Implications and Trends in SMYS Built Into Pipelines

For many the use of SMYS in conjunction with working-strength design for pipelines leads to the expectation that the least strength of the joints in the pipeline is at or above SMYS. In contrast, regulations relevant to pipeline operation reference specifications require limited testing to demonstrate the acceptance of pipe joints made from a “heat” of steel, and where such testing fails such specifications admit a retest. Thus, contrary to the expectation of that all joints constructed into a pipeline achieve SMYS, the statistical reality is that some joints can have strengths that fall below this design expectation. This paper considers the implications of changes due to the globalization of the steel and pipe-making industries relative to the historical evolution of classes/grades of steel and their processing in regard to the statistical properties of line pipe built into a pipeline. It is shown for the data evaluated that, in spite of globalization and other aspects that tend to diminish quality such as increasing heat-volume, controls affected in steel and pipe production can lead to better quality today as compared to historical scenarios. Circumstances that can compromise this outcome are identified and discussed.