834179-2008 stipulates that the Charpy impact energy of the welding seam and heat-affected zone is lower than that of the pipe body. For pipe fittings with a wall thickness greater than 25 mm, when V-notch specimens are selected, the average Charpy impact energy of the pipe body shall not be less than 70 J for У-type pipe fittings at the test temperature. The average Charpy impact energy of the welding seam and heat-affected zone is not less than 57 J. For УХЛ fittings, the average Charpy impact energy of the pipe body is not less than 59 J, and the average Charpy impact energy of the welding seam and heat-affected zone is not less than 49 J. When the U-shaped notch sample is selected, the average Charpy impact energy of the pipe body and the welding seam of the У-type and УХЛ pipe fittings are the same at the test temperature; the average Charpy impact energy of the pipe body is not less than 59 J. The average Charpy impact energy in the area is not less than 49 J (Table 1).
Table 4 Temperature and energy indicators of Charpy impact tests of pipe fittings on the China-Russia East Pipeline
| Standards | Positions | Average values of Charpy impact test impact absorption energy/J | Single minimum value | CVN shearing area | |
| ISO 15590-2-2003 | Base metal, welding seams and heat-affected zones | 55.5 | 41.6 | Average values | Single minimum value |
| BS EN 14870-2-2004 | Base metal, welding seams and heat-affected zones | 55.5 | 41.6 | ||
| DEP 31.40.21.33-Gen-2013 | Base metal, welding seams and heat-affected zones | 55.5 | 41.6 | ||
| GB/T 29168.2-2012 | Base metal, welding seams and heat-affected zones | 50 40 |
40 30 |
||
| CSA Z245.11-2005 | Base metal, welding seams and heat-affected zones | 27 | - | No requirements | No requirements |
| MSS SP-75-2014 | Base metal, welding seams and heat-affected zones | 27 | 20.3 | 20.3 | Providing reports No requirements |
| SY/T 0609-2016 | Base metal, welding seams and heat-affected zones | 27 | - | - | Providing reports Providing reports |
| ТУ 1469-012-04834179-2008 | Base metal, welding seams and heat-affected zones | 59 49 |
- - |
- - |
No requirements |
Please pay attention to the following aspects:
1) If the requirements for increasing the shear area index are determined through negotiation, the minimum average shear area of the failed sample shall not be less than 50% of the total section, and the shear area of a single sample shall not be less than 40% of the total section.
2) If required by the owner, the index can be increased.
3) If the above requirements are not met, the same sample at the same position can be selected for retesting, and the test value of a single sample should not be less than the minimum value of the average impact absorbed energy.
4) According to the project in practice, higher requirements can be put forward through negotiation.
5) U-shaped notch samples can be used; the test temperature should be -60°C, and the impact energy index is the same as that of the V-notch impact energy index.
For the tee with a diameter of 1 422 mm X 1 219 mm used in the China-Russia Natural Gas Pipeline Project, China National Petroleum Corporation carried out technical research, adopted finite element analysis, and considered the wall thickness effect of the tee and the stress concentration of the structure to establish the finite element model of the tee with defects, using the defect evaluation method and applying the theory of fracture mechanics, establishing the failure evaluation curve of the tee based on the actual stress-strain behavior of the material, and determining the fracture control index of the low-temperature brittle tee with a diameter of 1422 mm×1219 mm at the low-temperature station of the China-Russia Pipeline. The brittle initiation of pipe fittings is controlled in the low temperature of the station. The calculated minimum Charpy impact energy to ensure that the x 80 tee used in the China-Russia pipeline does not crack: the welding seam position is 32.22 J; the tee belly is 32.85J, and the tee shoulder is 38.85J. According to the analysis and results, the toughness index of the tee with a diameter of 1422 mm x 1219 mm used in the China-Russia Natural Gas Pipeline Project is determined, and a full-size (10 mm x 10 mm x 55 mm) Charpy impact test at -45°C is required. The test results are used as acceptance conditions. It is required to conduct a full-size (10mm x 10mm x 55mm) Charpy impact test at -60°C and report the test results. Determine the Charpy impact energy index of the X80 tee used in the China-Russia Project: the average impact energy of the pipe body is not less than 60J, and the single minimum value is not less than 45 J; the average impact energy of the welding seam and heat-affected zone is not less than 50 J, The single minimum value is not less than 40J.
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