ASME Section V Article 4 — Ultrasonic Examination of Welds

Ultrasonic examination (UT) of welds under ASME BPVC — covers basic calibration block, DAC, scanning, IIW V1/V2 reference, and acceptance flagged at 50% DAC.

Scope

Article 4 of ASME Section V governs ultrasonic examination (UT) of welds in ferritic materials, primarily for pressure-retaining welds in Section VIII Div 1, Section I, and B31 piping. The article covers conventional pulse-echo UT with single-element transducers in shear-wave and longitudinal-wave modes. Phased-array UT (PAUT) and time-of-flight diffraction (TOFD) are addressed by Article 4 with the Mandatory Appendix V (PAUT) and Mandatory Appendix N (TOFD) — both adopted in recent editions and increasingly used as alternatives to RT. Article 4 requires a basic calibration block of the same material specification, product form, heat treatment, and approximate thickness as the production weld. It establishes the distance-amplitude correction (DAC) curve from the side-drilled hole (SDH) of the basic calibration block, scanning techniques (raster, line, zone), and acceptance criteria keyed to percentage of DAC (typically 50% DAC threshold for recording).

NDT methods it governs

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{"label":"Phased Array UT (PAUT)","href":"/blog/phased-array-ultrasonic-testing-paut-guide"}
{"label":"Time-of-Flight Diffraction (TOFD)","href":"/blog/tofd-inspection-time-of-flight-diffraction-explained"}
{"label":"ASME Section V Overview","href":"/blog/asme-section-v-ndt-requirements-guide"}

Certifications that reference it

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{"label":"API 510 Certification","href":"/api-510-certification"}
{"label":"API 570 Certification","href":"/api-570-certification"}

Issuing body

ASME

Revision history

2025 —
2023 —
2021 —
2019 —

Related standards

asme-section-v-article-1 · asme-section-v-article-2 · asme-section-v-article-5 · iso-17640 · asme-b31-3 · aws-d1-1

Applying this in an inspection programme

Code compliance is only demonstrable if the evidence behind it is: the procedure revision in force, the inspector's certification state and the instrument's calibration status at the time of test. Atlantis NDT provides ASNT Level III consulting for procedure and written-practice work against this code, training toward the certifications that reference it, and inspection management software that keeps that evidence recoverable years later. Request a consultation.

How a standard like this is applied in an inspection programme

A standard is only half of the requirement. It defines how an examination is performed and, in some cases, how results are classified — but the acceptance criteria that decide whether a component stays in service normally come from the construction or in-service code governing the item, not from the examination standard itself. Confusing the two is one of the more common findings in a procedure review: a procedure that correctly cites the examination standard but applies acceptance criteria from the wrong code or the wrong edition.

What has to be in place for compliance to be demonstrable

A written procedure qualified against this standard for the specific materials, thickness ranges and geometries in scope — not a generic procedure covering everything
Personnel certified for the method and level under ASNT SNT-TC-1A, ANSI/ASNT CP-189, NAS 410 or ISO 9712, current on the date the examination was performed
Equipment, probes and reference standards in calibration on that date, with traceability to a national standard under ISO 17025
The applicable edition of the standard recorded against the examination, so historical work stays assessed under the edition then in force
Technique sheets under the same revision control as the procedure above them — the most frequently uncontrolled document in an otherwise compliant quality system

Edition changes

When a new edition is issued, new work moves to it from a defined effective date that you set and record; work already performed stays assessed under the edition in force at the time. Retrospectively applying a new edition to historical dispositions invalidates the original acceptance decision and creates a substantially larger problem than the one being solved.

Where this usually goes wrong

Not in the technical content, but in reconstruction. An auditor picks an issued report and asks which procedure revision applied, who performed the work and whether they were qualified on that date, and whether the instrument and reference blocks were in calibration. Programmes that hold only current state can answer none of those. Binding the document revision, the qualification state and the calibration state to each inspection record as it is created turns that from an investigation into a lookup.