Studies On The Methods Of Radiographic Inspection For The Valve Flaw

With vigorous development of electric power, petrochemical, metallurgy, ship engineering, nuclear energy and aviation, valve plays the more and more important role of component in special equipment. In the worldwide the developed country have paid more considerable attention to the safe quality of valve manufactured, rather than china, for several reasons, began to licence the manufacture qualification of bearing valve, supervise and verify its manufacture quality since Feb. in 2003. There often had valve leak and fracture accidents previously, because of not effective controlment of valve quality, causing great damage to people's life and wealth. Through studying the field of valve test the using of the technique radiographic inspection, the paper give a well impetus action to control the valve manufacture quality and improve the enterprise economy efficiency.Though china have promulgated some relevant regulations and established some corresponding standard for the valve manufacture quality, presenting the application problem of radiographic inspection in the field, there also cause undetected flaws and economic waste phenomenon, due to the variety of valve dimension and thickness, the short usage history of radiographic inspection in the field, and what is more, the technology verifying the valve with radiographic inspection technique is mature insufficiently, and have some random. The paper discusses the character of ray, the different effects and attenuation laws when penetrating through an object, and photographic principle of ray in detailed, and analyses the factors affecting the negative contrast, indistinctness and graininess thoroughly. Based on the three great factors affecting the detection sensitivity, the article studys the choice of technology such as radiographic source, focus, transillumination, negative, backscattering and so on, and defines the choice principle for transillumination means. Deducing the minimum times for various shooting methods, based on the general formula of the small flaw, combining the transmitted thickness ratio defined in the national standards.The paper study the character of ray equipment, design hardware system of various transillumination methods, verify the defective valve according to traditional transillumination methods and other methods studied in the paper respectively, to compare the defective negatives and prove to get more better negatives at contrast, indistinctness and graininess using the testing methods discussed in the article, offerring radiographic inspection technique both with good economy benefit and examination quality for valve manufacture enterprises.