ASME Section V Article 2 — Radiographic Testing (RT) Requirements Explained

ASME Section V Article 2 — Practical Industry Guide

ASME Section V Article 2 is the foundational ASME nondestructive examination standard for radiographic testing of welds, castings, and forgings. It is referenced by ASME Section VIII (pressure vessel construction), ASME B31.1 (power piping), ASME B31.3 (process piping), API 510, API 570, API 653, AWS D1.1, NAVSEA T9074-AS-GIB-010, and dozens of international jurisdictional codes. Without Article 2 compliance, a radiograph cannot be used to support code acceptance of a welded joint, period.

Scope and Applicability of Article 2

Article 2 (T-210 through T-292) covers conventional radiography using X-ray sources up to 1 MeV and gamma radiation sources (Iridium-192, Cobalt-60, Selenium-75, Ytterbium-169). It addresses both single-wall single-image (SWSI) and double-wall double-image (DWDI) viewing techniques and applies to welds, castings, fabrications, and bonded composites. Computed radiography (CR) and digital detector array (DDA) techniques are addressed in companion Articles 22 and 27 — but Article 2 remains the baseline for film-based RT.

Equipment owners running multi-code inspection programs RBI program design should be aware that ultrasonic testing is the preferred alternative for many in-service inspections under API 510 § 5.6 and API 570 § 5.7 because of access, throughput, and ALARA radiation considerations — but Article 2 RT remains mandatory for original construction acceptance on most ASME-VIII Class 1 and B31.3 Category M services.

Image Quality Indicators (IQIs) — T-233

IQIs are the most-rejected element of any radiograph. Article 2 (T-233.1, T-233.2, T-276) allows two IQI types: hole-type per ASTM E1025 (the diamond-shaped plaque with three drilled holes 1T, 2T, 4T in diameter where T is the IQI thickness), or wire-type per ASTM E747 (a sequence of six wires of graduated diameter encased in low-attenuation plastic). The IQI is normally placed on the SOURCE side of the weld; placing it film-side requires marking with the letter F and using one designation thinner per T-277.

Selection of IQI designator is based on the radiographic-thickness range tables in T-276. For nominal 25 mm (1-inch) weld thickness with no reinforcement, the typical IQI is designator 25, with required hole 2T essential. The required sensitivity of 2-2T means the 2T hole on a thickness-25 IQI must be visible on the radiograph. Failure to demonstrate the essential hole or wire is an automatic technique rejection — re-shoot required.

Geometric Unsharpness (Ug) Limits — T-274.2

Geometric unsharpness Ug = F · t / d, where F = source size (mm), t = specimen-to-film distance (mm), d = source-to-specimen distance (mm). Article 2 sets the upper limit: 0.020 in. for material thickness ≤ 2 in., 0.030 in. for 2–3 in., 0.040 in. for 3–4 in., 0.070 in. for > 4 in. A 4 mm × 4 mm Ir-192 source at d = 600 mm, t = 50 mm yields Ug = 0.013 in. — within the 0.020 limit. Cobalt-60 sources (much larger physical dimension, 3–5 mm) require longer SFD to stay within Ug limits.

Source-to-film distance calculation is the most common technique-sheet error caught by qualified Level III reviewers. The Ug equation MUST be in the documented technique sheet, with the worst-case geometry called out. Atlantis NDT Reporting Software auto-calculates Ug from the technique inputs and flags non-compliant geometry before the shoot.

Density and Penetrameter Sensitivity — T-282 + T-283

Film density (D = log₁₀ (Io/I)) per T-282 must be 1.8–4.0 for X-ray and 2.0–4.0 for gamma sources, measured through the area of interest (weld) NOT the parent metal. Density variation across a single radiograph must not exceed −15 % / +30 % of the IQI density. A densitometer calibrated against an NIST-traceable step wedge is mandatory in the lab.

Sensitivity per T-283 is the IQI essential hole/wire that must be visible. Cracks, lack of fusion, lack of penetration, and slag inclusions in the weld are interpreted only after demonstrating that the radiograph meets the density and sensitivity requirements. Order matters — never call indications on a radiograph that fails the IQI check.

Single-Wall vs Double-Wall Techniques

Article 2 addresses three viewing geometries:

1. Single-Wall Single-Image (SWSI) — T-271.1: source outside, film inside (or vice versa); one weld interrogated per exposure. Preferred for pressure vessels and any pipe > 3.5 inch NPS where access permits.
2. Double-Wall Single-Image (DWSI) — T-271.2: source outside, film outside; only the far-side weld is interpreted (near-side weld is too unsharp). Used on small-bore piping where SWSI is impractical.
3. Double-Wall Double-Image (DWDI) — T-271.3: source offset 90° to weld plane; both near and far welds visible, offset elliptically on the film. Limited to NPS ≤ 3.5 in. Minimum two shots at 90° spacing required for full circumferential coverage.

Article 2 Cross-References — ASME Section VIII, B31.3, B31.1, AWS D1.1, API

Article 2 is referenced (not duplicated) by every downstream construction code. ASME Section VIII Div 1 § UW-51 requires "full RT" per Article 2 for Class 1 lethal-service and some thicknesses; Div 2 § 7.4.7 specifies fluorescent screen / lead-screen rules. ASME B31.3 § 344.5 calls out Article 2 for Category M (severe cyclic / hazardous) and Category K services. ASME B31.1 § 136.4 calls out 100 % RT for Class 1 components > 19 mm wall.

AWS D1.1 Clause 8 and Annex G map to Article 2 with adjusted acceptance criteria for structural welds (cumulative slag, porosity, undercut limits). API 510 § 8 + API 570 § 5.7 + API 653 § 12 reference Article 2 for spot-RT on alterations and repairs. API 510 Pressure Vessel Inspector, API 570 Piping Inspector, API 653 Tank Inspector all expect inspectors to read and interpret an Article 2 radiograph.

Technique Sheet, Procedure Qualification, and Records — T-291 + T-292

Every radiograph requires a written technique sheet (T-292.5) capturing: source type and strength, source-to-film distance, exposure time, film type, screens, IQI designator and location, geometric unsharpness calculation, density measurements, identification marks, weld identification, joint geometry sketch, and personnel qualifications.

The procedure must be qualified per ASME Section V Mandatory Appendix when a "Demonstration" approach is required by the referencing code. The Procedure Qualification Record (PQR) bundles a worst-case shot, the IQI achieved, the density measured, and the demonstrated coverage. Atlantis NDT Reporting Software ships a built-in Article 2 technique-sheet template with Ug auto-calculation, IQI-table lookup, and PDF auto-generation per shot.

Common Article 2 Audit Findings

• IQI essential hole/wire NOT visible — most common rejection
• Density < 1.8 or > 4.0 (over- or under-exposure)
• Ug calculation missing from technique sheet
• SFD inconsistency between technique sheet and field shot
• Source-side / film-side IQI marking missing the F stamp when film-side
• Multi-shot circumferential coverage gaps on DWDI (less than 2 shots at 90°)
• SNT-TC-1A guide Level II RT certification expired on the interpreting inspector
• Calibration block / step-wedge traceability not documented

Personnel Qualification — Article 2 + ASNT SNT-TC-1A / ISO 9712

Article 2 itself does not certify personnel — it references ASNT SNT-TC-1A, CP-189, ACCP, ISO 9712, or an employer-approved equivalent (e.g., NAS 410 for aerospace). For pressure-equipment work in the US, the dominant scheme is SNT-TC-1A Level II RT. For European / Middle Eastern projects, ISO 9712 Level 2 RT is more common.

Annual eye exam (near-vision Jaeger J1 + colour-perception Ishihara) is required by both ASNT SNT-TC-1A § 8.2 and ISO 9712 § 7.4 — and is the second most common audit finding when missing from the Level II cert pack. ASNT Level III consulting provides written-practice authoring, training-hour audit, and exam administration to keep your RT roster Article 2-compliant year-round.

Frequently Asked Questions

Q1: Can I use digital radiography (DR) under Article 2?

A: No — Article 2 is film-only. Computed Radiography is Article 22; Digital Detector Arrays are Article 27. If your specification calls out "Article 2", you must shoot film unless the referencing code or contract amends the technique. Many recent ASME VIII fab specs allow either Article 2 OR Article 22/27 by mutual agreement; check the contract carefully.

Q2: What sensitivity does Article 2 require?

A: Hole-type IQIs require the 2T hole to be visible (2-2T sensitivity); wire-type IQIs require a specific wire diameter visible per the table in T-276 (typically wire 8 or smaller depending on thickness). The required IQI designator is determined by the radiographic thickness, which is the weld thickness plus reinforcement.

Q3: Is Ir-192 still allowed for thin pipe under 0.5-inch wall?

A: Yes, but the Ug equation governs. A 3 mm × 3 mm Ir-192 source at SFD 600 mm gives Ug = 0.005 in. on a 0.5 in. weld — well within limits. The bigger concern on thin wall is contrast — Ir-192 spectrum (avg ≈ 380 keV) gives flatter contrast than X-ray, so density and IQI sensitivity become harder to achieve. Many fabricators prefer 160–200 kV X-ray for pipe < 0.5 in. wall.

Q4: How does Article 2 compare with ISO 17636-1?

A: ISO 17636-1 (RT of metallic materials, film-based) is the European / international equivalent. Both define IQI placement, Ug limits, and density ranges, but ISO 17636-1 uses single-wire EN ISO 19232 IQIs by default (Article 2 allows wire OR hole). For projects accepted under both ASME and EN, dual-IQI exposures are common. The acceptance criteria are NOT in Article 2 / ISO 17636 — they live in the construction code (ASME VIII, B31.3, ISO 5817).

Q5: Does Article 2 cover acceptance criteria for porosity, slag, and cracks?

A: No. Article 2 is the WORKMANSHIP standard for HOW to shoot the radiograph; the acceptance criteria for the indications come from the construction code being used. ASME VIII Div 1 § UW-51 (no crack-like flaws), ASME B31.3 § 341.3.2 (Table 341.3.2A), AWS D1.1 Table 8.1 (slag length per inch), and API 1104 § 9 each define their own pass/fail rules. Always pair Article 2 with the construction code's acceptance section.

Q6: How long must Article 2 radiographs be retained?

A: Article 2 itself does not specify retention. Most referencing codes require a minimum of 5 years (ASME VIII § UW-52), often longer for life-of-equipment retention (typical for nuclear, offshore platforms, and LNG service). Digital archive of scanned films with SHA-256 hash chain is now widely accepted — Atlantis NDT Reporting Software auto-generates the archive bundle.

Q7: Are crawler / crawler-fed isotope cameras allowed under Article 2?

A: Yes, provided source size, SFD, and Ug calculations meet T-274.2. Pipeline pigging-crawler isotope shots are extremely common for cross-country pipeline construction (B31.4, B31.8) — and they are still Article 2 RT in spirit. The technique sheet must call out the crawler geometry, source size, and Ug calc for the worst weld position.

Q8: How does Article 2 interact with API 1104 for pipeline welds?

A: API 1104 § 11.1 references "an approved radiographic procedure". For US pipelines, that's almost always Article 2. The acceptance criteria are in API 1104 § 9 (image quality, indication length limits, cluster rules), NOT Article 2 — so Article 2 governs HOW you shoot, API 1104 governs PASS/FAIL on the pipeline weld.

Related Atlantis NDT Resources

• ASNT certification — Level I/II/III pathway, pass rates, employer recognition
• API 510 Pressure Vessel Inspector · API 570 Piping Inspector · API 653 Tank Inspector
• ASNT Level III consulting — outsourced Level III of record with SLA
• NDT reporting software — IACS-accepted Marine NDT report format auto-bundled
• Atlantis NDT ERP — affordable, accessible, fully customizable; 30+ Odoo apps included
• Atlantis Digital Twin platform — 3D inspection-data overlay, API 579 FFS, predictive maintenance
• radiographic testing
• API 579 FFS

Atlantis NDT is led by Anoop Rayavarapu (ASNT NDT Level III, API 653 Authorized Inspector, ISO 9001 Lead Auditor). Free consultation for NDT inspection companies, training providers, and asset owners worldwide. request a demo — pricing varies by region and scope, quote on request.