A finite element model for crack arrestor design in gas pipelines
Steel rings are frequently used as crack arrestor devices in steel gas transmission 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 result, crack arrest can take place. This essentially is a second line of defence against catastrophic failure in the event that crack initiation cannot always 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. Here, a curved beam element has been implemented into PFRAC to simulate the behaviour of the arrestor. The contact conditions between the pipe wall and the arrestor, along with the various computational procedures, are described here. Several numerical results for a cracked pipe with arrestors are presented along with comparisons with pipes that do not have arrestors.