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10:21 PM , Friday 28th July 2017

RT – Radiography

Radiographic testing reveals internal volumetric discontinuities. In specific cases, it is possible to detect also 2D defects, e.g. cracks. The most frequent use of RT is for examination of welds, castings, products of electro technical industry, civil engineering, etc. Due to tradition and demonstrativeness, an RT becomes one of the most important NDT method in the industrial applications. Its domains are:

  1. productivity
  2. accessibility
  3. internal volume inspection
  4. Wide variety of material properties
An electron beam is formed in the RT device. The beam is directed to the tested area. The x-rays are focused, or at least shielded as they exit the machine. Full-direction of gamma source radiation may be beneficial in some panorama tic snaps. As the photon energy is attenuated by the path through tested object material, it forms an image on the screen. A change or a local anomaly is evaluated and internal defects are detected.

X - Ray Gamma-Ray
High penetration. High penetration.
High safety. Isotope sources.
Electric power. Cannot stop the radiation.
Easy preparing to examination. Decreases with time.

Because the RT devices are generally heavier than common equipment for the other NDT methods, manipulation with a tested object may be beneficial. The set-up during image shot is fixed, or automatic manipulators shall be used because of personnel safety measures. The SSFAT laboratory is fully equipped for performance of industrial radioscopy. The core devices are: • directional X-Ray tube • linear accelerator For field application, a gamma sources may be used.

RT lab


SSFAT facility is provided with a large RT laboratory. The area of the bunker is about 227 m2. A safety measures are applied, such as wall of 2 m thickness, alert warning, interlocks or a live camera for operation survey. Full one wall is dedicated for tested object delivery provided by slide door.
image

A vacuum tube is operated at several thousand volts, however the device structure is pretty compact emphasized application flexibility. Because of limited energy, a fan cooling is enough to operate a device in the laboratory. Even an electric power supply is necessary, this device can be considered as portable.
image

The linear accelerator utilises physics of microwave to accelerate electrons in a so called a "wave guide". These high-energy electrons collide with a heavy metal target to produce x-rays. Because of high energy, a cooling system with forced circulation and external chillers is applied. The device head is mounted to the portal system. The height and angle of beaming may be set individually. In the tested area, a table is positioned allows rotating of the tested object. The table sustains 2400 kg. Linear Accelerator operated by SSFAT has been manufactured by Varian in 1990. After regular RT laboratory establishment, this unique device is ready for commercial applications now.
image
image

For industrial applications, we can deal with:

Radiation Source Characteristics Energy Steel Thickness
X-Ray linear accelerator manipulator 6 MeV –,11
MeV
51 –,300 mm
x-ray tube portable 40 keV –,225
keV
6 –,50,mm
Gamma Ir192 D2.7 x L3.45 mm 206 –,612
keV
12 –,63 mm
Se75 D3.25 x L2.5 mm 66 –,401
keV
3 –,29 mm


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