Non-destructive testing forms an integral part of the oil and gas industry. Therefore, aspirants wanting to get into this industry must have the skills and knowledge related to NDT methods. Here, let’s understand one of the most popular and crucial NDT methods, radiographic testing.
Radiographic testing (RT, X-ray, or Gamma-ray) is a type of non-destructive testing (NDT) that involves penetrating X or gamma radiation to examine objects having imperfections.
To maintain optimal quality in your operation, radiography (X-ray) uses X-rays and gamma-rays to generate a radiograph of a specimen, exposing any changes in thickness, defects (internal and external), and assembly details.
This is an essential topic in the oil and gas courses for mechanical engineers.
Why is Radiographic Testing used?
RT is typically suited for testing welded connections that can be accessed from both sides, and the only exception is double-wall signal imaging methods utilized on certain pipes. Although this is a time-consuming and costly NDT approach, it is a reliable way of detecting porosity, inclusions, fractures, and voids in weld interiors.
X-rays or gamma rays are used in RT. An X-ray tube generates X-rays, whereas a radioactive isotope generates gamma rays.
This segment holds a significant place in oil and gas training courses online.
Principle of Radiographic Testing
A radiography film is placed on the remote side of the object being inspected throughout the procedure. Radiation is then transmitted through the material from one side to the other, where the radiographic film is placed.
The radiation is detected by the radiographic film, which then measures the varying amounts of radiation received throughout the whole surface of the film.
This film is then processed in a dark room. The various degrees of radiation received by the film are imaged by a display of varying degrees of black and white, a process known as film density, which is seen on a specific light-emitting device.
Radiographic testing produces a lasting record in the form of a radiograph, which is a highly sensitive image of the material’s interior structure.
The amount of radiation the film receives via that particular plane of the material is affected by discontinuities in the substance.
Advantages & Disadvantages of Radiographic Testing
Radiography has several advantages, are:-
- Inspection capabilities for a wide range of materials of various densities
- Inspection of completed components
- Surface preparation is minimal.
- Determining the rate of crack growth
- Determination of surface and subsurface flaws
- A permanent record of the inspection
The significant disadvantages of Radiographic inspection:
- Ionizing radiation poses a threat that necessitates the establishment of a safety zone.
- Equipment is quite costly.
- The inspection procedure is rather sluggish.
- Sensitive to the orientation of flaws
- In most cases, determining the depth of signals is impossible.
- Access to the test object from both sides is necessary.
This is just an overview of the Radiographic inspection. If you are keen to know more about the detailed radiographic testing techniques, check our online course for piping engineering.