The radiographic method (RT) makes use of a ionizing radiation beam directed towards the piece to be examined in order to highlight any superficial and internal imperfections. Part of the radiation is absorbed through the piece depending of the material chemical-physical characteristics. When the beam finds a discontinuity, the absorption is different and creates a contrast with the surrounding material on a suitable means of detection.
The most common type of radiation sources are:
- Radioisotopes, made of artificial radioactive substances in order to have a continuous emission of γ (gamma) rays, with constant intensity and decreasing energy over time;
- The X-ray tubes, electrical machines that follow the operating principles of the Coolidge tube (vacuum cathode ray tube) and emit X-rays of adjustable energy and intensity.
- Technique applicable to a wide variety of materials;
- It allows the inspection of even assembled components;
- Reduced surface preparation;
- Ability to detect thickness variations, corrosions, porosities, cracks, material density variations;
- It provides a permanent report (radiographic film).
- The method is burdensome about the security management plan;
- The operator training is complex;
- The test piece must be accessible from both sides;
- The discontinuity orientation is critical;
- Except specific techniques, it is not possible to determine the depth of discontinuities;
- Costs are relevant.
The radiographic testing is applied in almost all fields in which Metalprove S.r.l. works, with the authorization by Ministerial Decree for the road transportation of radioactive substances throughout the national territory and with Prefectural Decree for the detention and use of radioactive sources.
The company has radioisotopes of iridium (Ir-192) and selenium (Se-75) and X-ray tubes of various powers, which are used in many applications according to European standards (EN ISO 5579, EN ISO 17636-1 , EN ISO 10675, EN ISO 4993, EN 12681, etc.), American standards (ASME Sec. V, ASME Sec. VIII, ASTM E94, ASTM E155, ASTM E186, ASTM E446, etc.) or customer specifications (SAL SNAM , etc.).