Radiographic Testing Procedure for Pipeline Girth Welds (API 1104)

1. Scope

This procedure covers radiographic examination of cross-country pipeline girth welds in carbon-steel transmission and gathering pipelines constructed to API 1104 (latest edition, currently 22nd). It applies to wall thicknesses from 3.2 mm (0.125 in) to 25.4 mm (1.00 in), outside diameters from 60 mm (2-3/8 in) NPS to 1219 mm (48 in) NPS, and is intended for new construction and tie-in welds. In-service pipeline welds under repair conditions require additional thermal-load review per API 2201; that case is out of scope.

2. References

• API Standard 1104 — Welding of Pipelines and Related Facilities, current edition
• ASTM E94 / E94M — Standard Guide for Radiographic Examination
• ASTM E747 — Wire-Type IQI
• ASTM E1742 / E1742M — Radiographic Examination Using Industrial Radiographic Film
• 49 CFR §192 (gas) / §195 (liquid) — PHMSA NDT requirements
• ASNT SNT-TC-1A or CP-189
• Customer Written Practice

3. Personnel Qualification

Radiographic examination shall be performed by personnel certified to ASNT NDT Level II in RT, qualified per a Written Practice meeting SNT-TC-1A or CP-189. Film interpretation and Level III review of marginal indications shall be by a Level III in RT.

Radiation-safety personnel shall hold a current operator certification per the applicable jurisdiction (US: NRC Reciprocity / Agreement-State; Canada: CNSC).

4. Equipment

• Source: Ir-192 for wall thicknesses 12.5 mm to 65 mm steel; Se-75 for thin-wall (≤ 12.5 mm) where focal-spot geometry is favourable; X-ray for thin-wall or where source-side IQI sensitivity demands it. Source-activity range typically 1.85 TBq (50 Ci) to 3.7 TBq (100 Ci) Ir-192 depending on wall thickness and SFD.
• Source projector with calibrated source-guide tubes and collimator (collimation mandatory in populated work areas).
• Industrial radiographic film: Class I (D7 / Industrex M / Agfa D4) for high-sensitivity work; Class II for routine work where sensitivity allows.
• Lead intensifying screens, 0.13 mm front / 0.25 mm back (0.005 in / 0.010 in).
• Densitometer calibrated to NIST-traceable step wedge — last calibration ≤ 90 days.
• IQI: ASTM E747 wire-type, material-matched to the production weld. Essential wire selected per API 1104 Table 11.1.
• Calibrated step-wedge density strip.
• Radiation survey meter (Geiger-Müller or scintillator) — calibration current within 12 months.
• Audible and visible alarming dosimeters per 10 CFR 34.

5. Surface Preparation and Geometry

Weld and adjacent base metal (minimum 25 mm each side of the weld toe) shall be free of mud, ice, weld spatter, paint that would mask indications, and slag. The weld profile shall be acceptable for visual interpretation per API 1104 Section 9.3.

Source-to-film distance (SFD) shall meet the geometric-unsharpness limits of API 1104 Section 11.1.6:

Ug = (F × t) / D
where Ug ≤ 0.5 mm (0.020 in) for t ≤ 50 mm

6. Technique

6.1 Single Wall — Single Image (SWSI)

For external pipe surfaces ≥ NPS 4 where the source can be placed inside the pipe: panoramic exposure if pipe ID permits source-and-projector entry, or contact / superimposed offset shots from external positions.

6.2 Double Wall — Single Image (DWSI)

For NPS 2-7/8 through NPS 3-1/2 where panoramic is not feasible: minimum 3 exposures at 120° spacing; minimum 4 exposures at 90° spacing for NPS ≥ 4 where source cannot enter the pipe.

6.3 Double Wall — Double Image (DWDI / Elliptical)

For pipe NPS ≤ 2-7/8 inclusive: minimum 2 exposures 90° apart with the source offset to produce an elliptical projection of the weld. Maximum elliptical separation: 1 weld width.

6.4 IQI Placement

Source-side preferred; film-side acceptable where source-side is not practical, subject to API 1104 Section 11.1.4. Wire IQIs placed across the weld with wires perpendicular to the weld axis.

7. Exposure and Processing

Exposure time selected from a calibrated exposure chart for the source activity, SFD, pipe-wall thickness, and material. Verify by processing a step-wedge density strip at the start of each shift.

7.1 Film Density

Film density measured through the weld and base metal shall be within 2.0 to 4.0 per API 1104 Section 11.1.5. Maximum density variation across the area of interest: 30%.

7.2 IQI Sensitivity

Smallest essential wire visible across the weld and adjacent base metal per the controlling table — typically equivalent to 2-2T sensitivity (per ASTM E747).

7.3 Film Processing

Manual or automatic processing per the film-manufacturer's specification, controlled by sensitometric step-wedge strips. Reject any film with handling marks, processing artefacts, or static within the area of interest.

8. Interpretation and Acceptance Criteria

Interpretation shall be performed in a film-viewing area meeting ASTM E1742 — variable-intensity viewer adequate for the densities being read, ambient light controlled to eliminate glare on the film.

Acceptance criteria per API 1104 Section 9.3 — discontinuity types:

• Inadequate penetration without high-low (IP): rejectable if length exceeds 25 mm in any continuous 300 mm of weld OR total IP length exceeds 8% of weld length.
• Inadequate penetration with high-low (IPD): rejectable if length exceeds 50 mm in any 300 mm OR total exceeds 8%.
• Incomplete fusion (IF): rejectable if length exceeds 25 mm in any 300 mm OR 8% of weld.
• Incomplete fusion due to cold lap (IFD): rejectable if individual length > 50 mm OR total > 8%.
• Internal concavity (IC): acceptable if density does not exceed adjacent base-metal density.
• Burn-through (BT): rejectable if max dimension > 6 mm AND > 0.5t, OR sum exceeds 12 mm in 300 mm.
• Slag inclusions (SI / ESI): rejectable per Table 9.1 — isolated slag > 13 mm long OR width > 1.6 mm.
• Porosity: acceptable per Table 9.2 if cluster diameter ≤ 13 mm AND scattered porosity does not exceed Figure 11.
• Cracks: rejectable regardless of size or location.
• Undercut: rejectable if exceeds 1 mm (0.04 in) deep OR limits of Table 9.3.

9. Reporting

Each radiograph shall be permanently identified with: contract number, weld number, station number, date, technician number, side designation (film side / source side), and shot number for multi-shot welds. The radiographer's report shall record: equipment used, source identity and activity, SFD, exposure time, film type, IQI used and wire visibility, film density, and a sketch with defect locations along the weld axis. Records retained per 49 CFR §192.243 / §195.234 (typically pipeline-life).

10. Safety

Compliance with 10 CFR Part 34 (US), Atomic Energy Regulatory Body equivalents (other jurisdictions). Restricted-area boundary established to 2.0 mSv/hr (200 mR/hr) survey limit; controlled-area boundary at 0.05 mSv/hr (5 mR/hr). Personnel dosimetry: TLD or OSL badge plus direct-reading dosimeter with audible alarm. Source-retraction verification on every shot via survey-meter reading at the projector.

This procedure is a published reference. Production use requires customer and AI (Authorized Inspector or equivalent) approval against the current API 1104 edition. Generate a custom procedure for your wall thickness, source, and operator at the free AI Procedure Generator.