Analytical investigation of process pipe failure in cryo-line; impact of different crack sizes

Safety is important in cryogenic field dealing with liquid or supercritical state helium. Cryo-lines carrying helium at 4 K temperature level and equipped with thermal compensation devices, like bellows, are prone todevelopment of cracksand its propagation after a number of expansion and contraction. Even after careful design, appropriate material selection and a strict quality control during manufacturing, probability of crack development in the Cryo-line cannot be avoided. An investigative study of failure of process pipe due to the development of crack has been carried out for a long Cryo-line laid in a confined space considering the space between two vacuum barriers is 10 meter.Study shows that minimum temperature of the Outer Vacuum Jacket (OVJ)goes down to 251 K in 540th second andthe minimum temperature of the confined space reaches to 73 K in 37th second. As the crack size reduces, the OVJ pipe temperature approaches to the minimum value in longer time and confined space final temperature increases.