RT (Radiographic Testing)
Industrial radiography is used for a variety of applications but is commonly performed using two different sources of radiation, X-Ray and Gamma ray sources. The choice of radiation sources and their strength depends on a variety of factors including size of the component and the material thickness. Within the broad group of X-Ray and Gamma ray sources are a variety of camera choices with varying radiation strengths. Tester Lab Services X-Ray capabilities run the X-Ray from 4 MEV units utilized to radiograph extremely large and thick castings and forgings, to portable X-Ray machine used for field weld applications and thin wall material inspection. Gamma sources vary from very low level fluoroscopic units to perform real time corrosion under insulation surveys, to Iridium (Ir192) and Selenium (Se 75) sources used for a variety of weld inspections, to Cobalt (Co 60) inspections for thick component testing.
There are many advantages to radiography including: inspection of a wide variety of material types with varying density, ability to inspect assembled components, minimum surface preparation required, sensitivity to changes in thickness corrosion, voids, cracks and material density changes, the ability to detect both surface and subsurface defects and the ability to provide a permanent record of the inspection.
The disadvantages of radiography are: safety precautions are required for the safe use of radiation, access to both sides of the specimen are required, orientation of the sample is critical, and determining flaw depth is impossible without additional angled exposures.
Radiographic testing is used extensively on castings and weldments. Radiography is well suited to the testing of semiconductor devices for cracks, broken wires, unsoldered connections, foreign material and misplaced components. Sensitivity of radiography to various types of flaws depends on many factors, including type of material, type of flaw and product form. Both ferrous alloys can be radio graphed, as can non-metallic materials and composites.