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PRCI PR-214-9802
- Interim Approach to Determine Crack Arrest Toughness to Avoid Dynamic Ductile Fracture in Gas Transmission Pipelines
- Report / Survey by Pipeline Research Council International, 03/01/2001
- Publisher: PRCI
$98.00$195.00
L51877e
Fleet Technology Limited
Need: Design against long ductile fracture propagation in gas pipelines involves an analysis of the balance between driving force, derived from the gas pressure, and the fracture resistance of the material. Initially, the shelf energy in the Charpy test was successfully used as a measure of fracture propagation resistance. As material strength, pipe diameter and operating pressures increased and required greater fracture propagation resistance, the limitations of the Charpy energy approach became increasingly apparent. This limitation for modern steels is due to the fact that the Charpy test involves significant energy absorption contributions from processes not related to fracture propagation. If an energy-balance approach is to be maintained, and if material resistance is to be measured in a fairly simple laboratory notch bend test (e.g. Charpy or drop-weight tear), the problem reduces to the isolation of the propagation energy absorption per unit of crack advance.
Result: To resolve crack propagation energy, a novel modification was evaluated for both Charpy and DWTT specimens by employing a back-slot including a snug fitting shim to replace the removed material. In most cases, this modification was effective in curtailing the load-displacement trace when the propagating crack interacted with the slot on the backside of the specimen. It is also noted that this approach did not affect the initial portion of the load-displacement history and thus allowed crack propagation energies to be resolved.
Benefit: The report's findings and pipe test data can improve fracture control plans within a gas pipeline company
Fleet Technology Limited
Need: Design against long ductile fracture propagation in gas pipelines involves an analysis of the balance between driving force, derived from the gas pressure, and the fracture resistance of the material. Initially, the shelf energy in the Charpy test was successfully used as a measure of fracture propagation resistance. As material strength, pipe diameter and operating pressures increased and required greater fracture propagation resistance, the limitations of the Charpy energy approach became increasingly apparent. This limitation for modern steels is due to the fact that the Charpy test involves significant energy absorption contributions from processes not related to fracture propagation. If an energy-balance approach is to be maintained, and if material resistance is to be measured in a fairly simple laboratory notch bend test (e.g. Charpy or drop-weight tear), the problem reduces to the isolation of the propagation energy absorption per unit of crack advance.
Result: To resolve crack propagation energy, a novel modification was evaluated for both Charpy and DWTT specimens by employing a back-slot including a snug fitting shim to replace the removed material. In most cases, this modification was effective in curtailing the load-displacement trace when the propagating crack interacted with the slot on the backside of the specimen. It is also noted that this approach did not affect the initial portion of the load-displacement history and thus allowed crack propagation energies to be resolved.
Benefit: The report's findings and pipe test data can improve fracture control plans within a gas pipeline company
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