What is Industrial radiography

Radiography is the use of certain types of electromagnetic radiation-usually ionizing-to view objects. Prior to 1912, X-rays were used little outside the realms of medicine and dentistry, though some X-ray pictures of metals were produced. The reason that X-rays were not used in industrial application beforethis date was because the X-ray tubes (the source of the X-rays) broke down under the voltagesrequiredto produce rays of satisfactory penetrating power for industrial purposes.

However, that changed in 1913 when the high vacuum X-ray tubes designed by Coolidge became available. The high vacuum tubes were an intense and reliable X-ray source, operating at energies up to 100,000 volts. In 1922, industrial radiography took another step forward with the advent of the 200,000-volt X-ray tube that allowed radiographs of thick steel parts to be produced in a reasonable amount of time. In 1931, General Electric Company developed 1,000,000 volt X-ray generators, providing an effective tool for industrial radiography. That same year, the American Society of Mechanical Engineers (ASME) permitted X-ray approval of fusion welded pressure vessels that further opened the door to industrial acceptance and use.

Today, industrial radiography uses X-rays or gamma rays to produce an image of an object on film. The image is usually natural size. X-ray and gamma rays are very short wavelength electromagnetic radiation, which can pass through solid material, being partly absorbed during transmission. Thus, if an X-ray source is placed on one side of a specimen and a photographic film on the other side, an image is obtained on the film of the thickness variations in the specimen, whether these are surface or internal. Radiography is a well-established technique, which gives a permanent record and is widely used to detect internal flaws in weldments and castings and to check for mis-constructions in assemblies.

Radium became the initial industrial gamma ray source. The material allowed castings up to 10 to 12 inches thick to be radiographed. During World War II, industrial radiography grew tremendously as part of the Navy's shipbuilding program. In 1946, man-made gamma ray sources such as cobalt and iridium became available.These new sources were far stronger than radium and were much less expensive. The manmade sources rapidlyreplaced radium, and use of gamma rays grew quickly in industrial radiography.