Radiographic testing (RT) is a non-destructive testing (NDT) method which uses either x-rays or gamma rays to examine the internal structure of manufactured components in order to identify any sub-surface flaws or defects.
In this testing method the sample is placed between the X-ray source and the x-ray film (detector). The ease of interpretation of the film will be dependent on many factors such as material density and thickness which will reduce the penetrating radiation through the interaction process which involves scattering as well as absorption. The different absorptions on the films are then evaluated and recorded as a pass or fail according to acceptance criteria defined by international specifications such as BS EN ISO / ASME / API etc… the two different types of radiation sources for industrial use are X-Ray and Gamma-ray. These radiation sources use high energy levels which result in radiation that is incredibly dangerous of once finds themselves exposed to it. It is of paramount importance that Local safety rules and regulations are adhered to when using this testing method.
Metallurgical Testing Labs is of the opinion that X-Ray machines (which lie dormant when not in use) are less hazardous than the radioactive isotopes (Gamma-rays) which require special storage and transport facilities when in use as they are never defined as dormant (meaning that even when not in use, the radioactive isotopes can prove fatal). As such a decision was made to make use of X-ray machines over the Gamma-ray or radioactive isotope method.
The method of RT used by Metallurgical Testing Labs is suitable for testing weld joints that can be accessed from both sides (including double walled single image techniques used on pipe. Although this is a relatively slow and expensive method, it is a very dependable way to detect porosity, inclusions, cracks and voids which would have a negative effect on the end product. Because of this it is a method that is considered to be an important part of proving or validating a “fit for use” concept.
It is noted that Metallurgical Testing Labs was the first lab in South Africa to achieve an ISO 17025:2017 (SANAS Accreditation) for this non-destructive testing method and as such are considered to be at the forefront of quality of testing when it comes to this method. Standards which we are accredited against include:
- ASME V, ASME VIII, ASME IX
- API 1104, API 650
- AWS D1.1, AWS D1.6
- BS EN ISO 10675-1, 17636-1, 17635, PD5500