This project addresses pragmatic application of the new DOT/PHMSA MegaRule RIN 1 - 192.712 for recommended toughness values for determining if an axial flaw needs repair or can instead be observed for any future growth. The MegaRule toughness is expressed as the Charpy energy value, which came from Charpy test data at 50F. However, the fracture toughness of a surface-cracked pipe is quite different than Charpy impact toughness values, especially if the Charpy data is in the transition region. In this project, it was shown from past axial surface-cracked pipe tests that the lowest temperature for...
This project addresses pragmatic application of the new DOT/PHMSA MegaRule RIN 1 - 192.712 for recommended toughness values for determining if an axial flaw needs repair or can instead be observed for any future growth. The MegaRule toughness is expressed as the Charpy energy value, which came from Charpy test data at 50F. However, the fracture toughness of a surface-cracked pipe is quite different than Charpy impact toughness values, especially if the Charpy data is in the transition region. In this project, it was shown from past axial surface-cracked pipe tests that the lowest temperature for ductile initiation is significantly lower than the Charpy test transition temperature. In cases with axial surface cracks in vintage base metal pipe tests, the surface-crack ductile transition temperature was >200F lower than the Charpy transition temperature. The procedures were extended to welds, and databases from member companies were examined to establish what Charpy energy values should be used to reflect the tough-ness of a surface crack in the pipe at the operating temperatures, and still be consistent with the MegaRule Charpy information and safety desires.