Phased Array Ultrasonic Testing (PAUT) with Encoded Scanning

Phased array ultrasonics uses a multi-element probe to steer, focus and sweep the beam electronically, producing imaged data across the volume of a weld and not a series of single readings. itmad provides PAUT inspection for welds, small bore tubing, turbine components and complex geometry, with encoded scanning, scan plans and qualification blocks, carried out by ISO 9712 qualified technicians. Encoded scanning records probe position with the signal, so the inspection is reproducible, reviewable after the fact and defensible when a result is challenged. itmad operates across the Middle East, Asia and Europe. Last reviewed: October 2026.

Scan planning

Coverage is not achieved by pointing a probe at a weld. A scan plan is developed first, establishing beam angles, focal laws, probe positions and index offsets that demonstrably cover the required volume for the geometry in question. Operators develop scan plans and produce technical justification summaries that account for the parameters chosen, and write the procedures and work instructions that make an inspection traceable and repeatable and not dependent on the operator.

Applications

On high pressure and high temperature piping, itmad achieves full weld volume coverage at 1 mm scanning intervals on circumferential and seam welds between 20 mm and 75 mm wall thickness, using encoded scanning at power station sites. Small bore tubing from 50 mm internal diameter down to 6 mm, where conventional probe access is not possible, is also inspected, and branch welds of complex geometry are scanned with encoded scanning of variable weld profiles for accurate sizing of internal defects where a fixed-angle technique cannot achieve coverage.

Turbine and generator components are examined with a focus on areas of high stress concentration, such as the fir tree serrations at turbine blade roots and geometry changes along exciter cooling fans. PAUT detects and monitors corrosion wastage along wind tower foundation bolts, reliably to five times the bolt diameter along the length, and maps corrosion and wall loss across tank shells and floors. It is used in situ to detect transverse cracking in shafts and axles in rotating and rail components for the public transport sector, on pipeline girth welds, pressure vessels, bifurcation lines and valve bodies with detailed analysis reporting, and on flat and shaped carbon fibre reinforced polymer (CFRP) components for delamination, porosity and disbonds.

Purpose-fabricated calibration and qualification blocks in the material and geometry being inspected, including aluminium, stainless steel, low carbon steel and Inconel, are used to demonstrate probability of detection.

Technical development

itmad's PAUT personnel have worked in research and development programmes that examined the technique for the detection of critical discontinuities in power industry components. They have published conference papers on compliance with standards and on the use of qualification blocks to improve probability of detection, and have investigated the effects of temperature, surface condition and couplant selection on PAUT signal response beyond the ranges that the standards prescribe. That work informs how techniques are selected and justified.

Standards applied

ISO 13588 covers ultrasonic testing of welds using automated phased array technology and ISO 19285 the PAUT acceptance levels for welds. ASME Boiler and Pressure Vessel Code Section V, Article 4, applies with acceptance to the relevant construction code section, alongside ASTM E2700 for contact ultrasonic testing of welds using phased arrays, API 1104 for pipeline girth welds and AWS D1.1 for structural steel welding. Client and project specifications and manufacturer requirements apply where they govern.

PAUT in place of radiography

PAUT is increasingly accepted where radiography was previously specified. It needs no radiation source, so there is no exclusion zone and no shutdown of surrounding work, it produces digital data immediately and not film that needs processing, and it measures through-wall flaw height, which radiography cannot. Substitution requires the governing code to permit it and the technique to be qualified, and itmad will advise where the code does not allow it.

Limitations

Coverage can be constrained by geometry, surface condition and access: a scan plan will show where full volumetric coverage is not achievable, and itmad reports that and does not imply coverage that was not obtained. Highly attenuative or coarse-grained materials reduce penetration, and surface preparation affects coupling and therefore sensitivity. PAUT complements the other NDT methods and does not replace all of them, and where a different technique answers the question better, itmad says so.

Personnel

PAUT is carried out by technicians qualified to ISO 9712 and ASNT SNT-TC-1A Level II with specific phased array qualification, under Level III oversight of procedure approval and technique validation. Encoded scanning suits shutdown and turnaround work, where the inspection window is fixed and results are needed for a return-to-service decision, at power stations, refineries, fabrication yards, pipelines and offshore installations.

What the client receives

The scan plan and the technical justification for the parameters applied, with encoded scan data retained and available for independent review. Indications are reported with location, length and through-wall height, supported by sectorial, C-scan and B-scan imagery, and are assessed against the acceptance criteria of the governing code. The client also receives calibration and qualification block records, the technician's qualification level and certification reference, and analysis that supports a repair or continued operation decision.

Frequently asked questions

What is PAUT and what does the full form stand for?

PAUT stands for phased array ultrasonic testing, an advanced ultrasonic method that uses a multi-element probe to steer, focus and sweep the beam electronically. It produces imaged sectorial, B-scan and C-scan data and not a series of single A-scan readings.

What is PAUT inspection used for in welding?

Full volumetric weld examination: detecting, locating and sizing internal defects such as lack of fusion, incomplete penetration, porosity and cracks. It is applied to piping, pressure vessel, pipeline girth and structural welds, and measures through-wall flaw height.

Can PAUT replace radiography?

It is increasingly accepted where radiography was previously specified, because it needs no radiation source, produces digital data immediately and measures through-wall flaw height. Substitution requires the governing code to permit it and the technique to be qualified.

Why is a scan plan needed?

Because coverage is not achieved by pointing a probe at a weld. The scan plan establishes beam angles, focal laws, probe positions and index offsets that demonstrably cover the required volume, and it makes the inspection traceable and repeatable.

Which standards apply?

ISO 13588, ISO 19285, ASME Section V Article 4, ASTM E2700, API 1104 for pipeline girth welds and AWS D1.1 for structural steel, with client and project specifications where they govern. Acceptance is to the relevant construction code section.

What qualifications do the PAUT technicians hold?

ISO 9712 and ASNT SNT-TC-1A Level II with specific phased array qualification, under Level III oversight. itmad's PAUT personnel have also worked in research and development programmes and published conference papers on probability of detection.