L51436 Brittle Fracture Arrest in Gas Pipelines

The phenomenon of brittle fracture arrest has been studied by Battelle Columbus Laboratories for the Pipeline Research Council International, Inc. and for the British Gas Corporation (BGC). Pertinent studies have been made independently by BGC for both steel and plastic (PVC) pipes. These studies have revealed that it is possible to obtain arrest of brittle or cleavage fractures propagating in natural gas pipelines under certain conditions..

The specific purpose of this report is to combine the previous work on brittle fracture initiation, propagation, and arrest into a consistent hypothesis, to show how this hypothesis can be used in design, and to show how current API specifications can be used to accomplish these designs or, alternatively, what additional supplementary requirements need to be added to API specifications. Current API 5LX Line Pipe Specifications have Supplementary Requirements SR5 and SR6, which relate to Charpy V-notch (CVN) Impact Testing and Drop Weight Tear Testing (DWTT), respectively, for 20-inch-diameter or larger pipe. Most of the experimental work, also, has been on pipes in this size category. Consequently, the analysis here will be pertinent mainly to the larger pipe sizes. This report describes the conditions that are necessary for control of propagating brittle fractures and also suggests other considerations with regard to fracture initiation.