Knowledge

Radiographic Testing

Radiographic Testing (RT), or industrial radiography, is a nondestructive testing (NDT) method of inspecting materials for hidden flaws by using the ability of short wavelengthelectromagnetic radiation (high energy photons) to penetrate various materials.

Either an X-ray machine or a radioactive source, like Ir-192, Co-60, or in rarer cases Cs-137 are used in a X-ray computed tomography machine as a source of photons. Neutron radiographic testing (NR) is a variant of radiographic testing which uses neutrons instead of photons to penetrate materials. This can see very different things from X-rays, because neutrons can pass with ease through lead and steel but are stopped by plastics, water and oils. Most industries are moving from film based radiography to a digital sensor based radiography much the same way that traditional photography has made this move.

Since the amount of radiation emerging from the opposite side of the material can be detected and measured, variations in this amount (or intensity) of radiation are used to determine thickness or composition of material. Penetrating radiations are those restricted to that part of the electromagnetic spectrum of wavelength less than about 10 nanometres.


Other Techniques:

In industrial radiography there are several imaging methods available, techniques to display the final image, i.e. Film Radiography, Real Time Radiography (RTR), Computed Tomography (CT), Digital Radiography (DR), and Computed Radiography (CR).

There are two different radioactive sources available for industrial use; X-ray and Gamma-ray. These radiation sources use higher energy level, i.e. shorter wavelength, versions of the electromagnetic waves. Because of the radioactivity involved in radiography testing, it is of paramount importance to ensure that the Local Rules is strictly adhered during operation.

Computed Tomography (CT) is one of the lab based advanced NDT methods that TWI offers to industry. CT is a radiographic based technique that provides both cross-sectional and 3D volume images of the object under inspection. These images allow the internal structure of the test object to be inspected without the inherent superimposition associated with 2D radiography. This feature allows detailed analysis of the internal structure of a wide range of components.


Benefits:

  • Can inspect assembled components
  • Minimum surface preparation required
  • Detects both surface and subsurface defects
  • Provides a permanent record of the inspection
  • Verify internal flaws on complex structures
  • Isolate and inspect internal components
  • Automatically detect and measure internal flaws
  • Measure dimensions and angles within the sample without sectioning
  • Sensitive to changes in thickness, corrosion, flaws and material density changes

Applications:

Radiographic Testing is widely used in the;

  • Aerospace industries
  • Military defence
  • Offshore industries
  • Marine industries
  • Power-gen industries
  • Petrochem industries
  • Waste Management
  • Automotive industries
  • Manufacturing industries
  • Transport industries