According to ASME Section V Article 4 (2019) and ISO 13588:2019, phased-array ultrasonic testing (PAUT) has become a primary tool for detecting and sizing defects in welded joints. A key distinction in PAUT interpretation is the difference between planar and volumetric defects.
Planar defects, such as cracks, lack of fusion, and incomplete penetration, are flat and oriented perpendicular to the stress direction. They pose a high risk of brittle fracture and require precise sizing. Volumetric defects, like porosity, slag inclusions, and gas pockets, are three-dimensional and generally less critical unless they cluster or exceed acceptance criteria.
PAUT's ability to steer the sound beam electronically allows for multiple angles in a single scan, making it highly effective for detecting planar defects in difficult geometries. The technique provides superior probability of detection for planar flaws compared to conventional UT, especially in thick-section welds.
However, proper calibration and setup are essential. False calls can occur if the inspector does not distinguish between geometric echoes and actual defects. Training and experience remain critical.
How does your team handle the classification of planar versus volumetric indications in PAUT?
Source: ASME Section V, 2019