'Improved Focusing for Pipeline Girth Weld Inspections using Phased Arrays'

摘要

Since Engineering Critical Assessment (ECA) became a standard procedure for assessing pipeline girth weld defects, sizing defects has become a major issue. Despite claims and requests for better sizing, most pipeline trials have shown that sizing accuracies are only within ～ ±1 mm at best in the vertical (through-wall) direction, and typically worse in the horizontal (circumferential) plane due to beam spread. Defect sizing requirements are becoming more stringent as new high strength pipes and new applications are being introduced. This applies to both thin-walled onshore pipelines and to thick-walled offshore pipelines, particularly tendons and risers where fatigue life is critical. This project has developed a curved 2D matrix array, primarily for improving focusing in the horizontal direction on thick-walled risers and tendons. Initially, the focusing was modeled for a variety of arrays, including the standard array, flat and curved arrays. The optimum array turned out to be 120 elements long, with three rows, plus a slight curvature for initial focusing. Detailed focusing can be performed using the electronic capability of phased arrays. Normal PipeWIZARD phased arrays use 60 element arrays on either side of the weld; in contrast, the new array uses 360 elements for one-side only inspection. The results from this array will be compared with standard focusing from a single 1D array on a typical calibration block.