Radiographic and Radioscopic Evaluation of Welding Defects in Natural Gas Pipeline Joints. Part 1: Film Radiography and Evaluation of Welding Defects

Résumé fourni par la source

This study assesses the structural integrity and weld quality of natural gas distribution pipeline joints using gamma-ray film radiography. Four hand-welded pipes of API 5L Grade B steel, with diameters ranging from 1½" to 6" and produced by the GTAW and SMAW processes, were radiographed using the ellipse and double-wall single-image exposure techniques with Ir-192 and Se-75 sources. The resulting films were evaluated against the acceptance criteria of API 1104 and ASME Section V. Porosity, lack of penetration, burn-through, concavity, and a base-metal manufacturing defect were identified and classified by density, length, and position relative to the weld root and cover passes. Burn-through and lack-of-penetration indications that exceeded the length limits set out in API 1104 Section 8 were rejected and required repair by grinding or rewelding, while porosity within the sensitivity limits of the technique was accepted. These findings show that at small pipe diameters, where control of the root pass depends heavily on the individual welder's skill, film radiography reliably separates acceptable indications from rejectable defects across a range of hand-welding methods.