NR198308 Design and Optimization of Mechanical Crack Arrestors for Pipelines

For natural gas or liquid CO2 pipelines, unstable ductile fracture can occur when the pressure at the propagating crack tip is sufficient to cause the crack driving force to exceed the fracture resistance of the line pipe material. In the past, when these conditions existed, unstable ductile fractures have been known to propagate for significant distances. The objective was to investigate the ability of various designs to arrest an axially propagating ductile fracture and to optimize the design of crack arrestors. The experimental evaluations involved a scale model approach to evaluate the different arrestor designs. By testing two different sizes of pipe and a variety of test conditions, it was possible to evaluate the ability of scale model experimental data to predict full-scale behavior. By normalizing the arrestor length and radial clearance to the pipe diameter, the arrest/propagate boundary lines for various arrestor designs were equally effective in describing the behavior of crack arrestors thus adding credence to the contention that the model crack arrestor experiments can predict full-scale behavior.