PAUT Weld Inspection Services
Phased Array Ultrasonic Testing (PAUT) is an advanced nondestructive testing technique used to inspect welds in pipes, pipelines, pressure vessels, tanks and other critical industrial components.
The technology uses a multi-element ultrasonic probe to electronically steer and focus the sound beam through the weld. This enables multiple inspection angles to be generated from a single probe position, providing detailed coverage of the weld volume and heat-affected zone.
PAUT is widely used during fabrication, installation, commissioning, plant shutdowns and in-service inspection programmes.
PAUT Inspection of Pipe Welds
Pipe welds can contain discontinuities caused by improper fit-up, welding parameters, consumable condition, joint preparation or operational stresses.
PAUT can be applied to:
➤ Pipeline girth welds
➤ Process-piping circumferential welds
➤ Longitudinal seam welds
➤ Small-bore piping welds
➤ Heavy-wall pipe welds
➤ Dissimilar-metal welds
➤ Branch and nozzle connections
➤ Repair welds
➤ Cladding and overlay welds
➤ In-service piping systems
The inspection technique must be designed according to the pipe outside diameter, wall thickness, weld preparation, material and expected defect orientation.
PAUT Inspection of Pressure-Vessel Welds
Pressure vessels contain several types of welds that may require volumetric examination during fabrication or periodic inspection.
Typical PAUT applications include:
➤ Longitudinal shell welds
➤ Circumferential shell welds
➤ Head-to-shell welds
➤ Nozzle-to-shell welds
➤ Manway welds
➤ Support attachment areas
➤ Repair welds
➤ Weld overlay and cladding
➤ Suspected in-service cracking areas
For complex connections such as nozzles and branch welds, additional probes, wedges or scanning positions may be required to achieve adequate coverage.
Weld Defects Detectable by PAUT
Subject to the material, geometry and approved technique, PAUT can detect:
➤ Lack of sidewall fusion
➤ Lack of root fusion
➤ Incomplete penetration
➤ Cracks
➤ Slag inclusions
➤ Porosity
➤ Root concavity
➤ Undercut
➤ Lamination
➤ Weld-profile indications
➤ Service-induced cracking
➤ Corrosion near the weld area
Planar discontinuities such as cracks and lack of fusion can be detected effectively when the ultrasonic beam is directed toward the expected defect orientation.
How PAUT Weld Inspection Is Performed
1.Technical Review
Before inspection, the technical team reviews:
➤ Component drawings
➤ Pipe diameter and thickness
➤ Material grade
➤ Weld joint configuration
➤ Surface condition
➤ Scanning access
➤ Applicable inspection code
➤ Acceptance criteria
➤ Expected defect locations
2. Scan-Plan Preparation
A scan plan is prepared to demonstrate how the ultrasonic beams will cover the weld volume, root, fusion faces and heat-affected zone.
The scan plan helps determine:
➤ Probe position
➤ Selected refracted angles
➤ Beam coverage
➤ Focal depth
➤ Index offset
➤ Scan direction
➤ Required number of scan positions
3. Equipment and Probe Selection
The equipment configuration may include:
➤ PAUT instrument
➤ Linear-array probe
➤ Suitable flat or contoured wedge
➤ Manual or encoded scanner
➤ Position encoder
➤ Calibration block
➤ Couplant
➤ Data-analysis software
Probe frequency, aperture, element configuration and wedge angle must suit the component material and geometry.
4. Calibration
System calibration may include:
➤ Wedge-delay calibration
➤ Velocity calibration
➤ Sensitivity calibration
➤ Time-corrected gain
➤ Encoder calibration
➤ Reference sensitivity verification
➤ Exit-point and angle verification
Calibration is performed using an appropriate reference block or project-specific calibration block.
5. Data Acquisition
The probe is moved along the weld manually or through an encoded scanner. The position encoder records the location of the probe while the PAUT instrument collects ultrasonic data.
Encoded scanning improves traceability because the recorded indications can be linked to their precise locations along the weld.
6. Data Analysis and Reporting
Qualified personnel analyse the recorded data to determine:
➤ Indication position
➤ Indication length
➤ Through-wall location
➤ Signal response
➤ Indication characteristics
➤ Evaluation against acceptance criteria
The final decision is made according to the applicable code, approved procedure and project specification.
Manual and Encoded PAUT Inspection
Manual PAUT
Manual PAUT may be suitable for:
➤ Limited inspection quantities
➤ Restricted-access areas
➤ Spot examinations
➤ Maintenance inspections
➤ Complex component geometries
➤ Preliminary feasibility assessments
Encoded PAUT
Encoded PAUT is generally preferred for:
➤ Pipeline girth welds
➤ Large inspection quantities
➤ Critical pressure components
➤ Mechanized weld inspection
➤ Permanent digital data requirements
➤ Repeat examinations and comparison
➤ Client or third-party review
Encoded data offers better positional traceability and allows the complete inspection file to be reviewed after completing the fieldwork.
Benefits of PAUT for Weld Inspection
Improved Weld Coverage
A range of ultrasonic angles can inspect different areas of the weld from a single probe position.
Detailed Defect Location
PAUT can help determine the location of an indication relative to the weld centreline, surface and component thickness.
Digital Data Recording
Inspection data can be stored for technical review, third-party verification and future comparison.
Faster Inspection
Electronic beam steering and encoded scanners can improve inspection speed, particularly for repetitive weld configurations.
No Radiation Hazard
PAUT does not use ionising radiation. Nearby activities can often continue without the exclusion zones commonly required for radiography.
Suitable for Thickness Sizing
When supported by an approved sizing technique, PAUT can assist in determining the through-wall dimensions of discontinuities.
PAUT and TOFD Combined Inspection
PAUT and Time of Flight Diffraction (TOFD) may be used together for critical weld inspection.
PAUT provides directional examination and detailed imaging of the weld volume, while TOFD can offer reliable through-wall sizing for suitable weld configurations. Combining both methods can improve overall inspection confidence.
However, the combined technique must be supported by:
➤ Adequate surface access
➤ Suitable component thickness
➤ Validated scanning arrangements
➤ Approved procedures
➤ Representative calibration blocks
➤ Qualified inspection personnel
PAUT Inspection Standards
Depending on the project, weld inspection may be conducted with reference to:
➤ ASME Boiler and Pressure Vessel Code, Section V
➤ ISO 13588
➤ ISO 20601
➤ ISO 4761
➤ ISO 22825
➤ API 1104
➤ Applicable construction codes
➤ Client specifications
➤ Approved project procedures
ISO 13588 covers the application of phased array technology for semi- or fully automated examination of fusion-welded joints. The applicable standard edition and acceptance criteria must be confirmed for each project. ISO 13588 information
Factors Affecting PAUT Inspection Reliability
Successful PAUT inspection depends on:
➤ Accurate weld dimensions
➤ Correct material identification
➤ Suitable probe and wedge selection
➤ Proper beam coverage
➤ Representative calibration reflectors
➤ Good surface condition
➤ Stable ultrasonic coupling
➤ Correct sensitivity settings
➤ Defect orientation
➤ Qualified data interpretation
Complex geometry, coarse-grained materials, restricted access and unfavourable defect orientation can reduce inspection effectiveness. A feasibility study or technical demonstration may therefore be required.
Information Required for a PAUT Proposal
Clients should provide:
➤ Pipe or vessel drawing
➤ Material specification
➤ Outside diameter
➤ Wall thickness
➤ Weld configuration
➤ Number and length of welds
➤ Applicable code
➤ Acceptance criteria
➤ Inspection location
➤ Surface accessibility
➤ Expected project duration
➤ Required reporting format
➤ Inspection schedule
Our PAUT Weld Inspection Capabilities
Integrity & Advanced Inspection Solutions India Private Limited provides PAUT inspection services for fabrication facilities, refineries, petrochemical plants, pipelines, power plants, offshore structures, marine assets and industrial shutdowns.
Our support can include:
➤ PAUT Level II personnel
➤ PAUT and TOFD inspection teams
➤ Advanced PAUT equipment
➤ Manual and encoded scanners
➤ Small-bore and large-diameter pipe inspection
➤ Customized probes and wedges
➤ Calibration-block preparation
➤ Procedure and scan-plan development
➤ On-site data analysis
➤ Weld-wise inspection reporting
➤ Domestic and international mobilization
Request a Technical and Commercial Proposal
Contact our technical team with your weld details, drawings, inspection quantities, applicable code and project location.