Phased Array Ultrasonic Testing (PAUT) in Belgium
Phased Array Ultrasonic Testing (PAUT) is an advanced ultrasonic inspection technique that uses multi-element probes to electronically steer and focus ultrasonic beams. It delivers superior detection capability and detailed cross-sectional imaging of the inspected volume, making it ideal for critical weld and component inspections.
What is Phased Array Ultrasonic Testing?
Phased Array Ultrasonic Testing (PAUT) is an advanced evolution of conventional ultrasonic testing that employs probes containing multiple piezoelectric elements (typically 16 to 128 elements), each of which can be individually controlled in terms of timing and amplitude. By applying precisely calculated time delays (phase shifts) to groups of elements, the ultrasonic beam can be electronically steered, focused and swept across a range of angles without physically moving the probe. This enables the generation of sectorial scans (S-scans) and linear scans (L-scans) that produce real-time cross-sectional images of the component under examination.
The key advantage of PAUT over conventional ultrasonics lies in its ability to inspect a large volume of material from a single probe position, with optimised beam focusing at different depths and angles. This results in improved detection sensitivity, more accurate defect sizing and significantly faster inspection times. The electronic scanning capability also allows for better characterisation of defect morphology and orientation, providing inspectors with richer data for engineering critical assessments and fitness-for-service evaluations.
LCNDTEST deploys state-of-the-art phased array equipment for inspections across Belgium and Europe. Our technicians hold specific PAUT certifications and have extensive experience in developing scan plans and inspection procedures tailored to complex joint configurations, thick-walled components and critical applications in the petrochemical, energy and structural fabrication sectors.
Inspection Methodology
The PAUT inspection process begins with the development of a detailed scan plan, typically using simulation software that models the ultrasonic beam coverage based on the component geometry, material properties and probe characteristics. The scan plan defines the probe position, scanning direction, angular range of the sectorial scan, focal laws and calibration requirements. This preparatory step is critical to ensuring complete volumetric coverage of the zone of interest.
Calibration is performed on reference blocks that are representative of the component material and geometry, containing side-drilled holes (SDH) or notches at specified depths. The focal laws are programmed into the PAUT instrument, and sensitivity is set to ensure adequate detection capability across the full range of inspection angles and depths. A couplant is applied to the component surface, and the probe is scanned along the weld or area of interest, either manually or using a semi-automated scanner with an encoder for positional tracking.
During the scan, the PAUT instrument acquires and displays data in real time as colour-coded sectorial or linear images, enabling the operator to identify and evaluate indications immediately. The recorded data can also be reviewed offline for detailed analysis and reporting. Each indication is evaluated against the acceptance criteria of the applicable code or standard, and a comprehensive inspection report is produced that includes the scan plan, calibration records, encoded scan data and defect evaluation results.
Industrial Applications
- Inspection of thick-walled butt welds on pressure vessels, columns and reactors in the petrochemical industry
- Weld inspection on subsea and offshore pipelines, risers and structural nodes
- Corrosion mapping and erosion assessment on piping systems and storage tanks
- Inspection of dissimilar metal welds and austenitic stainless steel welds in power generation plants
- Examination of turbine components, rotor forgings and large-diameter shafts
- Replacement or complement to radiographic testing where ionising radiation is undesirable or impractical
Advantages of Phased Array Testing
- Superior volumetric coverage from a single probe position with electronic beam steering across multiple angles
- Real-time cross-sectional imaging (S-scan, L-scan) for enhanced defect detection and characterisation
- More accurate defect sizing compared to conventional ultrasonics, supporting fitness-for-service assessments
- Faster inspection times with encoded data acquisition, providing full traceability and auditability of results
- No ionising radiation hazard, enabling inspections during production without site evacuation
Reference Standards
EN ISO 13588 • EN ISO 19285 • ASME Section V Article 4 • ASME Code Case 2235 • DNVGL-ST-F101 • API 5UE
Frequently asked questions
Phased Array Ultrasonic Testing is an advanced evolution of conventional ultrasonic testing that uses multi-element probes (typically 16 to 128 piezoelectric elements) to electronically steer, focus and sweep ultrasonic beams across a range of angles. By applying precisely calculated time delays to groups of elements, PAUT generates real-time cross-sectional images (sectorial and linear scans) of the component being inspected, providing significantly enhanced detection capability and defect characterisation compared to conventional single-element ultrasonics.
Phased Array offers several key advantages: it can inspect a large volume from a single probe position through electronic beam steering, eliminating the need for multiple probe angles; it produces detailed cross-sectional images that aid in defect identification and sizing; it provides faster inspection times with encoded data acquisition for full traceability; and it enables more accurate defect sizing for fitness-for-service assessments. PAUT is also increasingly accepted as an alternative to radiographic testing, avoiding the constraints of ionising radiation.
PAUT is widely used for the inspection of thick-walled butt welds on pressure vessels and piping in the petrochemical and energy sectors, dissimilar metal welds and austenitic stainless steel welds, offshore pipeline girth welds, corrosion mapping on piping systems and storage tanks, and examination of turbine components and large forgings. It is particularly valuable in critical applications where precise defect sizing is required for engineering assessments and where radiographic testing is impractical or undesirable.