Research on experiment and Engineering Application of 9%Ni LNG Steel Storage Tank butt joint using digital radiography testing technique

9%Ni steel process good mechanical properties, welding ability and low-temperature toughness, and has been widely used in LNG low-temperature storage tanks. Due to the existence of residual weld height in LNG storage tank and the different ray absorption of weld and base material,which brings great difficulties to radiography detection. The digital radiography technique and conventional film radiography technique is adopted in this paper which carried out in exposure chamber. The test results show that the imaging quality of digital radiography technique is better than that of film radiography technique. This paper proposes the digital radiography technique to detect the butt welds of 9% Ni steel, replacing the traditional film radiography technique. A set of automated inspection equipment for digital radiography of large LNG storage tanks has been developed, the inspection problem of butt welds of 9% Ni steel in large LNG storage tanks is successfully solved. Finally, the digital radiography technique is applied in the LNG installation engineering project.