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The development of radiographic equipment for industrial use from the 200-kv. machine of 10 yr. ago, similar in many respects to the medical equipment of that day, to the present million-volt industrial X-ray machine has kept pace with the increasing demands for radiographic examination of heavy wall fusion welded pressure vessels with plate thicknesses up to 52 in. Application of higher-voltage X-ray equipment to industrial radiography introduced the problem of blocking excessive secondary radiation from the film. This requirement was met by the development of the Bucky grid and similar devices. Although a considerable increase in exposure time resulted from the use of these grids, X-ray films of good detail were obtained with 300-kv. and 400-kv. equipment.
The advent of million-volt X-ray equipment with the emission of extremely short wave length X-rays necessitated a radical change in our X-ray technique. A special fine-grained no-screen film (direct-exposure film) was developed for this purpose by the Eastman Kodak Co., representing a significant advancement in the solution of radiographic problems. The use of lead foil screens in conjunction with this film obviates the necessity for Bucky grids and calcium-tungstate screens and permits the standardization of X-ray technique, thus assuring consistently satisfactory results.
Carpenter, O. R.
Engineer, The Babcock & Wilcox Co., Barberton, Ohio