Vigorously develop natural gas long-distance transmission pipeline

Standard recommendations Some foreign pressure vessels and pressure pipeline manufacturing standards are similar. With such regulations, a large number of welds were reworked due to excessive blowholes and slag inclusions. Shan 6 once reported the investigation of the repair of the main welds of pressure vessels in the United Kingdom. These rework defects have about 84 slag inclusions, 3 are dense pores 13 is a plane defect. Due to the above circumstances, foreign countries began to use the pressure vessel inspection standards in the late 1960s in accordance with the principle of appropriate use. According to the hazards of the defects, it was reasonably relaxed compared with the manufacturing standards, and the first welded structure was promulgated in 1976. In accordance with the evaluation standards of Fenghang, the evaluation of the combined use of pressure vessels in foreign countries has greatly relaxed the restrictions on air holes and slag inclusions. The most representative of which is the United Kingdom, 64931991. For the yield strength, 450MPa, at the lowest use, the V-shaped notch under the degree of ferrite steel and the impact energy of 4, 25, and the claw 1 allows the projection of the pores in the weld on the radiograph to reach 5, allowing a single The diameter of the stomata is equal to the wall thickness or the smaller of 6,1.

The maximum height or width of the slag allowed in the weld is 3, and the length is not limited.

Based on the above, in the inspection regulations for in-use pressure vessels promulgated by the Ministry of Labor in 1990, it is necessary to relax the allowable pores and slag inclusions in the welding seam from the manufacturing standards, and it is also perfected by reasonable experience.

5,443,1973.2 Yingzha double. Editor-in-Chief of Nichols. Defect analysis Beijing Machinery Industry Press, 1991.

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