Abstract: Nickel-based alloys are commonly used as welding materials for 9%Ni steel LNG storage tanks. Due to the particularity of the materials, radiographic inspection methods are often adopted for non-destructive detection of welded joints. The base material and weld metal have different radiation absorption properties, thus single-film transillumination cannot meet the blackness requirements of the base material and the weld metal at the same time. This paper presented comparative tests that were conducted respectively with single-film, double-film and digital radiography technology in radiographic inspection methods. It also analyzed the test results and developed the inspection process that can meet the testing requirements of nickel-based alloy base metal and weld metal.

Key words: LNG storage tank, 9%Ni steel, nickel-based alloys, dual-film, imaging detection