Radiographic testing (RT) passes X-rays or gamma rays through a part and records the image. Thicker or denser areas absorb more radiation, while voids, porosity, inclusions and cracks absorb less and show on the image, giving a permanent record of the inside of a weld, casting or assembly.
- Finds
- Internal voids, porosity, inclusions, cracks, assembly and joint defects
- Typical use
- Weld and casting acceptance, high-volume production, electronics, field source radiography
What industrial radiography finds
- Porosity, voids and shrinkage
- Slag and other inclusions
- Incomplete penetration and lack of fusion
- Cracks, where they lie roughly in line with the beam
- Assembly and joint defects, and missing or misplaced parts
- In electronics: loose connections, frayed wire and bad solder joints
X-ray or gamma?
We use both X-radiation and gamma sources. X-ray tubes can be switched off and give fine control of energy, which suits thin material, electronics and production work. Gamma sources need no power and fit into tight spaces, which suits field welds, pipe and thicker sections. The source is chosen by the material, its thickness, the image quality the code requires and the site.
Radiography or ultrasonic testing?
Radiography gives a permanent image and shows volumetric flaws such as porosity and slag well. Ultrasonic testing is better at planar flaws such as cracks and lack of fusion, gives depth, and needs no exclusion area. Many codes accept either for weld examination; some specify one.
Where it’s used
- Weld and casting acceptance in manufacturing
- Field radiography of pipe, piping and structural welds in oil and gas, chemical and petrochemical plants
- Defense and aerospace components
- Electronics, when taking a device apart would destroy it
- Fine art conservation, where the internal structure of a work has to be known before it is restored
- Accident investigation
Codes and standards
- ASME Boiler and Pressure Vessel Code, Section V, Article 2, with acceptance in Section VIII or ASME B31.3
- AWS D1.1, for structural steel welds
- API 1104, for pipeline welding
- ASTM E1742/E1742M, the standard practice for radiographic examination, widely used in aerospace and defense work
- ASTM E94/E94M, the guide to radiographic examination
- Customer and prime-contractor specifications
Industrial radiography is also governed by radiation safety regulations: the U.S. Nuclear Regulatory Commission’s rules in 10 CFR Part 34, or the equivalent state rules, for sealed gamma sources, and state rules for X-ray equipment.
Who does the work
Every Midgard technician who performs radiographic testing holds current certification in that method, issued under a written practice. For most industrial work the written practice follows ASNT’s SNT-TC-1A; for aerospace and defense work it follows NAS410. A Responsible Level III oversees the program: approving procedures and technique sheets, examining and certifying technicians, and answering the technical questions that come up on the job.
If your contract calls for a different scheme, such as ANSI/ASNT CP-189 or NAVSEA requirements, tell us when you ask for a quote.
Training in radiographic testing
Midgard also trains in radiographic testing, along with all the other major methods. Instruction is given at Level I, II and III by certified Level III instructors, to SNT-TC-1A, CP-189, NAS410, NAVSEA or whichever code you certify to, with general, specific and practical examinations at your facility or ours. It suits new hires working toward first certification as well as technicians due for re-examination. See training and certification, or ask about a class.
Common questions
Is radiographic testing dangerous?
Radiation is hazardous, which is why industrial radiography is tightly regulated. It is done under a radiation safety program, with a controlled boundary around the exposure, survey meters and personal dosimetry for the radiographers, and no one else inside the boundary while the source is exposed. Plan for the area to be cleared during exposures; many sites schedule radiography on off-shifts to keep other work moving.
What is the difference between radiography and ultrasonic testing?
Radiography produces an image of the whole volume and is strong on porosity, slag and other volumetric flaws. Ultrasonic testing is strong on cracks and lack of fusion, gives flaw depth, and needs no exclusion area. The right choice depends on the flaw you are looking for and the code you answer to.
Can radiography inspect electronics without taking them apart?
Yes. Radiographic imaging shows loose connections, frayed wire, bad solder joints and other internal faults when disassembly would damage the device.
Who interprets the radiographs?
Radiographs are interpreted and evaluated against the governing code by technicians certified in radiography, with a Level III available for anything in question.
Tell us the material and thickness, the welds or parts, whether the work is in the field or in a shop, and the code you work to. Call 1-844-MIDGARD, email contact@midgardscientific.com, or use the contact page.