FRACTURE BEHAVIOR IN PIPE PRESSURED WITH LNG
摘要
This paper presents a summary of the fracture behavior of pipe pressured with liquefied natural gas as observed in full-scale experiments conducted for the Pipeline Research Committee of the American Gas Association. The objective of the experiments was to investigate the conditions surrounding the initiation, unstable propagation, and arrest of fractures when LNG is used as the pressuring fluid. Altogether, 14 experiments are reported--9 of these employed LNG as the pressuring medium, including two aluminum alloy experiments conducted on another research program. Materials studied include 9 percent nickel steel, 3-1/2 percent nickel steel, 304 stainless steel, 6061-T6, 5083-0, and 7039-T651 aluminum. Of special importance among the data obtained in this research investigation is the observation that a stress level exists below which unstable fracture propagation cannot be supported in liquid filled LNG pipeline under expected operating conditions (the pipeline would decompress to the saturation pressure at the onset of fracture) and pipe wall thickness can be accordingly chosen to prevent the possibility of long, unstable fracture propagation should one unavoidably be initiated. These experiments suggest that it may be possible to design ship-to-shore LNG transfer lines, in-plant LNG piping, or other cryogenic pipelines with a greater assurance of safety.