Radiographic testing (RT), often called weld X-ray, is a non-destructive testing method in which X-rays or gamma rays pass through the material and form a two-dimensional image on film or a digital detector. Thinner or hollow areas let more radiation through and appear with a different density in the image. Because it produces a permanent record that can be archived as evidence, radiography is a primary inspection method in many industries. FKT NDT provides radiographic testing of welded joints and castings.
Where It Is Used
Radiography has two main fields of application: the inspection of welds and the examination of base material such as castings and forgings.
- Butt welds, particularly in pipe and plate
- Girth welds on pipelines and piping systems
- Pressure vessels, boilers and tanks
- Castings, valve and pump bodies
- Energy, oil and gas, shipyard and steel structure projects
On pipes without internal access, double-wall techniques (double-wall single-image or double-wall double-image) can be used.
What Defects It Detects
- In welds: lack of fusion, incomplete penetration, slag inclusions, porosity and gas pores, cracks, tungsten inclusions
- In castings and base material: shrinkage, gas cavities, inclusions and density variations
Radiography shows volumetric defects such as porosity and slag very clearly. Planar defects such as cracks and lack of fusion only show up well when they lie roughly parallel to the beam. For these, ultrasonic testing is usually more reliable, and the two methods often complement each other.
Standards
Radiographic testing is commonly applied according to:
- EN ISO 17636-1 – Radiographic testing of welds, X- and gamma-ray techniques with film
- EN ISO 17636-2 – Radiographic testing of welds, X- and gamma-ray techniques with digital detectors
- EN ISO 10675-1 – Acceptance levels for radiographic testing of welds (steel, nickel, titanium and their alloys)
- ISO 19232-1 – Image quality indicators (wire type)
- ASME Section V, Article 2 – Radiographic examination
- ISO 9712 – Personnel certification
How the Inspection Works
- Planning and radiation safety: the exposure technique and conditions are defined. The work area is barriered and marked in line with radiation safety rules, and unauthorised access is prevented during exposure.
- Preparation: weld identification and location markers are placed, and image quality indicators (IQIs) are positioned.
- Exposure: the source and the film or detector are placed on either side of the weld in the geometry defined by the standard, and the exposure is made.
- Processing: film is developed, or the digital image is processed.
- Evaluation and reporting: image quality (density, IQI sensitivity) is checked and indications are assessed against the acceptance criteria. The report records the technique, weld details, standard, findings and result (accept/reject), and the films or digital images are archived.
Advantages of Radiography
- Produces a permanent record that can be reviewed again and compared with references
- No equipment set-up on reference blocks as in ultrasonic testing; image quality is verified with IQIs
- Excellent for detecting internal discontinuities, especially volumetric ones
- Results depend less on surface condition and part geometry than ultrasonic testing does
Disadvantages of Radiography
- X- and gamma radiation is a serious health hazard; strict radiation safety measures are required and the area must be cleared during exposure
- Defect depth cannot be determined without special techniques
- The orientation of linear and planar discontinuities relative to the beam determines whether they are detected
- More expensive than other methods
- Penetration is limited in thick sections, and access to both sides of the part is needed
FAQ
Is weld X-ray the same as radiographic testing?
Yes. What is called weld X-ray on site is radiographic testing of welds with X- or gamma rays.
Does other work have to stop during radiography?
Nobody may enter the controlled area during exposure, so radiography is often scheduled between shifts or when the area can be cleared.
Film or digital radiography?
Both are covered by standards: EN ISO 17636-1 for film and EN ISO 17636-2 for digital detectors. The choice follows the project specification and client requirements.
Radiography or ultrasonic testing?
Radiography is preferred for volumetric defects and when a permanent image is needed; ultrasonic testing for planar defects such as cracks and for thick sections. Often the product standard or specification decides.
For a radiographic testing quote, please contact us through our contact page.