FABBRICAZIONE, CONTROLLO NON DISTRUTTIVO E DELLA QUALITÀ DI STRUTTURE ED APPARECCHIATURE SALDATE
Sala LEVANTE / PONENTE 15:30 - 16:00
Saipem iAUT qualification on CRA partial weld in - spection in compliance with DNV-ST-F101 G. Didonna, F. Bragotto, T. dos Santos - Saipem Spa
Automated Ultrasonic Testing (AUT) it is a broad combination of UT te- chniques used for a productive and reliable full volume girth weld in- spection on the Oil & Gas pipeline market. AUT can be applied to a wide range of materials, but mostly C-Mn steels and CRA (Corrosion Resistant Alloys), typically manufactured on cladded linepipes. During offshore pipeline installation the welding process is divided in multiple stations to ensure the highest productivity rate. And when welding CRA pipeline, the area of the root and hot pass is the most critical to secure the inte- grity of corrosion barrier for the criticality of the fluid in contact with weld root, when the pipeline is in operation. Thus, dedicated acceptance cri- teria for root and hot pass, respect to the rest of the weld, are designed: in most instances, no root repair is allowed. In this case, the weld shall be cut-out, determining a remarkable impact on overall productivity. Based on the status of the current technology, the weld shall be cut after weld completion by the final AUT carried-out on the full weld. Hence the need to develop an AUT solution capable to inspect a weld partially completed, focusing on inspection of root and hot pass welding passes. The tailored solution is an intermediate automated ultrasonic inspection (iAUT) which covers an area within 4.5 mm from the ID surface, including CRA layer (typically 3.0mm thick) + the area up to 1.5 mm above clad/ lined thickness (transition area). iAUT uses a combination of zonal focal beams typical in the Final AUT set-up, plus an azimuthal scan focalized on the root / hot pass region, and a focused TOFD. This permits to have a more resolved image on the clad transition area.iAUT solution has been qualified according to the requirements of the main governing code for offshore “Submarine Pipeline Systems”, DNV-ST-F101. The qualifica - tion proved, through comparison between iAUT data versus final AUT assessment and macro sectioning the consistency and reliability of iAUT solution to have a localized overlook of these first welding passes on cladded pipelines and anticipate a cut-out (if any), with no significant discrepancy than the final AUT inspection methodology.
GNS 12 | Programma
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