API · ASME · ISO · NIST · UKAS
Advanced phased array ultrasonic testing for high-resolution imaging and precise detection of internal defects in welds and critical industrial components.
Phased Array Ultrasonic Testing (PAUT) uses a probe containing many small elements that are pulsed with precise time delays, so the ultrasonic beam can be electronically steered through a range of angles and focused at chosen depths from a single, stationary probe. The result is a real-time cross-sectional image (sectorial or S-scan) of the weld.
Combined with an encoder, PAUT produces a fully recorded, mappable dataset — increasingly accepted as an alternative to radiography. We frequently pair it with Time-of-Flight Diffraction (TOFD) for accurate flaw height sizing and complete weld-volume coverage.
The probe holds an array of typically 16, 32 or 64 piezoelectric elements. By firing them with programmed time delays (phasing), the individual wavelets combine to form a single wavefront that can be swept through a range of angles (a sectorial or S-scan) or kept at a fixed angle and moved along the weld — all without moving the probe.
The returning echoes are reconstructed into colour cross-sectional images that show the position, depth and through-wall extent of reflectors, making interpretation far more intuitive than a single-channel A-scan.
Sectorial scanning sweeps many angles across the weld bevel in a single pass, so lack of fusion and cracks on the fusion faces are reliably caught. Time-of-Flight Diffraction (TOFD) complements it by measuring the tiny diffracted signals from the tips of a flaw, giving highly accurate through-wall height even for defects that specular reflection would under-size.
Used together and encoded, PAUT and TOFD give near-complete weld-volume coverage with a permanent, auditable record — the basis for engineering-critical fitness-for-service assessment.
The kit is a multi-channel phased-array instrument, array probes with hard-faced wedges, an encoder and scanner, and calibration blocks matching the geometry. A focal law (scan plan) is programmed for the joint thickness and bevel, and the system is calibrated for wedge delay, sensitivity (TCG) and encoder resolution before scanning.
Data is stored as encoded scans that can be re-analysed, overlaid on the weld map and archived — supporting independent review and long-term integrity records.
Indications are reported with position along the weld, depth, length and through-wall height, and evaluated either to workmanship criteria (e.g. ASME BPVC Section VIII, API 1104) or by fracture-mechanics-based fitness-for-service where the code permits. Encoded data lets a Level III review the scans independently.
Procedures follow ASME BPVC Section V and ISO 13588 / ISO 19285, and personnel hold PAUT/TOFD certification under ISO 9712 or SNT-TC-1A. The output is a complete report with the scan plan, calibration and imaged results.
In many cases yes. Modern codes (e.g. ASME Section VIII code cases, API 1104 and ISO 13588) accept encoded PAUT — often with TOFD — as an alternative to radiography, especially on thicker welds. It removes radiation-safety exclusion zones, gives instant imaged results and superior crack sizing. The substitution must be agreed with the client and covered by a qualified written procedure.
TOFD measures the diffracted signals from the tips of a flaw rather than the reflected signal from its face, which makes it very accurate for through-wall height and excellent for monitoring crack growth. Paired with PAUT — strong on detection and location — the combination gives both reliable detection and precise sizing for fitness-for-service.
An encoder ties every ultrasonic reading to a precise position along the weld, so the whole scan is stored as a mappable, permanent record. That data can be re-analysed by a Level III, audited by a third party, and compared against a later scan to track any flaw growth — something a manual, non-recorded UT cannot provide.
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