Failure Characteristics and Defect Tolerance Levels of Girth Welds in Large Diameter X 65 / X 70 Steel Linepipes: Experimental Verification through Wide Plate Testing and Comparison with ECA Prediction Models

摘要

Experimental work has been undertaken to quantify the failure characteristics and defect tolerance levels of a series of girth welds made by SMAW and GMAW welding in large diameter API 5L X 65 / X 70 linepipes. This objective was achieved by tensile testing of curved wide plates provided with artificial surface breaking root defects. In addition, the tensile and notch and fracture toughness properties of the welds have been determined by small-scale testing. The experimental data have been compared with the predictions of current ECA methodologies. The experiments and subsequent analysis of the data have shown that current ECA codes yield, in general, safe predictions of tolerable defect sizes for surface defects in pipeline girth welds provided weld metal yield strength overmatching is guaranteed. The degree of conservatism of the predictions is, however, variable. API 1104 -App. A incorporates the lowest, and EPRG Tier 2 the highest level of safety against girth weld failure.