Residual stresses in girth welds of carbon steel pipes: neutron diffraction analysis

Abstract

In the oil and gas industry, residual stresses in welded components, such as risers and oil offloading lines, play a key role in determining their fatigue and fracture performance. The focus of this work is on measuring the residual stresses in girth welds of large diameter (508 mm, 20 in. outside diameter) thick walled (25·4 mm, 1 in. wall thickness) pipes. Residual stresses were measured using neutrons on two girth welds on X-65 grade line pipes. One was a carbon steel weld with fully ferritic weld metal, and the second was an Inconel 625 dissimilar weld with fully austenitic weld metal. It was observed that while there were subtle differences, the overall magnitude and distribution of axial and hoop residual stresses were comparable in the two girth welds. These data are consistent with available previous measurements and computer models from the literature.