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What is Radiographic Testing (RT)? An NDT Method Overview
Radiographic testing (RT) is a non-destructive testing (NDT) method that uses X-rays or gamma rays to image the internal structure of materials. It is widely used for weld inspection, pressure vessel examination, and pipeline inspection — documenting internal flaws, voids, and integrity anomalies on a permanent image.
How RT Works
Ionizing radiation (X-ray or gamma) passes through the test piece. Density differences in the material — cracks, porosity, slag inclusions — cause the radiation to be absorbed at different levels. That difference is captured as an image on film or a digital detector on the far side of the part.
Image quality is determined by the source type, geometry, detector choice, and technical parameters (voltage, exposure time, distance).
Techniques
Film Radiography
The conventional method. X-ray or gamma is exposed onto radiographic film, which is then chemically processed. Film offers long-term archive value and is well suited to field work; however, darkroom processing and chemical waste management add to operating cost.
Digital Radiography (DR)
A flat-panel detector (FPD) replaces film. The image appears immediately on screen — no chemical processing. Field efficiency is high, but equipment cost is greater than film.
Computed Radiography (CR)
Uses phosphorescent imaging plates that are read by a scanner and converted to digital images. A middle ground between film and full DR.
Gamma Radiography
Radioactive isotopes — Ir-192, Se-75, Co-60 — replace the X-ray tube. No electricity required; suited for remote locations, confined spaces, or pipe interiors. The source is transported and stored under controlled conditions.
Applications
- Weld inspection: Internal flaws in pipe, vessel, and structural welds
- Pressure vessels: Manufacturing and in-service inspection under ASME and EN 13445
- Pipelines: Weld quality control in above- and below-ground piping systems
- Petrochemical and refinery: Inspections under API 510, API 570
- Aerospace and defense: Engine components, castings, and internal structure examination
Strengths and Limitations
Strengths:
- Permanent image record — archivable and comparable over time
- Depth information — shows where a flaw sits inside the material
- No access to the far surface required
Limitations:
- Radiation safety — requires an exclusion zone or night-shift planning
- Poor detection of planar flaws parallel to the radiation beam (laminar cracks) — UT is preferred in those cases
- Higher setup and equipment cost than some other NDT methods
Relevant Standards
| Standard | Scope |
|---|---|
| EN ISO 17636 | Radiographic examination of welds (European) |
| ASME Sec. V Article 2 | Radiographic testing technical requirements |
| API 510 | Pressure vessel inspection program |
| API 570 | Piping inspection program |
| EN ISO 9712 | RT personnel certification (Level 1/2/3) |
Personnel Qualification
RT requires personnel certified under EN ISO 9712 or ASNT SNT-TC-1A. In Turkey, technicians performing RT must also hold a radiation worker license from TAEK (Turkish Atomic Energy Authority). A certificate's scope matters: an RT Level II — w certificate covers weld inspection only.
RT and Document Management
RT is one of the most document-intensive NDT methods:
- Technical procedure (analogous to a welding WPS)
- Individual report per exposure
- Film/digital image archive (typically 5–10 years)
- Dosimeter and radiation worker records
- Source inventory and activity logs
This documentation load calls for a centralized management system, especially for high-volume NDT companies.
ceres-ndt manages your RT workflow end-to-end — from work orders and report generation to image archives and TAEK record keeping — on a single platform. Get in touch to book a demo.
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