Volumetric & Advanced NDT · PAUT
Phased Array Ultrasonics
Dozens of elements, one steered beam, a picture instead of a blip.
Phased array ultrasonic testing (PAUT) uses a probe containing many small elements — typically 16 to 64 — fired with precise time delays so their wavefronts combine into a single beam that can be steered and focused electronically. One probe position sweeps a whole fan of angles through a weld, painting an image of its interior rather than a single-angle signal.
The explainer
Watch how it works.
Schematic · loops automatically
1An array, not a crystal
The probe carries dozens of individually-wired elements — each a tiny transmitter and receiver.
2Delays shape the beam
Firing the elements with programmed nanosecond offsets tilts and focuses the combined wavefront — steering without moving the probe.
3The fan sweeps the weld
Delay laws cycle through a range of angles; the sectorial scan interrogates the full weld volume from one position.
4Echoes become an image
Returns from every angle assemble into a live cross-section — defects appear as positioned, coloured indications.
5Encode and archive
Scanning along the weld with a position encoder records the entire joint as reviewable data — sized, located, permanent.
The physics
The principle is wave interference. Each element launches its own wavelet; fire them simultaneously and the wavefront travels straight ahead, but stagger the firing by nanosecond delays and the combined wavefront tilts — the beam steers. Curve the delay pattern and the wavefronts converge — the beam focuses. The “phase” in phased array is exactly those programmed delays.
Sweep the delay laws electronically and one stationary probe interrogates a weld across a fan of angles — the sectorial scan — with every angle’s echoes assembled into a live cross-sectional image. Encode the probe’s position along the weld and the instrument records a complete, repeatable volumetric dataset: every millimetre of weld, every angle, stored and reviewable like a radiograph but with depth information radiography cannot give.
This is why PAUT has become the accepted alternative to radiography on many weld classes: comparable coverage codified in EN ISO 13588, no exclusion zones, immediate results, and encoded data that a second reviewer — or a client auditor — can replay years later. It remains ultrasound, so coupling, calibration and technician skill still decide the quality of everything recorded.
Where it earns its keep
Typical applications
- Radiography replacement on pipework and vessel welds — no exclusion zones
- Critical weld examination with encoded, auditable data
- Corrosion and erosion profiling with electronic raster coverage
- Nozzle, node and complex-joint examination with modelled scan plans
Standards & schemes
| Designation | Covers |
|---|---|
| EN ISO 13588 | Ultrasonic testing of welds — phased array technology |
| EN ISO 19285 | Acceptance levels for phased array testing of welds |
| EN ISO 18563 series | Characterisation and verification of phased array equipment |
PAUT is delivered by advanced-technique technicians certified under ISO 9712 with phased-array endorsement, working to parametric scan plans reviewed at Level 3.
Can PAUT fully replace radiography?
For many weld classes, yes — EN ISO 13588 with EN ISO 19285 acceptance gives a codified route, and clients gain time (no exclusion zones), depth-sized defects and encoded records. Some codes, materials or thin-wall cases still favour RT; we advise against the actual contract specification.
What does “encoded” mean and why does it matter?
A position encoder ties every ultrasonic firing to a location along the weld, so the instrument stores a complete map rather than a technician’s summary. Encoded data can be re-analysed, second-reviewed and audited — the difference between “we tested it” and “here is the whole weld, look for yourself.”
Is PAUT better than TOFD?
They answer different questions and are often run together: PAUT excels at detection and characterisation across the weld volume; TOFD adds the most accurate through-wall sizing of planar defects. Combined PAUT+TOFD scanning is the premium weld-examination package for critical joints.
Delivered through
Testing · Inspection · Certification
Need PAUT on your asset?
Describe the component, the material and the question — a specialist confirms the technique, the standard and the turnaround.