🔩 Detection, location, sizing and characterization of discontinuities in full-penetration butt-welded joints of thin-walled components of low-alloy or fine-grained steel (wall thickness 3,2–8,0 mm, e.g. boiler tubes) by semi- or fully automated ultrasonic phased array technology (E-scan, S-scan, raster, skewed scan), testing level C (standard situations) or D (special applications), assessment by height and length, amplitude and length or go/no-go, PN-EN ISO 20601

Materials and NDT PN-EN ISO 20601

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 20601:2019-03, in full (our translation of the Polish card text): “This document specifies the application of automated phased array technology for semi- or fully automated ultrasonic testing of welded joints in steel parts with a wall thickness from 3,2 mm to 8,0 mm. This is the typical range of tube wall thicknesses in boilers, which is an important application of this testing technology. The minimum and maximum values of the wall thickness range can be exceeded when testing level "D" of this document is applied. This document applies to full-penetration welded joints of simple geometry in plates, tubes, pipes and vessels, where both the weld and the parent material are low-alloy and/or fine-grained steel. Wherever material-dependent ultrasonic parameters are specified in this document, they are based on steels having a sound velocity of 5 920 (± 50) m / s for longitudinal waves and 3 255 (± 30) m/s for transverse waves. It is necessary to take this into account when testing materials with a different sound velocity. This document provides guidance on the specific capabilities and limitations of phased array technology for the detection, location, sizing and characterization of discontinuities in welded joints. Ultrasonic phased array technology can be used as a stand-alone technique or in combination with other non-destructive testing (NDT) methods or techniques, during manufacturing and testing of new welds / repair welds (in-service tests, inspections). This document specifies two testing levels: - level "C" for standard situations; - level "D" for other situations / special applications. This document describes the assessment of discontinuities for acceptance purposes based on: - height and length; - amplitude (equivalent reflector size) and length; - go / no-go decision. This document does not include acceptance levels for discontinuities”. Note: the English text at this point says “pre-service testing”, not in-service testing. We read the text of the standard in the preview of ISO 20601:2018 from the cover to clause 6.2.3 (probes — up to the frequency requirement, page 5); we do not have the rest of clause 6.2.3, clause 6.2.4 (scanning mechanisms), Clauses 7–15 (preparation, testing of parent material, range and sensitivity settings, reference and test blocks, equipment checks, verification of the procedure, weld testing, data storage, interpretation and assessment of indications, test report) or Annex A.

ACCORDING TO THE TEXT OF ISO 20601:2018 (foreword, Clauses 1–6.2.3). The standard was prepared by ISO/TC 44/SC 5 (testing and inspection of welds). Scope (Clause 1): application of phased array technology to semi- or fully automated ultrasonic testing of fusion-welded joints in steel parts 3,2–8,0 mm thick (typical boiler tube walls); at level D the thickness range may be exceeded; full-penetration joints of simple geometry in plates, tubes, pipes and vessels, weld and parent material of low-alloy or fine-grained steel; note: semi-automated testing — the probe is moved manually along a guide, and its position is unambiguously measured by a position sensor; fully automated — also mechanized propulsion; material-dependent parameters refer to steel with a longitudinal wave velocity of (5920 ± 50) m/s and transverse (3255 ± 30) m/s; stand-alone technique or in combination with other NDT methods during manufacturing and testing of new and repaired welds (pre-service testing); two testing levels: C — standard situations, D — other situations and special applications; assessment of discontinuities: height and length, amplitude (equivalent reflector size) and length, go/no-go decision; no acceptance levels. Normative references: ISO 5577 (UT vocabulary), ISO 9712 (personnel qualification), ISO 17640 (techniques, testing levels and assessment for UT of welds), ISO 18563-1, -2, -3 (characterization and verification of phased array equipment: instruments, probes, combined systems), EN 16018 (phased array terminology). Definitions (Clause 3): phased array image — one- or two-dimensional display from the collected data; indication — pattern or disturbance in the image which may need further evaluation; phased array set-up — probe arrangement defined by probe characteristics (frequency, element size, beam angle, wave mode), position, number and adaptation to curvature; scan increment — distance between successive data collection points in the scanning direction; skewed scan — with the beam skewed electronically or by rotating the probe. Testing levels (Clause 4): a written procedure is mandatory at both levels; level C — standardized approach for thin-walled components (Tables 1 and 2), e.g. testing from both sides of the weld or from one side with the cap removed; level D — agreed for special applications (wall below 3,2 mm, varying thickness, object temperature outside the range in 7.6), verification on test blocks mandatory; Table 1: level C recommended for quality levels B, C, D according to ISO 5817 (when ISO 17635 is specified), level D — special applications; the set-up is verified on reference and/or test blocks; when scanning from one surface at least half and full skip, from both surfaces half skip may suffice; with assessment based on amplitude only, the deviation of the beam axis from the normal to the weld bevel shall not exceed 6°, and if the geometry does not allow this, the scan plan describes corrective measures; Table 2 (level C): E-scan at fixed probe position — from two sides, S-scan at fixed position — from two sides or from two positions on the same side, S-scan raster — from one side with the cap removed, skewed scan — not applicable (at level D everything to be specified); when detection of transverse discontinuities is required — an additional set-up. Information before testing (Clause 5): among others purpose and extent, type of parent material and grain size, testing level, acceptance criteria, reference blocks, manufacturing or operational stage, weld details and heat-affected zone, access, surface condition and temperature, qualifications, reporting; additionally for the operator — joint preparation and dimensions, welding process, time of testing relative to post-weld heat treatment; the written procedure includes among others techniques, equipment (frequency, sampling rate, element pitch and size), reference blocks, sensitivity and range setting, testing of parent material, evaluation of indications, acceptance or recording levels and the scan plan (probe placement and movement, coverage, weld thickness and geometry, beam angles and directions, tested volume). Personnel (6.1): qualification according to ISO 9712 or equivalent; for characterization of indications — documented training (welding process and weld shape, setting up the system with the weld contour, static and dynamic echo response according to ISO 23279, display settings without echo envelope, hitting the bevel perpendicularly or within ± 6°). Equipment (6.2): ISO/TS 16829 helps in selecting the system; equipment according to ISO 18563-1, -2 and -3; recommended A-scan sampling rate at least six times the nominal probe frequency; probes for longitudinal, transverse and creeping waves, frequency at least 5 MHz, suitable for the thickness — this is where the part we read ends.

STATUS (cards as of 02.10.2026). The card of PN-EN ISO 20601:2019-03 in the English version (published 05-03-2019, 32 pages, price group P) does not carry the heading “Wycofana” (withdrawn): Metallurgy Sector, KT 165 Welding and Allied Processes, ICS 25.160.40, “Introduces: EN ISO 20601:2018 [IDT], ISO 20601:2018 [IDT]”. The PKN search for “PN-EN ISO 20601” (02.10.2026) shows only this edition.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read on 02.10.2026). The number 20601 appears in 8 records at 8 laboratories, but at two (AB 597, AB 774) it is a fragment of a European Pharmacopoeia reference (“2.6.1;04/2011:20601”, sterility), not this standard; PN-EN ISO 20601 appears in 6 records at 6 laboratories: AB 608, AB 1336, AB 1646, AB 1881, AB 1898, AB 1938. In the current scopes on the PCA website (read on 02.10.2026, issues from 23.04.2025 to 15.07.2026) four laboratories cite “PN-EN ISO 20601:2019-03”, and AB 608 and AB 1881 — the number without a year. No row is set in bold italics. The “Laboratories” tab searches for entries STARTING WITH “PN-EN ISO 20601” and shows all 6 laboratories and 6 items — checked with the tab query on the labcoda.pl production server on 02.10.2026.

WHAT THE LABORATORIES TEST (items in the PCA scopes). Welded joints of metallic materials — “discontinuities, range (3,2–8,0) mm, ultrasonic method, Phased Array technique” (AB 1336, AB 1881, AB 1938), “discontinuities of welded joints with thickness from 3,2 mm to 8 mm, ultrasonic method using the Phased Array technique” (AB 1898), “internal discontinuities, ultrasonic method” (AB 1646), joints 3,2–8,0 mm thick (AB 608). At all of them alongside PN-EN ISO 13588 (phased array for thicknesses from 6 mm) and PN-EN ISO 17640, at five also PN-EN ISO 10863 (TOFD).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Thickness: the standard covers walls of 3,2–8,0 mm — outside this range only level D with verification on test blocks; for thicker joints PN-EN ISO 13588 is appropriate. Material: the parameters refer to steel with a longitudinal wave velocity of 5920 m/s and transverse 3255 m/s — a different velocity (e.g. austenitic steel) must be taken into account. Amplitude assessment: the beam must hit the weld bevel perpendicularly or within ± 6° — otherwise the amplitude underestimates the discontinuity; the scan plan must then describe corrective measures. Coverage: when scanning from one surface, half and full skip are needed; transverse discontinuities require an additional set-up (skewed scan). Equipment: probe at least 5 MHz, A-scan sampling at least six times, equipment verified according to ISO 18563; a position encoder is a condition of semi-automated testing. Result: the standard contains no acceptance levels — they must be set before testing (e.g. via ISO 17635 and ISO 5817).

WHAT WE DO NOT GIVE. We do not have the rest of clause 6.2.3, clause 6.2.4 or Clauses 7–15 (scan increment, surface preparation, temperature, couplant, sensitivity setting, reference blocks and reflectors, test blocks for level D, equipment checks, data storage, determination of location, length and height of indications, test report) or Annex A — so we do not give reference block dimensions, sensitivity settings or rules for sizing indications.

Method principle

The weld of a thin-walled steel component is scanned with ultrasonic beams steered electronically by a multi-element phased array probe (E-scan, S-scan, raster, skewed scan), moved along the weld manually on a guide or mechanically with a position encoder; from the stored images discontinuities are detected, located and sized, and assessed by height and length, amplitude and length or a go/no-go decision.

Applications

• Welded joints of boiler tubes and other thin-walled steel components (3,2–8,0 mm) — internal discontinuities, 6 laboratories
• Plates, tubes and vessels of low-alloy and fine-grained steel — new and repaired welds before service
• Stand-alone testing or in combination with other non-destructive testing methods

Key parameters

Standard

Standard number

PN-EN ISO 20601:2019-03 (wersja angielska; EN ISO 20601:2018 IDT, ISO 20601:2018 IDT)

Title (PL)

Badania nieniszczące spoin — Badania ultradźwiękowe — Stosowanie zautomatyzowanej techniki głowicy mozaikowej dla cienkościennych elementów stalowych

Title (EN)

Non-destructive testing of welds — Ultrasonic testing — Use of automated phased array technology for thin-walled steel components

Step-by-step procedure

1. Information and procedure

   Purpose and extent, material, testing level (C or D), acceptance criteria, weld details; written procedure with scan plan. PN-EN ISO 20601:2019-03 current (cards as of 02.10.2026).

2. Personnel and equipment

   Qualification according to ISO 9712 (for characterization — additional training); equipment according to ISO 18563, probes ≥ 5 MHz.

3. Set-up and verification

   Probe set-up, range and sensitivity on reference blocks, at level D — verification on test blocks (Clauses 7, 9–11, details NOT GIVEN).

4. Scanning

   Set-ups according to Table 2 (e.g. E- or S-scan from two sides), half and full skip with access from one surface, beam within ± 6° of the normal to the bevel for amplitude assessment; data storage.

5. Assessment and report

   Identification, classification, location, length and height of indications; assessment according to the set criteria (Clause 14 — NOT GIVEN); test report (Clause 15).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Testing without particular hazards; on site — work at height and in boilers according to plant rules; the procedure must cover environmental and safety issues (5.3 n)
• SUBSTANTIVE NOTE: the standard contains no acceptance levels; the 3,2–8,0 mm range applies to level C — outside it only level D with test blocks; in the database copy the string “20601” also hits European Pharmacopoeia references

Frequently asked questions