Automated Ultrasonic Testing (AUT)

AUT is the use of mechanized scanners with encoded position to perform ultrasonic inspection (typically PAUT and/or TOFD) with consistent coverage, full data capture, and repeatable scan plans, widely used for pipeline girth welds.

Definition

Automated Ultrasonic Testing (AUT) employs mechanized scanners — usually band-driven for pipeline girth welds — that carry one or more PAUT and TOFD probes around the weld at a controlled speed. Position is recorded by an encoder, and full waveform data are captured for every position.

Technical Context

AUT replaces radiography on many pipeline construction projects, achieving higher inspection speed and zero radiation exposure. Acceptance is generally per API 1163 and ISO 13588 for the system, with weld acceptance per the construction code.

When It Is Used

  • Pipeline girth-weld inspection in lay barges and onshore spreads
  • Heavy-wall vessel and nozzle weld inspection
  • In-service crack monitoring

How it works

Ultrasonic examination performed with mechanised probe motion and encoded position, so every A-scan is stored against the coordinate where it was captured rather than being watched live and discarded.

What it finds

The same flaws as manual ultrasonics, but with coverage that can be demonstrated afterwards and data that can be re-analysed without returning to site. Girth weld inspection and corrosion mapping are its established uses.

What it will not find

Nothing that manual UT would catch by physics — the limits of orientation, attenuation and near-surface resolution are unchanged. What changes is repeatability and evidence, not detection capability.

How it is actually done

Scanner tracking, encoder calibration and consistent couplant delivery are the practical constraints. Zone discrimination setups for girth welds are built around the weld bevel geometry, so a change in bevel invalidates the setup.

Governing codes and standards

ASME Section V Article 4 with the relevant appendices; ISO 13588 for phased array; API 1104 Annex on ultrasonic examination for pipeline girth welds where mechanised UT substitutes for radiography.

Where it goes wrong

Assuming an encoded scan proves coverage. It proves where the probe went — coverage of the volume of interest additionally requires the beam angles and focal laws to have interrogated that volume, which is a setup question, not a scanning one.

Where Automated Ultrasonic Testing fits in an inspection programme

A term is only useful when it connects to a decision. Automated Ultrasonic Testing appears in written procedures, in technique sheets, and in the records an owner or accreditation body reviews afterwards — which means the way it is defined in your documentation has to match the way it is applied on site. Where the two drift apart, audits find it. Atlantis writes and reviews procedures against the governing codes, trains inspection personnel to apply them, and builds the record-keeping that makes the evidence retrievable years later. Procedure development and code consulting · NDT training and certification · Ask us about your programme.

Related terms

  • Phased Array Ultrasonic Testing (PAUT) — PAUT is an advanced ultrasonic technique using a multi-element transducer (16–256 elements) with electronic beam steering and focusing, producing sectorial, linear, and compound scans for superior weld inspection and defect characterization.
  • Time-of-Flight Diffraction (TOFD) — TOFD is an advanced UT technique using two angled probes in pitch-catch arrangement to detect and accurately size defects from the time of arrival of diffracted tip signals, achieving height-sizing accuracy of ±0.5 mm.
  • ISO 13588 Phased Array Ultrasonic Testing — ISO 13588 is the international standard for automated and semi-automated phased array ultrasonic testing of fusion welds, defining technique levels, scan plan, calibration, and characterization requirements for PAUT.

Further reading

automated ut aut systems complete overview · automated ultrasonic testing systems overview benefits

More method terms

Ultrasonic Testing · Radiographic Testing · Magnetic Particle Testing · Penetrant Testing · Eddy Current Testing · Visual Testing · Acoustic Emission Testing · Leak Testing · Thermography / Infrared Testing · Microwave Testing

Where this comes up in practice

Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.

Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.

AUT is not one configuration. Pipeline girth welds use zone-discriminated phased array plus TOFD on a band scanner; heavy-wall vessel welds use encoded raster PAUT; corrosion mapping uses an encoded zero-degree array. Each carries a different sizing basis and a different acceptance route, and ISO 13588 governs the automated phased array system rather than the weld acceptance.

On a US pipeline spread the decision to run AUT instead of radiography is commercial before it is technical: no radiation exclusion zone means welding continues alongside inspection, and the crew works through the night without clearing the right-of-way. What the owner buys with that is a qualification burden. Zone discrimination is built around the weld bevel, so the setup is qualified on a mock-up carrying deliberately placed flaws at the bevel geometry actually being welded, and a bevel change voids it. Sizing accuracy claimed for the system has to be demonstrated on that mock-up, because girth weld acceptance on most projects runs through an engineering critical assessment that consumes flaw height as an input. Data analysis is a separate competence from scanning, and specifications routinely require the analyst to hold a distinct qualification. The scan record is the deliverable, so archive the raw encoded data with its setup and calibration files.

Source: ISO 13588:2019 — Non-destructive testing of welds — Ultrasonic testing — Use of automated phased array technology; API 1104, Welding of Pipelines and Related Facilities; ASME BPVC Section V, Article 4 (2025 Edition)

Technically reviewed by Anoop Rayavarapu — ASNT NDT Level III (UT, RT, MT, PT, VT, ET) · API 653 · ISO 9001:2015 Lead Auditor
AUT configurations by application, sizing basis and acceptance route
ApplicationConfigurationSizing basisAcceptance routeRecord produced
Pipeline girth weldBand scanner carrying zone-discriminated PAUT plus TOFD, single circumferential passZone amplitude for detection, TOFD tip diffraction for through-wall heightAPI 1104 workmanship criteria or engineering critical assessment criteriaEncoded strip chart: zone gates, TOFD D-scan, coupling and position traces
Heavy-wall vessel and nozzle weldEncoded raster PAUT, sectorial scan from both sides where access allowsDAC or DGS amplitude, tip diffraction for through-wall extentASME Section VIII acceptance, examined to Section V Article 4Encoded volumetric C-scan and S-scan data set
Corrosion mappingEncoded zero-degree linear array on a two-axis or magnetic-wheel scannerMinimum remaining thickness per grid cellAPI 510 or API 570 evaluation against required minimum thicknessThickness C-scan with grid coordinates and a minimum-value map
Tube and pipe mill inspectionRotating or immersion AUT at fixed helical pitchReference notch amplitudeAPI 5L or the product specification, examined per ASTM E213Continuous alarm-channel trace logged against pipe identity
In-service crack and damage monitoringEncoded PAUT or TFM from a repeatable fixed datumTip diffraction through-wall height, compared scan to scanFitness-for-service assessment per API 579-1/ASME FFS-1Repeat-scan data set referenced to a permanent datum for growth comparison
Weld overlay and claddingEncoded PAUT in a low-frequency transmit-receive longitudinal configurationAmplitude against a clad reference block, with interface trackingASME Section V Article 4 with the construction code acceptanceEncoded C-scan of the bond line
The encoder records position only. Coverage of the weld volume is proved by the scan plan and the mock-up qualification, and a change of bevel, thickness or material sends the setup back through qualification before any data is acceptable.

Can AUT replace radiography on a US pipeline construction spread?

Yes, where the construction code and the owner permit ultrasonic examination as an alternative to radiography, which API 1104 does through its ultrasonic provisions and alternative acceptance criteria. The operational driver is the absence of a radiation exclusion zone: welding, coating and inspection run concurrently instead of clearing the right-of-way for every exposure, which is where the schedule saving comes from.

What has to be qualified before AUT data can be used for acceptance?

Three things independently. The procedure, demonstrated on a mock-up of the same material, thickness and bevel geometry with flaws at known positions. The system, including scanner, encoder, focal laws and analysis software, verified against that mock-up. And the personnel, both the operator running the scan and the analyst interpreting the data. Changing an essential variable sends the procedure back through qualification.

Does an encoded scan prove volumetric coverage?

It proves where the probe travelled, not what the beam interrogated. Coverage of the weld volume additionally requires the focal laws, wedge position and beam angles to have insonified every zone at an angle capable of detecting the expected flaw orientation. That is proved by the scan plan and the mock-up qualification; only the position axis comes from the encoder.

What happens to an AUT setup when the weld bevel changes?

A zone-discriminated setup maps each focal law to a specific height band of the bevel, so a change in bevel angle, root land or wall thickness moves the fusion faces out from under the zones. The setup is void and requires requalification on a mock-up of the new geometry. Field bevel changes made for fit-up reasons are the common cause of invalidated data.

Who is allowed to analyse AUT data?

Scanning and analysis are separate competences. Project specifications commonly require the analyst to hold Level II or III certification in the technique plus documented qualification on the specific system and the project mock-up. Data reviewed remotely by an analyst who never qualified on that mock-up is the finding auditors raise most often against AUT contractors.

What must an AUT record contain to be defensible years later?

The raw encoded data rather than a screenshot report; the setup and focal-law files used to acquire it; calibration and verification records naming the block; the scan plan and the procedure revision in force that day; and certification records for both operator and analyst. Without the setup files the data cannot be re-analysed, which removes the main reason for running AUT.