🔩 Radiographic testing of welded joints in metals with digital detectors — computed radiography (CR) and digital detector arrays (DDA), technique classes A and B, compensation principles, PN-EN ISO 17636-2

Materials and NDT PN-EN ISO 17636-2

Overview

WHAT THE STANDARD COVERS. We have a preview of ISO 17636-2:2022 (second edition) — from the foreword to clause 6.5; the text is introduced unchanged (IDT) by PN-EN ISO 17636-2:2023-04. Scope (Clause 1): digital radiographic techniques to achieve satisfactory and repeatable results, for fusion-welded joints in metallic materials — joints of plates and pipes ("pipe" also covers pipelines, boiler drums and pressure vessels); requirements for X- and gamma-ray radiography with computed radiography (CR) or digital detector arrays (DDA), with manual and automated DDA testing; the procedure gives the minimum requirements under which digital radiographs have a sensitivity for detecting imperfections equivalent to film radiography (ISO 17636-1). The standard does not specify acceptance levels for indications — these are in ISO 10675; if the parties agree lower criteria, the quality may be significantly lower. The foreword lists the changes from the 2013 edition, including: manual and automated DDA testing (6.6, 6.7, 7.8), permitting a wire visibility shorter than 10 mm for pipes with an outside diameter below 50 mm, ASTM wire IQIs and others by agreement of the parties, a new clause 6.8 on image quality assessment, deletion of the lower thickness limit for Se-75, clarification of IQI use for the DWDI technique, permission to accept a lower SNR_N (7.3.1) when the tube voltage is below 80 % of the values in Figure 20 (recommended tube voltages) or when energy-resolving detectors are used, extension of compensation principle CP II to three wire pairs, new annexes F and G.

TERMS AND TECHNIQUE CLASSES (clauses 3–6 of the preview). Computed radiography — an imaging plate with a storage phosphor (IP) and a reader converting the latent image into a digital one; DDA — a detector converting radiation into discrete signals that are digitized and transferred to a computer; structural noise, grey value and linearized grey value; basic spatial resolution of the detector (SRb detector) and of the image (SRb image) — half of the unsharpness measured with the duplex wire IQI (ISO 19232-5); SNR and normalized SNR_N = SNR × 88.6 / SRb image; CNR and normalized CNR_N; weld area of evaluation (WAE — the weld with the heat-affected zones) and area of interest (AoI — also letters, markers and image quality indicators); heat-affected zone — on both sides of the weld, the width of the weld cap, at least 10 mm. Two technique classes: A — basic, B — improved, used when A is not sensitive enough; the choice of technique is agreed by the parties; the visibility of imperfections with classes A and B is equivalent to film radiography and must be demonstrated with image quality indicators according to ISO 19232-1 or ISO 19232-2 and ISO 19232-5. When the class B condition cannot be met (e.g. type of source, source-to-object distance), the parties may accept the class A condition, and the loss of sensitivity is compensated by a higher grey value and SNR_N (an increase of SNR_N by more than 1.4 times is recommended). Three compensation principles: CP I — reduced contrast (e.g. higher voltage) is compensated by a higher SNR (e.g. higher tube current or exposure time); CP II — insufficient detector sharpness (SRb larger than required) — by a higher SNR, one more wire or hole for each missing wire pair; CP III — unsharpness from DDA bad pixel correction — by a higher SNR. Preparation: protection against ionizing radiation; the surface is usually not prepared unless irregularities or coatings hinder the detection of imperfections; testing after the last manufacturing stage (e.g. grinding, heat treatment); when the weld is not visible in the image, high-density markers are placed on both sides outside the WAE; each section is identified by symbols visible on the radiograph.

STATUS (state of the cards on 29 September 2026). The card of PN-EN ISO 17636-2:2023-04 (English version) has no "Wycofana" (withdrawn) header — the edition is CURRENT: published 06-04-2023, 78 pages, price group W, Metallurgy Sector, PKN technical committee KT 165 (Welding and Allied Processes), ICS 25.160.40, "Introduces: EN ISO 17636-2:2022 [IDT], ISO 17636-2:2022 [IDT]", "Supersedes: PN-EN ISO 17636-2:2013-06 - English version". Card of PN-EN ISO 17636-2:2013-06 (English version): "withdrawn and replaced by PN-EN ISO 17636-2:2023-04", published 25-06-2013, "Withdrawal date: 06-04-2023", 66 pages, "Introduces: EN ISO 17636-2:2013 [IDT], ISO 17636-2:2013 [IDT]". The PKN search for "PN-EN ISO 17636-2" (29 September 2026) shows only these two editions; no laboratory in the copy cites the 2013 edition.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17 September 2026, read on 28 September 2026). All records of number 17636-2: 12 entries at 12 laboratories, all in the form "PN-EN ISO 17636-2:2023-04". The "Laboratories" tab searches for records BEGINNING with "PN-EN ISO 17636-2" and will show 11 laboratories — checked with the tab query on the labcoda.pl production server on 29 September 2026: 11; AB 1646 remains outside it (it records "PN-EN ISO 17636-1:2023-02 PN-EN ISO 17636-2:2023-04 ASME s. V art. 2 ed. 2023" in one string). Current scopes on the PCA website (read on 29 September 2026, issues from 20 December 2024 to 25 August 2026): all entries stand in the valid issues and none is suspended.

TEST ITEM AND RANGES. Welded joints in metallic materials — 10 laboratories; AB 001 more widely: discontinuities in metallurgical products, castings and welded joints of metals up to 30 mm and of plastics, with X-rays (marked as tests on the basis of which the laboratory gives opinions and interpretations); AB 1754 — metallic products and materials up to 100 mm. Thicknesses: up to 30 mm (AB 001), up to 40 mm (AB 042, AB 1141 — "równoważnej dla stali" (steel equivalent), AB 1623 and AB 1921 — "Fe"), up to 60 mm (AB 1646), up to 100 mm (AB 1425 — "Fe", AB 1429, AB 1754) and up to 170 mm (AB 1307). Determined: discontinuities (including "spawalnicze wewnętrzne" — internal welding discontinuities); the technique is recorded as "metoda radiograficzna z użyciem detektorów cyfrowych" (radiographic method using digital detectors), "radiografii cyfrowej" (digital radiography) or simply "radiograficzna" (radiographic).

ALONGSIDE THIS STANDARD. Part 1 (film radiography, PN-EN ISO 17636-1:2023-02 — a separate Knowledge Base entry) is in the scopes of 10 of the 12 laboratories (all except AB 1921 and AB 1927): in the same entry — AB 1429, AB 1646 and AB 1754, in a separate row for the same joints — AB 042, AB 313, AB 1141, AB 1307, AB 1425 and AB 1623, and AB 001 — in a separate entry, for joints up to 30 mm Fe. The same entry as this standard also contains: PN-EN ISO 5579:2014-02 (general principles of radiographic testing of metals, a separate entry) — AB 1429 and AB 1754, ASME Section V Article 2 — AB 1646, PN-EN 12681-2:2017-12 (digital radiography of castings) — AB 001, AB 313 and AB 1927. Digital radiography of welded joints in steel tubes under PN-EN ISO 10893-7:2019-04 is held by AB 1623 in a separate row. All checked in the rows of the PCA documents.

WHAT WE DO NOT GIVE. The preview ends at clause 6.5, so we do not give the test arrangements (7.1), the choice of tube voltage (7.2, Figure 20) and isotope sources, the minimum source-to-object distance, the requirements for detectors and the minimum values of SNR_N, CNR_N and SRb (7.3 and tables), the position and choice of image quality indicators (6.7–6.9), image processing or the content of annexes A–G.

Method principle

The welded joint is irradiated with X- or gamma rays, and the image is recorded by a phosphor imaging plate read out in a scanner (CR) or by a digital detector array (DDA); the grey-scale image is evaluated on a monitor. Image quality is demonstrated with image quality indicators (wire or step/hole type and duplex wires) and with the normalized signal-to-noise ratio SNR_N and the basic spatial resolution SRb; class B gives a higher sensitivity than A, and shortfalls in some parameters can be compensated by a higher SNR (principles CP I–III). The standard does not set acceptance criteria (ISO 10675) (preview of ISO 17636-2:2022, clauses 1–6.5).

Applications

• Welded joints of metal plates and pipes, including pipelines, boiler drums and pressure vessels — detection of imperfections; in the scopes of 12 laboratories
• Thicknesses from 30 mm up to 170 mm (AB 1307); AB 001 also metallurgical products, castings and plastics

Key parameters

Standard

Standard number

PN-EN ISO 17636-2:2023-04 (wersja angielska; EN ISO 17636-2:2022, ISO 17636-2:2022 IDT)

Title (PL)

Badania nieniszczące spoin — Badanie radiograficzne — Część 2: Techniki promieniowania X i gamma z detektorami cyfrowymi

Title (EN)

Non-destructive testing of welds — Radiographic testing — Part 2: X- and gamma-ray techniques with digital detectors

Step-by-step procedure

1. Agreements

   The parties agree the digital radiography technique and the class (A or B); the standard does not give acceptance criteria (ISO 10675).

2. Preparation

   Radiation protection; testing after the last manufacturing stage; grinding or removal of coatings when they hinder the detection of imperfections; markers for the position of the weld and identification of sections.

3. Exposure

   X- or gamma rays, CR or DDA detector; test arrangements, voltages and distances NOT GIVEN — outside the preview.

4. Image quality

   Image quality indicators, SNR_N and SRb; shortfalls are compensated by a higher SNR (CP I–III); minimum values NOT GIVEN.

5. Evaluation

   Evaluation of the digital radiograph on a monitor in the WAE / AoI; acceptance criteria according to ISO 10675 (outside this standard).

Required equipment and apparatus

Health and safety (OHS)

• Ionizing X- and gamma radiation is very harmful — radiation protection regulations apply (the standard contains such a warning)
• SUBSTANTIVE NOTE: the standard specifies the testing technique, not the evaluation criteria — when asking for the test, also state the acceptance level (e.g. according to ISO 10675) and the technique class

Frequently asked questions