PAUT · Advanced NDT
Phased Array Ultrasonic Testing
The Method
How phased array works.
A phased array probe contains many small piezoelectric elements — commonly 16 to 128 — in a single housing. The instrument pulses those elements with precisely calculated time delays, called focal laws. Changing the delays steers and focuses the ultrasonic beam electronically, with no change of probe or wedge.
From one probe position, the beam can sweep through a range of refracted angles (a sectorial or S-scan), or step along the length of the array at a fixed angle (a linear or E-scan). The results are displayed as cross-sectional images of the weld and heat-affected zone, alongside the conventional A-scan.
Paired with an encoder, each scan is tied to its position along the weld. The full data set is saved, so it can be analyzed after the scan, reviewed by a second qualified analyst, and kept as a permanent inspection record.
Why PAUT
Benefits for complex inspection requirements.
Coverage from fewer passes
Multiple angles from one probe position cover the weld volume, often with a single line scan parallel to the weld.
Imaging for characterization
Sectorial and encoded views show where an indication sits in the weld geometry, supporting characterization and sizing.
Complex geometry
Beam steering and focusing help reach areas that are difficult to cover with fixed-angle probes, such as nozzles and restricted-access welds.
PAUT vs. Conventional UT
How the two compare.
| Aspect | Conventional manual UT | Phased array UT |
|---|---|---|
| Beam angle | One fixed angle per probe and wedge | Range of angles steered electronically from one probe |
| Scanning | Raster scanning by hand | Line scanning, often encoded |
| Display | A-scan | A-scan plus sectorial, linear, B- and C-scan views |
| Record | Report of recorded indications | With encoded scanning, the full data set is saved for review and archive |
| Setup | Simpler calibration | Scan plan, focal laws, and encoder calibration required |
Applications
Where PAUT is used
- Butt welds in plate and pipe
- Structural and pressure-boundary welds in shipbuilding, where specified
- Nozzle, branch, and other complex-geometry welds
- Volumetric examination in lieu of radiography, where the governing code permits
- Corrosion mapping and wall-loss assessment
- Repair verification on previously examined welds
Detection and characterization
Detection and characterization
- Lack of fusion — sidewall, interpass, and root
- Cracks and other planar discontinuities
- Incomplete penetration
- Volumetric discontinuities such as slag and porosity
- Indication length, depth, and through-wall height, where the procedure includes sizing
Methods & Equipment
Typical equipment
- Multi-channel phased array flaw detectors
- Linear array probes with angle and zero-degree wedges
- Position encoders and manual or semi-automated scanners
- Scan-planning and focal-law software
- Calibration and reference blocks specified by the procedure
Technical Considerations
Limits and requirements to plan for.
Scan plan
Coverage is designed up front: probe position, angles, and focal laws are chosen to cover the weld volume and heat-affected zone for the joint geometry.
Calibration
Wedge delay, sensitivity, time-corrected gain, and encoder calibration are verified before scanning and checked as the procedure requires.
Material
Coarse-grained materials such as austenitic welds scatter sound and may need specialized probes and techniques.
Analysis
Encoded data is only as good as its interpretation. Analysts must be qualified for PAUT specifically, not only for conventional UT.
In Practice
PAUT in industry.
Naval shipbuilding
Volumetric weld examination where specified, with encoded data that supports customer review.
Industrial fabrication
Production weld inspection on plate, pipe, and pressure equipment with faster coverage on long seams.
Power & process piping
Weld examination and corrosion mapping during construction and outages.
How TCI Supports You
What you get from TCI.
- Qualified PAUT technicians and data analysts
- Scan plans and techniques developed or reviewed by our Level III personnel
- Encoded scanning and data files delivered with the report when the scope calls for them
- Conventional UT available alongside PAUT on the same job
Let's discuss your inspection requirements.
Tell us about your project, schedule, and the specifications you work to. A member of our leadership team will respond directly.