Prediction of the service life of pipeline elements subjected to the action of hydrogen-containing media

We study the process of crack propagation in a preliminarily hydrogenated pipe placed in a hydrogen-containing medium. The crack growth rate is mainly controlled by the mass transport of hydrogen into the prefracture zone. We obtain an approximate solution of the problem of diffusion of hydrogen in the vicinity of the crack tip and establish the dependence of the crack growth rate on the crack tip opening displacement. This dependence is used for the determination of the residual service life of damaged elements of the pipe. The pipe is made of 4147 steel and the defect is modeled by a semielliptic longitudinal crack on the internal surface of the pipe. We show that the initial concentration of hydrogen may significantly accelerate the fracture process.