A finite element model for crack arrestor design in gas pipelines

Steel rings are frequently used as crack arrestor devices in steel gas tran smission pipelines to prevent the possibility of long running axial cracks. These arrestors have the effect of reducing the pipe opening as the crack propagates. This decreases the available crack driving force and, as a resu lt, crack arrest can take place. This essentially is a second line of defen ce against catastrophic failure in the event that crack initiation cannot a lways be prevented. This paper describes a novel analysis methodology that has been developed to investigate the suitability of these crack arrestors. This is based on a fluid/structure/fracture interaction package, PFRAC. He re, a curved beam element has been implemented into PFR;IC to simulate the behaviour of the arrestor. The contact conditions between the pipe wall and the arrestor, along with the various computational procedures, are describ ed here. Several numerical results for a cracked pipe with arrestors are pr esented along with comparisons with pipes that do not have arrestors.