L51880 Influence of Higher Design Factor on Structural Integrity of X70 and X80 Pipelines

Most pipelines in Class 1 areas are currently designed to a utilization factor of 0.72 using steel grades of up to X70. Using higher strength steels and/or a higher design factor can reduce the wall thickness and construction cost of such pipelines. High strength steels tend to have high yield-to-tensile ratios and lower overall post-yield tangent stiffness. This raises concerns about the potential for excessive plastic deformations under high hydrostatic test pressures. Combined with a high design factor, high steel grades will also lead to thinner pipe walls and reduced tolerance to thickness-dependent failure mechanisms such as corrosion, cracks, and dent-gouges. This effort evaluates the ability of a newer pipelines to safely operate at higher yield stresses.