Grade 550 (X80) pipeline steels are now the basis of a standard platform for the design and construction of large-diameter pipeline projects at NOVA Gas Transmission (NGT). Their introduction in 1995 and further application in 1997 have provided material savings, provided greater gas flow capacity and fuel gas savings and, once again, shown NGT to be an industry leader in successfully developing and applying new technology in response to business needs. The paper will outline the development of a Canadian capability to supply these steels, discuss design aspects including fracture initiation and arrest and weld/pipe strength mismatch, the overall cost efficient approach to material and weld requirements, and pipeline construction using mechanized welding with mechanized ultrasonic inspection and alternative weld acceptance standards. Future directions at NGT with respect to higher strength steels will also be described.

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