UT Quality/Technology & insightsInsights/Heavy-wall weld inspection
The thicker the wall, the more radiography has to work for the same sensitivity — longer exposures, and a heavier source (Se-75, Ir-192, then Co-60 or a linear accelerator) as penetrated thickness grows. An encoded PAUT/AUT scan reads a girth weld in minutes and sizes planar flaws, and its scan time barely moves with wall thickness — it is set mainly by pipe circumference, with more depth zones added as the wall gets thicker.
As wall thickness grows, radiographic exposure time rises and sensitivity falls, and past the practical range of Ir-192 (about 2.5" of steel) the job moves to a Co-60 source or a linear accelerator. Ultrasonics hold roughly 5–10 minutes a weld, set mainly by pipe circumference rather than by how much steel the beam has to penetrate.
Inspection time as steel thickness increases
UT Quality PAUT / AUT
per weld — near-flat with wall thickness. Detects and sizes planar flaws — the lack-of-fusion and crack-type defects that are difficult to see with conventional radiography, with height, depth and length for ECA acceptance criteria.
Radiography (RT)
Time and required source energy climb with penetrated thickness. On an external double-wall shot the beam crosses both walls — twice the wall thickness — and sensitivity is poorer than a single-wall crawler shot. Above about 2.5" of penetrated steel, Ir-192 runs out of practical range and the work moves to a Co-60 source or a linear accelerator — longer set-ups, bigger exclusion zones, more schedule.
On mainline and tie-ins — disposition at the weld, with a recordable digital file behind every call.
UT is operator-dependent, so every UT Quality crew works to a written procedure with Level III oversight of interpretation — keeping calls consistent, auditable and reviewable.
UT Quality fields PAUT and AUT crews built for thick-wall, high-restraint pipeline and station welds.
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