Summary
Radiography has long been the default method for Code-required weld acceptance testing, and as settled practice it raises few questions. On an active job site it raises a schedule problem. A radiation source demands a personnel exclusion zone, so welders and surrounding craft clear the area for the duration of every exam, and exposure and processing time delay the result after they return. Acceptance testing becomes a serial activity inside new construction, replacement piping, and outage repair schedules that have no room to accommodate one. In power generation and nuclear work in particular, the meaningful cost is rarely the examination itself — it is everything standing idle while it runs.
Advances in ultrasonic examination, and in phased array ultrasonic testing (PAUT) specifically, have produced systems that achieve sensitivities equivalent to or better than traditional radiography while eliminating the radiation altogether. Structural Integrity has developed and demonstrated PAUT procedures in compliance with a range of industry Codes and Standards. In most instances ASME B31.1 supplies the specific requirements governing pressure piping weld acceptance when ultrasonic testing is performed in lieu of radiography, with B31.3 and applications of ASME Case 189 available as scope requires. Because there is no source to shield, examinations proceed within proximity to welding and other craft with no exclusion zone and no lost production, and typically deliver a 50 percent or better improvement in total process production.
What the method returns differs in kind as well as in speed. PAUT results display in near real time, so the operator screens flaws and judges data quality while the scan is running rather than after processing. Through-wall depth sizing and volumetric positioning are accurate enough to bound a repair excavation tightly, which shortens the repair that follows. The equipment is portable and lightweight, handled by a small team, with minimal impact on surrounding work activities. And the data, as ASME B31.1 requires, is digitally recorded — captured, archived, and retained as a permanent record available for future reference.
Method availability is not the same as demonstrated capability. Leaning on decades of supporting ASME Code development, interpretation, and compliance, Structural Integrity applied PAUT in lieu of Radiography Testing on an ASME Class 1 component before anyone else in the industry. Comprehensive scan plans are supported by extensive 3D ultrasonic beam modeling to confirm that the full examination volume is covered, and Level III personnel review and approve every scan plan, focal law, and essential requirement before a technician reaches the weld. Where Code rules do not exist or do not address a configuration, SI’s engineering organization develops component-specific flaw acceptance criteria — the same integration of nondestructive examination and analysis that allows a finding to move directly into evaluation rather than waiting on a second vendor.