Fracture Control of the 2nd West to East Gas Pipeline in China

The 2nd West to East Gas Pipeline ( WEGP) is the first major pipeline project in China importing abroad natural gas and also the longest and largest gas transmission pipeline in the world with gas supply of Middle Asian natural gas and adjusting gas supply of domestic gas from Tarim Basin and Ordos Basin. Its total length is 9 000 kilometers, in which the total length of artery from Khorgos to Guangzhou is 4 900 kilometers. Its design throughput is 30 billion cubic meters per year. Designed maximum operation pressure is 12 MPa, largest diameter of pipe is 1219mm and highest steel grade is X80. To ensure the long-term safety and reliability in operation, fracture control program has been proposed through systematic research, including crack initiation control, brittle fracture control and ductile long-running fracture control. The requirement of arrest toughness of the 2nd WEGP had been studied on the basis of pipe full-scale burst test data base in the world, Battelle Two Curve (BTC) method and GasDecom software. Full-scale burst tests of X80 high-pressure gas pipeline had been successfully performed based on previous research results. The fracture control program was set up based on different fracture criteria and the principle of both safety and economy. The crack arrest ability of X80 spiral submerged arc welded (SSAW) steel pipe was firstly verified and a new correct factor of arrest toughness prediction was obtained. Results presented that the crack arrest ability of SSAW pipe is better than longitudinal submerged arc welded (LSAW) pipe. It lays a solid foundation for the safe operation of the X80 pipeline after construction and completion.