Toughness index of low-temperature pipe of high steel grade used for the process pipelines at the station of China-Russia eastern natural gas pipeline

The China-Russia eastern natural gas pipeline is the first large-diameter (OD 1 422 mm) natural gas pipeline in China and it runs through the cold areas in northeastern China. In this paper, the design principles of process pipeline fracture control at the station of natural gas pipeline and the selection requirements of minimum design temperature were confirmed based on the comparative analysis and study of domestic and foreign standards and norms. First, in order to control the fracture of process pipelines at the station, it is fundamental to prevent the crack initiation, so the steel pipe should be tough enough to avoid the crack initiation. And the fracture propagation control index after the crack initiation and the Drop Weight Tear Test (DWTT) index shall be determined comprehensively according to specific project situations, combined with the domestic production level of low-temperature steel pipes. Second, when the minimum temperature is designed, it is necessary to consider the minimum temperature of the metal wall in the operational modes of normal operation, venting, throttling and shutdown & pressure maintaining. And the minimum design temperature of X70 and X80 pipes used for the process pipelines at the station is equal to the lowest ambient temperature. Third, it is recommended to take the lowest daily average temperature as the lowest ambient temperature of the process pipeline at the station of oil/gas pipeline. Finally, the low-temperature toughness indexes of X70 and X80 steel pipes used for the process pipeline at the station of China-Russia eastern natural gas pipeline were put forward based on theoretical calculation and physical performance parameter statistics. (4 Figures, 4 Tables, 22 References)