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Why Prime/Heavy-Wall Weld Inspection

On heavy wall, radiography gets slower and ultrasonics do not

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The thicker the wall, the more radiography has to work for the same sensitivity — longer exposures and a heavier source. Ultrasonic scan time barely moves, and encoded AUT/PAUT is accepted in lieu of RT where the code and the owner permit it.

Time & difficulty to a usable result vs. wall thickness

Inspection time and difficulty versus steel thickness Automated ultrasonics stay near-flat at roughly 5 to 10 minutes a weld across pipeline wall thicknesses, adding depth zones as the wall thickens. Radiographic exposure rises with the thickness of steel in the beam; past the practical iridium-192 range of about 2.5 inches the work moves to cobalt-60 or a linear accelerator. AUT / PAUT Radiography (RT) 0.25 0.5 1 1.5 2 2.5 3 time / difficulty → steel thickness in the beam (inches) AUT / PAUT — 5–10 min per weld, near-flat with wall thickness Ir-192 practical limit ≈ 2.5" of steel Co-60 or linac above RT: longer exposures, lower sensitivity as steel thickness grows 48" double-wall shot, 1" wall ≈ 2" in the beam Inspection time and difficulty versus steel thickness Automated ultrasonics stay near-flat at roughly 5 to 10 minutes a weld across pipeline wall thicknesses, adding depth zones as the wall thickens. Radiographic exposure rises with the thickness of steel in the beam; past the practical iridium-192 range of about 2.5 inches the work moves to cobalt-60 or a linear accelerator. AUT / PAUT Radiography (RT) 0.5 1 2 2.5 3 ↑ time / difficulty steel thickness in the beam (in.) Ir-192 limit ≈ 2.5" of steel AUT / PAUT — 5–10 min, near-flat Past ≈2.5": Co-60 or a linear accelerator 48" double-wall shot, 1" wall ≈ 2" in beam
External double-wall shot on 48" pipe: the beam crosses both walls — twice the wall thickness — so sensitivity is poorer than a single-wall crawler shot. Radiography: longer exposures and lower sensitivity as the steel in the beam grows, and past the practical Ir-192 range (about 2.5" of penetrated steel) the work moves to Co-60 or a linear accelerator. Prime PAUT / AUT: 5–10 min per weld, near-flat with wall thickness.

Detects and sizes planar flaws

Cracks and lack of fusion RT can under-call.

Immediate encoded results

On mainline and tie-ins — disposition at the weld.

Interpretation, controlled. UT is operator-dependent — so Prime can back every crew with remote Level III interpretation and a defined, written process, keeping calls consistent, auditable, and reviewable.

Related resources

Why Prime InspectionsExperience + Equipment + Productivity = fewer delays, lower risk, and a partner that scales with you.Automated Ultrasonic Testing100 AUT systems ready to deploy. Encoded PAUT and TOFD, mainline to tie-ins.Digital vs Conventional RTCount the darkroom, and digital wins at every pipe size.AUT vs RadiographyWhere radiography is still the right call.

Heavy-wall spread coming up?

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